Comparison between the continuum threshold and the Polyakov loop as deconfinement order parameters

We study the relation between the continuum threshold s0 within finite energy sum rules and the trace of the Polyakov loop Φ in the framework of a nonlocal SU(2) chiral quark model, establishing a contact between both deconfinement order parameters at finite temperature T and chemical potential μ. In our analysis, we also include the order parameter for the chiral symmetry restoration, the chiral quark condensate. We found that s0 and Φ provide us with the same information for the deconfinement transition, both for the zero and finite chemical potential cases. At zero density, the critical temperatures for both quantities coincide exactly and, at finite μ both order parameters provide evidence for the appearance of a quarkyonic phase.Instituto de Física La PlataConsejo Nacional de Investigaciones Científicas y Técnica

Relation between the continuum threshold and the Polyakov loop with the QCD deconfinement transition

Using vector and axial-vector correlators within finite-energy sum rules with inputs from a chiral quark model, coupled to the Polyakov loop, with nonlocal vector interactions, we extend our previous work to confirm the equivalence between the continuum threshold s0 and the trace of the Polyakov loop Φ as order parameters for the deconfinement transition at finite temperature T and quark chemical potential μ. The obtained results are in agreement with our initial conclusion, where we showed that s0(T,μ) and Φ(T,μ) provide the same information for the QCD deconfinement transition.Fil: Carlomagno, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; ArgentinaFil: Loewe, Marcelo. Pontificia Universidad Catolica de Chile. Facultad de Física. Departamento de Física; Chile. University of Cape Town; Sudáfric

On the critical end point in a two-flavor linear sigma model coupled to quarks

We use the linear sigma model coupled to quarks to explore the location of the phase transition lines in the QCD phase diagram from the point of view of chiral symmetry restoration at high temperature and baryon chemical potential. We compute analytically the effective potential in the high- and low-temperature approximations up to sixth order, including the contribution of the ring diagrams to account for the plasma screening properties. We determine the model parameters, namely, the couplings and mass-parameter, from conditions valid at the first order phase transition at vanishing temperature and, using the Hagedorn limiting temperature concept applied to finite baryon density, for a critical baryochemical potential of order of the nucleon mass. We show that when using the set of parameters thus determined, the second order phase transition line (our proxy for the crossover transition) that starts at finite temperature and zero baryon chemical potential converges to the line of first order phase transitions that starts at zero temperature and finite baryon chemical potential to determine the critical end point to lie in the region 5.02<\mu_B^{\mbox{CEP}}/T_c<5.18, 0.14, where $T_c$ is the critical transition temperature at zero baryon chemical potential.Comment: 11 pages, 3 figures, discussion extended, explicit calculations included in appendices and version accepted for publication in EPJ

Chemical sensing with graphene: A quantum field theory perspective

We studied theoretically the effect of a low concentration of adsorbed polar molecules on the optical conductivity of graphene, within the Kubo linear response approximation. Our analysis is based on a continuum model approximation that includes up to next-to-nearest neighbors in the pristine graphene effective Hamiltonian. Our results show that the conductivity can be expressed in terms of renormalized quasiparticle parameters vF , M , and μ that include the effect of the molecular surface concentration ndip and dipolar moment P, thus providing a quantum field theory approach to model a graphene-based chemical sensor.Fil: Falomir, Horacio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Loewe, Marcelo. Pontificia Universidad Católica de Chile; ChileFil: Muñoz, Enrique. Pontificia Universidad Católica de Chile; Chil

Electromagnetic nucleon form factors from QCD sum rules

The electromagnetic form factors of the nucleon, in the space-like region, are determined from three-point function Finite Energy QCD Sum Rules. The QCD calculation is performed to leading order in perturbation theory in the chiral limit, and to leading order in the non-perturbative power corrections. The results for the Dirac form factor, F1(q2), are in very good agreement with data for both the proton and the neutron, in the currently accessible experimental region of momentum transfers. This is not the case, though, for the Pauli form factor F2(q2), which has a soft q2-dependence proportional to the quark condensate h0|q¯q|0i