2,273 research outputs found
Dielectric correction to the Chiral Magnetic Effect
We derive an electric current density in the presence of a magnetic
field and a chiral chemical potential . We show that has
not only the anomaly-induced term (i.e. Chiral Magnetic
Effect) but also a non-anomalous correction which comes from interaction
effects and expressed in terms of the susceptibility. We find the correction
characteristically dependent on the number of quark flavors. The numerically
estimated correction turns out to be a minor effect on heavy-ion collisions but
can be tested by the lattice QCD simulation.Comment: 4 pages, 1 figur
Dynamics of rapidly rotating Bose-Einstein condensates in a harmonic plus quartic trap
A two-dimensional rapidly rotating Bose-Einstein condensate in a harmonic
plus quartic trap is expected to have unusual vortex states that do not occur
in a pure harmonic trap. At a critical rotation speed , a central
hole appears in the condensate, and at some faster rotation speed ,
the system undergoes a transition to a giant vortex state with pure
irrotational flow. Using a time-dependent variational analysis, we study the
behavior of an annular condensate with a single concentric ring of vortices.
The transition to a giant vortex state is investigated by comparing the energy
of the two equilibrium states (the ring of vortices and the giant vortex) and
also by studying the dynamical stability of small excitation modes of the ring
of vortices.Comment: 12pages, 4figure
An efficient method for the Quantum Monte Carlo evaluation of the static density-response function of a many-electron system
In a recent Letter we introduced Hellmann-Feynman operator sampling in
diffusion Monte Carlo calculations. Here we derive, by evaluating the second
derivative of the total energy, an efficient method for the calculation of the
static density-response function of a many-electron system. Our analysis of the
effect of the nodes suggests that correlation is described correctly and we
find that the effect of the nodes can be dealt with
Two-fluid model for a rotating trapped Fermi gas in the BCS phase
We investigate the dynamical properties of a superfluid gas of trapped
fermionic atoms in the BCS phase. As a simple example we consider the reaction
of the gas to a slow rotation of the trap. It is shown that the currents
generated by the rotation can be understood within a two-fluid model similar to
the one used in the theory of superconductors, but with a position dependent
ratio of normal and superfluid densities. The rather general result of this
paper is that already at very low temperatures, far below the critical one, an
important normal-fluid component appears in the outer regions of the gas. This
renders the experimental observation of superfluidity effects more difficult
and indicates that reliable theoretical predictions concerning other dynamical
properties, like the frequencies of collective modes, can only be made by
taking into account temperature effects.Comment: 6 pages, 4 figure
Effects of disorder on the vortex charge
We study the influence of disorder on the vortex charge, both due to random
pinning of the vortices and due to scattering off non-magnetic impurities. In
the case when there are no impurities present, but the vortices are randomly
distributed, the effect is very small, except when two or more vortices are
close by. When impurities are present, they have a noticeable effect on the
vortex charge. This, together with the effect of temperature, changes
appreciably the vortex charge. In the case of an attractive impurity potential
the sign of the charge naturally changes.Comment: 10 pages, 16 figures. Accepted in Phys. Rev.
Approximation for discrete Fourier transform and application in study of three-dimensional interacting electron gas
The discrete Fourier transform is approximated by summing over part of the
terms with corresponding weights. The approximation reduces significantly the
requirement for computer memory storage and enhances the numerical computation
efficiency with several orders without loosing accuracy. As an example, we
apply the algorithm to study the three-dimensional interacting electron gas
under the renormalized-ring-diagram approximation where the Green's function
needs to be self-consistently solved. We present the results for the chemical
potential, compressibility, free energy, entropy, and specific heat of the
system. The ground-state energy obtained by the present calculation is compared
with the existing results of Monte Carlo simulation and random-phase
approximation.Comment: 11 pages, 13 figure
Thermal equilibrium of two quantum Brownian particles
The influence of the environment in the thermal equilibrium properties of a
bipartite continuous variable quantum system is studied. The problem is treated
within a system-plus-reservoir approach. The considered model reproduces the
conventional Brownian motion when the two particles are far apart and induces
an effective interaction between them, depending on the choice of the spectral
function of the bath. The coupling between the system and the environment
guarantees the translational invariance of the system in the absence of an
external potential. The entanglement between the particles is measured by the
logarithmic negativity, which is shown to monotonically decrease with the
increase of the temperature. A range of finite temperatures is found in which
entanglement is still induced by the reservoir.Comment: 8 pages, 1 figur
Anomalous Pinning Fields in Helical Magnets: Screening of the Quasiparticle Interaction
The spin-orbit interaction strength g_so in helical magnets determines both
the pitch wave number q and the critical field H_c1 where the helix aligns with
an external magnetic field. Within a standard Landau-Ginzburg-Wilson (LGW)
theory, a determination of g_so in MnSi and FeGe from these two observables
yields values that differ by a factor of 20. This discrepancy is remedied by
considering the fermionic theory underlying the LGW theory, and in particular
the effects of screening on the effective electron-electron interaction that
results from an exchange of helical fluctuations.Comment: 4pp, 2 fig
Coupling of hydrodynamics and quasiparticle motion in collective modes of superfluid trapped Fermi gases
At finite temperature, the hydrodynamic collective modes of superfluid
trapped Fermi gases are coupled to the motion of the normal component, which in
the BCS limit behaves like a collisionless normal Fermi gas. The coupling
between the superfluid and the normal components is treated in the framework of
a semiclassical transport theory for the quasiparticle distribution function,
combined with a hydrodynamic equation for the collective motion of the
superfluid component. We develop a numerical test-particle method for solving
these equations in the linear response regime. As a first application we study
the temperature dependence of the collective quadrupole mode of a Fermi gas in
a spherical trap. The coupling between the superfluid collective motion and the
quasiparticles leads to a rather strong damping of the hydrodynamic mode
already at very low temperatures. At higher temperatures the spectrum has a
two-peak structure, the second peak corresponding to the quadrupole mode in the
normal phase.Comment: 14 pages; v2: major changes (effect of Hartree field included
Phase diagram of a Bose gas near a wide Feshbach resonance
In this paper, we study the phase diagram of a homogeneous Bose gas with a
repulsive interaction near a wide Feshbach resonance at zero temperature. The
Bose-Einstein-condensation (BEC) state of atoms is a metastable state. When the
scattering length exceeds a critical value depending on the atom density
, , the molecular excitation energy is imaginary and the atomic
BEC state is dynamically unstable against molecule formation. The BEC state of
diatomic molecules has lower energy, where the atomic excitation is gapped and
the molecular excitation is gapless. However when the scattering length is
above another critical value, , the molecular BEC state becomes a
unstable coherent mixture of atoms and molecules. In both BEC states, the
binding energy of diatomic molecules is reduced due to the many-body effect.Comment: 5 pages, 4 figure
- …