Influence of the isospin and hypercharge chemical potentials on the location of the CEP in the mu_B-T phase diagram of the SU(3)_L x SU(3)_R chiral quark model

We investigate the influence of the asymmetric quark matter (rho_u\ne rho_d\ne rho_s) on the mass of the quasiparticles and the phase diagram of the chiral quark model parametrized at one-loop level of the renormalized theory, using the optimized perturbation theory for the resummation of the perturbative series. The effect of various chemical potentials introduced in the grand canonical ensemble is investigated with the method of relativistic many-body theory. The temperature dependence of the topological susceptibility is estimated with the help of the Witten-Veneziano mass formula.Comment: RevTeX4, 13 pages, 6 figures, version accepted for publication in Phys. Rev.

Influence of the Polyakov loop on the chiral phase transition in the two flavor chiral quark model

The SU(2)_L x SU(2)_R chiral quark model consisting of the (sigma,pi) meson multiplet and the constituent quarks propagating on the homogeneous background of a temporal gauge field is solved at finite temperature and quark baryon chemical potential mu_q using an expansion in the number of flavors N_f, both in the chiral limit and for the physical value of the pion mass. Keeping the fermion propagator at its tree-level, several approximations to the pion propagator are investigated. These approximations correspond to different partial resummations of the perturbative series. Comparing their solution with a diagrammatically formulated resummation relying on a strict large-N_f expansion of the perturbative series one concludes that only when the local part of the approximated pion propagator resums infinitely many orders in 1/N_f of fermionic contributions a sufficiently rapid crossover transition at mu_q=0 is achieved allowing for the existence of a tricritical point or a critical end point in the mu_q-T phase diagram. The renormalization and the possibility of determining the counterterms in the resummation provided by a strict large-N_f expansion are investigated.Comment: 20 pages, 7 figures, 5 graphs, and 3 tables; uses revtex4-1, minor corrections and investigation of the influence of the pion-fermion setting-sun integral on the field equations for the Polyakov loop and its conjugate. Version published in the Phys. Rev. D journa

Systematics of High Temperature Perturbation Theory: The Two-Loop Electron Self-Energy in QED

In order to investigate the systematics of the loop expansion in high temperature gauge theories beyond the leading order hard thermal loop (HTL) approximation, we calculate the two-loop electron proper self-energy in high temperature QED. The two-loop bubble diagram contains a linear infrared divergence. Even if regulated with a non-zero photon mass M of order of the Debye mass, this infrared sensitivity implies that the two-loop self-energy contributes terms to the fermion dispersion relation that are comparable to or even larger than the next-to-leading-order (NLO) contributions at one-loop. Additional evidence for the necessity of a systematic restructuring of the loop expansion comes from the explicit gauge parameter dependence of the fermion damping rate at both one and two-loops. The leading terms in the high temperature expansion of the two-loop self-energy for all topologies arise from an explicit hard-soft factorization pattern, in which one of the loop integrals is hard, nested inside a second loop integral which is soft. There are no hard-hard contributions to the two-loop Sigma at leading order at high T. Provided the same factorization pattern holds for arbitrary ell loops, the NLO high temperature contributions to the electron self-energy come from ell-1 hard loops factorized with one soft loop integral. This hard-soft pattern is both a necessary condition for the resummation over ell to coincide with the one-loop self-energy calculated with HTL dressed propagators and vertices, and to yield the complete NLO correction to the self-energy at scales ~eT, which is both infrared finite and gauge invariant. We employ spectral representations and the Gaudin method for evaluating finite temperature Matsubara sums, which facilitates the analysis of multi-loop diagrams at high T.Comment: 63 pages, 10 figures. Published version. Main differences from v1: (1) Gaudin method explained in more detail; (2) Full expression (3.9) for Two-Loop Bubble Self-Energy with no need to expand in M; (3) Appendix C eliminated and incorporated in Secs. 4 and 5; (4) Examples of the breakdown of HTL resummation added to summary and Discussion in Sec.

Beyond HTL: The Classical Kinetic Theory of Landau Damping for Selfinteracting Scalar Fields in the Broken Phase

The effective theory of low frequency fluctuations of selfinteracting scalar fields is constructed in the broken symmetry phase. The theory resulting from integrating fluctuations with frequencies much above the spontanously generated mass scale $(p_0>>M)$ is found to be local. Non-local dynamics, especially Landau damping emerges under the effect of fluctuations in the $p_0 \sim M$ region. A kinetic theory of relativistic scalar gas particles interacting via their locally variable mass with the low frequency scalar field is shown to be equivalent to this effective field theory for scales below the characteristic mass, that is beyond the accuracy of the Hard Thermal Loop (HTL) approximation.Comment: 5 pages, Latex, uses sprocl.sty, to be published in the Proceedings of SEWM 98 Conference Copenhagen, Denmark 2-5 December 199

The effect of the Polyakov loop on the chiral phase transition

The Polyakov loop is included in the SU(2)_L x SU(2)_R chiral quark-meson model by considering the propagation of the constituent quarks, coupled to the (sigma,pi) meson multiplet, on the homogeneous background of a temporal gauge field, diagonal in color space. The model is solved at finite temperature and quark baryon chemical potential both in the chiral limit and for the physical value of the pion mass by using an expansion in the number of flavors N_f. Keeping the fermion propagator at its tree-level, a resummation on the pion propagator is constructed which resums infinitely many orders in 1/N_f, where O(1/N_f) represents the order at which the fermions start to contribute in the pion propagator. The influence of the Polyakov loop on the tricritical or the critical point in the mu_q-T phase diagram is studied for various forms of the Polyakov loop potential.Comment: 8 pages, 3 figures, uses svepjCONF.clo, contribution to the International Workshop on Hot & Cold Baryonic Matter 2010, 15-20 August, Budapest, Hungar

The Economic Situation of Individual (Family) Farms in Hungary

Combined elaboration of the first and second parts of papers prepared for presentation at the IAMO FORUM 2007 Halle, Germany 24-29 June 2007 and the IAAE-EAAE 104th seminar Budapest, Hungary 6-8 September 2007. In 2003 a research study looked at the position of smallholders; the survey was carried out using questionnaires and interviews. The farms included in the survey were situated in 3 counties in the Southern Great Plain of Hungary and in 3 counties of the western part of the country (Transdanubia). The results of the survey showed that there was a firm tendency of concentration among the Hungarian individual farms. Though their average size is about 3 ha, the number and area of farms over 50 ha size are rapidly growing and taking a significant part of the total individual agricultural area. The number of small farms is great but their total farming area is relatively small. The concentration takes place primarily due to renting. The land market is sluggish mainly owing to the land-buying restrictions and the small intention to sell of those owners who are waiting for higher prices. Land prices are low but rising, especially on the Western border of the country, near to Austria. The dominance of arable production and within that cereal production, especially on the larger individual farms, points to a prevalence of extensive farming The present support and subsidy system fortifies this tendency. When comparing the Southern Plain with western Transdanubia, it can be said that agricultural production is greater in the former region and more people are involved in agriculture. There is a higher share of under-cover production of vegetables and ornamental plants and animal husbandry. However, it seems that in western Transdanubia the spirit of enterprise is stronger than in the Southern Plain: more farmers enter into contractual agreements, more farmers make use of credits and subsidies, and the farms operate with greater profitability. Nevertheless, the proximity of western Transdanubia to industrial and service centers and, furthermore, its closeness to Austria tend to suppress agricultural activities. The regression analyses with respect to efficiency and profitability and the cluster analyses supported the assessments of the descriptive analyses and produced the following main conclusions: the larger farms, farmed by younger and better-educated individuals, are more efficient and profitable than the others. Furthermore, farmers with significant conceptions for development seem to achieve greater profitability.agricultural production, family farms, land tenure, land use, trade, finances, profitability, Consumer/Household Economics, Farm Management,

Effect of the scalar condensate on the linear gauge field response in the Abelian Higgs model

The effective equations of motion for low-frequency mean gauge fields in the Abelian Higgs model are investigated in the presence of a scalar condensate, near the high temperature equilibrium. We determine the current induced by an inhomogeneous background gauge field in the linear response approximation up to order $e^4$, assuming adiabatic variation of the scalar fields. The physical degrees of freedom are found and a physical gauge choice for the numerical study of the combined Higgs+gauge evolution is proposed.Comment: 11 pages, latex, no figure