Heavy Quarkonia at High Temperature

We present a new method to study the properties of heavy quarks at finite temperature. It combines non-relativistic QCD with an improved gluonic action on anisotropic lattices. The efficiency of the approach is demonstrated by the first non-perturbative calculation of the temperature dependence of low-lying quarkonium "pole" masses. For ground state meson masses in the region between charmonium and bottomonium we find only very little variation up to our highest temperature which corresponds to T approximately 1.2 Tc while first excited states indicate a large mass shift.Comment: 17 pages of LaTeX with 26 PostScript figures, uses elsart style fil

Deconfinement from Action Restriction

The effect of restricting the plaquette to be greater than a certain cutoff value is studied. The action considered is the standard Wilson action with the addition of a plaquette restriction, which should not affect the continuum limit of the theory. In this investigation, the strong coupling limit is also taken. It is found that a deconfining phase transition occurs as the cutoff is increased, on all lattices studied (up to $20^4$). The critical cutoff on the infinite lattice appears to be around 0.55. For cutoffs above this, a fixed point behavior is observed in the normalized fourth cumulant of the Polyakov loop, suggesting the existence of a line of critical points corresponding to a massless gluon phase, not unlike the situation in compact U(1). The Polyakov loop susceptibility also appears to be diverging with lattice size at these cutoffs. A strong finite volume behavior is observed in the pseudo-specific heat. It is discussed whether these results could still be consistent with the standard crossover picture which precludes the existence of a deconfining phase transition on an infinite symmetric lattice.Comment: 4 pages latex, 6 ps figures, uses espcrc2.sty (included). Poster presented at LATTICE96(topology

Universality, Scaling and Topology with a Modified Lattice Action

We examined the effect of a complete suppression of a lattice artifact, the negative plaquettes, on physical quantities, such as the critical temperature, the string tension, the topological charge, glueball masses, and their ratios.Comment: 3 pages, self unpacking uuencoded PostScript file, contribution to conference LATTICE '9

Probing Confinement with Chromomagnetic Fields

Using the lattice Schr\"odinger functional we study vacuum dynamics of SU(3) gauge theory at finite temperature. The vacuum is probed by means of an external constant Abelian chromomagnetic field. We find that by increasing the strength of the applied external field the deconfinement temperature decreases towards zero. This implies that strong enough Abelian chromomagnetic fields destroy confinement of color.Comment: Lattice2002(topology). 3 pages, 3 figure

Confinement by Monopoles in the Positive Plaquette Model of SU(2) Lattice Gauge Theory

Confinement via 't Hooft-Mandelstam monopoles is studied for the positive plaquette model in SU(2) lattice gauge theory. Positive plaquette model configurations are projected into the maximum abelian gauge and the magnetic current extracted. The resulting magnetic current is used to compute monopole contributions to Wilson loops and extract a monopole contribution to the string tension. As was previously found for the Wilson action, the monopole contribution to the string tension agrees with the string tension calculated directly from the SU(2) links. The fact that the positive plaquette model suppresses Z2 monopoles and vortices is discussed.Comment: 8 pages, one Postscript figure, Latex, uses psfig files: posplaq.tex,posplaq.aux,pp_1_3.ps packaged with uufile

Spinodal Decomposition in High Temperature Gauge Theories

After a rapid increase in temperature across the deconfinement temperature $T_{d}$, pure gauge theories exhibit unstable long wavelength fluctuations in the approach to equilibrium. This phenomenon is analogous to spinodal decomposition observed in condensed matter physics, and also seen in models of disordered chiral condensate formation. At high temperature, the unstable modes occur only in the range $0\leq k$ $\leq k_{c}$, where $k_{c}$ is on the order of the Debye screening mass $m_D$. Equilibration always occurs via spinodal decomposition for $SU(2)$at temperatures $T>T_{d}$ and for SU(3) for $T\gg T_{d}$. For SU(3) at temperatures $T\gtrsim T_{d}$, nucleation may replace spinodal decomposition as the dominant equilibration mechanism. Monte Carlo simulations of SU(2) lattice gauge theory exhibit the predicted phenomena. The observed value of $k_c$ is in reasonable agreement with a value predicted from previous lattice measurements of $m_D$.Comment: minor revisions, 16 pages, 6 figures, RevTe

Numerical test of Polyakov loop models in high temperature SU(2)

We study the compatibility of effective mean-field models of the Polyakov loop for the deconfined phase of SU(N) pure gauge theories with lattice data obtained for the case of SU(2), in the temperature range T_c - 4.8 T_c.Comment: Poster presented at Lattice2004(non-zero), Fermilab, June 21-26, 2004; 3 pages, 4 figures, uses espcrc2.st

Effective actions for finite temperature Lattice Gauge Theories

We consider a lattice gauge theory at finite temperature in ($d$+1) dimensions with the Wilson action and different couplings $\beta_t$ and $\beta_s$ for timelike and spacelike plaquettes. By using the character expansion and Schwinger-Dyson type equations we construct, order by order in $\beta_s$, an effective action for the Polyakov loops which is exact to all orders in $\beta_t$. As an example we construct the first non-trivial order in $\beta_s$ for the (3+1) dimensional SU(2) model and use this effective action to extract the deconfinement temperature of the model.Comment: Talk presented at LATTICE96(finite temperature

Low-Energy Theorems for Gluodynamics at Finite Temperature

We generalize the low-energy theorems of gluodynamics to finite temperature. Examples of the theorems in the low and high temperature limits are given.Comment: 8 pages latex plus 1 postscript figur