4,943 research outputs found
Long Distance Coupling of a Quantum Mechanical Oscillator to the Internal States of an Atomic Ensemble
We propose and investigate a hybrid optomechanical system consisting of a
micro-mechanical oscillator coupled to the internal states of a distant
ensemble of atoms. The interaction between the systems is mediated by a light
field which allows to couple the two systems in a modular way over long
distances. Coupling to internal degrees of freedom of atoms opens up the
possibility to employ high-frequency mechanical resonators in the MHz to GHz
regime, such as optomechanical crystal structures, and to benefit from the rich
toolbox of quantum control over internal atomic states. Previous schemes
involving atomic motional states are rather limited in both of these aspects.
We derive a full quantum model for the effective coupling including the main
sources of decoherence. As an application we show that sympathetic ground-state
cooling and strong coupling between the two systems is possible.Comment: 14 pages, 5 figure
Estudio comparativo de técnicas de preparación de muestraspara microscopía electrónica de transmisión de recubrimientos cerámicos proyectados por plasma
The development of advanced materials, with complex microstructures, is a permanent challenge to the development and application of new efficient techniques for microstructural characterization. In ceramic coatings on metals, there exist a differential ion-milling ratio between both components, limiting in principle the use of conventional techniques. In this work, we report on a comparative study of TEM sample preparation techniques for plasma-sprayed ceramic coatings. Firstly, we have used a procedure derived from the conventional one (polishing, dimpling, ion milling), and alternatively a new technique using focused ion-beam milling. The material selected for this study is fine-grained alumina that was plasma-sprayed on a steel substrate. The efficiency of both techniques is discussed along with the most significant microstructural features of the material subject of study
Abelian representation for nonabelian Wilson loops and the Non - Abelian Stokes theorem on the lattice
We derive the Abelian - like expression for the lattice SU(N) Wilson loop in
arbitrary irreducible representation. The continuum Abelian representation of
the SU(N) Wilson loop (for the loop without selfintersections) that has been
obtained by Diakonov and Petrov appears to be a continuum limit of this
expression. We also obtain the lattice variant of a non - Abelian Stokes
theorem and present the explicit expression for the matrix used in the
Diakonov - Petrov approach.Comment: revtex, 10 pages, ITEP-LAT/2002-3
Computing top intersections in the tautological ring of
We derive effective recursion formulae of top intersections in the
tautological ring of the moduli space of curves of genus .
As an application, we prove a convolution-type tautological relation in
.Comment: 18 page
Vortex structures in pure SU(3) lattice gauge theory
The structures of confining vortices which underlie pure SU(3) Yang-Mills
theory are studied by means of lattice gauge theory. Vortices and Z_3 monopoles
are defined as dynamical degrees of freedom of the Z_3 gauge theory which
emerges by center gauge fixing and by subsequent center projection. It is
observed for the first time for the case of SU(3) that these degrees of freedom
are sensible in the continuum limit: the planar vortex density and the monopole
density properly scales with the lattice spacing. By contrast to earlier
findings concerning the gauge group SU(2), the effective vortex theory only
reproduces 62% of the full string tension. On the other hand, however, the
removal of the vortices from the lattice configurations yields ensembles with
vanishing string tension. SU(3) vortex matter which originates from Laplacian
center gauge fixing is also discussed. Although these vortices recover the full
string tension, they lack a direct interpretation as physical degrees of
freedom in the continuum limit.Comment: 25 pages, 13 ps figures, improved presentation, results unchange
AEGIS: The color-magnitude relation for X-ray selected AGN
We discuss the relationship between rest-frame color and optical luminosity
for X-ray sources in the range 0.6<z<1.4 selected from the Chandra survey of
the Extended Groth Strip (EGS). These objects are almost exclusively active
galactic nuclei (AGN). While there are a few luminous QSOs, most are relatively
weak or obscured AGN whose optical colors should be dominated by host galaxy
light. The vast majority of AGN hosts at z~1 are luminous and red, with very
few objects fainter than M_{B}=-20.5 or bluer than U-B=0.6. This places the AGN
in a distinct region of color-magnitude space, on the ``red sequence'' or at
the top of the ``blue cloud'', with many in between these two modes in galaxy
color. A key stage in the evolution of massive galaxies is when star formation
is quenched, resulting in a migration from the blue cloud to the red sequence.
Our results are consistent with scenarios in which AGN either cause or maintain
this quenching. The large numbers of red sequence AGN imply that strong,
ongoing star formation is not a necessary ingredient for AGN activity, as black
hole accretion appears often to persist after star formation has been
terminated.Comment: 5 pages, 2 figures, accepted for publication in AEGIS ApJ Letters
special editio
Massless Thirring model in canonical quantization scheme
It is shown that the exact solvability of the massless Thirring model in the
canonical quantization scheme originates from the intrinsic linearizability of
its Heisenberg equations in the method of dynamical mappings. The corresponding
role of inequivalent representations of free massless Dirac field is
elucidated.Comment: 10 page
Relativistic Calculations of Coalescing Binary Neutron Stars
We have designed and tested a new relativistic Lagrangian hydrodynamics code,
which treats gravity in the conformally flat approximation to general
relativity. We have tested the resulting code extensively, finding that it
performs well for calculations of equilibrium single-star models, collapsing
relativistic dust clouds, and quasi-circular orbits of equilibrium solutions.
By adding in a radiation reaction treatment, we compute the full evolution of a
coalescing binary neutron star system. We find that the amount of mass ejected
from the system, much less than a percent, is greatly reduced by the inclusion
of relativistic gravitation. The gravity wave energy spectrum shows a clear
divergence away from the Newtonian point-mass form, consistent with the form
derived from relativistic quasi-equilibrium fluid sequences.Comment: 7 pages, proceedings of the ICGC 2004 meeting, to appear in Praman
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