1,186 research outputs found
Thermodynamic fermion-boson symmetry in harmonic oscillator potentials
A remarkable thermodynamic fermion-boson symmetry is found for the canonical
ensemble of ideal quantum gases in harmonic oscillator potentials of odd
dimensions. The bosonic partition function is related to the fermionic one
extended to negative temperatures, and vice versa.Comment: 7 pages, no figures, submitted to PHYSICA A. More information
available at http://www.physik.uni-osnabrueck.de/makrosysteme
Comment on: rotational properties of trapped bosons
Based on the Hellman-Feynman theorem it is shown that the average square
radius of a cloud of interacting bosons in a parabolic well can be derived from
their free energy. As an application, the temperature dependence of the moment
of inertia of non-interacting bosons in a parabolic trap is determined as a
function of the number of bosons. Well below the critical condensation
temperature, the Bose-Einstein statistics are found to substantially reduce the
moment of inertia of this system, as compared to a gas of ``distinguishable''
particles in a parabolic well.Comment: Herewith we repost our paper cond-mat/9611090 (1996). It was
published in Phys. Rev. A 55, 2453 (March 1997), three years before
cond-mat/0003471 (2000) by Schneider and Wallis. Reposted by
[email protected]
The center-of-mass response of confined systems
For confined systems of identical particles, either bosons or fermions, we
argue that the parabolic nature of the confinement potential is a prerequisite
for the non-dissipative character of the center of mass response to a uniform
probe. For an excitation in a parabolic confining potential, the half width of
the density response function depends nevertheless quantitatively on properties
of the internal degrees of freedom, as is illustrated here for an ideal
confined gas of identical particles with harmonic interparticle interactions.Comment: 4 pages REVTEX; accepted as Brief Communication in Phys. Rev.
Dynamical Exchange Effects in a Two-Dimensional Many-Polaron Gas
We calculate the influence of dynamical exchange effects on the response
properties and the static properties of a two-dimensional many-polaron gas.
These effects are not manifested in the random-phase approximation which is
widely used in the analysis of the many-polaron system. Here they are taken
into account by using a dielectric function derived in the time-dependent
Hartree-Fock formalism. At weak electron-phonon coupling, we find that
dynamical exchange effects lead to substantial corrections to the random-phase
approximation results for the ground state energy, the effective mass, and the
optical conductivity of the polaron system. Furthermore, we show that the
reduction of the spectral weight of the optical absorption spectrum at
frequencies above the longitudinal optical phonon frequency, due to many-body
effects, is overestimated by the random-phase approximation.Comment: 9 pages, 7 figure
Momentum distribution of confined bosons: temperature dependence
The momentum distribution function of a parabolically confined gas of bosons
with harmonic interparticle interactions is derived. In the Bose-Einstein
condensation region, this momentum distribution substantially deviates from a
Maxwell-Boltzmann distribution. It is argued that the determination of the
temperature of the boson gas from the Bose-Einstein momentum distribution
function is more appropriate than the currently used fitting to the high
momentum tail of the Maxwell-Boltzmann distribution.Comment: 5 REVTEX pages + 2 postscript figures. Accepted in Phys. Rev.
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