235,755 research outputs found
Deconfinement transition for nonzero baryon density in the Field Correlator Method
Deconfinement phase transition due to disappearance of confining
colorelectric field correlators is described using nonperturbative equation of
state. The resulting transition temperature at any chemical
potential is expressed in terms of the change of gluonic condensate
and absolute value of Polyakov loop , known from
lattice and analytic data, and is in good agreement with lattice data for
GeV. E.g. GeV for
respectively.Comment: 8 pages, 1 figure, LaTeX2e; some typos correcte
Induced quantum numbers of a magnetic monopole at finite temperature
A Dirac electron field is quantized in the background of a Dirac magnetic
monopole, and the phenomenon of induced quantum numbers in this system is
analyzed. We show that, in addition to electric charge, also squares of orbital
angular momentum, spin, and total angular momentum are induced. The functional
dependence of these quantities on the temperature and the CP-violating vacuum
angle is determined. Thermal quadratic fluctuations of charge and squared total
angular momentum, as well as the correlation between them and their
correlations with squared orbital angular momentum and squared spin, are
examined. We find the conditions when charge and squared total angular momentum
at zero temperature are sharp quantum observables rather than mere quantum
averages.Comment: 24 pages, minor grammatical changes, journal versio
Experimental observation of the longitudinal plasma excitation in intrinsic Josephson junctions
We have investigated the current-voltage characteristics (IVCs) of intrinsic
Josephson junctions (IJJs). Recently, it is predicted that the longitudinal
plasma wave can be excited by the parametric resonance in IJJs. Such an
excitation induces a singularity called as breakpoint region around switch back
region in the IVC. We have succeeded in the observation of the breakpoint
region in the IVC of the mesa with 5 IJJs at 4.2 K. Furthermore, it is found
that the temperature dependence of the breakpoint current is in agreement with
the theoretical prediction. This suggests that the wave number of the excited
plasma wave varies with temperature.Comment: 7 pages, 7 figures. Dubna-Nano2008, Accepted for JPCS
Josephson -junctions based on structures with complex normal/ferromagnet bilayer
We demonstrate that Josephson devices with nontrivial phase difference in the ground state can be realized in structures composed
from longitudinally oriented normal metal (N) and ferromagnet (F) films in the
weak link region. Oscillatory coupling across F-layer makes the first harmonic
in the current-phase relation relatively small, while coupling across N-layer
provides negative sign of the second harmonic. To derive quantitative criteria
for a -junction, we have solved two-dimensional boundary-value problem
in the frame of Usadel equations for overlap and ramp geometries of S-NF-S
structures. Our numerical estimates show that -junctions can be
fabricated using up-to-date technology.Comment: 14 pages, 9 figure
Properties of tunnel Josephson junctions with a ferromagnetic interlayer
We investigate superconductor/insulator/ferromagnet/superconductor (SIFS)
tunnel Josephson junctions in the dirty limit, using the quasiclassical theory.
We formulate a quantitative model describing the oscillations of critical
current as a function of thickness of the ferromagnetic layer and use this
model to fit recent experimental data. We also calculate quantitatively the
density of states (DOS) in this type of junctions and compare DOS oscillations
with those of the critical current.Comment: 9 pages, 8 figures, to be published in Phys. Rev.
Analytic calculation of field-strength correlators
Field correlators are expressed using background field formalism through the
gluelump Green's functions. The latter are obtained in the path integral and
Hamiltonian formalism. As a result behaviour of field correlators is obtained
at small and large distances both for perturbative and nonperturbative parts.
The latter decay exponentially at large distances and are finite at x=0, in
agreement with OPE and lattice data.Comment: 28 pages, no figures; new material added, misprints correcte
The matrix Hamiltonian for hadrons and the role of negative-energy components
The world-line (Fock-Feynman-Schwinger) representation is used for quarks in
arbitrary (vacuum and valence gluon) field to construct the relativistic
Hamiltonian. After averaging the Green's function of the white system
over gluon fields one obtains the relativistic Hamiltonian, which is matrix in
spin indices and contains both positive and negative quark energies. The role
of the latter is studied in the example of the heavy-light meson and the
standard einbein technic is extended to the case of the matrix Hamiltonian.
Comparison with the Dirac equation shows a good agreement of the results. For
arbitrary system the nondiagonal matrix Hamiltonian components are
calculated through hyperfine interaction terms. A general discussion of the
role of negative energy components is given in conclusion.Comment: 29 pages, no figure
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