Four Novel Observational Tests of General Relativity. (arXiv:2205.02746v3 [gr-qc] UPDATED)
<a href="http://arxiv.org/find/gr-qc/1/au:+Loeb_A/0/1/0/all/0/1">Abraham Loeb</a> (Harvard)
I study four novel observational tests of general relativity. First, I show
that a gravitational wave pulse from a major merger of massive black holes at
the Galactic center induces a permanent increase in the Earth-Moon separation.
For black holes of a few million solar masses, the shift in the local
gravitational potential is comparable to the Earth-Moon potential, leading to
the Moon being perturbed relative to the Earth during the passage of the pulse.
The permanent increase in the Earth-Moon separation is a fraction of a
millimeter, measurable by lunar ranging for future merger events. Second, I
show that General Relativity sets an absolute upper limit on the energy flux
observed from a cosmological source as a function of its redshift. Third, I
consider the implications of modified inertia at low accelerations for rockets.
An attractive interpretation of MOdified Newtonian Dynamics (MOND) as an
alternative to dark matter, changes the inertia of matter at accelerations
a<a_0=1.2×10^{-8} cm/s^2. I show that if inertia is modified at low
accelerations, this suppresses the exponential factor for the required fuel
mass in low acceleration journeys. Rockets operating at a<<a_0 might allow
intergalactic travel with a modest fuel-to-payload mass ratio. Fourth, I show
that the tidal gravitational potential of the Milky-Way galaxy removes fuzzy
dark matter from its satellite dwarf galaxies through quantum-mechanical
tunneling. The existence of dark matter in satellites rules-out ultra-light
axions (ULAs) as dark matter with a particle mass, $m_a< 2times 10^{-21}~{rm
eV}$. This limit exceeds the canonical mass range proposed as a solution to the
small-scale challenges of the cold-dark-matter paradigm.
I study four novel observational tests of general relativity. First, I show
that a gravitational wave pulse from a major merger of massive black holes at
the Galactic center induces a permanent increase in the Earth-Moon separation.
For black holes of a few million solar masses, the shift in the local
gravitational potential is comparable to the Earth-Moon potential, leading to
the Moon being perturbed relative to the Earth during the passage of the pulse.
The permanent increase in the Earth-Moon separation is a fraction of a
millimeter, measurable by lunar ranging for future merger events. Second, I
show that General Relativity sets an absolute upper limit on the energy flux
observed from a cosmological source as a function of its redshift. Third, I
consider the implications of modified inertia at low accelerations for rockets.
An attractive interpretation of MOdified Newtonian Dynamics (MOND) as an
alternative to dark matter, changes the inertia of matter at accelerations
a<a_0=1.2×10^{-8} cm/s^2. I show that if inertia is modified at low
accelerations, this suppresses the exponential factor for the required fuel
mass in low acceleration journeys. Rockets operating at a<<a_0 might allow
intergalactic travel with a modest fuel-to-payload mass ratio. Fourth, I show
that the tidal gravitational potential of the Milky-Way galaxy removes fuzzy
dark matter from its satellite dwarf galaxies through quantum-mechanical
tunneling. The existence of dark matter in satellites rules-out ultra-light
axions (ULAs) as dark matter with a particle mass, $m_a< 2times 10^{-21}~{rm
eV}$. This limit exceeds the canonical mass range proposed as a solution to the
small-scale challenges of the cold-dark-matter paradigm.
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