12,399 research outputs found
Entanglement in the anisotropic Heisenberg XYZ model with different Dzyaloshinskii-Moriya interaction and inhomogeneous magnetic field
We investigate the entanglement in a two-qubit Heisenberg XYZ system with
different Dzyaloshinskii-Moriya(DM) interaction and inhomogeneous magnetic
field. It is found that the control parameters (, and )
are remarkably different with the common control parameters (,
and ) in the entanglement and the critical temperature, and these
x-component parameters can increase the entanglement and the critical
temperature more efficiently. Furthermore, we show the properties of these
x-component parameters for the control of entanglement. In the ground state,
increasing (spin-orbit coupling parameter) can decrease the critical
value and increase the entanglement in the revival region, and
adjusting some parameters (increasing and , decreasing and
) can decrease the critical value to enlarge the revival
region. In the thermal state, increasing can increase the revival
region and the entanglement in the revival region (for or ), and
enhance the critical value to make the region of high entanglement
larger. Also, the entanglement and the revival region will increase with the
decrease of (uniform magnetic field). In addition, small
(nonuniform magnetic field) has some similar properties to , and with
the increase of the entanglement also has a revival phenomenon, so that
the entanglement can exist at higher temperature for larger .Comment: 8 pages, 8 figure
Thermodynamics of Dual CFTs for Kerr-AdS Black Holes
Recently Gibbons {\it et al.} in hep-th/0408217 defined a set of conserved
quantities for Kerr-AdS black holes with the maximal number of rotation
parameters in arbitrary dimension. This set of conserved quantities is defined
with respect to a frame which is non-rotating at infinity. On the other hand,
there is another set of conserved quantities for Kerr-AdS black holes, defined
by Hawking {\it et al.} in hep-th/9811056, which is measured relative to a
frame rotating at infinity. Gibbons {\it et al.} explicitly showed that the
quantities defined by them satisfy the first law of black hole thermodynamics,
while those quantities defined by Hawking {\it et al.} do not obey the first
law. In this paper we discuss thermodynamics of dual CFTs to the Kerr-AdS black
holes by mapping the bulk thermodynamic quantities to the boundary of the AdS
space. We find that thermodynamic quantities of dual CFTs satisfy the first law
of thermodynamics and Cardy-Verlinde formula only when these thermodynamic
quantities result from the set of bulk quantities given by Hawking {\it et
al.}. We discuss the implication of our results.Comment: Revtex4, twocolumn, 6 pages, v2: 7 pages, more references and
comments added, an err correcte
A note on -partial difference equations and some applications to generating functions and -integrals
summary:We study the condition on expanding an analytic several variables function in terms of products of the homogeneous generalized Al-Salam-Carlitz polynomials. As applications, we deduce bilinear generating functions for the homogeneous generalized Al-Salam-Carlitz polynomials. We also gain multilinear generating functions for the homogeneous generalized Al-Salam-Carlitz polynomials. Moreover, we obtain generalizations of Andrews-Askey integrals and Ramanujan -beta integrals. At last, we derive type generating functions for the homogeneous generalized Al-Salam-Carlitz polynomials
A Three-Dimensional Tight-Binding Model and Magnetic Instability of KFe2e2
For a newly discovered iron-based high T_c superconducting parent material
KFe2Se2, we present an effective three-dimensional five-orbital tight-binding
model by fitting the band structures. The three t2g-symmetry orbitals of the
five Fe 3d orbitals mainly contribute to the electron-like Fermi surface, in
agreement with recent angle-resolved photoemission spectroscopy experiments. To
understand the groundstate magnetic structure, the two- and three-dimensional
dynamical spin susceptibilities within the random phase approximation are
investigated. It obviously shows a sharp peak at wave vector
(, ), indicating the magnetic instability of {\it
Nel}-type antiferromagnetic rather than (/2, /2)-type
antiferromagnetic ordering. While along \emph{c} axis, it exhibits a
ferromagnetic coupling between the nearest neighboring FeSe layers. The
difference between the present results and the experimental observation in
KxFe2-ySe2 is attributed to the presence of Fe vacancy in the latter.Comment: 14 pages, 8 figure
Storage and retrieval of continuous-variable polarization-entangled cluster states in atomic ensembles
We present a proposal for storing and retrieving a continuous-variable
quadripartite polarization-entangled cluster state, using macroscopic atomic
ensembles in a magnetic field. The Larmor precession of the atomic spins leads
to a symmetry between the atomic canonical operators. In this scheme, each of
the four spatially separated pulses passes twice through the respective
ensemble in order to map the polarization-entangled cluster state onto the
long-lived atomic ensembles. The stored state can then be retrieved by another
four read-out pulses, each crossing the respective ensemble twice. By
calculating the variances, we analyzed the fidelities of the storage and
retrieval, and our scheme is feasible under realistic experimental conditions.Comment: 6 pages, 4 figure
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