David E. Miller

Formation of Quantum-Degenerate Sodium Molecules

Ultracold sodium molecules were produced from an atomic Bose-Einstein condensate by ramping an applied magnetic field across a Feshbach resonance. More than 10(5) molecules were generated with a conversion efficiency of approximately 4%. Using laser light resonant with an atomic transition, the remaining atoms could be selectively removed, preventing fast collisional relaxation of the molecules. Time-of-flight analysis of the pure molecular sample yielded an instantaneous phase-space density greater than 20.

Non-perturbative thermodynamics of SU (N) gauge theories

Abstract The pressure near the deconfinement transition as determined up to now in lattice gauge theories shows unphysical behaviour: it can become negative and may in SU (3) even have a gap at the transition. This has been attributed to the use of only perturbatively known derivatives of coupling constants. We propose a method to evaluate the pressure, which works without these derivatives, and is valid on large lattices. In SU (2) we study the finite-volume effects and show that for lattices with spatial extent N σ ⪆15 these effects are negligible. In SU (3) we then obtain a positive and continuous pressure. The influence of non-perturbative corrections to the β-function on the energy density are investigated and found to be important, in particular for the latent heat.

Lattice QCD calculations for the physical equation of state

In this report we consider the numerical simulations at finite temperature using lattice QCD data for the computation of the thermodynamical quantities including the pressure, energy density and the entropy density. These physical quantities can be related to the equation of state for quarks and gluons. We shall apply the lattice data to the evaluation of the specific structure of the gluon and quark condensates at finite temperature in relation to the deconfinement and chiral phase transitions. Finally we mention the quantum nature of the phases at lower temperatures.

Critical velocity for superfluid flow across the BEC-BCS crossover.

Critical velocities have been observed in an ultracold superfluid Fermi gas throughout the BEC-BCS crossover. A pronounced peak of the critical velocity at unitarity demonstrates that superfluidity is most robust for resonant atomic interactions. Critical velocities were determined from the abrupt onset of dissipation when the velocity of a moving one-dimensional optical lattice was varied. The dependence of the critical velocity on lattice depth and on the inhomogeneous density profile was studied.

Dimensional reduction of SU(2) gauge theory beyond the perturbative horizon

A recent investigation has confirmed that the perturbative properties of the deconfined phase of non-abelian Yang-Mills theories at intermediate distances are shared by a renormalizable three-dimensional field model. This effective model is derived from a zero-momentum expansion of the effective action that is generated by the thermal degrees of freedom. Here we extend the investigation of the model beyond the perturbative horizon. For the example of the gauge group SU(2) it is shown that the infrared range accessible by Monte Carlo simulations is well described at least for temperatures above three times the deconfining phase transition temperature. This confirms on a non-perturbative level that dimensional reduction to a local field theory is realized at high temperature.

Phenomenological renormalization and scaling behaviour of SU(2) lattice gauge theory

Near the deconfinement transition of SU(2) gauge theory the finite-size scaling behaviour of the order parameter, the susceptibility and the normalized fourth cumulant gr is studied on Nσ3 × Nτ lattices with Nτ = 4 and 6 and Nσ = 8, 12, 18, 24or 26. For that purpose we have calculated new high-statistics data for Nτ = 6 and re-evaluated previous results obtained for Nτ = 4. In both cases we used the density of states method. We determine the critical coupling and with a new way of phenomenological renormalization the critical exponents. For Nτ = 6 we find that 4/gc,∞2 = 2.4265(30). Using the results for the criitical temperature obtained for different Nτ we examine the approach to asymptotic scaling.

Dimensional reduction in SU (3) gauge theory

Abstract We present a local effective three-dimensional lattice action for four-dimensional SU (3) gauge theory at high temperatures. It is shown that the quark potential, and sufficiently large spatial Wilson loops, are precisely reproduced by the effective theory in the temperature range down to about two times the deconfining phase transition temperature. An accurate estimate for the Debye screening mass is given.

THE HEAVY QUARK POTENTIAL IN SU(2) GAUGE-THEORY AT HIGH-TEMPERATURE

We present a detailed investigation of the heavy quark potential in the deconfined phase of pure SU(2) gauge theory at intermediate temperatures. The analysis is based on close comparison of numerical and analytical methods. The extent of the short-distance range, where because of asymptotic freedom perturbation theory gives a good description of the interaction, is determined. Slightly beyond the perturbative horizon the potential becomes that of screened colour-averaged charges. The screening length determined in that range appears to be surprisingly close to the value that is derived from a partial resummation of the continuum perturbation series.

Sodium Bose-Einstein condensates in an optical lattice

The phase transition from a superfluid to a Mott insulator has been observed in a {sup 23}Na Bose-Einstein condensate. A dye laser detuned {approx_equal}5 nm red of the Na 3{sup 2}S{yields}3{sup 2}P{sub 1/2} transition was used to form the three-dimensional optical lattice. The heating effects of the small detuning as well as the three-body decay processes constrained the time scale of the experiment. Certain lattice detunings were found to induce a large loss of atoms. These loss features were shown to be due to photoassociation of atoms to vibrational levels in the Na{sub 2} (1){sup 3}{sigma}{sub g}{sup +} state.

THE PHYSICAL PHASE OF DIMENSIONALLY REDUCED GAUGE-THEORIES

We investigate the relationship between the high-temperature deconfined phase of the SU(2) gauge theory to the phases of the corresponding three-dimensional adjoint Higgs model. For various temperatures we simulate the effective theory in a neighbourhood of the physical states, that is of those values of the coupling constants that describe the infrared behaviour of the four-dimensional theory and which have been calculated by applying dimensional reduction techniques. We show that the physical points belong to the confined phase of the SU(2) adjoint Higgs model.