31,404 research outputs found
Vacuum structure and effective potential at finite temperature: a variational approach
We compute the effective potential for theory with a squeezed
coherent state type of construct for the ground state. The method essentially
consists in optimising the basis at zero and finite temperatures. The gap
equation becomes identical to resumming the infinite series of daisy and super
daisy graphs while the effective potential includes multiloop effects and
agrees with that obtained through composite operator formalism at finite
temperature.Comment: 15 pages, Revtex, No figures, to appear in Jou. of Phys.G(Nucl. and
Part. Phys.
Strong CP violation and chiral symmetry breaking in hot and dense quark matter
We investigate chiral symmetry breaking and strong CP violation effects in
the phase diagram of strongly interacting matter. We demonstrate the effect of
strong CP violating terms on the phase structure at finite temperature and
densities in a 3-flavor Nambu-Jona-Lasinio (NJL) model including the
Kobayashi-Maskawa-t'Hooft (KMT) determinant term. This is investigated using an
explicit structure for the ground state in terms of quark-antiquark condensates
for both in the scalar and the pseudoscalar channels. CP restoring transition
with temperature at zero baryon density is found to be a second order
transition at while the same at finite chemical potential and
small temperature turns out to be a first order transition. Within the model,
the tri-critical point turns out to be MeV at
for such a transition.Comment: 10 pages, 12 figure
Chiral Symmetry Breaking and Pion Wave Function
We consider here chiral symmetry breaking through nontrivial vacuum structure
with quark antiquark condensates. We then relate the condensate function to the
wave function of pion as a Goldstone mode. This simultaneously yields the pion
also as a quark antiquark bound state as a localised zero mode in vacuum. We
illustrate the above with Nambu Jona-Lasinio model to calculate different
pionic properties in terms of the vacuum structure for breaking of exact or
approximate chiral symmetry, as well as the condensate fluctuations giving rise
to mesons.Comment: latex, revtex, 16 page
Isospin dependent kaon and antikaon optical potentials in dense hadronic matter
Isospin effects on the optical potentials of kaons and antikaons in dense
hadronic matter are investigated using a chiral SU(3) model. These effects are
important for asymmetric heavy ion collision experiments. In the present work
the dispersion relations are derived for kaons and antikaons, compatible with
the low energy scattering data, within our model approach. The relations result
from the kaonic interactions with the nucleons, vector mesons and scalar mesons
in the asymmetric nuclear matter. The isospin asymmetry effects arising from
the interactions with the vector-isovector - meson as well as the scalar
isovector mesons are considered. The density dependence of the isospin
asymmetry is seen to be appreciable for the kaon and antikaon optical
potentials. This can be particularly relevant for the future accelerator
facility FAIR at GSI, where experiments using neutron rich beams are planned to
be used in the study of compressed baryonic matter.Comment: 21 pages, 7 figure
Spin-Charge Decoupling and Orthofermi Quantum Statistics
Currently Gutzwiller projection technique and nested Bethe ansatz are two
main methods used to handle electronic systems in the infinity limit. We
demonstrate that these two approaches describe two distinct physical systems.
In the nested Bethe ansatz solutions, there is a decoupling between the spin
and charge degrees of freedom. Such a decoupling is absent in the Gutzwiller
projection technique. Whereas in the Gutzwiller approach, the usual
antisymmetry of space and spin coordinates is maintained, we show that the
Bethe ansatz wave function is compatible with a new form of quantum statistics,
viz., orthofermi statistics. In this statistics, the wave function is
antisymmetric in spatial coordinates alone. This feature ultimately leads to
spin-charge decoupling.Comment: 12 pages, LaTex Journal_ref: A slightly abridged version of this
paper has appeared as a brief report in Phys. Rev. B, Vol. 63, 132405 (2001
D mesons and charmonium states in asymmetric nuclear matter at finite temperatures
We investigate the in-medium masses of and mesons in the
isospin-asymmetric nuclear matter at finite temperatures arising due to the
interactions with the nucleons, the scalar isoscalar meson , and the
scalar iso-vector meson within a SU(4) model. The in-medium masses of
and the excited charmonium states ( and ) are
also calculated in the hot isospin asymmetric nuclear matter in the present
investigation. These mass modifications arise due to the interaction of the
charmonium states with the gluon condensates of QCD, simulated by a scalar
dilaton field introduced to incorporate the broken scale invariance of QCD
within the effective chiral model. The change in the mass of in the
nuclear matter with the density is seen to be rather small, as has been shown
in the literature by using various approaches, whereas, the masses of the
excited states of charmonium ( and ) are seen to have
considerable drop at high densities. The present study of the in-medium masses
of () mesons as well as of the charmonium states will be of
relevance for the observables from the compressed baryonic matter, like the
production and collective flow of the () mesons, resulting from the
asymmetric heavy ion collision experiments planned at the future facility of
the FAIR, GSI. The mass modifications of and mesons as well as of
the charmonium states in hot nuclear medium can modify the decay of the
charmonium states () to pairs in the hot
dense hadronic matter. The small attractive potentials observed for the
mesons may lead to formation of the mesic nuclei.Comment: 61 pages, 19 figues, to be published in Phys. Rev.
Interior gap superfluidity in a two-component Fermi gas of atoms
A new superfluid phase in Fermi matter, termed as "interior gap" (IG) or
"breached pair", has been recently predicted by Liu and Wilczek [Phys.Rev.Lett.
{\bf 90}, 047002 (2003)]. This results from pairing between fermions of two
species having essentially different Fermi surfaces. Using a nonperturbative
variational approach, we analyze the features, such as energy gap, momentum
distributions, and elementary excitations associated with the predicted phase.
We discuss possible realization of this phase in two-component Fermi gases in
an optical trap.Comment: 5 page
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