75 research outputs found
Expansion-Free Evolving Spheres Must Have Inhomogeneous Energy Density Distributions
In a recent paper a systematic study on shearing expansion-free spherically
symmetric distributions was presented. As a particular case of such systems,
the Skripkin model was mentioned, which corresponds to a nondissipative perfect
fluid with a constant energy density. Here we show that such a model is
inconsistent with junction conditions. It is shown that in general for any
nondissipative fluid distribution, the expansion-free condition requires the
energy density to be inhomogeneous. As an example we consider the case of dust,
which allows for a complete integration.Comment: 8 pages, Latex. To appear in Phys. Rev.D. Typos correcte
Expansion-Free Cavity Evolution: Some exact Analytical Models
We consider spherically symmetric distributions of anisotropic fluids with a
central vacuum cavity, evolving under the condition of vanishing expansion
scalar. Some analytical solutions are found satisfying Darmois junction
conditions on both delimiting boundary surfaces, while some others require the
presence of thin shells on either (or both) boundary surfaces. The solutions
here obtained model the evolution of the vacuum cavity and the surrounding
fluid distribution, emerging after a central explosion. This study complements
a previously published work where modeling of the evolution of such kind of
systems was achieved through a different kinematical condition.Comment: 9 pages, Revtex. Typos corrected. Published in Int. J. Mod. Phys.
Some problems in the study of the chronology of the ancient nomadic cultures in Eurasia (9th - 3rd centuries BC)
This research is focused on the chronological investigations of ancient nomads belonging to the Scythian cultures which occupied the steppe and forest-steppe zones of Eurasia during the 9th-3rd centuries BC. The 14C dates for the pre-scythian and early scythian time in both Europe and Asia are presented and compared to their chronological position based on archaeological evidence. The first 14C dates have been produced for the Scythian time monuments located in the Lower Volga River basin, Urals and Transurals regions. Their chronological positions are compared with the position of the monuments of Southern Siberia and Central Asia. It was shown that the nomadic cultures belonging to the Scythian culture began to exist over the wide territory of Eurasia from the 9th-8th centuries cal BC and there are some monuments which may be synchronous to the Arzhan royal barrow (the oldest monument known). A list of new 14C dates and a map of the monuments are presented
A chronology of the Scythian antiquities of Eurasia based on new archaeological and C-14 data
The paper is compares the chronology of the monuments of the Scythian epoch located in the east and west of the Eurasian steppe zone on the basis of both archaeological and radiocarbon data. The lists of C-14 dates for the monuments located in different parts of Eurasia are presented according to the periods of their existence. Generally, the C-14 dates are confirmed the archaeological point of view and allow us to compare the chronological position of the European and Asian Scythian monuments on the united C-14 time scale
Review of experimental results from SND detector
The review of experimental results obtained with SND detector at VEPP-2M
collider in the energy region -- 1.38 GeV is given.
The presented results include the following items: studies of the light vector
mesons radiative decays, OZI-rule and G-parity suppressed -meson rare
decays, -meson parameters measurements, studies of
process dynamics, and mesons rare
decays, and mesons conversion decays, and study of the
annihilation into hadrons.Comment: 12 pages and 6 figures. Talk given at the IX International Conference
on Hadron Spectroskopy, Protvino, Russia, August 25 - September 1, 200
Cavity evolution in relativistic self-gravitating fluids
We consider the evolution of cavities within spherically symmetric
relativistic fluids, under the assumption that proper radial distance between
neighboring fluid elements remains constant during their evolution (purely
areal evolution condition). The general formalism is deployed and solutions are
presented. Some of them satisfy Darmois conditions whereas others present
shells and must satisfy Israel conditions, on either one or both boundary
surfaces. Prospective applications of these results to some astrophysical
scenarios is suggested.Comment: 10 pages Revtex. To appear in Class. Quantum Grav
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