Sep 11 (Fri.) 2:20-3:20 PM

NTU New Physics Building Room 815

*Chrysostomos Kalousios* (ICTP-SAIFR, Sao Paulo)

Comments on the Scattering Equations

*Abstract:* I will present the latest developments and ideas in calculating scattering amplitudes of massless theories in arbitrary dimensions using the formalism of the scattering equations.

Sep 18 (Fri.) 2:20-3:20 PM

NTU New Physics Building Room 815

*Tadashi Okazaki* (NTU)

Beyond Planar M2-branes

*Abstract:* I will discuss descriptions of curved and attached M2-branes beyond planar case via topological twist and supersymmetric boundary conditions in supersymmetric gauge theories. I will also sketch some projects currently under investigation and relevant applications in math and physics.

Sep 25 (Fri.) 2:20-3:20 PM

NTU New Physics Building Room 815

*Pei-Ming Ho* (NTU)

Geometry of Area without Length

*Abstract:* To define a free string by the Nambu-Goto action, all we need is the notion of area, and mathematically the area can be defined directly in the absence of a metric. Motivated by the possibility that string theory admits backgrounds where the notion of length is not well defined but a definition of area is given, we study space-time geometries based on the generalization of metric to area metric. In analogy with Riemannian geometry, we define the analogues of connections, curvatures and Einstein tensor. We propose a formulation generalizing Einstein's theory that will be useful if at a certain stage or a certain scale the metric is ill-defined and the space-time is better characterized by the notion of area. Static spherical solutions are found for the generalized Einstein equation in vacuum, including the Schwarzschild solution as a special case.

Oct 2 (Fri.) 2:20-3:20 PM

NTU New Physics Building Room 815

*Douglas J. Smith* (Durham University)

Supersymmetric Open M2-brane Actions

*Abstract:* I will discuss some aspects of multiple open M2-branes. One motivation is to study multiple self-dual strings within the M5-brane worldvolume, which arise as the boundary of M2-branes ending on an M5-brane. The BLG and ABJM models for multiple M2-branes are Chern-Simons matter theories. As such they need to be modified in the presence of a boundary to preserve gauge invariance. I will first review how a pure Chern-Simons theory can be suitably modified by adding boundary degrees of freedom, resulting in a WZW model. I will then describe recent work (in progress) to construct the boundary action which also preserves (some) supersymmetry.

Oct 16 (Fri.) 2:20-3:20 PM

NTU New Physics Building Room 815

*Carlos Andres Cardona Giraldo* (NTHU)

Deforming CFT_{2} on a Symmetric Product and Pulsating Strings

*Abstract:* We propose a state in 2d conformal field theory on the orbifold (T^{4})^{N}/S(N) as a dual description for a pulsating string moving in AdS_{3}. We show that, up to first order in the deforming parameter, the energy in both descriptions has the same dependence on the mode number, but a nontrivial function of the coupling.

Oct 23 (Fri.) 2:20-3:20 PM

NTU New Physics Building Room 815

*Simeon Hellerman* (Kavli IPMU)

BIG J: On the Conformal Operator Spectrum at Large Global Charge

*Abstract:* We calculate the anomalous dimensions of operators with large global charge J in certain strongly coupled conformal field theories in three dimensions, such as the O(2) model and the supersymmetric fixed point with a single chiral superfield and a W = Φ³ superpotential. Working in a 1/J expansion, we find that the large-J sector of both examples is controlled by a conformally invariant effective Lagrangian for a Goldstone boson of the global symmetry. For both these theories, we find that the lowest state with charge J is always a scalar operator whose dimension Δ_{J} satisfies the sum rule J²\Δ_{J} - [ (J²/2) + (J/4) + (3/16) ] Δ_{J+1} - [ (J²/2) - (J/4) + (3/16) ] Δ_{J-1} = 0.04067, up to corrections that vanish at large J. The spectrum of low-lying excited states is also calculable explicitly: For example, the second-lowest primary operator has spin two and dimension Δ_{J} + √3. In the supersymmetric case, the dimensions of all half-integer-spin operators lie above the dimensions of the integer-spin operators by a gap of order J^{+½}. The propagation speeds of the Goldstone waves and heavy fermions are 1/√2 and ±½ times the speed of light, respectively. These values, including the negative one, are necessary for the consistent realization of the superconformal symmetry at large J.

Oct 30 (Fri.) 2:20-3:20 PM

NTU New Physics Building Room 815

*Akinori Tanaka* (RIKEN)

Exact Path Integral for 3D Quantum Gravity

*Abstract:* In 2007, it was conjectured by E. Witten that the chiral part of the partition function of 3d pure AdS Einstein gravity in a quantum regime coincides with so-called modular J-function, a partition function of certain holomorphic CFT, called "monster CFT" considered by I. B. Frenkel, J. Lepowsky and A. Meurman in the context of monstrous moonshine. We tried to calculate the partition function for the 3d pure AdS Einstein gravity directly by utilizing recently developed localization techniques, and arrived at the J-function from purely gravity side under some plausible assumptions.

This talk is based on arXiv:1504.05991.