Talks

In the context of class S theories and 4D/2D duality relations there, we discuss the skein

relations of general topological defects on the 2D side which is expected to be counterparts

of composite surface-line operators in 4D class S theory. Such defects are geometrically

interpreted as networks in a three dimensional space. We also propose a conjectural com-

putational procedure for such defects in two dimensional SU(N) topological q-deformed

Yang-Mills theory by interpreting it as a statistical mechanical system associated with

ideal triangulations.

This talk is based partly on arXiv:1504.00121 with Yuji Tachikawa (Phys.Univ.Tokyo) and much on a forthcoming paper in arXiv.

The Weak Gravity Conjecture (WGC), in its original form, says that given an abelian gauge theory there should be at least one charged particle whose charge is bigger than its mass in Planck units. This has surprisingly powerful implications for the possibility of large-field inflation. In this talk I will explore some of the arguments linking the WGC to inflation before taking a closer look at a different question: which version of the WGC should we be trying to prove? I suggest that the right version to focus on is much stronger than the original WGC, and requires a sufficiently light particle to exist in every representation of the gauge group. I will present some evidence for this statement from both weakly-coupled string theory and semiclassical GR. This talk is based on work with Ben Heidenreich and Tom Rudelius (arXiv:1506.03447, 1509.06374, and further work in progress).

The ordinary atoms that make up the known universe, from our bodies and the air we breathe to the planets and stars, constitute only 5 percent of all matter and energy in the cosmos. The remaining 95 percent is a recipe of 25 percent dark matter and 70 percent dark energy, both nonluminous components whose nature remains a mystery.

In her March 2 public lecture, Katherine Freese will recount the hunt for dark matter, from the discoveries of visionary scientists like Fritz Zwicky, the Swiss astronomer who coined the term "dark matter" in 1933, to the deluge of data today from underground laboratories, satellites in space, and the Large Hadron Collider.