This week

Wednesday

Wilson Surface Central Charge

Regular Seminar Andy O'Bannon (University of Southampton)

 at: 13:15 KCLroom S2.49 abstract: M-theory is currently our best candidate for a theory of everything, but remains mysterious. We know M-theory has M2- and M5-branes. The low-energy theory on a stack of coincident M2-branes is well-understood: it is maximally supersymmetric Chern-Simons-matter theory. However, the low-energy theory on a stack of coincident M5-branes remains poorly-understood: it is a maximally supersymmetric theory of self-dual strings with zero tension. In this talk I will discuss one type of probe of the M5-brane theory, namely self-dual strings with infinite tension. These play a role analogous to Wilson lines in gauge theories, but are two-dimensional surfaces rather than lines, and hence are called Wilson surfaces. I will describe holographic calculations of entanglement entropy associated with these infinite-tension self-dual strings, from which we extract a key parameter characterizing them, their central charge. This provides a count of the number of massless degrees of freedom living on them, and thus may shed light on some of the fundamental degrees of freedom of M-theory.

Polygon Seminar: tba

Triangular Seminar Hugh Osborn (DAMTP, Cambridge University)

 at: 15:00 ICroom Blackett LT2 abstract: tba

Polygon Seminar: Exploring generalised dualities and integrable deformations

Triangular Seminar Daniel C Thompson (Swansea)

 at: 16:30 ICroom Blackett LT2 abstract: Extensions of target space T-duality to non-Abelian isometry groups and even to spaces without isometry have found recent utility within the AdS/CFT correspondence and have played a central role in the development of new classes of integrable string backgrounds called $\eta$ and $\lambda$-models. After a pedagogical introduction to the topic I will outline some recent results concerning the open sector of $\lambda$-models and the interpretation of these theories within the formalism of double field theory.

Thursday

Holographic relative entropy in infinite-dimensional Hilbert spaces

Regular Seminar Monica Kang (Harvard)

 at: 14:00 QMWroom G O Jones 610 abstract: Quantum error correction provides a convenient setup where bulk operators are defined only on a code subspace of the physical Hilbert space of the conformal field theory. I will first reformulate entanglement wedge reconstruction in the language of operator-algebra quantum error correction with infinite-dimensional physical and code Hilbert spaces. I will streamline my proof that for infinite-dimensional Hilbert spaces, the entanglement wedge reconstruction is identical to the equivalence of the boundary and bulk relative entropies. I will discuss its implications for holographic theories with the Reeh-Schlieder theorem.

Friday

Goldstone pairs at the Fermi surface

Exceptional Seminar Alberto Nicolis (Columbia)

 at: 14:00 ICroom H503 abstract: I will adapt the Goldstone theorem to spontaneously broken boosts, and show that, while still predicting gapless Goldstone states, it is quite forgiving regarding the nature of such states. In particular, I will show that while for solids and superfluids the role of the boost Goldstone states is played by phonon single-particle states, for a Fermi liquid such a role is played by the particle-hole continuum, that is, by two-particle states.