16 research outputs found
Formation of light antinuclei and "dense gas" stage in heavy ion collisions
The antideuteron and antihelium-3 production rates at high-energy heavy ion
collisions are calculated in the framework of fusion mechanism when
participating particles are moving in the mean field of other fireball
constituents. It is shown that coalescence parameters can be found from the
requirement of balance between created and disintegrated antinuclei. The
explicit formulae for coalescence parameters are presented and compared with
experimental data.Comment: To be published in "Proceedings of the 18th International Nuclear
Physics Divisional Conference of the EPS (NPDC18), 2004.
Theory of the Magnetic Catalysis of Chiral Symmetry Breaking in QED
The theory of the magnetic catalysis of chiral symmetry breaking in QED is
developed. An approximation for the Schwinger-Dyson equations describing
reliably this phenomenon is established, i.e., it is shown that there exists a
consistent truncation of those equations in this problem. The equations are
solved both analytically and numerically, and the dynamical mass of fermions is
determined.Comment: 22 pages, 5 figures, REVTe
QCD vacuum structure in strong magnetic fields
We study the response of the QCD vacuum to strong magnetic fields, using a
potential model for the quark-antiquark interaction. We find that production of
spin-polarized u-ubar pairs is energetically favorable for fields B > B_crit
\sim 10 GeV^2. We contrast the resulting u-ubar condensate with the quark
condensate which is present at zero magnetic field, and we estimate the
corresponding magnetization as a function of B.Comment: 16 pages, LaTeX, 3 eps figures. v2: references added. v3: fixed typ
Quark condensate in a magnetic field
We study the dependence of quark condensate on an external magnetic
field. For weak fields, it rises linearly with the field. Pion mass and residue
are also shifted so that the Gell-Mann - Oakes - Renner relation is satisfied.
In the strong field region, .Comment: 13 pages LaTeX, 5 postscript files for figure
Nonlinear Realization of Chiral Symmetry on the Lattice
We formulate lattice theories in which chiral symmetry is realized
nonlinearly on the fermion fields. In this framework the fermion mass term does
not break chiral symmetry. This property allows us to use the Wilson term to
remove the doubler fermions while maintaining exact chiral symmetry on the
lattice. Our lattice formulation enables us to address non-perturbative
questions in effective field theories of baryons interacting with pions and in
models involving constituent quarks interacting with pions and gluons. We show
that a system containing a non-zero density of static baryons interacting with
pions can be studied on the lattice without encountering complex action
problems. In our formulation one can also decide non-perturbatively if the
chiral quark model of Georgi and Manohar provides an appropriate low-energy
description of QCD. If so, one could understand why the non-relativistic quark
model works.Comment: 34 pages, 2 figures, revised version to be published in J. High
Energy Phys. (changes in the 1st paragraph, additional descriptions on the
nature of the coordinate singularities in Sec.2, references added
Monopoles, confinement and deconfinement of (2+1)D compact lattice QED in external fields
The compact Abelian model in three space--time dimensions is studied in the
presence of external electromagnetic fields at finite temperatures. We show
that the deconfinement phase transition is independent on the strength of the
external fields. This result is in agreement with our observation that the
external fields create small--size magnetic dipoles from the vacuum which do
not influence the confining properties of the model. Contrary to the
deconfinement phase, the internal field in the direction of the applied
external field is attenuated in the confinement phase, this screening becomes
stronger with decreasing temperature.Comment: 22 pages, 24 EPS figures, LaTeX uses epsfig.st
Magnetic catalysis and anisotropic confinement in QCD
The expressions for dynamical masses of quarks in the chiral limit in QCD in
a strong magnetic field are obtained. A low energy effective action for the
corresponding Nambu-Goldstone bosons is derived and the values of their decay
constants as well as the velocities are calculated. The existence of a
threshold value of the number of colors , dividing the theories with
essentially different dynamics, is established. For the number of colors , an anisotropic dynamics of confinement with the confinement
scale much less than and a rich spectrum of light glueballs is
realized. For of order or larger, a conventional confinement
dynamics takes place. It is found that the threshold value grows
rapidly with the magnetic field [ for ]. In contrast to QCD with a nonzero baryon density, there are no
principal obstacles for checking these results and predictions in lattice
computer simulations.Comment: 10 pages, 1 figure. REVTeX. Minor correction. To appear in Phys. Rev.
Lectures on Chiral Disorder in QCD
I explain the concept that light quarks diffuse in the QCD vacuum following
the spontaneous breakdown of chiral symmetry. I exploit the striking analogy to
disordered electrons in metals, identifying, among others, the universal regime
described by random matrix theory, diffusive regime described by chiral
perturbation theory and the crossover between these two domains.Comment: Lectures given at the Cargese Summer School, August 6-18, 200
Beyond-Constant-Mass-Approximation Magnetic Catalysis in the Gauge Higgs-Yukawa Model
Beyond-constant-mass approximation solutions for magnetically catalyzed
fermion and scalar masses are found in a gauge Higgs-Yukawa theory in the
presence of a constant magnetic field. The obtained fermion masses are several
orders of magnitude larger than those found in the absence of Yukawa
interactions. The masses obtained within the beyond-constant-mass approximation
exactly reduce to the results within the constant-mass approach when the
condition is satisfied. Possible
applications to early universe physics and condensed matter are discussed.Comment: Revised numerical results. New figures. Several sections rewritte
Universality and the magnetic catalysis of chiral symmetry breaking
The hypothesis that the magnetic catalysis of chiral symmetry breaking is due
to interactions of massless fermions in their lowest Landau level is examined
in the context of chirally symmetric models with short ranged interactions. It
is argued that, when the magnetic field is sufficiently large, even an
infinitesimal attractive interaction in the appropriate channel will break
chiral symmetry.Comment: 24 pages, 6 figures, REVTeX. The final version with minor
corrections. To appear in Phys Rev D60 (1999