Dark matter as a cancer hazard

We comment on the paper "Dark Matter collisions with the Human Body" by K. Freese and C. Savage (Phys. Lett. B 717, 25 (2012) [arXiv:1204.1339]) and describe a dark matter model for which the results of the previous paper do not quite apply. Within this mirror dark matter model, potentially hazardous objects, mirror micrometeorites, can exist and may lead to diseases triggered by multiple mutations, such as cancer, though with very low probability.Comment: 7 pages, revtex4, some text and references added, version to be published in Physics Letters

Promising Versions of alpha-Martensite Rod-Like Crystal Initiation in Iron Alloys by Three Elastic Wave Sources

Versions are provided for alpha-martensite rod-shaped crystal initiation by three orthogonal longitudinal elastic waves propagating in orthogonal directions of the types aOE (c) 001 >(gamma) and aOE (c) 110 >(gamma) in Fe - 31% Ni single crystals. The probability is considered of direct initiation by Bain-type deformation waves. It is demonstrated within the scope of dynamic theory that the anticipated orientation of rod-like crystals is close to aOE (c) 111 >(gamma) or to aOE (c) 905 >(gamma). Possible features of martensite crystal tetragonality are discussed. Ultrasound source power required for initiating martensitic transformation is determined.Work was carried out with financial support of the RFFI (project number 14-08-00734)

Breaking the light speed barrier

As it is well known, classical special relativity allows the existence of three different kinds of particles: bradyons, luxons and tachyons. Bradyons have non-zero mass and hence always travel slower than light. Luxons are particles with zero mass, like the photon, and they always travel with invariant velocity. Tachyons are hypothetical superluminal particles that always move faster than light. The existence of bradyons and luxons is firmly established, while the tachyons were never reliably observed. In quantum field theory, the appearance of tachyonic degrees of freedom indicates vacuum instability rather than a real existence of the faster-than-light particles. However, recent controversial claims of the OPERA experiment about superluminal neutrinos triggered a renewed interest in superluminal particles. Driven by a striking analogy of the old Frenkel-Kontorova model of a dislocation dynamics to the theory of relativity, we conjecture in this note a remarkable possibility of existence of the fourth type of particles, elvisebrions, which can be superluminal. The characteristic feature of elvisebrions, distinguishing them from tachyons, is that they are outside the realm of special relativity and their energy remains finite (or may even turn to zero) when the elvisebrion velocity approaches the light velocity.Comment: 37 pages, no figures, two last sections extended, to be published in Acta Physica Polonica

Expanding space, quasars and St. Augustine's fireworks

An attempt is made to explain time non-dilation allegedly observed in quasar light curves. The explanation is based on the assumption that quasar black holes are, in some sense, foreign for our Friedmann-Robertson-Walker universe and do not participate in the Hubble flow. Although at first sight such a weird explanation requires unreasonably fine-tuned Big Bang initial conditions, we find a natural justification for it using the Milne cosmological model as an inspiration.Comment: 36 pages, 4 figures, some text and references added, published versio

Degenerate Structure of Transformation Twins and Estimation of Dislocation Density in Martensite Crystals

In the dynamic theory of martensitic transformations, the wave mechanism of controlling martensite crystal growth is determined by the superposition of wave beams of quasi-longitudinal (or longitudinal) waves carrying the "tensile-compression" deformation in the orthogonal directions. The wave beam formation is considered to be a result of the formation of excited (vibrational) states. The existence of transformation twins is interpreted as a result of a matched propagation with respect to long-wave (l waves) and short-wave (s waves) shifts. The matching condition is analyzed for the gamma-alpha martensitic transformation in iron-base alloys. It is shown for the first time that the transition to a degenerate twin structure with the allowance for the medium discreteness enables one to estimate the dislocation density in crystals with habit {557}, which agrees with that observed experimentally

The dog-and-rabbit chase problem as an exercise in introductory kinematics

The purpose of this article is to present a simple solution of the classic dog-and-rabbit chase problem which emphasizes the use of concepts of elementary kinematics and, therefore, can be used in introductory mechanics course. The article is based on the teaching experience of introductory mechanics course at Novosibirsk State University for first year physics students which are just beginning to use advanced mathematical methods in physics problems. We hope it will be also useful for students and teachers at other universities too.Comment: 11 pages, 3 figures, authorship changed to match the published versio