359 research outputs found
Infrared properties of propagators in Landau-gauge pure Yang-Mills theory at finite temperature
The finite-temperature behavior of gluon and of Faddeev-Popov-ghost
propagators is investigated for pure SU(2) Yang-Mills theory in Landau gauge.
We present nonperturbative results, obtained using lattice simulations and
Dyson-Schwinger equations. Possible limitations of these two approaches, such
as finite-volume effects and truncation artifacts, are extensively discussed.
Both methods suggest a very different temperature dependence for the magnetic
sector when compared to the electric one. In particular, a clear thermodynamic
transition seems to affect only the electric sector. These results imply in
particular the confinement of transverse gluons at all temperatures and they
can be understood inside the framework of the so-called Gribov-Zwanziger
scenario of confinement.Comment: 25 pages, 14 figures, 2 tables, minor changes of typographical and
design character, some minor errors corrected, version to appear in PR
Three dimensional fermionic determinants, Chern-Simons and nonlinear field redefinitions
The three dimensional abelian fermionic determinant of a two component
massive spinor in flat euclidean space-time is resetted to a pure Chern-Simons
action through a nonlinear redefinition of the gauge field.Comment: 18 pages, latex2
A-stable Runge-Kutta methods for semilinear evolution equations
We consider semilinear evolution equations for which the linear part
generates a strongly continuous semigroup and the nonlinear part is
sufficiently smooth on a scale of Hilbert spaces. In this setting, we prove the
existence of solutions which are temporally smooth in the norm of the lowest
rung of the scale for an open set of initial data on the highest rung of the
scale. Under the same assumptions, we prove that a class of implicit,
-stable Runge--Kutta semidiscretizations in time of such equations are
smooth as maps from open subsets of the highest rung into the lowest rung of
the scale. Under the additional assumption that the linear part of the
evolution equation is normal or sectorial, we prove full order convergence of
the semidiscretization in time for initial data on open sets. Our results
apply, in particular, to the semilinear wave equation and to the nonlinear
Schr\"odinger equation
Screening masses in quenched (2+1)d Yang-Mills theory: universality from dynamics?
We compute the spectrum of gluonic screening-masses in the channel
of quenched 3d Yang-Mills theory near the phase-transition. Our
finite-temperature lattice simulations are performed at scaling region, using
state-of-art techniques for thermalization and spectroscopy, which allows for
thorough data extrapolations to thermodynamic limit. Ratios among
mass-excitations with the same quantum numbers on the gauge theory, 2d Ising
and models are compared, resulting in a nice agreement with
predictions from universality. In addition, a gauge-to-scalar mapping,
previously employed to fit QCD Green's functions at deep IR, is verified to
dynamically describe these universal spectroscopic patternsComment: 15 pages, 4 eps figures. Revised version, to appear in Nucl. Phys.
Color Confinement, Quark Pair Creation and Dynamical Chiral-Symmetry Breaking in the Dual Ginzburg-Landau Theory
We study the color confinement, the - pair creation and the
dynamical chiral-symmetry breaking of nonperturbative QCD by using the dual
Ginzburg-Landau theory, where QCD-monopole condensation plays an essential role
on the nonperturbative dynamics in the infrared region. As a result of the dual
Meissner effect, the linear static quark potential, which characterizes the
quark confinement, is obtained in the long distance within the quenched
approximation. We obtain a simple expression for the string tension similar to
the energy per unit length of a vortex in the superconductivity physics. The
dynamical effect of light quarks on the quark confining potential is
investigated in terms of the infrared screening effect due to the -
pair creation or the cut of the hadronic string. The screening length of the
potential is estimated by using the Schwinger formula for the - pair
creation. We introduce the corresponding infrared cutoff to the strong
long-range correlation factor in the gluon propagator as a dynamical effect of
light quarks, and obtain a compact formula of the quark potential including the
screening effect in the infrared region. We investigate the dynamical
chiral-symmetry breaking by using the Schwinger-Dyson equation, where the gluon
propagator includes the nonperturbative effect related toComment: 37 pages, plain TeX (using `phyzzx' macro), (( 8 figures - available
on request from [email protected] )
Effective Action for QED with Fermion Self-Interaction in D=2 and D=3 Dimensions
In this work we discuss the effect of the quartic fermion self-interaction of
Thirring type in QED in D=2 and D=3 dimensions. This is done through the
computation of the effective action up to quadratic terms in the photon field.
We analyze the corresponding nonlocal photon propagators nonperturbatively in %
\frac{k}{m}, where k is the photon momentum and m the fermion mass. The poles
of the propagators were determined numerically by using the Mathematica
software. In D=2 there is always a massless pole whereas for strong enough
Thirring coupling a massive pole may appear . For D=3 there are three regions
in parameters space. We may have one or two massive poles or even no pole at
all. The inter-quark static potential is computed analytically in D=2. We
notice that the Thirring interaction contributes with a screening term to the
confining linear potential of massive QED_{2}. In D=3 the static potential must
be calculated numerically. The screening nature of the massive QED
prevails at any distance, indicating that this is a universal feature of % D=3
electromagnetic interaction. Our results become exact for an infinite number of
fermion flavors.Comment: Latex, 13 pages, 3 figure
Quadratic Effective Action for QED in D=2,3 Dimensions
We calculate the effective action for Quantum Electrodynamics (QED) in D=2,3
dimensions at the quadratic approximation in the gauge fields. We analyse the
analytic structure of the corresponding nonlocal boson propagators
nonperturbatively in k/m. In two dimensions for any nonzero fermion mass, we
end up with one massless pole for the gauge boson . We also calculate in D=2
the effective potential between two static charges separated by a distance L
and find it to be a linearly increasing function of L in agreement with the
bosonized theory (massive Sine-Gordon model). In three dimensions we find
nonperturbatively in k/m one massive pole in the effective bosonic action
leading to screening. Fitting the numerical results we derive a simple
expression for the functional dependence of the boson mass upon the
dimensionless parameter e^{2}/m .Comment: 10 pages, 2 figure
Temperature dependence of the anomalous effective action of fermions in two and four dimensions
The temperature dependence of the anomalous sector of the effective action of
fermions coupled to external gauge and pseudo-scalar fields is computed at
leading order in an expansion in the number of Lorentz indices in two and four
dimensions. The calculation preserves chiral symmetry and confirms that a
temperature dependence is compatible with axial anomaly saturation. The result
checks soft-pions theorems at zero temperature as well as recent results in the
literature for the pionic decay amplitude into static photons in the chirally
symmetric phase. The case of chiral fermions is also considered.Comment: RevTex, 19 pages, no figures. References adde
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