3,458 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
Magnetic Susceptibility of the Quark Condensate and Polarization from Chiral Models
We compute the magnetic susceptibility of the quark condensate and the
polarization of quarks at zero temperature and in a uniform magnetic
background. Our theoretical framework consists of two chiral models that allow
to treat self-consistently the spontaneous breaking of chiral symmetry: the
linear model coupled to quarks, dubbed quark-meson model, and the
Nambu-Jona-Lasinio model. We also perform analytic estimates of the same
quantities within the renormalized quark-meson model, both in the regimes of
weak and strong fields. Our numerical results are in agreement with the recent
literature; moreover, we confirm previous Lattice findings, related to the
saturation of the polarization at large fields.Comment: 13 pages, 4 figure
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
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