Chemical physics of high dynamic pressures

Basic characteristics of dynamic impact and specific changes caused by it in condensed media, both used in practice and prospective, are discussed.     

Mach reflection parameters for plexiglas cylinders

The collapsing air gap method has been used to investigate the development and limiting parameters of the Mach reflection of a conical convergent shock in plexiglas cylinders arranged along the axis of a detonating explosive charge. The diameters of the cylindrical specimens varied from 15 to 100 mm. It is shown that on the stationary interval of development of the triple-shock configuration, where the velocity of the head wave is equal to the detonation velocity, there is a linear relationship between the diameter of the head wave, its radius of curvature, and the diameter of the cylinder.     

QCD and hybrid NBD on oscillating moments of multiplicity distributions in lepton-and hadron-initiated reactions

QCD predictions for moments of multiplicity distributions are compared with experimental data on e⁺e^? collisions and their two-NBD fits. Moments of the multiplicity distribution in a two-NBD model for 1.8-TeV pp collisions are considered. Three-NBD model predictions and fits for pp at LHC energies are also discussed. Analytic expressions for moments of hybrid NBD are derived and used to get insight into jet parameters and multicomponent structure of the processes. Interpretation of observed correlations is proposed.     

Bose condensation of interwell excitons in lateral traps: A phase diagram

The luminescence of interwell excitons in GaAs/AlGaAs double quantum wells (n-i-n heterostructures) containing large-scale random-potential fluctuations was studied. The study dealt with the properties of an exciton whose photoexcited electron and hole are spatially divided between the neighboring quantum wells under density variation and at temperatures of down to 0.5 K. We investigated domains ∼1 μm in size, which act as macroscopic exciton traps. Once the resonance laser pump power reaches a certain threshold, a very narrow delocalized exciton line appears (with a width less than 0.3 meV), which grows strongly in intensity with increasing pump power and shifts toward lower energies (by approximately 0.5 meV) in accordance with the exciton buildup in the lowest state in the domain. As the temperature increases, this spectral line disappears in a nonactivated manner. This phenomenon is assigned to Bose condensation occurring in the quasi-two-dimensional system of interwell excitons. The critical exciton density and temperature were determined within the temperature interval studied (0.5 to 3.6 K), and a phase diagram specifying the exciton condensate region was constructed. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 1, 2004, pp. 168–170. Original Russian Text Copyright ? 2004 by Dremin, Larionov, Timofeev.     

On some properties of cascade processes with random intensity

By the example of the asymptotically free theory λϕ ₆³ with random constant λ, the process of cascade multiplication of particles with random intensity of elementary decay is considered. The dependence of the characteristics of the cascade particle multiplicity distribution on the parameters of the probabilistic distribution over the elementary decay intensity is studied.     

Elastic coefficients of aluminum as functions of the degree of compression in a shock wave

The velocities of elastic relief waves in commercial aluminum (AD1) and aluminum alloy (D16) samples compressed by a shock wave were measured by the most direct method. Using these results together with the relationship for the three-dimensional velocity of sound as a function of the intensity of the sound wave (derived on the assumption that the shock adiabat and the one-dimensional release isentrope coincide when expressed in pressure/mass-velocity coordinates), Young's modulus, the shear modulus, and the Poisson coefficient are calculated for shock-compressed aluminum.     

Nonclassical Field States in Quantum Optics and Particle Physics

The primary aim of the present paper is to draw the attention of particle physicists to new developments in studying squeezed and correlated states of the electromagnetic field, and those working on the latest developments to new findings about multiplicity distributions and other specific effects in quantum chromodynamics. New types of nonclassical states used in quantum optics such as squeezed states, correlated states, and even and odd coherent states (Schrödinger cat states) for one-mode and multimode interactions are reviewed. Their distribution functions are analyzed according to the method first used for multiplicity distributions in high-energy particle interactions. The phenomenon of oscillations of particle distribution functions of squeezed fields is described and related to the phenomenon of oscillations of cumulant moments of some distributions for squeezed and correlated field states. Possible extension of the method to fields different from the electromagnetic field (gluons, pions, etc.) is conjectured, and some predictions of specific effects in nucleus-nucleus interactions at high energies are presented.     

Some problems of the jet calculus in the perturbative QCD

Some problems of the jet calculus in perturbative QCD are discussed. The first one is related to specifying the order of perturbation. Because of the cancellation of the leading-order (LO) and next-to-leading-order (NLO) terms in the ratio r of the mean multiplicities in gluon and quark jets, the results presently obtained for this ratio should be associated with the 4NLO approximation. The second problem reveals itself in calculations where corrections to some quantities (in particular, to r′ are greater at present energies than lower order terms. Some features that characterize jets and which do not suffer from this deficiency are proposed. Yet another problem lies in interpreting negative cumulant-moment values, which are considered as an indication of a changeover from attraction to repulsion in sets of specific particle content. Finally, the problem of generalizing QCD equations for generating functions is briefly discussed.     

Detonation parameters of trinitrotoluene-hexogen mixtures

Summary The polytropy index of the explosion products for trinitrotoluene-hexogen mixtures may be calculated from the known values of this index for the individual components.