Zel'dovich states with very small mass and charge in nonlinear electrodynamics coupled to gravity

It is shown that in non-linear electrodynamics (in particular, Born-Infeld one) in the framework of general relativity there exist "weakly singular" configurations such that (i) the proper mass M is finite in spite of divergences of the energy density, (ii) the electric charge q and Schwarzschild mass m ~ q can be made as small as one likes, (iv) all field and energy distributions are concentrated in the core region. This region has an almost zero surface area but a finite longitudinal size L=2M. Such configurations can be viewed as a new version of a classical analogue of an elementary particle.Comment: 11 pages. 1 reference added. To appear in Grav. Cosm

Bunch-excited wakefield in dielectric waveguide with hollow plasma channel

Wakefield excitation by a single relativistic electron bunch in a plasma-dielectric accelerating structure has been studied both analytically and numerically. The structure represents a dielectric-loaded cylindrical metal waveguide, which has partially plasma-filled channel (the hollow plasma channel) to transport charged particles. Assuming the linear regime of excitation, analytical expressions have been derived for the longitudinal and radial wakefields generated by a finite-size electron bunch. Axial profiles of wakefield component amplitudes have been studied, and their mode and spectrum analyses have been performed. Furthermore, the electron bunch-driven wakefield excitation has been PIC-simulated numerically for the quasi-linear regime. The comparative analysis of the data resulting from analytical studies and the ones obtained by numerical simulation has demonstrated qualitative agreement between the results

Parity violating cylindrical shell in the framework of QED

We present calculations of Casimir energy (CE) in a system of quantized electromagnetic (EM) field interacting with an infinite circular cylindrical shell (which we call `the defect'). Interaction is described in the only QFT-consistent way by Chern-Simon action concentrated on the defect, with a single coupling constant $a$. For regularization of UV divergencies of the theory we use % physically motivated Pauli-Villars regularization of the free EM action. The divergencies are extracted as a polynomial in regularization mass $M$, and they renormalize classical part of the surface action. We reveal the dependence of CE on the coupling constant $a$. Corresponding Casimir force is attractive for all values of $a$. For $a\to\infty$ we reproduce the known results for CE for perfectly conducting cylindrical shell first obtained by DeRaad and Milton.Comment: Typos corrected. Some references adde

The banding in serpentinites and its influence on character of talc-magnesite and magnesite mineralization (natural and experimental data)

The geological setting of some banded talc-magnesite ores and magnesites was studied in the field (Urals, Russia; Finland, East Iran). Talc-magnesite and magnesite ores occur in ultramafic rocks. Experimental methods were used in order to determine the influence of physico-mechanical parameters on the formation of banded structures in talc-magnesite rocks and magnesites. Experiments were carried out with axial compression up to 10 kbar and confining pressure 2, 4, 6 and 8 kbars at room temperature. The samples were chemically analyzed using a Philips Analytical PW 2400 authomatic XRF Spectrometer and a scanning electron microscope (SEM). Some analyses were made with a "Camebax SX-50" electron microprobe, using an accelerating voltage of 20 kilovolts for all elements with a sample current of 20 nanoamps. X-ray method for phase identification was used. Structure peculiarities of rocks prior to the experiment and after were studied by optical methods in polished sections and thin sections. It was shown, that banding in talc-magnesite stone and magnesites are inherited from banded serpentinites and can affect on distribution and composition rock-forming minerals

The behaviours of Mg and Ca in some types of ultramaphic alkaline melts in the presence of H 2 O at high temperature and pressure (the experimental data)

The sample has been investigated, which was composed of olivine-melilite rock from the south-western part of the Kugda intrusion, situated in the eastern margin of the Maimecha-Kotuiskay alkaline- ultramaphic province (northern part of Siberia platform). The experiments were carried out using a high-pressure apparatus of the "piston-cylinder" type. The pressure was 5-15 kb and the temperature -800-1250 0 C. The water content in the system was 3 and 9 wt. All experiments were carried out in hermetically sealed Pt or Au ampoules. The samples were chemically analyzed using a scanning electron microscope (SEM). Besides, the chemical composition of the experimental phases was determined by means of more than 40 electron microprobe in 20 experimental samples. For phase identification the X-ray method was used too. The structural peculiarities of rocks and mineral compositions were studied by optical methods in polished and thin sections prior and after the experiment. It was shown that at pressures above 7.5-8 kb the olivine-melilite melt is separated into two melts: pyroxenite and melilite. Most part of Mg in this system was concentrated in a high temperature phase of diopside type. The remaining melt was depleted of Mg and enriched by Ca. The mineralization vapour practically did not contain Mg. The main components of the mineralization vapour were Ca, Na, Si and Fe

Влияние релаксационных процессов при деформировании на электрическое сопротивление полипропиленовых композитов с техническим углеродом

Objectives. To study the relationship between bending deformation and the change in the electrical resistance of carbon black polypropylene composites.Methods. Conductive polypropylene composites filled with carbon black UM-76 were investigated. The samples were deformed and kept under constant bending at temperatures of 20–155 °C.Results. The deformation of the samples led to a reversible increase in their electrical resistance, while subsequent holding of the samples in the deformed state was accompanied by an exponential drop in their electrical resistance. The average times and activation energies of the electrical relaxation of the deformed polypropylene composites were calculated (30–32 kJ/mol) and compared with similar characteristics of polyethylene composites (15–16 kJ/mol).Conclusions. The electrical resistance relaxation of deformed carbon black polypropylene composites at elevated temperatures is similar to their stress relaxation. The average times and activation energies of the electrical relaxation of deformed polypropylene composites are comparable with similar data on their mechanical relaxation. It was found that these electrical and mechanical phenomena are based on the same underlying physical processes.Цели. Работа посвящена изучению влияния деформации изгиба при повышенных температурах на изменение электрического сопротивления электропроводящих полипропиленовых композитов, наполненных техническим углеродом.Методы. Исследовались полипропиленовые композиты с техническим углеродом УМ-76. Образцы изгибались и выдерживались при заданном прогибе в интервале 20–155 °C.Результаты. При деформировании образцов наблюдался обратимый рост электрического сопротивления. Последующая выдержка образцов в деформированном состоянии сопровождалась экспоненциальным падением их электрического сопротивления. Были рассчитаны средние времена и энергия активации электрической релаксации деформированных полипропиленовых композитов (30–32 кДж/моль), а также проведено их сравнение с аналогичными характеристиками полиэтиленовых композитов (около 14–16 кДж/моль).Выводы. При механическом деформировании электропроводящих полипропиленовых композитов с техническим углеродом, в том числе при повышенных температурах, характер релаксации электрического сопротивления аналогичен характеру релаксации механического напряжения. Средние времена и энергия активации электрической релаксации деформированных полипропиленовых композитов сопоставимы с аналогичными показателями для механической релаксации. Это указывает на общий механизм этих процессов

Hadron and Quark Form Factors in the Relativistic Harmonic Oscillator Model

Nucleon, pion and quark form factors are studied within the relativistic harmonic oscillator model including the quark spin. It is shown that the nucleon charge, magnetic and axial form factors and the pion charge form factor can be explained with one oscillator parameter if one accounts for the scaling rule and the size of the constituent quarks.Comment: 9 pages, Latex, 3 postscript figures, DFTT 8/9

The Boltzmann equation for colourless plasmons in hot QCD plasma. Semiclassical approximation

Within the framework of the semiclassical approximation, we derive the Boltzmann equation describing the dynamics of colorless plasmons in a hot QCD plasma. The probability of the plasmon-plasmon scattering at the leading order in the coupling constant is obtained. This probability is gauge-independent at least in the class of the covariant and temporal gauges. It is noted that the structure of the scattering kernel possesses important qualitative difference from the corresponding one in the Abelian plasma, in spite of the fact that we focused our study on the colorless soft excitations. It is shown that four-plasmon decay is suppressed by the power of $g$ relative to the process of nonlinear scattering of plasmons by thermal particles at the soft momentum scale. It is stated that the former process becomes important in going to the ultrasoft region of the momentum scale.Comment: 41, LaTeX, minor changes, identical to published versio

Quark-antiquark composite systems: the Bethe-Salpeter equation in the spectral-integration technique

The Bethe-Salpeter equations for the light-quark composite systems, q q-bar, are written in terms of spectral integrals. For the q q-bar -mesons characterized by the mass M, spin J and radial quantum number n, the equations are presented for the following (n,M^2)-trajectories: pi_J, eta_J, a_J, f_J, rho_J, omega_J, h_J and b_J.Comment: 42 pages, 5 figures, typos correcte