Quantum decoupling transition in a one-dimensional Feshbach-resonant superfluid

We study a one-dimensional gas of fermionic atoms interacting via an s-wave molecular Feshbach resonance. At low energies the system is characterized by two Josephson-coupled Luttinger liquids, corresponding to paired atomic and molecular superfluids. We show that, in contrast to higher dimensions, the system exhibits a quantum phase transition from a phase in which the two superfluids are locked together to one in which, at low energies, quantum fluctuations suppress the Feshbach resonance (Josephson) coupling, effectively decoupling the molecular and atomic superfluids. Experimental signatures of this quantum transition include the appearance of an out-of-phase gapless mode (in addition to the standard gapless in-phase mode) in the spectrum of the decoupled superfluid phase and a discontinuous change in the molecular momentum distribution function.     

The gluon condensate and the deconfinement transition

The gluon condensate of dimension 4 is shown to stay unchanged through the deconfining phase transition.     

Correlations between dilepton yields and pion multiplicities as probe of the deconfinement transition

The correlation between dilepton yields and pion multiplicities from the thermalized baryon-poor central region matter produced in ultra-relativistic nucleus-nucleus collisions is analyzed within a hydrodynamical framework. A “cut-in” (or a concave section) in the correlation function is predicted as signal of the deconfinement transition. Transverse flow effects, finite hadronization times of the deconfined matter and realistic initial matter distribution tend to enhance this signal. The need of a refined background subtraction is pointed out to discriminate the dileptons stemming from hard initial interactions and pre-equilibrium processes.     

Migdal renormalization group approach to deconfinement phase transition

The Migdal renormalization group approach is applied to a finite temperature lattice gauge theory. Imposing the periodic boundary condition in the timelike orientation, the phase structure of the finite temperature lattice gauge system with a gauge groupG in (d+1)-dimensional space is determined by two kinds of recursion equations, describing spacelike and timelike correlations, respectively. One is the recursion equation for ad-dimensional gauge system with the gauge groupG, and the other corresponds to ad-dimensional spin system for which the effective theory is described by the nearest neighbor interaction of the Wilson lines. Detailed phase structure is investigated for theSU(2) gauge theory in (3+1)-dimensional space. Deconfinement phase transition is obtained. Using the recursion equation for the three dimensional spin system of the Wilson lines, it is shown that the flow of the renormalization group trajectories leads to a phase transition of the three dimensional Ising model.     

On the deconfinement phase transition in the resonance gas

We obtain the constraints on the governing parameters of the dense hadronic gas model at the critical temperature and propose quasiuniversal ratios of the thermodynamic quantities. The possible appearance of thermodynamic instability is discussed. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 487–491 (10 April 1996) Alexander von Humboldt Fellow. Published in English in the original Russian journal. Edited by Steve Torstveit.     

Hydrodynamic modeling of deconfinement phase transition in nuclear collision

The (3 + 1)-dimensional ideal hydrodynamics is used to simulate collisions of gold nuclei with bombarding energies from 1 to 160 GeV per nucleon. The initial state is represented by two cold Lorentzboosted nuclei. Two equations of state: with and without the deconfinement phase transition are used. We have investigated dynamical trajectories of compressed baryon-rich matter as functions of various thermodynamical variables. The parameters of collective flow and hadronic spectra are calculated. It is shown that presence of the deconfinement phase transition leads to increase of the elliptic flow and to flattening of proton rapidity distributions.     

Thermodynamics of a single bag and quark deconfinement phase transition

We present-in our opinion conclusive-evidence that the fermion number induced by the coupling to a chiral hedgehog in 3+1 dimensions is zero.     

Model of deconfinement phase transition in baryonic quark-gluon bag system

A model of phase transition between baryonic hadron and quark-gluon matter is elaborated. The spectrum of baryonic colourless bags is found. It is shown that the constraint of bag colourlessness is decisive for the phase transition to be realized.     

Phase transition for Ising frustration potentials

A frustration potential is a sum of interactions the terms of which are not simultaneously minimized even in the ground-state spin configurations. Ising models with such potentials can be discussed by the use of contours. The Peierls condition for the phase transition can be properly generalized, taking into account the presence of zero-energy contours. Frustration has some special features in two dimensions, which we study in detail. The connection with models of spin-glasses is discussed.     

The deconfinement transition in SU(2) lattice gauge theories

Using Monte Carlo techniques we study the SU(2) Yang-Mills system at finite temperatures for two different forms of lattice action, proposed by Villain and Monton respectively. In both cases the energy density ε exhibits a similar behaviour to the case of the Wilson action, being an order of magnitude smaller at lower temperatures and approaching the Stefan-Boltzmann limit for a free gluon gas at higher temperatures. The transition between these two temperature regimes appears rather abrupt and the specific heat of gluon matter exhibits a sharp peak at the transition point. The transition temperature, expressed in MeV, is found to be consistent in both the cases with that obtained by using the Wilson action, although in the natural units of the corresponding Λ-parameters it differs substantially, being 10.7, 27.3 and 42.8 for Manton, Villain and Wilson actions, respectively.     

Finite size effects on bag thermodynamics and quark-gluon deconfinement phase transition

We have investigated the effects of finite size corrections (surface and curvature) to the single particle density of states on various thermodynamic quantities of massless quarks and gluons confined in a spherical cavity. The chemical potential zero and non-zero both the cases are studied. Ignoring the surface term which seems much less important than the curvature term, the problem can be studied analytically in the case of zero chemical potential. We find a first order deconfinement phase transition contrary to the second order in absence of the curvature term. Furthermore, the values of the transition temperature,T _s in the infinite volume limit and the critical temperatureT _c >T _s , beyond which hadrons cease to exist, are in conformity with our earlier studies.     

Excitations in correlated superfluids near a continuous transition into a supersolid

We study a superfluid on a lattice close to a transition into a supersolid phase and show that a uniform superflow in the homogeneous superfluid can drive the roton gap to zero. This leads to supersolid order around the vortex core in the superfluid, with the size of the modulated pattern around the core being related to the bulk superfluid density and roton gap. We also study the electronic tunneling density of states for a uniform superconductor near a phase transition into a supersolid phase. Implications are considered for strongly correlated superconductors.