arXiv subjects

Craig Copi

Publications and source records attributed to Craig Copi.

3 recordsLinked to original sources

arXiv2026

No persuasive evidence yet of gravitational-wave tails from perturbers along the line of sight in LVK observations

Observations of compact binary coalescences (CBCs) by the LIGO-Virgo-KAGRA collaboration resulted in 90 events in the first three observing runs. We search the data near the loudest of these detections for so-called "gravitational glints," by performing Bayesian model comparison. Gravitational glints are gravitational-wave tails caused by interactions between a signal and a spacetime perturber and are theorized to present as echoes of the primary signal. We do not find convincing evidence of gravitational glints in binary black hole or intermediate-mass black hole binary events with a signal-to-noise ratio (SNR) of at least 12. We also found that standard matched-filter CBC searches with template banks that do not contain gravitational glints would likely not have missed signals containing a gravitational glint. We therefore estimate upper limits on the probability of a glint as a function of its relative amplitude and use these estimates to constrain the properties of perturbers in the Universe. With increased sensitivity in the fourth observing run, which will increase the number and SNR of detectable events, we remain optimistic that glints will soon be detectable.

gr-qc↗

arXiv2022

Gravitational glint: Detectable gravitational wave tails from stars and compact objects

Observations of a merging neutron star binary in both gravitational waves, by the Laser Interferometer Gravitational-wave Observatory (LIGO), and across the spectrum of electromagnetic radiation, by myriad telescopes, have been used to show that gravitational waves travel in vacuum at a speed that is indistinguishable from that of light to within one part in a quadrillion. However, it has long been expected mathematically that, when electromagnetic or gravitational waves travel through vacuum in a curved spacetime, the waves develop "tails" that travel more slowly. The associated signal has been thought to be undetectably weak. Here we demonstrate that gravitational waves are efficiently scattered by the curvature sourced by ordinary compact objects -- stars, white dwarfs, neutron stars, and planets -- and certain candidates for dark matter, populating the interior of the null cone. The resulting "gravitational glint" should imminently be detectable, and be recognizable (for all but planets) as briefly delayed echoes of the primary signal emanating from extremely near the direction of the primary source. This opens the prospect for using GRAvitational Detection And Ranging (GRADAR) to map the Universe and conduct a comprehensive census of massive compact objects, and ultimately to explore their interiors.

gr-qc↗

arXiv2018

CMB Spectral Distortions from Cooling Macroscopic Dark Matter

We propose a new mechanism by which dark matter (DM) can affect the early universe. The hot interior of a macroscopic DM, or macro, can behave as a heat reservoir so that energetic photons are emitted from its surface. This results in spectral distortions (SDs) of the cosmic microwave background. The SDs depend on the density and the cooling processes of the interior, and the surface composition of the Macros. We use neutron stars as a model for nuclear-density Macros and find that the spectral distortions are mass-independent for fixed density. In our work, we find that, for Macros of this type that constitute 100$\%$ of the dark matter, the $\mu$ and $y$ distortions can be above detection threshold for typical proposed next-generation experiments such as PIXIE.

astro-ph.CO↗