7,440 research outputs found
Gravitational Rutherford scattering and Keplerian orbits for electrically charged bodies in heterotic string theory
Properties of the motion of electrically charged particles in the background
of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) black hole is
presented in this paper. Radial and angular motion are studied analytically for
different values of the fundamental parameter. Therefore, gravitational
Rutherford scattering and Keplerian orbits are analysed in detail. Finally,
this paper complements previous work by Fernando for null geodesics (Phys. Rev.
D 85: 024033, 2012), Olivares & Villanueva (Eur. Phys. J. C 73: 2659, 2013) and
Blaga (Automat. Comp. Appl. Math. 22, 41 (2013); Serb. Astron. J. 190, 41
(2015)) for time-like geodesics.Comment: 11 pages, 12 figure
Massive neutral particles on heterotic string theory
The motion of massive particles in the background of a charged black hole in
heterotic string theory, which is characterized by a parameter , is
studied in detail in this paper. Since it is possible to write this space-time
in the Einstein frame, we perform a quantitative analysis of the time-like
geodesics by means of the standard Lagrange procedure. Thus, we obtain and
solve a set of differential equations and then we describe the orbits in terms
of the elliptic -Weierstra{\ss} function. Also, by making an elementary
derivation developed by Cornbleet (Am. J. Phys. \textbf{61} 7, (1993) 650 -
651) we obtain the correction to the angle of advance of perihelion to first
order in , and thus, by comparing with Mercury's data we give an
estimation for the value of this parameter, which yields an {\it heterotic
solar charge} .
Therefore, in addition to the study on null geodesics performed by Fernando
(Phys. Rev. D {\bf 85}, (2012) 024033), this work completes the geodesic
structure for this class of space-time.Comment: 12 pages, 8 figures. Accepted for publication on EPJ
Geodesic Structure of Lifshitz Black Holes in 2+1 Dimensions
We present a study of the geodesic equations of a black hole space-time which
is a solution of the three-dimensional NMG theory and is asymptotically
Lifshitz with and as found in [Ayon-Beato E., Garbarz A., Giribet
G. and Hassaine M., Phys. Rev. {\bf D} 80, 104029 (2009)]. By means of the
corresponding effective potentials for massive particles and photons we find
the allowed motions by the energy levels. Exact solutions for radial and
non-radial geodesics are given in terms of the Weierstrass elliptic ,
, and functions.Comment: 10 pages, 6 figures, accepted for publication in Eur. Phys. J.
The golden ratio in Schwarzschild-Kottler black holes
In this paper we show that the golden ratio is present in the
Schwarzschild-Kottler metric. For null geodesics with maximal radial
acceleration, the turning points of the orbits are in the golden ratio . This is a general result which is independent of the value and
sign of the cosmological constant
Stabilization in relation to wavenumber in HDG methods
Simulation of wave propagation through complex media relies on proper
understanding of the properties of numerical methods when the wavenumber is
real and complex. Numerical methods of the Hybrid Discontinuous Galerkin (HDG)
type are considered for simulating waves that satisfy the Helmholtz and Maxwell
equations. It is shown that these methods, when wrongly used, give rise to
singular systems for complex wavenumbers. A sufficient condition on the HDG
stabilization parameter for guaranteeing unique solvability of the numerical
HDG system, both for Helmholtz and Maxwell systems, is obtained for complex
wavenumbers. For real wavenumbers, results from a dispersion analysis are
presented. An asymptotic expansion of the dispersion relation, as the number of
mesh elements per wave increase, reveal that some choices of the stabilization
parameter are better than others. To summarize the findings, there are values
of the HDG stabilization parameter that will cause the HDG method to fail for
complex wavenumbers. However, this failure is remedied if the real part of the
stabilization parameter has the opposite sign of the imaginary part of the
wavenumber. When the wavenumber is real, values of the stabilization parameter
that asymptotically minimize the HDG wavenumber errors are found on the
imaginary axis. Finally, a dispersion analysis of the mixed hybrid
Raviart-Thomas method showed that its wavenumber errors are an order smaller
than those of the HDG method
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