8,129 research outputs found
The Structure of AdS Black Holes and Chern Simons Theory in 2+1 Dimensions
We study anti-de Sitter black holes in 2+1 dimensions in terms of Chern
Simons gauge theory of anti-de Sitter group coupled to a source. Taking the
source to be an anti-de Sitter state specified by its Casimir invariants, we
show how all the relevant features of the black hole are accounted for. The
requirement that the source be a unitary representation leads to a discrete
tower of states which provide a microscopic model for the black hole.Comment: 17 pages, LaTex. The presentation in Section 5 was improved; other
minor improvements. Final form of the manuscrip
Fourth order perturbative expansion for the Casimir energy with a slightly deformed plate
We apply a perturbative approach to evaluate the Casimir energy for a
massless real scalar field in 3+1 dimensions, subject to Dirichlet boundary
conditions on two surfaces. One of the surfaces is assumed to be flat, while
the other corresponds to a small deformation, described by a single function
, of a flat mirror. The perturbative expansion is carried out up to the
fourth order in the deformation , and the results are applied to the
calculation of the Casimir energy for corrugated mirrors in front of a plane.
We also reconsider the proximity force approximation within the context of this
expansion.Comment: 10 pages, 3 figures. Version to appear in Phys. Rev.
Local electronic nematicity in the one-band Hubbard model
Nematicity is a well known property of liquid crystals and has been recently
discussed in the context of strongly interacting electrons. An electronic
nematic phase has been seen by many experiments in certain strongly correlated
materials, in particular, in the pseudogap phase generic to many hole-doped
cuprate superconductors. Recent measurements in high superconductors has
shown even if the lattice is perfectly rotationally symmetric, the ground state
can still have strongly nematic local properties. Our study of the
two-dimensional Hubbard model provides strong support of the recent
experimental results on local rotational symmetry breaking. The
variational cluster approach is used here to show the possibility of an
electronic nematic state and the proximity of the underlying symmetry-breaking
ground state within the Hubbard model. We identify this nematic phase in the
overdoped region and show that the local nematicity decreases with increasing
electron filling. Our results also indicate that strong Coulomb interaction may
drive the nematic phase into a phase similar to the stripe structure. The
calculated spin (magnetic) correlation function in momentum space shows the
effects resulting from real-space nematicity
Model for resonant photon creation in a cavity with time dependent conductivity
In an electromagnetic cavity, photons can be created from the vacuum state by
changing the cavity's properties with time. Using a simple model based on a
massless scalar field, we analyze resonant photon creation induced by the
time-dependent conductivity of a thin semiconductor film contained in the
cavity. This time dependence may be achieved by irradiating periodically the
film with short laser pulses. This setup offers several experimental advantages
over the case of moving mirrors.Comment: 9 pages, 1 figure. Minor changes. Version to appear in Phys. Rev.
Derivative expansion of the electromagnetic Casimir energy for two thin mirrors
We extend our previous work on a derivative expansion for the Casimir energy,
to the case of the electromagnetic field coupled to two thin, imperfect
mirrors. The latter are described by means of vacuum polarization tensors
localized on the mirrors. We apply the results so obtained to compute the first
correction to the proximity force approximation to the static Casimir effect.Comment: Version to appear in Phys. Rev.
Elliptic Wess-Zumino-Witten Model from Elliptic Chern-Simons Theory
This letter continues the program aimed at analysis of the scalar product of
states in the Chern-Simons theory. It treats the elliptic case with group
SU(2). The formal scalar product is expressed as a multiple finite dimensional
integral which, if convergent for every state, provides the space of states
with a Hilbert space structure. The convergence is checked for states with a
single Wilson line where the integral expressions encode the Bethe-Ansatz
solutions of the Lame equation. In relation to the Wess-Zumino-Witten conformal
field theory, the scalar product renders unitary the
Knizhnik-Zamolodchikov-Bernard connection and gives a pairing between conformal
blocks used to obtain the genus one correlation functions.Comment: 18 pages, late
Spin-Glass Attractor on Tridimensional Hierarchical Lattices in the Presence of an External Magnetic Field
A nearest-neighbor-interaction Ising spin glass, in the presence of an
external magnetic field, is studied on different hierarchical lattices that
approach the cubic lattice. The magnetic field is considered as uniform, or
random (following either a bimodal or a Gaussian probability distribution). In
all cases, a spin-glass attractor is found, in the plane magnetic field versus
temperature, associated with a low-temperature phase. The physical consequences
of this attractor are discussed, in view of the present scenario of the
spin-glass problem.Comment: Accepted for publication in Physical Review
The proximity force approximation for the Casimir energy as a derivative expansion
The proximity force approximation (PFA) has been widely used as a tool to
evaluate the Casimir force between smooth objects at small distances. In spite
of being intuitively easy to grasp, it is generally believed to be an
uncontrolled approximation. Indeed, its validity has only been tested in
particular examples, by confronting its predictions with the next to leading
order (NTLO) correction extracted from numerical or analytical solutions
obtained without using the PFA. In this article we show that the PFA and its
NTLO correction may be derived within a single framework, as the first two
terms in a derivative expansion. To that effect, we consider the Casimir energy
for a vacuum scalar field with Dirichlet conditions on a smooth curved surface
described by a function in front of a plane. By regarding the Casimir
energy as a functional of , we show that the PFA is the leading term in a
derivative expansion of this functional. We also obtain the general form of
corresponding NTLO correction, which involves two derivatives of . We
show, by evaluating this correction term for particular geometries, that it
properly reproduces the known corrections to PFA obtained from exact
evaluations of the energy.Comment: Minor changes. Version to appear in Phys. Rev.
Unitarity of the Knizhnik-Zamolodchikov-Bernard connection and the Bethe Ansatz for the elliptic Hitchin systems
We work out finite-dimensional integral formulae for the scalar product of
genus one states of the group Chern-Simons theory with insertions of Wilson
lines. Assuming convergence of the integrals, we show that unitarity of the
elliptic Knizhnik-Zamolodchikov-Bernard connection with respect to the scalar
product of CS states is closely related to the Bethe Ansatz for the commuting
Hamiltonians building up the connection and quantizing the quadratic
Hamiltonians of the elliptic Hitchin system.Comment: 24 pages, latex fil
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