113,204 research outputs found
Study of QCD critical point using canonical ensemble method
The existence of the QCD critical point at non-zero baryon density is not
only of great interest for experimental physics but also a challenge for the
theory. We use lattice simulations based on the canonical ensemble method to
explore the finite baryon density region and look for the critical point. We
scan the phase diagram of QCD with three degenerate quark flavors using clover
fermions with on lattices. We measure the
baryon chemical potential as we increase the density and we see the
characteristic "S-shape" that signals the first order phase transition. We
determine the phase boundary by Maxwell construction and report our preliminary
results for the location of critical point.Comment: 2 pages, 2 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
Critical point of QCD from lattice simulations in the canonical ensemble
A canonical ensemble algorithm is employed to study the phase diagram of QCD using lattice simulations. We lock in the desired quark number sector
using an exact Fourier transform of the fermion determinant. We scan the phase
space below and look for an S-shape structure in the chemical potential,
which signals the coexistence phase of a first order phase transition in finite
volume. Applying Maxwell construction, we determine the boundaries of the
coexistence phase at three temperatures and extrapolate them to locate the
critical point. Using an improved gauge action and improved Wilson fermions on
lattices with a spatial extent of 1.8 \fm and quark masses close to that of
the strange, we find the critical point at and baryon
chemical potential .Comment: 5 pages, 7 figures, references added, published versio
Eta absorption by mesons
Using the chiral Lagrangian with hidden local
symmetry, we evaluate the cross sections for the absorption of eta meson () by pion (), rho (), omega (), kaon (), and kaon
star () in the tree-level approximation. With empirical masses and
coupling constants as well as reasonable values for the cutoff parameter in the
form factors at interaction vertices, we find that most cross sections are less
than 1 mb, except the reactions ,
, , and , which are a few mb, and the reactions and , which are more than 10 mb. Including these reactions in a kinetic model
based on a schematic hydrodynamic description of relativistic heavy ion
collisions, we find that the abundance of eta mesons likely reaches chemical
equilibrium with other hadrons in nuclear collisions at the Relativistic Heavy
Ion Collider.Comment: 29 pages, 10 figures, version to appear in Nucl. Phys.
Parametric cooling of a degenerate Fermi gas in an optical trap
We demonstrate a novel technique for cooling a degenerate Fermi gas in a
crossed-beam optical dipole trap, where high-energy atoms can be selectively
removed from the trap by modulating the stiffness of the trapping potential
with anharmonic trapping frequencies. We measure the dependence of the cooling
effect on the frequency and amplitude of the parametric modulations. It is
found that the large anharmonicity along the axial trapping potential allows to
generate a degenerate Fermi gas with anisotropic energy distribution, in which
the cloud energy in the axial direction can be reduced to the ground state
value
Matrix Model in a Class of Time Dependent Supersymmetric Backgrounds
We discuss the matrix model in a class of 11D time dependent supersymmetric
backgrounds as obtained in hep-th/0508191 . We construct the matrix model
action through the matrix regularization of the membrane action in the
background. We show that the action is exact to all order of fermionic
coordinates. Furthermore We discuss the fuzzy sphere solutions in this
background.Comment: 16 pages, 4 figures; references added, modifications of some comments
in introduction, version to appear in PL
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