Press release – April 27th, 2015
Crucial theoreticalbreakthrough
todetect gravitationalwaves
Combining an analyticalapproachwithnumericalmethods, an international team of physicists has obtained an accuratetheoretical description of the gravitationalwavesemittedduring the last orbits of a binarysystem made of two neutron stars. This new resultcould have a significantastronomicalimpact inallowing the detectors LIGO and Virgo to observe thesewaves in the next few years.
Gravitationalwaves: a keyprediction of Einstein’sTheory of General Relativity
In 1915, Albert Einstein completedhistheory of General Relativity, withinwhichSpaceissimilar to an elastic mediumdeformed by matter. The followingyear, he
showedthatthisdeformationpropagatesat the speed of light, in the form of waves, called «gravitationalwaves». A system made of two neutron stars, orbitingaroundeachother,generatesgravitationalwaves.
Undetectedwavesso far
The gravitationalwavesemitted, more than 600 millions of light yearsaway, by a system of two
neutron stars arrive on Earthwithsuch a small amplitude (10-22)thatitis of paramount importance to have at hand a veryprecisetheoretical model of theirshape to be able to extractthemout of the detector’s noise. Nowthat the ground-basedinterferometers LIGO (USA) and Virgo (French-Italian) are coming back online at an improvedsensitivity, sucha theoreticaladvancemayallowone to finallydetect the gravitationalwavesemittedduring the coalescence of a system of two neutron stars.
A team of Europeanscientistswithcomplementaryskills
SebastianoBernuzzi (CalTech, Parma University) and Tim Dietrich (Jena University) are twoyoung experts in numericallysolvingEinstein’sequations by means of supercomputers.Thibault Damour et Alessandro Nagar(Institut des Hautes Études Scientifiques) have developed an analytical description (called Effective One Body method) of the orbital motion and of the gravitationalwaveemission of binarysystems made of dead stars (black holes or neutron stars). By comparing state of the art numerical simulations of coalescing neutron stars binaries to their best availableanalyticrepresentations, the team has succeeded in reliablydescribing the gravitationalwave signal up to the moment when the two neutron stars becomeso closethattheymergetogether. This resultjustappeared in the prestigious journal PhysicalReviewLetters(PRL 114, 161103, 23 avril 2015).
Institut des Hautes Études Scientifiques (IHES)
IHES is a privateresearch centre dedicated to mathematics, theoreticalphysics and relatedfields. The Institute has a restrictednumber of permanent members, eithermathematicians or theoreticalphysicists, and welcomes about 200 visitors per year, which come from all over the world for researchstays. Researchfreedom, independence and interdisciplinarity are the foundingpillars of IHES.
Thibault Damour is an IHES permanent professorsince 1989; Alessandro Nagar, holder of theBeverly et Raymond SacklerVisitingChair in TheoreticalPhysics and Cosmology, collaborateswithhimat IHES since 2007.
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