Experimental search for gamma-ray bursts from evaporating primordial black holes

The energy spectra and temporal characteristics of high-energy gamma-ray bursts from evaporating primordial black holes have been calculated using various evaporation models. The currently existing theoretical uncertainties in the shape of the evaporated photon spectrum are discussed. The data from the Andyrchy and Carpet-2 arrays of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) obtained in the mode of detection of a single cosmic-ray component are used to search for cosmic gamma-ray bursts with a primary photon energy of about 8 GeV. New upper limits have been obtained for the number density of evaporating black holes in a local region of space with a characteristic size of ～10^?3 pc for various evaporation models.     

Discreteness criteria forRP groups

Recently Gehring, Gilman, and Martin introduced an important class of two-generator groups with real parameters: whereβ=tr² f−4,β′=tr² g−4, and γ=tr(fgf ⁻¹ g ⁻¹)−2. The groups that belong to this class we callRP groups. We find criteria for discreteness ofRP groups generated by a hyperbolic element and an elliptic one of even order with intersecting axes. The research was partially supported by the Russian Foundation for Basic Research (Grant 99-01-00630).     

Vibronic-spin-orbit coupling in 1,3,6,8-tetrachlorodibenzo-p-dioxin

The squared dipole moments (P _0R )² of vibronic transitions caused by vibronic-spin-orbit coupling along the coordinates of out-of-plane vibration modes R were calculated for the triplet ππ* electronic states (with u and g types of orbital symmetry) in a 1,3,6,8-tetrachlorodibenzo-p-dioxin (αβTCDD) molecule. Special features of distribution (P _0R )² over R related to transitions from various sublevels of triplet states are ascertained. The obtained data made it possible to infer that the observed fine-structure phosphorescence spectrum of an αβTCDD solid solution corresponded to the ³ A _g →S ₀ and to eliminate a certain ambiguity in interpreting the vibronic structure of this spectrum.     

Resonant enhancement of dielectronic recombination by a microwave field

We have observed dielectronic recombination of Ba+ and e(-) from a continuum of finite bandwidth in the presence of microwave fields of frequencies 8.08 and 12.05 GHz and amplitudes of up to 2 V/cm. There are sharp resonant enhancements when the microwave frequency matches the Deltan = 1, 2, and 3 resonances of the intermediate autoionizing Rydberg states, and we attribute the enhancements to resonant microwave Stark l mixing. The microwave field provides a simple and powerful way to enhance the recombination rate for incident electrons of a specific energy.     

Conditional methods for continuum reacting flows in porous media

A special version of conditional moment closure—PCMC—is suggested for modeling reacting flows in porous media. The model involves conditioning on a special tracer scalar, which is introduced to characterize scalar transport in the gaseous phase. (i.e., for the flow in the interparticle space or in the pores). The model accounts for interparticle variations of species concentrations and emulates diffusion in the interparticle space. Special boundary conditions that are consistent with conventional conditions at the phase interface are obtained for the PCMC model. The model is tested against complete direct simulation of a reacting flow in porous media with favourable results.