42 research outputs found
Particle Dynamics in Weakly Charged Extreme Kerr Throat
We study dynamics of a test charged particle moving in a weakly charged
extreme Kerr throat. Dynamical equations of the particle motion are solved in
quadratures. We show explicitly that the Killing tensor of the Kerr spacetime
becomes reducible in the extreme Kerr throat geometry. Special types of motion
of particles and light are discussed.Comment: The paper is prepared for the fest volume devoted to 75th Birthday of
Mario Castagnin
Interior of a Charged Distorted Black Hole
We study interior of a charged, non-rotating distorted black hole. We
consider static and axisymmetric black holes, and focus on a special case when
an electrically charged distorted solution is obtained by the Harrison-Ernst
transformation from an uncharged one. We demonstrate that the Cauchy horizon of
such black hole remains regular, provided the distortion is regular at the
event horizon. The shape and the inner geometry of both the outer and inner
(Cauchy) horizons are studied. We demonstrate that there exists a duality
between the properties of the horizons. Proper time of a free fall of a test
particle moving in the interior of the distorted black hole along the symmetry
axis is calculated. We also study the property of the curvature in the inner
domain between the horizons. Simple relations between the 4D curvature
invariants and the Gaussian curvature of the outer and inner horizon surfaces
are found.Comment: 14 pages, 11 figures. References added, typos corrected. Some minor
changes in the tex
Distorted 5-dimensional vacuum black hole
In this paper we study how the distortion generated by a static and neutral
distribution of external matter affects a 5-dimensional
Schwarzschild-Tangherlini black hole. A solution representing a particular
class of such distorted black holes admits an RxU(1)xU(1) isometry group. We
show that there exists a certain duality transformation between the black hole
horizon and a stretched singularity surfaces. The space-time near the distorted
black hole singularity has the same topology and Kasner exponents as those of a
5-dimensional Schwarzschild-Tangherlini black hole. We calculate the maximal
proper time of free fall of a test particle from the distorted black hole
horizon to its singularity and find that, depending on the distortion, it can
be less, equal to, or greater than that of a Schwarzschild-Tangherlini black
hole of the same horizon area. This implies that due to the distortion, the
singularity of a Schwarzschild-Tangherlini black hole can come close to its
horizon. A relation between the Kretschmann scalar calculated on the horizon of
a 5-dimensional static, asymmetric, distorted black hole and the trace of the
square of the Ricci tensor of the horizon surface is derived.Comment: 20 pages, 9 figure
Amplicon metagenomics of dung beetles (Coleoptera, Scarabaeidae, Scarabaeinae) as a proxy for lemur (Primates, Lemuroidea) studies in Madagascar
Dung beetles (Scarabaeidae, Scarabaeinae) are among the most cost-effective and informative biodiversity indicator groups, conveying rich information about the status of habitats and faunas of an area. Yet their use for monitoring the mammal species, that are the main providers of the food for the dung beetles, has only recently been recognized. In the present work, we studied the diet of four endemic Madagascan dung beetles (Helictopleurus fissicollis (Fairmaire), H. giganteus (Harold), Nanos agaboides (Boucomont), and Epilissus splendidus Fairmaire) using high-throughput sequencing and amplicon metagenomics. For all beetle species, the ⅔–¾ of reads belonged to humans, suggesting that human feces are the main source of food for the beetles in the examined areas. The second most abundant were the reads of the cattle (Bos taurus Linnaeus). We also found lower but significant number of reads of six lemur species belonging to three genera. Our sampling localities agree well with the known ranges of these lemur species. The amplicon metagenomics method proved a promising tool for the lemur inventories in Madagascar
Spinoptics in a stationary spacetime
The main goal of the present paper is to study how polarization of photons
affects their motion in a gravitational field created by a rotating massive
compact object. We study propagation of the circularly polarized beams of light
in a stationary gravitational field. We use (3+1)-form of the Maxwell equations
to derive a master equation for the propagation of monochromatic
electromagnetic waves of the frequency with a given helicity. We first
analize its solutions in the high frequency approximation using the `standard'
geometrical optics approach. After that we demonstrate how this `standard'
approach can be modified in order to include the effect of the helicity of
photons on their motion. Such an improved method reproduces the standard
results of the geometrical optics at short distances. However, it modifies the
asymptotic behavior of the circularly polarized beams in the late-time regime.
We demonstrate that the corresponding equations for the circularly polarized
beam can be effectively obtained by modification of the background geometry by
including a small factor proportional to whose sign corresponds
to photon helicity. We obtain the modified equations for circularly polarized
rays by using such a `renormalization' procedure, and calculate the
corresponding renormalization term for the Kerr geometry.Comment: Added references, 13 page
Collins and Sivers asymmetries in muonproduction of pions and kaons off transversely polarised protons
Measurements of the Collins and Sivers asymmetries for charged pions and charged and neutral kaons produced in semi-inclusive deep-inelastic scattering of high energy muons off transversely polarised protons are presented. The results were obtained using all the available COMPASS proton data, which were taken in the years 2007 and 2010. The Collins asymmetries exhibit in the valence region a non-zero signal for pions and there are hints of non-zero signal also for kaons. The Sivers asymmetries are found to be positive for positive pions and kaons and compatible with zero otherwise. © 2015
Accurate Calculation of Solvation Free Energies in Supercritical Fluids by Fully Atomistic Simulations: Probing the Theory of Solutions in Energy Representation
Accurate
calculation of solvation free energies (SFEs) is a fundamental
problem of theoretical chemistry. In this work we perform a careful
validation of the theory of solutions in energy representation (ER
method) developed by Matubayasi et al. [<i>J. Chem. Phys.</i> <b>2000</b>, <i>113</i>, 6070–6081] for SFE
calculations in supercritical solvents. This method can be seen as
a bridge between the molecular simulations and the classical (not
quantum) density functional theory (DFT) formulated in energy representation.
We performed extensive calculations of SFEs of organic molecules of
different chemical natures in pure supercritical CO<sub>2</sub> (sc-CO<sub>2</sub>) and in sc-CO<sub>2</sub> with addition of 6 mol % of ethanol,
acetone, and <i>n</i>-hexane as cosolvents. We show that
the ER method reproduces SFE data calculated by a method free of <i>theoretical</i> approximations (the Bennett’s acceptance
ratio) with the mean absolute error of only 0.05 kcal/mol. However,
the ER method requires by an order less computational resources. Also,
we show that the quality of ER calculations should be carefully monitored
since the lack of sampling can result into a considerable bias in
predictions. The present calculations reproduce the trends in the
cosolvent-induced solubility enhancement factors observed in experimental
data. Thus, we think that molecular simulations coupled with the ER
method can be used for quick calculations of the effect of variation
of temperature, pressure, and cosolvent concentration on SFE and hence
solubility of bioactive compounds in supercritical fluids. This should
dramatically reduce the burden of experimental work on optimizing
solvency of supercritical solvents