Tag Archives: OKC

Welcome the new director!

After eight years of existence, the Oskar Klein Centre of cosmoparticle physics ranks among the most dynamic and successful European research centres in the field. We are proud for having hosted outstanding postdocs and recruited world leading researchers.
Today, a new chapter in the OKC success story is about to unfold: it is time for me to pass on the baton to Hiranya Peiris, as she starts her journey as the new director of the centre.

Foto credits Max Alexander
Foto credits Max Alexander

Hiranya Peiris is an internationally recognised cosmologist working in both theory and observation. She studied at Cambridge University and got her PhD from Princeton University in 2003. She was a Hubble Fellow at the University of Chicago from 2004–2007. She then moved back to Cambridge as a STFC Halliday Fellow, and began a faculty position at UCL in 2009, where she is now Professor of Astrophysics. Her research aims to test fundamental physics using large cosmological datasets, including the cosmic microwave background and galaxy surveys, using an interdisciplinary approach combining observations, theoretical physics, and advanced statistical methods. In addition to supporting the many existing strengths of the OKC in cosmoparticle physics, she hopes to create new initiatives in observational cosmology, transient and gravitational wave astronomy, and the interdisciplinary interface with data science.

On behalf of all of us at OKC and the Department of Physics at SU, I want to express Hiranya our best wishes for the future.

I hope she will enjoy the friendly and creative atmosphere in Stockholm. Hiranya is well suited for leading the centre to new scientific heights. Welcome!

– Ariel Goobar, outgoing director

As we turn the page to a new year

As we close the book on 2015 we can again look back at a year of exciting science and great accomplishments by members of the Oskar Klein Centre for Cosmoparticle Physics.

As in previous years, OKCers feature very prominently in the list of the most cited astrophysics and cosmology papers led by Swedish scientists published during the year. The list was compiled by Robert Cumming in populärastronomi and appears in today’s issue.

In fact, half of top-10 2015 publications originate in our centre, starting with a Fermi collaboration search for gamma-rays from dwarf galaxies, led by Brandon Anderson. Together with a similar study led by Christian Farnier based on observations from the H.E.S.S. array (place #4), gamma-rays are used as tracers for annihilation of dark matter particles. Unfortunately, the detection of dark matter particles remain elusive but the hunt goes on, now also directly using the Xenon 1T detector.
Addressing the challenges posed by the dark sector, including both dark matter and dark energy, has become a very active area of theoretical and phenomenological research at OKC. The cosmological implications of the bimetric Hassan-Rosen theory of gravity, an alternative to Einstein’s theory of gravity including a massive graviton, has been scrutinized in a paper led by Jonas Enander. This paper came in second in citations for 2015. The other OKC contributions to the top-10 list involve two studies of SN2014J, the nearest Type Ia supernova in many decades, and an essential laboratory for our understanding of the precision reach of the use of SNe Ia as distance indicators in cosmology in our quest to understand the nature of dark energy. In one of the studies that I led together with Markus Kromer, we explored the onset of the explosion with aunique data set allowing us to probe what powers the very first moments of the optical lightcurve. In another paper, led by Peter Lundqvist and Anders Nyholm, evidence showing that both SN2014J and SN2011fe are likely the result of a merger of two white dwarfs is presented. In a short time, there has been a paradigm shift in what we think is the most common channel triggering these powerful explosions used in cosmology. These are exciting times in the field!

Just before the end of 2015, we were also intrigued by the recent developments in particle physics. The two major LHC experiments, ATLAS (with OKC participation) and CMS, presented the results from the second run of 13 TeV proton-proton collisions. Although no signal reached the magical threshold of 5 standard deviations required to claim discovery, there is an intriguing accumulation of photon-pairs of what could be hinting at a decay of a 750 GeV scalar boson. If confirmed, this would be the sign of long awaited new physics!

Looking forward to a Great New Year at the Oskar Klein Centre!

New times for the Oskar Klein Centre

image003Dear all,

As you have noticed by following the OKC blog, our success is continuing. We had an international mid-term review in the beginning of the year, and we came through with flying colours. Just a couple of quotes from that report of the Swedish Research Council (VR):

”Research on some of the most profound mysteries of the universe, such as the nature of dark matter, is being conducted in OKC at the highest international levels…”

“The research is of excellent quality, as can be seen from publications and citations, but even more by looking at the published papers…”

“OKC is actively involved in several very high-profile international experiments or facilities… The most prominent is ATLAS, one of the two experiments which led to the discovery of the Higgs boson at the CERN LHC… “

“OKC has had hardware participation in, and is leading the search for, indirect detection of dark matter…”

“A 2011 OKC paper [by Fawad Hassan and OKC-Fellow Rachel Rosen] provided a consistent formulation of the “bimetric theory”, as an alternative to Einstein’s theory of gravitation…”

This was great words for us to read – and indeed they meant that we can continue in OKC with unchanged budget 5 more years.  This was soon followed by other positive news: Katie Freese was chosen new NORDITA Director, and also obtained a large VR 10-year excellence grant to perform her  research here at Stockholm University in the OKC environment. Then in October Jan Conrad received a substantial grant from the Wallenberg Foundation to enter the world-leading XENON experiment in Gran Sasso, and soon after that word came about OKC’s Ariel Goobar being honoured by the “Breakthrough Prize”  for his role in the Nobel Prize winning SCP project. Finally, a few weeks ago, OKC got one more Wallenberg Academy Fellow – congratulations to Matthew Hayes of the Astronomy Department!

As some of you know, I will now step down as Director for OKC, and will be Dean of the Mathematics and Physics Section of the Science Faculty of Stockholm University as from January 1st 2015. Ariel Goobar will take the responsibility to lead the OKC until a new Director arrives (there is still time to apply to the announced Chair at Stockholm University which has this as a first task).

I want to finish this blog by thanking all my colleagues and friends at the OKC who have helped making this such an enjoyable, exciting and successful 6 years. I am sure that the next leg of this wonderful OKC journey will be at least as exciting as the first part.

I wish you all Happy Holidays and a great New Year!



Another interesting and very successful year of the Oskar Klein Centre

Francois Englert just before Nobel lecture in Stockholm University’s Aula Magna. Photo: L. Bergström.

Hello and Happy Holidays to all friends of the OKC

As the year 2013 is now nearing its end, it is time to recapitulate the main events of the year from the OKC perspective. If I temporarily put on my Nobel hat (being the scientific secretary of the Nobel Committee for Physics) the main event from the Stockholm horizon is without doubt the Nobel Prize to Francois Englert and Peter Higgs for their almost 50-year old prediction from the early 1960’s that was so spectacularly confirmed by the ATLAS and CMS experiments at CERN’s LHC accelerator last year. Hats off for Englert and Higgs, and also for the many clever and hard-working experimentalists, in particular the ATLAS people of OKC such as Jonas Strandberg, who has been directly involved in the discovery of the Higgs particle in ATLAS. Of course we now look forward to the energy upgrade of LHC, which will increase the chances substantially to find the much awaited effects beyond the Standard Model that, hopefully, could give an indication of what the dark matter may consist of. At the Oskar Klein Centre we also have been searching in gamma-ray, positron and neutrino signals, without positive results (yet), but producing some of the best limits.

Peter Higgs signing the Nobel Poster (prepared with the help of OKC's Sara Strandberg and Oscar Stål). Photo: L. Bergström.

The OKC has now been in existence for 5 years, and we will soon encounter the international mid-review panel of the Science Council (VR) of Sweden. By September 1st we had to submit our self-assessment report, containing a detailed description This meant a lot of work for me and the OKC Steering Group: Christophe Clement, Jan Conrad, Claes Fransson, Ariel Goobar, Klas Hultquist, Garrelt Mellema, Mark Pearce, Sara Strandberg and Göran Östlin (and of course our great communications manager, Serena Nobili). We hope that we managed to convey our great enthusiasm for the scientific outcome of the OKC during its first 5 years, and that the evaluation committee will agree that it has been a great success. In fact, when we meet them January 30th, we will have quite a number of recent sucesses to report:

  • A generous grant of SEK 32 million from the K&A Wallenberg Foundation was given to groups in OKC (with J. Sollerman as PI) for contributing to the Zwicky Transient Facility (with S. Kulkarni of Caltech leading the team).
  • OKC Steering Group member Sara Strandberg has obtained both a young researcher’s grant from the VR and a Wallenberg Academy Fellow (WAF) grant – both in very strong competition.
  • Jan Conrad (also OKC Steering Group member) has in addition to his previous WAF grant also been given one of the new excellent junior investigator grants from VR. Congratulations to Sara and Jan!
  • The IceCube experiment has finally detected high-energy (PeV) cosmological neutrino events, with a surprising energy distribution.  This was declared the discovery of the year of the Physics World magazine. Congratulations to the OKC IceCube group (Chad Finley, P.O. Hulth, Klas Hultquist & al.) and the Uppsala group (with present IceCube spokesperson Olga Botner and her colleagues)!
  • The Fermi satellite project with large OKC contribution continues to make important discoveries. One concerns the discovery of a gamma-ray spectrum of two supernova remnants which clearly shows a hadronic origin (from decays of neutral pions), and thus is a proof that these sources accelerate protons, and are thus the long-sought-for sources of the Galactic cosmic rays. This was one of the runner-ups for the discovery of the year of Science magazine.

To conclude, with all the interesting science produced by OKC during its first half-life, one may only anticipate with great expectations what will come out of the second half!

Merry Holidays and a Happy New Year to all in the OKC research environment and all our followers!


Interview with Timur Delahaye

Timur Delahaye is one of the OKC fellows working at the Cosmology, Particle astrophysics and String theory group (CoPS) since this summer. let’s get to know him better.

Where have you studied or did research before coming to the OKC?
I did my undergraduate studies at École Polytechnique near Paris. I then completed my Mas ter degree at the theoretical physics department of École Normale Supérieure in Lyon and did my Ph.D. with the IDAPP (International Doctorate on AstroParticle Physics) program both in Annecy and Turin under the supervision of Pierre Salati and Nicolao Fornengo. Autumn 2010, I moved to Madrid to do my first post-doc at the Instituto de Física Teórica (IFT) of the Universidad Autónoma where I stayed for two years. Last year I worked at the Laboratoire d’Annecy-le-Vieux de Physique Théorique (LAPTh) and the Institut d’Astrophysique de Paris (IAP).

What is your field of research?
I work in modelling the propagation of Galactic Cosmic Rays and Dark Matter indirect detection. Cosmic rays are high energy particle that are accelerated by exploding stars, by high magnetised stars called pulsars, and maybe by the annihilation or decay of Dark Matter particles. Even though cosmic rays have been discovered more than 100 years ago we still do not understand precisely where they come from nor how they propagate in the interstellar medium. In spite of being a rather young science, cosmic ray physics are is a wonderful way to look at things in the sky that do not emit light and cannot be probed by usual astronomy.

What I really enjoy in this field is that it is at the intersection of cosmology, astrophysics and particle physics and allows to interact with many people from very different fields.
Continue reading Interview with Timur Delahaye

End of a good Oskar Klein Centre year

This year has been very interesting for the OKC. The highlight was of course the Nobel Prize for Saul Perlmutter, Brian Schmidt and Adam Riess.

The Nobel banquet, waiting for the Laureates and Royalties to arrive. (Photo: Lars Bergström)

The half-day December 12th immediately following the Prize ceremony, organized by Ariel Goobar and Jesper Sollerman, was a great success. I could not be present, unfortunately, but I can recommend the video from the very memorable colloquium session, at http://videos.albanova.se/colloquia/2011/ – it is well worth watching, as is the colloquium the day after on global warming by Rich Muller (who was one of the forefathers of the Supernova Cosmology Project). Continue reading End of a good Oskar Klein Centre year

New activity starting at OKC: The Monthly Science Pub!

A new academic year has started, and it is time also for the Oskar Klein Centre to get up to full steam again. As the OKC is to some extent a rather large, loosely connected set of people and groups, we feel in the Steering Group that there is a need to better understand what everybody is doing, and to encourage collaboration. To achieve this, under relaxed conditions, we will let the various Working Groups of OKC take turns in arranging an afternoon (at the end of each month) where a very basic introduction to the main activities of the group will be given, followed by discussions and ending with a pub. This will be both useful and enjoyable events!

What is the perfect size for a research group?

If you are thinking about your research group and are wondering on whether to include more people you better read this.

Ralph Kenna from the University of Coventry and Bertrand Berche from the University of Nancy (France) have analyzed the correlation between quality and research group size for different areas, based on data collected for the UK’s 2008 Research Assessment Exercise (RAE). Their findings are very interesting. While one could think that more people would get better results together, it seems that this is not true indefinitely. There is a linear relation between group size and quality of the scientific results, and they correlate until reaching a breaking point, which is different for different areas. In experimental physics the breaking point is 25 people while in theoretical physics is 13. Once reached the breaking point, if you keep increasing the group size, quality does not increase anymore, and the trend flatten out.
The analysis shows that there is also a lower critical mass calculated as a minimum of 2 persons for theorists and 13 for experimentalists to guarantee an healthy scientific outcome.

This is probably something to keep in mind when deciding about future strategies. If you are interested in reading the original article you can find it here: http://arxiv.org/abs/1006.0928

The OKC Day

This spring’s Oskar Klein Centre day took place in beautiful surroundings yesterday (Monday, May 30th), at Villa Källhagen – a nice conference centre in Djurgården near the water. As is now customary in these general OKC meetings, first a summary of the activities of the working groups was done, with slide presentations by Jonas Enander (Dark Energy), Christoph Clement (Dark Matter), Elena Moretti and Josefin Larsson (Extreme Objects) and Rachel Rosen (Fundamental Theory). Although the working group for Structure formation was left without slides due to a late cancellation, Lucia Gaita and Kanan Datta made a very good, unprepared presentation of their activities.

After this very good summary of achievements during the last semester, it was time for a new activity  – brainstorming – on the initiative of OKC’s Communication Manager, Serena Nobili. We had two topics to discuss very freely about Continue reading The OKC Day