185 research outputs found
Wilson fermions and the topological charge on the lattice
No full textKarsch F, Seiler E, Stamatescu IO. Wilson fermions and the topological charge on the lattice. Nuclear Physics, B. 1986;271(2):349-368.We investigate the realization on the lattice of the relation between the chiral properties of the fermions and the topological properties of the gauge field. A lattice definition of the topological charge density via the U(1) Adler-Bardeen anomaly is analysed with the help of given configurations of nontrivial topology and for 2-dimensional quenched QED
On the Assumption That Our Concepts ‘Structure the Material of Our Experience’
No full textThe general assumption that human knowledge depends, firstly, on our faculty to receive some raw material from the world outside us and, secondly, on our faculty to ‘organize’ or to ‘structure’ this material by means of certain concepts may sound quite innocent. At a close look, however, it appears to be anything but clear. In an article entitled “On the Very Idea of a Conceptual Scheme”, the philosopher Donald Davidson has called this assumption “the third dogma of empiricism” (Davidson 1984, 189)
A model for QCD at high density and large quark mass
No full textWe study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion and choosing Polyakov-type loops as the main dynamical variables representing the fermionic matter. To get a first idea of the phase structure, the model is analyzed in strong coupling expansion and using a mean field approximation. In numerical simulations, the model still shows the so-called sign problem, a difficulty peculiar to nonzero chemical potential, but it permits the development of algorithms which ensure a good overlap of the Monte Carlo ensemble with the true one. We review the main features of the model and present calculations concerning the dependence of various observables on the chemical potential and on the temperature, in particular, of the charge density and the diquark susceptibility, which may be used to characterize the various phases expected at high baryonic density. We obtain in this way information about the phase structure of the model and the corresponding phase transitions and crossover regions, which can be considered as hints for the behavior of nonzero density QCD
QCD on anisotropic lattices
No full textBurgers G, Karsch F, Nakamura A, Stamatescu IO. QCD on anisotropic lattices. Nuclear Physics, B. 1988;304:587-600
DETERMINATION OF SCALE PARAMETERS ON ANISOTROPIC LATTICES
No full textKarsch F, Burgers G, Nakamura A, Stamatescu IO. DETERMINATION OF SCALE PARAMETERS ON ANISOTROPIC LATTICES. 1987
QCD thermodynamics with light quarks. Quantum corrections to the fermionic anisotropy parameter
No full textKarsch F, Stamatescu IO. QCD thermodynamics with light quarks. Quantum corrections to the fermionic anisotropy parameter. Physics Letters, B. 1989;227(1):153-160.We determine the O(g 2) corrections to the anisotropy parameter in the fermionic action, which are required to guarantee a rotational invariant continuum limit on anisotropic lattices. We show the importance of these quantum corrections for QCD thermodynamics on isotropic lattices. Only after including these corrections do we find, on large lattices, agreement between lattice and continuum perturbation theory at finite temperature. The implied renormalization of the operators used in Monte Carlo simulations to measure the energy density leads to a 20% reduction of the fermionic part of the energy density which, to a large extent, compensates the previously found overshooting in the gluonic sector. We reanalyze existing Monte Carlo data for the thermodynamics of QCD with light quarks and extract the entropy density. We find that immediately above the chiral transition the entropy density is already close to the ideal gas value
P oS(LATTICE 2007)184 The High Density Region of QCD from an Effective Model
No full textWe study the high density region of QCD within an effective model obtained in the frame of the hopping parameter expansion and choosing Polyakov-type loops as the main dynamical variables representing the fermionic matter. This model still shows the so-called sign problem, a diffi-culty peculiar to non-zero chemical potential, but it permits the development of algorithms which ensure a good overlap of the simulated Monte Carlo ensemble with the true one. We review the main features of the model and present results concerning the dependence of var-ious observables on the chemical potential and on the temperature, in particular of the charge density and the Polykov loop susceptibility, which may be used to characterize the various phases expected at high baryonic density. In this way, we obtain information about the phase struc-ture of the model and the corresponding phase transitions and cross over regions, which can be considered as hints about the behaviour of non-zero density QCD. The XXV International Symposium on Lattice Field Theor
The SU(3) deconfinement phase transition in the presence of quarks
No full textHasenfratz P, Karsch F, Stamatescu IO. The SU(3) deconfinement phase transition in the presence of quarks. Physics Letters, B. 1983;133(3-4):221-226.The fate of the deconfinement phase transition is studied as a function of the quark mass on a 8 3 × 2 lattice. The first order phase transition present in the pure SU(3) lattice gauge theory weakens rapidly as the quark mass is decreased and no such transition is observed below a critical mass value. This critical mass appears to be large, of the order of GeV
Study of the phase structure of an SU(3) Higgs model at finite temperature
No full textKarsch F, Seiler E, Stamatescu IO. Study of the phase structure of an SU(3) Higgs model at finite temperature. Physics Letters, B. 1985;157(1):60-64.We analyse numerically an SU(3) Higgs model with complete symmetry breaking and radial degree of freedom on asymmetric, periodic lattices. The character of both the Higgs and deconfining transitions is found to depend on the Higgs self-coupling and on a parameter which may simulate the number of flavours. In particular, an increase in the latter leads to the disappearance of the deconfining transition for small Higgs masses
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