NBIA News 2014

The largest computer cluster dedicated to astrophysics in Scandinavia

Oliver Gressel receives ERC Starting Grant

Research by Sami Dib highlighted in Science

A question that has troubled astrophysicists for more than half a century is whether the mass distribution of stars at their birth is identical among stellar clusters or whether variations in this distribution can be detected.

In a recent study, NBIA scientist Sami Dib used Bayesian statistics techniques in order to characterize the mass distribution of eight, young (< 2 million years) stellar clusters in our galaxy. Surprisingly, the analysis indicated that the parameters that describe the distributions of these clusters do not resemble each other, thus shattering the long-held concept of a universal function describing these distributions. In addition to advocating the importance of using robust statistical methods for the analysis, these results also highlight the need for advanced theories of star formation that can account for the variations.

Jacob Bourjaily joins the NBIA

Jacob Bourjaily, who received his PhD-degree from Princeton University in 2011 and who has since then been Junior Fellow in the Harvard Society of Fellows at Harvard University, is now starting as Assistant Professor at the NBIA. Jacob works on a radically new way of computing scattering amplitudes in quantum field theory. The method, which Jacob is developing together with his former adviser Nima Arkani-Hamed at the Institute for Advanced Study in Princeton, and others, is also the subject of a scientific monograph that Jacob has been co-authoring and which will be published by Cambridge University Press later this year.

Villum Young Investigator Grant to Michael Kastoryano

This month, quantum information theorist Michael Kastoryano joins the NBIA on a Villum Young Investigator grant. Michael earned his PhD-degree at the Niels Bohr Institute in 2011, and has since held an Alexander von Humboldt post-doctoral appointment at the Dahlem Center at the Freie University Berlin. His arrival at the NBIA coincides with an upswing in activity in theoretical quantum information sciences at the university of Copenhagen, following the appointments of Mark Rudner (NBIA) and Matthias Christandl (Math). Michael will be building a quantum information group at the NBIA as part of a larger operation to make Copenhagen a pole of excellence in this dynamic field of research. Michael Kastoryano works mainly on quantum information motivated questions in many body physics. Recently his focus has shifted towards topologically ordered systems and topological computation.

Michael Trott is new Associate Professor at the NBIA

This month, Michael Trott joins the NBIA and Discovery Center as new Associate Professor in theoretical particle physics. Michael earned his PhD-degree at the University of Toronto, and has since held post-doctoral appointments at the University of California in San Diego and the Perimeter Institute. He is presently Fellow at the Theory Group of CERN. Michael Trott works mainly on the phenomenology of particle physics and is one of the leading scientists in understanding how physics beyond the Standard Model can represent itself through the Higgs sector.

The NBIA signs MoU with the Weizmann Institute of Science

The NBIA Director and the President of the Weizmann Institute of Science Prof. Daniel Zajfman have last week signed a Memorandum of Understanding between the NBIA and the Weizmann Institute of Science in Israel. The agreement shall help in further strengthening the scientific links between the two institutions and includes collaboration in higher education and scientific research. An important aspect of the agreement concerns the exchange of scientists and scholars in connection with scientific collaboration, seminars and joint workshops. A first joint workshop will be held in Copenhagen in 2015.

Research inspired by Ciaran Williams and collaborators makes front-page news at CERN

With the discovery of the Higgs particle at CERN it is now crucial to determine with high accuracy the precise properties of this new particle, and see, in particular, if it really is the Higgs particle predicted by the Standard Model. Measuring its width to high accuracy is absolutely essential. Perhaps surprisingly to many, the Standard Model prediction is that it should be very narrow, around just 4 MeV (this should be compared to, for example, its mass which has been found to be near 125 GeV). Inspired by theoretical advances by NBIA Assistant Professor Ciaran Williams and collaborators John Campbell and Keith Ellis from Fermilab, the limits of the Higgs particle has now been reduced by a factor of 200 from its original first rough bound of around 3 GeV. This remarkable development, which tests the Standard Model at a very subtle level, was front-page news at CERN last week when it reported on new analysis based on the CMS experiment.

Chris Pethick's recent paper is "Editor's Suggestion" at Physics Review Letters

Dmitry Kobyakov, a visitor to NBIA and a graduate student at the University of Umeå (Sweden), and Prof. Chris Pethick have just had a paper accepted in Physical Review Letters. The work, highlighted as an "Editors' Suggestion", concerns neutron stars, objects whose interiors are similar to a giant atomic nucleus weighing as much as our sun. In the outer parts of these stars (the so-called ``crust'') matter closely resembles a terrestrial solid. However, above a density of one-thousandth of the density inside atomic nuclei there is an important difference, because the space between nuclei is permeated by a fluid of neutrons. The traditional view of the structure of matter at these densities is that its electronic and crystal structure are rather simple. The authors argue that the presence of the neutrons can change this picture because the neutrons give rise to an attraction between nuclei that is strong enough to change the crystal structure. The properties of ordinary materials such as steels depend sensitively on the existence of a number of different crystal structures, and the possibility of different crystal structures in neutron star means that their properties could be much richer than previously suspected. The new insight into neutron stars has a number of implications for interpreting observed signals from neutron stars seen in satellite observations.