120 research outputs found
Parent Action Approach for the Duality between Non-Abelian Self-Dual and Yang-Mills-Chern-Simons Models
It has been argued by some authors that the parent action approach cannot be
used in order to establish the duality between the 2+1 Abelian and non-Abelian
Self-Dual (SD) and Yang-Mills-Chern-Simons (YMCS) models for all the coupling
regimes. We propose here an alternative (perturbative) point of view, and show
that this equivalence can be achieved with the parent action approach.Comment: To be published in Phys. Lett.
Spacetime Geometry as Statistic Ensemble of Strings
Jacobson theorem (Ref. \cite{jacobson}) shows that Einstein gravity may be
understood as a thermodynamical equation of state; a microscopic realization of
this result is however lacking. In this paper, we propose that this may be
achieved by assuming the spacetime geometry as a macroscopic system, whose
thermodynamical behavior is described by a statistical ensemble, whose
microscopic components are low-dimensional geometries. We show that this
picture is consistent with string theory by proposing a particular model for
the microscopic geometry, where the spacetime metric plays the role of an
ordinary thermodynamical potential in a special ensemble. In this scenario,
Einstein equation is indeed recovered as an equation of state, and the black
hole thermodynamics is reproduced in a thermodynamic limit (large length
scales). The model presented here is background-independent and, in particular,
it provides an alternative formulation of string theory.Comment: 14 pages, no figure
Emergent spacetime, and a model for unitary gravitational collapse in AdS
We propose a CFT unitary description of the gravitational collapse. The
starting point is the model of a black hole in AdS proposed by Maldacena in
arXiv: 0106112 [hep-th]. We show that by proposing a two-copies version of the
AdS/CFT conjecture, the process of formation of black holes so as other
spacetimes with horizons may be described as an unitary process in the dual
field theory. In doing this, we construct a well defined framework to describe
general spacetimes as entangled states, in terms of the spectrum of states on
the exact Anti-de-Sitter background. As application, we show how the
description of the Hawking-Page transition results simplified in this formalism
and some novel aspects may be observed. Finally, a simplified analysis based on
weakly coupled bulk fields is discussed.Comment: 19 pages, 1 figur
Area Operators in Holographic Quantum Gravity
We argue that the holographic formula relating entanglement entropy and the
area of a minimal surface is the key to define the area of surfaces in the
(emergent) spacetime from the dual theory on the boundary. So we promote the
entropy/area relation to operators to define the "area" observable in a
holographic formulation of quantum gravity, then we find a suitable geometric
representation for the states, and show that the Ryu-Takayanagi proposal is
recovered in the approximation of semi-classical gravity. Finally, we discuss
this picture in the example of a AdS-Black hole.Comment: Essay written for the Gravity Research Foundation 2014 Awards for
Essays on Gravitation. Minor corrections. Figure and reference adde
Lorentz Symmetry Breaking and Planar Effects from Non-Linear Electrodynamics
We propose a modification of standard linear electrodynamics in four
dimensions, where effective non-trivial interactions of the electromagnetic
field with itself and with matter fields induce Lorentz violating Chern-Simons
terms. This yields two consequences: it provides a more realistic and general
scenario for the breakdown of Lorentz symmetry in electromagnetism and it may
explain the effective behavior of the electromagnetic field in certain planar
phenomena (for instance, Hall effect). A number of proposals for non-linear
electrodynamics is discussed along the paper. Important physical implications
of the breaking of Lorentz symmetry, such as optical birefringence and the
possibility of having conductance in the vacuum are commented on
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