11 research outputs found
Magnetic Oscillations in Dense Cold Quark Matter with Four-Fermion Interactions
The phase structures of Nambu-Jona-Lasinio models with one or two flavours
have been investigated at non-zero values of and , where is an
external magnetic field and is the chemical potential. In the phase
portraits of both models there arise infinitely many massless chirally
symmetric phases, as well as massive ones with spontaneously broken chiral
invariance, reflecting the existence of infinitely many Landau levels. Phase
transitions of first and second orders and a lot of tricritical points have
been shown to exist in phase diagrams. In the massless case, such a phase
structure leads unavoidably to the standard van Alphen-de Haas magnetic
oscillations of some thermodynamical quantities, including magnetization,
pressure and particle density. In the massive case we have found an oscillating
behaviour not only for thermodynamical quantities, but also for a dynamical
quantity as the quark mass. Besides, in this case we have non-standard, i.e.
non-periodic, magnetic oscillations, since the frequency of oscillations is an
-dependent quantity.Comment: latex, 29 pages, 8 figure
Quark and pion condensation in a chromomagnetic background field
The general features of quark and pion condensation in dense quark matter
with flavor asymmetry have been considered at finite temperature in the
presence of a chromomagnetic background field modelling the gluon condensate.
In particular, pion condensation in the case of a constant abelian
chromomagnetic field and zero temperature has been studied both analytically
and numerically. Under the influence of the chromomagnetic background field the
effective potential of the system is found to have a global minimum for a
finite pion condensate even for small values of the effective quark coupling
constant. In the strong field limit, an effective dimensional reduction has
been found to take place.Comment: 17 pages, 6 figure
Chiral symmetry breaking in d=3 NJL model in external gravitational and magnetic fields
The phase structure of Nambu-Jona-Lasinio model in curved spacetime
with magnetic field is investigated in the leading order of the -expansion
and in linear curvature approximation (an external magnetic field is treated
exactly). The possibility of the chiral symmetry breaking under the combined
action of the external gravitational and magnetic fields is shown explicitly.
At some circumstances the chiral symmetry may be restored due to the
compensation of the magnetic field by the gravitational field.Comment: 7 pages, LaTe
The Influence of an External Chromomagnetic Field on Color Superconductivity
We study the competition of quark-antiquark and diquark condensates under the
influence of an external chromomagnetic field modelling the gluon condensate
and in dependence on the chemical potential and temperature. As our results
indicate, an external chromomagnetic field might produce remarkable qualitative
changes in the picture of the color superconducting (CSC) phase formation. This
concerns, in particular, the possibility of a transition to the CSC phase and
diquark condensation at finite temperature.Comment: 27 pages, RevTex, 8 figures; the version accepted for the publication
in PRD (few references added; new numerical results added; main conclusions
are not changed
Non-abelian plane waves and stochastic regimes for (2+1)-dimensional gauge field models with Chern-Simons term
An exact time-dependent solution of field equations for the 3-d gauge field
model with a Chern-Simons (CS) topological mass is found. Limiting cases of
constant solution and solution with vanishing topological mass are considered.
After Lorentz boost, the found solution describes a massive nonlinear
non-abelian plane wave. For the more complicate case of gauge fields with CS
mass interacting with a Higgs field, the stochastic character of motion is
demonstrated.Comment: LaTeX 2.09, 13 pages, 11 eps figure
Energy States of Colored Particle in a Chromomagnetic Field
The unitary transformation, which diagonalizes squared Dirac equation in a
constant chromomagnetic field is found. Applying this transformation, we find
the eigenfunctions of diagonalized Hamiltonian, that describe the states with
definite value of energy and call them energy states. It is pointed out that,
the energy states are determined by the color interaction term of the particle
with the background chromofield and this term is responsible for the splitting
of the energy spectrum.
We construct supercharge operators for the diagonal Hamiltonian, that ensure
the superpartner property of the energy states.Comment: 25 pages, some calculation details have been removed, typos correcte
Pion condensation of quark matter in the static Einstein universe
In the framework of an extended Nambu--Jona-Lasinio model we are studying
pion condensation in quark matter with an asymmetric isospin composition in a
gravitational field of the static Einstein universe at finite temperature and
chemical potential. This particular choice of the gravitational field
configuration enables us to investigate phase transitions of the system with
exact consideration of the role of this field in the formation of quark and
pion condensates and to point out its influence on the phase portraits. We
demonstrate the effect of oscillations of the thermodynamic quantities as
functions of the curvature and also refer to a certain similarity between the
behavior of these quantities as functions of curvature and finite temperature.
Finally, the role of quantum fluctuations for spontaneous symmetry breaking in
the case of a finite volume of the universe is shortly discussed.Comment: RevTex4; 15 pages, 10 figure
Symmetry Nonrestoration in a Gross-Neveu Model with Random Chemical Potential
We study the symmetry behavior of the Gross-Neveu model in three and two
dimensions with random chemical potential. This is equivalent to a four-fermion
model with charge conjugation symmetry as well as Z_2 chiral symmetry. At high
temperature the Z_2 chiral symmetry is always restored. In three dimensions the
initially broken charge conjugation symmetry is not restored at high
temperature, irrespective of the value of the disorder strength. In two
dimensions and at zero temperature the charge conjugation symmetry undergoes a
quantum phase transition from a symmetric state (for weak disorder) to a broken
state (for strong disorder) as the disorder strength is varied. For any given
value of disorder strength, the high-temperature behavior of the charge
conjugation symmetry is the same as its zero-temperature behavior. Therefore,
in two dimensions and for strong disorder strength the charge conjugation
symmetry is not restored at high temperature.Comment: 16 pages, 3 figure
Numerical Portrait of a Relativistic Thin Film BCS Superfluid
We present results of numerical simulations of the 2+1d Nambu - Jona-Lasinio
model with a non-zero baryon chemical potential mu including the effects of a
diquark source term. Diquark condensates, susceptibilities and masses are
measured as functions of source strength j. The results suggest that diquark
condensation does not take place in the high density phase mu>mu_c, but rather
that the condensate scales non-analytically with j implying a line of critical
points and long range phase coherence. Analogies are drawn with the low
temperature phase of the 2d XY model. The spectrum of the spin-1/2 sector is
also studied yielding the quasiparticle dispersion relation. There is no
evidence for a non-zero gap; rather the results are characteristic of a normal
Fermi liquid with Fermi velocity less than that of light. We conclude that the
high density phase of the model describes a relativistic gapless thin film BCS
superfluid.Comment: 37 pages, 16 figure
Abnormal number of Nambu-Goldstone bosons in the color-asymmetric 2SC phase of an NJL-type model
We consider an extended Nambu--Jona-Lasinio model including both (q \bar q)-
and (qq)-interactions with two light-quark flavors in the presence of a single
(quark density) chemical potential. In the color superconducting phase of the
quark matter the color SU(3) symmetry is spontaneously broken down to SU(2). If
the usual counting of Goldstone bosons would apply, five Nambu-Goldstone (NG)
bosons corresponding to the five broken color generators should appear in the
mass spectrum. Unlike that expectation, we find only three gapless diquark
excitations of quark matter. One of them is an SU(2)-singlet, the remaining two
form an SU(2)-(anti)doublet and have a quadratic dispersion law in the small
momentum limit. These results are in agreement with the Nielsen-Chadha theorem,
according to which NG-bosons in Lorentz-noninvariant systems, having a
quadratic dispersion law, must be counted differently. The origin of the
abnormal number of NG-bosons is shown to be related to a nonvanishing
expectation value of the color charge operator Q_8 reflecting the lack of color
neutrality of the ground state. Finally, by requiring color neutrality, two
massive diquarks are argued to become massless, resulting in a normal number of
five NG-bosons with usual linear dispersion laws.Comment: 13 pages, 4 figures, revtex