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SUMMARY:Inhomogeneous Cosmological Bounce in Cubic Horndeski Theory
DTSTART;VALUE=DATE-TIME:20261029T145500Z
DTEND;VALUE=DATE-TIME:20261029T151000Z
DTSTAMP;VALUE=DATE-TIME:20261019T191005Z
UID:indico-contribution-6257@cern.ch
DESCRIPTION:Speakers: Marina Bakhlova (M.V. Lomonosov Moscow State Univers
 ity)\nThis work investigates the physical stability of cosmological bounce
  scenarios. As a starting point\, we consider a previously proposed bounce
  solution for a homogeneous and isotropic background within a subclass of 
 Horndeski theory. In this model\, the scalar perturbation mode is non-dyna
 mical ("frozen")\, which allows the system to formally evade standard no-g
 o theorems limiting the construction of stable bounces.\n\nIn this paper\,
  we investigate the stability of this solution against small spatial inhom
 ogeneities. To this end\, we introduce a spherically symmetric dynamical m
 etric and a scalar field with small inhomogeneous perturbations. Based on 
 the derived equations of motion\, we verify the stability conditions (i.e.
 \, the absence of ghosts and gradient instabilities) using a newly formula
 ted no-go theorem extended to inhomogeneous dynamical metrics.\n\nOur nume
 rical analysis demonstrates that introducing even arbitrarily small spatia
 l inhomogeneities leads to the violation of these stability conditions. We
  show that the scalar mode\, which remains stable and "frozen" in the stri
 ctly homogeneous case\, acquires dynamics upon deformation of the bounce\,
  inevitably triggering the development of instabilities. Consequently\, th
 e mechanism for evading the no-go theorem in a homogeneous background prov
 es to be unstable against spatial fluctuations.\n\nhttps://indico.particle
 .mephi.ru/event/626/contributions/6257/
LOCATION:Sevastopol Hotel
URL:https://indico.particle.mephi.ru/event/626/contributions/6257/
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