3,517 research outputs found
Potentials between heavy-light mesons from lattice and inverse scattering theory
We extend our investigation of heavy-light meson-meson interactions to a
system consisting of a heavy-light meson and the corresponding antiparticle. An
effective potential is obtained from meson-antimeson Green-functions computed
in a quenched simulation with staggered fermions. Comparisons with a simulation
using an tree-level and tadpole improved gauge action and a full QCD
simulation show that lattice discretization errors and dynamical quarks have no
drastic influence. Calculations from inverse scattering theory propose a
similar shape for potentials.Comment: 3 pages, 5 EPS figures, Poster presented at "Lattice'97", to appear
in the proceeding
Illuminating interfaces between phases of a U(1) x U(1) gauge theory
We study reflection and transmission of light at the interface between
different phases of a U(1) x U(1) gauge theory. On each side of the interface,
one can choose a basis so that one generator is free (allowing propagation of
light), and the orthogonal one may be free, Higgsed, or confined. However, the
basis on one side will in general be rotated relative to the basis on the other
by some angle alpha. We calculate reflection and transmission coefficients for
both polarizations of light and all 8 types of boundary, for arbitrary alpha.
We find that an observer measuring the behavior of light beams at the boundary
would be able to distinguish 4 different types of boundary, and we show how the
remaining ambiguity arises from the principle of complementarity
(indistinguishability of confined and Higgs phases) which leaves observables
invariant under a global electric/magnetic duality transformation. We also
explain the seemingly paradoxical behavior of Higgs/Higgs and confined/confined
boundaries, and clarify some previous arguments that confinement must involve
magnetic monopole condensation.Comment: RevTeX, 12 page
Systematics of Gamow-Teller strengths in mid-fp-shell nuclei
We show that the presently available data on the Gamow-Teller (GT) strength
in mid-fp-shell nuclei are proportional to the product of the numbers of
valence protons and neutron holes in the full fp-shell. This observation leads
to important insights into the mechanism for GT quenching and to a simple
parametrization of the Gamow-Teller strengths important for electron capture by
fp-shell nuclei in the early stage of supernovae.Comment: 9 pages + 1 figure, Caltech preprint MAP-16
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
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
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.
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
Colour superconductivity in finite systems
In this paper we study the effect of finite size on the two-flavour colour
superconducting state. As well as restricting the quarks to a box, we project
onto states of good baryon number and onto colour singlets, these being
necessary restrictions on any observable ``quark nuggets''. We find that
whereas finite size alone has a significant effect for very small boxes, with
the superconducting state often being destroyed, the effect of projection is to
restore it again. The infinite-volume limit is a good approximation even for
quite small systems.Comment: 14 pages RevTeX4, 12 eps figure
Self-consistent parametrization of the two-flavor isotropic color-superconducting ground state
Lack of Lorentz invariance of QCD at finite quark chemical potential in
general implies the need of Lorentz non-invariant condensates for the
self-consistent description of the color-superconducting ground state.
Moreover, the spontaneous breakdown of color SU(3) in this state naturally
leads to the existence of SU(3) non-invariant non-superconducting expectation
values. We illustrate these observations by analyzing the properties of an
effective 2-flavor Nambu-Jona-Lasinio type Lagrangian and discuss the
possibility of color-superconducting states with effectively gapless fermionic
excitations. It turns out that the effect of condensates so far neglected can
yield new interesting phenomena.Comment: 16 pages, 3 figure
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