Rate-equation approach to atomic-laser light statistics

We consider three- and four-level atomic lasers that are either incoherently (unidirectionally) or coherently (bidirectionally) pumped, the single-mode cavity being resonant with the laser transition. The intra-cavity Fano factor and the photo-current spectral density are evaluated on the basis of rate equations. According to that approach, fluctuations are caused by jumps in active and detecting atoms. The algebra is considerably simpler than the one required by Quantum-Optics treatments. Whenever a comparison can be made, the expressions obtained coincide. The conditions under which the output light exhibits sub-Poissonian statistics are considered in detail. Analytical results, based on linearization, are verified by comparison with Monte Carlo simulations. An essentially exhaustive investigation of sub-Poissonian light generation by three- and four-level atoms lasers has been performed. Only special forms were reported earlier.Comment: 9 pages, 7 figures, RevTeX

A rate equation approach to cavity mediated laser cooling

The cooling rate for cavity mediated laser cooling scales as the Lamb-Dicke parameter eta squared. A proper analysis of the cooling process hence needs to take terms up to eta^2 in the system dynamics into account. In this paper, we present such an analysis for a standard scenario of cavity mediated laser cooling with eta << 1. Our results confirm that there are many similarities between ordinary and cavity mediated laser cooling. However, for a weakly confined particle inside a strongly coupled cavity, which is the most interesting case for the cooling of molecules, numerical results indicate that even more detailed calculations are needed to model the cooling process accurately.Comment: 15 pages, 10 figures, minor corrections, PRA (in press

Baryonic loading and e^+e^- rate equation in GRB sources

The expansion of the electron-positron plasma in the GRB phenomenon is compared and contrasted in the treatments of Meszaros, Laguna and Rees, of Shemi, Piran and Narayan, and of Ruffini et al. The role of the correct numerical integration of the hydrodynamical equations, as well as of the rate equation for the electron-positron plasma loaded with a baryonic mass, are outlined and confronted for crucial differences.Comment: 5 pages, 3 figures, to appear in the proceedings of "Relativistic Astrophysics and Cosmology - Einstein's Legacy" meeting, November 7-11, 2005, Munich, Germany, edited by B. Aschenbach, V. Burwitz, G. Hasinger, and B. Leibundgu

A relativistic dissipative hydrodynamic description for systems including particle number changing processes

Relativistic dissipative hydrodynamic equations are extended by taking into account particle number changing processes in a gluon system, which expands in one dimension boost-invariantly. Chemical equilibration is treated by a rate equation for the particle number density based on Boltzmann equation and Grad's ansatz for the off-equilibrium particle phase space distribution. We find that not only the particle production, but also the temperature and the momentum spectra of the gluon system, obtained from the hydrodynamic calculations, are sensitive to the rates of particle number changing processes. Comparisons of the hydrodynamic calculations with the transport ones employing the parton cascade BAMPS show the inaccuracy of the rate equation at large shear viscosity to entropy density ratio. To improve the rate equation, the Grad's ansatz has to be modified beyond the second moments in momentum.Comment: 20 pages, 11 figure

Semi-analytical model for nonlinear light propagation in strongly interacting Rydberg gases

Rate equation models are extensively used to describe the many-body states of laser driven atomic gases. We show that the properties of the rate equation model used to describe nonlinear optical effects arising in interacting Rydberg gases can be understood by considering the excitation of individual super-atoms. From this we deduce a simple semi-analytic model that accurately describes the Rydberg density and optical susceptibility for different dimensionalities. We identify the previously reported universal dependence of the susceptibility on the Rydberg excited fraction as an intrinsic property of the rate equation model that is rooted in one-body properties. Benchmarking against exact master equation calculations, we identify regimes in which the semi-analytic model is particularly reliable. The performance of the model improves in the presence of dephasing which destroys higher order atomic coherences.Comment: 7 pages, 4 figure

q-deformed dynamics and Josephson junction

We define a generalized rate equation for an observable in quantum mechanics, that involves a parameter q and whose limit $q\to 1$ gives the standard Heisenberg equation. The generalized rate equation is used to study dynamics of current biased Josephson junction. It is observed that this toy model incorporates diffraction like effects in the critical current. Physical interpretation for q is provided which is also shown to be q-deformation parameter.Comment: LaTeX 9 pages, submitted Mod. Phys. Lett. B, e-mail: [email protected]