14,006 research outputs found
Mass Terms in Effective Theories of High Density Quark Matter
We study the structure of mass terms in the effective theory for
quasi-particles in QCD at high baryon density. To next-to-leading order in the
expansion we find two types of mass terms, chirality conserving
two-fermion operators and chirality violating four-fermion operators. In the
effective chiral theory for Goldstone modes in the color-flavor-locked (CFL)
phase the former terms correspond to effective chemical potentials, while the
latter lead to Lorentz invariant mass terms. We compute the masses of Goldstone
bosons in the CFL phase, confirming earlier results by Son and Stephanov as
well as Bedaque and Sch\"afer. We show that to leading order in the coupling
constant there is no anti-particle gap contribution to the mass of
Goldstone modes, and that our results are independent of the choice of gauge.Comment: 22 pages, 4 figure
Superdense Matter
We review recent work on the phase structure of QCD at very high baryon
density. We introduce the phenomenon of color superconductivity and discuss the
use of weak coupling methods. We study the phase structure as a function of the
number of flavors and their masses. We also introduce effective theories that
describe low energy excitations at high baryon density. Finally, we study the
possibility of kaon condensation at very large baryon density.Comment: 13 pages, talk at ICPAQGP, Jaipur, India, Nov. 26-30, 2001; to appear
in the proceeding
Hydrodynamic fluctuations and the minimum shear viscosity of the dilute Fermi gas at unitarity
We study hydrodynamic fluctuations in a non-relativistic fluid. We show that
in three dimensions fluctuations lead to a minimum in the shear viscosity to
entropy density ratio as a function of the temperature. The minimum
provides a bound on which is independent of the conjectured bound in
string theory, , where is the entropy
density. For the dilute Fermi gas at unitarity we find \eta/s\gsim 0.2\hbar.
This bound is not universal -- it depends on thermodynamic properties of the
unitary Fermi gas, and on empirical information about the range of validity of
hydrodynamics. We also find that the viscous relaxation time of a hydrodynamic
mode with frequency diverges as , and that the shear
viscosity in two dimensions diverges as .Comment: 26 pages, 5 figures; final version to appear in Phys Rev
Binary Black Hole Coalescence in Semi-Analytic Puncture Evolution
Binary black-hole coalescence is treated semi-analytically by a novel
approach. Our prescription employs the conservative Skeleton Hamiltonian that
describes orbiting Brill-Lindquist wormholes (termed punctures in Numerical
Relativity) within a waveless truncation to the Einstein field equations [G.
Faye, P. Jaranowski and G. Sch\"afer, Phys. Rev. D {\bf 69}, 124029 (2004)]. We
incorporate, in a transparent Hamiltonian way and in Burke-Thorne gauge
structure, the effects of gravitational radiation reaction into the above
Skeleton dynamics with the help of 3.5PN accurate angular momentum flux for
compact binaries in quasi-circular orbits to obtain a Semi-Analytic Puncture
Evolution to model merging black-hole binaries. With the help of the TaylorT4
approximant at 3.5PN order, we perform a {\it first-order} comparison between
gravitational wave phase evolutions in Numerical Relativity and our approach
for equal-mass binary black holes. This comparison reveals that a modified
Skeletonian reactive dynamics that employs flexible parameters will be required
to prevent the dephasing between our scheme and Numerical Relativity, similar
to what is pursued in the Effective One Body approach. A rough estimate for the
gravitational waveform associated with the binary black-hole coalescence in our
approach is also provided.Comment: 16 pages, 5 figure
Phases of QCD at High Baryon Density
We review recent work on the phase structure of QCD at very high baryon
density. We introduce the phenomenon of color superconductivity and discuss how
the quark masses and chemical potentials determine the structure of the
superfluid quark phase. We comment on the possibility of kaon condensation at
very high baryon density and study the competition between superfluid, density
wave, and chiral crystal phases at intermediate density.Comment: 15 pages. To appear in the proceedings of the ECT Workshop on Neutron
Star Interiors, Trento, Italy, June 200
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