S. O. Alexeyev

Black hole solutions with dilatonic hair in higher curvature gravity

A new numerical integration method for examining a black hole structure was realized. Black hole solutions with dilatonic hair of 4D low energy effective SuperString Theory action with Gauss-Bonnet quadratic curvature contribution were studied, using this method, inside and outside the event horizon. Thermodynamical properties of this solution were also studied.

Gauss-Bonnet black holes at the LHC: Beyond the dimensionality of space

Abstract The Gauss–Bonnet invariant is one of the most promising candidates for a quadratic curvature correction to the Einstein action in expansions of supersymmetric string theory. We study the evaporation of such Schwarzschild–Gauss–Bonnet black holes which could be formed at future colliders if the Planck scale is of order of TeV, as predicted by some modern brane world models. We show that, beyond the dimensionality of space, the corresponding coupling constant could be measured by the LHC. This opens new windows for physics investigation in spite of the possible screening of microphysics due to the event horizon.

Black-hole relics in string gravity: last stages of Hawking evaporation

The endpoint of black-hole evaporation is a very intriguing problem of modern physics. Based on the Einstein-dilaton-Gauss–Bonnet four-dimensional string gravity model, we show that black holes do not disappear and should become relics at the end of the evaporation process. The possibility of experimental detection of such remnant black holes is investigated. If they really exist, these objects could form a considerable part of the non-baryonic dark matter in our universe.

The nature of singularity in Bianchi I cosmological string gravity model with second order curvature corrections

Abstract We investigate Bianchi I cosmological model in the theory of a dilaton field coupled to gravity through a Gauss–Bonnet term. Two type of cosmological singularity are distinguished. The former is analogous to the Einstein gravity singularity, the latter (which does not appear in classical General Relativity) occurs when the main determinant of the system of field equations vanishes. An analogy between the latter cosmological singularity and the singularity inside a black hole with a dilatonic hair is discussed. Initial conditions, leading to these two types of cosmological singularity are found via numerical integration of the equation of motion.We investigate Bianchi I cosmological model in the theory of a dilatonM field coupled to gravity through a Gauss-Bonnet term. Two type ofM cosmological singularity are distinguished. The former is analogous toM the Einstein gravity singularity, the latter (which does not appear inM classical General Relativity) occurs when the main determinant of theM system of field equations vanishes. An analogy between the latterM cosmological singularity and the singularity inside a black hole withM a dilatonic hair is discussed. Initial conditions, leading to theseM two types of cosmological singularity are found via numericalM integration of the equation of motion.

Non-singular cosmological models in string gravity with constant dilaton and second-order curvature corrections

We investigate FRW cosmological solutions in the theory of a modulus field coupled to gravity through a Gauss-Bonnet term. The explicit analytical forms of non-singular asymptotics are presented for power-law and exponentially steep modulus coupling functions. We study the influence of a modulus field potential on these asymptotic regimes and find some forms of the potential which do not destroy the non-singular behaviour. In particular, we obtain that exponentially steep coupling functions arising from the string theory do not allow non-singular past asymptotic unless the modulus field potential tends to zero for a modulus field ψ→±∞. Finally, the modification of the chaotic dynamics in the closed FRW universe due to presence of the Gauss-Bonnet term is discussed.We investigate FRW cosmological solutions in the theory of modulus field coupled to gravity through a Gauss-Bonnet term. The explicit analytical forms of nonsingular asymptotics are presented for power-law and exponentially steep modulus coupling functions. We study the influence of modulus field potential on these asymptotical regimes and find some forms of the potential which do not destroy the nonsingular behavior. In particular, we obtain that exponentially steep coupling functions arising from the string theory do not allow nonsingular past asymptotic unless modulus field potential tends to zero for modulus field

Wormholes and naked singularities in Brans–Dicke cosmology

\psi \to \pm \infty

Kerr-Gauss-Bonnet black holes: Exact analytical solution

. Finally, the modification of the chaotic dynamics in the closed FRW universe due to presence of the Gauss-Bonnet term is discussed.

Non-singular Brans-Dicke cosmology with cosmological constant

We perform analytical and numerical study of static spherically symmetric solutions in the context of Brans-Dicke-like cosmological model by Elizalde et al. with an exponential potential. In this model the phantom regime arises without the appearance of any ghost degree of freedom due to the specific form of coupling. For the certain parameter ranges the model contains a regular solution which we interpret as a wormhole in an otherwise dS Universe. We put several bounds on the parameter values:

BLACK HOLES OF A MINIMAL SIZE IN STRING GRAVITY

\omega<0 ,\,\, \alpha^2/|\omega|<10^{-5},22.7\lesssim\!\phi_0\!\lesssim25\,

Four-Dimensional Dilatonic Black Holes in Gauss-Bonnet Extended String Gravity

. The numerical solution could mimic the Schwarzschild one, so the original model is consistent with astrophysical and cosmological observational data. However differences between our solution and the Schwarzschild one can be quite large, so black hole candidate observations could probably place further limits on the