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INT Program INT-18-1b
Multi-Scale Problems Using Effective Field Theories
May 7 - June 1, 2018

Reported by E. Braaten, N. Brambilla, T. Schäfer, A. Vairo
  Date posted June 19, 2018

Many contemporary open problems at the frontiers of nuclear and particle physics are characterized by the existence of a separation of scales that can be exploited using effective field theories (EFTs). The EFT method treats the low energy degrees of freedom as dynamical fields, and takes into account higher-energy scales systematically through matching conditions. The choice of the low-energy degrees of freedom that remain dynamical depends on the physical observables we wish to describe.

State-of-the-art applications of EFT involve multiple effective field theories to deal with several different scales. Examples include sequences of EFTs in which the dynamical degrees of freedom have increasingly lower energies. Other applications involve very different EFTs that are combined in innovative ways to systematically separate the scales. EFT methods developed in high energy and nuclear physics have been applied successfully in other fields, such as atomic, molecular, and solid state physics. Many-body systems involving multiple scales are of interest to physicists from many backgrounds, and new avenues for studying these systems in very clean settings have recently emerged in condensed matter physics and especially in atomic physics. Scope of this institute has been to bring together EFT practitioners with overlapping interests, but different specialized expertise, and lattice practitioners, phenomenologists and scientists with a different core expertise.

This interdisciplinary workshop focused on addressing multi-scale problems in various areas of physics using a variety of effective field theories and focusing of some of the most interesting contemporary problems, precisely:

  • Key problems in nuclear physics, such as transport properties of light particles, jets, and charmonia in dense matter, in which precision analysis of experiments is based on coupling several effective field theories.

  • Key problems in dark matter, including dealing with the multiple scales involved in the scattering of weakly interacting massive particles (wimps) in direct detection experiments and the annihilation of pairs of wimps in indirect detection experiments, especially when the wimps have resonant self-interactions.

  • The quantum and classical theoretical study of systems in non-equilibrium addressed with the tool of open systems combined with effective field theories. This subject overarched a large span of problems from the study of the nonequilibrium evolution of quarkonium in a medium to the study of dissipation at Black Hole horizon.

  • Exotics configuration arising in many body strongly coupled theories with particular reference to the X Y Z states observe at LHC experiments and at B and tau-charm factories. In this case new EFT constructions have been presented that allow to obtain and describe for the first time the spin structure of exotics hybrids. A novel alliance of EFT and lattice QCD is needed to fix all the nonperturbative parameters.

The workshop initiated new discussions between scientists with an expertise in effective field theories and those engaged in large scale lattice computations. We hope that one outcome of the workshop will be the lattice calculation of new EFTs defined low energy objects crucial for phenomenological applications.