78 research outputs found
Analytic treatment of geodesics in five-dimensional Myers-Perry space--times
We present the complete set of analytical solutions of the geodesic equation
in the five-dimensional Myers-Perry space-time with equal rotation parameter in
terms of the Weierstra{\ss}' elliptic and Weierstra{\ss}' zeta and sigma
functions. We study the underlying polynomials in the polar and radial
equations which depend on the parameters of the metric and conserved quantities
of a test particle and characterize the motion by their zeros. We exemplify the
efficiency of the analytical method on the orbits of test particles.Comment: 15 pages, 7 figures, to be published in PRD. Version with improved
reference
Geodesic motion in the space-time of cosmic strings interacting via magnetic fields
We study the geodesic motion of test particles in the space-time of two
Abelian-Higgs strings interacting via their magnetic fields. These bound states
of cosmic strings constitute a field theoretical realization of p-q-strings
which are predicted by inflationary models rooted in String Theory, e.g. brane
inflation. In contrast to previously studied models describing p-q-strings our
model possesses a Bogomolnyi-Prasad-Sommerfield (BPS) limit. If cosmic strings
exist it would be exciting to detect them by direct observation. We propose
that this can be done by the observation of test particle motion in the
space-time of these objects. In order to be able to make predictions we have to
solve the field equations describing the configuration as well as the geodesic
equation numerically. The geodesics can then be classified according to the
test particle's energy, angular momentum and momentum along the string axis. We
find that the interaction of two Abelian-Higgs strings can lead to the
existence of bound orbits that would be absent without the interaction. We also
discuss the minimal and maximal radius of orbits and comment on possible
applications in the context of gravitational wave emission.Comment: v1: 22 pages including 17 figures; v2: new figure added, section on
observables added; acccepted for publication in Phys. Rev.
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
Analytic treatment of complete and incomplete geodesics in Taub-NUT space-times
We present the complete set of analytical solutions of the geodesic equation
in Taub-NUT space-times in terms of the Weierstrass elliptic function. We
systematically study the underlying polynomials and characterize the motion of
test particles by its zeros. Since the presence of the "Misner string" in the
Taub-NUT metric has led to different interpretations, we consider these in
terms of the geodesics of the space-time. In particular, we address the
geodesic incompleteness at the horizons discussed by Misner and Taub, and the
analytic extension of Miller, Kruskal and Godfrey, and compare with the
Reissner-Nordstr\"om space-time.Comment: 22 pages, 14 figures, accepted for publication in PR
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
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.
Particle Motion and Electromagnetic Fields of Rotating Compact Gravitating Objects with Gravitomagnetic Charge
The exact solution for the electromagnetic field occuring when the
Kerr-Taub-NUT compact object is immersed (i) in an originally uniform magnetic
field aligned along the axis of axial symmetry (ii) in dipolar magnetic field
generated by current loop has been investigated. Effective potential of motion
of charged test particle around Kerr-Taub-NUT gravitational source immersed in
magnetic field with different values of external magnetic field and NUT
parameter has been also investigated. In both cases presence of NUT parameter
and magnetic field shifts stable circular orbits in the direction of the
central gravitating object. Finally we find analytical solutions of Maxwell
equations in the external background spacetime of a slowly rotating magnetized
NUT star. The star is considered isolated and in vacuum, with monopolar
configuration model for the stellar magnetic field.Comment: 18 pages, 6 figures, new results in section 2 added, section 3 is
revised, 3 references are adde
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
Personalized medicine in the treatment of inflammatory bowel diseases
Personalized medicine (personalized medicine, individualized medicine) represents the totality of methods of prevention of a pathological condition, diagnosis and treatment in the event of its occurrence, based on individual patient characteristics. Such individual characteristics include genetic, epigenetic, and transcript, proteome, metabolomic and metagenomic markers, as well as a set of variable phenotypic traits - both of the patient's body and its separate tissues or cells. For example, treatment of inflammatory bowel diseases (IBD) can most clearly show the importance of applying personalized approaches. Currently in the treatment of patients with IBD paid great attention to genetic studies, monitoring of the concentration of the biological drugs and the level of antibodies to them, the role of microbiota as a predictor of effectiveness of therapy of IBD. Used clinical, laboratory, instrumental methods, as well as new biomarkers to assess the forecasting efficiency of conservative therapy in IBD patient. In the future treatment of patients with IBD will include a number of personalized data in order to better predict outcomes of the disease in each patient and more accurately select the appropriate treatment regimen
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