56 research outputs found
Thermally activated energy and critical magnetic fields of SmFeAsOF
Thermally activated flux flow and vortex glass transition of recently
discovered SmFeAsOF superconductor are studied in magnetic
fields up to 9.0 T. The thermally activated energy is analyzed in two analytic
methods, of which one is conventional and generally used, while the other is
closer to the theoretical description. The thermally activated energy values
determined from both methods are discussed and compared. In addition, several
critical magnetic fields determined from resistivity measurements are presented
and discussed.Comment: Accepted by Superconductor Science and Technolog. 5 page, 4 figure
Chiral Heat Wave and mixing of Magnetic, Vortical and Heat waves in chiral media
We show that a hot rotating fluid of relativistic chiral fermions possesses a
new gapless collective mode associated with coherent propagation of energy
density and chiral density waves along the axis of rotation. This mode, which
we call the Chiral Heat Wave, emerges due to a mixed gauge-gravitational
anomaly. At finite density the Chiral Heat Wave couples to the Chiral Vortical
Wave while in the presence of an external magnetic field it mixes with the
Chiral Magnetic Wave. The coupling of the Chiral Magnetic and Chiral Vortical
Waves is also demonstrated. We find that the coupled waves - which are coherent
fluctuations of the vector, axial and energy currents - have generally
different velocities compared to the velocities of the individual waves.Comment: 33 pages, 6 figures; v2: minor changes, published versio
Constraints on dark matter particles charged under a hidden gauge group from primordial black holes
In order to accommodate increasingly tighter observational constraints on
dark matter, several models have been proposed recently in which dark matter
particles are charged under some hidden gauge group. Hidden gauge charges are
invisible for the standard model particles, hence such scenarios are very
difficult to constrain directly. However black holes are sensitive to all gauge
charges, whether they belong to the standard model or not. Here, we examine the
constraints on the possible values of the dark matter particle mass and hidden
gauge charge from the evolution of primordial black holes. We find that the
existence of the primordial black holes with reasonable mass is incompatible
with dark matter particles whose charge to mass ratio is of the order of one.
For dark matter particles whose charge to mass ratio is much less than one, we
are able to exclude only heavy dark matter in the mass range of 10^(11) GeV -
10^(16) GeV. Finally, for dark matter particles whose charge to mass ratio is
much greater than one, there are no useful limits coming from primordial black
holes.Comment: accepted for publication in JCA
Chiral zero-mode for abelian BPS dipoles
We present an exact normalisable zero-energy chiral fermion solution for
abelian BPS dipoles. For a single dipole, this solution is contained within the
high temperature limit of the SU(2) caloron with non-trivial holonomy.Comment: 9 pages, 1 figure (in 2 parts), presented at the workshop on
"Confinement, Topology, and other Non-Perturbative Aspects of QCD", 21-27
Jan. 2002, Stara Lesna, Slovaki
Status of center dominance in various center gauges
We review arguments for center dominance in center gauges where vortex
locations are correctly identified. We introduce an appealing interpretation of
the maximal center gauge, discuss problems with Gribov copies, and a cure to
the problems through the direct Laplacian center gauge. We study correlations
between direct and indirect Laplacian center gauges.Comment: Presented by S. Olejnik at the NATO Advanced Research Workshop
"Confinement, Topology, and other Non-Perturbative Aspects of QCD", Jan.
21-27, 2002, Stara Lesna, Slovakia. 10 pages, 3 figures (8 EPS files), uses
crckapb.st
Towards Unquenched Holographic Magnetic Catalysis
We propose a string dual to the SU(Nc) N=4 SYM coupled to Nf massless
fundamental flavors in an external magnetic field. The flavors are introduced
by homogeneously smeared Nf D7-branes and the external magnetic field via a
non-trivial Kalb-Ramond B-field. Our solution is perturbative in a parameter
that counts the number of internal flavor loops. In the limit of vanishing
B-field the background reduces to the supersymmetric one obtained in
hep-th/0612118. We introduce an additional probe D7--brane and in the
supersymmetric limit of vanishing B-field perform a holographic renormalization
of its "on-shell" action. We consider also non-supersymmetric probes with fixed
worldvolume gauge field corresponding to a magnetic field coupled only to the
fundamental fields of the probe brane. We study the influence of the
backreacted flavors on the effect of dynamical mass generation. Qualitatively
the physical picture remains unchanged. In the next step we consider the case
when the magnetic field couples to both the backreacted and the probe
fundamental degrees of freedom. At sufficiently strong magnetic field the meson
spectrum signals an instability of the probe D7-brane, which we interpret as
reflecting an instability of the supergravity background.Comment: 33 pages, 5 figures, v2: minor corrections and references adde
Wilson Expansion of QCD Propagators at Three Loops: Operators of Dimension Two and Three
In this paper we construct the Wilson short distance operator product
expansion for the gluon, quark and ghost propagators in QCD, including
operators of dimension two and three, namely, A^2, m^2, m A^2, \ovl{\psi} \psi
and m^3. We compute analytically the coefficient functions of these operators
at three loops for all three propagators in the general covariant gauge. Our
results, taken in the Landau gauge, should help to improve the accuracy of
extracting the vacuum expectation values of these operators from lattice
simulation of the QCD propagators.Comment: 20 pages, no figure
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