3,388 research outputs found
Illuminating Dense Quark Matter
We imagine shining light on a lump of cold dense quark matter, in the CFL
phase and therefore a transparent insulator. We calculate the angles of
reflection and refraction, and the intensity of the reflected and refracted
light. Although the only potentially observable context for this phenomenon
(reflection of light from and refraction of light through an illuminated quark
star) is unlikely to be realized, our calculation casts new light on the old
idea that confinement makes the QCD vacuum behave as if filled with a
condensate of color-magnetic monopoles.Comment: 4 pages, 1 figur
The D234 action for light quarks
We investigate a new light fermion action (the ``D234'' action), which is
accurate up to \O(a^3) and tadpole-improved \O(a \alpha_s) errors. Using
D234 with Symanzik- and tadpole-improved glue we find evidence that continuum
results for the quenched hadron spectrum (pion, rho and nucleon) can be
obtained on coarse lattices.Comment: Latex, 4 pages, submitted to Lattice '95 proceeding
Chiral and Color-superconducting Phase Transitions with Vector Interaction in a Simple Model (Addenda)
In the preceding paper(Prog.Theor.Phys.108(2002)929 or hep-ph/0207255), we
have shown that the critical line of the first order chiral transition of QCD
can have two endpoints. In this addendum, we elucidate the mechanism to realize
the two-endpoint structure in the QCD phase diagram and argue the robustness
for the appearance of such an interesting phase structure
Controlled Ecological Life Support System: Use of Higher Plants
Results of two workshops concerning the use of higher plants in Controlled Ecological Life Support Systems (CELSS) are summarized. Criteria for plant selection were identified from these categories: food production, nutrition, oxygen production and carbon dioxide utilization, water recycling, waste recycling, and other morphological and physiological considerations. Types of plant species suitable for use in CELSS, growing procedures, and research priorities were recommended. Also included are productivity values for selected plant species
Color-Neutral Superconducting Quark Matter
We investigate the consequences of enforcing local color neutrality on the
color superconducting phases of quark matter by utilizing the
Nambu-Jona-Lasinio model supplemented by diquark and the t'Hooft six-fermion
interactions. In neutrino free matter at zero temperature, color neutrality
guarantees that the number densities of u, d, and s quarks in the
Color-Flavor-Locked (CFL) phase will be equal even with physical current quark
masses. Electric charge neutrality follows as a consequence and without the
presence of electrons. In contrast, electric charge neutrality in the less
symmetric 2-flavor superconducting (2SC) phase with ud pairing requires more
electrons than the normal quark phase. The free energy density cost of
enforcing color and electric charge neutrality in the CFL phase is lower than
that in the 2SC phase, which favors the formation of the CFL phase. With
increasing temperature and neutrino content, an unlocking transition occurs
from the CFL phase to the 2SC phase with the order of the transition depending
on the temperature, the quark and lepton number chemical potentials. The
astrophysical implications of this rich structure in the phase diagram,
including estimates of the effects from Goldstone bosons in the CFL phase, are
discussed.Comment: 20 pages, 4 figures; version to appear in Phys. Rev.
Modern compact star observations and the quark matter EoS
A hybrid equation of state for dense matter is presented that satisfies
phenomenological constraints from modern compact star observations which
indicate high maximum masses of about 2 M_sun and large radii of R> 12 km. The
corresponding isospin symmetric equation of state is consistent with flow data
analyses of heavy-ion collisions. The transition from nuclear to two-flavor
color superconducting quark matter at n approximately 0.55 fm^{-3} is almost a
crossover.Comment: 2 pages, 2 figures; Proceedings of the Erice School on 'Radioactive
Beams, Nuclear Dynamics and Astrophysics' to be published in 'Prog. Part.
Nucl. Phys.
Quark matter in compact stars?
Ozel, in a recent reanalysis of EXO 0748-676 observational data
(astro-ph/0605106), concluded that quark matter probably does not exist in the
center of compact stars. We show that the data is actually consistent with the
presence of quark matter in compact stars.Comment: 4 pages, LaTeX; New title and overall rewrite to reflect version
published in Nature. Conclusions unchange
On finite-density QCD at large Nc
Deryagin, Grigoriev, and Rubakov (DGR) have shown that in finite-density QCD
at infinite Nc the Fermi surface is unstable with respect to the formation of
chiral waves with wavenumber twice the Fermi momentum, while the BCS
instability is suppressed. We show here that at large, but finite Nc, the DGR
instability only occurs in a finite window of chemical potentials from above
Lambda_QCD to mu_critical = exp(gamma ln^2 Nc + O(ln Nc ln ln Nc))Lambda_QCD,
where gamma = 0.02173. Our analysis shows that, at least in the perturbative
regime, the instability occurs only at extremely large Nc, Nc > 1000 Nf, where
Nf is the number of flavors. We conclude that the DGR instability is not likely
to occur in QCD with three colors, where the ground state is expected to be a
color superconductor. We speculate on possible structure of the ground state of
finite-density QCD with very large Nc.Comment: 13 pages, 5 figures, 3 figures drawn using PicTe
Aspects of the Color Flavor Locking phase of QCD in the Nambu-Jona Lasinio approximation
We study two aspects of the CFL phase of QCD in the NJL approximation. The
first one is the issue of the dependence on \mu of the ultraviolet cutoff in
the gap equation, which is solved allowing a running coupling constant. The
second one is the dependence of the gap on the strange quark mass; using the
high density effective theory we perform an expansion in the parameter
(m_s/\mu)^2 after checking that its numerical validity is very good already at
first order.Comment: LaTeX file, 6 figure
Mass-Induced Crystalline Color Superconductivity
We demonstrate that crystalline color superconductivity may arise as a result
of pairing between massless quarks and quarks with nonzero mass m_s. Previous
analyses of this phase of cold dense quark matter have all utilized a chemical
potential difference \delta\mu to favor crystalline color superconductivity
over ordinary BCS pairing. In any context in which crystalline color
superconductivity occurs in nature, however, it will be m_s-induced. The effect
of m_s is qualitatively different from that of \delta\mu in one crucial
respect: m_s depresses the value of the BCS gap \Delta_0 whereas \delta\mu
leaves \Delta_0 unchanged. This effect in the BCS phase must be taken into
account before m_s-induced and \delta\mu-induced crystalline color
superconductivity can sensibly be compared.Comment: 12 pages, 4 figures. v2: very small change onl
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