Papers by Abhinandan Dass
General Relativity and Gravitation, 2019
We confront the predicted gyroscopic precession (in particular the geodetic precession) from metr... more We confront the predicted gyroscopic precession (in particular the geodetic precession) from metric f (R) theory with the data provided by the mission, Gravity Probe-B. We find the constraint, |a 2 | < 1.33×10 12 m 2 , where a 2 is the coefficient assessing the strength of the lowest order correction to the Einstein-Hilbert action for a metric f (R) theory with f analytic. This constraint improves over astrophysical bounds provided by massive black holes and planetary precession which are |a 2 | 10 17 m 2 and |a 2 | 1.2 × 10 18 m 2 respectively and it is complementary to the stringent ones provided by lab based experiments, like the Eöt-Wash experiment. We also investigate the modification of our result for gyroscopic precession if the oblateness of Earth is taken into account by considering the quadrupole moment of Earth. Finally, we provide a generalisation of our result for the gyroscopic precession in the context of Brans-Dicke theories with a potential (recovering the previously derived results in the appropriate limits).
General Relativity and Gravitation, 2019
A Gravitoelectromagnetism formalism in the context of metric f (R) theory is presented and the an... more A Gravitoelectromagnetism formalism in the context of metric f (R) theory is presented and the analogue Lorentz force law is derived. Some interesting results such as the dependence of the deviation from General Relativity on the absolute value of the scalar potential are found, it is also found that the f (R) effects are only relevant at a shorter distance or when the distance is much less than the compton wavelength, and that the effects are attractive in nature. An investigation of gravitational time delay in the context of metric f (R) is also presented showing that the Ricci scalar alone is responsible for the time delay effect which seems to suggest that the extra scalar degree of freedom associated to f (R) does not provide any modification. Also, to generalise our results, the Lorentz force law and gravitational time delay in the case of Brans-Dicke theories with a potential are derived; it is shown that the results are consistent with those obtained in the case of metric f (R) and General Relativity in the appropriate limits. Keywords f (R) • Gravitolelectromagnetism • Brans-Dicke • gravitational time delay 1 Introduction: Gravitolelectromagnetism The parallelism between Gravitation and Electromagnetism can be traced back to the eighteenth century when Charles-Augustin de Coulomb forumlated the empirical inverse square Coloumb's law, F e = K q 1 q 2 |r| 2r , [1] describing the force between two charges q 1 and q 2 at a distance r where K is the Coloumb's constant. The form of the equation had a stark similarity with the Gravitational force law [2], F G = −G m 1 m 2 |r| 2r where G is the Gravitational constant and m 1 and m 2 are two masses. The analogy between gravity and electrodynamics also led to a postulate by Holzmüller [3]
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Papers by Abhinandan Dass