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.

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

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 $\beta$-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 $T$, although the phase diagrams with intermediate-$T$ 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 $T$, 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

Optimized Perturbation Theory for Wave Functions of Quantum Systems

The notion of the optimized perturbation, which has been successfully applied to energy eigenvalues, is generalized to treat wave functions of quantum systems. The key ingredient is to construct an envelope of a set of perturbative wave functions. This leads to a condition similar to that obtained from the principle of minimal sensitivity. Applications of the method to quantum anharmonic oscillator and the double well potential show that uniformly valid wave functions with correct asymptotic behavior are obtained in the first-order optimized perturbation even for strong couplings.Comment: 11 pages, RevTeX, three ps figure

Color neutrality effects in the phase diagram of the PNJL model

The phase diagram of a two-flavor Polyakov loop Nambu-Jona-Lasinio model is analyzed imposing the constraint of color charge neutrality. Main effects of this constraint are a shrinking of the chiral symmetry breaking (chiSB) domain in the T-mu plane, a shift of the critical point to lower temperatures and a coexistence of chiSB and two-flavor superconducting phases. The effects can be understood in view of the presence of a nonvanishing color chemical potential mu_8, which is necessary to compensate the color charge density rho_8 induced by the nonvanishing Polyakov-loop mean field phi_3.Comment: 8 pages, 4 figures, figures added, minor text modification

Reversible and Fast Association Equilibria of a Molecular Chaperone, gp57A, of Bacteriophage T4

The association of a molecular chaperone, gp57A, of bacteriophage T4, which facilitates formation of the long and short tail fibers, was investigated by analytical ultracentrifugation, differential scanning microcalorimetry, and stopped-flow circular dichroism (CD) to establish the association scheme of the protein. Gp57A is an oligomeric α-helix protein with 79 amino acids. Analysis of the sedimentation velocity data by direct boundary modeling with Lamm equation solutions together with a more detailed boundary analysis incorporating association schemes led us to conclude that at least three oligomeric species of gp57A are in reversible and fast association equilibria and that a 3mer-6mer-12mer model described the data best. On the other hand, differential scanning microcalorimetry revealed a highly reversible two-step transition of dissociation/denaturation, both of which accompanied decrease in CD at 222 nm. The melting curve analysis revealed that it is consistent with a 6mer-3mer-1mer model. The refolding/association kinetics of gp57A measured by stopped-flow CD was consistent with the interpretation that the bimolecular reaction from trimer to hexamer was preceded by a fast α-helix formation in the dead-time. Trimer or hexamer is likely the functional oligomeric state of gp57A

Phase diagram at finite temperature and quark density in the strong coupling limit of lattice QCD for color SU(3)

We study the phase diagram of quark matter at finite temperature (T) and finite chemical potential (mu) in the strong coupling limit of lattice QCD for color SU(3). We derive an analytical expression of the effective free energy as a function of T and mu, including baryon effects. The finite temperature effects are evaluated by integrating over the temporal link variable exactly in the Polyakov gauge with anti-periodic boundary condition for fermions. The obtained phase diagram shows the first order phase transition at low temperatures and the second order phase transition at high temperatures separated by the tri-critical point in the chiral limit. Baryon has effects to reduce the effective free energy and to extend the hadron phase to a larger mu direction at low temperatures.Comment: 18 pages, 10 figure