232,304 research outputs found
Geometric phases induced in auxiliary qubits by many-body systems near its critical points
The geometric phase induced in an auxiliary qubit by a many-body system is
calculated and discussed. Two kinds of coupling between the auxiliary qubit and
the many-body system are considered, which lead to dephasing and dissipation in
the qubit, respectively. As an example, we consider the XY spin-chain
dephasingly couple to a qubit, the geometric phase induced in the qubit is
presented and discussed. The results show that the geometric phase might be
used to signal the critical points of the many-body system, and it tends to
zero with the parameters of the many-body system going away from the critical
points
Azimuthal asymmetry in transverse energy flow in nuclear collisions at high energies
The azimuthal pattern of transverse energy flow in nuclear collisions at RHIC
and LHC energies is considered. We show that the probability distribution of
the event-by-event azimuthal disbalance in transverse energy flow is
essentially sensitive to the presence of the semihard minijet component.Comment: 6 pages, 2 figure
Geometric phase in dephasing systems
Beyond the quantum Markov approximation, we calculate the geometric phase of
a two-level system driven by a quantized magnetic field subject to phase
dephasing. The phase reduces to the standard geometric phase in the weak
coupling limit and it involves the phase information of the environment in
general. In contrast with the geometric phase in dissipative systems, the
geometric phase acquired by the system can be observed on a long time scale. We
also show that with the system decohering to its pointer states, the geometric
phase factor tends to a sum over the phase factors pertaining to the pointer
states.Comment: 4 page
Plasmon spectrum of two-dimensional electron systems with Rashba spin-orbit interaction
The dielectric function and plasmon modes of a two-dimensional electron gas
(2DEG) are studied in single- and double-quantum-well structures with Rashba
spin-orbit interaction (RSOI) in the framework of the random-phase
approximation. The RSOI splits each parabolic energy subband of a 2DEG into two
nonparabolic spin branches and affects the electronic many-body correlation and
dielectric properties of the 2DEG. The influence of the RSOI on the 2DEG
plasmon spectrum in single quantum wells appear mainly in three ways: 1) an
overall frequency lowering due to the energy band deformation; 2) a weak
frequency oscillation stemming from the spin-split energy band; and 3)an
enhancement of the Landau damping as a result of the emerging of the
inter-branch single-particle-excitation spectrum. In double quantum wells, the
above effects are enhanced for the optic plasmon mode but diminished for the
acoustic one.Comment: 7 figure
Negative Refraction and Subwavelength Lensing in a Polaritonic Crystal
We show that a two-dimensional polaritonic crystal, made of metallic rods
that support well defined plasmon oscillations, can act in a narrow frequency
range as a medium in which a negative refraction and subwavelength lensing can
occur. We show that surface modes are excited on the surface of the lens, and
that they facilitate restoration of the evanescent waves, which carry the
subwavelength image information. We demonstrate that this can occur in the
visible frequency range, for a wide range of materials, including silver and
aluminum rods, and carbon nanotubes. This flexibility should allow for an
experimental demonstration of this phenomenon in the visible frequency range.Comment: 14 pages; 4 figure
Thermal and ground-state entanglement in Heisenberg XX qubit rings
We study the entanglement of thermal and ground states in Heisernberg
qubit rings with a magnetic field. A general result is found that for
even-number rings pairwise entanglement between nearest-neighbor qubits is
independent on both the sign of exchange interaction constants and the sign of
magnetic fields. As an example we study the entanglement in the four-qubit
model and find that the ground state of this model without magnetic fields is
shown to be a four-body maximally entangled state measured by the -tangle.Comment: Four pages and one figure, small change
Spin squeezing in nonlinear spin coherent states
We introduce the nonlinear spin coherent state via its ladder operator
formalism and propose a type of nonlinear spin coherent state by the nonlinear
time evolution of spin coherent states. By a new version of spectroscopic
squeezing criteria we study the spin squeezing in both the spin coherent state
and nonlinear spin coherent state. The results show that the spin coherent
state is not squeezed in the x, y, and z directions, and the nonlinear spin
coherent state may be squeezed in the x and y directions.Comment: 4 pages, 2 figs, revised version submitted to J. Opt.
Quakes in Solid Quark Stars
A starquake mechanism for pulsar glitches is developed in the solid quark
star model. It is found that the general glitch natures (i.e., the glitch
amplitudes and the time intervals) could be reproduced if solid quark matter,
with high baryon density but low temperature, has properties of shear modulus
\mu = 10^{30~34} erg/cm^3 and critical stress \sigma_c = 10^{18~24} erg/cm^3.
The post-glitch behavior may represent a kind of damped oscillations.Comment: 11 pages, 4 figures (but Fig.3 is lost), a complete version can be
obtained by http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.htm, a new
version to be published on Astroparticle Physic
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