Gravitational atoms

Abstract

Particles in a yet unexplored dark sector with sufficiently large mass and small gauge coupling may form purely gravitational atoms (quantum gravitational bound states) with a rich phenomenology. In particular, we investigate the possibility of having an observable signal of gravitational waves or ultra high energy cosmic rays from the decay of gravitational atoms. We show that if ordinary Einstein gravity holds up to the Planck scale, then, within the ΛCDM model, the frequency of the gravitational wave signal produced by the decays is always higher than 10 13 Hz. An observable signal of gravitational waves with smaller frequency from such decays, in addition to probing near Planckian dark physics, would also imply a departure from Einstein gravity near the Planck scale or an early epoch of non-standard cosmology. As an example, we consider an early universe cosmology with a matter-dominated phase, violating our assumption that the universe is radiation dominated after reheating, which gives a signal in an interesting frequency range for near Planckian bound states. We also show how gravitational atoms arise in the minimal PIDM scenario and compute their gravitational wave signature. 1 ngnielsen@cp3.sdu.dk 2 palessandro@cp3.sdu.dk 3 sloth@cp3.sdu.dk 1 arXiv:1903.12168v1 [hep-ph]

Searching for black hole echoes from the LIGO-Virgo catalog GWTC-1

“…As mentioned in Introduction, previous injection studies [18][19][20] show that if the amplitude of the first echo is larger than 15% of the peak amplitude of the binary black hole merger, echo signals can be detected by the current detector sensitivity, assuming frequencyindependent reflection rate. Combined with their studies, our results suggest that the amplitude of echo signals should be much smaller than the peak amplitude of the merger even if echo signals exist.…”

“…where r max is the peak of the angular momentum barrier and ∆r is the location of the membrane away from the horizon, r + . In the previous studies [16,[18][19][20], the frequency-independent reflection rate and ∆t echo are assumed to be parameters. In our case, since both the reflection rate and ∆t echo depend on a and M, we set (a, M) as parameters instead of [R( f ), ∆t echo ].…”

“…The cutoff function is determined by a cutoff parameter t 0 and the typical frequency around the merger time ω. The cutoff parameter is also a parameter in [16,[18][19][20], however, since it is insensitive to the signal-to-noise ratio defined in the next section, to save the computational cost, we set t 0 as a constant. Following the best fit value of t 0 obtained in [16], we set t 0 = −0.084 ∆t echo for GW150914 and t 0 = −0.1 ∆t echo for the rest of the events.…”

“…However, Asthon et al [17] have pointed out some problems in the analysis done by Abedi et al and Westerweck et al [18] have improved the background estimation using 4096 seconds data around each binary black hole event, which gave lower significance, 0.032 in p-value, than in Abedi et al. Using the same template waveform given in Abedi et al, Nielsen et al [19] and Lo et al [20] have also shown lower significance on echo signals evaluated by Bayes factor using Bayesian analysis, where Lo et al have included the inspiral-merger-ringdown waveform into the template as well. Injection studies given in [18][19][20] have shown that echo signals with their amplitude of the first echo larger than about 15% of the merger amplitude are detectable within the current detector sensitivity.…”

“…Using the same template waveform given in Abedi et al, Nielsen et al [19] and Lo et al [20] have also shown lower significance on echo signals evaluated by Bayes factor using Bayesian analysis, where Lo et al have included the inspiral-merger-ringdown waveform into the template as well. Injection studies given in [18][19][20] have shown that echo signals with their amplitude of the first echo larger than about 15% of the merger amplitude are detectable within the current detector sensitivity.…”