Finite Temperature and Density Effects in Planar QED

2011

We investigate planar Quantum ElectroDynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. Our preliminary results indicate that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak coupling region. We comment on possible implications to the quantum Hall effect in graphene.

Physical Review D, 2001

We study the deconfinement phase transition and monopole properties in the finite temperature 3D compact Abelian gauge model on the lattice. We predict the critical coupling as function of the lattice size in a simplified model to describe monopole binding. We demonstrate numerically that the monopoles are sensitive to the transition. In the deconfinement phase the monopoles appear in the form of a dilute gas of magnetic dipoles. In the confinement phase both monopole density and string tension differ from semiclassical estimates if monopole binding is neglected. However, the analysis of the monopole clusters shows that the relation between the string tension and the density of monopoles in charged clusters is in reasonable agreement with those predictions. We study the cluster structure of the vacuum in both phases of the model.

1988

The photon sector of Quantum Electrodynamics (QED) in one spatial dimension is analyzed a t high temperature to all orders of perturbation theory. The imaginary-time formalism is used. The photon self-energy and propagator a t finite tempexature with vanishing frequency are given to second order of perturbation theory. Based upon them, an improved perturbation theory which incorporates Debye screening if formulated. In the infinite-temperature limit, the photon sector becomes equivalent to a massive scalar boson field plus a maaslees pure gauge field and both are decoupled: all connected Green's functions with given external momenta much smaller than the temperature and containing, at least, one closedfermion loop with four or more vertices vanish. An approximate generating functional yielding all leading high-temperature corrections to all connected Green's functions is preaented. The Iadt result leads to establish for one spatial dimension a conjecture of Gross, Pisarski and Yaffe regarding the reduction of &ED to a sort of 144 theory a t high temperature. The leading high temperature contribution to the thermodynamic potential to all perturbativc orders: i) is given in terms of the dominant high temperature contribution to the twopoint photon Green's function for zero frequency, ii) is shown to be both ultraviolet and infrared finite.

Physical Review Letters, 1994

We present the three loop contribution (order e 4) to the pressure of massless quantum electrodynamics at nonzero temperature. The calculation is performed within the imaginary time formalism. Dimensional regularization is used to handle the usual, intermediate stage, ultraviolet and infrared singularities, and also to prevent overcounting of diagrams during resummation.

Journal of High Energy Physics, 2008

The confinement-deconfinement phase transition is explored by lattice numerical simulations in non-compact (2+1)-dimensional quantum electrodynamics with massive fermions at finite temperature. The existence of two phases, one with and the other without confinement of fractional charges, is related to the realization of the Z symmetry. The order parameter of this transition can be clearly identified. We show that it is possible to detect the critical temperature for a given value of the fermion mass, by exploiting suitable lattice operators as probes of the Z symmetry. Moreover, the large-distance behavior of the correlation of these operators permits to distinguish the phase with Coulombconfinement from the Debye-screened phase. The resulting scenario is compatible with the existence of a Berezinsky-Kosterlitz-Thouless transition. Some investigations are presented on the possible relation between chiral and deconfinement transitions and on the role of "monopoles".

2011

We investigate planar Quantum ElectroDynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. Our preliminary results indicate that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak coupling region. We comment on possible implications to the quantum Hall effect in graphene.

Journal of High Energy Physics

Planar quantum electrodynamics, in presence of tree-level Chern-Simons term, is shown to support bound state excitations, with a threshold, not present for the pure Chern-Simons theory. In the present case, the bound state gets destabilized by vacuum fluctuations. The bound state itself finds justification in the duality of the theory with massive topological vector field. Thermal fluctuations further destabilize this state, leading to smooth dissociation at high temperatures. Physical systems are suggested for observing such a bound state.

Physical Review D, 1987

An earlier work on finite-temperature renormalization and radiative corrections in QED is gen- eralized to incorporate finite-density effects. Some methods of quantum field theory have their ori- gin in many-body systems. Such theories account for finite-temperature and -density (FTD) effects in the quan- tum description and are known to possess nontrivial signi- ficance in heavy-ion physics and cosmology. A renewed interest in relativistic calculations in FTD recently arose from the fact that the spontaneously broken gauge symmetries can be restored at sufficiently high temperatures. ' Other effects such as deconfinement and supersymmetry breaking, although not so well understood, have more re- cently been found in finite-temperature field theories.

Physical Review D, 2012

We investigate planar quantum electrodynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. We argue that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak-coupling region. We extrapolate our lattice results to the quantum Hall effect in graphene.

Physics Letters B, 2019

Quantum polarization effects associated with the conformal anomaly in a static magnetic field background may generate a transverse electric current in the vacuum. The current may be produced either in an unbounded curved spacetime or in a flat spacetime in a physically bounded system. In both cases, the magnitude of the electric current is proportional to the beta-function associated with renormalization of the electric charge. In our article, we investigate the electric current density induced by the magnetic field in the vicinity of a Dirichlet boundary in the scalar QED. Using first-principle lattice simulations we show that the electric current, generated by this "conformal magnetic effect at the edge" (CMEE), is well described by the conformal anomaly provided the conformal symmetry is classically unbroken. Outside of the conformal limit, the current density is characterized by an anomalous power law near the edge of the system and by an exponential suppression of the current far away from the edge.