arXiv subjects
Publications and source records attributed to M. C. Nemes.
The dynamics of the composition of uniform Bose condensates involving two species capable of reciprocal interconversion is treated in terms of a collective quasi-spin model. This collective model quickly reduces to classical form towards the thermodynamic limit. Quantum solutions are easily obtained numerically short of this limit which give insight into the dynamically relevant correlation processes.
We show that two-atom correlation measurements of the type involved in a recent experimental study of the evolution of a mesoscopic superposition state prepared in a definite mode of a high-Q cavity can be used to determine the eigenvalues of the reduced density matrix of the field, provided the assumed dynamical conditions are actually fulfilled to experimental accuracy. These conditions involve i) a purely dispersive coupling of the field to the Rydberg atoms used to manipulate and to monitor the cavity field, and ii) the effective absence of correlations in the ground state of the system consisting of the cavity coupled to the ``reservoir'' which accounts for the decoherence and damping processes. A microscopic calculation at zero temperature is performed and compared to master equation results.
We show how nonrelativistic many body techniques can be used to study quantum corrections to the classical limit, in particular of the $SU(2)$ Lipkin Model. We show that the quantum corrections are essentially of two types: unitary and nonunitary. In this work we perform a detailed study of the unitary corrections. They can be cast in Hamiltonian form and are shown to double the number of degrees of freedom. As a consequence chaotic behavior emerges. We show that this semiquantal chaos is the mechanism trough which tunneling is effected. We also show that these corrections systematically improve the classical results and propose some quantitative measure of this improvement.
The purpose of this paper is to formulate an action principle which allows for the construction of a classical lagrangean including both electric and magnetic currents. The lagrangean is non-local and shown to yield all the expected (local) equations for dual electrodynamics.
We calculate the one-quark-loop amplitude for the low energy $γγ\toππ$ collision in the context of the Nambu and Jona-Lasinio model with scalar and pseudoscalar four quark couplings to all orders in the external momenta. We show that the NJL predictions for the $γγ\toπ^+π^-$ reaction are not far from the Born amplitude, which is close to the data, and is compatible with the chiral perturbation theory estimations. We determine the corrections given by the NJL model in leading order of $1/N_c$ to the chiral loop amplitude for $γγ\toπ^0π^0$. Numerical results for the $γγ\rightarrowππ$ cross sections and for pion polarizabilities are given.
We derive simple and physically transparent expressions for the contribution of the strong interaction to one nucleon removal processes in peripheral relativistic heavy ion collisions. The coherent contribution,i.e, the excitation of a giant dipole resonance via meson exchange is shown to be negligible as well as interference between coulomb and nuclear excitation. Incoherent nucleon knock out contribution is also derived suggesting the nature of the nuclear interaction in this class of processes. We also justify the simple formulae used to fit the data of the E814 Collaboration.
We calculate the momentum dependence of three particle vertices $σγγ$, $σργ$ and $σρρ$ in the context of a Nambu Jona Lasinio type model. We show how they influence the processes $γγ\rightarrow σ\rightarrow ππ$, $ρ\rightarrow γσ$ and $γγ\rightarrow ρρ$ and how chiral symmetry shadows the presence of the $σ$.
In the present contribution we show that the introduction of a conserved axial current in electrodynamics can explain the quantization of electric charge, preserving parity conservation, and introduces a dynamical discreteness into space-time.
In the present contribution we show that the introduction of axial currents in electrodynamics can explain the quantization of electric charge and introduces a dynamical discreteness of space-time, justifying thus the regularization of Feymman's integrals.
In the present contribution we propose a gedankenexperiment in which the restriction of rational values on the velocities emerges as a necessary condition from Classical Electromagnetism and Quantum Mechanics. This restriction is shown to be intimately connected to Dirac's electric charge quantization condition.
In the present work we argue that the usual assumption that magnetic currents possess the vector structure characteristic of electric currents may be the source of several difficulties in the theory of magnetic monopoles. We propose an {\it axial} magnetic current instead and show that such difficulties are solved. Charge quantization is shown to be intimately connected with results of theories of discrete space time.
We present a possible solution for the long standing problem of the incompatibility of Dirac's charge quantization condition with integer values for the angular momentum of the electromagnetic field.