116 research outputs found
Phases of a bilayer Fermi gas
We investigate a two-species Fermi gas in which one species is confined in
two parallel layers and interacts with the other species in the
three-dimensional space by a tunable short-range interaction. Based on the
controlled weak coupling analysis and the exact three-body calculation, we show
that the system has a rich phase diagram in the plane of the effective
scattering length and the layer separation. Resulting phases include an
interlayer s-wave pairing, an intralayer p-wave pairing, a dimer Bose-Einstein
condensation, and a Fermi gas of stable Efimov-like trimers. Our system
provides a widely applicable scheme to induce long-range interlayer
correlations in ultracold atoms.Comment: 5 pages, 5 figures; (v2) stability of trimer is emphasized; (v3)
published versio
Realisation of chiral symmetry in the domain model of QCD
The domain model for the QCD vacuum has previously been developed and shown
to exhibit confinement of quarks and strong correlation of the local chirality
of quark modes and duality of the background domain-like gluon field. Quark
fluctuations satisfy a chirality violating boundary conditions parametrized by
a random chiral angle on the domain. The free energy of an
ensemble of domains depends on through
the logarithm of the quark determinant. Its parity odd part is given by the
axial anomaly. The anomaly contribution to the free energy suppresses
continuous axial U(1) degeneracy in the ground state, leaving only a residual
axial Z(2) symmetry. This discrete symmetry and flavour chiral symmetry in turn are spontaneously broken with a quark
condensate arising due to the asymmetry of the spectrum of Dirac operator. In
order to illustrate the splitting between the from octet pseudoscalar
mesons realised in the domain model, we estimate the masses of light
pseudoscalar and vector mesons.Comment: 27 pages, uses RevTeX, 3 figures. v.2. includes additional references
and comment
CP-violating theta parameter in the domain model of the QCD vacuum
A non-zero CP-violating parameter is treated in the domain model
which assumes a cluster-like vacuum structure whose units are characterised in
particular by a topological charge which is not necessarily an integer number.
In the present paper we restrict consideration to rational values of the
charge. The model has previously been shown to manifest confinement,
spontaneous chiral symmetry breaking and the absence of an axial U(1) Goldstone
boson. We find that the specific structure of the minima of the free energy
density of the domain ensemble forces a -periodicity of observables in
for any number of light quarks, that vacuum doubling occurs at
for any and any value of topological charge . These
features are in agreement with expectations based on anomalous Ward identities
and large effective theories. We find also additional values of
depending on for which vacuum doubling occurs.Comment: 10 pages, 6 figures. Final version with modification of Eq.(2),
additional references, minor typographical correction
Plasma assisted fabrication of zinc oxide based nanostructures
ZnO/Ag nanocomposite structures were prepared by using a discharge with an atmospheric-pressure mi-croplasma cathode and a solid metal anode immersed in an electrolyte solution and their properties were studied. The effect of Ag on the microstructure and optical properties of ZnO has been discussed
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