12,288 research outputs found
Algebraic methods in the theory of generalized Harish-Chandra modules
This paper is a review of results on generalized Harish-Chandra modules in
the framework of cohomological induction. The main results, obtained during the
last 10 years, concern the structure of the fundamental series of
modules, where is a semisimple Lie
algebra and is an arbitrary algebraic reductive in
subalgebra. These results lead to a classification of simple
modules of finite type with generic minimal
types, which we state. We establish a new result about the
Fernando-Kac subalgebra of a fundamental series module. In addition, we pay
special attention to the case when is an eligible subalgebra
(see the definition in section 4) in which we prove stronger versions of our
main results. If is eligible, the fundamental series of
modules yields a natural algebraic generalization
of Harish-Chandra's discrete series modules.Comment: Keywords : generalized Harish-Chandra module, (g,k)-module of finite
type, minimal k-type, Fernando-Kac subalgebra, eligible subalgebra; Pages no.
: 13; Bibliography : 21 item
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
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
Structural Interdependence among Colombian Departments
This paper advances on the analysis of the structural interdependence among Colombian departments. The results show that Bogotá has a large influence in the other regional economies through its purchasing power. Additionally, it can be observed a centerperiphery pattern in the spatial concentration of the effects of the hypothetical extraction of any territory. From a policy point of view, the main findings reaffirm the role played by Bogotá in the polarization process observed in the regional economies in Colombia in the last years. Any policy action oriented to reduce these regional disparities should take into account that, given the structural interdependence among Colombian departments, new investment in the lagged regions would flow through Bogotá and the major regional economies.Input-output; extraction method; Colombia Classification JEL: R12; R15.
Space dependent Fermi velocity in strained graphene
We resolve some apparent discrepancies between two different models for
curved graphene: the one based on tight binding and elasticity theory, and the
covariant approach based on quantum field theory in curved space. We
demonstrate that strained or corrugated samples will have a space dependent
Fermi velocity in either approach that can affect the interpretation of some
experiments.Comment: Revised version as will appear in Phys. Rev. Let
Charge inhomogeneities due to smooth ripples in graphene sheets
We study the effect of the curved ripples observed in the free standing
graphene samples on the electronic structure of the system. We model the
ripples as smooth curved bumps and compute the Green's function of the Dirac
fermions in the curved surface. Curved regions modify the Fermi velocity that
becomes a function of the point on the graphene surface and induce energy
dependent oscillations in the local density of states around the position of
the bump. The corrections are estimated to be of a few percent of the flat
density at the typical energies explored in local probes such as scanning
tunnel microscopy that should be able to observe the predicted correlation of
the morphology with the electronics. We discuss the connection of the present
work with the recent observation of charge anisotropy in graphene and propose
that it can be used as an experimental test of the curvature effects.Comment: 9 pages, 5 figures. v2: Abstract and discussion about experimental
consequences expande
The quantum one-time pad in the presence of an eavesdropper
A classical one-time pad allows two parties to send private messages over a
public classical channel -- an eavesdropper who intercepts the communication
learns nothing about the message. A quantum one-time pad is a shared quantum
state which allows two parties to send private messages or private quantum
states over a public quantum channel. If the eavesdropper intercepts the
quantum communication she learns nothing about the message. In the classical
case, a one-time pad can be created using shared and partially private
correlations. Here we consider the quantum case in the presence of an
eavesdropper, and find the single letter formula for the rate at which the two
parties can send messages using a quantum one-time pad
Self-propelled particles with fluctuating speed and direction of motion
We study general aspects of active motion with fluctuations in the speed and
the direction of motion in two dimensions. We consider the case in which
fluctuations in the speed are not correlated to fluctuations in the direction
of motion, and assume that both processes can be described by independent
characteristic time-scales. We show the occurrence of a complex transient that
can exhibit a series of alternating regimes of motion, for two different
angular dynamics which correspond to persistent and directed random walks. We
also show additive corrections to the diffusion coefficient. The characteristic
time-scales are also exposed in the velocity autocorrelation, which is a sum of
exponential forms.Comment: to appear in Phys. Rev. Let
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