Colloquium APC

GWTC-1: First LIGO/Virgo Gravitational-Wave Transient Catalog

Abstract: After the end of the O2 observing run, the LIGO and Virgo data were reprocessed and reanalyzed delivering the final O1 and O2 results. We will discuss the content of the catalog consisting of 10 BBH merger signals (4 of which are new discoveries) and one BNS merger signal (arXiv:1811.12907). We will also report the results of the companion article devoted to the astrophysical rates and parameters of the previously not known stellar-mass BH population (arXiv:1811.12940).

Colloquium APC : Concordance of the Dirac-Milne Universe

Concordance of the Dirac-Milne universe

« The Dirac-Milne universe, a matter-antimatter universe where antimatter
has a negative gravitational mass, presents several elements
of concordance with our universe, except apparently for two tests:
primordial helium-3, and BAO, at least if the latter is interpreted in a
conventional way.
After a discussion on the definition of a negative mass particle,
I will describe the formation of structures in the Dirac-Milne universe,

Kinetic Inductance Detectors (KIDs)

Kinetic inductance detector (KID) is a promising technology for astronomy with high sensitivity, microsecond timing and intrinsic multiplexing readout properties. Based on these advantages, a wide range of application has been proposed from millimeter to X-ray. With simple fabrication and frequency domain multiplexing readout, hundreds of KID pixels could be easily read out with single cable. In the last decade, KID has been developed rapidly. This talk will introduce the recent development of KIDs for frequency range from 100 GHz to 1 THz.

Studying black hole populations with gravitational-wave observations

The first observations of gravitational waves emitted by merging binary black holes demonstrated the existence of black holes more massive than ever observed in our Galaxy. Future observations with ground-based interferometers such as Advanced LIGO and Virgo will probe the mass and spin distributions of black holes in various galactic environments and may also detect the stochastic gravitational-wave background from unresolved mergers. These measurements will provide a new tool for stellar and galaxy evolution studies.

Physics of Gravitational Redshifts in Clusters of Galaxies

Wojtak, Hansen and Hjorth and others have measured the long-predicted gravitational redshift of light escaping from galaxy clusters.  The effect is very small, corresponding to a velocity shift of only ~10 km/s, but the result appears to be fairly robust and seemed to be in good agreement with general relativity predictions and possibly in conflict with some alternative theories. The effect was initially imagined to be a simple astronomical analogue of the famous terrestrial Pound and Rebka experiment that verified Einstein's theoretical prediction.


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