Cherenkov Gravitational Radiation During the Radiation Era. (arXiv:2108.13463v2 [gr-qc] UPDATED)
<a href="http://arxiv.org/find/gr-qc/1/au:+Chu_Y/0/1/0/all/0/1">Yi-Zen Chu</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Liu_Y/0/1/0/all/0/1">Yen-Wei Liu</a>
Cherenkov radiation may occur whenever the source is moving faster than the
waves it generates. In a radiation dominated universe, with equation-of-state
$w = 1/3$, we have recently shown that the Bardeen scalar-metric perturbations
contribute to the linearized Weyl tensor in such a manner that its wavefront
propagates at acoustic speed $sqrt{w}=1/sqrt{3}$. In this work, we explicitly
compute the shape of the Bardeen Cherenkov cone and wedge generated
respectively by a supersonic point mass (approximating a primordial black hole)
and a straight Nambu-Goto wire (approximating a cosmic string) moving
perpendicular to its length. When the black hole or cosmic string is moving at
ultra-relativistic speeds, we also calculate explicitly the sudden surge of
scalar-metric induced tidal forces on a pair of test particles due to the
passing Cherenkov shock wave. These forces can stretch or compress, depending
on the orientation of the masses relative to the shock front’s normal.
Cherenkov radiation may occur whenever the source is moving faster than the
waves it generates. In a radiation dominated universe, with equation-of-state
$w = 1/3$, we have recently shown that the Bardeen scalar-metric perturbations
contribute to the linearized Weyl tensor in such a manner that its wavefront
propagates at acoustic speed $sqrt{w}=1/sqrt{3}$. In this work, we explicitly
compute the shape of the Bardeen Cherenkov cone and wedge generated
respectively by a supersonic point mass (approximating a primordial black hole)
and a straight Nambu-Goto wire (approximating a cosmic string) moving
perpendicular to its length. When the black hole or cosmic string is moving at
ultra-relativistic speeds, we also calculate explicitly the sudden surge of
scalar-metric induced tidal forces on a pair of test particles due to the
passing Cherenkov shock wave. These forces can stretch or compress, depending
on the orientation of the masses relative to the shock front’s normal.
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