Upcoming Events

We are deprecating this webpage in favour of our new website to which you will be redirected in a few seconds. The new website features our usual weekly seminar announcement as well as a calendar with up-to-date information about upcoming seminars and workshops, in addition to other useful information about our group at NTU. Please bookmark it (and/or subscribe to the calendar) for your future visits. Thank you!

Schedule of Seminars at NTU

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 CFT2 on a Symmetric Product and Pulsating Strings
Abstract: We propose a state in 2d conformal field theory on the orbifold (T4)N/S(N) as a dual description for a pulsating string moving in AdS3. 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 ΔJ satisfies the sum rule J²\ΔJ - [ (J²/2) + (J/4) + (3/16) ] ΔJ+1 - [ (J²/2) - (J/4) + (3/16) ] ΔJ-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 ΔJ + √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. 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.

Schools & Conferences

8th Taiwan String Workshop
Nov.16 (Mon.) - Nov.20 (Fri.), 2015, NTHU, Hsinchu, Taiwan.
Amplitudes in Asia 2015
Nov.2 (Mon.) - Nov.6 (Fri.), 2015, NTU, Taipei, Taiwan.
Gravity and Beyond
Jul.6 (Mon.) - Jul.10 (Fri.), 2015, NTU, Taipei, Taiwan.
Strings 2015
Jun.22 (Mon.) - Jun.26 (Fri.), 2015, Bangalore, India.
The 2nd Joint Kyoto-NTU High Energy Theory Workshop
Mar.27 (Fri.) - Mar.29 (Sun.), 2015, NTU, Taipei, Taiwan.
StringWiKi link