scholarly journals Null geodesics and red–blue shifts of photons emitted from geodesic particles around a noncommutative black hole space–time

2018 ◽  
Vol 33 (16) ◽  
pp. 1850098 ◽  
Author(s):  
Ravi Shankar Kuniyal ◽  
Rashmi Uniyal ◽  
Anindya Biswas ◽  
Hemwati Nandan ◽  
K. D. Purohit
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Noncommutative Geometry ◽  
Equatorial Plane ◽  
Mass Parameter ◽  
Space Time ◽  
Geodesic Motion ◽  
Schwarzschild Black Hole ◽  
Gravitational Fields ◽  
Test Particles

We investigate the geodesic motion of massless test particles in the background of a noncommutative geometry-inspired Schwarzschild black hole. The behavior of effective potential is analyzed in the equatorial plane and the possible motions of massless particles (i.e. photons) for different values of impact parameter are discussed accordingly. We have also calculated the frequency shift of photons in this space–time. Further, the mass parameter of a noncommutative inspired Schwarzschild black hole is computed in terms of the measurable redshift of photons emitted by massive particles moving along circular geodesics in equatorial plane. The strength of gravitational fields of noncommutative geometry-inspired Schwarzschild black hole and usual Schwarzschild black hole in General Relativity is also compared.

Space–Time Defects: Torsion Walls

1997 ◽  
Vol 12 (27) ◽  
pp. 2005-2009 ◽  
Author(s):  
L. C. Garcia de Andrade
Keyword(s):  
De Sitter Space ◽  
Space Time ◽  
Geodesic Motion ◽  
De Sitter ◽  
Gravitational Fields ◽  
Test Particles ◽  
Minkowski Spaces ◽  
Static Torsion

The geometry of torsion defects in Weitzenböck space–time is investigated. Conformal de Sitter space–time outside the defect is obtained. Geodesic motion of test particles outside the torsion wall is given. Torsion defect wall is shown to have repulsive gravitational fields. Static torsion defect is obtained by gluing together two half Minkowski spaces across a torsion wall junction.

scholarly journals A pseudo-Newtonian description of any stationary space-time

2016 ◽  
Vol 12 (S324) ◽  
pp. 45-46
Author(s):  
Vojtěch Witzany ◽  
Claus Lämmerzahl
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Strong Field ◽  
Kerr Black Hole ◽  
Space Time ◽  
Schwarzschild Black Hole ◽  
Test Particles ◽  
Kerr Field ◽  
Alternative Gravity Theories ◽  
Static Space

AbstractSince the first investigations into accretion onto black holes, astrophysicists have proposed effective Newtonian-like potentials to mimic the strong-field behavior of matter near a Schwarzschild or Kerr black hole. On the other hand, the fields of neutron stars or black holes in many of the alternative gravity theories differ from the idealized Schwarzschild or Kerr field which would require a number of new potentials. To resolve this, we give a Newtonian-like Hamiltonian which almost perfectly mimics the behavior of test particles in any given stationary space-time. The properties of the Hamiltonian are excellent in static space-times such as the Schwarzschild black hole, but become worse for space-times with gravito-magnetic or dragging effects such as near the Kerr black hole.

scholarly journals ASYMPTOTIC QUASINORMAL MODES OF A NONCOMMUTATIVE GEOMETRY INSPIRED SCHWARZSCHILD BLACK HOLE

2007 ◽  
Vol 22 (11) ◽  
pp. 2047-2056 ◽  
Author(s):  
PULAK RANJAN GIRI
Keyword(s):  
Black Hole ◽  
Noncommutative Geometry ◽  
Quasinormal Modes ◽  
Space Time ◽  
Hawking Temperature ◽  
Scalar Perturbation ◽  
Schwarzschild Black Hole ◽  
The Real ◽  
Quasinormal Frequency

We study the asymptotic quasinormal modes for the scalar perturbation of the noncommutative geometry inspired Schwarzschild black hole in 3+1 dimensions. We have considered M ≥ M0, which effectively correspond to a single horizon Schwarzschild black hole with correction due to noncommutativity. We have shown that for this situation the real part of the asymptotic quasinormal frequency is proportional to ln (3). The effect of noncommutativity of space–time on quasinormal frequency arises through the constant of proportionality, which is Hawking temperature TH(θ). We also consider the two-horizons case and show that in this case also the real part of the asymptotic quasinormal frequency is proportional to ln (3).

Dirac quasi-normal frequencies in a noncommutative black hole space–time

2019 ◽  
Vol 97 (5) ◽  
pp. 562-565
Author(s):  
Cuibai Luo ◽  
Chen Wu
Keyword(s):  
Black Hole ◽  
Quantum Gravity ◽  
Noncommutative Geometry ◽  
Imaginary Part ◽  
Normal Modes ◽  
Space Time ◽  
Numerical Results ◽  
Schwarzschild Black Hole ◽  
Oscillation Frequencies ◽  
Noncommutative Parameter

Noncommutative geometry may be an alternative way to quantum gravity. We study the influence of the space–time noncommutative parameter on the Dirac quasi-normal modes in the noncommutative Schwarzschild black hole space–times. In comparison to the commutative Schwarzschild black hole, the numerical results show that the oscillation frequencies and magnitude of the imaginary part of the Dirac quasi-normal modes will increase. However, it is found that the influence of the space–time noncommutative parameter on the Dirac quasi-normal modes is tiny and negligible.

scholarly journals WEYL GEOMETRY AS CHARACTERIZATION OF SPACE-TIME

2011 ◽  
Vol 03 ◽  
pp. 87-97 ◽  
Author(s):  
F. P. POULIS ◽  
J. M. SALIM
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Riemannian Geometry ◽  
Axiomatic Approach ◽  
Space Time ◽  
Weyl Geometry ◽  
Test Particles ◽  
Variational Formalism ◽  
Physical Fields

Motivated by an axiomatic approach to characterize space-time it is investigated a reformulation of Einstein's gravity where the pseudo-riemannian geometry is substituted by a Weyl one. It is presented the main properties of the Weyl geometry and it is shown that it gives extra contributions to the trajectories of test particles, serving as one more motivation to study general relativity in Weyl geometry. It is introduced its variational formalism and it is established the coupling with other physical fields in such a way that the theory acquires a gauge symmetry for the geometrical fields. It is shown that this symmetry is still present for the red-shift and it is concluded that for cosmological models it opens the possibility that observations can be fully described by the new geometrical scalar field. It is concluded then that this reformulation, although representing a theoretical advance, still needs a complete description of their objects.

scholarly journals BLACK HOLE EVAPORATION BASED UPON A q-DEFORMATION DESCRIPTION

2005 ◽  
Vol 20 (26) ◽  
pp. 6039-6049 ◽  
Author(s):  
XIN ZHANG
Keyword(s):  
Black Hole ◽  
Degrees Of Freedom ◽  
Radiation Spectrum ◽  
Correlation Effect ◽  
Space Time ◽  
Noncommutative Space ◽  
Schwarzschild Black Hole ◽  
Black Hole Evaporation ◽  
Starting Point ◽  
New Distribution

A toy model based upon the q-deformation description for studying the radiation spectrum of black hole is proposed. The starting point is to make an attempt to consider the space–time noncommutativity in the vicinity of black hole horizon. We use a trick that all the space–time noncommutative effects are ascribed to the modification of the behavior of the radiation field of black hole and a kind of q-deformed degrees of freedom are postulated to mimic the radiation particles that live on the noncommutative space–time, meanwhile the background metric is preserved as usual. We calculate the radiation spectrum of Schwarzschild black hole in this framework. The new distribution deviates from the standard thermal spectrum evidently. The result indicates that some correlation effect will be introduced to the system if the noncommutativity is taken into account. In addition, an infrared cutoff of the spectrum is the prediction of the model.

Complex Spacetimes and the Newman-Janis Trick

2021 ◽  
Author(s):  
◽  
Del Rajan
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Mathematical Theory ◽  
Kerr Black Hole ◽  
Complex Variables ◽  
Complex Manifolds ◽  
Schwarzschild Black Hole ◽  
The Subject ◽  
Short Method

<p>In this thesis, we explore the subject of complex spacetimes, in which the mathematical theory of complex manifolds gets modified for application to General Relativity. We will also explore the mysterious Newman-Janis trick, which is an elementary and quite short method to obtain the Kerr black hole from the Schwarzschild black hole through the use of complex variables. This exposition will cover variations of the Newman-Janis trick, partial explanations, as well as original contributions.</p>

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