scholarly journals Phenomenological inclusion of alternative dispersion relations to the Teukolsky equation and its application to bounding the graviton mass with gravitational-wave measurements

2019 ◽  
Vol 99 (12) ◽  
Author(s):  
Adrian Ka-Wai Chung ◽  
Tjonnie Guang Feng Li
Keyword(s):  
Gravitational Wave ◽  
Dispersion Relations ◽  
Graviton Mass ◽  
Wave Measurements ◽  
Teukolsky Equation

scholarly journals Constraints on alternative theories of gravity with observations of the Galactic Center

2018 ◽  
Vol 191 ◽  
pp. 01010 ◽  
Author(s):  
Alexander Zakharov
Keyword(s):  
Black Hole ◽  
Gravitational Wave ◽  
Galactic Center ◽  
Alternative Theories Of Gravity ◽  
Significant Activity ◽  
Graviton Mass ◽  
The Future ◽  
Theories Of Gravity ◽  
Theory Of Gravity ◽  
Alternative Theories

To evaluate a potential usually one analyzes trajectories of test particles. For the Galactic Center case astronomers use bright stars or photons, so there are two basic observational techniques to investigate a gravitational potential, namely, (a) monitoring the orbits of bright stars near the Galactic Center as it is going on with 10m Keck twin and four 8m VLT telescopes equipped with adaptive optics facilities (in addition, recently the IR interferometer GRAVITY started to operate with VLT); (b) measuring the size and shape of shadows around black hole with VLBI-technique using telescopes operating in mm-band. At the moment, one can use a small relativistic correction approach for stellar orbit analysis, however, in the future the approximation will not be precise enough due to enormous progress of observational facilities and recently the GRAVITY team found that the first post-Newtonian correction has to be taken into account for the gravitational redshift in the S2 star orbit case. Meanwhile for smallest structure analysis in VLBI observations one really needs a strong gravitational field approximation. We discuss results of observations and their interpretations. In spite of great efforts there is a very slow progress to resolve dark matter (DM) and dark energy (DE) puzzles and in these circumstances in last years a number of alternative theories of gravity have been proposed. Parameters of these theories could be effectively constrained with of observations of the Galactic Center. We show some cases of alternative theories of gravity where their parameters are constrained with observations, in particular, we consider massive theory of gravity. We choose the alternative theory of gravity since there is a significant activity in this field and in the last years theorists demonstrated an opportunity to create such theories without ghosts, on the other hand, recently, the joint LIGO & Virgo team presented an upper limit on graviton mass such as mg< 1:2 × 10-22eV [1] analyzing gravitational wave signal in their first paper where they reported about the discovery of gravitational waves from binary black holes as it was suggested by C. Will [2]. So, the authors concluded that their observational data do not indicate a significant deviation from classical general relativity. We show that an analysis of bright star trajectories could estimate a graviton mass with a commensurable accuracy in comparison with an approach used in gravitational wave observations and the estimates obtained with these two approaches are consistent. Therefore, such an analysis gives an opportunity to treat observations of bright stars near the Galactic Center as a useful tool to obtain constraints on the fundamental gravity law. We showed that in the future graviton mass estimates obtained with analysis of trajectories of bright stars would be better than current LIGO bounds on the value, therefore, based on a potential reconstruction at the Galactic Center we obtain bounds on a graviton mass and these bounds are comparable with LIGO constraints. Analyzing size of shadows around the supermassive black hole at the Galactic Center (or/and in the center of M87) one could constrain parameters of different alternative theories of gravity as well.

scholarly journals The last three minutes: Issues in gravitational-wave measurements of coalescing compact binaries

1993 ◽  
Vol 70 (20) ◽  
pp. 2984-2987 ◽  
Author(s):  
Curt Cutler ◽  
Theocharis A. Apostolatos ◽  
Lars Bildsten ◽  
Lee Smauel Finn ◽  
Eanna E. Flanagan ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
Compact Binaries ◽  
Wave Measurements

scholarly journals Constraints on primordial black hole dark matter from Galactic center X-ray observations

2018 ◽  
Vol 618 ◽  
pp. A139 ◽  
Author(s):  
Andi Hektor ◽  
Gert Hütsi ◽  
Martti Raidal
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Gravitational Wave ◽  
Galactic Center ◽  
Model Parameters ◽  
Primordial Black Hole ◽  
Density Profiles ◽  
X Ray ◽  
Wave Measurements ◽  
Gas Accretion

Context. Surprisingly high masses of the black holes inferred from the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo gravitational wave measurements have lead to speculations that the observed mergers might be due to 𝒪(10) M⊙ primordial black holes (PBHs). Furthermore, it has been suggested that the whole amount of dark matter (DM) might be in that exotic form. Aims. We investigate constraints on the PBH DM using NuSTAR Galactic center (GC) X-ray data. Methods. We used a robust Monte Carlo approach in conjunction with a radiatively inefficient PBH accretion model with commonly accepted model parameters. Compared to previous studies we allowed for multiple forms of DM density profiles. Most importantly, our study includes treatment of the gas turbulence, which significantly modifies the relative velocity between PBHs and gas. Results. We show that inclusion of the effects of gas turbulence and the uncertainties related to the DM density profile reduces significantly the gas accretion onto PBHs compared to the claimed values in previous papers. It is highly improbable to obtain accreting PBHs brighter than the NuSTAR point source limit using observationally determined gas velocities. Conclusions. One can safely conclude that GC X-ray observations cannot rule out 𝒪(10) M⊙ PBH DM.

scholarly journals From Maximal Force to the Field Equations of General Relativity

2021 ◽  
Author(s):  
C Sivaram ◽  
Arun Kenath ◽  
Christoph Schiller
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Elastic Constant ◽  
Gravitational Wave ◽  
Special Relativity ◽  
Field Equations ◽  
Maximal Force ◽  
Wave Measurements ◽  
Maximal Speed

We point out that field equations of general relativity are implied by a maximal force given by c4/4G, analogous to the way that special relativity is implied by a maximal speed given by c. We present some of the arguments for this equivalence. The maxi-mal force naturally plays the role of an elastic constant for space-time. Implications of the maximal force for gravitational wave measurements, cosmology and black holes are highlighted. Quantum aspects of the maximal force are discussed.

Sign in / Sign up

Export Citation Format

Share Document