Program

Talk information

Sunjin Choi: "AdS black holes and deconfinement"

We study supersymmetric AdS_d+1 black holes at large angular momenta, from the index of dual SCFT_d’s on S^d-1 X R in the large N and Cardy limit. In particular, we shall focus on the underlying physics to realize the deconfined N^d/2 degrees of freedom in CFT_d for d=3,4. In 4d CFTs, N^2 matrix degrees of freedom emerges in the deconfined phase. However, in 3d CFTs, monopole condensation confines most of the N^2 degrees of freedom except N^3/2 of them, even in the high temperature deconfined phase. Resulting large N free energies statistically account for the Bekenstein-Hawking entropies of large BPS black holes in dual AdS. We also briefly comment on novel deconfinement in 5d CFTs, where instanton solitons play subtle roles to realize deconfined N^5/2 degrees of freedom.

Richard Eager: "Hidden exceptional symmetry in the pure spinor superstring"

The pure spinor formulation of superstring theory includes an interacting sector of central charge 22, which can be realized as a curved βγ system on the cone over the orthogonal Grassmannian OG+(5,10). We find that the spectrum of the βγ system organizes into representations of the g=e6 affine algebra at level -3, whose so(10) ⊕ u(1) subalgebra encodes the rotational and ghost symmetries of the system. As a consequence, the pure spinor partition function decomposes as a sum of affine e6 characters. We then use the pure spinor partition function to describe the covariant spectrum of the open superstring. We remark on similar enhancements in curved βγ systems, including the cases g=so(8) and e7, corresponding to target spaces that are cones over the complex Grassmannian Gr(2,4) and the complex Cayley plane OP2. We identify these curved βγ systems with the chiral algebras of certain 2d (0,2) CFTs arising from twisted compactification of 4d N=2 SCFTs on S^2. Based on joint work with G. Lockhart and E. Sharpe.

Dongwook Ghim: "On the Witten index of theories with 2 real supercharges"

In this talk, I will formulate Witten index problems for theories with two supercharges in a Majorana doublet, such as in d=3 N=1 or in d=1 N=2. Regardless of spacetime dimensions, the wall-crossing occurs generically, in the parameter space of the real superpotential. After brief discussion on the theories only with scalar multiplets, we move on to abelian gauge theories. Even though the index theorem for the latter is a little more involved, we reduce it to winding number counting of the neutral part of superpotential’s derivative dW. The holonomy saddle plays key roles for both dimensions and also in relating indices across dimensions.

Yuji Hirono: "Topological order, higher-form symmetry, and dense quark matter"

The standard way of classifying phases of matter is the use of symmetry breaking patterns. It has been realized later that, if one considers quantum phases of matter, this is not sufficient. Namely,there can be distinct phases without changes of symmetry. Such an order of quantum phases is called a topological order. Identifying the topological structure of phases is important in determining the phase diagram of quantum matter. In this talk, I will review how a topological order can be captured by a generalized form of symmetry, called higher-form symmetries. Then, I’ll discuss an application of this idea to constrain the phase diagram of dense quark matter.

Lavneet Janagal: "Classifying and constraining local four photon and four graviton S-Matrices"

We study the space of all kinematically allowed four photon and four graviton S-matrices, polynomial in scattering momenta. We demonstrate that this space is permutation invariant sector of a module over the ring of polynomials of the Mandelstam invariants $s$, $t$ and $u$. We construct these modules for every value of the spacetime dimension $D$, and so explicitly count and parametrize the most general four photon and four graviton S-matrix at any given derivative order. We also explicitly list the local Lagrangians that give rise to these S-matrices. We then conjecture that the Regge growth of S-matrices in all physically acceptable classical theories is bounded by $s^2$ at fixed $t$. In the case of photons a four parameter subset of the polynomial S-matrices constructed above satisfies this Regge criterion. In the case of gravity, on the other hand, no polynomial addition to the Einstein S-matrix obeys this bound for $D \leq 6$. When $D \geq 7$ there is a single six derivative polynomial Lagrangian consistent with our conjectured Regge growth bound. Our conjecture then implies that the Einstein four graviton S-matrix does not admit any physically acceptable polynomial modifications for $D\leq 6$. A preliminary analysis suggests any finite sum of pole exchange contributions to four graviton scattering also such violates our conjectured Regge growth bound, atleast when $D\leq 6$, even when the exchanged particles have low spin. In the process, we classified the basis structures for photon and graviton local S-matrices. (Based on 1910.14392)

Jung-Wook Kim: "Kerr-Newman black hole stress tensor from QFT"

A common misconception among physicists is that loop effects in quantum field theory are quantum effects, in the sense that such effects always accompany higher powers in Planck's constant. This belief has been shown to be untrue using different counterexamples, and we add another counterexample to the list; the matter stress tensor of Kerr-Newman spacetime to all orders in spin. This is an old counterexample which already has been computed up to linear order in spin, but its extension to higher orders in spin has been obstructed by inefficient computation tools. We show that new tools of modern amplitude techniques can overcome the obstacle and the old counterexample extends to all orders in spin, alluding to the conclusion that computation of all orders in spin dynamics of NRGR from QFT is a viable approach.

Sejin Kim: "Perturbation Approach for Mass deformed Theories"

We solve the associated BPS equations, requiring IR regularity, using a perturbative method proposed. We find the exact solution holographic free energy upto reading order. In particular, we provide an analytic proof of a crucial conjecture based on numerical solutions.

Kanghoon Lee: "Double Copy Meets Double Field Theory"

I will present a generalization of the conventional KS formalism, which is a powerful tool for constructing exact solutions in general relativity, to double field theory (DFT) and supergravities. I will describe the generalized KS ansatz for the generalized metric in terms of a pair of null vectors and apply this ansatz to the equations of motion of DFT. I'll show that it is possible to find solutions by considering linear equations only. Based on this formalism, I'll discuss that the classical double copy structure, which represents solutions of the Einstein equation in terms of solutions of the Maxwell equation, can be extended to the entire massless string NS-NS sector.

Ki-Hong Lee: "Instantons from blow-up"

In this talk, I will introduce some consistency conditions called "blow-up equations" that partition functions of 4d and 5d gauge theories must satisfy. Using blowup equations, I will introduce a method to compute instanton partition functions for an arbitrary gauge group with a large class of matter representations from their perturbative partition functions.

June Nahmgoong: "6d Cardy formulas from self-dual strings"

In this talk, we study the partition functions of 6d (2,0) SCFTs on R4 X T2 and S5 X S1. I will show that their Cardy limit asymptotics can be obtained from the elliptic genus of self-dual strings. The resulting free energy is proportional to N^3 for N M5-branes, and it statistically accounts for the entropy of dual AdS7 black holes.

Matthieu Sarkis: "Algebraic surfaces and Mathieu Moonshine"

After reviewing some facts about Mathieu moonshine as discovered by Eguchi, Ooguri and Tachikawa in the context of NLSMs with K3 target on the one hand, and the geometrical definition of the elliptic genus of a complex manifold on the other hand, we enlighten a mysterious connection between compact complex surfaces and the Mathieu moonshine.

Jaewon Song: "On the large N limit of superconformal field theories and supergravity."

Most of the well-known instances of the AdS/CFT correspondence maps large N SCFT to semi-classical supergravity in AdS. However, the AdS/CFT maps any CFTs to a 'quantum gravity' in AdS, even though it may not be similar to the Einstein gravity. In this talk, I will outline some attempts to extract generic features of AdS quantum gravity using large N SCFT.

Minwoo Suh: "First order system of two-dimensional dilaton gravity and supersymmetric AdS black holes"

We look into the problem of AdS black holes from two-dimensional gravity perspective. It is one of the essential element for calculations in gravity that, for domain wall backgrounds in dimensions higher than two, the second order equations of motion reduce to a first order system. In supergravity, the first order system, in fact, reproduces the BPS equations obtained from the supersymmetry variations. In this work, we extend the known results to dimensions two and derive the first order system in two-dimensional dilaton gravity. As examples, we show that recently studied supersymmetric AdS black hole solutions generically dimensionally reduce to two-dimensional dilaton gravity, and obtain the first order systems for black hole solutions. We also propose that the dilaton contains the information of the Bekenstein-Hawking entropy of supersymmetric AdS black holes in higher dimensions.