Table of contents

We describe a construction of fuzzy spaces which approximate projective toric varieties. The construction uses the canonical embedding of such varieties into a complex projective space: The algebra of fuzzy functions on a toric variety is obtained by a restriction of the fuzzy algebra of functions on the complex projective space appearing in the embedding. We give several explicit examples for this construction; in particular, we present fuzzy weighted projective spaces as well as fuzzy Hirzebruch and del Pezzo surfaces. As our construction is actually suited for arbitrary subvarieties of complex projective spaces, one can easily obtain large classes of fuzzy Calabi-Yau manifolds and we comment on fuzzy K3 surfaces and fuzzy quintic three-folds. Besides enlarging the number of available fuzzy spaces significantly, we show that the fuzzification of a projective toric variety amounts to a quantization of its toric base.

We summarize the physics case of a high-luminosity e⁺e⁻ flavour factory collecting an integrated luminosity of 50–75 ab⁻¹. Many New Physics sensitive measurements involving B and D mesons and τ leptons, unique to a Super Flavour Factory, can be performed with excellent sensitivity to new particles with masses up to ∼ 100 (or even ∼ 1000) TeV. Flavour- and CP-violating couplings of new particles that may be discovered at the LHC can be measured in most scenarios, even in unfavourable cases assuming minimal flavour violation. Together with the LHC, a Super Flavour Factory, following either the SuperKEKB or the SuperB proposal, could be soon starting the project of reconstructing the New Physics Lagrangian.

By explicit calculation, we show that the expansion of the disk level S-matrix element of one RR field, two open string tachyons and one gauge field that has been recently found corresponds to the derivative expansion of the Wess-Zumino action of D-brane-anti-D-brane systems.

Following on from recent studies of string theory on a one-parameter family of integrable deformations of AdS₅ × S⁵ proposed by Lunin and Maldacena, we carry out a systematic analysis of the high temperature properties of type IIB strings on the associated pp-wave geometries. In particular, through the computation of the thermal partition function and free energy we find that not only does the theory exhibit a Hagedorn transition in both the (J, 0, 0) and (J, J, J) class of pp-waves, but that the Hagedorn temperature is insensitive to the deformation suggesting an interesting universality in the high temperature behaviour of the pp-wave string theory. We comment also on the implications of this universality on the confinement/deconfinement transition in the dual = 1 Leigh-Strassler deformation of = 4 Yang-Mills theory.

In hep-th/0311177, the Large N renormalization group (RG) flows of a modified matrix quantum mechanics on a circle, capable of capturing effects of nonsingets, were shown to have fixed points with negative specific heat. The corresponding rescaling equation of the compactified matter field with respect to the RG scale, identified with the Liouville direction, is used to extract the two dimensional Euclidean black hole metric at the new type of fixed points. Interpreting the large N RG flows as flow velocities in holographic RG in two dimensions, the flow equation of the matter field around the black hole fixed point is shown to be of the same form as the radial evolution equation of the appropriate bulk scalar coupled to 2D black hole.

We show that various holomorphic quantities in supersymmetric gauge theories can be conveniently computed by configurations of D4-branes and D6-branes. These D-branes intersect along a Riemann surface that is described by a holomorphic curve in a complex surface. The resulting I-brane carries two-dimensional chiral fermions on its world-volume. This system can be mapped directly to the topological string on a large class of non-compact Calabi-Yau manifolds. Inclusion of the string coupling constant corresponds to turning on a constant B-field on the complex surface, which makes this space non-commutative. Including all string loop corrections the free fermion theory is elegantly formulated in terms of holonomic D-modules that replace the classical holomorphic curve in the quantum case.

Recently a three-dimensional field theory was derived that is consistent with all the symmetries expected of the worldvolume action for multiple M2-branes. In this note we examine several physical predictions of this model and show that they are in agreement with expected M2-brane dynamics. In particular, we discuss the quantization of the Chern-Simons coefficient, the vacuum moduli space, a massive deformation leading to fuzzy three-sphere vacua, and a possible large n limit. In this large n limit, the fuzzy funnel solution correctly reproduces the mass of an M5-brane.

A static self-tuning SO(3) × ₂ symmetric and translation invariant braneworld setup with flat brane is considered. We discuss the null energy conditions (NEC) for matter on the brane and in the bulk and prove that for the static regular background with broken Lorentz invariance the NEC and positiveness of the total energy density on the brane and NEC in the bulk cannot be satisfied simultaneously. Then we give some examples and elaborate some special cases.

We study different aspects of the non-perturbative superpotentials induced by Euclidean E3-branes on systems of D3/D7-branes located at Abelian orbifold singularities. We discuss in detail how the induced couplings are consistent with the U(1) symmetries carried by the D3/D7 branes. We construct different compact and non-compact examples, and show phenomenologically relevant couplings like μ-terms or certain Yukawa couplings generated by these E3 instantons. Some other novel effects are described. We show an example where E3 instantons combine with standard gauge instantons to yield new multi-instanton effects contributing to superpotential, along the lines of ref. [28]. In the case of non-SUSY Z_N tachyon-free singularities it is shown how E3-instantons give rise to non perturbative scalar couplings including exponentially suppressed scalar bilinears.

We present a simple method to automatically evaluate arbitrary tree-level amplitudes involving the production or decay of a heavy quark pair Q in a generic ^2S+1L_J^[1,8], S- or P-wave state, i.e., the leading short distance coefficients appearing in the NRQCD factorization formalism. Our approach is based on extracting the relevant contributions from the open heavy quark-antiquark amplitudes through an expansion with respect to the quark-antiquark relative momentum and the application of suitable color and spin projectors. To illustrate the capabilities of the method and its implementation in MadGraph a few applications to quarkonium collider phenomenology are presented.

The k-essence theories admit in general the superluminal propagation of the perturbations on classical backgrounds. We show that in spite of the superluminal propagation the causal paradoxes do not arise in these theories and in this respect they are not less safe than General Relativity.

Interactions between non-BPS non-Abelian vortices are studied in non-Abelian U(1) × SU(N) extensions of the Abelian-Higgs model in four dimensions. The distinctive feature of a non-Abelian vortex is the presence of an internal CP^N−1 space of orientational degrees of freedom. For fine-tuned values of the couplings, the vortices are BPS and there is no net force between two static parallel vortices at arbitrary distance. On the other hand, for generic values of the couplings the interactions between two vortices depend non-trivially on their relative internal orientations. We discuss the problem both with a numerical approach (valid for small deviations from the BPS limit) and in a semi-analytical way (valid at large vortex separations). The interactions can be classified with respect to their asymptotic property at large vortex separation. In a simpler fine-tuned model, we find two regimes which are quite similar to the usual type I/II Abelian superconductors. In the generic model we find other two new regimes: type I*/II*. Unlike the type I (type II) case, where the interaction is always attractive (repulsive), the type I* and II* have both attractive and repulsive interactions depending on the relative orientation. We have found a rich variety of interactions at small vortex separations. For some values of the couplings, a bound state of two static vortices at a non-zero distance exists.

We construct an inflationary model that is consistent with both large non-Gaussianity and a running spectral index. The scenario of modulated inflation suggests that modulated perturbation can induce the curvature perturbation with a large non-Gaussianity, even if the inflaton perturbation is negligible. Using this idea, we consider a multi-field extension of the modulated inflation scenario and examine the specific situation where different moduli are responsible for the perturbation at different scales. We suppose that the additional moduli (shooting-star moduli) is responsible for the curvature perturbation at the earlier inflationary epoch and it generates the fluctuation with n > 1 spectral index at this scale. After a while, another moduli (or inflaton) takes the place and generates the perturbation with n < 1. At the transition point the two fluctuations are comparable with each other. We show how the spectral index is affected by the transition induced by the shooting-star moduli.

Using a sample of over 600 million ϕ → K⁺K⁻ decays collected at the DAΦNE e⁺e⁻ collider, we have measured with the KLOE detector the absolute branching ratios for the charged kaon semileptonic decays, K^± → π⁰e^±ν(γ) and K^± → π⁰μ^±ν(γ). The results, BR(K_e3) = 0.04965±0.00038_stat±0.00037_syst and BR(K_μ3) = 0.03233±0.00029_stat±0.00026_syst, are inclusive of radiation. Accounting for correlations, we derive the ratio Γ(K_μ3)/Γ(K_e3) = 0.6511±0.0064. Using the semileptonic form factors measured in the same experiment, we obtain |V_us f₊(0)| = 0.2141 ±0.0013$.

We show by explicit construction the existence of various four dimensional models of type II superstrings with N = 2 supersymmetry, purely vector multiplet spectrum and no hypermultiplets. Among these, two are of special interest, at the field theory level they correspond to the two exceptional N = 2 supergravities of the magic square that have the same massless scalar field content as pure N = 6 supergravity and N = 3 supergravity coupled to three extra vector multiplets. The N = 2 model of the magic square that is associated to N = 6 supergravity is very peculiar since not only the scalar degrees of freedom but all the bosonic massless degrees of freedom are the same in both theories. All presented hyper-free N = 2 models are based on asymmetric orbifold constructions with = (4, 1) world-sheet superconformal symmetry and utilize the 2d fermionic construction techniques. The two exceptional N = 2 models of the magic square are constructed via a ``twisting mechanism" that eliminates the extra gravitini of the N = 6 and N = 3 extended supergravities and creates at the same time the extra spin-½ fermions and spin-1 gauge bosons which are necessary to balance the numbers of bosons and fermions. Theories of the magic square with the same amount of supersymmetry in three and five space-time dimensions are constructed as well, via stringy reduction and oxidation from the corresponding four-dimensional models.

We consider gauged sigma-models from a Riemann surface into a Kähler and hamiltonian G-manifold X. The supersymmetric = 2 theory can always be twisted to produce a gauged A-model. This model localizes to the moduli space of solutions of the vortex equations and computes the Hamiltonian Gromov-Witten invariants. When the target is equivariantly Calabi-Yau, i.e. when its first G-equivariant Chern class vanishes, the supersymmetric theory can also be twisted into a gauged B-model. This model localizes to the Kähler quotient X//G.

We present a set of algebraic functions for evaluating the coefficients of the scalar integral basis of a general one-loop amplitude. The functions are derived from unitarity cuts, but the complete cut-integral procedure has been carried out in generality so that it never needs to be repeated. Where the master integrals are known explicitly, the results here can be used as a black box with tree-level amplitudes as input and one-loop amplitudes as output.

We construct the action of a relativistic spinning particle from a non-linear realization of a space-time odd vector extension of the Poincaré group. For particular values of the parameters appearing in the lagrangian the model has a gauge world-line supersymmetry. As a consequence of this local symmetry there are BPS solutions in the model preserving 1/5 of the supersymmetries. A supersymmetric invariant quantization produces two decoupled 4d Dirac equations.

We study the conformal field theory dual of the type IIA flux compactification model of DeWolfe, Giryavets, Kachru and Taylor, with all moduli stabilized. We find its central charge and properties of its operator spectrum. We concentrate on the moduli space of the conformal field theory, which we investigate through domain walls in the type IIA string theory. The moduli space turns out to consist of many different branches. We use Bezout's theorem and Bernstein's theorem to enumerate the different branches of the moduli space and estimate their dimension.

We discuss a holographic dual of a non-relativistic (NR) string on AdS₅ × S⁵ . The NR string can be regarded as a semiclassical string around an AdS₂ classical solution corresponding to a straight Wilson line in the gauge-theory side. The quadratic action with respect to the fluctuations is composed of free massive and massless scalars, and free massive fermions on the AdS₂ world-sheet. We show that the complete agreement of the spectra between the NR string and a conformal quantum mechanics (CQM). Then we show a holographic relation between normalizable modes of the NR string and wave functions in the CQM. Then it may be argued from this result that an AdS₂/CFT₁ would be realized in AdS₅/CFT₄. We can really discuss a GKPW-type relation by considering non-normalizable modes of the NR string in Euclidean signature. Those modes give a source term insertion to the Wilson line, which can also be regarded as a small deformation of it.

We study the question of whether spontaneous U(1)_R breaking can occur in O'Raifeartaigh-type models of spontaneous supersymmetry breaking. We show that in order for it to occur, there must be a field in the theory with R-charge different from 0 or 2. We construct the simplest O'Raifeartaigh model with this property, and we find that for a wide range of parameters, it has a meta-stable vacuum where U(1)_R is spontaneously broken. This suggests that spontaneous U(1)_R breaking actually occurs in generic O'Raifeartaigh models.

We study the rolling tachyon and the dissipative quantum mechanics using the Thirring model with a boundary mass. We construct a boundary state for the dissipative quantum system in one dimension, which describes the system at the off-critical points as well as at the critical point. Then we extend the Thirring model with a boundary mass in order to depict the time evolution of an unstable D-branes with one direction wrapped on a circle of radius R, which is termed the inhomogeneous rolling tachyon. The analysis based on the Thirring model shows that the time dependent evolution of the inhomogeneous tachyon is possible only when 2/(3)^1/2 < R < 2.

We study the non-commutative matrix model which arises as the low-energy effective action of open strings in WZW models. We re-derive this fuzzy effective gauge dynamics in two different ways, without recourse to conformal field theory: The first method starts from a linearised version of the WZW σ-model, which is classically equivalent to an action of the Schild type, which in turn can be quantised in a natural way to yield the matrix model. The second method relies on purely geometric symmetry principles—albeit within the non-commutative spectral geometry that is provided by the boundary CFT data: we show that imposing invariance under extended gauge transformations singles out the string-theoretic action up to the relevant order in the gauge field. The extension of ordinary gauge transformations by tangential shifts is motivated by the gerbe structure underlying the classical WZW model and standard within Weitzenböck geometry—which is a natural reformulation of geometry to use when describing strings in targets with torsion.

We study the attractor equations for a quantum corrected prepotential = t³+iλ, with λ ∊ ,which is the only correction which preserves the axion shift symmetry and modifies the geometry. By performing computations in the ``magnetic'' charge configuration, we find evidence for interesting phenomena (absent in the classical limit of vanishing λ). For a certain range of the quantum parameter λ we find a ``separation'' of attractors, {i.e.} the existence of multiple solutions to the Attractor Equations for fixed supporting charge configuration. Furthermore, we find that, away from the classical limit, a ``transmutation'' of the supersymmetry-preserving features of the attractors takes place when λ reaches a particular critical value.

We consider general planar deformations of a circular distribution of NS5-branes. The near-horizon region of the latter admits, after a T-duality transformation, an exact conformal-field-theory description in terms of the coset model SU(2)/U(1) × SL(2, )/U(1). We derive the exactly marginal operators corresponding to an infinitesimal planar deformation using the conjectured holography between the coset model and the little string theory that resides on the worldvolume of the NS5-branes. Subsequently, we perform a complementary analysis of the same deformations using the associated = 1 supersymmetric σ model and verify the holographic correspondence. We explicitly demonstrate a precise match between the two approaches which rests upon a delicate interplay between exact conformal-field-theory operators and their semiclassical realizations in terms of target-space variables.

We show that a class of type IIA vacua recently found within the D = 4 effective approach corresponds to compactification on AdS₄ × S³ × S³/₂³. The results obtained using the effective method completely match the general ten-dimensional analysis for the existence of  = 1 warped compactifications on AdS₄ × M₆. In particular, we verify that the internal metric is nearly-Kähler and that for specific values of the parameters the Bianchi identity of the RR 2-form is fulfilled without sources. For another range of parameters, including the massless case, the Bianchi identity is satisfied when D6-branes are introduced. Solving the tadpole cancellation conditions in D = 4 we are able to find examples of appropriate sets of branes. In the second part of this paper we describe how an example with internal space ³ but with non nearly-Kähler metric fits into the general analysis of flux vacua.

We study the fusion of conformal interfaces in the c = 1 conformal field theory. We uncover an elegant structure reminiscent of that of black holes in supersymmetric theories. The role of the BPS black holes is played by topological interfaces, which (a) minimize the entropy function, (b) fix through an attractor mechanism one or both of the bulk radii, and (c) are (marginally) stable under splitting. One significant difference is that the conserved charges are logarithms of natural numbers, rather than vectors in a charge lattice, as for BPS states. Besides potential applications to condensed-matter physics and number theory, these results point to the existence of large solution-generating algebras in string theory.

We study two-Higgs models for large tan β and relatively large second Higgs mass. In this limit the second heavy Higgs should have small vev and therefore couples only weakly to two gauge bosons. Furthermore, the couplings to down-type quarks can be significantly modified (so long as the second Higgs is not overly heavy). Both these facts have significant implications for search strategies at the LHC and ILC. We show how an effective theory and explicit fundamental two-Higgs model approach are related and consider the additional constraints in the presence of supersymmetry or Z₂ flavor symmetries. We argue that the best tests of the two-Higgs doublet potential are likely to be measurements of the light Higgs branching fractions. We show how higher dimension operators that have recently been suggested to raise the light Higgs mass are probably best measured and distinguished in this way.

We consider the most general class of supersymmetric solutions of D = 11 supergravity consisting of a warped product of AdS₅ with a six-dimensional internal manifold ₆, which are dual to N = 2 super conformal field theories in d = 4. For any such ₆ we construct the full non-linear Kaluza-Klein ansatz for the reduction of D = 11 supergravity on ₆ down to D = 5 SU(2) × U(1) gauged supergravity, at the level of the bosonic fields. This allows one to uplift any solution of the D = 5 supergravity to obtain a solution of D = 11 supergravity for any given ₆. Using an explicit ₆, corresponding to M5-branes wrapping holomorphic curves in a Calabi-Yau two-fold, we uplift some solutions and comment upon their interpretation.

We exhibit a simple and robust mechanism for bulk mediation of supersymmetry breaking between hidden and visible sectors localized on geometrically separated D-branes in type II string theory. The mediation proceeds via RR p-forms that couple via linear Chern-Simons terms to the abelian vector bosons on the branes. From a 4-d low energy perspective, the mechanism reduces to U(1) mediation.

We present the full details of a calculation at next-to-leading order of the momentum diffusion coefficient of a heavy quark in a hot, weakly coupled, QCD plasma. Corrections arise at (g_s); physically they represent interference between overlapping scatterings, as well as soft, electric scale (p ∼ gT) gauge field physics, which we treat using the hard thermal loop (HTL) effective theory. In 3-color, 3-flavor QCD, the momentum diffusion constant of a fundamental representation heavy quark at NLO is κ = (16π/3)α_s²T³(ln (1/g_s)+0.07428+1.9026g_s). We extend the computation to a heavy fundamental representation ``probe'' quark in large N_c, = 4 Super Yang-Mills theory, where the result is κ^(SYM) = (λ²T³/6π)(ln (1/√λ)+0.4304+0.8010√λ) (where λ = g²N_c is the t'Hooft coupling). In the absence of some resummation technique, the convergence of perturbation theory is poor.

We describe in detail the calculation of the two-loop corrections to the QED Bhabha scattering cross section due to the vacuum polarization by heavy fermions. Our approach eliminates one mass scale from the most challenging part of the calculation and allows us to obtain the corrections in a closed analytical form. The result is valid for arbitrary values of the heavy fermion mass and the Mandelstam invariants, as long as s, t, u >> m_e².

In spite of the breakthrough in non-perturbative chiral gauge theories during the last decade, the present formulation has stubborn artefacts. Independently of the fermion representation one is confronted with unwanted CP violation and infinitely many undetermined weight factors. Renormalization group identifies the culprit. We demonstrate the procedure on Weyl fermions in a real representation.

We improve a previous quenched result for heavy-light pseudoscalar meson decay constants with the light quark taken to be the strange quark. A finer lattice resolution (a ≈ 0.05 fm) in the continuum limit extrapolation of the data computed in the static approximation is included. We also give further details concerning the techniques used in order to keep the statistical and systematic errors at large lattice sizes L/a under control. Our final result, obtained by combining these data with determinations of the decay constant for pseudoscalar mesons around the D_s, follows nicely the qualitative expectation of the 1/m-expansion with a (relative) 1/m-term of about −0.5 GeV/m_PS. At the physical b-quark mass we obtain F_Bs = 193(7) MeV, where all errors apart from the quenched approximation are included.

A model with N species of massless fermions interacting via (microscopic) gravitational torsion in de Sitter spacetime is investigated in the limit N → ∞. The U_V(N) × U_A(N) flavor symmetry is broken dynamically irrespective of the (positive) value of the induced four-fermion coupling. This model is equivalent to a theory with free but massive fermions fluctuating about the chiral condensate. When the fermions are integrated out in a way demonstrated long ago by Candelas and Raine, the associated gap equation together with the Friedmann equation predict that the Hubble parameter vanishes. Introducing a matter sector (subject to a finite gauge symmetry) as a source for subsequent cosmology, the neutral Goldstone field acquires mass by the chiral anomaly, resulting in a Planck-scale axion.

We present the calculation of the dominant next to leading order QCD corrections to Higgs boson production in association with three jets via vector boson fusion in the form of a NLO parton-level Monte Carlo program. QCD corrections to integrated cross sections are modest, while the shapes of some kinematical distributions change appreciably at NLO. Scale uncertainties are shown to be reduced at NLO for the total cross section and for distributions. We consider a central jet veto at the LHC and analyze the veto probability for typical vector boson fusion cuts. Scale uncertainties of the veto probability are sufficiently small at NLO for precise Higgs coupling measurements at the LHC.

We algebraically prove the cancellation of the β function at all order of perturbation theory of = 2 supersymmetric gauge theories with a vanishing one-loop β function. The proof generalises that recently given for the = 4 case. It uses the consistent Slavnov-Taylor identities of the shadow dependent formulation. We also demonstrate the cancellation at all orders of the anomalous dimensions of vector and hypermultiplet ½BPS operators.

Supersymmetry breaking in a metastable vacuum allows one to build simple and concrete models of gauge mediation. Generation of gaugino masses requires that R-symmetry be broken in this vacuum. In general, there are two possible ways to break R-symmetry, explicitly or spontaneously. We find that the MSSM phenomenology depends crucially on how this breaking occurs in the Hidden Sector. Explicit R-symmetry breaking models can lead to fairly standard gauge mediation, but we argue that in the context of ISS-type models this only makes sense if B = 0 at the mediation scale, which leads to high tan β. If on the other hand, R-symmetry is broken spontaneously, then R-symmetry violating soft terms tend to be suppressed with respect to R-symmetry preserving ones, and one is led to a scenario with large scalar masses. These models interpolate between standard gauge mediation and split SUSY models. We provide benchmark points for the two scenarios. They demonstrate that the specific dynamics of the Hidden Sector—the underlying nature of supersymmetry and R-symmetry breaking—affects considerably the mass spectrum of the MSSM, and vice versa.

We discuss Fermi interactions of four hyperini generated by ``stringy'' instantons in a Type I/Heterotic dual pair on T⁴/₂.

It is argued that it is valid to use QCD sum rules to determine the scalar and pseudoscalar two-point functions at zero momentum, which in turn determine the ratio of the strange to non-strange quark condensates R_su = ⟨s⟩/⟨q⟩ with (q = u, d). This is done in the framework of a new set of QCD Finite Energy Sum Rules (FESR) that involve as integration kernel a second degree polynomial, tuned to reduce considerably the systematic uncertainties in the hadronic spectral functions. As a result, the parameters limiting the precision of this determination are Λ_QCD, and to a major extent the strange quark mass. From the positivity of R_su there follows an upper bound on the latter: (2 GeV) ⩽ 121 (105) MeV, for Λ_QCD = 330 (420) MeV.

We analyze the effect of an isospin chemical potential μ_I in the Sakai-Sugimoto model, which is the string dual of a confining gauge theory related to large N_c QCD, at temperatures below the chiral symmetry restoration temperature. For small chemical potentials we show that the results agree with expectations from the low-energy chiral Lagrangian, and the charged pion condenses. When the chemical potential reaches a critical value μ_I = μ_crit ≃ 1.7m_ρ, the lowest vector meson (the ``rho meson'') becomes massless, and it condenses (in addition to the pion condensate) for μ_I > μ_crit. This spontaneously breaks the rotational symmetry, as well as a residual U(1) flavor symmetry. We numerically construct the resulting new ground state for μ_I > μ_crit.

G₂ Yang-Mills theory is an interesting laboratory to investigate non-perturbative effects. On one hand, no conventional quark confinement via a linearly rising potential is present. On the other hand, its thermodynamic properties are similar to ordinary SU(N) Yang-Mills theory. Finally, it has been conjectured that gluons are removed from the physical spectrum in the same way as in SU(N) Yang-Mills theory. The last claim will be explored by determining the Landau-gauge ghost and gluon propagators, as well as the Faddeev-Popov operator eigenspectrum, in G₂ lattice gauge theory in two and three dimensions. The results are found to agree qualitatively with the SU(2) and SU(3) case. Therefore, the conjecture that Yang-Mills theories with different gauge groups are qualitatively similar on the level of their Landau gauge Green's functions is supported.

We establish the correspondence between, on one side, the possible gaugings and massive deformations of half-maximal supergravity coupled to vector multiplets and, on the other side, certain generators of the associated very extended Kac-Moody algebras. The difference between generators associated to gaugings and to massive deformations is pointed out. Furthermore, we argue that another set of generators are related to the so-called quadratic constraints of the embedding tensor. Special emphasis is placed on a truncation of the Kac-Moody algebra that is related to the bosonic gauge transformations of supergravity. We give a separate discussion of this truncation when non-zero deformations are present. The new insights are also illustrated in the context of maximal supergravity.

We study the ILC phenomenology of Kaluza-Klein (KK) modes along two universal extra dimensions compactified on the chiral square. We compute production cross sections of various (1, 0) particles at the ILC with (s)^1/2 = 1 TeV, focusing on decays of KK-leptons and the KK partner of the hypercharge gauge boson down to the ``spinless photon'', which is the lightest KK particle. We contrast this model to one universal extra dimension with KK-photon (spin-1) and supersymmetry with neutralino (spin-1/2) or gravitino (spin-3/2) dark matter. We also investigate the discovery potential for (1, 1) KK bosons as s-channel resonances.

In the literatures, several types of thick smooth brane configurations in a pure geometric Weyl integrable 5-dimensional space time have been presented. The Weyl geometry is a non-Riemannian modification of 5-dimensional Kaluza-Klein (KK) theory. All these thick brane solutions preserve 4-dimensional Poincaré invariance, and some of them break Z₂-symmetry along the extra dimension. In this paper, we study localization of various matter fields on these pure geometrical thick branes, which also localize the graviton. We present the shape of the potential of the corresponding Schrödinger problem and obtain the lowest KK mode. It is shown that, for both spin 0 scalars and spin 1 vectors, there exists a continuum gapless spectrum of KK states with m² > 0. But only the massless mode of scalars is found to be normalizable on the brane. However, for the massless left or right chiral fermion localization, there must be some kind of Yukawa coupling. For a special coupling, there exist a series of discrete massive KK modes with m² > 0. It is also showed that for a given coupling constant only one of the massless chiral modes is localized on the branes.

In this note we set-up an explicit 5D construction of AdS-fragmentation, whereby a single black ring splits-up into a multi-black ring configuration. Furthermore it is seen that these fragmented rings are equivalent to a direct 5D lift of 4D multi-center black holes. Along the way we also determine the 4D/5D transformations relevant for multi-center charges. It is seen that the physical charges involved in black ring fragmentation are Page charges arising due to 5D Chern-Simons terms. As an application of these methods, we reproduce the total angular momentum of concentric black rings, originally due to Gauntlett and Gutowski. Finally we provide a geometric interpretation of fragmented black rings using the idea of split-spectral flows, which seeks to study charge shifts of a given black ring due to fluxes generated in a multi-ring background.

We study a class of non-geometric string vacua realized as completely soluble superconformal field theory (SCFT). These models are defined as `interpolating orbifolds' of K3 × S<sup>1</sup> by the mirror transformation acting on the K3 fiber combined with the half-shift on the S<sup>1</sup>-base. They are variants of the T-folds, the interpolating orbifolds by T-duality transformations, and thus may be called `mirrorfolds'. Starting with arbitrary (compact or non-compact) Gepner models for the K3 fiber, we construct modular invariant partition functions of general mirrorfold models. In the case of compact K3 fiber the mirrorfolds only yield non-supersymmetric string vacua. They exhibit IR instability due to winding tachyon condensation which is similar to the Scherk-Schwarz type circle compactification. When the fiber SCFT is non-compact (say, the ALE space in the simplest case), on the other hand, both supersymmetric and non-supersymmetric vacua can be constructed. The non-compact non-supersymmetric mirrorfolds can get stabilised at the level of string perturbation theory. We also find that in the non-compact supersymmeric mirrorfolds D-branes are always non-BPS. These D-branes can get stabilized against both open- and closed-string marginal deformations.

We present a trace formula for a Witten type Index for superconformal field theories in d = 3, 5 and 6 dimensions, generalizing a similar recent construction in d = 4. We perform a detailed study of the decomposition of long representations into sums of short representations at the unitarity bound to demonstrate that our trace formula yields the most general index (i.e. quantity that is guaranteed to be protected by superconformal symmetry alone) for the corresponding superalgebras. Using the dual gravitational description, we compute our index for the theory on the world volume of N M2 and M5 branes in the large N limit. We also compute our index for recently constructed Chern Simons theories in three dimensions in the large N limit, and find that, in certain cases, this index undergoes a large N phase transition as a function of chemical potentials.

In the gauge invariant formulation of U(1) chiral lattice gauge theories based on the Ginsparg-Wilson relation, the gauge field dependence of the fermion measure is determined through the so-called measure term. We derive a closed formula of the measure term on the finite volume lattice. The Wilson line degrees of freedom (torons) of the link field are treated separately to take care of the global integrability. The local counter term is explicitly constructed with the local current associated with the cohomologically trivial part of the gauge anomaly in finite volume. The resulted formula is very close to the known expression of the measure term in infinite volume with a single parameter integration, and would be useful in practical implementations.

We consider configurations of D4−D8−8 branes which correspond to large N QCD with non-vanishing temperature and chemical potential for baryon number and isospin. We study the holographic dual of this model and find a rich phase structure. The phases, distinguished by the values of quark condensates, are separated by the surfaces of first order phase transitions. The picture is in many respects similar to the expected phase structure of QCD in the chiral limit.

We compute the three-body decays of charged sleptons and sneutrinos into other sleptons. These decays are of particular interest in SUSY-breaking models with non-universal Higgs mass parameters, where the left-chiral sleptons can be lighter than the right-chiral ones, and lighter than the lightest neutralino. We present the formulas for the three-body decay widths together with a numerical analysis in the context of gaugino-mediated SUSY breaking with a gravitino LSP.

We discuss the low energy effective theory of an M5-brane wrapped on a smooth holomorphic four-cycle of K3 × T², including the special case of T⁶. In particular we give the lowest order equations of motion and resolve a puzzle concerning the counting of massless modes that was reported in hep-th/9906094. In order to find agreement with black hole entropy and anomaly inflow arguments we propose that some of the moduli become massive.

Inflation may occur while rolling into the metastable supersymmetry-breaking vacuum of massive supersymmetric QCD. We explore the range of parameters in which slow-roll inflation and long-lived metastable supersymmetry breaking may be simultaneously realized. The end of slow-roll inflation in this context coincides with the spontaneous breaking of a global symmetry, which may give rise to significant curvature perturbations via inhomogenous preheating. Such spontaneous symmetry breaking at the end of inflation may give rise to observable non-gaussianities, distinguishing this scenario from more conventional models of supersymmetric hybrid inflation.

We continue the studies of our earlier proposal for an AdS/CFT correspondence for time-dependent supergravity backgrounds. We note that by performing a suitable change of variables, the dual super Yang-Mills theory lives on a flat base space, and the time-dependence of the supergravity background is entirely encoded in the time-dependent couplings (gauge and axionic) and their supersymmetric completion. This form of the SYM allows a detailed perturbative analysis to be performed. In particular the one-loop Wilsonian effective action of the boundary SYM theory is computed. By using the holographic UV/IR relation, we propose a way to extract the bulk metric from the Wilsonian effective action; and we find that the bulk metric of our supergravity solutions can be reproduced precisely. While the bulk geometry can have various singularities such as geodesic incompleteness, gauge theory quantum effects can introduce higher derivative corrections in the effective action which can serve as a way to resolve the singularities.

We calculate the order (α²α_s³) interference effect between the gluon fusion and weak boson fusion processes allowed at the one-loop level in Higgs boson plus 2 jet production at the LHC. The corresponding one-loop amplitudes, which have not been considered in the literature so far, are evaluated analytically using dimensional regularisation and the necessary master integrals with massive propagators are reported. It is discussed in detail how various mechanisms conspire to make this contribution numerically negligible for experimental studies at the LHC.

We use the new N = (2, 2) vector multiplets to clarify T-dualities for generalized Kähler geometries. Following the usual procedure, we gauge isometries of nonlinear σ-models and introduce Lagrange multipliers that constrain the field-strengths of the gauge fields to vanish. Integrating out the Lagrange multipliers leads to the original action, whereas integrating out the vector multiplets gives the dual action. The description is given both in N = (2, 2) and N = (1, 1) superspace.

We discuss non-perturbative QCD contributions to jet observables, computing their dependence on the jet radius R, and on the colour and transverse momentum of the parton initiating the jet. We show, using analytic QCD models of power corrections as well as Monte Carlo simulations, that hadronisation corrections grow at small values of R, behaving as 1/R, while underlying event contributions grow with the jet area as R². We highlight the connection between hadronisation corrections to jets and those for event shapes in e⁺e⁻ and DIS; we note the limited dependence of our results on the choice of jet algorithm; finally, we propose several measurements in the context of which to test or implement our predictions. The results presented here reinforce the motivation for the use of a range of R values, as well as a plurality of infrared-safe jet algorithms, in precision jet studies at hadron colliders.

We reconsider the Enriques Calabi Yau (FHSV) model and its string derivation and argue that the Octonionic magic supergravity theory admits a string interpretation closely related to the Enriques model. The uplift to D = 6 of the Octonionic magic model has 16 abelian vectors related to the rank of Type I and Heterotic strings.

I consider the two-body decay of a particle at a hadron collider into a visible and an invisible particle, generalizing W→eν, where the masses of the decaying particle and the invisible decay particle are, a priori, unknown. I prove that the transverse mass, when maximized over possible kinematic configurations, can be used to determine both of the unknown masses. I argue that the proof can be generalized to cover cases such as decays of pair-produced superpartners to the lightest, stable superpartner at the Large Hadron Collider.

In this paper we investigate the attractor mechanism in the five dimensional low energy supergravity theory corresponding to M-theory compactified on a Calabi-Yau threefold CY₃. Using very special geometry, we derive the general first-order attractor flow equations for BPS and non-BPS solutions in five-dimensional Gibbons-Hawking spaces. Especially, considering the supersymmetric solution, we obtain the first-order flow equations for supersymmetric (multi)black rings. We also solve the flow equations and discuss some properties of the solutions of flow equations.

We study a class of Lorentz violating quantum field theories that contain higher space derivatives, but no higher time derivatives, and become renormalizable in the large N expansion. The fixed points of their renormalization-group flows provide examples of exactly ``weighted scale invariant'' theories, which are noticeable Lorentz violating generalizations of conformal field theories. We classify the scalar and fermion models that are causal, stable and unitary. Solutions exist also in four and higher dimensions, even and odd. In some explicit four dimensional examples, we compute the correlation functions to the leading order in 1/N and the critical exponents to the subleading order. We construct also RG flows interpolating between pairs of fixed points.

We study a class of solutions of IIB supergravity which are asymptotically AdS₅ × Y^p,q. They have an × SO(4) × SU(2) × U(1) isometry and preserve half of the 8 supercharges of the background geometry. They are described by a set of second order differential equations that we have found and analysed in a previous paper, where we studied 1/8 BPS states in the maximally supersymmetric AdS₅ × S⁵ background. These geometries correspond to certain chiral primary operators of the = 1 superconformal quiver theories, dual to IIB theory on AdS₅ × Y^p,q. We also show how to recover the AdS₅ × Y^p,q backgrounds by suitably doubling the number of preserved supersymmetries. We then solve the differential equations perturbatively in a large AdS₅ radius expansion, imposing asymptotic AdS₅ × Y^p,q boundary conditions. We compute the global baryonic and mesonic charges, including the R-charge. As for the computation of the mass, i.e. the conformal dimension Δ of the dual field theory operators, which is notoriously subtle in asymptotically AdS backgrounds, we adopt the general formalism due to Wald and collaborators, which gives a finite result, and verify the relation Δ = 3R/2, demanded by the = 1 superconformal algebra.

Extending our previous results on trans-Planckian (Gs >> ℏ) scattering of light particles in quantum string-gravity we present a calculation of the corresponding S-matrix from the region of large impact parameters (b >> G(s)^1/2>λ_s) down to the regime where classical gravitational collapse is expected to occur. By solving the semiclassical equations of a previously introduced effective-action approximation, we find that the perturbative expansion around the leading eikonal result diverges at a critical value b = b_c = O(G(s)^1/2), signalling the onset of a new (black-hole related?) regime. We then discuss the main features of our explicitly unitary S-matrix—and of the associated effective metric—down to (and in the vicinity of) b = b_c, and present some ideas and results on its extension all the way to the b→0 region. We find that for b < b_c the physical field solutions are complex-valued and the S-matrix shows additional absorption, related to a new production mechanism. The field solutions themselves are, surprisingly, everywhere regular, suggesting a quantum-tunneling—rather than a singular-geometry—situation.

Medium-induced gluon radiation is usually identified as the dominant dynamical mechanism underling the jet quenching phenomenon observed in heavy-ion collisions. In its actual implementation, multiple medium-induced gluon emissions are assumed to be independent, leading, in the eikonal approximation, to a Poisson distribution. Here, we introduce a medium term in the splitting probabilities so that both medium and vacuum contributions are included on the same footing in a DGLAP approach. The improvements include energy-momentum conservation at each individual splitting, medium-modified virtuality evolution and a coherent implementation of vacuum and medium splitting probabilities. Noticeably, the usual formalism is recovered when the virtuality and the energy of the parton are very large. This leads to a similar description of the suppression observed in heavy-ion collisions with values of the transport coefficient of the same order as those obtained using the quenching weights.

Using the simple setting of 3D N = 1 supergravity, we show how the tensor calculus of supergravity can be extended to manifolds with boundary. We present an extension of the standard F-density formula which yields supersymmetric bulk-plus-boundary actions. To construct additional separately supersymmetric boundary actions, we decompose bulk supergravity and bulk matter multiplets into co-dimension one submultiplets. As an illustration we obtain the supersymmetric extension of the York-Gibbons-Hawking extrinsic curvature boundary term. We emphasize that our construction does not require any boundary conditions on off-shell fields. This gives a significant improvement over the existing orbifold supergravity tensor calculus.

We derive semiclassical ground state solutions that correspond to the quantum Hall states earlier found in the Maxwell-Chern-Simons matrix theory. They realize the Jain composite-fermion construction and their density is piecewise constant as that of phenomenological wave functions. These results support the matrix theory as a possible effective theory of the fractional Hall effect. A crucial role is played by the constraint limiting the degeneracy of matrix states: we find its explicit gauge invariant form and clarify its physical interpretation.

Black branes in AdS₅ appear in a four parameter family labeled by their velocity and temperature. Promoting these parameters to Goldstone modes or collective coordinate fields—arbitrary functions of the coordinates on the boundary of AdS₅—we use Einstein's equations together with regularity requirements and boundary conditions to determine their dynamics. The resultant equations turn out to be those of boundary fluid dynamics, with specific values for fluid parameters. Our analysis is perturbative in the boundary derivative expansion but is valid for arbitrary amplitudes. Our work may be regarded as a derivation of the nonlinear equations of boundary fluid dynamics from gravity. As a concrete application we find an explicit expression for the expansion of this fluid stress tensor including terms up to second order in the derivative expansion.

Deformations of maximal supergravity theories induced by gauging non-abelian subgroups of the duality group reveal the presence of charged M-theory degrees of freedom that are not necessarily contained in supergravity. The relation with M-theory degrees of freedom is confirmed by the representation assignments under the duality group of the gauge charges and the ensuing vector and tensor gauge fields. The underlying hierarchy of these gauge fields is required for consistency of general gaugings. As an example gauged maximal supergravity in three space-time dimensions is presented in a version where all possible tensor fields appear.

We consider Standard Model Higgs boson production by gluon-gluon fusion in hadron collisions. We present a calculation of the next-to-next-to-leading order QCD corrections to the cross section in the H → WW → lνlν and H → ZZ → 4l decay channels. The calculation is implemented in the parton level Monte Carlo program HNNLO and allows us to apply arbitrary cuts on the final state leptons and the associated jet activity. We present selected numerical results for the signal cross section at the LHC, by using all the nominal cuts proposed for the forthcoming Higgs boson search.

Very recently in [1] Alday and Maldacena gave a string theory prescription for computing (all) planar amplitudes in = 4 supersymmetric gauge theory at strong coupling using the AdS/CFT correspondence. These amplitudes are determined by a classical string solution and contain a universal exponential factor involving the action of the classical string. On the gauge theory side, expressions for perturbative amplitudes at strong coupling were previously proposed only for specific helicities of external particles — the maximally helicity violating or MHV amplitudes. These follow from the exponential ansatz of Bern, Dixon and Smirnov [2] for MHV amplitudes in = 4 SYM. In this paper we examine the amplitudes dependence on helicities and particle-types of external states. We consider the prefactor of string amplitudes and give arguments suggesting that the prefactor at strong coupling should be the same as the Yang-Mills tree-level amplitude for the same process. This implies that scattering amplitudes in = 4 SYM simplify dramatically in the strong coupling limit. It follows from our proposal that in this limit all (MHV and non-MHV) n-point amplitudes are given by the (known) tree-level Yang-Mills result times the helicity-independent (and particle-type-independent) universal exponential.

In order to deepen our understanding of the nature of the deconfinement phase transition for various gauge groups, we investigate SU(4) Yang-Mills theory in 2+1 dimensions. We find that the transition is weakly first order. We perform extensive Monte Carlo simulations on lattices with temporal extent N_t = 3, 4, and 5, and spatial sizes up to N_s = 20 N_t. We observe coexistence of confined and deconfined phases at the critical temperature, and finite-size scaling shows consistency with first order exponents. The continuum extrapolation of the latent heat yields L_h/T_c³ = 0.188(17).

We present the first determination of the strong coupling constant from a fit of next-to-next-to-leading order QCD predictions to event-shape variables, measured in e⁺e⁻ annihilations at LEP. The data have been collected by the ALEPH detector at centre-of-mass energies between 91 and 206 GeV. Compared to results of next-to-leading order fits we observe that the central fit values are lower by about 10 %, with considerably reduced scatter among the results obtained with different event-shape variables. The dominant systematic uncertainty from renormalization scale variations is reduced by a factor of two. By combining the results for several event-shape variables and centre-of-mass energies, we find α_s(M²_Z) = 0.1240 ± 0.0008 (stat) ± 0.0010 (exp) ± 0.0011 (had) ± 0.0029 (theo).

We formulate all the five dimensional gauged maximal supergravity theories as non-linear realisations of the semi-direct product of E₁₁ and a set of generators which transform according to the first fundamental representation l of E₁₁. The latter introduces a generalised space-time which plays a crucial role for these theories. We derive the E₁₁ and l transformations of all the form fields and their dynamics. We also formulate the five dimensional gauged supergravity theories using the closure of the supersymmetry algebra. We show that this closes on the bosonic field content predicted by E₁₁ and we derive the field transformations and the dynamics of this theory. The results are in precise agreement with those found from the E₁₁ formulation. This provides a very detailed check of E₁₁ and also the first substantial evidence for the generalised space-time. The results can be generalised to all gauged maximal supergravities, thus providing a unified framework of all these theories as part of E₁₁.

In a recent paper [1] we showed that N = 1 supersymmetric QCD in the presence of certain superpotential deformations has a rich landscape of supersymmetric and non-supersymmetric vacua. In this paper we embed this theory in string theory as a low energy theory of intersecting NS and D-branes. We find that in the region of parameter space of brane configurations that can be reliably studied using classical string theory, the vacuum structure is qualitatively similar to that in the field theory regime. Effects that in field theory come from one loop corrections arise in string theory as classical gravitational effects. The brane construction provides a useful guide to the structure of stable and metastable gauge theory vacua.

We study the formation and evolution of an interconnected string network in large-scale field-theory numerical simulations, both in flat spacetime and in expanding universe. The network consists of gauge U(1) strings of two different kinds and their bound states, arising due to an attractive interaction potential. We find that the network shows no tendency to ``freeze'' and appears to approach a scaling regime, with all characteristic lengths growing linearly with time. Bound strings constitute only a small fraction of the total string length in the network.

We study the Fareytail expansion of the topological partition function of = 4 SU(N) super Yang-Mills theory on K3. We argue that this expansion corresponds to a sum over geometries in asymptotically AdS₃ spacetime, which is holographically dual to a large number of coincident fundamental heterotic strings.

We present a detailed study of the collider observable m_T2 applied for pair-produced superparticles decaying to visible particles and a pair of invisible lightest supersymmetric particles (LSPs). Analytic expressions of the maximum of m_T2 over all events (m_T2^max) are derived. It is noticed that if the decay product of each superparticle involves more than one visible particle, m_T2^max being a function of the trial LSP mass m_χ has a kink structure at m_χ = true LSP mass, which can be used to determine the mother superparticle mass and the LSP mass simultaneously. To see how well m_T2^max can be constructed from collider data, a Monte-Carlo analysis of the gluino m_T2 is performed for some superparticle spectra.

The worldsheet of a macroscopic fundamental superstring in the Green-Schwarz light-cone gauge is viewed as a possible boundary hologram of the near horizon region of a small black string. For toroidally compactified strings, the hologram has global symmetries of AdS₃ × S^d−1 × T^8−d (d = 3, ..., 8), only some of which extend to local conformal symmetries. We construct the bulk string theory in detail for the particular case of d = 3. The symmetries of the hologram are correctly reproduced from this exact worldsheet description in the bulk. Moreover, the central charge of the boundary Virasoro algebra obtained from the bulk agrees with the Wald entropy of the associated small black holes. This construction provides an exact CFT description of the near horizon region of small black holes both in Type-II and heterotic string theory arising from multiply wound fundamental superstrings.

We consider, in de Sitter spacetime, both freely falling and static two-level atoms in interaction with a conformally coupled massless scalar field in the de Sitter-invariant vacuum, and separately calculate the contributions of vacuum fluctuations and radiation reaction to the atom's spontaneous excitation rate. We find that spontaneous excitations occur even for the freely falling atom as if there is a thermal bath of radiation at the Gibbons-Hawking temperature and we thus recover, in a different physical context, the results of Gibbons and Hawking that reveals the thermal nature of de Sitter spacetime. Similarly, for the case of the static atom, our results show that the atom also perceives a thermal bath which now arises as a result of the intrinsic thermal nature of de Sitter spacetime and the Unruh effect associated with the inherent acceleration of the atom.

Various holographic approaches to QCD in five dimensions are explored using input both from the putative five-dimensional non-critical string theory as well as QCD. It is argued that a gravity theory in five dimensions coupled to a dilaton and an axion may capture the important qualitative features of pure YM theory. A part of the effects of higher α'-corrections is resummed into a dilaton potential. The potential is shown to be in one-to-one correspondence with the exact β-function of QCD, and its knowledge determines the full structure of the vacuum solution. The geometry near the UV boundary is that of AdS₅ with logarithmic corrections reflecting the asymptotic freedom of QCD. We find that all relevant confining backgrounds have an IR singularity of the ``good" kind that allows unambiguous spectrum computations. Near the singularity the 't Hooft coupling is driven to infinity. Asymptotically linear glueball masses can also be achieved. The classification of all confining asymptotics, the associated glueball spectra and meson dynamics are addressed in a companion paper arXiv:0707.1349

We investigate sum rules for heavy-to-light transition form factors at large recoil derived from correlation functions with interpolating currents for light pseudoscalar or vector fields in soft-collinear effective theory (SCET). We consider both, factorizable and non-factorizable contributions at leading power in the Λ/m_b expansion and to first order in the strong coupling constant α_s, neglecting contributions from 3-particle distribution amplitudes in the B-meson. We pay particular attention to various sources of parametric and systematic uncertainties. We also discuss certain form factor ratios where part of the hadronic uncertainties related to the B-meson distribution amplitude and to logarithmically enhanced α_s corrections cancel.

We present a complete basis of multi-trace multi-matrix operators that has a diagonal two point function for the free matrix field theory at finite N. This generalises to multiple matrices the single matrix diagonalisation by Schur polynomials. Crucially, it involves intertwining the gauge group U(N) and the global symmetry group U(M) with Clebsch-Gordan coefficients of symmetric groups S_n. When applied to = 4 super Yang-Mills we consider the U(3) subgroup of the full symmetry group. The diagonalisation allows the description of a dual basis to multi-traces, which permits the characterisation of the metric on operators transforming in short representations at weak coupling. This gives a framework for the comparison of quarter and eighth-BPS giant gravitons of AdS₅ × S⁵ spacetime to gauge invariant operators of the dual = 4 SYM.

We develop techniques to compute the one-loop anomalous dimensions of operators in the = 4 super Yang-Mills theory that are dual to open strings ending on boundstates of sphere giant gravitons. Our results, which are applicable to excitations involving an arbitrary number of open strings, generalize the single string results of hep-th/0701067. The open strings we consider carry angular momentum on an S³ embedded in the S⁵ of the AdS₅ × S⁵ background. The problem of computing the one loop anomalous dimensions is replaced with the problem of diagonalizing an interacting Cuntz oscillator Hamiltonian. Our Cuntz oscillator dynamics illustrates how the Chan-Paton factors for open strings propagating on multiple branes can arise dynamically.

We present a simple solution to the crossing equation for an open string worldsheet reflection matrix, with boundaries preserving a SU(1|2)² residual symmetry, which constrains the boundary dressing factor. In addition, we also propose an analogous crossing equation for the dressing factor where extra boundary degrees of freedom preserve a SU(2|2)² residual symmetry.

We investigate boundary dynamics of orbifold conformal field theory involving T-duality twists. Such models typically appear in contexts of non-geometric string compactifications that are called monodrofolds or T-folds in recent literature. We use the framework of boundary conformal field theory to analyse the models from a microscopic world-sheet perspective. In these backgrounds there are two kinds of D-branes that are analogous to bulk and fractional branes in standard orbifold models. The bulk D-branes in T-folds allow intuitive geometrical interpretations and are consistent with the classical analysis based on the doubled torus formalism. The fractional branes, on the other hand, are `non-geometric' at any point in the moduli space and have not been considered in the doubled torus analysis so far. We compute cylinder amplitudes between the bulk and fractional branes, and find that the lightest modes of the open string spectra show intriguing non-linear dependence on the moduli (location of the brane or value of the Wilson line), suggesting that the physics of T-folds, when D-branes are involved, could deviate from geometric backgrounds even at low energies. We also extend our analysis to the models with SU(2) WZW fibre at arbitrary levels.

There have been a number of forms of a conjecture that there is a universal lower bound on the ratio, η/s, of the shear viscosity, η, to entropy density, s, with several different domains of validity. We examine the various forms of the conjecture. We argue that a number of variants of the conjecture are not viable due to the existence of theoretically consistent counterexamples. We also note that much of the evidence in favor of a bound does not apply to the variants which have not yet been ruled out.

We study the entropy function of two = 2 string compactifications obtained as freely acting orbifolds of = 4 theories: the STU model and the FHSV model. The Gauss-Bonnet term for these compactifications is known precisely. We apply the entropy function formalism including the contribution of this four derivative term and evaluate the entropy of dyons to the first subleading order in charges for these models. We then propose a partition function involving the product of three Siegel modular forms of weight zero which reproduces the degeneracy of dyonic black holes in the STU model to the first subleading order in charges. The proposal is invariant under all the duality symmetries of the STU model. For the FHSV model we write down an approximate partition function involving a Siegel modular form of weight four which captures the entropy of dyons in the FHSV model in the limit when electric charges are much larger than magnetic charges.

We find the boundary action for Euclidean AdS₂ D-branes in H⁺₃. This action is consistent with the D-branes' symmetries and with the H⁺₃-Liouville relation for disc correlators. It can be used for performing free-field calculations in the H⁺₃ model with boundaries. We explicitly perform the Coulomb-like integrals which appear in the free-field calculation of the bulk one-point function, and find agreement with previously known conformal bootstrap results.

In the previous paper hep-th/0604112 we calculated the first of the five planar two-loop diagrams for the Lcc vertex of the general non-Abelian Yang-Mills theory, the vertex which allows us in principle to obtain all other vertices via the Slavnov-Taylor identity. The integrand of this first diagram has a simple Lorentz structure. In this letter we present the result for the second diagram, whose integrand has a complicated Lorentz structure. The calculation is performed in the D-dimensional Euclidean position space. We initially perform one of the two integrations in the position space and then reduce the Lorentz structure to D-dimensional scalar single integrals. Some of the latter are then calculated by the uniqueness method, others by the Gegenbauer polynomial technique. The result is independent of the ultraviolet and the infrared scale. It is expressed in terms of the squares of spacetime intervals between points of the effective fields in the position space—it includes simple powers of these intervals, as well as logarithms and polylogarithms thereof, with some of the latter appearing within the Davydychev integral J(1, 1, 1). Concerning the rest of diagrams, we present the result for the contributions correponding to third, fourth and fifth diagrams without giving the details of calculation. The full result for the Lcc correlator of the effective action at the planar two-loop level is written explicitly for maximally supersymmetric Yang-Mills theory.

We study the near-flat space limit for strings on AdS₅ × M⁵, where the internal manifold M⁵ is equipped with a generic metric with U(1)³ isometry. In the bosonic sector, the limiting sigma model is similar to the one found for AdS₅ × S⁵, as the global symmetries are reduced in the most general case. When M⁵ is a Sasaki-Einstein space like T^1,1, Y^p,q and L^p,q,r, whose dual CFT's have = 1 supersymmetry, the near-flat space limit gives the same bosonic sector of the sigma model found for AdS₅ × S⁵. This indicates the generic presence of integrable subsectors in AdS/CFT.

We construct the Lagrangian of the = 1 four-dimensional generalized supersymmetric Nambu-Jona-Lasinio (SNJL) model, which has = 1/2 supersymmetry (SUSY) on non(anti)commutative superspace. A special attention is paid to the examination on the nonperturbative quantum dynamics: The phenomenon of dynamical-symmetry-breaking/mass-generation on the deformed superspace is investigated. The model Lagrangian and the method of SUSY auxiliary fields of composites are examined in terms of component fields. We derive the effective action, examine it, and solve the gap equation for self-consistent mass parameters.

A diagrammatic expansion of coefficients in the low-momentum expansion of the genus-one four-particle amplitude in type II superstring theory is developed. This is applied to determine coefficients up to order s⁶ R⁴ (where s is a Mandelstam invariant and R the linearized super-curvature), and partial results are obtained beyond that order. This involves integrating powers of the scalar propagator on a toroidal world-sheet, as well as integrating over the modulus of the torus. At any given order in s the coefficients of these terms are given by rational numbers multiplying multiple zeta values (or Euler-Zagier sums) that, up to the order studied here, reduce to products of Riemann zeta values. We are careful to disentangle the analytic pieces from logarithmic threshold terms, which involves a discussion of the conditions imposed by unitarity. We further consider the compactification of the amplitude on a circle of radius r, which results in a plethora of terms that are power-behaved in r. These coefficients provide boundary `data' that must be matched by any non-perturbative expression for the low-energy expansion of the four-graviton amplitude. The paper includes an appendix by Don Zagier.

This paper is a continuation arXiv:0707.1324 where improved holographic theories for QCD were set up and explored. Here, the IR confining geometries are classified and analyzed. They all end in a ``good" (repulsive) singularity in the IR. The glueball spectra are gapped and discrete, and they favorably compare to the lattice data. Quite generally, confinement and discrete spectra imply each other. Asymptotically linear glueball masses can also be achieved. Asymptotic mass ratios of various glueballs with different spin also turn out to be universal. Meson dynamics is implemented via space filling D₄−₄ brane pairs. The associated tachyon dynamics is analyzed and chiral symmetry breaking is shown. The dynamics of the RR axion is analyzed, and the non-perturbative running of the QCD θ-angle is obtained. It is shown to always vanish in the IR.

Presented are complete next-to-leading order electroweak (NLO EW) corrections to top-squark pair production at the Large Hadron Collider (LHC) within the Minimal Supersymmetric Standard Model (MSSM). At this order, also effects from the interference of EW and QCD contributions have to be taken into account. Moreover, photon-induced top-squark production is considered as an additional partonic channel, which arises from the non-zero photon density in the proton.

We analyze the conditions to have no-scale supersymmetry breaking solutions of type IIA and IIB supergravity compactified on manifolds of SU(3)-structure. The supersymmetry is spontaneously broken by the intrinsic torsion of the internal space. For type IIB orientifolds with O9 and O5-planes the mass of the gravitino is governed by the torsion class ₁, and the breaking is mediated through F-terms associated to descendants of the original = 2 hypermultiplets. For type IIA orientifolds with O6-planes we find two families of solutions, depending on whether the breaking is mediated exclusively by hypermultiplets or by a mixture of hypermultiplets and vector multiplets, the latter case corresponding to a class of Scherk-Schwarz compactifications not dual to any geometric IIB setup. We compute the geometrically induced μ-terms for D5, D6 and D9-branes on twisted tori, and discuss the patterns of soft-terms which arise for pure moduli mediation in each type of breaking. As for D3 and D7-branes in presence of 3-form fluxes, the effective scalar potential turns out to possess interesting phenomenological properties.

In this paper we investigate the properties of series of vacua in the string theory landscape. In particular, we study minima to the flux potential in type IIB compactifications on the mirror quintic. Using geometric transitions, we embed its one-dimensional complex structure moduli space in that of another Calabi-Yau with h^1,1 = 86 and h^2,1 = 2. We then show how to construct infinite series of continuously connected minima to the mirror quintic potential by moving into this larger moduli space, applying its monodromies, and moving back. We provide an example of such series, and discuss their implications for the string theory landscape.

Following Alday and Maldacena [1], we describe a string theory method to compute the strong coupling behavior of the scattering amplitudes of quarks and gluons in planar = 2 super Yang-Mills theory in the probe approximation. Explicit predictions for these quantities can be constructed using the all-orders planar gluon scattering amplitudes of = 4 super Yang-Mills due to Bern, Dixon and Smirnov [2].

We consider the application of endpoint techniques to the problem of mass determination for new particles produced at a hadron collider, where these particles decay to an invisible particle of unknown mass and one or more visible particles of known mass. We also consider decays of these types for pair-produced particles and in each case consider situations both with and without initial state radiation. We prove that, in most (but not all) cases, the endpoint of an appropriate transverse mass observable, considered as a function of the unknown mass of the invisible particle, has a kink at the true value of the invisible particle mass. The co-ordinates of the kink yield the masses of the decaying particle and the invisible particle. We discuss the prospects for implementing this method at the LHC.

We show a calculable example of stable supersymmetry (SUSY) breaking models with O(10) eV gravitino mass based on the combination of D-term gauge mediation and U(1)' mediation. A potential problem of the negative mass squared for the SUSY standard model (SSM) sfermions in the D-term gauge mediation is solved by the contribution from the U(1)' mediation. On the other hand, the splitting between the SSM gauginos and sfermions in the U(1)' mediation is circumvented by the contributions from the D-term gauge mediation. Since the U(1)' mediation does not introduce any new SUSY vacua, we achieve a completely stable model under thermal effects. Our model, therefore, has no cosmological difficulty.

We consider an open string version of the topological twist previously proposed for sigma-models with G₂ target spaces. We determine the cohomology of open strings states and relate these to geometric deformations of calibrated submanifolds and to flat or anti-self-dual connections on such submanifolds. On associative three-cycles we show that the worldvolume theory is a gauge-fixed Chern-Simons theory coupled to normal deformations of the cycle. For coassociative four-cycles we find a functional that extremizes on anti-self-dual gauge fields. A brane wrapping the whole G₂ induces a seven-dimensional associative Chern-Simons theory on the manifold. This theory has already been proposed by Donaldson and Thomas as the higher-dimensional generalization of real Chern-Simons theory. When the G₂ manifold has the structure of a Calabi-Yau times a circle, these theories reduce to a combination of the open A-model on special Lagrangians and the open -model on holomorphic submanifolds. We also comment on possible applications of our results.

Standard active-sterile neutrino oscillations do not provide a satisfactory description of the LSND evidence for neutrino oscillations together with the constraints from MiniBooNE and other null-result short-baseline oscillation experiments. However, if the mass or the mixing of the sterile neutrino depends in an exotic way on its energy all data become consistent. I explore the phenomenological consequences of the assumption that either the mass or the mixing scales with the neutrino energy as 1/E_ν^r (r > 0). Since the neutrino energy in LSND is about 40 MeV, whereas MiniBooNE operates at around 1 GeV, oscillations get suppressed in MiniBooNE and the two results become fully compatible for r ≳ 0.2. Furthermore, also the global fit of all relevant data improves significantly by exploring the different energy regimes of the various experiments. The best fit χ² decreases by 12.7 (14.1) units with respect to standard sterile neutrino oscillations if the mass (mixing) scales with energy.

The conditions for = 1 supersymmetry in type II supergravity have been previously reformulated in terms of generalized complex geometry. We improve that reformulation so as to completely eliminate the remaining explicit dependence on the metric. Doing so involves a natural generalization of the Dolbeault operator. As an application, we present some general arguments about supersymmetric moduli. In particular, a subset of them are then classified by a certain cohomology. We also argue that the Dolbeault reformulation should make it easier to find existence theorems for the = 1 equations.

We apply the dressing method to a string solution given by a static string wrapped around the equator of a three-sphere and find that the result is the single spike solution recently discussed in the literature. Further application of the method allows the construction of solutions with multiple spikes. In particular we construct the solution describing the scattering of two single spikes and compute the scattering phase shift. As a function of the dressing parameters, the result is exactly the same as the one for the giant magnon, up to non-logarithmic terms. This suggests that the single spikes should be described by an integrable spin chain closely related to the one associated to the giant magnons. The field theory interpretation of such spin chain however is still unclear.

Differential equations of infinite order are an increasingly important class of equations in theoretical physics. Such equations are ubiquitous in string field theory and have recently attracted considerable interest also from cosmologists. Though these equations have been studied in the classical mathematical literature, it appears that the physics community is largely unaware of the relevant formalism. Of particular importance is the fate of the initial value problem. Under what circumstances do infinite order differential equations possess a well-defined initial value problem and how many initial data are required? In this paper we study the initial value problem for infinite order differential equations in the mathematical framework of the formal operator calculus, with analytic initial data. This formalism allows us to handle simultaneously a wide array of different nonlocal equations within a single framework and also admits a transparent physical interpretation. We show that differential equations of infinite order do not generically admit infinitely many initial data. Rather, each pole of the propagator contributes two initial data to the final solution. Though it is possible to find differential equations of infinite order which admit well-defined initial value problem with only two initial data, neither the dynamical equations of p-adic string theory nor string field theory seem to belong to this class. However, both theories can be rendered ghost-free by suitable definition of the action of the formal pseudo-differential operator. This prescription restricts the theory to frequencies within some contour in the complex plane and hence may be thought of as a sort of ultra-violet cut-off. Our results place certain recent attempts to study inflation in the context of nonlocal field theories on a much firmer mathematical footing.

We demonstrate complete integrability of the Nambu-Goto equations for a stationary string in the general Kerr-NUT-(A)dS spacetime describing the higher-dimensional rotating black hole. The stationary string in D dimensions is generated by a 1-parameter family of Killing trajectories and the problem of finding a string configuration reduces to a problem of finding a geodesic line in an effective (D−1)-dimensional space. Resulting integrability of this geodesic problem is connected with the existence of hidden symmetries which are inherited from the black hole background. In a spacetime with p mutually commuting Killing vectors it is possible to introduce a concept of a ξ-brane, that is a p-brane with the worldvolume generated by these fields and a 1-dimensional curve. We discuss integrability of such ξ-branes in the Kerr-NUT-(A)dS spacetime.

We construct probe solutions in the attractor background of the five-dimensional D1-D5-P black hole which represent near-horizon microstates in the limit of large D1-charge. These generalize the corresponding solutions considered by Gaiotto, Strominger and Yin for the 4-dimensional D0-D4 black hole. Using U-duality and a 4D-5D connection, we argue that the relevant configurations are bound states of D1-branes that have expanded through the Myers effect to form a Kaluza-Klein monopole wrapping the black hole horizon. We show that these branes experience a magnetic field on their moduli space, and that the degeneracy of lowest Landau levels reproduces the Bekenstein-Hawking entropy.

We discuss flavor-mixing probabilities and flavor ratios of high energy astrophysical neutrinos. In the first part of this paper, we expand the neutrino flavor-fluxes in terms of the small parameters U_e3 and π/4−θ₂₃, and show that there are universal first and second order corrections. The second order term can exceed the first order term, and so should be included in any analytic study. We also investigate the probabilities and ratios after a further expansion around the tribimaximal value of sin²θ₁₂ = 1/3. In the second part of the paper, we discuss implications of deviations of initial flavor ratios from the usually assumed, idealized flavor compositions for pion, muon-damped, and neutron beam sources, viz., (ν_e : ν_μ : ν_τ) = (1 : 2 : 0), (0 : 1 : 0), and (1 : 0 : 0), respectively. We show that even small deviations have significant consequences for the observed flavor ratios at Earth. If initial flavor deviations are not taken into account in analyses, then false inferences for the values in the PMNS matrix elements (angles and phase) may result.

This paper is a companion to our earlier work [1] in which the projective superspace formulation for matter-coupled simple supergravity in five dimensions was presented. For the minimal multiplet of 5D = 1 supergravity introduced by Howe in 1981, we give a complete solution of the Bianchi identities. The geometry of curved superspace is shown to allow the existence of a large family of off-shell supermultiplets that can be used to describe supersymmetric matter, including vector multiplets and hypermultiplets. We formulate a manifestly locally supersymmetric action principle. Its natural property turns out to be the invariance under so-called projective transformations of the auxiliary isotwistor variables. We then demonstrate that the projective invariance allows one to uniquely restore the action functional in a Wess-Zumino gauge. The latter action is well-suited for reducing the supergravity-matter systems to components.

We discuss the chiral symmetry breaking in general intersecting Dq/Dp brane models consisting of N_c Dq-branes and a single Dp-brane with an s-dimensional intersection. There exists a QCD-like theory localized at the intersection and the Dq/Dp model gives a holographic description of it. The rotational symmetry of directions transverse to both of the Dq and Dp-branes can be identified with a chiral symmetry, which is non-Abelian for certain cases. The asymptotic distance between the Dq-branes and the Dp-brane corresponds to a quark mass. By studying the probe Dp-brane dynamics in a Dq-brane background in the near horizon and large N_c limit we find that the chiral symmetry is spontaneously broken and there appear (pseudo-)Nambu-Goldstone bosons. We also discuss the models at finite temperature.

We construct a basis set of infra-red and/or collinearly divergent scalar one-loop integrals and give analytic formulas, for tadpole, bubble, triangle and box integrals, regulating the divergences (ultra-violet, infra-red or collinear) by regularization in D = 4−2 dimensions. For scalar triangle integrals we give results for our basis set containing 6 divergent integrals. For scalar box integrals we give results for our basis set containing 16 divergent integrals. We provide analytic results for the 5 divergent box integrals in the basis set which are missing in the literature. Building on the work of van Oldenborgh, a general, publicly available code has been constructed, which calculates both finite and divergent one-loop integrals. The code returns the coefficients of 1/²,1/¹ and 1/⁰ as complex numbers for an arbitrary tadpole, bubble, triangle or box integral.

We investigate the perturbative (in g_sN_D8) backreaction of localized D8 branes in D4-D8 systems including in particular the Sakai Sugimoto model. We write down the explicit expressions of the backreacted metric, dilaton and RR form. We find that the backreaction remains small up to a radial value of u << ℓ_s/(g_sN_D8), and that the background functions are smooth except at the D8 sources. In this perturbative window, the original embedding remains a solution to the equations of motion. Furthermore, the fluctuations around the original embedding, describing scalar mesons, do not become tachyonic due to the backreaction in the perturbative regime. This is is due to a cancelation between the DBI and CS parts of the D8 brane action in the perturbed background.