128 research outputs found
Stability of color-flavor locked strangelets
The stability of color-flavor locked (CFL) strangelets is studied in the
three-flavor Nambu--Jona-Lasinio model. We consider all quark flavors to be
massless, for simplicity. By making use of the multiple reflection expansion,
we explicitly take into account finite size effects and formulate the
thermodynamic potential for CFL strangelets. We find that the CFL gap could be
large enough so that the energy per baryon number of CFL strangelets is greatly
affected. In addition, if the quark-quark coupling constant is larger than a
certain critical value, there is a possibility of finding absolutely stable CFL
strangelets.Comment: 7 pages, 3 figures, to appear in Int. J. Mod. Phys.
Dense quark matter in compact stars
The densest predicted state of matter is colour-superconducting quark matter,
in which quarks near the Fermi surface form a condensate of Cooper pairs. This
form of matter may well exist in the core of compact stars, and the search for
signatures of its presence is an ongoing enterprise. Using a bag model of quark
matter, I discuss the effects of colour superconductivity on the mass-radius
relationship of compact stars, showing that colour superconducting quark matter
can occur in compact stars at values of the bag constant where ordinary quark
matter would not be allowed. The resultant ``hybrid'' stars with colour
superconducting quark matter interior and nuclear matter surface have masses in
the range 1.3-1.6 Msolar and radii 8-11 km. Once perturbative corrections are
included, quark matter can show a mass-radius relationship very similar to that
of nuclear matter, and the mass of a hybrid star can reach 1.8 \Msolar.Comment: 11 pages, for proceedings of SQM 2003 conference; references added,
abstract reworde
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
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
A diagrammatic derivation of the meson effective masses in the neutral color-flavor-locked phase of Quantum Chromodynamics
We offer a diagrammatic derivation of the effective masses of the axial
flavor excitations in the electrical and color neutral CFL phase of QCD. In
particular we concentrate on the excitations with the quantum numbers of the
kaons: we show how their effective chemical potentials, responsible of their
Bose-Einstein condensation and found previously on the basis of pure symmetry
arguments, arise at the microscopic level by loop effects. We perform also the
numerical evaluation of the relevant loops in the whole CFL regime
, showing the existence of the enhancement of the
kaon condensation with respect to the lowest order result. Finally we discuss
the role of electrical and color neutrality in the microscopic calculation.Comment: 10 pages, 2 figures, RevTeX4 style. Version accepted for publication
on JHEP. Some minor change in the tex
The Stability of Strange Star Crusts and Strangelets
We construct strangelets, taking into account electrostatic effects,
including Debye screening, and arbitrary surface tension sigma of the interface
between vacuum and quark matter. We find that there is a critical surface
tension sigma_crit below which large strangelets are unstable to fragmentation
and below which quark star surfaces will fragment into a crystalline crust made
of charged strangelets immersed in an electron gas. We derive a
model-independent relationship between sigma_crit and two parameters that
characterize any quark matter equation of state. For reasonable model equations
of state, we find sigma_crit typically of order a few MeV/fm^2. If sigma <=
sigma_crit, the size-distribution of strangelets in cosmic rays could feature a
peak corresponding to the stable strangelets that we construct.Comment: 11 pages, LaTe
Prelude to Compressed Baryonic Matter
This is intended to appear as the introduction to "The CBM Physics Book:
compressed baryonic matter in laboratory experiments" (ed. B. Friman, C.
H\"ohne, S. Leupold, J. Knoll, J. Randrup, R. Rapp, P. Senger), to be published
by Springer. At the end there is a new proposal for numerically tractable
models of interacting many-body systems.Comment: 12 pages, to appear in "The CBM Book: compressed baryonic matter in
laboratory experiments
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
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