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S. Mignemi

Publications and source records attributed to S. Mignemi.

At least 91 records · Page 5Linked to original sources
arXiv2002

Quantum dilaton gravity as a linear dilaton conformal field theory

A model of matter-coupled gravity in two dimensions is quantized. The crucial requirement for performing the quantization is the vanishing of the conformal anomaly, which is achieved by tuning a parameter in the interaction potential. The spectrum of the theory is determined by mapping the model first onto a field theory with a Liouville interaction, then onto a linear dilaton conformal field theory. In absence of matter fields a pure gauge theory with massless ground state is found; otherwise it is possible to minimally couple up to 11 matter scalar fields: in this case the ground state is tachyonic and the matter sector decouples, like the transverse oscillators in the critical bosonic string.

hep-th↗
arXiv2002

The Cardy-Verlinde formula for 2D gravity

We discuss the different bounds on entropy in the context of two-dimensional cosmology. We show that in order to obtain well definite bounds one has to use the scale symmetry of the gravitational theory. We then extend the recently found relation between the Friedmann equation and the Cardy formula to the case of two dimensions. In particular, we find that in two dimensions this relation requires that the central charge c of the conformal field theory is given in terms of the Newton constant G of the gravitational theory by c=6/G.

hep-th↗
arXiv2001

Conformal Dynamics of 0-Branes

We investigate the dynamics of dilatonic D-dimensional 0-branes in the near-horizon regime. The theory is given in a twofold form: two-dimensional dilaton gravity and nonlinear sigma model. Using asymptotic symmetries, duality relations, and sigma model techniques we find that the theory has three conformal points which correspond to (a) the asymptotic (Anti-de Sitter) region of the two-dimensional spacetime, (b) the horizon of the black hole, and (c) the infinite limit of the coupling parameter. We show that the conformal symmetry is perturbatively preserved at one-loop, identify the corresponding conformal field theories, and calculate the associated central charges. Finally, we use the conformal field theories to explain the thermodynamical properties of the two-dimensional black holes.

hep-th↗
arXiv2001

AdS_2 Gravity as Conformally Invariant Mechanical System

We show that two-dimensional (2D) AdS gravity induces on the spacetime boundary a conformally invariant dynamics that can be described in terms of a de Alfaro-Fubini-Furlan model coupled to an external source with conformal dimension two. The external source encodes the information about the gauge symmetries of the 2D gravity system. Alternatively, there exists a description in terms of a mechanical system with anholonomic constraints. The considered systems are invariant under the action of the conformal group generated by a Virasoro algebra, which occurs also as asymptotic symmetry algebra of two-dimensional anti-de Sitter space. We calculate the central charge of the algebra and find perfect agreement between statistical and thermodynamical entropy of AdS_2 black holes.

hep-th↗
arXiv2001

Black holes and conformal mechanics

We show how the motion of a charged particle near the horizon of an extreme Reissner-Nordstrom black hole can lead to different forms of conformal mechanics, depending on the choice of the time coordinate.

hep-th↗
arXiv2000

A Realization of the infinite dimensional Symmetries of Conformal Mechanics

We discuss the possibility of realizing the infinite dimensional symmetries of conformal mechanics as time reparametrizations, generalizing the realization of the SL(2,R) symmetry of the de Alfaro, Fubini, Furlan model in terms of quasi--primary fields. We find that this is possible using an appropriate generalization of the transformation law for the quasi-primary fields.

hep-th↗
arXiv1999

Primary scalar hair in dilatonic theories with modulus fields

We study the general spherical symmetric solutions of dilaton-modulus gravity non-minimally coupled to a Maxwell field, using methods from the theory of dynamical systems. We show that the solutions can be classified by the mass, the electric charge, and a third parameter which we argue can be related to a scalar charge. The global properties of the solutions are discussed.

gr-qc↗
arXiv1998

The dynamical structure of four-dimensional Chamseddine's gauge theory of gravity

We perform the Dirac hamiltonian analysis of a four-dimensional gauge theory of gravity with an action of topological type, which generalizes some well-known two-dimensional models. We show that, in contrast with the two-dimensional case, the theory has a non-vanishing number of dynamical degrees of freedom and that its structure is very similar to higher-dimensional Chern-Simons gravity.

gr-qc↗
arXiv1997

Classification of multidimensional inflationary models

We define under which circumstances two multi-warped product spacetimes can be considered equivalent and then we classify the spaces of constant curvature in the Euclidean and Lorentzian signature. For dimension D=2, we get essentially twelve representations, for D=3 exactly eighteen. More general, for every even D, 5D+2 cases exist, whereas for every odd D, 5D+3 cases exist. For every D, exactly one half of them has the Euclidean signature. Our definition is well suited for the discussion of multidimensional cosmological models, and our results give a simple algorithm to decide whether a given metric represents the inflationary de Sitter spacetime (in unusual coordinates) or not.

gr-qc↗
arXiv1996

Black hole solutions in four-dimensional topological gravity

We study spherically symmetric solutions of a four-dimensional theory of gravity with a topological action, which was constructed as a Yang-Mills theory of the Poincaré group and can be considered a generalization to higher dimensions of well-known two-dimensional models. We also discuss the perturbative degrees of freedom and the properties of the theory under conformal transformations.

gr-qc↗
arXiv1996

Multi-black holes and instantons in effective string theory

The effective action for string theory which takes into account non-minimal coupling of moduli admits multi-black hole solutions. The euclidean continuation of these solutions can be interpreted as an instanton mediating the splitting and recombination of the throat of extremal magnetically charged black holes.

gr-qc↗
arXiv1995

Exact solutions, symmetries and quantization of two-dimensional higher-derivative gravity with dynamical torsion

We investigate two-dimensional higher derivative gravitational theories in a Riemann-Cartan framework and obtain the most general static black hole solutions in conformal coordinates. We also consider the hamiltonian formulation of the theory and discuss its symmetries, showing they are implemented by a non-linear generalizations of the 2-dimensional Poincaré algebra. Finally, we discuss the quantization in the Dirac formalism.

gr-qc↗
arXiv1994

Black holes in generalized dilaton gravity in two dimensions

We consider two-dimensional dilaton-gravity theories with a generic exponential potential for the dilaton, and obtain the most general black hole solutions in the Schwarzshild form. We discuss their geometrical and thermodynamical properties. We also study these models from the point of view of gauge theories of the extended Poincaré group and show that they can be considered as gauge theories with broken symmetry. Finally, we examine the theory in a hamiltonian formalism and discuss its quantization and its symmetries.

hep-th↗
arXiv1994

Non-singular four-dimensional black holes and the Jackiw-Teitelboim theory

A four-dimensional dilaton-gravity action whose spherical reduction to two dimensions leads to the Jackiw-Teitelboim theory is presented. A nonsingular black hole solution of the theory is obtained and its physical interpretation is discussed. The classical and semiclassical properties of the solution and of its 2d counterpart are analysed. The 2d theory is also used to model the evaporation process of the near-extremal 4d black hole. We describe in detail the peculiarities of the black hole solutions, in particular the purely topological nature of the Hawking radiation, in the context of the Jackiw-Teitelboim theory.

hep-th↗