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Papers by Saeed Mirshekari
Bulletin of the American Physical Society, Jan 1, 2011
Submitted for the APR11 Meeting of The American Physical Society Sorting Category: C3. (T)
Physical Review D, Jan 1, 2012
Modified gravity theories generically predict a violation of Lorentz invariance, which may lead t... more Modified gravity theories generically predict a violation of Lorentz invariance, which may lead to a modified dispersion relation for propagating modes of gravitational waves. We construct a parametrized dispersion relation that can reproduce a range of known Lorentz-violating predictions and investigate their impact on the propagation of gravitational waves. A modified dispersion relation forces different wavelengths of the gravitational wave train to travel at slightly different velocities, leading to a modified phase evolution observed at a gravitational-wave detector. We show how such corrections map to the waveform observable and to the parametrized post-Einsteinian framework, proposed to model a range of deviations from General Relativity. Given a gravitationalwave detection, the lack of evidence for such corrections could then be used to place a constraint on Lorentz violation. The constraints we obtain are tightest for dispersion relations that scale with small power of the graviton's momentum and deteriorate for a steeper scaling.
Bulletin of the American Physical Society, Jan 1, 2010
... Abstract: K14.00007 : Searching for a Carter-like constant of motion in the Bach-Weyl solutio... more ... Abstract: K14.00007 : Searching for a Carter-like constant of motion in the Bach-Weyl solution. 4:42 PM4:54 PM. Preview Abstract. Authors: Saeed Mirshekari (Washington University, St. Louis). Clifford Will (Washington University, St. Louis). ...
In Newtonian gravity, a stationary axisymmetric system admits a third, Carter-like constant of mo... more In Newtonian gravity, a stationary axisymmetric system admits a third, Carter-like constant of motion if its mass multipole moments are related to each other in exactly the same manner as for the Kerr black-hole spacetime. The Newtonian source with this property consists of two point masses at rest a fixed distance apart. The integrability of motion about this source was first studied in the 1760s by Euler. We show that the general relativistic analogue of the Euler problem, the Bach-Weyl solution, does not admit a Carter-like constant of motion, first, by showing that it does not possess a non-trivial Killing tensor, and secondly, by showing that the existence of a Carter-like constant for the two-center problem fails at the first post-Newtonian order.
In this paper, we elaborate the problem of energy-momentum in GR by energy-momentum prescriptions... more In this paper, we elaborate the problem of energy-momentum in GR by energy-momentum prescriptions theory. In this regard, we calculate Møller, Landau-Lifshitz, Papapetrou, Einstein, Bergmann, Tolman, and Weinberg's energy-momentum complexes in static and non-static cosmic string space-times. We obtain strong coincidences between the results. These coincidences can be considered as an extension of Virbhadra's viewpoint that different energy-momentum prescriptions may provide some basis to define a unique quantity. In addition, our results disagree with Lessner's belief about Møller's prescription, and support the Virbhadra's conclusion about power of Einstein's prescription.
Einstein, Landau-Lifshitz, Papapetrou, Weinberg, and Møller energy-momentum prescriptions in gene... more Einstein, Landau-Lifshitz, Papapetrou, Weinberg, and Møller energy-momentum prescriptions in general spherically symmetric space-times are investigated. It is shown that for two special but not unusual classes of general spherically symmetric space-times several energy-momentum prescriptions in Schwarzschild Cartesian coordinates lead to some coincidences in energy distribution. It is also obtained that for a special class of spherically symmetric metrics Møller and Einstein energymomentum prescriptions give the same result for energy distribution if and only if it has a specific dependence on radial coordinate.
Bulletin of the American Physical Society, Jan 1, 2011
Submitted for the APR11 Meeting of The American Physical Society Sorting Category: C3. (T)
Physical Review D, Jan 1, 2012
Modified gravity theories generically predict a violation of Lorentz invariance, which may lead t... more Modified gravity theories generically predict a violation of Lorentz invariance, which may lead to a modified dispersion relation for propagating modes of gravitational waves. We construct a parametrized dispersion relation that can reproduce a range of known Lorentz-violating predictions and investigate their impact on the propagation of gravitational waves. A modified dispersion relation forces different wavelengths of the gravitational wave train to travel at slightly different velocities, leading to a modified phase evolution observed at a gravitational-wave detector. We show how such corrections map to the waveform observable and to the parametrized post-Einsteinian framework, proposed to model a range of deviations from General Relativity. Given a gravitationalwave detection, the lack of evidence for such corrections could then be used to place a constraint on Lorentz violation. The constraints we obtain are tightest for dispersion relations that scale with small power of the graviton's momentum and deteriorate for a steeper scaling.
Bulletin of the American Physical Society, Jan 1, 2010
... Abstract: K14.00007 : Searching for a Carter-like constant of motion in the Bach-Weyl solutio... more ... Abstract: K14.00007 : Searching for a Carter-like constant of motion in the Bach-Weyl solution. 4:42 PM4:54 PM. Preview Abstract. Authors: Saeed Mirshekari (Washington University, St. Louis). Clifford Will (Washington University, St. Louis). ...
In Newtonian gravity, a stationary axisymmetric system admits a third, Carter-like constant of mo... more In Newtonian gravity, a stationary axisymmetric system admits a third, Carter-like constant of motion if its mass multipole moments are related to each other in exactly the same manner as for the Kerr black-hole spacetime. The Newtonian source with this property consists of two point masses at rest a fixed distance apart. The integrability of motion about this source was first studied in the 1760s by Euler. We show that the general relativistic analogue of the Euler problem, the Bach-Weyl solution, does not admit a Carter-like constant of motion, first, by showing that it does not possess a non-trivial Killing tensor, and secondly, by showing that the existence of a Carter-like constant for the two-center problem fails at the first post-Newtonian order.
In this paper, we elaborate the problem of energy-momentum in GR by energy-momentum prescriptions... more In this paper, we elaborate the problem of energy-momentum in GR by energy-momentum prescriptions theory. In this regard, we calculate Møller, Landau-Lifshitz, Papapetrou, Einstein, Bergmann, Tolman, and Weinberg's energy-momentum complexes in static and non-static cosmic string space-times. We obtain strong coincidences between the results. These coincidences can be considered as an extension of Virbhadra's viewpoint that different energy-momentum prescriptions may provide some basis to define a unique quantity. In addition, our results disagree with Lessner's belief about Møller's prescription, and support the Virbhadra's conclusion about power of Einstein's prescription.
Einstein, Landau-Lifshitz, Papapetrou, Weinberg, and Møller energy-momentum prescriptions in gene... more Einstein, Landau-Lifshitz, Papapetrou, Weinberg, and Møller energy-momentum prescriptions in general spherically symmetric space-times are investigated. It is shown that for two special but not unusual classes of general spherically symmetric space-times several energy-momentum prescriptions in Schwarzschild Cartesian coordinates lead to some coincidences in energy distribution. It is also obtained that for a special class of spherically symmetric metrics Møller and Einstein energymomentum prescriptions give the same result for energy distribution if and only if it has a specific dependence on radial coordinate.