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Report number	arXiv:1701.06629 ; IPPP-17-6 ; CERN-TH-2017-015
Title	Exponential suppression of the cosmological constant in nonsupersymmetric string vacua at two loops and beyond
Related title	On exponential suppression of the cosmological constant in non-SUSY strings at two loops and beyond
Author(s)	Abel, Steven (Durham U., IPPP ; Durham U., Dept. of Math.) ; Stewart, Richard J. (CERN)
Publication	2017-11-17
Imprint	2017-01-23
Number of pages	18
Note	41 pages, 5 figures, version accepted for publication
In:	Phys. Rev. D 96 (2017) 106013
DOI	10.1103/PhysRevD.96.106013
Subject category	hep-ph ; Particle Physics - Phenomenology ; hep-th ; Particle Physics - Theory
Abstract	Two independent criteria are presented that together guarantee exponential suppression of the two-loop cosmological constant in non-supersymmetric heterotic strings. They are derived by performing calculations in both the full string theory and in its underlying effective field theory, and come respectively from contributions that involve only physical untwisted states, and contributions that include orbifold twisted states. The criteria depend purely on the spectrum and charges, so a model that satisfies them will do so with no fine-tuning. An additional consistency condition (emerging from the so-called separating degeneration limit of the two-loop diagram) is that the one-loop cosmological constant must also be suppressed, by Bose-Fermi degeneracy in the massless spectrum. We remark that theories of this kind, that have continued exponential suppression to higher orders, can form the basis for a string implementation of the "naturalness without supersymmetry" idea.
Copyright/License	arXiv nonexclusive-distrib. 1.0 publication: © 2017-2025 authors (License: CC-BY-4.0) preprint: © 2017-2025 CERN (License: CC-BY-4.0)

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