39,253 research outputs found
Stability of the superfluid state in a disordered 1D ultracold fermionic gas
We study a 1D Fermi gas with attractive short range-interactions in a
disordered potential by the density matrix renormalization group (DMRG)
technique. This setting can be implemented experimentally by using cold atom
techniques. We identify a region of parameters for which disorder enhances the
superfluid state. As disorder is further increased, global superfluidity
eventually breaks down. However this transition occurs before the transition to
the insulator state takes place. This suggests the existence of an intermediate
metallic `pseudogap' phase characterized by strong pairing but no quasi
long-range order.Comment: 5 pages, 5 figure
Instanton classical solutions of SU(3) fixed point actions on open lattices
We construct instanton-like classical solutions of the fixed point action of
a suitable renormalization group transformation for the SU(3) lattice gauge
theory. The problem of the non-existence of one-instantons on a lattice with
periodic boundary conditions is circumvented by working on open lattices. We
consider instanton solutions for values of the size (0.6-1.9 in lattice units)
which are relevant when studying the SU(3) topology on coarse lattices using
fixed point actions. We show how these instanton configurations on open
lattices can be taken into account when determining a few-couplings
parametrization of the fixed point action.Comment: 23 pages, LaTeX, 4 eps figures, epsfig.sty; some comments adde
From Perturbation Theory to Confinement: How the String Tension is built up
We study the spatial volume dependence of electric flux energies for SU(2)
Yang-Mills fields on the torus with twisted boundary conditions. The results
approach smoothly the rotational invariant Confinement regime. The would-be
string tension is very close to the infinite volume result already for volumes
of . We speculate on the consequences of our result for
the Confinement mechanism.Comment: 6p, ps-file (uuencoded). Contribution to Lattice'93 Conference
(Dallas, 1993). Preprint INLO-PUB 18/93, FTUAM-93/4
Einstein constraints on a characteristic cone
We analyse the Cauchy problem on a characteristic cone, including its vertex,
for the Einstein equations in arbitrary dimensions. We use a wave map gauge,
solve the obtained constraints and show gauge conservation.Comment: 10 pages, to be published in the Proceedings of the 15th
International Conference on Waves and Stability in Continuous Media, held in
Palermo, 28th June to 1st July 200
Probing for Instanton Quarks with epsilon-Cooling
We use epsilon-cooling, adjusting at will the order a^2 corrections to the
lattice action, to study the parameter space of instantons in the background of
non-trivial holonomy and to determine the presence and nature of constituents
with fractional topological charge at finite and zero temperature for SU(2). As
an additional tool, zero temperature configurations were generated from those
at finite temperature with well-separated constituents. This is achieved by
"adiabatically" adjusting the anisotropic coupling used to implement finite
temperature on a symmetric lattice. The action and topological charge density,
as well as the Polyakov loop and chiral zero-modes are used to analyse these
configurations. We also show how cooling histories themselves can reveal the
presence of constituents with fractional topological charge. We comment on the
interpretation of recent fermion zero-mode studies for thermalized ensembles at
small temperatures.Comment: 26 pages, 14 figures in 33 part
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