Heidelberg Institute for Theoretical Studies

Heidelberg, Germany

Heidelberg Institute for Theoretical Studies

Heidelberg, Germany
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News Article | May 10, 2017
Site: www.eurekalert.org

What distinguishes the HLF from standard scientific conferences is the unique informal atmosphere that inspires a blend of acute scientific discussions and social interactions among the participants. Lectures, workshops and panel discussions embolden scientifically driven debate, while various social events encourage the participants to pursue their discourse outside the lecture halls and to get to know each other. Embedded once again into the program is the Hot Topic session, which is especially interesting for the media. At the 4th HLF in 2016, the focus revolved around Artificial Intelligence (AI) and a panel of experts addressed the costs and benefits created by developments brought on by AI. The theme for the session in 2017 at the 5th HLF will delve into quantum computing, more information will be available soon on the HLF homepage: heidelberg-laureate-forum.org The Heidelberg Laureate Forum Foundation offers 15 travel grants of up to 3,000 euros to enable journalists to report on this compelling networking event for the pinnacle in computer science and mathematics. Grants cover the travel costs as well as board and accommodation during the stay in Heidelberg (starting with a media get-together on the evening of September 23). Until May 31, 2017, journalists from all over the world are invited to apply, irrespective of their media affiliation (print, TV, online, radio). The applications must include the following: a short CV, three samples of work (indicating respective medium), a synopsis of publications to date (indicating respective medium), planned contributions regarding the HLF as well as a preliminary travel itinerary including estimated costs. Please send your travel grant applications to: media@heidelberg-laureate-forum.org All journalists who wish to cover the 5th HLF are requested to register using the following link: (regardless of whether or not they choose to apply for a travel grant) https:/ The Heidelberg Laureate Forum Foundation (HLFF) annually organizes the Heidelberg Laureate Forum (HLF), which is a networking event for mathematicians and computer scientists from all over the world. The 5th Heidelberg Laureate Forum will take place from September 24-29, 2017. The HLFF was established and is funded by the German foundation Klaus Tschira Stiftung (KTS), which promotes natural sciences, mathematics and computer science. The Scientific Partners of the HLFF are the Heidelberg Institute for Theoretical Studies (HITS) and Heidelberg University. The HLF is strongly supported by the award-granting institutions, the Association for Computing Machinery (ACM), the International Mathematical Union (IMU), and the Norwegian Academy of Science and Letters (DNVA).


Stamatakis A.,Heidelberg Institute for Theoretical Studies | Stamatakis A.,Karlsruhe Institute of Technology
Bioinformatics | Year: 2014

Motivation: Phylogenies are increasingly used in all fields of medical and biological research. Moreover, because of the next-generation sequencing revolution, datasets used for conducting phylogenetic analyses grow at an unprecedented pace. RAxML (Randomized Axelerated Maximum Likelihood) is a popular program for phylogenetic analyses of large datasets under maximum likelihood. Since the last RAxML paper in 2006, it has been continuously maintained and extended to accommodate the increasingly growing input datasets and to serve the needs of the user community. Results: I present some of the most notable new features and extensions of RAxML, such as a substantial extension of substitution models and supported data types, the introduction of SSE3, AVX and AVX2 vector intrinsics, techniques for reducing the memory requirements of the code and a plethora of operations for conducting postanalyses on sets of trees. In addition, an up-to-date 50-page user manual covering all new RAxML options is available. © The Author 2013. Published by Oxford University Press.


News Article | November 15, 2016
Site: www.eurekalert.org

The HLF offers all accepted young researchers the great opportunity to personally interact with the laureates of the most prestigious prizes in the fields of mathematics and computer science. The 5th HLF will take place from September 24 to 29, 2017 (with young researcher registration on September 23). The application period for the 5th HLF has begun and runs from November 14, 2016 until February 14, 2017. Young researchers at all phases of their careers (undergrad, PhD or postdoc) are encouraged to complete and submit their applications by February 14 (midnight at the dateline) via the following link: This prominent, versatile event combines scientific, social and outreach activities in an informal atmosphere, fueled by comprehensive exchange and scientific inspiration. Laureate lectures, young researcher workshops and a structure welcoming unfettered discussions are the elements that compose the Forum's platform. The 4th HLF attracted young researchers from over 50 nations to participate. Over the course of the week-long HLF, young researchers will be given the exclusive possibility to profoundly connect with their scientific role models and find out how the laureates made it to the top of their fields. As described by a young researcher at the 4th HLF, "Attending the 4th Heidelberg Laureate Forum has been a profoundly enriching experience. I was also very impressed with how well organized the Forum was." All completed and submitted applications are meticulously reviewed by an international committee of expert mathematicians and computer scientists to ensure that only the most qualified candidates are invited. There are 100 spaces available for each discipline of mathematics and computer science. All applicants will be notified by the end of April 2017 whether or not they will be invited. For questions regarding requirements and the application process, please contact Young Researchers Relations at: yr@heidelberg-laureate-forum.org For more information, please visit: http://www. The Heidelberg Laureate Forum Foundation (HLFF) annually organizes the Heidelberg Laureate Forum (HLF), which is a networking event for mathematicians and computer scientists from all over the world. The 5th Heidelberg Laureate Forum will take place from September 24 to 29, 2017. The HLFF was established and is funded by the German foundation the Klaus Tschira Stiftung (KTS), which promotes natural sciences, mathematics and computer science. The Scientific Partners of the HLFF are the Heidelberg Institute for Theoretical Studies (HITS) and Heidelberg University. The HLF is strongly supported by the award-granting institutions, the Association for Computing Machinery (ACM), the International Mathematical Union (IMU), and the Norwegian Academy of Science and Letters (DNVA).


News Article | October 26, 2016
Site: www.eurekalert.org

The HLF offers all accepted young researchers the great opportunity to personally interact with the laureates of the most prestigious prizes in the fields of mathematics and computer science. The 5th HLF will take place from September 24 to 29, 2017 (with young researcher registration on September 23). The application period for the 5th HLF runs from November 14, 2016 until February 14, 2017. Young researchers at all phases of their careers (undergrad, PhD or postdoc) are encouraged to complete and submit their applications by February 14 (midnight at the dateline) via the following link: http://application. This prominent, versatile event combines scientific, social and outreach activities in an informal atmosphere, fueled by comprehensive exchange and scientific inspiration. Laureate lectures, young researcher workshops and a structure welcoming unfettered discussions are the elements that compose the Forum's platform. The 4th HLF attracted young researchers from over 50 nations to participate. Over the course of the week-long HLF, young researchers will be given the exclusive possibility to profoundly connect with their scientific role models and find out how the laureates made it to the top of their fields. As described by a young researcher at the 4th HLF, "Attending the 4th Heidelberg Laureate Forum has been a profoundly enriching experience. I was also very impressed with how well organized the Forum was." All completed and submitted applications are meticulously reviewed by an international committee of expert mathematicians and computer scientists to ensure that only the most qualified candidates are invited. There are 100 spaces available for each discipline of mathematics and computer science. All applicants will be notified by the end of April 2017 whether or not they will be invited. For questions regarding requirements and the application process, please contact Young Researchers Relations at: yr@heidelberg-laureate-forum.org For more information, please visit: http://www. The Heidelberg Laureate Forum Foundation (HLFF) annually organizes the Heidelberg Laureate Forum (HLF), which is a networking event for mathematicians and computer scientists from all over the world. The 5th Heidelberg Laureate Forum will take place from September 24 to 29, 2017. The HLFF was established and is funded by the German foundation the Klaus Tschira Stiftung (KTS), which promotes natural sciences, mathematics and computer science. The Scientific Partners of the HLFF are the Heidelberg Institute for Theoretical Studies (HITS) and Heidelberg University. The HLF is strongly supported by the award-granting institutions, the Association for Computing Machinery (ACM), the International Mathematical Union (IMU), and the Norwegian Academy of Science and Letters (DNVA).


News Article | November 14, 2016
Site: www.eurekalert.org

The Heidelberg Laureate Forum is an annual networking event that unites the laureates of computer science and mathematics with brilliant, precisely selected young researchers from around the globe for a week of intensive exchange. All recipients of the ACM Prize in Computing will be cordially invited to attend the 5th Heidelberg Laureate Forum next September 24-29, to profoundly interact with fellow laureates and young researchers in computer science and mathematics. The history of the ACM Prize in Computing: Ten years ago, the ACM established the Infosys Foundation Award in Computing Science to "recognize personal contributions by young scientists and system developers to a contemporary innovation that, through its depth, fundamental impact and broad implications, exemplifies the greatest achievements in the discipline." The prize was commonly referred to as the Infosys Award and was accompanied by funding from Infosys. Due to the award's eminence, it has been renamed the ACM Prize in Computing and funding from the Infosys Ltd. has been raised to $250,000. Significant developments in the wake of the 4th HLF, from the HLFF being joined by two substantial scientific partners to the HLF Laureates expanding with the inclusion of the ACM Prize in Computing recipients, have sparked excitement and heightened anticipation for the 5th Heidelberg Laureate Forum. More information regarding the ACM Prize in Computing can be found here: http://awards. For further information pertaining to the Heidelberg Laureate Forum, please visit the homepage: http://www. The Heidelberg Laureate Forum Foundation (HLFF) annually organizes the Heidelberg Laureate Forum (HLF), which is a networking event for mathematicians and computer scientists from all over the world. The 5th Heidelberg Laureate Forum will take place from September 24 to 29, 2017. The HLFF was established and is funded by the German foundation the Klaus Tschira Stiftung (KTS), which promotes natural sciences, mathematics and computer science. The Scientific Partners of the HLFF are the Heidelberg Institute for Theoretical Studies (HITS) and Heidelberg University. The HLF is strongly supported by the award-granting institutions, the Association for Computing Machinery (ACM), the International Mathematical Union (IMU), and the Norwegian Academy of Science and Letters (DNVA). With this press release, we would like to extend an invitation to attend and report on the 5th Heidelberg Laureate Forum.


News Article | February 16, 2017
Site: www.eurekalert.org

Lectures, workshops and panel discussions embolden scientifically driven debate, while various social events encourage the participants to pursue their discourse outside the lecture halls and to get to know each other. Embedded once again into the program is the Hot Topic session, which is especially interesting for the media. At the 4th HLF in 2016, the focus revolved around Artificial Intelligence (AI) and a panel of experts addressed the costs and benefits created by developments brought on by AI. The theme for the session in 2017 at the 5th HLF will delve into quantum computing, more information will be available soon on the HLF homepage: heidelberg-laureate-forum.org The Heidelberg Laureate Forum Foundation (HLFF) offers 15 travel grants of up to 3,000 euros to enable journalists to report on this compelling networking event for the pinnacle in computer science and mathematics. Grants cover the travel costs as well as board and accommodation during the stay in Heidelberg (starting with a media get-together on the evening of September 23). Until May 15, 2017, journalists from all over the world are invited to apply, irrespective of their media affiliation (print, TV, online, radio). The applications must include the following: a short CV, three samples of work (indicating respective medium), a synopsis of publications to date (indicating respective medium), planned contributions regarding the HLF as well as a preliminary travel itinerary including estimated costs. Please send your travel grant applications to: media@heidelberg-laureate-forum.org All journalists who wish to cover the 5th HLF are requested to register using the following link: (regardless of whether or not they choose to apply for a travel grant) https:/ The Heidelberg Laureate Forum Foundation (HLFF) annually organizes the Heidelberg Laureate Forum (HLF), which is a networking event for mathematicians and computer scientists from all over the world. The 5th Heidelberg Laureate Forum will take place from September 24-29, 2017. The HLFF was established and is funded by the German foundation Klaus Tschira Stiftung (KTS), which promotes natural sciences, mathematics and computer science. The Scientific Partners of the HLFF are the Heidelberg Institute for Theoretical Studies (HITS) and Heidelberg University. The HLF is strongly supported by the award-granting institutions, the Association for Computing Machinery (ACM), the International Mathematical Union (IMU), and the Norwegian Academy of Science and Letters (DNVA).


Schefzik R.,Heidelberg Institute for Theoretical Studies
Quarterly Journal of the Royal Meteorological Society | Year: 2016

State-of-the-art weather forecasts usually rely on ensemble prediction systems, accounting for the different sources of uncertainty. As ensembles are typically uncalibrated, they should get statistically postprocessed. Several multivariate ensemble postprocessing techniques that additionally consider spatial, inter-variable and/or temporal dependences have been developed. These can be roughly divided into two groups. The first group comprises parametric, mainly low-dimensional, approaches that are tailored to specific settings. The second group involves non-parametric reordering methods that impose a specific dependence template on univariately postprocessed forecasts and are suitable in any dimension. In this article, these different strategies are combined, with the aim of exploiting the benefits of both concepts. Specifically, a high-dimensional postprocessing problem is divided into multiple low-dimensional instances, each of which is postprocessed via a suitable multivariate parametric method. From each postprocessed low-dimensional distribution, a sample is drawn, which is then reordered according to the corresponding multidimensional rank structure of an appropriately chosen dependence template. In this context, different ranking concepts for multivariate settings are discussed. Finally, all reordered samples are aggregated to obtain the overall postprocessed ensemble. The new approach is applied to ensemble forecasts for temperature and wind speed at several locations from the European Centre for Medium-Range Weather Forecasts, using a recent bivariate ensemble model output statistics postprocessing technique and a reordering based on the raw ensemble forecasts similar to the ensemble copula coupling method. It shows good predictive skill and outperforms reference ensembles. © 2016 Royal Meteorological Society.


Pfrommer C.,Heidelberg Institute for Theoretical Studies
Astrophysical Journal | Year: 2013

Feedback by active galactic nuclei (AGNs) appears to be critical in balancing radiative cooling of the low-entropy gas at the centers of galaxy clusters and in mitigating the star formation of elliptical galaxies. New observations of M87 enable us to put forward a comprehensive model for the physical heating mechanism. Low-frequency radio observations by LOFAR revealed the absence of fossil cosmic-ray (CR) electrons in the radio halo surrounding M87. This puzzle can be resolved by accounting for the CR release from the radio lobes and the subsequent mixing of CRs with the dense ambient intracluster gas, which thermalizes the electrons on a timescale similar to the radio halo age of 40 Myr. Hadronic interactions of similarly injected CR protons with the ambient gas should produce an observable gamma-ray signal in accordance with the steady emission of the low state of M87 detected by Fermi and H.E.S.S. Hence, we normalize the CR population to the gamma-ray emission, which shows the same spectral slope as the CR injection spectrum probed by LOFAR, thereby supporting a common origin. We show that CRs, which stream at the Alfvén velocity with respect to the plasma rest frame, heat the surrounding thermal plasma at a rate that balances that of radiative cooling on average at each radius. However, the resulting global thermal equilibrium is locally unstable and allows for the formation of the observed cooling multi-phase medium through thermal instability. Provided that CR heating balances cooling during the emerging "cooling flow," the collapse of the majority of the gas is halted around 1 keV - in accordance with X-ray data. We show that both the existence of a temperature floor and the similar radial scaling of the heating and cooling rates are generic predictions of the CR heating model. © 2013. The American Astronomical Society. All rights reserved..


Van Den Aarssen L.G.,University of Hamburg | Bringmann T.,University of Hamburg | Pfrommer C.,Heidelberg Institute for Theoretical Studies
Physical Review Letters | Year: 2012

The cold dark matter paradigm describes the large-scale structure of the Universe remarkably well. However, there exists some tension with the observed abundances and internal density structures of both field dwarf galaxies and galactic satellites. Here, we demonstrate that a simple class of dark matter models may offer a viable solution to all of these problems simultaneously. Their key phenomenological properties are velocity-dependent self-interactions mediated by a light vector messenger and thermal production with much later kinetic decoupling than in the standard case. © 2012 American Physical Society.


News Article | February 5, 2016
Site: www.rdmag.com

When we look at the night sky, we see stars as tiny points of light eking out a solitary existence at immense distances from Earth. But appearances are deceptive. More than half the stars we know of have a companion, a second nearby star that can have a major impact on their primary companions. The interplay within these so-called binary star systems is particularly intensive when the two stars involved are going through a phase in which they are surrounded by a common envelope consisting of hydrogen and helium. Compared to the overall time taken by stars to evolve, this phase is extremely short, so astronomers have great difficulty observing and hence understanding it. This is where theoretical models with highly compute-intensive simulations come in. Research into this phenomenon is relevant understanding a number of stellar events such as supernovae. Using new methods, astrophysicists Sebastian Ohlmann, Friedrich Roepke, Ruediger Pakmor, and Volker Springel of the Heidelberg Institute for Theoretical Studies (HITS) have now made a step forward in modeling this phenomenon. As they report in The Astrophysical Journal Letters, the scientists have successfully used simulations to discover dynamic irregularities that occur during the common-envelope phase and are crucial for the subsequent existence of binary star systems. These so-called instabilities change the flow of matter inside the envelope, thus influencing the stars' distance from one another and determining, for example, whether a supernova will ensue and, if so, what kind it will be. The article is the fruit of collaboration between two HITS research groups, the Physics of Stellar Objects (PSO) group and the Theoretical Astrophysics group (TAP). Prof. Volker Springel's Arepo code for hydrodynamic simulations was used and adapted for the modeling. It solves the equations on a moving mesh that follows the mass flow, and thus enhances the accuracy of the model. More than half the stars we know of have evolved in binary star systems. The energy for their luminosity comes from the nuclear fusion of hydrogen at the core of the stars. As soon as the hydrogen fueling the nuclear fusion is exhausted in the heavier of the two stars, the star core shrinks. At the same time, a highly extended stellar envelope evolves, consisting of hydrogen and helium. The star becomes a red giant. As the envelope of the red giant goes on expanding, the companion star draws the envelope to itself via gravity, and part of the envelope flows towards it. In the course of this process the two stars come closer to one another. Finally, the companion star may fall into the envelope of the red giant and both stars are then surrounded by a common envelope. As the core of the red giant and the companion draw closer together, the gravity between them releases energy that passes into the common envelope. As a result, the envelope is ejected and mixes with interstellar matter in the galaxy, leaving behind it a close binary star system consisting of the core of the giant and the companion star. Sebastian Ohlmann of the PSO group explains why this common-envelope phase is important for our understanding of the way various star systems evolve: "Depending on what the system of the common envelope looks like initially, very different phenomena may ensue in the aftermath, such as thermonuclear supernovae." Ohlmann and colleagues are investigating the run-up to these stellar explosions, which are among the most luminous events in the universe and can light up a whole galaxy. But modeling the systems that can lead to such explosions is bedeviled by major uncertainty in the description of the common-envelope phase. One of the reasons for this is that the core of the giant is anything between a thousand and ten thousand times smaller than the envelope, so that spatial and temporal scale differences complicate the modeling process and make approximations necessary. The methodically innovative simulations performed by the Heidelberg scientists are a first step towards a better understanding of this phase.

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