326 research outputs found
Developments in General Relativity: Black Hole Singularity and Beyond
At the 20-th Texas Symposium on Relativistic Astrophysics there was a plenary
talk devoted to the recent developments in classical Relativity. In that talk
the problems of gravitational collapse, collisions of black holes, and of black
holes as celestial bodies were discussed. But probably the problems of the
internal structure of black holes are a real great challenge. In my talk I want
to outline the recent achievements in our understanding of the nature of the
singularity (and beyond!) inside a realistic rotating black hole. This
presentation also addresses the following questions: Can we see what happens
inside a black hole? Can a falling observer cross the singularity without being
crushed? An answer to these questions is probably "yes".Comment: 13 page
Special features in the asymptotic expression of the electromagnetic spectrum from dipole which free fall into a Schwarzschild black hole
The characteristic features were found in the electromagnetic spectrum of
radiation from free falling dipole, when it is fall radially into a
Schwarzschild black hole. These features can be used as another method for the
black hole mass determinating. Also, these features can be used for the
determination some characteristics of the magnetosphere or the accretion disk
around the black hole.Comment: 13 pages, 5 figure
Three-Dimensional Billiards with Time Machine
Self-collision of a non-relativistic classical point-like body, or particle,
in the spacetime containing closed time-like curves (time-machine spacetime) is
considered. A point-like body (particle) is an idealization of a small ideal
elastic billiard ball. The known model of a time machine is used containing a
wormhole leading to the past. If the body enters one of the mouths of the
wormhole, it emerges from another mouth in an earlier time so that both the
particle and its "incarnation" coexist during some time and may collide. Such
self-collisions are considered in the case when the size of the body is much
less than the radius of the mouth, and the latter is much less than the
distance between the mouths. Three-dimensional configurations of trajectories
with a self-collision are presented. Their dynamics is investigated in detail.
Configurations corresponding to multiple wormhole traversals are discussed. It
is shown that, for each world line describing self-collision of a particle,
dynamically equivalent configurations exist in which the particle collides not
with itself but with an identical particle having a closed trajectory (Jinnee
of Time Machine).Comment: 20 pages (LATEX), 5 figures (EPS
Why Expenses are not Charges?
The article considers problems of such economic categories, such as “expenses”, “charges” and “costs” disclosure, gives clear differentiation of these notions and proves that it is wrong to consider them synonym
Passage of radiation through wormholes
We investigate numerically the process of the passage of a radiation pulse
through a wormhole and the subsequent evolution of the wormhole that is caused
by the gravitational action of this pulse. The initial static wormhole is
modeled by the spherically symmetrical Armendariz-Picon solution with zero
mass. The radiation pulses are modeled by spherically symmetrical shells of
self-gravitating massless scalar fields. We demonstrate that the compact signal
propagates through the wormhole and investigate the dynamics of the fields in
this process for both cases: collapse of the wormhole into the black hole and
for the expanding wormhole.Comment: 18 Pages, 13 figures, minor typos corrected, updated reference
Silhouettes of wormholes traversed for radiation
The problem of the passage of light through the mouth of a zero-mass wormhole
and the possibility of observing the objects from another asymptotically flat
space-time through the mouth of a wormhole are considered. It is shown that an
individual star can have several images and the fact that the image of a flat
Lambertian screen has a complex brightness distribution for an observer located
on the opposite side of the throat. Images of two such screens visible inside
the silhouette of a massless wormhole and the distribution of radiation
intensity in their images are constructed.Comment: 11 pages, 12 figure
An application of high-dimensional statistics to predictive modeling of grade variability
The economic viability of a mining project depends on its efficient exploration, which requires a prediction of worthwhile ore in a mine deposit. In this work, we apply the so-called LASSO methodology to estimate mineral concentration within unexplored areas. Our methodology outperforms traditional techniques not only in terms of logical consistency, but potentially also in costs reduction. Our approach is illustrated by a full source code listing and a detailed discussion of the advantages and limitations of our approach. © 2020 by the authors. Licensee MDPI, Basel, Switzerland
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