Daily Archives: March 24, 2014

Melvin magnetic cosmologies

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Magnetic fields are ubiquitous in the universe – observed on scales ranging from stellar, through galactic and beyond – and are key to the physics of dramatic astrophysical objects such as pulsars and active galactic nuclei. Meanwhile, the origin of large-scale magnetic fields is still a topic of great debate in the cosmological literature.

Our recent CQG article presents a new family of exact solutions to the Einstein-Maxwell equations for cosmological magnetic fields. These solutions are both inhomogeneous and anisotropic, with the magnetic field having nontrivial dependence on Continue reading →

Probing the notion of gravitational entropy in inhomogeneous cosmologies

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Roberto Sussman

Dr Roberto A Sussman is a senior researcher in Theoretical Cosmology at the Institute for Nuclear Sciences (ICN) of the National University of Mexico (UNAM).

One of the long standing open problems in General Relativity is to find a self-consistent theoretically robust definition of a classical “gravitational” entropy, which is distinct (though possibly connected) to the entropy of the field sources (hydrodynamical or non-collisional) and to holographic and black hole entropies. Current research has produced two main classical gravitational entropy proposals: one by Clifton, Ellis and Tavakol, based on an effective construction from the “free” gravitational field associated to the Bell-Robinson tensor (the CET proposal), the other, by Hosoya and Buchert, is based on the Kullback-Leibler functional of Information Theory (the HB proposal).

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

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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 →