7 research outputs found
Two-dimensional dilute Bose gas in the normal phase
We consider a two-dimensional dilute Bose gas above its superfluid transition
temperature. We show that the t-matrix approximation corresponds to the leading
set of diagrams in the dilute limit, provided the temperature is sufficiently
larger than the superfluid transition temperature. Within this approximation,
we give an explicit expression for the wave vector and frequency dependence of
the self-energy, and calculate the corrections to the chemical potential and
the effective mass arising from the interaction. We also argue that the
breakdown of the t-matrix approximation, which occurs upon lowering the
temperature, provides a simple criterion to estimate the superfluid critical
temperature for the two-dimensional dilute Bose gas. The critical temperature
identified by this criterion coincides with earlier results obtained by Popov
and by Fisher and Hohenberg using different methods. Extension of this
procedure to the three-dimensional case gives good agreement with recent Monte
Carlo data.Comment: 9 pages, 3 Figure
Local exchange-correlation vector potential with memory in Time-Dependent Density Functional Theory: the generalized hydrodynamics approach
Using Landau Fermi liquid theory we derive a nonlinear non-adiabatic
approximation for the exchange-correlation (xc) vector potential defined by the
xc stress tensor. The stress tensor is a local nonlinear functional of two
basic variables - the displacement vector and the second-rank tensor which
describes the evolution of momentum in a local frame moving with Eulerian
velocity. For irrotational motion and equilibrium initial state the dependence
on the tensor variable reduces to that on a metrics generated by a dynamical
deformation of the system.Comment: RevTex, 5 pages, no figures. Final version published in PR
Correlation effects and the high-frequency spin susceptibility of an electron liquid: Exact limits
Spin correlations in an interacting electron liquid are studied in the
high-frequency limit and in both two and three dimensions. The third-moment sum
rule is evaluated and used to derive exact limiting forms (at both long- and
short-wavelengths) for the spin-antisymmetric local-field factor, . In two dimensions is found to diverge as at long wavelengths,
and the spin-antisymmetric exchange-correlation kernel of time-dependent spin
density functional theory diverges as in both two and three dimensions.
These signal a failure of the local-density approximation, one that can be
redressed by alternative approaches.Comment: 5 page