7,018 research outputs found
Studies of the nucler equation of state using numerical calculations of nuclear drop collisions
A numerical calculation for the full thermal dynamics of colliding nuclei was developed. Preliminary results are reported for the thermal fluid dynamics in such processes as Coulomb scattering, fusion, fusion-fission, bulk oscillations, compression with heating, and collisions of heated nuclei
Dual-species quantum degeneracy of potassium-40 and rubidium-87 on an atom chip
In this article we review our recent experiments with a 40K-87Rb mixture. We
demonstrate rapid sympathetic cooling of a 40K-87Rb mixture to dual quantum
degeneracy on an atom chip. We also provide details on efficient BEC
production, species-selective magnetic confinement, and progress toward
integration of an optical lattice with an atom chip. The efficiency of our
evaporation allows us to reach dual degeneracy after just 6 s of evaporation -
more rapidly than in conventional magnetic traps. When optimizing evaporative
cooling for efficient evaporation of 87Rb alone we achieve BEC after just 4 s
of evaporation and an 8 s total cycle time.Comment: 8 pages, 4 figures. To be published in the Proceedings of the 20th
International Conference on Atomic Physics, 2006 (Innsbruck, Austria
Fluctuation diagnostics of the electron self-energy: Origin of the pseudogap physics
We demonstrate how to identify which physical processes dominate the
low-energy spectral functions of correlated electron systems. We obtain an
unambiguous classification through an analysis of the equation of motion for
the electron self-energy in its charge, spin and particle-particle
representations. Our procedure is then employed to clarify the controversial
physics responsible for the appearance of the pseudogap in correlated systems.
We illustrate our method by examining the attractive and repulsive Hubbard
model in two-dimensions. In the latter, spin fluctuations are identified as the
origin of the pseudogap, and we also explain why wave pairing fluctuations
play a marginal role in suppressing the low-energy spectral weight, independent
of their actual strength.Comment: 6 pages, 2 figures + 4 pages supplementar
Dynamics of a tunable superfluid junction
We study the population dynamics of a Bose-Einstein condensate in a
double-well potential throughout the crossover from Josephson dynamics to
hydrodynamics. At barriers higher than the chemical potential, we observe slow
oscillations well described by a Josephson model. In the limit of low barriers,
the fundamental frequency agrees with a simple hydrodynamic model, but we also
observe a second, higher frequency. A full numerical simulation of the
Gross-Pitaevskii equation giving the frequencies and amplitudes of the observed
modes between these two limits is compared to the data and is used to
understand the origin of the higher mode. Implications for trapped matter-wave
interferometers are discussed.Comment: 8 pages, 7 figures; v3: Journal reference added, minor changes to
tex
Term by Spontaneous Symmetry Breaking in a generalized Abelian Higgs Model
We show that the topological term in dimensions can be
generated via spontaneous symmetry breaking in a generalized Abelian Higgs
model. Further, we also show that even in dimensions , a term gives rise to the topological massive excitations of the Abelian
gauge field and that such a term can also be generated via Higgs
mechanism.Comment: 7 pages, RevTeX, IP/BBSR/94-2
Two-point phase correlations of a one-dimensional bosonic Josephson junction
We realize a one-dimensional Josephson junction using quantum degenerate Bose
gases in a tunable double well potential on an atom chip. Matter wave
interferometry gives direct access to the relative phase field, which reflects
the interplay of thermally driven fluctuations and phase locking due to
tunneling. The thermal equilibrium state is characterized by probing the full
statistical distribution function of the two-point phase correlation.
Comparison to a stochastic model allows to measure the coupling strength and
temperature and hence a full characterization of the system
Gauge Invariance in Chern-Simons Systems
We show explicitly that the question of gauge invariance of the effective
potential in standard scalar electrodynamics remains unchanged despite the
introduction of the Chern-Simons term. The result does not depend on the
presence of the Maxwell term in the Chern-Simons territory.Comment: 10 pages, Plain Tex, DF/UFPB-14/9
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