CERN Accelerating science

Article
Report number	arXiv:0908.0004 ; CERN-PH-TH-2009-142 ; CERN-PH-TH-2009-142
Title	The gravitational S-matrix
Author(s)	Giddings, Steven B. (UC, Santa Barbara ; CERN) ; Porto, Rafael A. (UC, Santa Barbara ; CERN)
Publication	2010
Imprint	04 Aug 2009
Number of pages	46 p, 46
Note	Comments: 46 pages, 10 figures
In:	Phys. Rev. D 81 (2010) 025002
DOI	10.1103/PhysRevD.81.025002
Subject category	Particle Physics - Theory
Abstract	We investigate the hypothesized existence of an S-matrix for gravity, and some of its expected general properties. We first discuss basic questions regarding existence of such a matrix, including those of infrared divergences and description of asymptotic states. Distinct scattering behavior occurs in the Born, eikonal, and strong gravity regimes, and we describe aspects of both the partial wave and momentum space amplitudes, and their analytic properties, from these regimes. Classically the strong gravity region would be dominated by formation of black holes, and we assume its unitary quantum dynamics is described by corresponding resonances. Masslessness limits some powerful methods and results that apply to massive theories, though a continuation path implying crossing symmetry plausibly still exists. Physical properties of gravity suggest nonpolynomial amplitudes, although crossing and causality constrain (with modest assumptions) this nonpolynomial behavior, particularly requiring a polynomial bound in complex s at fixed physical momentum transfer. We explore the hypothesis that such behavior corresponds to a nonlocality intrinsic to gravity, but consistent with unitarity, analyticity, crossing, and causality.

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