Crashing Neutron Stars on the Italian Dolomites

Bruno Giacomazzo, Andrea Endrizzi, Riccardo Ciolfi, Wolfgang Kastaun share details of their latest research published in the CQG focus issue: Rattle and shine: the signals from compact binary mergers.

Bruno Giacomazzo, Andrea Endrizzi, Riccardo Ciolfi, Wolfgang Kastaun

From left to right: Bruno Giacomazzo, Andrea Endrizzi, Riccardo Ciolfi, Wolfgang Kastaun.
About the authors: Bruno Giacomazzo is an assistant professor at the Department of Physics of the University of Trento and the Principal Investigator of the numerical relativity group there. The group is currently composed of two postdocs (Riccardo Ciolfi and Wolfgang Kastaun) and two PhD students (Andrea Endrizzi and Takumu Kawamura).

At the end of 2013, after seven years spent abroad (between Germany and the USA),  Bruno Giacomazzo came back to Italy for an assistant professor position at the University of Trento in Northern Italy. He used to come to this region when he was a kid to hike or ski on the mountains, but he never thought he would have come back here to study neutron star mergers.

Thanks to financial support from MIUR (Ministry of Education, University, and Research) he was able to attract Riccardo Ciolfi and Wolfgang Kastaun from abroad and to create with them the first numerical relativity group in this part of Italy. Thanks to Continue reading

The spin limit of colliding black holes

Geoffrey Lovelace

Geoffrey Lovelace is an Assistant Professor of Physics at California State University, Fullerton. As member of Fullerton’s Gravitational-Wave Physics and Astronomy Center and the Simulating eXtreme Spacetimes collaboration, his research interests focus on using computer simulations to model colliding black holes and neutron stars and the gravitational waves they emit.

A single black hole’s size limits its spin. Do colliding black holes obey this limit?

In our recent paper, published in Classical and Quantum Gravity, we take a first look at how supercomputer simulations can help reveal the answer.

A black hole is an object whose gravity is so strong that nothing, even light, can escape from inside its horizon. An isolated, uncharged black hole can be completely described by just two numbers: its spin and its horizon surface area. All of the black hole’s properties then follow from Kerr’s solution of Einstein’s equations.

Kerr’s solution implies that a single black hole can spin no faster than its horizon area times a constant: spinning any faster would destroy the horizon. Astronomers have found evidence that some black holes spin very close to the limit (but still below it). Mathematical relativists have proven that this spin limit is obeyed not only by Continue reading

High-order fully general-relativistic hydrodynamics: new approaches and tests

Pablo Laguna

Pablo Laguna is the Chair of the School of Physics at Georgia Tech

As we approach the era of gravitational-wave astrophysics driven by observations, it is imperative to have general-relativistic hydrodynamic codes capable of revealing in exquisite detail phenomena driven by strong dynamical gravity.

In this paper, Radice, Rezzolla and Galeazzi introduce a new approach to build a code, called WhiskyTHC, with the potential to help deliver that. The new approach borrows elements from the Whisky and Template Hydrodynamics codes. The Whisky code is widely used by the numerical relativity community, and the Continue reading

General-relativistic hydrodynamics: going beyond second-order convergence

High accuracy in numerical relativity simulations is essential: now it can also be achieved for non-vacuum spacetimes.

Merging binary neutron stars are among the most promising sources of gravitational waves (GWs) for the next generation of interferometric detectors. Such waves carry valuable information about the masses, radii, and deformability of the two stars. Even a single detection would set stringent constraints on the equation of state of nuclear matter, which is still poorly known. Gravitational-wave observations, in combination with electromagnetic/neutrino counterparts, would also help to unravel the mystery behind gamma-ray bursts. Continue reading