Galactic anisotropy as signature of “top-down” mechanisms of ultrahigh-energy cosmic rays

We show that “top-down” mechanisms of ultrahigh-energy cosmic rays which involve heavy relic particle-like objects predict a Galactic anisotropy of the highest-energy cosmic rays at the level of minimum ∼ 20%. This anisotropy is large enough to be either observed or ruled out in the next generation of experiments. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 2, 99–103 (25 July 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Emission of supersonic soliton wave beams—generators of restructuring of nanocrystals under atom bombardment,and the self-organization of a dynamic superlattice of complexes of soliton atomic vibrations

It has been shown that the dynamic superlattice of pulsed complexes of soliton vibrations or, actually, a “soliton crystal” is self-organized in crystalline materials at high levels of thermal and dynamic excitations of atomic vibrations. The results obtained have been adapted to the alpha uranium crystal system. It has been demonstrated that the atom bombardment of crystalline materials leads to the generation of beams of nonlinear subsonic and supersonic soliton and breather waves. The breathers and solitons initiate threshold kinetic processes of defect formation, such as surface vibrations and evaporation of surface atoms, multiple reflection of bombarding atoms, and restructuring of nanocrystals. The results obtained can be used in experimental investigations of microdynamics of materials under high dynamic and temperature loads by the neutron and ion scattering methods.     

Finite‐difference approximation for the u(k)‐derivative with O(hM−k+1) accuracy: An analytical expression

An approximation of function u(x) as a Taylor series expansion about a point x₀ at M points x_i, ～ i = 1,2,…,M is used where x_i are arbitrary‐spaced. This approximation is a linear system for the derivatives u^(k) with an arbitrary accuracy. An analytical expression for the inverse matrix A ^?1 where A = [A_ik] = (x_i ? x₀)^k is found. A finite‐difference approximation of derivatives u^(k) of a given function u(x) at point x₀ is derived in terms of the values u(x_i). © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006     

Soliton microdynamics of structural phase transitions in crystalline materials and phonons of a new type on phase interfaces

It is shown that the generation of nonlinear soliton, breather, and shock waves at high dynamic excitations leads to martensitic phase transformations in crystalline materials of the α-uranium type. Investigations have been performed by modeling the atomic microdynamics with the use of the modified interaction potential. It is shown that collisions of compression shock waves and rarefaction solitons lead to the generation of nuclei of new phases, which evolve according to the domino principle. The phonon spectra of systems with phase interfaces are investigated. A new effect of the total internal phonon reflection has been discovered. It is shown that surface phonons of radically a new type (different from the Rayleigh surface waves) are excited on interfaces. The results are adapted to materials of the α-uranium type, where solitons have been found at slow-neutron scattering.     

Biphonon Spectra in Disordered Crystals

In the coherent potential approximation (CPA) calculations have been made for the light absorption coefficient and the density of states in biphonon band for a disordered isotopicmixed crystal over the whole range of mixture concentrations. Models of one-dimensional and three-dimensional crystals have been considered. It is shown that even in three-dimensional crystals such situations may arise when in the region of the fundamental tone at any concentrations no splitting of the impurity band occurs while in the overtone region due to anharmonicity such splitting takes place at any compositions of the mixture.     

Massive graviton as a testable cold-dark-matter candidate

We construct a consistent model of gravity where the tensor graviton mode is massive, while linearized equations for scalar and vector metric perturbations are not modified. The Friedmann equation acquires an extra dark-energy component leading to accelerated expansion. The mass of the graviton can be as large as approximately (10(15) cm)(-1), being constrained by the pulsar timing measurements. We argue that nonrelativistic gravitational waves can comprise the cold dark matter and may be detected by the future gravitational wave searches.     

Narrowing the window for millicharged particles by CMB anisotropy

We calculate the cosmic microwave background (CMB) anisotropy spectrum in models with millicharged particles of electric charge q～10^?6?10^?1 in units of electron charge. We find that a large region of the parameter space for the millicharged particles exists where their effect on the CMB spectrum is similar to the effect of baryons. Using WMAP data on the CMB anisotropy and assuming the Big Bang nucleosynthesis value for the baryon abundance, we find that only a small fraction of cold dark matter, Ω_mcp<0.007 (at 95% CL), may consist of millicharged particles with the parameters (charge and mass) from this region. This bound significantly narrows the allowed range of the parameters of millicharged particles. In models without paraphotons, millicharged particles are now excluded as a dark matter candidate. We also speculate that recent observation of 511-keV γ rays from the Galactic bulge may be an indication that a (small) fraction of cold dark matter is comprised of millicharged particles.     

Charged Frenkel biexcitons in organic molecular crystals

It is known that the energy of the lowest electronic transition in the neutral molecules of anthracene, tetracene, and other polyacenes is blue-shifted in comparison with the corresponding transition energy in univalent molecular ions. This effect in a molecular crystal may be responsible for the attraction between a molecular (Frenkel) exciton and a charge carrier. Due to this attraction, a bound state of Frenkel exciton and free charge (charged Frenkel exciton) may be formed [5]. As we demonstrate below, the same mechanism can be responsible for the formation of a charged biexciton (bound state of two Frenkel excitons and a charge carrier). A one-dimensional lattice model is used which corresponds to J aggregates and is also a good approximation for quasi-one-dimensional crystals. Calculations are performed for molecular crystals like tetracene, where the exciton band at low temperature is much narrower than the band of the charge carrier.     

Soliton and multiphonon microdynamics of thermal conductivity of plutonium and uranium in the temperature range of martensitic phase transitions

The microdynamics of nonlinear crystal lattice vibrations of Pu and U at temperatures of martensitic phase transitions has been studied. Using the Lenard-Jones potential, the dynamic equations are solved when the energy is transferred by solitons. The synchronism of solitons and the energy flux peaks demonstrates the staccato-effect. The temperature dependences of the thermal conductivity have maxima at the phase transitions. A spectral analysis shows that the main heat transfer is provided by rarefaction solitons. Upon the martensitic transition, the spectral density is transformed with “ignition” of the high-frequency region. The spectral density demonstrates maxima of the quasi-biphonon type.