Rafael Porto, newcomer to DESY’s new astro-particle physics division and based in Hamburg, does not only bring the promise of an exciting research topics, he also brings one of the most endowed and sought-after grants in Europe. In 2018 the scientist secured an ERC consolidating grant of two million Euros over a period of five years to continue his work in gravitational wave physics, using novel methods that he and collaborators have pioneered.

 

Under the heading “Precision Gravity: From LHC to LISA”, Porto’s multidisciplinary group, consisting of a number of postdocs and PhD students with expertise in gravity and particle physics, will work together under the umbrella of gravitational wave science in order to “redefine the frontiers of analytic understanding in gravity”, according to Porto. 

Gravitational waves are “ripples” travelling through space and time. We are now able to observe them thanks to the LIGO/VIRGO experiments. These gravitational waves are very feeble, but those produce by colossal events such as the collision of black holes or neutron stars can be detected by very precise laser interferometers such as the ones used by the LIGO/VIRGO collaboration. The gravitational waves, which propagate to us, carry information about matter under unique conditions and ultimately gravity itself. The feasibility of direct detection has enabled a new era of multimessenger astronomy, which uses different observations, for example light or neutrinos, etc., to unravel the source’s properties, thus adding another angle to our understanding the fabric of the Universe.

Christian Stegmann, DESY’s Director in charge of Astroparticle Physics, says: “Gravitational wave science will become a truly interdisciplinary subject, also thanks to Rafael and his ground-breaking work. We are immensely proud that he won this prestigious ERC grant and joined our team. When so many different communities like astrophysics, cosmology, general relativity, theory and particle physics throw their heads together, we can look forward to exciting new results from gravitational wave observations in the years to come.”

A particle physicist by training, and originally from Uruguay, Rafael Porto graduated with a PhD in physics from Carnegie Mellon University in the US in 2007. His thesis work already introduced new ideas and results in gravitational physics. In particular, Porto solved for the first time (in collaboration with his PhD advisor, Prof. Rothstein) the dynamics of binary black holes due to nonlinear spin effects in the weak-field regime, a problem that daunted scientists for many decades. He then went on to post-doctoral positions at the Kavli Institute for Theoretical Physics in Santa Barbara, and the Institute for Advanced Study in Princeton, where he also worked on new approaches in cosmology. Before coming to DESY, he was a faculty member at the ICTP South American Institute for Fundamental Research in Sao Paulo.

Porto’s work focuses on using a new framework — dubbed the effective field theory approach — to study the two-body problem in gravity. Unlike the problem of motion in Newton’s theory, which does not feature gravitational wave radiation, the nonlinear character of Einstein’s equations makes finding accurate solutions for binary systems a real tour-de-force. For the late stages, numerical methods are needed, however, for many sources of interest the majority of the gravitational wave signal is produced during the earlier ‘inspiral’ regime, which may be understood analytically. This is the regime where Porto and collaborators have opened a new way to look at the problem, using tools that were originally developed for particle physics to study the strong force at colliders. The work of Porto and collaborators has played a key role in modelling spinning binary systems in general relativity using analytic methods. This is a crucial step towards constructing accurate gravitational wave templates, which are then used to characterise the nature of the sources and search for new physics.

In particle physics, precise predictions for the theory of the building blocks of matter — known as Standard Model of Particle Physics — are used to search for new phenomena lurking in the many products of particle colliders. Using similar ideas and tools, Porto’s work in general relativity could likewise be used to look for new physics in the data from gravitational wave events.“Ambitiously, we aim to go beyond the current computational paradigm in general relativity, with powerful tools which have been crucial for new-physics searches at the Large Hadron Collider”, Porto says. 

So what kind of new physics can be expected from gravitational wave data? Once the gravitational wave observatories like LIGO/VIRGO have reached their design sensitivity, scientists may be able to search for new ultralight particles with the help of gravitational wave signals, study the properties of black holes as well as neutron stars. “We want to bring together different and seemingly unrelated tools and researchers focusing in the emerging new field of gravitational wave physics, ranging from field-theoretical methods, analytic and numerical relativity, astrophysics and data analysis, to make use of all possible routes to learn about the universe,” says Porto. “As a byproduct, we will probe gravity itself, to learn whether “Einstein’s theory withstands precision scrutiny.”

The European Research Council ERC hands out these grants to researchers of any nationality or research field with seven to twelve years of experience since completion of their PhD and “a scientific track record showing great promise and an excellent research proposal.” Porto is one of 291 scientists to receive the grant over all disciplines (in 2018), and one of 12 in the PE2 division which encompasses gravity and particle physics, being one of only two theorists awarded in 2018. Porto’s grant will start in June 2019.