arXiv subjects

S. D. Odintsov

Publications and source records attributed to S. D. Odintsov.

At least 253 records · Page 14Linked to original sources

arXiv1995

On Black Holes in the Theory of Dilatonic Gravity Coupled to a Scalar Field

Taking advantage of the representation of dilatonic gravity with the $R^2$-term under the form of low-derivative dilatonic gravity coupled to an additional scalar, we construct a general renormalizable model motivated by this theory. Exact black hole solutions are found for some special versions of the model, and their thermodynamical properties are described in detail. In particular, their horizons and temperatures are calculated. Finally, the corresponding one-loop effective action is obtained in the conformal gauge, and a number of its properties -including the construction of one-loop finite models-are briefly described.

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arXiv1995

General dilatonic gravity with an asymptotically free gravitational coupling constant near two dimensions

We study a renormalizable, general theory of dilatonic gravity (with a kinetic-like term for the dilaton) interacting with scalar matter near two dimensions. The one-loop effective action and the beta functions for this general theory are written down. It is proven that the theory possesses a non-trivial ultraviolet fixed point which yields an asymptotically free gravitational coupling constant (at $ε\rightarrow 0$) in this regime. Moreover, at the fixed point the theory can be cast under the form of a string-inspired model with free scalar matter. The renormalization of the Jackiw-Teitelboim model and of lineal gravity in $2+ε$ dimensions is also discussed. We show that these two theories are distinguished at the quantum level. Finally, fermion-dilatonic gravity near two dimensions is considered.

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arXiv1995

GUTs in Curved Spacetime: Running Gravitational Constants, Newtonian Potential and the Quantum Corrected Gravitational Equations

The running coupling constants (in particular, the gravitational one) are studied in asymptotically free GUTs and in finite GUTs in curved spacetime, with explicit examples. The running gravitational coupling is used to calculate the leading quantum GUT corrections to the Newtonian potential, which turn out to be of logarithmic form in asymptotically free GUTs. A comparison with the effective theory for the conformal factor ---where leading quantum corrections to the Newtonian potential are again logarithmic--- is made. A totally asymptotically free $O(N)$ GUT with quantum higher derivative gravity is then constructed, using the technique of introducing renormalization group (RG) potentials in the space of couplings. RG equations for the cosmological and gravitational couplings in this theory are derived, and solved numerically, showing the influence of higher-derivative quantum gravity on the Newtonian potential. The RG-improved effective gravitational Lagrangian for asymptotically free massive GUTs is calculated in the strong (almost constant) curvature regime, and the non-singular De Sitter solution to the quantum corrected gravitational equations is subsequently discussed. Finally, possible extensions of the results here obtained are briefly outlined.

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arXiv1995

HIGH TEMPERATURE EXPANSION OF STRING FREE ENERGY IN HYPERBOLIC SPACE

The high temperature behaviour of the open bosonic string free energy in the space $S^1 \otimes H^N$ with vanishingly small curvature is investigated. The leading term of the high temperature expansion of the one-loop free energy, near the Hagedorn instability, is obtained. The problem of infrared regularization of thermodynamical quantities is pointed out. For minimally coupling quantum fields related to the normal modes of strings, the results are similar to the ones valid for Rindler space. In the lower mass string states regime a connection with the quantum corrections to the black hole entropy is outlined.

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arXiv1995

THE HIGGS-YUKAWA MODEL IN CURVED SPACETIME

The Higgs-Yukawa model in curved spacetime (renormalizable in the usual sense) is considered near the critical point, employing the $1/N$--expansion and renormalization group techniques. By making use of the equivalence of this model with the standard NJL model, the effective potential in the linear curvature approach is calculated and the dynamically generated fermionic mass is found. A numerical study of chiral symmetry breaking by curvature effects is presented.

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arXiv1995

DILATONIC GRAVITY NEAR TWO DIMENSIONS AND ASYMPTOTIC FREEDOM OF THE GRAVITATIONAL COUPLING CONSTANT

Two models of dilatonic gravity are investigated: (i) dilaton-Yang-Mills gravity and (ii) higher-derivative dilatonic gravity. Both are renormalizable in $2+ε$ dimensions and have a smooth limit for $ε\rightarrow 0$. The corresponding one-loop effective actions and beta-functions are found. Both theories are shown to possess a non-trivial ultraviolet fixed point ---for all dilatonic couplings--- in which the gravitational constant is asymptotically free. It is shown that in the regime of asymptotic freedom the matter central charge can be significantly increased by two different mechanisms ---as compared with pure dilatonic gravity, where $n < 24$.

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arXiv1995

Dilaton-Maxwell gravity with matter near two dimensions

Unlike Einstein gravity, dilaton-Maxwell gravity with matter is renormalizable in $2+ε$ dimensions and has a smooth $ε\to 0$ limit.By performing a renormalization- group study of this last theory we show that the gravitational coupling constant $G$ has a non-trivial,ultraviolet stable fixed point (asymptotic freedom) and that the dilatonic coupling functions (including the dilatonic potential) exhibit also a real, non-trivial fixed point. At such point the theory represents a standard charged string-inspired model.Stability and the gauge dependence of the fixed-point solution is discussed.It is shown that all these properties remain valid in a dilatonic-Yang-Mills theory with $n$ scalars and $m$ spinors, that has the UF stable fixed point $G^* = 3ε(48+12N-m-2n)^{-1}$.In addition, it is seen that by increasing $N$ (number of gauge fields) the matter central charge $C=n+m/2$ ($0<C<24+6N$) can be increased correspondingly (in pure dilatonic gravity $0<C<24$).

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arXiv1994

A Four-Dimensional Theory for Quantum Gravity with Conformal and Nonconformal Explicit Solutions

The most general version of a renormalizable $d=4$ theory corresponding to a dimensionless higher-derivative scalar field model in curved spacetime is explored. The classical action of the theory contains $12$ independent functions, which are the generalized coupling constants of the theory. We calculate the one-loop beta functions and then consider the conditions for finiteness. The set of exact solutions of power type is proven to consist of precisely three conformal and three nonconformal solutions, given by remarkably simple (albeit nontrivial) functions that we obtain explicitly. The finiteness of the conformal theory indicates the absence of a conformal anomaly in the finite sector. The stability of the finite solutions is investigated and the possibility of renormalization group flows is discussed as well as several physical applications.

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arXiv1994

Higher Derivative Four-Fermion Model in Curved Spacetime

We discuss the phase structure of a higher derivative four-fermion model in four dimensions in curved spacetime in frames of the $\frac{1}{N_c}$-expansion. First, we evaluate in our model the effective potential of two composite scalars in the linear curvature approximation using a local momentum representation in curved spacetime for the higher-derivative propagator which naturally appears. The symmetry breaking phenomenon and phase transition induced by curvature are numerically investigated. A numerical study of the dynamically generated fermionic mass, which depends on the coupling constants and on the curvature, is also presented.

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arXiv1994

Non-Critical Bosonic String Corrections to the Black Hole Entropy

We calculate the quantum corrections to the entropy of a very large black hole, coming from the theory of a $D$-dimensional, non-critical bosonic string. We show that, for $D >2$, as a result of modular invariance the entropy is ultraviolet finite, although it diverges in the infrared (while for $D=2$ the entropy contains both ultraviolet and infrared divergences). The issue of modular invariance in field theory, in connection with black-hole entropy, is also investigated.

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arXiv1994

Renormalization group and logarithmic corrections to scaling relations in conformal sector of 4D gravity

We study the effective theory of the conformal factor near its infrared stable fixed point.The renormalization group equations for the effective coupling constants are found and their solutions near the critical point are obtained, providing the logarithmic corrections to scaling relations.Some cosmological applications of the running of coupling constants are briefly discussed.

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arXiv1994

The Effective Action in Gauged Supergravity on Hyperbolic Background and Induced Cosmological Constant

The one-loop effective action for 4-dimensional gauged supergravity with negative cosmological constant, is investigated in space-times with compact hyperbolic spatial section. The explicit expansion of the effective action as a power series of the curvature on hyperbolic background is derived, making use of heat-kernel and zeta-regularization techniques. The induced cosmological and Newton constants are computed.

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arXiv1994

Conformal Factor Dynamics in the 1/N Expansion

We suggest to consider conformal factor dynamics as applying to composite boundstates, in frames of the $1/N$ expansion. In this way, a new model of effective theory for quantum gravity is obtained. The renormalization group (RG) analysis of this model provides a framework to solve the cosmological constant problem, since the value of this constant turns out to be suppressed, as a result of the RG contributions. The effective potential for the conformal factor is found too.

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arXiv1994

Schwinger-Dyson Equations in 2D Induced Gravity in Covariant Gauges

We formulate the Schwinger-Dyson equations in the ladder approximation for 2D induced quantum gravity with fermions using covariant gauges of harmonic type. It is shown that these equations can be formulated consistently in a gauge of Landau type (for negative cosmological constant). A numerical analysis of the equations hints towards the possibility of chiral symmetry breaking, depending on the value of the coupling constant.

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arXiv1994

A Theory for the Conformal Factor in Quantum $R^2$ Gravity

A new theory for the conformal factor in R$^2$-gravity is developed. The infrared phase of this theory, which follows from the one-loop renormalization group equations for the whole quantum R$^2$-gravity theory is described. The one-loop effective potential for the conformal factor is found explicitly and a mechanism for inducing Einstein gravity at the minimum of the effective potential for the conformal factor is suggested. A comparison with the effective theory of the conformal factor induced by the conformal anomaly, and also aiming to describe quantum gravity at large distances, is done.

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arXiv1994

Asymptotic Regimes in Quantum Gravity at Large Distances and Running Newtonian and Cosmological Constants

We consider a multiplicatively renormalizable higher-derivative scalar theory which is used as an effective theory for quantum gravity at large distances (infrared phase of quantum gravity). The asymptotic regimes (in particular, the asymptotically free infrared regime) for the coupling constants ---specifically the Newtonian and the cosmological constant--- are obtained. The running of the Newton and cosmological constants in the infrared asymptotically free regime may be relevant for solving the cosmological constant problem and for estimating the leading-log corrections to the static gravitational potential.

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arXiv1994

Asymptotic Level State Density for Parabosonic Strings

Making use of some results concerning the theory of partitions, relevant in number theory, the complete asymptotic behavior, for large $n$, of the level density of states for a parabosonic string is derived. It is also pointed out the similarity between parabosonic strings and membranes.

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arXiv1994

Renormalization-Group Improved Effective Potential for Finite Grand Unified Theories in Curved Spacetime

The renormalization-group improved effective potential ---to leading-log and in the linear curvature approximation--- is constructed for ``finite'' theories in curved spacetime. It is not trivial and displays a quite interesting, exponential-like structure ---in contrast with the case of flat spacetime where it coincides with the classical potential. Several possible cosmological applications, as curvature-induced phase transitions and modifications of the values of the gravitational and cosmological constants, are briefly discussed.

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