Zobrazeno 1 - 10
of 430
pro vyhledávání: '"Rubakov, V. A."'
We consider the issue of stability at the linearized level for static, spherically symmetric wormhole solutions within a subclass of scalar-tensor theories of beyond Horndeski type. In this class of theories we derive a set of stability conditions en
Externí odkaz:
http://arxiv.org/abs/2212.05969
Autor:
Rubakov, V. A., Wetterich, C.
The geometric concept of geodesic completeness depends on the choice of the metric field or "metric frame". We develop a frame-invariant concept of "generalised geodesic completeness" or "time completeness". It is based on the notion of physical time
Externí odkaz:
http://arxiv.org/abs/2210.11198
Publikováno v:
JHEP 01 (2023) 026
We construct a concrete model of Horndeski bounce with strong gravity in the past. Within this model we show that the correct spectra of cosmological perturbations may be generated at early contracting epoch, with mild fine-tuning ensuring that the s
Externí odkaz:
http://arxiv.org/abs/2207.04071
Publikováno v:
Phys. Rev. D 104, 063530 (2021)
In scalar-tensor Horndeski theories, nonsingular cosmological models - bounce and genesis - are problematic because of potential ghost and/or gradient instabilities. One way to get around this obstacle is to send the effective Planck mass to zero in
Externí odkaz:
http://arxiv.org/abs/2104.13412
We consider DHOST Ia theory interacting gravitationally with an additional conventional scalar field minimally coupled to gravity. At the linearized level of perturbations about cosmological background, we find that in the presence of a slowly rollin
Externí odkaz:
http://arxiv.org/abs/2011.14912
Genesis within the Horndeski theory is one of possible scenarios for the start of the Universe. In this model, the absence of instabilities is obtained at the expense of the property that coefficients, serving as effective Planck masses, vanish in th
Externí odkaz:
http://arxiv.org/abs/2009.05071
We study the superluminality issue in beyond Horndeski theory with additional scalar field, which is minimally coupled to gravity and has no second derivatives in the Lagrangian. We present the quadratic action for perturbations in cosmological backg
Externí odkaz:
http://arxiv.org/abs/2005.12626
Publikováno v:
Phys. Rev. D 102, 023519 (2020)
It is of interest to understand whether or not one can construct a classical field theory description of early cosmology which would be free of the initial singularity and stable throughout the whole evolution. One of the known possibilities is genes
Externí odkaz:
http://arxiv.org/abs/2003.01202
Autor:
Rubakov, V. A.
Cosmology and astroparticle physics give strongest possible evidence for the incompleteness of the Standard Model of particle physics. Leaving aside misterious dark energy, which may or may not be just the cosmological constant, two properties of the
Externí odkaz:
http://arxiv.org/abs/1912.04727