49270375
The correlation lengths and the order of the phase transition in three-dimensional Z 3 symmetric models
We present a high statistics Monte Carlo investigation of three-dimensional Z 3 symmetric models, which are related to SU(3) pure gauge theory at finite temperature. From the finite size scaling behaviour of bulk properties and the existence of metastable states, we conclude that these models exhibit a first-order phase transition. We have also performed detailed correlation length measurements in a cylindrical geometry with periodic boundary conditions as well as with a cold wall in the longitudinal direction. The correlation length, which appears to be independent of the boundary conditions, becomes very large near the critical point. Nonetheless, our data suggest that the correlation length developes a discontinuity at the critical point in the infinite volume limit.
122166973
The phase diagram of QCD: methods and logic of the comparison of experiments and theory
Abstract A small review of the phase diagram of QCD is presented. This is followed by a discussion of the conditions under which experimental data on the fluctuations of conserved quantities in heavy-ion collisions can be treated in the grand canonical ensemble. A robust method for detecting the presence of a nearby critical point in experiments is given. There is a short discussion of the need for non-Gaussian error analysis.
123004962
Flavour degrees of freedom and the transition temperature in QCD
We study the finite temperature transition in QCD with four flavours of dynamical quarks. Our simulation is performed on an 8×16 3 lattice for quarks of mass ma=0.01. At the coupling β c =5.15, we find long-lived metastable states, as well as an abrupt change in the entropy density, suggesting a first order phase transition. Using presently available results from corresponding calculations of the hadron masses and the chiral condensate, this gives us a transition temperature T c ≅100 MeV, which is a factor two lower than the transition temperature found in quenched QCD.
17443615
Lattice QCD for RHIC
I briefly introduce the methods by which lattice QCD predictions for RHIC are obtained. Next I deal with lattice determinations of strangeness production and event-to-event fluctuations of conserved quantities. I also present a new diagrammatic method for computing derivatives with respect to chemical potentials, and conclude with discussions of some tests of thermal perturbation theory which follow.
121387686
Hybrid Monte Carlo simulations of a two-dimensional gauge theory
Through a study of the dynamics of the two-dimensional U(1) pure gauge theory we find exponential slowing down in barrier penetration problems. We verify that the dynamical critical exponent in HMC can be tuned exactly to 1, and that normal and gauge fixed updates have equal cost.
119431013
A precise determination of T_c in QCD from scaling
Existing lattice data on the QCD phase transition are analyzed in renormalized perturbation theory. In quenched QCD it is found that T_c scales for lattices with only 3 time slices, and that T_c/Lambda_msbar=1.15 \pm 0.05. A preliminary estimate in QCD with two flavours of dynamical quarks shows that this ratio depends on the quark mass. For realistic quark masses we estimate T_c/Lambda_msbar=0.49 \pm 0.02. We also investigate the equation of state in quenched QCD at 1-loop order in renormalised perturbation theory.
15293327
Liquid-Gas Phase Transition in Nuclear Multifragmentation
Heavy-ion collisions allow one to pump energy into a nuclear system. In central collisions of equal size nuclei one can also create a significant amount of compression using high energy nuclear beams. The possibility of studying nuclei far from normal conditions raises the question: can we study phase transitions in nuclei similar, for instance, to the way, one can study phase transition in water? This is the subject of the present article.
121643346
Study on nuclear composition of cosmic rays around the knee utilizing muon multiplicity with GRAPES-3 experiment at Ooty
The composition and energy spectrum of primary cosmic rays (PCRs) are the only observables available at ultra-high energies to understand the nature of sources accelerating protons and other nuclei to 1000 TeV and beyond. These observables have been measured up to 1000 TeV, directly with detectors flown aboard balloons and satellites. The measurements at > 1000  TeV are obtained indirectly, from ground based observations of extensive air showers (EAS). However, their interpretation depends on rather inadequate knowledge of hadronic interactions at > 1000  TeV . The GRAPES-3 experiment has been designed to study the EAS at ∼ 30  TeV to provide a sizable overlap with the results from direct measurements, enabling selection of a suitable model of hadronic interactions. We present here the salient features of GRAPES-3 experiment and some details of muon multiplicity distributions (MMDs) observed with a 560 m2 muon detector as a function of shower size ( N e ) fro analysis of 560 days of data. A comparison of GRAPES-3 results with direct measurements over the energy region 100 – 1000 TeV is presented to show the suitability of hadronic interaction generator “SIBYLL” for the interpretation of EAS data. We presented the energy spectrum of five nuclear groups (H, He, N, Al and Fe) with good statistics for 100 – 10, 000 TeV.
124703371
FEL ACTIVITIES IN INDIA
We are building a Compact Ultrafast TErahertz FreeElectron Laser (CUTE-FEL), designed to lase from 50 – 100 μm. The FEL will be driven by a 10-15 MeV electron beam from a Plane-Wave Transformer (PWT) linac. The undulator is a 5 cm period, 2.5 m long PPM planar undulator. We present details of the FEL design and the present status of activities. We also present very preliminary plans for a short-wavelength SASE FEL in India.
18664179
Parametrizing yields of nuclear multifragmentation
We consider a model where, for a finite disintegrating system, yields of composites can be calculated to arbitrary accuracy. An analytic answer for yields is also known in the thermodynamic limit. In the range of temperature and density considered in this work, the model has a phase transition. This phase transition is first order. The analytic expression for yields of composites, in the thermodynamic limit, does not conform to the expression $ =a^{-\tau}f(a^{\sigma} (T-T_c))$ where, the usual identification would be that $T_c$ is the critical temperature and $\tau,\sigma$ are critical exponents. Nonetheless, for finite systems, we try to fit the yields with the above expression. A minimisation procedure is adopted to get the parameters $T_c,\tau$ and $\sigma$. While deviations from the formula are not negligible, one might believe that the deviations are consistent with the corrections attributable to finite particle number effects and might then conclude that one has deduced at least approximately the values of critical parameters. This exercise thus points to difficulties of trying to extract critical parameters from data on nuclear disintegration. An interesting result is that the value of $T_c$ deduced from the ``best'' fit is very close to the temperature at which the first order phase transition occurs in the model. The yields calculated in this model can also be fitted quite well by a parametrisation derived from a droplet model.
121230523
NONLINEAR HADRON COUPLINGS FROM DIVERGENCE CONDITIONS. I. PIONS AND NUCLEONS.