Three and Two Colours Finite Density QCD at Strong Coupling: A New Look

Simulations in finite density, beta=0 lattice QCD by means of the Monomer-Dimer-Polymer algorithm show a signal of first order transition at finite temporal size. This behaviour agrees with predictions of the mean field approximation, but is difficult to reconcile with infinite mass analytical solution. The MDP simulations are considered in detail and severe convergence problems are found for the SU(3) gauge group, in a wide region of chemical potential. Simulations of SU(2) model show discrepancies with MDP results as well.Comment: 18 pages, 9 figures, to appear in Nucl. Phys.

Rigorous arguments against current wisdoms in finite density QCD

QCD at finite chemical potential is analytically investigated in the region of large bare fermion masses. We show that, contrary to the general wisdom, the phase of the fermion determinant is irrelevant at zero temperature. However if the system is put at finite temperature, the contribution of the phase is finite. We also discuss on the quenched approximation and suggest that the origin of the failure of this approximation in finite density QCD could relay on the fundamental role that Pauli exclusion principle plays in this case.Comment: 16 pages, 5 figure

Phase transition(s) in finite density QCD

The Grand Canonical formalism is generally used in numerical simulations of finite density QCD since it allows free mobility in the chemical potential $\mu$. We show that special care has to be used in extracting numerical results to avoid dramatic rounding effects and spurious transition signals. If we analyze data correctly, with reasonable statistics, no signal of first order phase transition is present and results using the Glasgow prescription are practically coincident with the ones obtained using the modulus of the fermionic determinant.Comment: 6 pages, 5 ps figs. To appear in Proceedings of "QCD at Finite Baryon Density" workshop, Bielefeld, 27-30 April 199

Finite density QCD with heavy quarks

In the large fermion mass limit of QCD at finite density the structure of the partition function greatly simplifies and can be studied analytically. We show that, contrary to general wisdom, the phase of the Dirac determinant is relevant only at finite temperature and can be neglected for zero temperature fields.Comment: LATTICE98(hightemp), 3 pages, 3 figure

New Ideas in Finite Density QCD

We introduce a new approach to analyze the phase diagram of QCD at finite chemical potential and temperature, based on the definition of a generalized QCD action. Several details of the method will be discussed, with particular emphasis on the advantages respect to the imaginary chemical potential approach.Comment: Talk presented at Lattice2004 (non-zero), Fermilab, June 21-26, 2004; 3 pages, 2 figure

Strongly Coupled QCD at Finite Baryon Density

The analytical results obtained in the infinite mass and strong coupling limits of QCD are difficult to reconcile with the predictions of the Monomer Dimer Polymer algorithm. We have reconsidered in detail the results obtained with this simulation scheme and evidences of severe convergence problems are presented for the SU(3) and SU(2) gauge group.Comment: LATTICE99(Finite Temperature and Density), 3 pages, 3 postscript figure

Disappointing model for ultrahigh-energy cosmic rays

Data of Pierre Auger Observatory show a proton-dominated chemical composition of ultrahigh-energy cosmic rays spectrum at (1 - 3) EeV and a steadily heavier composition with energy increasing. In order to explain this feature we assume that (1 - 3) EeV protons are extragalactic and derive their maximum acceleration energy, E_p^{max} \simeq 4 EeV, compatible with both the spectrum and the composition. We also assume the rigidity-dependent acceleration mechanism of heavier nuclei, E_A^{max} = Z x E_p^{max}. The proposed model has rather disappointing consequences: i) no pion photo-production on CMB photons in extragalactic space and hence ii) no high-energy cosmogenic neutrino fluxes; iii) no GZK-cutoff in the spectrum; iv) no correlation with nearby sources due to nuclei deflection in the galactic magnetic fields up to highest energies.Comment: 4 pages, 7 figures, the talk presented by A. Gazizov at NPA5 Conference, April 3-8, 2011, Eilat, Israe

Approaching Space Time Through Velocity in Doubly Special Relativity

We discuss the definition of velocity as dE/dp, where E,p are the energy and momentum of a particle, in Doubly Special Relativity (DSR). If this definition matches dx/dt appropriate for the space-time sector, then space-time can in principle be built consistently with the existence of an invariant length scale. We show that, within different possible velocity definitions, a space-time compatible with momentum-space DSR principles can not be derived.Comment: 11 pages, no figures, minor changes, references added, final version to appear in PR

Probability Distribution Function of the Diquark Condensate in Two Colours QCD

We consider diquark condensation in finite density lattice SU(2). We first present an extension of Vafa-Witten result, on spontaneous breaking of vector-like global symmetries, that allows us to formulate a no-go theorem for diquark condensation in a region of the chemical potential-mass parameter space. We then describe a new technique to calculate diquark condensation at any number of flavours directly at zero external source without using any potentially dangerous extrapolation procedure. We apply it to the strong coupling limit and find compelling evidences for a second order phase transition, where a diquark condensate appears, as well as quantitative agreement between lattice results and low-energy effective Lagrangian calculations.Comment: 21 pages, 7 figure

Report on the EU-US Workshop on Large Scientific Databases

This joint workshop was set up under the auspices of the Joint European Commission/National Science Foundation Strategy Group that met in Budapest in September 1998. The meeting derived from a joint collaboration agreement between the EC and NSF, signed by Dr. George Metakides (Director of Information Technologies for the EC) and Prof. Juris Hartmanis (Director of Computer and Information Science and Engineering at the NSF). Some themes that were identified include: digital libraries human-centered computing and virtual environments large scientific databases, and intelligent implants This report expresses the conclusions and recommendations of the Workshop on Large Scientific Databases, held in Annapolis, Maryland, USA in September 1999. The purpose of the workshop was to develop a report to the funding agencies outlining a possible solicitation to the research community, with emphasis on joint European-US work on Large Scientific Databases. Before the workshop, each participant submitted a position paper (these are available at the web site http://www.cacr.caltech.edu/euus). The results of the position papers, presentations, and group discussion are summarized in this report. There were 12 participants from Europe and 12 from the United States, and they are listed at the end of this report. The last section of this report describes possible funding mechanisms