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M. Cadoni

Publications and source records attributed to M. Cadoni.

At least 73 records · Page 4Linked to original sources
arXiv2003

Entropy of the 3-brane and the AdS/CFT duality from a two-dimensional perspective

A two-dimensional (2D) scalar-tensor gravity theory is used to describe the near-horizon near-extremal behavior of black 3-branes solutions of type IIB string theory. The asymptotic symmetry group of the 2D, asymptotically anti de Sitter (AdS) metric, is generated by a Virasoro algebra. The (non-constant) configuration of the 2D scalar field, which parametrizes the volume of the 3-brane, breaks the conformal symmetry and produces a divergent central charge in the Virasoro algebra. Using a renormalization procedure we find a finite value for the central charge and by means of the Cardy formula, the entropy of the black 3-brane in terms of microstates of the conformal field theory living on the boundary of the 2D spacetime. We find for the entropy as a function of the temperature the power-law behavior $S\propto T^3$. Unfortunately, owing to a scale symmetry of the 2D model the proportionality constant is undetermined. The black 3-brane case is a nice example of how finite temperature effects in higher dimensional AdS/CFT dualities can be described by a AdS$_2$/CFT$_1$ duality endowed with a scalar field that breaks the conformal symmetry and produces a non-vanishing central charge.

hep-th↗
arXiv2002

Tachyons in de Sitter space and analytical continuation from dS/CFT to AdS/CFT

We discuss analytic continuation from d-dimensional Lorentzian de Sitter (dS$_d$) to d-dimensional Lorentzian anti-de Sitter (AdS$_{d}$) spacetime. We show that AdS$_{d}$, with opposite signature of the metric, can be obtained as analytic continuation of a portion of dS$_d$. This implies that the dynamics of (positive square-mass) scalar particles in AdS$_{d}$ can be obtained from the dynamics of tachyons in dS$_d$. We discuss this correspondence both at the level of the solution of the field equations and of the Green functions. The AdS/CFT duality is obtained as analytic continuation of the dS/CFT duality.

hep-th↗
arXiv2002

Cosmology of the Jackiw-Teitelboim model

We investigate the cosmology of the two-dimensional Jackiw-Teitelboim model. Since the matter coupling is not defined uniquely, we consider two possible choices. The dilaton field plays an important role in the discussion of the properties of the solutions. In particular, the possibility of universes having a finite initial size emerges.

gr-qc↗
arXiv2002

Two-dimensional dS/CFT correspondence

We investigate de Sitter/conformal field theory (dS/CFT) correspondence in two dimensions. We define the conserved mass of de Sitter spacetime and formulate the correspondence along the lines of anti-de Sitter/conformal field theory duality. Asymptotic symmetry group, mass, and central charge of de Sitter spacetime are equal to those of anti-de Sitter spacetime. The entropy of two-dimensional de Sitter spacetime is evaluated by applying Cardy formula. We calculate the boundary correlators induced by the propagation of the dilaton in two-dimensional de Sitter space. Although the dilaton is a tachyonic perturbation in the bulk, boundary conformal correlators have positive dimension.

hep-th↗
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↗
arXiv2000

Large N limit of Calogero-Moser models and Conformal Field Theories

We discuss the large N limit of Calogero-Moser models for the classical infinite families of simple Lie algebras A_N, B_N, C_N and D_N. We show that the limit defines two different Conformal Field Theories with central charge c>1. The value of c and the dimension of the primary field are dictated by the underlying algebraic symmetries of the model.

hep-th↗
arXiv2000

Thermodynamical Behaviour of Composite Stringy Black Holes

We study the thermodynamical and geometrical behaviour of the black holes that arise as solutions of the heterotic string action. We discuss the near-horizon scaling behaviour of the solutions that are described by two-dimensional Anti-de Sitter Space AdS(2). We find that finite-energy excitations of AdS(2) are suppressed only for scaling limits characterised by a dilaton which is constant near the horizon, whereas this suppression does not occur when the dilaton is non constant.

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↗
arXiv1998

2D Extremal Black Holes as Solitons

We discuss the relationship between two-dimensional (2D) dilaton gravity models and sine-Gordon-like field theories. We show that there is a one-to-one correspondence between the solutions of 2D dilaton gravity and the solutions of a (two fields) generalization of the sine-Gordon model. In particular, we find a connection between the soliton solutions of the generalized sine-Gordon model and extremal black hole solutions of 2D dilaton gravity. As a by-product of our calculations we find a easy way to generate cosmological solutions of 2D dilaton gravity.

hep-th↗
arXiv1997

Dualities Compositeness and Spacetime Structure of 4d Extreme Stringy Black Holes

We study the BPS black hole solutions of the (truncated) action for heterotic string theory compactified on a six-torus. The O(3,Z) duality symmetry of the theory, together with the bound state interpretation of extreme black holes, is used to generate the whole spectrum of the solutions. The corresponding spacetime structures, written in terms of the string metric, are analyzed in detail. In particular, we show that only the elementary solutions present naked singularities. The bound states have either null singularities (electric solutions) or are regular (magnetic or dyonic solutions) with near-horizon geometries given by the product of two 2d spaces of constant curvature. The behavior of some of these solutions as supersymmetric attractors is discussed. We also show that our approach is very useful to understand some of the puzzling features of charged black hole solutions in string theory.

hep-th↗
arXiv1996

The 2D analogue of the Reissner-Nordstrom solution

A two-dimensional (2D) dilaton gravity model, whose static solutions have the same features of the Reissner-Nordstrom solutions, is obtained from the dimensional reduction of a four-dimensional (4D) string effective action invariant under S-duality transformations. The black hole solutions of the 2D model and their relationship with those of the 4D theory are discussed.

gr-qc↗
arXiv1995

Dilatonic black holes in a S-duality model

We find exact charged black hole solutions of a string effective action that is invariant under S-duality transformations. These black hole solutions have the same causal structure as the Reissner-Nordstrom (RN) solutions. They reduce to the RN solutions for self-dual configurations of the dilaton and to the Garfinkle-Horowitz-Strominger (GHS) solution in the weak (or strong) coupling regime. Using the purely magnetic solutions of the S-duality model we also generate dyonic black hole solutions of the GHS model, which have the causal structure of the RN solutions.

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↗