Search Talks

Modified gravity models seem to have classical instabilities, ghosts degrees of freedom and superluminal modes. Besides these constraints new dynamical bounds have found to be typical of these models. The cosmological nature of all these constraints is discussed.

Existence of dark energy and nonzero nu mass are two most exciting discoveries of recent years. More excitingly, the similarity between the energy scales of these two raise the question: "Are they related?" I will explore how such connection could be there in nature and its cosmological consequences mainly in structure formation.

The exact boundary states for the rolling D-brane solution in two-dimensional black hole systems will be presented.I will study the physical significance of the solution in relation to the ``tachyon-radion correspondence\" and the ``black hole - string transition\". When the alpha\' corrections become larger, when at the same time the Hawking temperature coincide with the Hagedorn temperature, the phase transition occurs and the physics changes drastically. It also suggests the universal feature of the decaying D-brane and its failure in the strong quantum regime. The talk is based on my series of works hep-th/0605013, hep-th/0507040 in collaboration with Soo-jong Rey (SNU) and Yuji Sugawara (Tokyo).

We have previously isolated and characterized a multipotent precursor cell (termed SKPs for SKin-derived Precursors) from both rodent and human skin, and have shown that these stem cells share many characteristics with a multipotent stem cell that is found in the embryo termed a neural crest stem cell. Here I will discuss our current work with regard to the basic biology of these stem cells, with a focus on the “what, where and why”, and on their therapeutic potential with specific regard to the nervous system.

Most modern discussions of Bell's theorem take microscopic causality (the arrow of time) for granted, and raise serious doubts concerning realism and/or relativity. Alternatively, one may allow a weak form of backwards-in-time causation, by considering "causes" to have not only "effects" at later times but also "influences" at earlier times. These "influences" generate the correlations of quantum entanglement, but do not enable information to be transmitted to the past. Can one realize this scenario in a mathematical model? If macroscopic time-asymmetry is introduced by imposing initial conditions, such a model can not be deterministic. Stochastic Quantization (Parisi and Wu,1981) is a non-deterministic approach known to reproduce quantum field theory. Based on this, a search for models displaying quantum nonlocal correlations, while maintaining the principles of realism, relativity and macroscopic causality, is proposed.

It will be shown that eternal inflation of the random walk type is generically absent in the brane inflationary scenario. Eternal inflation will be analysed both in the context of KKLMMT and the DBI inflationary models. A Langevin analysis will be employed for a more careful treatment. The DBI action, and the relativistic nature of the brane motion in DBI inflationary model, leads to new subtleties in formulating a Langevin approach.

I will discuss some ambiguities involved in using the AdS/CFT correspondence to calculate the ultra-relativistic jet quenching parameter for quarks moving in an N=4 super Yang-Mills thermal bath. Along the way, I will investigate the behavior of various string configurations on a five-dimensional AdS black hole background.