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Keywords = superstring cosmology

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12 pages, 794 KB  
Article
Weak Scale Supersymmetry Emergent from the String Landscape
by Howard Baer, Vernon Barger, Dakotah Martinez and Shadman Salam
Entropy 2024, 26(3), 275; https://doi.org/10.3390/e26030275 - 21 Mar 2024
Cited by 2 | Viewed by 1872
Abstract
Superstring flux compactifications can stabilize all moduli while leading to an enormous number of vacua solutions, each leading to different 4d laws of physics. While the string landscape provides at present the only plausible explanation for the size of the cosmological [...] Read more.
Superstring flux compactifications can stabilize all moduli while leading to an enormous number of vacua solutions, each leading to different 4d laws of physics. While the string landscape provides at present the only plausible explanation for the size of the cosmological constant, it may also predict the form of weak scale supersymmetry which is expected to emerge. Rather general arguments suggest a power-law draw to large soft terms, but these are subject to an anthropic selection of a not-too-large value for the weak scale. The combined selection allows one to compute relative probabilities for the emergence of supersymmetric models from the landscape. Models with weak scale naturalness appear most likely to emerge since they have the largest parameter space on the landscape. For finetuned models such as high-scale SUSY or split SUSY, the required weak scale finetuning shrinks their parameter space to tiny volumes, making them much less likely to appear compared to natural models. Probability distributions for sparticle and Higgs masses from natural models show a preference for Higgs mass mh125 GeV, with sparticles typically beyond the present LHC limits, in accord with data. From these considerations, we briefly describe how natural SUSY is expected to be revealed at future LHC upgrades. This article is a contribution to the Special Edition of the journal Entropy, honoring Paul Frampton on his 80th birthday. Full article
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10 pages, 427 KB  
Article
BFSS Matrix Model Cosmology: Progress and Challenges
by Suddhasattwa Brahma, Robert Brandenberger and Samuel Laliberte
Physics 2023, 5(1), 1-10; https://doi.org/10.3390/physics5010001 - 22 Dec 2022
Cited by 19 | Viewed by 3673
Abstract
We review a proposal to obtain an emergent metric space-time and an emergent early universe cosmology from the Banks–Fischler–Shenker–Susskind (BFSS) matrix model. Some challenges and directions for future research are outlined. Full article
(This article belongs to the Special Issue New Advances in Quantum Geometry)
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6 pages, 246 KB  
Communication
Starobinsky–Bel–Robinson Gravity
by Sergei V. Ketov
Universe 2022, 8(7), 351; https://doi.org/10.3390/universe8070351 - 24 Jun 2022
Cited by 33 | Viewed by 1671
Abstract
A novel string-inspired gravitational theory in four spacetime dimensions is proposed as a sum of the modified (R+αR2) gravity motivated by the Starobinsky inflation and the leading Bel–Robinson-tensor-squared correction to the gravitational effective action of superstrings/M-theory compactified [...] Read more.
A novel string-inspired gravitational theory in four spacetime dimensions is proposed as a sum of the modified (R+αR2) gravity motivated by the Starobinsky inflation and the leading Bel–Robinson-tensor-squared correction to the gravitational effective action of superstrings/M-theory compactified down to four dimensions. The possible origin of the theory from higher dimensions is revealed. The proposed Starobinsky–Bel–Robinson action has only two free parameters, which makes it suitable for verifiable physical applications in black hole physics, cosmological inflation and Hawking radiation. Full article
(This article belongs to the Section Gravitation)
19 pages, 316 KB  
Review
Conformal Relativity versus Brans–Dicke and Superstring Theories
by David B. Blaschke and Mariusz P. Dąbrowski
Entropy 2012, 14(10), 1978-1996; https://doi.org/10.3390/e14101978 - 18 Oct 2012
Cited by 9 | Viewed by 6832
Abstract
We show how conformal relativity is related to Brans–Dicke theory and to low-energy-effective superstring theory. Conformal relativity or the Hoyle–Narlikar theory is invariant with respect to conformal transformations of the metric. We show that the conformal relativity action is equivalent to the transformed [...] Read more.
We show how conformal relativity is related to Brans–Dicke theory and to low-energy-effective superstring theory. Conformal relativity or the Hoyle–Narlikar theory is invariant with respect to conformal transformations of the metric. We show that the conformal relativity action is equivalent to the transformed Brans–Dicke action for ω = -3/2 (which is the border between standard scalar field and ghost) in contrast to the reduced (graviton-dilaton) low-energy-effective superstring action which corresponds to the Brans–Dicke action with ω = -1. We show that like in ekpyrotic/cyclic models, the transition through the singularity in conformal cosmology in the string frame takes place in the weak coupling regime. We also find interesting self-duality and duality relations for the graviton-dilaton actions. Full article
(This article belongs to the Special Issue Modified Gravity: From Black Holes Entropy to Current Cosmology)
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