Talks

How many interacting quantum (field) theories of four-dimensional geometry are there which have General Relativity as their classical limit? Some of us still harbour hopes that a quantum theory of gravity is "reasonably unique", i.e. characterized by a finite number of free parameters. One framework in which such universality may manifest itself is that of "Quantum Gravity from Causal Dynamical Triangulations (CDT)". I will summarize the rationale behind this nonperturbative formulation and CDT's main achievements in trying to explain the micro- and macro-structure of spacetime from first principles. This includes the remarkable property of "dynamical reduction" of the spacetime dimension from four to two at the Planck scale.

A new force mediated by a new vector boson with mass in the MeV to GeV range and with very weak coupling to ordinary matter appears naturally in many theoretical models and could also explain a variety of observed anomalies. Such anomalies include the discrepancy between the predicted and the experimentally observed value for the muon anomalous magnetic moment, and recent cosmic-ray data that can be explained by dark matter interacting through this force with ordinary matter. This talk will review the motivation for such a force and present a broad array of probes of this physics. These probes include high-luminosity e+e- colliders, such as BaBar and BELLE, whose existing data sets may contain thousands of spectacular events; new high-intensity fixed-target experiments at electron accelerators such as Jefferson Laboratory; and indirect astrophysical probes such as gamma-ray observations of Milky-Way dwarf satellite galaxies, which constitute some of the least luminous and most dark matter dominated galaxies known.

ABJM theory is a world-volume theory for an arbitrary number of M2-branes. One of the unique features of ABJM theory is its characteristic scaling behaviour, exhibited for example by the free energy and correlation functions of chiral primary operators. In more detail, ABJM theory has a holographic dual where thermodynamics at strong coupling is determined by a system of black M2-branes. The zero-coupling (black-body radiation) free energy disagrees with the strong coupling result. Even the scaling in the 't Hooft coupling is different (strongly suppressed at strong coupling). It is therefore important to check that the weak and strong coupling results converge as loop corrections are taken into account. The leading order computation indeed confirms that the first correction goes in the right direction.

Quantum key distribution (QKD) is an application of quantum theory as its security relies on quantum foundations, at the same time there is development in the information-theoretic point of view to quantum theory. The security is related to impossible quantum performance, for instance, neither perfect quantum cloning nor perfect quantum state discrimination are possible. In this talk, I would like to discuss issues relevant to practical and fundamental sides of QKD: i) toward characterization of quantum correlations from which a secret key can be distilled, ii) determination whether quantum states shared by two honest parties in distance are entangled or separable, and iii) limitations on quantum performance by fundamental principles in quantum theory.