13 research outputs found
Vacuum replicas in two-dimensional QCD
Two-dimensional QCD is studied from the point of view of existence of
multiple chirally noninvariant solutions to the mass-gap equation. The
ground-state solution is reproduced and an infinite set of replica solutions is
discovered for this equation using the WKB quantisation procedure.Comment: LaTeX2e, 9 pages, 1 Postscript figure, uses epsfig.sty, to appear in
Phys.Lett.
Analytical approach to chiral symmetry breaking in Minkowsky space
The mass gap equation for spontaneous chiral symmetry breaking is studied
directly in Minkowsky space. In hadronic physics, spontaneous chiral symmetry
breaking is crucial to generate a constituent mass for the quarks, and to
produce the Partially Conserved Axial Current theorems, including a small mass
for the pion. Here a class of finite kernels is used, expanded in Yukawa
interactions. The Schwinger-Dyson equation is solved with an analytical
approach. This improves the state of the art of solving the mass gap equation,
which is usually solved with the equal-time approximation or with the Euclidean
approximation. The mapping from the Euclidean space to the Minkowsky space is
also illustrated.Comment: 7 pages, 3 figure
Field theory description of vacuum replicas
In this paper we develop a systematic quantum field theory based approach to
the vacuum replica recently found to exist in effective low energy models in
hadronic physics. A local operator creating the replica state is constructed
explicitly. We show that a new effective quark-quark force arises in result of
replica existence. Phenomenological implications of such a force are also
briefly discussed.Comment: RevTeX4, 23 pages, 4 Postscript figures, uses epsfig.sty, to appear
in Phys.Rev.
Fermion family recurrences in the Dyson-Schwinger formalism
We study the multiple solutions of the truncated propagator Dyson-Schwinger
equation for a simple fermion theory with Yukawa coupling to a scalar field.
Upon increasing the coupling constant , other parameters being fixed, more
than one non-perturbative solution breaking chiral symmetry becomes possible
and we find these numerically. These ``recurrences'' appear as a mechanism to
generate different fermion generations as quanta of the same fundamental field
in an interacting field theory, without assuming any composite structure. The
number of recurrences or flavors is reduced to a question about the value of
the Yukawa coupling, and has no special profound significance in the Standard
Model. The resulting mass function can have one or more nodes and the
measurement that potentially detects them can be thought of as a collider-based
test of the virtual dispersion relation for the charged
lepton member of each family. This requires three independent measurements of
the charged lepton's energy, three-momentum and off-shellness. We illustrate
how this can be achieved for the (more difficult) case of the tau lepton
Coulomb Gauge QCD, Confinement, and the Constituent Representation
Quark confinement and the genesis of the constituent quark model are examined
in nonperturbative QCD in Coulomb gauge. We employ a self-consistent method to
construct a quasiparticle basis and to determine the quasiparticle interaction.
The results agree remarkably well with lattice computations. They also
illustrate the mechanism by which confinement and constituent quarks emerge,
provide support for the Gribov-Zwanziger confinement scenario, clarify several
perplexing issues in the constituent quark model, and permit the construction
of an improved model of low energy QCD.Comment: 43 pages, 14 figures, revtex, uses psfig.st
Long distance regularization in chiral perturbation theory with decuplet
We investigate the use of long distance regularization in SU(3) baryon chiral
perturbation theory with decuplet fields. The one-loop decuplet contributions
to the octet baryon masses, axial couplings, S-wave nonleptonic hyperon decays
and magnetic moments are evaluated in a chirally consistent fashion by
employing a cutoff to implement long distance regularization. The convergence
of the chiral expansions of these quantities is improved compared to the
dimensionally regularized version which indicates that the propagation of
Goldstone bosons over distances smaller than a typical hadronic size, which is
beyond the regime of chiral perturbation theory but included by dimensional
regularization, is removed by use of a cutoff.Comment: 31 page
QCD Corrections to QED Vacuum Polarization
We compute QCD corrections to QED calculations for vacuum polarization in
background magnetic fields. Formally, the diagram for virtual loops
is identical to the one for virtual loops. However due to
confinement, or to the growth of as decreases, a direct
calculation of the diagram is not allowed. At large we consider the
virtual diagram, in the intermediate region we discuss the role of
the contribution of quark condensates \left and at the
low-energy limit we consider the , as well as charged pion
loops. Although these effects seem to be out of the measurement accuracy of
photon-photon laboratory experiments they may be relevant for -ray
burst propagation. In particular, for emissions from the center of the galaxy
(8.5 kpc), we show that the mixing between the neutral pseudo-scalar pion
and photons renders a deviation from the power-law spectrum in the
range. As for scalar quark condensates \left and
virtual loops are relevant only for very high radiation density
and very strong magnetic fields of order .Comment: 15 pages, 4 figures; Final versio