Alejandro Cabo Montes de Oca

Spontaneous symmetry breaking approach to La2CuO4 properties: Hints for matching the Mott and Slater pictures

Abstract Special solutions of the Hartree–Fock (HF) problem for Coulomb interacting electrons described by a simple model of the Cu–O planes in La 2 CuO 4 are presented. One of the mean field states obtained, is able to predict some of the most interesting properties of this material, such as its insulator character and the antiferromagnetic order. The natural appearance of pseudogaps in some states of this material is also indicated by another of the HF states obtained. These surprising results follow after eliminating spin and crystal symmetry restrictions usually imposed on the single particle HF orbitals, by employing the rotational invariant formulation of the HF scheme originally introduced by Dirac. Therefore, it is exemplified here, how up to know considered strong correlation effects, can be described by improving the HF solution of the considered system. In other words, it has been argued, that defining correlation effects as the ones shown by the system and not predicted by the HF best (lowest energy) solution, allows to explain important, up to know considered as strong correlation properties, as simple mean field ones. The discussion also helps to clarify the role of the antiferromagnetism and pseudogaps in the physical properties of the HTSC materials and indicates a promising way to start conciliating the Mott and Slater pictures in the physics of the transition metal oxides and other strongly correlated electron systems.

Hartee Fock Symmetry Breaking Effects in La 2 CuO 4 : Hints for connecting the Mott and Slater Pictures and Pseudogap Prediction

Abstract: This work expands the results and derivations presented in a recent letter. It isargued that symmetry breaking Hartree-Fock (HF) solutions of a simple model of the Cu-Oplanes in La 2 CuO 4 , are able to describe the insulator and antiferromagnetic characters ofthis material. Then, this classical primer of a Mott insulator is alternatively obtained hereas an exact Slater insulator within the simplest of the firstprinciples schemes. Moreover,pseudogap HF states are also predicted. The maximal energy gap of 100 meV over theFermi surface of this wavefunction, reasonably well matches the ARPES upper pseudogapmeasurements for La 2 CuO 4 in the zero doping limit. These surprising results followed aftereliminating spin and crystal symmetry constraints usually imposed on the HF orbitals. Thediscussion helps to clarify the role of the antiferromagnetism and pseudogaps in the physicsoftheHTSCmaterialsandindicatesapromisingwaytostartconciliatingtheMottandSlaterpictures for the description of the transition metal oxides.Keywords: symmetry breaking; strongly correlated electron systems; Magnetism; HTc su-percondutivity; HTSC; pseudgaps; MIS; entanglementClassification: PACS 71.10.Fd,71.15.Mb,71.27.+a,71.30.+h,74.20.-z,74.25.Ha,74.25.Jb,74.72.-h

Vacuum polarization of massive spinor fields in static black-string backgrounds

The renormalized mean value of the quantum Lagrangian and the corresponding components of the energy-momentum tensor for massive spinor fields coupled to an arbitrary gravitational field configuration having cylindrical symmetry are analytically evaluated using the Schwinger-DeWitt approximation, up to second order in the inverse mass value. The general results are employed to explicitly derive compact analytical expressions for the quantum mean Lagrangian and Energy-Momentum tensor in the particular background of the black-string spacetime.

Quantization of massive scalar fields over static black string backgrounds

Grupo de F´isica Te´orica, ICIMAF, Calle E No. 309, esq. a 15 Vedado, C. Habana,Cuba.(Dated: February 1, 2008)The renormalized mean value of the corresponding components of the Energy-Momentum tensorfor massive scalar fields coupled to an arbitrary gravitational field configuration having cylindricalsymmetry are analytically evaluated using the Schwinger-DeWitt approximation, up to second orderin the inverse mass value. The general results are employed to explicitly derive compact analyticalexpressions for the Energy-Momentum tensor in the particular background of the Black-String space-time. In the case of the Black String considered in this work, we proof that a violation of the weakenergy condition occur at the horizon of the space-time for values of the coupling constant, thatinclude as particular cases the most interesting of minimal and conformal coupling.

Particle dynamics in a relativistic invariant stochastic medium

The dynamics of particles moving in a medium defined by its relativistically invariant stochastic properties is investigated. For this aim, the force exerted on the particles by the medium is defined by a stationary random variable as a function of the proper time of the particles. The equations of motion for a single one-dimensional particle are obtained and numerically solved. A conservation law for the drift momentum of the particle during its random motion is shown. Moreover, the conservation of the mean value of the total linear momentum for two particles repelling each other according to the Coulomb interaction also follows. Therefore, the results indicate the realization of a kind of stochastic Noether theorem in the system under study.

Newton-like equations for a radiating particle

Second order Newton equations of motion for a radiating particle are presented. It is argued that the trajectories obeying them also satisfy the Abraham-Lorentz-Dirac (ALD) equations for general 3D motions in the non-relativistic and relativistic limits. The case of forces only depending of the proper time is here considered. For these properties to hold, it is sufficient that the external force to be infinitely smooth and that a series formed with its time derivatives converges. This series define in a special local way the effective forces entering the Newton equations. When the external force vanishes in an open vicinity of a given time, the effective one also becomes null. Thus, the proper solutions of the effective equations can not show runaway or pre-acceleration effects. The Newton equations are numerically solved for a pulsed force given by an analytic function along the proper time axis. The simultaneous satisfaction of the ALD equations is numerically checked. Further, a set of modified ALD equations for almost everywhere infinitely smooth forces, but including step like discontinuities in some points is also presented for the case of collinear motions. The form of the equations supports the statement argued in a previous work, about that the causal Lienard-Wiechert field solution surrounding a radiating particle, implies that the effective force on the particle should instantaneously vanish when the external force is retired. The modified ALD equations proposed in the previous work are here derived in a generalized way including the same effect also when a the force is instantly connected.