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Pengfei Zhuang

Publications and source records attributed to Pengfei Zhuang.

At least 109 records · Page 6Linked to original sources
arXiv2009

BCS-BEC Crossover and Thermodynamics in Asymmetric Nuclear Matter with Pairings in Isospin I=0 and I=1 Channels

The BCS-BEC crossover and phase diagram for asymmetric nuclear superfluid with pairings in isospin I = 0 and I = 1 channels are investigated at mean field level, by using a density dependent nucleon-nucleon potential. Induced by the in-medium nucleon mass and density dependent coupling constants, neutron-proton Cooper pairs could be in BEC state at sufficiently low density, but there is no chance for the BEC formation of neutron-neutron and proton-proton pairs at any density and asymmetry. We calculate the phase diagram in asymmetry-temperature plane for weakly interacting nuclear superfluid, and find that including the I = 1 channel changes significantly the phase structure at low temperature. There appears a new phase with both I = 0 and I = 1 pairings at low temperature and low asymmetry, and the gapless state in any phase with I = 1 pairing is washed out and all excited nucleons are fully gapped.

nucl-th↗
arXiv2009

Neutrino Emission From Inhomogeneous Pion Condensed Quark Matter

It is believed that quark matter can exist in neutron star interior if the baryon density is high enough. When there is a large isospin density, quark matter could be in a pion condensed phase. We compute neutrino emission from direct Urca processes in such a phase, particularly in the inhomogeneous Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) states. The neutrino emissivity and specific heat are obtained, from which the cooling rate is estimated.

hep-ph↗
arXiv2009

J/psi elliptic flow in relativistic heavy ion collisions

The J/psi elliptic flow in high energy nuclear collisions is calculated in a transport model. While the flow is very small at SPS and RHIC energies, it is strongly enhanced at LHC energy due to the dominance of the regeneration mechanism.

nucl-th↗
arXiv2009

J/psi production at mid and forward rapidity at RHIC

We calculate the rapidity dependence of $J/ψ$ nuclear modification factor and averaged transverse momentum square in heavy ion collisions at RHIC in a 3-dimensional transport approach with regeneration mechanism.

nucl-th↗
arXiv2009

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.

hep-ph↗
arXiv2009

Critical Zeeman Splitting of Fermi Superfluidity at Infinite Scattering Length

We determine the critical Zeeman energy splitting for Fermi superfluidity at infinite s-wave scattering length according to the Monte Carlo and experimental results of the equations of state. Based on the universality hypothesis, we show that there exist two critical fields $H_{c1}$ and $H_{c2}$, between which a superfluid-normal mixed phase is energetically favored, and model-independent formulae for $H_{c1}$, $H_{c2}$ and the critical population imbalance $P_c$ are derived. Using recent Monte Carlo and experimental results of $P_c$, $H_{c1}$ and $H_{c2}$ are determined. It is found $H_{c1}=0.41ε_{\text F}$ and $H_{c2}=0.50ε_{\text F}$, with $ε_{\text F}$ being the Fermi energy of non-interacting gas.

cond-mat.supr-con↗
arXiv2009

Rapidity Dependence of $J/ψ$ Production at RHIC and LHC

The motion of charmonium in heavy ion collisions is described by a three dimensional transport equation with initial production and continuous regeneration in hot medium. The observation of apparently stronger $J/ψ$ suppression at forward rapidity compared to that at midrapidity, so called $J/ψ$ puzzle at RHIC, can well be explained by the competition between the two production mechanisms. At LHC, however, the rapidity dependence of the $J/ψ$ production is dominated by the regeneration process.

nucl-th↗
arXiv2009

J/psi Transverse Momentum Distribution in High Energy Nuclear Collisions

The transverse momentum (pt) dependence of J/psi production in heavy ion collisions is investigated in a transport model with both initial production and continuous regeneration of charmonia. The competition between the two production mechanisms results in a pt suppression in central collisions, the gluon multi-scattering in the initial stage leads to a high pt enhancement, and the regeneration populates J/psis at low pt region and induces a minimum in R_AA(pt). These three phenomena are indeed observed in both 200 GeV Cu+Cu and Au+Au collisions at RHIC energy.

nucl-th↗
arXiv2009

Pion Superfluidity beyond Mean Field Approximation In Nambu--Jona-Lasinio Model

We investigate pion superfluidity in the frame of two flavor Nambu--Jona-Lasinio model beyond mean field approximation. We calculate the thermodynamics to the next to leading order in an expansion in the inverse number of colors, including both quark and meson contributions at finite temperature and baryon and isospin density. Due to the meson fluctuations, the Sarma phase which exists at mean field level is washed away, and the Bose-Einstein condensation region at low isospin density is highly suppressed.

hep-ph↗
arXiv2009

Quark and Gluon Condensates in Isospin Matter

Applying the Hellmann-Feynman theorem to a charged pion gas, the quark and gluon condensates at low isospin density are determined by precise pion properties. At intermediate density around $ f_π^2m_π$, from both the estimation for the dilute pion gas and the calculation with Nambu--Jona-Lasinio model, the quark condensate is strongly and monotonously suppressed, while the gluon condensate is enhanced and can be larger than its vacuum value. This unusual behavior of the gluon condensate is universal for Bose condensed matter of mesons. Our results can be tested by lattice calculations at finite isospin density.

nucl-th↗
arXiv2009

Stable Sarma State in Two-band Fermi Systems

We investigate fermionic superconductivity with mismatched Fermi surfaces in a general two-band system. The exchange interaction between the two bands changes significantly the stability structure of the pairing states. The Sarma state with two gapless Fermi surfaces which is always unstable in single-band systems, can be the stable ground state in two-band systems. To realize a visible mismatch window for the stable Sarma state, two conditions should be satisfied: a nonzero inter-band exchange interaction and a large asymmetry between the two bands.

cond-mat.supr-con↗
arXiv2008

BEC-BCS Crossover in the Nambu--Jona-Lasinio Model of QCD

The BEC-BCS crossover in QCD at finite baryon and isospin chemical potentials is investigated in the Nambu--Jona-Lasinio model. The diquark condensation in two color QCD and the pion condensation in real QCD would undergo a BEC-BCS crossover when the corresponding chemical potential increases. We determined the crossover chemical potential as well as the BEC and BCS regions. The crossover is not triggered by increasing the strength of attractive interaction among quarks but driven by changing the charge density. The chiral symmetry restoration at finite temperature and density plays an important role in the BEC-BCS crossover. For real QCD, strong couplings in diquark and vector meson channels can induce a diquark BEC-BCS crossover in color superconductor, and in the BEC region the chromomagnetic instability is fully cured and the ground state is a uniform phase.

hep-ph↗
arXiv2008

Phase Diagram of Cold Polarized Fermi Gas in Two Dimensions

The superfluid phase diagrams of a two-dimensional cold polarized Fermi gas in the BCS-BEC crossover are systematically and analytically investigated. In the BCS-Leggett mean field theory, the transition from unpolarized superfluid phase to normal phase is always of first order. For a homogeneous system, the two critical Zeeman fields and the critical population imbalance are analytically determined in the whole coupling parameter region, and the superfluid-normal mixed phase is shown to be the ground state between the two critical fields. The density profile in the presence of a harmonic trap calculated in the local density approximation exhibits a shell structure, a superfluid core at the center and a normal shell outside. For weak interaction, the normal shell contains a partially polarized cloud with constant density difference surrounded by a fully polarized state. For strong interaction, the normal shell is totally in fully polarized state with a density profile depending only on the global population imbalance. The di-fermion bound states can survive in the whole highly imbalanced normal phase.

cond-mat.supr-con↗
arXiv2008

Quark Potential in a Quark-Meson Plasma

We investigate quark potential by considering meson exchanges in the two flavor Nambu--Jona-Lasinio model at finite temperature and density. There are two kinds of oscillations in the chiral restoration phase, one is the Friedel oscillation due to the sharp quark Fermi surface at high density, and the other is the Yukawa oscillation driven by the complex meson poles at high temperature. The quark-meson plasma is strongly coupled in the temperature region $1\le T/T_c \lesssim 3$ with $T_c$ being the critical temperature of chiral phase transition. The maximum coupling in this region is located at the critical point.

nucl-th↗
arXiv2007

Chiral Phase Structure at Finite Temperature and Density in Einstein Universe

The gravitational effect on the chiral phase structure at finite temperature and density is investigated in the framework of Nambu--Jona-Lasinio model in $D$-dimensional ultrastatic Einstein universe. In mean field approximation, the thermodynamic potential and the gap equation determining the curvature, temperature and density dependence of the chiral condensate are analytically derived. In the sense of chiral symmetry restoration and the order of the phase transition, the scalar curvature of the space-time plays similar role as the temperature.

hep-ph↗
arXiv2007

Neutrino Emission From Direct Urca Processes in Pion Condensed Quark Matter

We study neutrino emission from direct Urca processes in pion condensed quark matter. In compact stars with high baryon density, the emission is dominated by the gapless modes of the pion condensation which leads to an enhanced emissivity. While for massless quarks the enhancement is not remarkable, the emissivity is significantly larger and the cooling of the condensed matter is considerably faster than that in normal quark matter when the mass difference between $u$- and $d$-quarks is sizable.

hep-ph↗
arXiv2007

Asymmetric Fermi Superfluid With Two Types Of Pairings

We investigate the phase diagram in the plane of temperature and chemical potential mismatch for an asymmetric fermion superfluid with double- and single-species pairings. There is no mixing of these two types of pairings at fixed chemical potential, but the introduction of the single species pairing cures the magnetic instability at low temperature.

cond-mat.supr-con↗