10,214 research outputs found
Chromomagnetic instability in two-flavor quark matter at nonzero temperature
We calculate the effective potential of the 2SC/g2SC phases including vector
condensates () and study the gluonic phase and the
single plane-wave Larkin-Ovchinnikov-Fulde-Ferrell state at nonzero
temperature. Our analysis is performed within the framework of the gauged
Nambu--Jona-Lasinio model. We compute potential curvatures with respect to the
vector condensates and investigate the temperature dependence of the Meissner
masses squared of gluons of color 4--7 and 8 in the neutral 2SC/g2SC phases.
The phase diagram is presented in the plane of temperature and coupling
strength. The unstable regions for gluons 4--7 and 8 are mapped out on the
phase diagram. We find that, apart from the case of strong coupling, the
2SC/g2SC phases at low temperatures are unstable against the vector
condensation until the temperature reaches tens of MeV.Comment: 10 pages, 10 figures, revisions to text, published in Phys. Rev.
Analytical and numerical evaluation of the Debye and Meissner masses in dense neutral three-flavor quark matter
We calculate the Debye and Meissner masses and investigate chromomagnetic
instability associated with the gapless color superconducting phase changing
the strange quark mass and the temperature . Based on the analytical
study, we develop a computational procedure to derive the screening masses
numerically from curvatures of the thermodynamic potential. When the
temperature is zero, from our numerical results for the Meissner masses, we
find that instability occurs for and gluons entirely in the gapless
color-flavor locked (gCFL) phase, while the Meissner masses are real for ,
, , and until exceeds a certain value that is larger than
the gCFL onset. We then handle mixing between color-diagonal gluons ,
, and photon , and clarify that, among three eigenvalues of the
mass squared matrix, one remains positive, one is always zero because of an
unbroken U(1)_\tilde{Q} symmetry, and one exhibits chromomagnetic instability
in the gCFL region. We also examine the temperature effects that bring
modifications into the Meissner masses. The instability found at large
for , , , and persists at finite into the -quark
color superconducting (uSC) phase which has - and - but no -
quark pairing and also into the two-flavor color superconducting (2SC) phase
characterized by - quark pairing only. The and instability
also goes into the uSC phase, but the 2SC phase has no instability for ,
, and . We map the unstable region for each gluon onto the phase
diagram as a function of and .Comment: 17 pages, 18 figure
Neutral Larkin--Ovchinnikov--Fulde--Ferrell state and chromomagnetic instability in two-flavor dense QCD
In two-flavor dense quark matter, we describe the dynamics in the single
plane wave Larkin--Ovchinnikov--Fulde--Ferrell (LOFF) state satisfying the
color and electric neutrality conditions. We find that because the neutral LOFF
state itself suffers from a chromomagnetic instability in the whole region
where it coexists with the (gapped/gapless) two-flavor superconducting
(2SC/g2SC) phases, it cannot cure this instability in those phases. This is
unlike the recently revealed gluonic phase which seems to be able to resolve
this problem.Comment: Revtex4, 5 pages, 3 figures, clarifications added, to appear in
Phys.Rev.Let
Collective excitations, instabilities, and ground state in dense quark matter
We study the spectrum of light plasmons in the (gapped and gapless)
two-flavor color superconducting phases and its connection with the
chromomagnetic instabilities and the structure of the ground state. It is
revealed that the chromomagnetic instabilities in the 4-7th and 8th gluonic
channels correspond to two very different plasmon spectra. These spectra lead
us to the unequivocal conclusion about the existence of gluonic condensates
(some of which can be spatially inhomogeneous) in the ground state. We also
argue that spatially inhomogeneous gluonic condensates should exist in the
three-flavor quark matter with the values of the mass of strange quark
corresponding to the gapless color-flavor locked state.Comment: Revtex, 5 pages, 4 figures, two figures and clarifications added, to
appear in PRD (Rapid Communications
Gluonic phases, vector condensates, and exotic hadrons in dense QCD
We study the dynamics in phases with vector condensates of gluons (gluonic
phases) in dense two-flavor quark matter. These phases yield an example of
dynamics in which the Higgs mechanism is provided by condensates of gauge (or
gauge plus scalar) fields. Because vacuum expectation values of spatial
components of vector fields break the rotational symmetry, it is naturally to
have a spontaneous breakdown both of external and internal symmetries in this
case. In particular, by using the Ginzburg-Landau approach, we establish the
existence of a gluonic phase with both the rotational symmetry and the
electromagnetic U(1) being spontaneously broken. In other words, this phase
describes an anisotropic medium in which the color and electric
superconductivities coexist. It is shown that this phase corresponds to a
minimum of the Ginzburg-Landau potential and, unlike the two-flavor
superconducting (2SC) phase, it does not suffer from the chromomagnetic
instability. The dual (confinement) description of its dynamics is developed
and it is shown that there are light exotic vector hadrons in the spectrum,
some of which condense. Because most of the initial symmetries in this system
are spontaneously broken, its dynamics is very rich.Comment: 33 pages, RevTeX; v.2: Published PRD versio
Neutrino emission from compact stars and inhomogeneous color superconductivity
We discuss specific heat and neutrino emissivity due to direct Urca processes
for quark matter in the color superconductive Larkin-Ovchinnikov-Fulde-Ferrell
(LOFF) phase of Quantum-Chromodynamics. We assume that the three light quarks
are in a color and electrically neutral state and interact by a four
fermion Nambu-Jona Lasinio coupling. We study a LOFF state characterized by a
single plane wave for each pairing. From the evaluation of neutrino emissivity
and fermionic specific heat, the cooling rate of simplified models of compact
stars with a quark core in the LOFF state is estimated.Comment: 16 pages, 5 figures, revtex4 style. Version accepted for publication
in Phys. Rev.
Photons in gapless color-flavor-locked quark matter
We calculate the Debye and Meissner masses of a gauge boson in a material
consisting of two species of massless fermions that form a condensate of Cooper
pairs. We perform the calculation as a function of temperature, for the cases
of neutral Cooper pairs and charged Cooper pairs, and for a range of parameters
including gapped quaisparticles, and ungapped quasiparticles with both
quadratic and linear dispersion relations at low energy.
Our results are relevant to the behavior of photons and gluons in the gapless
color-flavor-locked phase of quark matter. We find that the photon's Meissner
mass vanishes, and the Debye mass shows a non-monotonic temperature dependence,
and at temperatures of order the pairing gap it drops to a minimum value of
order sqrt(alpha) times the quark chemical potential. We confirm previous
claims that at zero temperature an imaginary Meissner mass can arise from a
charged gapless condensate, and we find that at finite temperature this can
also occur for a gapped condensate.Comment: 22 pages, LaTeX; expanded discussion of temperature dependenc
Color-flavor locked superconductor in a magnetic field
We study the effects of moderately strong magnetic fields on the properties
of color-flavor locked color superconducting quark matter in the framework of
the Nambu-Jona-Lasinio model. We find that the energy gaps, which describe the
color superconducting pairing as well as the magnetization, are oscillating
functions of the magnetic field. Also, we observe that the oscillations of the
magnetization can be so strong that homogeneous quark matter becomes metastable
for a range of parameters. We suggest that this points to the possibility of
magnetic domains or other types of magnetic inhomogeneities in the quark cores
of magnetars.Comment: 12 pages, 3 figures. Version accepted for publication in Phys. Rev.
Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE
We present initial results of a deep near-IR spectroscopic survey covering
the 15 fields of the Keck Baryonic Structure Survey (KBSS) using MOSFIRE on the
Keck 1 telescope, focusing on a sample of 251 galaxies with redshifts 2.0< z <
2.6, star-formation rates 2 < SFR < 200 M_sun/yr, and stellar masses 8.6 <
log(M*/M_sun) < 11.4, with high-quality spectra in both H- and K-band
atmospheric windows. We show unambiguously that the locus of z~2.3 galaxies in
the "BPT" nebular diagnostic diagram exhibits a disjoint, yet similarly tight,
relationship between the ratios [NII]6585/Halpha and [OIII]/Hbeta as compared
to local galaxies. Using photoionization models, we argue that the offset of
the z~2.3 locus relative to z~ 0 is explained by a combination of harder
ionizing radiation field, higher ionization parameter, and higher N/O at a
given O/H than applies to most local galaxies, and that the position of a
galaxy along the z~2.3 star-forming BPT locus is surprisingly insensitive to
gas-phase oxygen abundance. The observed nebular emission line ratios are most
easily reproduced by models in which the net ionizing radiation field resembles
a blackbody with effective temperature T_eff = 50000-60000 K and N/O close to
the solar value at all O/H. We critically assess the applicability of
commonly-used strong line indices for estimating gas-phase metallicities, and
consider the implications of the small intrinsic scatter in the empirical
relationship between excitation-sensitive line indices and stellar mass (i.e.,
the "mass-metallicity" relation), at z~2.3.Comment: 41 pages, 25 figures, accepted for publication in the Astrophysical
Journal. Version with full-resolution figures available at
http://www.astro.caltech.edu/~ccs/mos_bpt_submit.pd
Competition of ferromagnetic and antiferromagnetic spin ordering in nuclear matter
In the framework of a Fermi liquid theory it is considered the possibility of
ferromagnetic and antiferromagnetic phase transitions in symmetric nuclear
matter with Skyrme effective interaction. The zero temperature dependence of
ferromagnetic and antiferromagnetic spin polarization parameters as functions
of density is found for SkM, SGII effective forces. It is shown that in the
density domain, where both type of solutions of self--consistent equations
exist, ferromagnetic spin state is more preferable than antiferromagnetic one.Comment: 9p., 3 figure
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