FM 18: Scale-free processes in the universe

Start Date: 
Wednesday, August 12, 2015
End Date: 
Friday, August 14, 2015
Co-Chairs of SOC: 
  • Edith Falgarone (ENS and Paris Observatory)
  • Bruce Elmegreen (IBM Watson)

Scientific Organizing Committee

  • Monique Arnaud (CEA)
  • Deepak Dhar (Tata Institute, India)
  • Torsten Ensslin (MPA)
  • Michiko Fuji (NAOJ)
  • Bryan Gaensler (University of Sydney)
  • Gerry Gilmore (University of Cambridge)
  • Sangeeta Malhotra (Arizona State University)
  • Simon Portegies-Zwart (Sterrewachts Leiden, The Netherlands)
  • Kazunari Shibata (Kyoto University)
  • Steven Spangler (University of Iowa)
  • Romain Teyssier (Institute for Theoretical Physics, Switzerland)
  • Enrique Vasquez Semadeni (Universidad Nacional Autónoma de México)
  • Ellen Zweibel (University of Wisconsin-Madison)

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The following broad areas will be discussed in the perspective of the interdisciplinary spirit of the meeting:

We especially wish to encourage contributions which emphasize the trans-disciplinarity of the meeting. The final balance between the topics will depend on the distribution of the submitted abstracts among the different topics. 


Most of the distribution functions in the universe, including those for mass, energy, and structure of components like dark matter, galaxy clusters, galaxies, magnetic fields, cosmic rays, star clusters, and stars, have power-law shapes indicating a lack of definite scales in whatever processes determine their formation and organization. As these scale-free behaviors are obtained without fine-tuning, they are by definition self-organized critical, which raises fascinating questions regarding the respective roles of long-range (gravity) and short-range (collisional) interactions. These questions touch on the interaction between dark matter, baryons, cosmic rays and magnetic fields, the importance of scales where the power-laws break down, the observed deviations from power-laws, and the range of scales that are truly coupled. Computer simulations now include a large enough range of scales to reproduce some of these power-laws, and recent theoretical analyses attempt to unify them. 

The main objective of this Focus Meeting  is to gather cosmologists, astrophysicists and statistical physicists, whether they are observers, theoreticians or numericists.  It will provide an opportunity to exchange ideas from different horizons and plan the next steps in this global investigation.

Key Topics: 

The meeting will be trans-disciplinary and focused on the key topics:

  1. Universality (or not) of power-law probability distribution functions: breaks and deviations
  2. Interplay between cosmic rays, magnetic fields, turbulence, and gravity
  3. Interplay of dark matter and baryons: baryonic fragmentation versus dark matter clustering in
  4. Hierarchical systems
  5. Transitions from cosmological to baryonic physics
  6. Insights from the physics of critical phenomena and self-organized criticality
  7. Steps toward better boundary conditions and sub-grid physics in computer models