754 research outputs found
Horizons and the Thermal Harmonic Oscillator
We show that two-dimensional anti-de Sitter spacetime (AdS_2) can be put in
correspondence, holographically, both with the harmonic oscillator and the free
particle. When AdS_2 has an horizon the corresponding mechanical system is a
thermal harmonic oscillator at temperature given by the Hawking temperature of
the horizon.Comment: Content changed, title slightly modifie
Instability of the R^3\times S^1 vacuum in low-energy effective string theory
We present and discuss an euclidean solution of the low-energy effective
string action that can be interpreded as a semiclassical decay process of the
ground state of the theory.Comment: 9 pages, plain-tex file, 2 figures available upon reques
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.Comment: 14 pages, Latex file. v2: reference adde
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.Comment: 18 pages, Latex fil
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.Comment: 10 pages, Plain-Tex, no figure
Duality of Lorentzian and Euclidean black holes in two-dimensional string-generated models
We discuss the properties of lorentzian and euclidean black hole solutions of
a generalized 2-dim dilaton-gravity action containing a modulus field, which
arises from the compactification of heterotic string models. The duality
symmetries of these solutions are also investigated.Comment: 10 pages plain Tex, 4 figures avalaible upon request from authors,
INFNCA-TH-94-
Dilatonic black holes in theories with moduli fields
We discuss the low-energy effective string theory when moduli of the
compactified manifold are present. Assuming a nontrivial coupling of the moduli
to the Maxwell tensor, we find a class of regular black hole solutions. Both
the thermodynamical and the geometrical structure of these solutions are
discussedComment: 8 page
Reply Comment on "Entropy of 2D black holes from counting microstates"
We show that the arguments proposed by Park and Yee against our recent
derivation of the statistical entropy of 2D black holes do not apply to the
case under considerationComment: 3 pages, LaTex file, reply to comment hep-th/991021
Holographic Central Charge for 2-Dimensional de Sitter Space
Recently, investigations have begun into a holographic duality for
two-dimensional de Sitter space. In this paper, we evaluate the associated
central charge, using a modified version of the canonical Hamiltonian method
that was first advocated by Catelani {\it et al}. Our computation agrees with
that of a prior work (Cadoni {\it et al}), but we argue that the method used
here is, perhaps, aesthetically preferable on holographic grounds. We also
confirm an agreement between the Cardy and thermodynamic entropy, thus
providing further support for the conjectured two-dimensional de
Sitter/conformal field theory correspondence.Comment: 19 pages, Latex; discussion (Section 4) and references adde
Black Hole fragmentation and holography
We discuss the entropy change due to fragmentation for black hole solutions
in various dimensions. We find three different types of behavior. The entropy
may decrease, increase or have a mixed behavior, characterized by the presence
of a threshold mass. For two-dimensional (2D) black holes we give a complete
characterization of the entropy behavior under fragmentation, in the form of
sufficient conditions imposed on the function J, which defines the 2D
gravitational model. We compare the behavior of the gravitational solutions
with that of free field theories in d dimensions. This excludes the possibility
of finding a gravity/field theory realization of the holographic principle for
a broad class of solutions, including asymptotically flat black holes. We find
that the most natural candidates for holographic duals of the black hole
solutions with mixed behavior are field theories with a mass gap. We also
discuss the possibility of formulating entropy bounds that make reference only
to the energy of a system.Comment: 7 pages, no figure
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