Aurel Bulgac

Spin 1/2 Fermions in the Unitary Regime: A Superfluid of a New Type

We study, in a fully nonperturbative calculation, a dilute system of spin 1/2 interacting fermions, characterized by an infinite scattering length at finite temperatures. Various thermodynamic properties and the condensate fraction are calculated and we also determine the critical temperature for the superfluid-normal phase transition in this regime. The thermodynamic behavior appears as a rather surprising and unexpected mélange of fermionic and bosonic features. The thermal response of a spin 1/2 fermion at the BCS-BEC crossover should be classified as that of a new type of superfluid.

Canonical ensembles from chaos

Abstract We present methods to compute thermodynamic properties of classical systems which involve extending the phase space by two degrees of freedom. These two additional degrees of freedom are used to replicate the coupling of the original system to the infinite degrees of freedom of a heat bath. In the extended phase space, the trajectories are ergodic. This feature enables one to replace phase space averages by time averages, which are extremely simple to compute. We examine phase space patterns, thermal distributions, correlations, ergodicity, Lyapunov exponents, mixing, and rate of convergence in an analysis of several simple systems.

Scalar Casimir effect between Dirichlet spheres or a plate and a sphere

We present a simple formalism for the evaluation of the Casimir energy for two spheres and a sphere and a plane, in case of a scalar fluctuating field, valid at any separations. We compare the exact results with various approximation schemes and establish when such schemes become useful. The formalism can be easily extended to any number of spheres and/or planes in three or arbitrary dimensions, with a variety of boundary conditions or nonoverlapping potentials/nonideal reflectors.

Renormalization of the Hartree-Fock-Bogoliubov equations in the case of a zero range pairing interaction.

We introduce a natural and simple way to implement the regularization scheme of the Hartree-Fock-Bogoliubov equations with zero range pairing interaction. The renormalization scheme proves to be equivalent to a simple energy cutoff with a position dependent running coupling constant.

Quantum Monte Carlo simulations of the BCS-BEC crossover at finite temperature

The quantum Monte Carlo method for spin-

Finite-Temperature Pairing Gap of a Unitary Fermi Gas by Quantum Monte Carlo Calculations

\frac{1}{2}

Local-density-functional theory for superfluid fermionic systems : The unitary gas

fermions at finite temperature is formulated for dilute systems with an

Isovector Giant Dipole Resonance from the 3D Time-Dependent Density Functional Theory for Superfluid Nuclei

s

Induced Fission of

-wave interaction. The motivation and the formalism are discussed along with descriptions of the algorithm and various numerical issues. We report on results for the energy, entropy, and chemical potential as a function of temperature. We give upper bounds on the critical temperature

^{240}

{T}_{c}