Talks

We will discuss some expectations regarding properties of N=1 SCFTs in four dimensions obtained by compactifying (1,0) theories in six dimensions on a Riemann surface. We will illustrate in detail how these properties come about in the special case of compactifications of two M5 branes probing Z_2 singularity.  In particular, we will obtain a large class of strongly coupled  N=1 theories in four dimensions obtained in such compactifications. We will derive some of their robust properties, such as anomalies and supersymmetric indices.

In the framework of the ordinary seesaw model with right-handed neutrinos (and nothing else) we show that the total lepton number violating decay of the Higgs doublet into a right-handed neutrino and a standard model lepton can successfully account for the baryon asymmetry of the Universe. This is possible thanks to thermal effects shortly before the sphalerons decouple.

The AdS/Ricci-flat (AdS/RF) correspondence is a map between families of asymptotically locally AdS solutions on a torus and families of asymptotically flat spacetimes on a sphere. In this talk I will discuss how to relax these restrictions for linearized perturbations around solutions connected via the original AdS/RF correspondence.
To this end we perform a Kaluza-Klein (KK)  reduction, keeping all (massive) KK modes,  of AdS on torus and of Minkowski on a sphere.  We show that in the limit of large dimension of the compact manifolds (torus and sphere), the AdS/RF correspondence maps individual KK modes from one side to the other.
When the dimension is finite, the correspondence maps single modes to infinite superpositions of modes. One may further take appropriate limits so that there is either no torus (AdS side) or no sphere (Minkowski side) to map perturbations of solutions that possess no symmetry, thus completely relaxing the original restrictions.
This correspondence should allow us to develop a detailed holographic dictionary for asymptotically flat spacetimes.

The origin and composition of 85% of the matter in the universe is completely unknown. Among several viable options, Weakly Interacting Massive Particles (WIMPs) are motivated dark matter candidates that can be tested by different and complementary search strategies. Crucially, different searches probe WIMP couplings at different energy scales, and such a separation of scales has striking consequences in connecting different experimental probes. This motivates the development of theoretical tools to properly connect the different energy scales involved in constraining WIMP models. I will introduce these tools and I will illustrate with several examples how crucial the inclusion of these effects in WIMP searches is.

In this talk, we will discuss an open Gromov-Witten invariant on hyperKahler surfaces, including K3 surfaces and certain Hitchin moduli spaces. The invariant is defined via the Lagrangian Floer theory and satisfy the Kontsevich-Soibelman wall-crossing formula and are expect to recover the generalized Donaldson-Thomas invariants studied in the work of Gaiotto-Moore-Neitzke.

More than a billion years ago, two black holes collided. In the final second of their long life together, the black holes banged out a rhythm like mallets on a drum, creating gravitational waves – ripples in the shape of spacetime. One hundred years ago, Albert Einstein predicted the existence of such waves, though it seemed improbable – if not outright impossible – that we’d ever be able to actually detect them. They were long considered too faint for any earthbound experiment to measure. Undaunted, experimentalists were determined to measure these Lilliputian ripples, and after many decades of work and collaboration, they built LIGO – the Laser Interferometer Gravitational-Wave Observatory. This incredible sophisticated and sensitive instrument was made to listen for the beat of that distant drum. In 2015, a billion years after the two black holes collided, their waves rippled through the LIGO detectors in Louisiana and Washington. With these remarkable new observatories, we can now capture the soundtrack to accompany the silent movie of the history of our universe.

Collisions at the Large Hadron Collider (LHC) are dominated by jets, collimated sprays of particles that arise from quantum chromodynamics (QCD) at high energies.  With the remarkable performance of the ATLAS and CMS detectors, jets can now be characterized not just by their overall direction and energy but also by their substructure.  In this talk, I highlight the increasingly important role that jet substructure is playing in searches for dark matter and other new physics at the LHC, especially when exploring extreme kinematic regimes involving large Lorentz boosts.

I also explain how innovative theoretical studies of jet substructure have taught us surprising lessons about QCD, revealing new probes of hot dense matter and universal features of gauge theories.

In the past few years we have witnessed a flurry of activity in the field of topological phases of matter. An outstanding theme in the field is the study of the interplay between geometry and topology of many-body wave functions, which has attracted the attention of condensed matter and high-energy physicists. In this talk, I will present the quantum field-theoretic descriptions of the fascinating novel phenomena emergent from intertwined geometry and topology, which are vividly exemplified by the geometric responses in fractional quantum Hall systems. For the strict topological limit, where only the global topology of space matters, the fractional quantum Hall systems are characterized by their universal properties such as fractional quantum Hall conductivity and a degeneracy on surfaces with the topology of a torus. Quite surprisingly, these topological fluids also couple to the geometry and have universal responses to the adiabatic deformations of the background geometry. These responses are given by a Wen-Zee term, Hall viscosity term, and gravitational Chern-Simons term. Through the field-theoretic approaches of the topological fluids, I will for the first time show how to derive all the universal geometric responses. To account for the coupling to the background geometry, I show that the concept of “flux attachment” must be modified in the curved space and use it to derive the responses from Chern-Simons theories for all the known fractional quantum Hall states. I also apply these results to the theory of the anisotropic quantum Hall systems, where the geometric responses play a central role in understanding their universal physics.