916 research outputs found
Transition scattering in stochastically inhomogeneous media
When a physical object (âa sourceâ) without its own eigenfrequency moves through an acoustically homogeneous medium, the only possible form of acoustic radiation is the emission of Mach shock waves, which appear when the source velocity surpasses sonic speed. In nonhomogeneous media, in nonstationary media, or in the neighborhood of such media, the source motion is accompanied by the so-called âtransitionâ radiation (diffraction or scattering), which has place even when the source moves with subsonic velocity. Key features pertaining to the formation of the acoustical transition scattering in media with fluctuating acoustical parameters are established. To analytically study the effect, the Green's function method formulated in terms of functional derivatives is used. The relationship between the wave number and frequency, k=k(Ï), for acoustic waves is found. The results serve to determine the phasing conditions necessary for opening the transition scattering and Cherenkov radiation channel and to establish the physical explanation for the phenomenonâscattering (transformation) on inhomogeneities of the accompanied source field; i.e., formation of radiation appears when the attached field readjusts back to the equilibrium state after being deformed while passing through the fluctuations of the medium
Hypothesis about Enrichment of Solar System
Despite significant progress in the understanding of galactic nucleosynthesis
and its influence on the solar system neighborhood, challenges remain in the
understanding of enrichment of the solar system itself. Based on the detailed
review of multi-disciplinary literature, we propose a scenario that an event of
nucleogenesis -- not nucleosynthesis (from lower nucleon numbers A to higher A)
but nuclear-fission (from higher A to lower A) -- occurred in the inner part of
the solar system at one of the stages of its evolution. We propose a feasible
mechanism of implementation of such event. The occurrence of such event could
help explain the puzzles in yet-unresolved isotopic abundances, certain
meteoritic anomalies, as well as peculiarities in the solar system's
composition and planetary structure. We also discuss experimental data and
available results from existing models (in several relevant sub-fields) that
provide support and/or appear consistent with the hypothesis.Comment: 73 pages, 31 figures. arXiv admin note: text overlap with
arXiv:1610.07202, arXiv:1109.3432, arXiv:1302.6530 by other author
Tsunami generation by ocean floor rupture front propagation: Hamiltonian description
The Hamiltonian method is applied to the problem of tsunami generation caused by a propagating rupture front and deformation of the ocean floor. The method establishes an alternative framework for analyzing the tsunami generation process and produces analytical expressions for the power and directivity of tsunami radiation (in the far-field) for two illustrative cases, with constant and gradually varying speeds of rupture front propagation
Hot super-dense compact object with particular EoS
We show the possibility of existence of a self-gravitating spherically-symmetric equilibrium configuration for a neutral matter with neutron-like density, small mass MâȘMâ, and small radius RâȘRâ. We incorporate the effects of both the special and general theories of relativity. Such object may be formed in a cosmic cataclysm, perhaps an exotic one. Since the base equations of hydrostatic equilibrium are completed by the equation of state (EoS) for the matter of the object, we offer a novel, interpolating experimental data from high-energy physics, EoS which permits the existence of such compact system of finite radius. This EoS model possesses a critical state characterized by density Ï_c and temperature T_c. For such an object, we derive a radial distribution for the super-dense matter in âliquidâ phase using TolmanâOppenheimerâVolkoff equations for hydrostatic equilibrium. We demonstrate that a stable configuration is indeed possible (only) for temperatures smaller than the critical one. We derive the mass-radius relation (adjusted for relativistic corrections) for such small (MâȘMâMâȘMâ) super-dense compact objects. The results are within the constraints established by both heavy-ion collision experiments and theoretical studies of neutron-rich matter
Accretion-caused deceleration of a gravitationally powerful compact stellar object moving within a dense Fermi gas
We consider accretion-caused deceleration of a gravitationally-powerful compact stellar object traveling within a cold Fermi-gas medium. We provide analytical and numerical estimates of the effect manifestation
Dust in Interstellar Clouds, Evolved Stars and Supernovae
Outflows of pre-main-sequence stars drive shocks into molecular material
within 0.01 - 1 pc of the young stars. The shock-heated gas emits infrared,
millimeter and submillimeter lines of many species including. Dust grains are
important charge carriers and play a large role in coupling the magnetic field
and flow of neutral gas. Some effects of the dust on the dynamics of oblique
shocks began to emerge in the 1990s. However, detailed models of these shocks
are required for the calculation of the grain sputtering contribution to gas
phase abundances of species producing observed emissions. We are developing
such models. Some of the molecular species introduced into the gas phase by
sputtering in shocks or by thermally driven desorption in hot cores form on
grain surfaces. Recently laboratory studies have begun to contribute to the
understanding of surface reactions and thermally driven desorption important
for the chemistry of star forming clouds. Dusty plasmas are prevalent in many
evolved stars just as well as in star forming regions. Radiation pressure on
dust plays a significant role in mass loss from some post-main-sequence stars.
The mechanisms leading to the formation of carbonaceous dust in the stellar
outflows are similar to those important for soot formation in flames. However,
nucleation in oxygen-rich outflows is less well understood and remains a
challenging research area. Dust is observed in supernova ejecta that have not
passed through the reverse shocks that develop in the interaction of ejecta
with ambient media. Dust is detected in high redshift galaxies that are
sufficiently young that the only stars that could have produced the dust were
so massive that they became supernovae. Consequently, the issue of the survival
of dust in strong supernova shocks is of considerable interest.Comment: 4 pages, to be published in the proceedings of Fifth International
Conference on Physics of Dusty Plasma
Accretion-caused deceleration of a gravitationally powerful compact stellar object moving within a dense Fermi gas
We consider accretion-caused deceleration of a gravitationally-powerful compact stellar object traveling within a cold Fermi-gas medium. We provide analytical and numerical estimates of the effect manifestation
Hot super-dense compact object with particular EoS
We show the possibility of existence of a self-gravitating spherically-symmetric equilibrium configuration for a neutral matter with neutron-like density, small mass MâȘMâ, and small radius RâȘRâ. We incorporate the effects of both the special and general theories of relativity. Such object may be formed in a cosmic cataclysm, perhaps an exotic one. Since the base equations of hydrostatic equilibrium are completed by the equation of state (EoS) for the matter of the object, we offer a novel, interpolating experimental data from high-energy physics, EoS which permits the existence of such compact system of finite radius. This EoS model possesses a critical state characterized by density Ï_c and temperature T_c. For such an object, we derive a radial distribution for the super-dense matter in âliquidâ phase using TolmanâOppenheimerâVolkoff equations for hydrostatic equilibrium. We demonstrate that a stable configuration is indeed possible (only) for temperatures smaller than the critical one. We derive the mass-radius relation (adjusted for relativistic corrections) for such small (MâȘMâMâȘMâ) super-dense compact objects. The results are within the constraints established by both heavy-ion collision experiments and theoretical studies of neutron-rich matter
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