2,469 research outputs found

### Generalizations of the thermal Bogoliubov transformation

The thermal Bogoliubov transformation in thermo field dynamics is generalized
in two respects. First, a generalization of the $\alpha$--degree of freedom to
tilde non--conserving representations is considered. Secondly, the usual
$2\times2$ Bogoliubov matrix is extended to a $4\times4$ matrix including
mixing of modes with non--trivial multiparticle correlations. The analysis is
carried out for both bosons and fermions.Comment: 20 pages, Latex, Nordita 93/33

### String Entanglement and D-branes as Pure States

We study the entanglement of closed strings degrees of freedom in order to
investigate the microscopic structure and statistics of objects as D-branes. By
considering the macroscopic pure state (MPS) limit, whenever the entanglement
entropy goes to zero (in such a way that the macroscopic properties of the
state are preserved), we show that boundary states may be recovered in this
limit and, furthermore, the description through closed string (perturbative)
degrees of freedom collapses. We also show how the thermal properties of branes
and closed strings could be described by this model, and it requires that
dissipative effects be taken into account. Extensions of the MPS analysis to
more general systems at finite temperature are finally emphasized.Comment: 14 pages. Minor improvements. Published in Phys. Rev.

### Wigner functions of thermo number state, photon subtracted and added thermo vacuum state at finite temperature

Based on Takahashi-Umezawa thermo field dynamics and the order-invariance of
Weyl ordered operators under similar transformations, we present a new approach
to deriving the exact Wigner functions of thermo number state, photon
subtracted and added thermo vacuum state. We find that these Wigner functions
are related to the Gaussian-Laguerre type functions of temperature, whose
statistical properties are then analysed.Comment: 10 pages and 2 figure

### Diagonalization of full finite temperature Green's function by quasi-particles

For thermal systems, standard perturbation theory breaks down because of the
absence of stable, observable asymptotic states. We show, how the introduction
of {\it statistical} quasi-particles (stable, but not observable) gives rise to
a consistent description. Statistical and spectral information can be cleanly
separated also for interacting systems.Comment: 9 pages in standard LaTe

### No-cloning theorem in thermofield dynamics

We discuss the relation between the no-cloning theorem from quantum
information and the doubling procedure used in the formalism of thermofield
dynamics (TFD). We also discuss how to apply the no-cloning theorem in the
context of thermofield states defined in TFD. Consequences associated to mixed
states, von Neumann entropy and thermofield vacuum are also addressed.Comment: 16 pages, 3 figure

### 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 $\theta = \pi$ 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 $(T_c,\mu_c)\simeq(273,94)$ MeV at
$\theta = \pi$ for such a transition.Comment: 10 pages, 12 figure

### 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

### The Delta-Hole model at Finite Temperature

The spectral function of pions interacting with a gas of nucleons and
Delta-33-resonances is investigated using the formalism of Thermo Field
Dynamics. After a discussion of the zero Delta-width approximation at finite
temperature, we take into account a constant width of the resonance. Apart from
a full numerical calculation, we give analytical approximations to the pionic
spectral function including such a width. They are found to be different from
previous approximations, and require an increase of the effective Delta-width
in hot compressed nuclear matter. The results are summarized in an effective
dispersion relation for interacting pions.Comment: 34 pages in standard LaTeX GSI-preprint No. GSI-93-2

### Topological Discrete Algebra, Ground State Degeneracy, and Quark Confinement in QCD

Based on the permutation group formalism, we present a discrete symmetry
algebra in QCD. The discrete algebra is hidden symmetry in QCD, which is
manifest only on a space-manifold with non-trivial topology. Quark confinement
in the presence of the dynamical quarks is discussed in terms of the discrete
symmetry algebra. It is shown that the quark deconfinement phase has the ground
state degeneracy depending on the topology of the space, which gives a
gauge-invariant distinction between the confinement and deconfinement phases.
We also point out that new quantum numbers relating to the fractional quantum
Hall effect exist in the deconfinement phase.Comment: 11 pages, 1 figur

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