83 research outputs found
Analytic solutions of the geodesic equation in axially symmetric space-times
The complete sets of analytic solutions of the geodesic equation in
Taub--NUT--(anti-)de Sitter, Kerr--(anti-)de Sitter and also in general
Plebanski--Demianski space--times without acceleration are presented. The
solutions are given in terms of the Kleinian sigma functions.Comment: 4 pages, 4 figures, accepted for publication in EP
Endonuclease domain of the Drosophila melanogaster R2 non-LTR retrotransposon and related retroelements: a new model for transposition
The molecular mechanisms of the transposition of non-long terminal repeat (non-LTR) retrotransposons are not well understood; the key questions of how the 3′-ends of cDNA copies integrate and how site-specific integration occurs remain unresolved. Integration depends on properties of the endonuclease (EN) domain of retrotransposons. Using the EN domain of the Drosophila R2 retrotransposon as a model for other, closely related non-LTR retrotransposons, we investigated the EN domain and found that it resembles archaeal Holliday-junction resolvases. We suggest that these non-LTR retrotransposons are co-transcribed with the host transcript. Combined with the proposed resolvase activity of the EN domain, this model yields a novel mechanism for site-specific retrotransposition within this class of retrotransposons, with resolution proceeding via a Holliday junction intermediate
General Relativistic Effect of Gravitomagnetic Charge on Pulsar Magnetosphere and Particle Acceleration in a Polar Cap
We study magnetospheric structure surrounding rotating magnetized neutron
star with nonvanishing NUT (Newman-Tamburino-Unti) parameter. For the
simplicity of calculations Goldreich-Julian charge density is analyzed for the
aligned neutron star with zero inclination between magnetic field,
gravitomagnetic field and rotation axis. From the system of Maxwell equations
in spacetime of slowly rotating NUT star, second-order differential equation
for electrostatic potential is derived. Analytical solution of this equation
indicates the general relativistic modification of an accelerating electric
field and charge density along the open field lines by the gravitomagnetic
charge. The implication of this effect to the magnetospheric energy loss
problem is underlined. In the second part of the paper we derive the equations
of motion of test particles in magnetosphere of slowly rotating NUT star. Then
we analyze particle motion in the polar cap and show that NUT parameter can
significantly change conditions for particle acceleration.Comment: 21 pages, 6 figures, accepted for publication in Ap
Geodesics of electrically and magnetically charged test particles in the Reissner-Nordstr\"om space-time: analytical solutions
We present the full set of analytical solutions of the geodesic equations of
charged test particles in the Reissner-Nordstr\"om space-time in terms of the
Weierstra{\ss} , and elliptic functions. Based on the
study of the polynomials in the and equations we characterize
the motion of test particles and discuss their properties. The motion of
charged test particles in the Reissner-Nordstr\"om space-time is compared with
the motion of neutral test particles in the field of a gravitomagnetic
monopole. Electrically or magnetically charged particles in the
Reissner-Nordstr\"om space-time with magnetic or electric charges,
respectively, move on cones similar to neutral test particles in the Taub-NUT
space-times
Analytical solution of the geodesic equation in Kerr-(anti) de Sitter space-times
The complete analytical solutions of the geodesic equations in Kerr-de Sitter
and Kerr-anti-de Sitter space-times are presented. They are expressed in terms
of Weierstrass elliptic p, zeta, and sigma functions as well as hyperelliptic
Kleinian sigma functions restricted to the one-dimensional theta-divisor. We
analyze the dependency of timelike geodesics on the parameters of the
space-time metric and the test-particle and compare the results with the
situation in Kerr space-time with vanishing cosmological constant. Furthermore,
we systematically can find all last stable spherical and circular orbits and
derive the expressions of the deflection angle of flyby orbits, the orbital
frequencies of bound orbits, the periastron shift, and the Lense-Thirring
effect.Comment: 18 pages, 11 figure
Crohn disease: before and after 1932 year
The article describes the historical milestones in the study of Crohn's disease from the time of its original description in the 17th century, the revolution in the medical community after the landmark paper in 1932, to the present day. The history of Crohn's disease testifies to the discoveries of the past years, which open up to us the advantages of a scientific approach to the diagnosis and treatment of this disease
The Real Scalar Field Equation for Nariai Black Hole in the 5D Schwarzschild-de Sitter Black String Space
The Nariai black hole, whose two horizons are lying close to each other, is
an extreme and important case in the research of black hole. In this paper we
study the evolution of a massless scalar field scattered around in 5D
Schwarzschild-de Sitter black string space. Using the method shown by Brevik
and Simonsen (2001) we solve the scalar field equation as a boundary value
problem, where real boundary condition is employed. Then with convenient
replacement of the 5D continuous potential by square barrier, the reflection
and transmission coefficients () are obtained. At last, we also compare
the coefficients with usual 4D counterpart.Comment: 10 pages,6 figures.To appear in Int. J. Mod. Phys.
External Electromagnetic Fields of a Slowly Rotating Magnetized Star with Gravitomagnetic Charge
We study Maxwell equations in the external background spacetime of a slowly
rotating magnetized NUT star and find analytical solutions for the exterior
electric fields after separating the equations of electric field into angular
and radial parts in the lowest order approximation. The star is considered
isolated and in vacuum, with dipolar magnetic field aligned with the axis of
rotation. The contribution to the external electric field of star from the NUT
charge is considered in detail.Comment: 6 pages, 2 figures, accepted for publication in Astrophysics and
Space Scienc
Geodesic equations and algebro-geometric methods
For an investigation of the physical properties of gravitational fields the
observation of massive test particles and light is very useful. The
characteristic features of a given space-time may be decoded by studying the
complete set of all possible geodesic motions. Such a thorough analysis can be
accomplished most effectively by using analytical methods to solve the geodesic
equation. In this contribution, the use of elliptic functions and their
generalizations for solving the geodesic equation in a wide range of well known
space-times, which are part of the general Pleba\'nski-Demia\'nski family of
solutions, will be presented. In addition, the definition and calculation of
observable effects like the perihelion shift will be presented and further
applications of the presented methods will be outlined.Comment: 8 pages, no figures; based on presentation at the conference
"Relativity and Gravitation: 100 Years after Einstein in Prague," Prague,
2012. Relativity and Gravitation, volume 157 of Springer Proceedings in
Physics, p 91. Springer International Publishing, 201
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