Presence of a positive cosmological constant $\Lambda$, however small, introduces unforeseen conceptual issues in all main areas of gravitational physics. I will first illustrate these in the context of cosmology and black holes, and then focus on gravitational waves. In particular, the celebrated “quadrupole formula” that Einstein derived a century ago was generalized to the positive $\Lambda$ case only last … Read More

Slow-roll inflation can become eternal if the quantum variance of the inflaton field around its slowly rolling classical trajectory is converted into a distribution of classical spacetimes inflating at different rates, and if the variance is large enough compared to the rate of classical rolling that the probability of an increased rate of expansion is sufficiently high. Both of these … Read More

Abstract: “I will describe a technique for exact computation of a large class of correlation functions in 3d N=4 gauge theories placed on S^3. In general, N=4 theories on S^3 have interesting supersymmetric sectors, defined by passing to the cohomology of a certain supercharge, and described by an emergent 1d theory. There are two such 1d sectors that are exchanged … Read More

Abstract: I will review the concept of quantum complexity of a state and the related holographic conjectures. I will discuss certain properties of holographic complexity, namely, the structure of divergences, the complexity of formation of a thermal state, and the time dependence of complexity. I will then move to the QFT side and describe our proposal for defining the complexity … Read More