2,855 research outputs found
Competition of Color Ferromagnetic and Superconductive States in a Quark-Gluon System
The possibility of color ferromagnetism in an SU(2) gauge field model is
investigated. The conditions allowing a stable color ferromagnetic state of the
quark system in the chromomagnetic field occupying small domains are
considered. A phase transition between this state and the color superconducting
state is considered. The effect of finite temperature is analyzed.Comment: 21 pages, 4 Postscript figure
Exotic solutions in string theory
Solutions of classical string theory, correspondent to the world sheets,
mapped in Minkowsky space with a fold, are considered. Typical processes for
them are creation of strings from vacuum, their recombination and annihilation.
These solutions violate positiveness of square of mass and Regge condition. In
quantum string theory these solutions correspond to physical states |DDF>+|sp>
with non-zero spurious component.Comment: accepted in Il Nuovo Cimento A for publication in 199
Molecular hydrogen absorption systems in Sloan Digital Sky Survey
We present a systematic search for molecular hydrogen absorption systems at
high redshift in quasar spectra from the Sloan Digital Sky Survey (SDSS) II
Data Release 7 and SDSS-III Data Release 9. We have selected candidates using a
modified profile fitting technique taking into account that the Ly
forest can effectively mimic H absorption systems at the resolution of SDSS
data. To estimate the confidence level of the detections, we use two methods: a
Monte-Carlo sampling and an analysis of control samples. The analysis of
control samples allows us to define regions of the spectral quality parameter
space where H absorption systems can be confidently identified. We find
that H absorption systems with column densities
can be detected in only less than 3% of SDSS quasar spectra. We estimate the
upper limit on the detection rate of saturated H absorption systems () in Damped Ly- (DLA) systems to be about 7%. We
provide a sample of 23 confident H absorption system candidates that would
be interesting to follow up with high resolution spectrographs. There is a
1 color excess and non-significant extinction excess
in quasar spectra with an H candidate compared to standard DLA-bearing
quasar spectra. The equivalent widths (EWs) of C II, Si II and Al III (but not
Fe II) absorptions associated with H candidate DLAs are larger compared to
standard DLAs. This is probably related to a larger spread in velocity of the
absorption lines in the H bearing sample.Comment: 17 pages, 17 figures, accepted for publication in MNRA
Inhomogeneous charged pion condensation phenomenon in the NJL model with quark number and isospin chemical potentials
The properties of two-flavored massive Nambu--Jona-Lasinio model in
(1+1)-dimensional spacetime are investigated in the presence of isospin and
quark number chemical potentials. The consideration is performed in the
large- limit, where is the number of colored quarks. It is shown in
the framework of this model that charged pion condensation phenomenon of dense
quark/hadron isotopically asymmetric matter is rather a spatially inhomogeneous
than a homogeneous one.Comment: 11 pages, 8 figures; version accepted for publication in PRD. arXiv
admin note: text overlap with arXiv:1106.2928, arXiv:1102.407
New phase structure of the Nambu -- Jona - Lasinio model at nonzero chemical potential
It is shown that in the Nambu -- Jona - Lasinio model at nonzero chemical
potential there are two different massive phases with spontaneously broken
chiral symmetry. In one of them particle density is identically zero, in
another phase it is not equal to zero. The transition between phases is a phase
transition of the second order.Comment: 8 pages, LaTeX, no figures
Partial covering of emission regions of Q 0528-250 by intervening H clouds
We present an analysis of the molecular hydrogen absorption system at z = 2.811 in the spectrum of the blazar Q0528-250. We demonstrate that the
molecular cloud does not cover the background source completely. The partial
coverage reveals itself as a residual flux in the bottom of saturated H_2
absorption lines. This amounts to about (2.220.54)% of the continuum and
does not depend on the wavelength. This value is small and it explains why this
effect has not been detected in previous studies of this quasar spectrum.
However, it is robustly detected and significantly higher than the zero flux
level in the bottom of saturated lines of the Ly-alpha forest,
(-0.210.22)%. The presence of the residual flux could be caused by
unresolved quasar multicomponents, by light scattered by dust, and/or by
jet-cloud interaction. The H absorption system is very well described by a
two-component model without inclusion of additional components when we take
partial coverage into account. The derived total column densities in the H
absorption components A and B are logN(H)[cm] = 18.100.02 and
17.820.02, respectively. HD molecules are present only in component B.
Given the column density, logN(HD)= 13.330.02, we find
N(HD)/2N(H)=(1.480.10)x10, significantly lower than previous
estimations. We argue that it is crucial to take into account partial coverage
effects for any analysis of H bearing absorption systems, in particular
when studying the physical state of high-redshift interstellar medium.Comment: Accepted for MNRA
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