Organizers:
Hans-Werner Hammer
Shina Tan
Program Coordinator:
Seminar Schedules:
Exit report
This program will be accompanied by a five-day workshop entitled: "Few-body Universality in Atomic and Nuclear Physics: Recent Experimental and Theoretical Advances". Workshop dates: May 12, 2014 - May 16, 2014 Workshop Organizers: Doerte Blume Washington State University doerte@wsu.edu
Francesca Ferlaino |
INT Program INT-14-1 Universality in few-body systems: Theoretical challenges and new directions March 10, 2014 - May 16, 2014
The program will focus on the universality in few-body systems relevant to atomic and nuclear physics. Theoretical challenges and new directions will be discussed and identified, and confronted with experimental results where possible. The program will be capped by a five-day workshop, which will bring
together theorists and experimentalists from both atomic and nuclear physics.
The program seeks to bring together researchers with diverse backgrounds from the atomic and nuclear physics communities. Hence we wish to attract scientists with different strengths: researchers who are well-versed in the intricacies of multi-channel atom-atom scattering or the two- and three-body nuclear interactions; experts on connecting the few- and many-body problems; scientists who have strong analytical expertise; scientists with knowledge of diverse numerical approaches to few-body calculations (e.g. in coordinate or momentum space, for bound-state and scattering states), and people with a strong background in effective field theory. The program will have around 10 to 15 participants at any given time. Participants will be invited to present their work during informal morning talks (at a rate of about one talk per day). In addition, we will organize two weekly afternoon discussions on topics of common interest. We will particularly encourage discussions that aim at identifying and defining new frontiers within the area of universal few-body physics, and which aim at establishing concrete connections between theoretical predictions and experimental observables. The program will be accompanied by a five-day workshop entitled: "Few-body Universality in Atomic and Nuclear Physics: Recent Experimental and Theoretical Advances". Workshop dates: May 12, 2014 - May 16, 2014
Friday, May 16: workshop ends at 12.30pm Doerte Blume Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2814 Phone: +1-509-335-2412, email: doerte@wsu.edu Francesca Ferlaino Institut für Experimentalphysik Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria Phone: +43-512-507-6340, email: Francesca.Ferlaino@uibk.ac.at Chris Greene Department of Physics, Purdue University, West Lafayette, IN 47907 phone: +1-765-496-1859, email: chgreene@purdue.edu Daniel Phillips Department of Physics and Astronomy, Ohio University Athens, OH 45701 phone: +1-740-593-1698, email: phillips@phy.ohiou.edu Details regarding the five-day workshop will be posted closer to the event. More background: Few-body physics has played a prominent role in atomic, molecular and nuclear physics since the early days of quantum mechanics. One of the most prominent examples of this is the three-body Efimov effect, which was predicted in the early seventies by Vitaly Efimov, a nuclear theorist. Motivated by the large scattering lengths in the two-nucleon system, Efimov considered the---at the time hypothetical---three-body system with resonant two-body interactions. He predicted that this system would have an infinite geometric sequence of bound states, with successive binding energies in the ratio 515:1. Despite concerted theoretical and experimental efforts, it was not until 2006 that Efimov's rather counterintuitive prediction was confirmed in cold-atom experiments. Since then, there has been an explosion of interest and effort focused on the physics of few-body systems which have features in common with Efimov's original scenario. On the theory side the effective hyperspherical potential curves that underlie Efimov's analysis have been found to be an elegant way of understanding universal aspects of low-energy three-body collisions, while an expansion around the "unitary limit" of resonant interactions provides the basis for an effective field theory within which generic properties of strongly interacting quantum systems can be derived. These methods have led to intriguing extensions of Efimov's result to four-, and higher-, body systems, as well as hypotheses regarding the implications of "Efimov physics" for phases of many-body quantum systems with resonant two-body interactions. Several of the theoretical results produced in this direction since 2006 have stimulated, and ultimately been confirmed in, experiments with cold atomic gases. Thus, in this area of few-body physics theory and experiment are both developing rapidly, in a mutually beneficial fashion. In so doing they inform our understanding of systems ranging from cold gases of atoms, to few-hadron systems, to halo nuclei. The program aims to seize this opportunity by bringing together leading theorists working on aspects of few-body systems which, like the Efimov effect, are universal. Throughout, the term "universal" is used quite broadly. It indicates that a certain observable or phenomenon can be described by a finite and well-defined parameter or set of parameters, e.g. an observable which depends only on the s-wave scattering length, or on that observable and the so-called three-body phase which determines the particular energies of three-body bound states in Efimov's problem. A major boost for theorists working on questions related to universal few-body physics has come from the tremendous progress made in cold-atom experiments. The ability to manipulate samples of atoms at cold or ultracold temperatures, and to measure observables such as trap losses, yields information on two-, three- and four-atom processes. This, combined with the experimental tunability of scattering parameters (e.g. the two-body scattering length), has driven many of the advances in this area. These advances have significant implications for systems bound by the strong interaction. Such systems are to be understood as providing "effective" few-body problems, e.g. few-nucleon systems at energies such that their quark substructure is not resolved, and halo nuclei examined in the regime where a treatment in terms of a small number of clustered degrees of freedom is appropriate. In a similar vein, hadronic molecules can also be treated as few-body systems (e.g., the X(3872) as a D^{*} D molecule) in a low-energy regime where the substructure of the clusters making up the bound states is not resolved. The Efimov effect is then (approximately) realized already in the three-nucleon problem---a fact that we now understand is associated with the "universal" correlations in these systems, such as the Phillips line (correlation of triton binding and doublet neutron-deuteron scattering length) and the Tjon line (correlation of three- and four-body binding energies). Similar correlations are being discovered in more complex effective few-body problems, e.g. some halo systems. Few-body universality thus complements ab initio approaches to these nuclei by providing a way to understand and predict correlations between different observables in loosely-bound nuclear systems. This, in turn, opens the possibility to look for universal aspects of nuclear systems close to the driplines. These nuclei will be investigated at present and future radioactive beam facilities, and provide another arena for universal phenomena in nuclear physics. The ten-week program will identify key problems and challenges in the investigation of universal aspects of these few-body systems. With the Efimov effect now well established for three equal-mass particles interacting via resonant s-wave interactions in three dimensions, we want our program to identify and characterize universal physics in four- and higher-body systems and determine universal aspects of non-central interactions. We want to discuss and develop the theoretical tools that will permit a rigorous treatment of these highly non-trivial problems, where dynamics occurring at scales differing by several orders of magnitude can affect the final result. And we want to determine which experimental signatures theorists can predict, and which observables are sufficiently sensitive to discriminate between different hypotheses regarding universality in these emerging contexts. |