846 research outputs found
Vector interaction, charge neutrality and multiple chiral critical point structures
We investigate the combined effect of the repulsive vector interaction and
the positive electric chemical potential on the chiral phase transition by
considering neutral color superconductivity (CSC). The chiral condensate,
diquark condensate and quark number densities are solved in both two-flavor and
two-plus-one-flavor Nambu-Jona-Lasinio(NJL) models with the so called
Kobayashi-Maskawa-'t Hooft term under the charge neutrality constraint. We
demonstrate that multiple chiral critical-point structures always exist in the
NJL model within the self-consistent mean-field approximation and the number of
chiral critical points can vary from zero to four, which is dependent on the
magnitudes of vector interaction and the diquark coupling. The difference
between the dynamical chemical potentials induced by vector interaction for u
and d quarks can effectively reduce the Fermi sphere disparity between the two
flavors of diquark paring. Thus the vector interaction works to significantly
suppress the unstable region associated with chromomagnetic instability in the
phase of neutral asymmetric homogenous CSC.Comment: version for Phys. Rev.
Precursor of Color Superconductivity in Hot Quark Matter
We investigate possible precursory phenomena of color superconductivity in
quark matter at finite temperature T with use of a simple Nambu-Jona-Lasinio
model. It is found that the fluctuating pair field exists with a prominent
strength even well above the critical temperature T_c. We show that the
collective pair field has a complex energy located in the second Riemann sheet,
which approaches the origin as T is lowered to T_c. We discuss the possible
relevance of the precursor to the observables to be detected in heavy ion
collisions.Comment: 5 pages, 3 figures, version to appear in Phys. Rev. D. Discussions
are enlarged on the physical origin of the large fluctuation of the pair
field and its phenomenological consequences. References are adde
Influence of pure-dephasing by phonons on exciton-photon interfaces: Quantum microscopic theory
We have developed a full quantum microscopic theory to analyze the time
evolution of transversal and longitudinal components of an exciton-single
photon system coupled to bulk acoustic phonons. These components are subjected
to two decay processes. One is radiative relaxation and the other is
pure-dephasing due to exciton-phonon interaction. The former results in a decay
with an exponent linear to time, while the latter causes a faster initial decay
than the radiative decay. We analyzed the dependence of the components on the
duration of the input one-photon pulse, temperature, and radiative relaxation
rates. Such a quantitative analysis is important for the developments of
atom-photon interfaces which enable coherent transfer of quantum information
between photons and atomic systems. We found that, for a GaAs spherical quantum
dot in which the exciton interacts with bulk phonons, the maximal probability
of the excited state can be increased up to 75 %. This probability can be
considered as the efficiency for quantum information transfer from photon to
exciton.Comment: 9pages, 5figure
Roles of axial anomaly on neutral quark matter with color superconducting phase
We investigate effects of the axial anomaly term with a chiral-diquark
coupling on the phase diagram within a two-plus-one-flavor Nambu-Jona-Lasinio
(NJL) model under the charge-neutrality and -equilibrium constraints. We
find that when such constraints are imposed, the new anomaly term plays a quite
similar role as the vector interaction does on the phase diagram, which the
present authors clarified in a previous work. Thus, there appear several types
of phase structures with multiple critical points at low temperature ,
although the phase diagrams with intermediate- critical point(s) are never
realized without these constraints even within the same model Lagrangian. This
drastic change is attributed to an enhanced interplay between the chiral and
diquark condensates due to the anomaly term at finite temperature; the u-d
diquark coupling is strengthened by the relatively large chiral condensate of
the strange quark through the anomaly term, which in turn definitely leads to
the abnormal behavior of the diquark condensate at finite , inherent to the
asymmetric quark matter. We note that the critical point from which the
crossover region extends to zero temperature appears only when the strength of
the vector interaction is larger than a critical value. We also show that the
chromomagnetic instability of the neutral asymmetric homogenous two-flavor
color superconducting(2CSC) phase is suppressed and can be even completely
cured by the enhanced diquark coupling due to the anomaly term and/or by the
vector interaction.Comment: 15 pages, 5 figures, typos corrected, new references and some
statements adde
Chiral and Color-superconducting Phase Transitions with Vector Interaction in a Simple Model (Addenda)
In the preceding paper(Prog.Theor.Phys.108(2002)929 or hep-ph/0207255), we
have shown that the critical line of the first order chiral transition of QCD
can have two endpoints. In this addendum, we elucidate the mechanism to realize
the two-endpoint structure in the QCD phase diagram and argue the robustness
for the appearance of such an interesting phase structure
Dynamical Reduction of Discrete Systems Based on the Renormalization Group Method
The renormalization group (RG) method is extended for global asymptotic
analysis of discrete systems. We show that the RG equation in the discretized
form leads to difference equations corresponding to the Stuart-Landau or
Ginzburg-Landau equations. We propose a discretization scheme which leads to a
faithful discretization of the reduced dynamics of the original differential
equations.Comment: LaTEX. 12pages. 1 figure include
Quark condensates in the chiral bag with the NJL interaction
We discuss the quark condensate of the vacuum inside the baryon. We analyze
the 1+1 dimensional chiral bag in analogy with the realistic 3+1 dimensional
one. The Nambu--Jona-Lasinio (NJL) type interaction is used to investigate the
quark condensate in the chiral bag. Considering the strong meson-quark
coupling, we solve the mean field solution to the scalar and pseudoscalar
channels by including the chiral Casimir effects. The self-consistent equation
allows a finite value of the quark condensate and hence a finite dynamical
quark mass inside the bag. It is shown that an approximate Cheshire Cat picture
holds for massive quarks
Pseudogap of Color Superconductivity in Heated Quark Matter
We show that the pseudogap of the quark density of states is formed in hot
quark matter as a precursory phenomenon of the color superconductivity on the
basis of a low-energy effective theory. We clarify that the decaying process of
quarks near Fermi surface to a hole and the diquark soft mode (qq)_{soft} is
responsible for the formation of the pseudogap. Our result suggests that the
pseudogap is a universal phenomenon in strong coupling superconductors.Comment: Introduction is largely rewritten and minor changes are made in other
parts of the text. Some referenes with comments are added. Numerical errors
in the figures are corrected. To appear in Phys. Rev.
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