Search results for "Dirac equation"

Positron Production in Heavy Ion-Atom Collisions

1983

The question of pair creation in strong electrical fields is a very old problem. Already in 1929, within the framework of the new Dirac theory of the electron1, Klein considered the behaviour of an electron wave with a total energy E = ET + mec2 impinging on a one-dimensional step barrier potential Vo> mec2/e (fig. 1a). If the kinetic energy ET of an electron travelling on the z-axis from left to right is less than eVo, then for z>0 an exponentially damped wave function is expected as a solution of the Schrodinger equation. According to Klein’s calculations with the Dirac equation, this behaviour was also found for eVo-2mec2 <ET<eVo, but for a kinetic energy ET<eVo-2mec2 the wave function s…

Relativistic nuclear structure. II. Finite nuclei.

1990

Quantum walks as simulators of neutrino oscillations in a vacuum and matter

2016

We analyze the simulation of Dirac neutrino oscillations using quantum walks, both in vacuum and in matter. We show that this simulation, in the continuum limit, reproduces a set of coupled Dirac equations that describe neutrino flavor oscillations, and we make use of this to establish a connection with neutrino phenomenology, thus allowing to fix the parameters of the simulation for a given neutrino experiment. We also analyze how matter effects for neutrino propagation can be simulated in the quantum walk. In this way, important features, such as the MSW effect, can be incorporated. Thus, the simulation of neutrino oscillations with the help of quantum walks might be useful to explore the…

Relativistic effects in quasifree deuteron electrodisintegration compared to a covariant model

1994

Deuteron disintegration by electrons is calculated in a covariant model for the quasifree region, where final-state interaction and two-body currents can be negiected, and is compared to a phenomenological approach in which one adds to the nonrelativistic one-body current relativistic contributions of lowest order and the kinematic wave-function boost. It is shown that ap/M-reduction of the relativistic theory contains the expressions of the phenomenological approach. The inclusion of relativistic contributions leads to a less frame-dependent description and the deviation from the covariant theory becomes small at low and medium energy and momentum transfers. Furthermore, the dependence of …

The Axial Charge Renormalization in a Relativistic Description of Finite Nuclei

1994

Starting from a realistic One-Boson-Exchange model of the nucleon nucleon interaction the relativistic mean field for nucleons is determined within the Dirac Brueckner Hartree Fock approach for finite nuclei. The matrix elements of the axial charge operator evaluated for the solutions of the Dirac equation with this selfenergy are investigated. These matrix elements are enhanced with respect to the equivalent non relativistic ones obtained from the solutions of the Schr\"odinger equation with the non relativistic equivalent potential. The present results confirm at a qualitative level the results for the axial charge renormalization obtained with perturbative approaches. However, the result…

Properties of dense nuclear and neutron matter with relativistic nucleon-nucleon interactions.

1992

Within the framework of the Dirac-Brueckner (DB) approach, the properties of dense nuclear and neutron matter are investigated using realistic nucleon-nucleon (NN) interactions which are derived from relativistic meson-field theory and describe the two-nucleon system quantitatively. Single-particle potentials, equations of state, nucleon effective masses, Landau parameters, and speeds of sound are calculated and analyzed as functions of density, for both nuclear and neutron matter. In the DB approach, the equation of state comes out stiffer than in the most sophisticated nonrelativistic calculation, but softer than in the Walecka model. Possible extensions of the present approach to nucleon…

Nuclear ground-state properties in a relativistic Meson-Field theory

1986

We investigate the ability of a relativistic Mean-Field theory to reproduce nuclear ground state properties by an exhaustive fit to experimental data. We find that the bulk properties of nuclei from16O to208Pb can be adjusted very well. There remain problems with level density and fluctuations in the charge density similar as in fits using the conventional Skyrme Hartree-Fock model.

CP symmetry and thermal effects on Dirac bi-spinor spin–parity local correlations

2018

Intrinsic quantum correlations supported by the $SU(2)\otimes SU(2)$ structure of the Dirac equation used to describe particle/antiparticle states, optical ion traps and bilayer graphene are investigated and connected to the description of local properties of Dirac bi-spinors. For quantum states driven by Dirac-like Hamiltonians, quantum entanglement and geometric discord between spin and parity degrees of freedom - sometimes mapped into equivalent low energy internal degrees of freedom - are obtained. Such \textit{spin-parity} quantum correlations and the corresponding nonlocal intrinsic structures of bi-spinor fermionic states can be classified in order to relate quantum observables to th…

Asymptotic properties of the Dirac quantum cellular automaton

2016

We show that the Dirac quantum cellular automaton [Ann. Phys. 354 (2015) 244] shares many properties in common with the discrete-time quantum walk. These similarities can be exploited to study the automaton as a unitary process that takes place at regular time steps on a one-dimensional lattice, in the spirit of general quantum cellular automata. In this way, it becomes an alternative to the quantum walk, with a dispersion relation that can be controlled by a parameter, which plays a similar role to the coin angle in the quantum walk. The Dirac Hamiltonian is recovered under a suitable limit. We provide two independent analytical approximations to the long term probability distribution. It …

Bilayer graphene lattice-layer entanglement in the presence of non-Markovian phase noise

2018

The evolution of single particle excitations of bilayer graphene under effects of non-Markovian noise is described with focus on the decoherence process of lattice-layer (LL) maximally entangled states. Once that the noiseless dynamics of an arbitrary initial state is identified by the correspondence between the tight-binding Hamiltonian for the AB-stacked bilayer graphene and the Dirac equation -- which includes pseudovector- and tensor-like field interactions -- the noisy environment is described as random fluctuations on bias voltage and mass terms. The inclusion of noisy dynamics reproduces the Ornstein-Uhlenbeck processes: a non-Markovian noise model with a well-defined Markovian limit…