Improving the Quark Number Susceptibilities for Staggered Fermions

Quark number susceptibilities approach their ideal gas limit at sufficiently high temperatures. As in the case of other thermodynamic quantities, this limit itself is altered substantially on lattices with small temporal extent, N_t = 4-8, making it thus difficult to check the validity of perturbation theory. Unlike other observables, improving susceptibilities or number densities is subject to constraints of current conservation and absence of chemical potential dependent divergences. We construct such an improved number density and susceptibility for staggered fermions and show that they approximate the continuum ideal gas limit better on small temporal lattices.Comment: Lattice2002(nonzerot), 3 pages, 3 figure

A smoother approach to scaling by suppressing monopoles and vortices

Suppressing monopoles and vortices by introducing large chemical potentials for them in the Wilson action for the SU(2) lattice gauge theory, we study the nature of the deconfinement phase transition on N_sigma^3 X N_tau lattices for N_tau =4, 5, 6 and 8 and N_sigma = 8-16. Using finite size scaling theory, we obtain \omega = 1.93 +/- 0.03 for N_tau = 4, in excellent agreement with universality. The critical couplings for N_tau= 4, 5, 6 and 8 lattices exhibit large shifts towards the strong coupling region when compared with the usual Wilson action, and suggest a lot smoother approach to scaling.Comment: Lattice 2000 (Topology and Vaccum II); LaTeX 4 pages, 2 figure

Results from Lattice QCD

I present our recent results on the critical end point in the \mu_B-T phase diagram of QCD with two flavours of light dynamical quarks and compare them with similar results from other groups. Implications for a possible energy scan at the RHIC are discussed. I also comment briefly on the new results of great relevance to heavy ion collisions from finite temperature lattice QCD simulations on speed of sound, specific heat and on the fate of J/\psi.Comment: Invited Plenary Talk given at 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma, Kolkata, India, February 8-12, 2005; LaTeX in Journal of Physics G style; 9 pages including figure

Phase Diagram of SO(3) Lattice Gauge Theory at Finite Temperature

The phase diagram of SO(3) lattice gauge theory at finite temperature is investigated by Monte Carlo techniques with a view i) to understand the relationship between the deconfinement phase transitions in the SU(2) and SO(3) lattice gauge theories and ii) to resolve the current ambiguity of the nature of the high temperature phases of the latter. Phases with positive and negative adjoint Polyakov loop are shown to have the same physics. A first order deconfining phase transition is found for N_t=4.Comment: 3 pages, 2 figures, latex2e, uses espcrc2.sty. Contribution to Lattice '97, Edinburgh, July 1997, to appear in Nucl. Phys. B (Proc. Suppl.) Latex command for figures correcte

Suppressing monopoles and vortices : A possibly smoother approach to scaling ?

Suppressing monopoles and vortices by introducing large chemical potentials for them in the Wilson action for the SU(2) lattice gauge theory, we study the nature of the deconfinement phase transition on N_\sigma^3 \times N_\tau lattices for N_\tau = 4, 5, 6 and 8 and N_\sigma = 8--16. Using finite size scaling theory, we obtain \omega = 1.93 \pm 0.03 for N_\tau = 4, in excellent agreement with universality. Corresponding determinations for the N_\tau = 5 and 6 lattices are also found to be in very good agreement with this estimate. The critical couplings for N_\tau= 4, 5, 6 and 8 lattices exhibit large shifts towards the strong coupling region when compared with the usual Wilson action, and suggest a lot smoother approach to scaling.Comment: 22 pages, LaTeX, 6 figures included, Very minor correction

C-Periodicity and the Physical Mass in the 3-State Potts Model

The standard infinite-volume definition of connected correlation function and particle mass in the 3-state Potts model can be implemented in Monte Carlo simulations by using C-periodic spatial boundary conditions. This avoids both the breaking of translation invariance (cold wall b.c.) and the phase-dependent and thus possibly biased evaluation of data (periodic boundary cconditions). The numerical feasibility of the standard definitions is demonstrated by sample computations on a 24*24*48 lattice.Comment: 13 pages + 5 figures Preprint Nos. IC/93/131 and TIFR/TH/93-2

QCD Critical Point: The Race is On

A critical point in the phase diagram of Quantum Chromodynamics (QCD), if established either theoretically or experimentally, would be as profound a discovery as the good-old gas-liquid critical point. Unlike the latter, however, first-principles based approaches are being employed to locate it theoretically. Due to the short lived nature of the concerned phases, novel experimental techniques are needed to search for it. The Relativistic Heavy Ion Collider (RHIC) in USA has an experimental program to do so. This short review is an attempt to provide a glimpse of the race between the theorists and the experimentalists as well as that of the synergy between them.Comment: 15 Pages, Invited Review for Praman

Impact of Z_2 monopoles and vortices on the deconfinement transition

The impact of Z_2-monopoles and vortices on the bulk and the deconfinement phase transitions of the SU(2) lattice gauge theory with a mixed Villain form of action is investigated by varying their numbers with appropriate chemical potentials. Suppressing the former shifts the line of deconfinement transitions in the coupling plane but it continues to behave also like the bulk transition line. We find separate deconfinement and bulk phase transitions on the same lattice, suggesting the two to be indeed coincident at higher adjoint couplings. Universality is restored when both monopoles and vortices are suppressed.Comment: LATTICE99(Finite Temp I), 3 pages, 3 eps figures, LaTeX, espcrc2.st

Exact chiral invariance at finite density on the lattice

We propose a lattice action for the overlap Dirac matrix with nonzero chemical potential which is shown to preserve the chiral invariance on the lattice exactly. We further demonstrate it to arise from the Domain wall by letting the chemical potential count only the physically relevant wall modes.Comment: 4 pages, RevTe