1,554 research outputs found
Bound diquarks and their Bose-Einstein condensation in strongly coupled quark matter
We explore the formation of diquark molecules and their Bose-Einstein
condensation (BEC) in the phase diagram of three-flavor quark matter at nonzero
temperature, T, and quark chemical potential, mu. Using a quark model with a
four-fermion interaction, we identify possible diquark excitations as poles of
the microscopically computed diquark propagator. The quark masses are obtained
by solving a dynamical equation for the chiral condensate and are found to
determine the stability of the diquark excitations. The stability of diquark
excitations is investigated in the T-mu plane for different values of the
diquark coupling strength. We find that bound diquark molecules appear at small
quark chemical potentials at intermediate coupling and that BEC of non-strange
diquark molecules occurs if the attractive interaction between quarks is
sufficiently strong.Comment: 7 pages, 6 figure
Ground State Phase Diagram of S=1 XXZ Chains with Uniaxial Single-Ion-Type Anisotropy
One dimensional S=1 XXZ chains with uniaxial single-ion-type anisotropy are
studied by numerical exact diagonalization of finite size systems. The
numerical data are analyzed using conformal field theory, the level
spectroscopy, phenomenological renormalization group and finite size scaling
method. We thus present the first quantitatively reliable ground state phase
diagram of this model. The ground states of this model contain the Haldane
phase, large-D phase, N\'{e}el phase, two XY phases and the ferromagnetic
phase. There are four different types of transitions between these phases: the
Brezinskii-Kosterlitz-Thouless type transitions, the Gaussian type transitions,
the Ising type transitions and the first order transitions. The location of
these critical lines are accurately determined.Comment: 8 pages, 19 figure
Bose-Einstein condensation of diquark molecules in three-flavor quark matter
We study the phase diagram of strongly interacting matter with three quark
flavors at low and intermediate densities and non-zero temperatures in the
framework of an NJL-type model with four-point interactions. At large
densities, when the interactions are weak due to asymptotic freedom, quarks
form loosely bound Cooper pairs. However, when the density decreases,
interactions become stronger and quark Cooper pairs transform smoothly into
tightly bound diquark molecules. We find that such molecules are stable at low
density and temperature and that they dissociate above a temperature of the order of the chiral phase transition temperature
MeV. We also explore the conditions under which these molecules undergo
Bose-Einstein condensation (BEC). We find that BEC is only possible if we
increase the attractive interaction in the diquark channel to (probably
unrealistically) large values.Comment: 8 pages, 3 figures, proceedings of YKIS 2006 "New Frontiers in QCD
String Field Theory from IIB Matrix Model
We derive Schwinger-Dyson equations for the Wilson loops of a type IIB matrix
model. Superstring coordinates are introduced through the construction of the
loop space. We show that the continuum limit of the loop equation reproduces
the light-cone superstring field theory of type IIB superstring in the large-N
limit. We find that the interacting string theory can be obtained in the double
scaling limit as it is expected.Comment: 21 pages, Latex, 1 figur
Field-induced magnetic ordering in the Haldane system PbNi2V2O8
The Haldane system PbNi2V2O8 was investigated by the temperature dependent
magnetization M(T) measurements at fields higher than H_c, with H_c the
critical fields necessary to close the Haldane gap. It is revealed that M(T)
for H > H_c exhibits a cusp-like minimum at T_{min}, below which M(T) increases
with decreasing T having a convex curve. These features have been observed for
both and , with c-axis being parallel to the chain.
These data indicate the occurrence of field-induced magnetic ordering around
T_{min}. Phase boundaries for and do not cross each
other, consistent with the theoretical calculation for negative single-ion
anisotropy D.Comment: 3 figures, submitted to Phys. Rev.
Phase diagram of S=1 XXZ chain with next-nearest neighbor interaction
The one dimensional S=1 XXZ model with next-nearest-neighbor interaction
and Ising-type anisotropy is studied by using a numerical
diagonalization technique. We discuss the ground state phase diagram of this
model numerically by the twisted-boundary-condition level spectroscopy method
and the phenomenological renormalization group method, and analytically by the
spin wave theory. We determine the phase boundaries among the XY phase, the
Haldane phase, the ferromagnetic phase and the N\'{e}el phase, and then we
confirm the universality class. Moreover, we map this model onto the non-linear
model and analyze the phase diagram in the -1 and
1 region by using the renormalization group method.Comment: 18 pages, 10 figure
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