Theoretical Physics

22 May 2013
Time: n/a

Alexander Adam (Imperial)

Bosonic Fractionalisation Transitions in Ads/CFT

Gauge gravity duality refers to the remarkable observation that under certain circumstances, gravitational theories can be equivalent to quantum field theories. In this talk, I will outline how this works assuming very little background in the subject and in particular will discuss how it can be applied to describe phenomena such as superconductivity and fractionalisation in condensed matter. More technically, charged holographic systems can be broadly divided into two classes: Those where the charge is sourced by electric flux due to bulk matter sources and those where it is sourced by bulk black hole horizons. The latter case is very interesting and may be associated with deconfined, gauge-variant degrees of freedom and consequently may be viewed as describing fractionalised matter in the dual field theory. I’ll discuss bosonic gravitational solutions of both these classes, breaking a global U(1) symmetry in the former case and leaving it unbroken in the latter. I will then exhibit phase transitions (fractionalisation transitions) between these two classes, both in the context of an engineered phenomenological model and in a more fundamental setting that arises from M theory. Finally I'll briefly speculate on how holography may provide clues as to a possible order parameter (analogous to Wilson loops) for charge fractionalisation in the form of the entanglement entropy.



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