2,292 research outputs found
Correlation functions of the energy-momentum tensor in SU(2) gauge theory at finite temperature
We calculate correlation functions of the energy-momentum tensor in the
vicinity of the deconfinement phase transition of (3+1)-dimensional SU(2) gauge
theory and discuss their critical behavior in the vicinity of the second order
deconfinement transition. We show that correlation functions of the trace of
the energy momentum tensor diverge uniformly at the critical point in
proportion to the specific heat singularity. Correlation functions of the
pressure, on the other hand, stay finite at the critical point. We discuss the
consequences of these findings for the analysis of transport coefficients, in
particular the bulk viscosity, in the vicinity of a second order phase
transition point.Comment: 24 pages, 6 figure
Order, Disorder and Confinement
Studying the order of the chiral transition for is of fundamental
importance to understand the mechanism of color confinement. We present results
of a numerical investigation on the order of the transition by use of a novel
strategy in finite size scaling analysis. The specific heat and a number of
susceptibilities are compared with the possible critical behaviours. A second
order transition in the O(4) and O(2) universality classes are excluded.
Substantial evidence emerges for a first order transition. Results are in
agreement with those found by studying the scaling properties of a disorder
parameter related to the dual superconductivity mechanism of color confinement.Comment: 7 pages, 11 figures. Talk given at the International Workshop on
Quantum Chromodynamics: QCD@Work 2005, Conversano, Italy, 16-20 June 200
The chiral transition in two-flavor QCD
QCD with N_f=2 is a specially interesting system to investigate the chiral
transition. The order of the transition has still not been established. We
report the results of an in-depth numerical investigation performed with
staggered fermions on lattices with L_t=4 and L_s=12,16,20,24,32 and quark
masses am_q ranging from 0.01335 to 0.307036. Using finite-size techniques we
compare the scaling behavior of a number of thermodynamical susceptibilities
with the expectations of O(4) and O(2) universality classes. Clear disagreement
is observed. Indications of a first order transition are found.Comment: 6 pages, 4 figures, PoS style. Talk presented at Lattice 2005
(Nonzero temperature and density), Dublin, Ireland, July 25-3
A test of first order scaling in Nf =2 QCD: a progress report
We present the status of our analysis on the order of the finite temperature
transition in QCD with two flavors of degenerate fermions. Our new simulations
on large lattices support the hypothesis of the first order nature of the
transition, showing a preliminary two state signal. We will discuss the
implications and the next steps in our analysis.Comment: 6 pages, 4 figures. Talk presented at The XXVI International
Symposium on Lattice Field Theory, July 14 - 19, 2008 - Williamsburg,
Virginia, US
A test of first order scaling in Nf=2 QCD
We complete our analysis of Nf=2 QCD based on the lattice staggered fermion
formulation. Using a series of Monte Carlo simulations at fixed (amq*Ls^yh) one
is able to test the universality class with given critical exponent yh. This
strategy has been used to test the O(4) universality class and it has been
presented at the previous Lattice conferences. No agreement was found with
simulations in the mass range amq=[0.01335,0.15] using lattices with Ls=16 up
to 32 and Lt=4. With the same strategy, we now investigate the possibility of a
first order transition using a new set of Monte Carlo data corresponding to
yh=3 in the same mass and volume range as the one used for O(4). A substantial
agreement is observed both in the specific heat scaling and in the scaling of
the chiral condensate, while the chiral susceptibilities still presents visible
deviation from scaling in the mass range explored.Comment: 5 pages, 6 figures, Presented at the XXV International Symposium on
Lattice Field Theory, July 30 - August 4 2007, Regensburg, German
Two flavor QCD and confinement - II
This paper is part of a program of investigation of the chiral transition in
Nf=2 QCD, started in Phys.Rev.D72:114510,2005. Progress is reported on the
understanding of some possible systematic errors. A direct test of first order
scaling is presented.Comment: 7 pages, 6 figure
Conformal vs confining scenario in SU(2) with adjoint fermions
The masses of the lowest-lying states in the meson and in the gluonic sector
of an SU(2) gauge theory with two Dirac flavors in the adjoint representation
are measured on the lattice at a fixed value of the lattice coupling for values of the bare fermion mass that span a range
between the quenched regime and the massless limit, and for various lattice
volumes. Even for light constituent fermions the lightest glueballs are found
to be lighter than the lightest mesons. Moreover, the string tension between
two static fundamental sources strongly depends on the mass of the dynamical
fermions and becomes of the order of the inverse squared lattice linear size
before the chiral limit is reached. The implications of these findings for the
phase of the theory in the massless limit are discussed and a strategy for
discriminating between the (near--)conformal and the confining scenario is
outlined.Comment: 5 pages, 4 figures using RevTeX4, Typos corrected, references added.
Versions to appear on PR
Spontaneous breaking of discrete symmetries in QCD on a small volume
In a compact space with non-trivial cycles, for sufficiently small values of
the compact dimensions, charge conjugation (C), spatial reflection (P) and time
reversal (T) are spontaneously broken in QCD. The order parameter for the
symmetry breaking is the trace of the Wilson line wrapping around the compact
dimension, which acquires an imaginary part in the broken phase. We show that a
physical signature for the symmetry breaking is a persistent baryonic current
wrapping in the compact directions. The existence of such a current is derived
analytically at first order in perturbation theory and confirmed in the
non-perturbative regime by lattice simulations.Comment: 4 pages, 2 figures, based on the poster presented by B. Lucini at
Pascos 0
Rho meson decay width in SU(2) gauge theories with 2 fundamental flavours
7 pages, Proceedings of the 34th International Symposium on Lattice Field Theory (Lattice 2016)SU(2) gauge theories with two quark flavours in the fundamental representation are among the most promising theories of composite dynamics describing the electroweak sector. Three out of five Goldstone bosons in these models become the longitudinal components of the W and Z bosons giving them mass. Like in QCD, we expect a spectrum of excitations which appear as resonances in vector boson scattering, in particular the vector resonance corresponding to the rho-meson in QCD. In this talk I will present the preliminary results of the first calculation of the rho-meson decay width in this theory, which is analogous to rho to two pions decay calculation in QCD. The results presented were calculated in a moving frame with total momentum (0,0,1) on two ensembles. Future plans include using 3 moving frames on a larger set of ensembles to extract the resonance parameters more reliably and also take the chiral and continuum limits
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