# Holography and Applied String Theory (13w5054)

Arriving in Banff, Alberta Sunday, February 10 and departing Friday February 15, 2013

## Organizers

Johanna Erdmenger (Max Planck Institute, Munich)

Sean Hartnoll (Stanford University)

Gordon Semenoff (University of British Columbia)

## Objectives

The objective of this 5-day workshop is to develop and consolidate the use of string theory holography as a tool for the understanding and analysis of strongly coupled quantum systems. There are two main lines of investigation. 1.) One line of research is focused on components of the standard model of elementary particle physics that are strongly coupled. One success of holography and a focus of ongoing work is centered on understanding hadronic matter whose structure is governed by the strong nuclear interactions. It has already had some success in describing the low viscosity fluid state of the fireball of hadronic matter which was created in heavy ion collision experiments at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. At high energies and densities like those created in the heavy ion collisions, hadronic matter is expected to behave like a plasma of weakly interacting quarks and gluons, the elementary excitations of Yang-Mills theory. Surprisingly, at the RHIC energy scale, it was found to behave differently, as an ultra-low viscosity, strongly coupled fluid. Moreover, this fluid state was qualitatively described by a hologrpaphic gauge field theory. The next generation heavy ion collider, the Alice experiment, which is now in operation at the Large Hadron Collider site at CERN in Geneva, and which is designed to create a hadronic fireball at higher temperature is currently operating and data will become available in the near future. It will be very interesting to see whether the holographic approach to gauge theory has similar impact there. Spring of 2013 should be good timing for a workshop on this subject as the first wave of data could be digested by then. Another component of the standard model of elementary particle physics describes the unified theory of the weak nuclear and the electromagnetic interactions. These are conventionally thought to be so weakly interacting as to be for all intents and purposes solved by perturbation theory. The Large Hadron Collider (LHC) is now performing an intensive search the Higgs Boson as well as other new physics which is anticipated at the electroweak energy scale. These could well be discovered between the time of writing of this proposal and the time when it is read. If, as some current indications seem to suggest, the Higgs Boson turns out to be heavy, or if it is not found at all, the electroweak sector of the standard model must in fact be strongly coupled. In that scenario, there is no doubt that the holographic approach to strong coupling field theory will attract significant attention as the only analytic theoretical approach to studying gauge field theories such as the standard model of particle physics in scenarios where weak coupling perturbation theory fails. By December, 2012, the LHC is scheduled to have completed its full experimental run at the current beam energy. This run has enough energy and it is expected to take enough data to either discover or rule out the Higgs boson up to quite a high energy, 600GeV. In the case that Higgs is heavy, even at the top of the current, still open, 145Gev window, the proposed workshop on the use of string theory to study strongly coupled field theory in early 2013 could have remarkably good timing. 2.) The second line of research is to the application of holographic techniques to condensed matter systems in two and three dimensions, in particular to systems exhibiting quantum critical behavior. The present focus of this research is to use the paradigm of strongly coupled field theory at high density and temperatures to gain understanding of non-fermi liquid ground states and thermal states of quantum systems of interacting electrons. This addresses some of the most interesting challenges in condensed matter physics, which involve strongly interacting systems of fermions and other components. One of the outstanding problems there is to understand non-Fermi liquid' behavior, which is widely believed to require physics going beyond weakly interacting fermions. Of particular interest are the thermodynamic and transport properties of the observed but unexplained strange metal' phases of heavy fermion compounds and high temperature superconductors. The proposed workshop will have a hard focus on developing string theory holography as a tool for studying strongly coupled dynamical systems in nature. A range of systems will be discussed, with a view towards identifying questions where holographic techniques can be usefully applied. Topics to be covered include hadronic physics at high temperature and density, holographic constructions of the standard model of particle physics, quantum critical transport, hydrodynamics, superconductivity and quantum criticality, deconfined criticality, quantum hall physics, fermions at unitarity and entanglement entropy. The partial list of prospective participants, all of whom have expressed significant enthusiasm for a workshop of this kind, represent the current leading research groups in this field. A number of further invitations will be reserved for closer to the time of the workshop to attempt to include representatives of the most current developments. We also intend to include a number of young researchers at the Postgraduate and Postdoctoral levels.