45,768 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
Evidence of chaotic modes in the analysis of four delta Scuti stars
Since CoRoT observations unveiled the very low amplitude modes that form a
flat plateau in the power spectrum structure of delta Scuti stars, the nature
of this phenomenon, including the possibility of spurious signals due to the
light curve analysis, has been a matter of long-standing scientific debate. We
contribute to this debate by finding the structural parameters of a sample of
four delta Scuti stars, CID 546, CID 3619, CID 8669, and KIC 5892969, and
looking for a possible relation between these stars' structural parameters and
their power spectrum structure. For the purposes of characterization, we
developed a method of studying and analysing the power spectrum with high
precision and have applied it to both CoRoT and Kepler light curves. We obtain
the best estimates to date of these stars' structural parameters. Moreover, we
observe that the power spectrum structure depends on the inclination,
oblateness, and convective efficiency of each star. Our results suggest that
the power spectrum structure is real and is possibly formed by 2-period island
modes and chaotic modes
Do classical configurations produce Confinement?
We show that certain classical SU(2) pure gauge configurations give rise to a
non-zero string tension. We then investigate cooled configurations generated by
Monte Carlo simulations on the lattice and find similar properties. We infer
evidence in favour of a classical model of Confinement.Comment: Uuencoded, Z-compressed and tarred file of the TeX file submit.tex
and PostScript files Stnt.eps and Stst.eps. 11 pages of text and two figure
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
Analytic Coulomb matrix elements in a three-dimensional geometry
Using a complete basis set we have obtained an analytic expression for the
matrix elements of the Coulomb interaction. These matrix elements are written
in a closed form. We have used the basis set of the three-dimensional isotropic
quantum armonic oscillator in order to develop our calculations, which can be
useful when treating interactions in localized systems.Comment: 3 pages, errat
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
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