Pion Superfluidity and Meson Properties at Finite Isospin Density

We investigate pion superfluidity and its effect on meson properties and equation of state at finite temperature and isospin and baryon densities in the frame of standard flavor SU(2) NJL model. In mean field approximation to quarks and random phase approximation to mesons, the critical isospin chemical potential for pion superfluidity is exactly the pion mass in the vacuum, and corresponding to the isospin symmetry spontaneous breaking, there is in the pion superfluidity phase a Goldstone mode which is the linear combination of the normal sigma and charged pion modes. We calculate numerically the gap equations for the chiral and pion condensates, the phase diagrams, the meson spectra, and the equation of state, and compare them with that obtained in other effective models. The competitions between pion superfluidity and color superconductivity at finite baryon density and between pion and kaon superfluidity at finite strangeness density in flavor SU(3) NJL model are briefly discussed.Comment: Updated version: (1)typos corrected; (2)an algebra error in Eq.(87) corrected; (3)Fig.(17) renewed according to Eq.(87). We thank Prof.Masayuki Matsuzaki for pointing out the error in Eq.(87

Production of the X(3872) at the Tevatron and the LHC

We predict the differential cross sections for production of the X(3872) at the Tevatron and the Large Hadron Collider from both prompt QCD mechanisms and from decays of b hadrons. The prompt cross section is calculated using the NRQCD factorization formula. Simplifying assumptions are used to reduce the nonperturbative parameters to a single NRQCD matrix element that is determined from an estimate of the prompt cross section at the Tevatron. For X(3872) with transverse momenta greater than about 4 GeV, the predicted cross section is insensitive to the simplifying assumptions. We also discuss critically a recent analysis that concluded that the prompt production rate at the Tevatron is too large by orders of magnitude for the X(3872) to be a weakly-bound charm-meson molecule. We point out that if charm-meson rescattering is properly taken into account, the upper bound is increased by orders of magnitude and is compatible with the observed production rate at the Tevatron.Comment: 29 pages, 5 figure

Response functions of cold neutron matter: density fluctuations

We compute the finite temperature density response function of nonrelativistic cold fermions with an isotropic condensate. The pair-breaking contribution to the response function is evaluated in the limit of small three-momentum transfers q within an effective theory which exploits series expansion in powers of small q/p_F, where p_F is the Fermi momentum. The leading order O(q^2) contribution is universal and depends only on two fundamental scales, the Fermi energy and the pairing gap. The particle-hole Landau Fermi-liquid interaction contributes first at the next-to-leading-order O(q^4). The scattering contribution to the polarization tensor is nonperturbative (in the above sense) and is evaluated numerically. The spectral functions of density fluctuations are constructed and the relevance of the q^2 scaling for the pair-breaking neutrino emission from neutron stars is discussed.Comment: v2: 11 pages, 4 figures, matches published version

Universality of the single-particle spectra of cuprate superconductors

All the available data for the dispersion and linewidth of the single-particle spectra above the superconducting gap and the pseudogap in metallic cuprates for any doping has universal features. The linewidth is linear in energy below a scale $\omega_c$ and constant above. The cusp in the linewidth at $\omega_c$ mandates, due to causality, a "waterfall", i.e., a vertical feature in the dispersion. These features are predicted by a recent microscopic theory. We find that all data can be quantitatively fitted by the theory with a coupling constant $\lambda_0$ and an upper cutoff at $\omega_c$ which vary by less than 50% among the different cuprates and for varying dopings. The microscopic theory also gives these values to within factors of O(2).Comment: 4 pages, 4 figures; accepted by Phys. Rev. Let

Pion condensation in the two--flavor chiral quark model at finite baryochemical potential

Pion condensation is studied at one--loop level and nonzero baryochemical potential in the framework of two flavor constituent quark model using the one--loop level optimized perturbation theory for the resummation of the perturbative series. A Landau type of analysis is presented for the investigation of the phase boundary between the pion condensed/non-condensed phases. The statement that the condensation starts at \muI = m_{\pi} is slightly modified by one--loop corrections. The second order critical surface is determined and analysed in the \muI-\muB-T space. The \muI dependence of the one--loop level charged pion pole masses is also studied.Comment: 12 pages, 5 figures, submitted to PR

Neutral weak currents in nucleon superfluid Fermi liquids: Larkin-Migdal and Leggett approaches

Neutrino emission in processes of breaking and formation of nucleon Cooper pairs is calculated in the framework of the Larkin-Migdal and the Leggett approaches to the description of superfluid Fermi liquids at finite temperatures. We explain peculiarities of both approaches and explicitly demonstrate that they lead to the same expression for the emissivity in pair breaking and formation processes.Comment: 24 pages, 3 figure

Quasiparticle-vibration coupling in relativistic framework: shell structure of Z=120 isotopes

For the first time, the shell structure of open-shell nuclei is described in a fully self-consistent extension of the covariant energy density functional theory. The approach implies quasiparticle-vibration coupling for superfluid systems. One-body Dyson equation formulated in the doubled quasiparticle space of Dirac spinors is solved for nucleonic propagators in tin isotopes which represent the reference case: the obtained energies of the single-quasiparticle levels and their spectroscopic amplitudes are in agreement with data. The model is applied to describe the shell evolution in a chain of superheavy isotopes $^{292,296,300,304}$120 and finds a rather stable proton spherical shell closure at Z = 120. An interplay of the pairing correlations and the quasiparticle-phonon coupling gives rise for a smooth evolution of the neutron shell gap between N = 172 and N = 184 neutron numbers. Vibrational corrections to the alpha decay energies reach several hundred keV and can be either positive and negative, thus also smearing the shell effects.Comment: 10 pages, 3 figure

Strong electron-lattice coupling as the mechanism behind charge density wave transformations in transition-metal dichalcogenides

We consider single band of conduction electrons interacting with displacements of the transitional ions. In the classical regime strong enough coupling transforms the harmonic elastic energy for an ion to the one of the well with two deep minima, so that the system is described in terms of Ising spins. Inter-site interactions order spins at lower tempratures. Extention to the quantum regime is discussed. Below the CDW-transition the energy spectrum of electrons remains metallic because the structural vector Q and the FS sizes are not related. Large values of the CDW gap seen in the tunneling experiments correspond to the energy of the minima in the electron-ion two-well complex. The gap is defined through the density of states (DOS) inside the electronic bands below the CDW transition. We focus mainly on electronic properties of transition-metal dichalcogenides.Comment: new references added; accepted for publication in Physical Review B. arXiv admin note: substantial text overlap with arXiv:1110.043

Diquark and Pion Condensation in Random Matrix Models for two-color QCD

We introduce a random matrix model with the symmetries of QCD with two colors at nonzero isospin and baryon chemical potentials and temperature. We analyze its phase diagram and find phases with condensation of pion and diquark states in addition to the phases with spontaneously broken chiral symmetries. In the limit of small chemical potentials and quark masses, we reproduce the mean field results obtained from chiral Lagrangians. As in the case of QCD with three colors, the presence of two chemical potentials breaks the flavor symmetry and leads to phases that are characterized by different behaviors of the chiral condensates for each flavor. In particular, the phase diagram we obtain is similar to QCD with three colors and three flavors of quarks of equal masses at zero baryon chemical potential and nonzero isospin and strange chemical potentials. A tricritical point of the superfluid transitions found in lattice calculations and from an analysis in terms of chiral Lagrangians does not appear in the random matrix model. Remarkably, at fixed isospin chemical potential, for the regions outside of the superfluid phases, the phase diagram in the temperature - baryon chemical potential plane for two colors and three colors are qualitatively the same.Comment: 19 pages, 7 figures, RevTeX

Critical densities for the Skyrme type effective interactions

We use the stability conditions of the Landau parameters for the symmetric nuclear matter and pure neutron matter to calculate the critical densities for the Skyrme type effective nucleon-nucleon interactions. We find that the critical density can be maximized by adjusting appropriately the values of the enhancement factor $\kappa$ associated with isovector giant dipole resonance, the quantity $L$ which is directly related to the slope of the symmetry energy and the Landau parameter $G_0^\prime$. However, restricting $\kappa$, $L$ and $G_0^\prime$ to vary within acceptable limits reduces the maximum value for the critical density $\tilde\rho_{cr}$ by $\sim 25$. We also show that among the various quantities characterizing the symmetric nuclear matter, $\tilde\rho_{cr}$ depends strongly on the isoscalar effective mass $m^*/m$ and surface energy coefficient $E_s$. For realistic values of $m^*/m$ and $E_s$ we get $\tilde\rho_{cr} = 2\rho_0$ to $3\rho_0$ ($\rho_0 = 0.16$fm$^{-3}$).Comment: 10 pages, 3 figures. Physicsl Review C (in press