Talks

The Ryu-Takayanagi formula implies that the entropy, a non-linear function of the state, is an observable in the semiclassical limit. This is a general phenomenon in a class of quantum error-correcting codes (QECC), but few specific area operators in the boundary CFT. In this work, I define a specific code in a holographic 2d CFT that includes all thermofield double states with arbitrary amounts of time evolution, but no bulk local degrees of freedom. While the naive area operator vanishes, it is possible to write down an area operator for appropriately classical states; the answer matches with previous results obtained from bulk considerations. Interestingly, this area operator involves an explicit coarse-graining. This suggests a construction for a non-isometric holographic map for these states.

The entanglement entropy for regions in a BMS field theory living at null infinity has been proposed to be holographically dual to certain ‘swing surfaces’ in flat space. We lift this construction to AdS/CFT and revisit both bulk and boundary aspects of this proposal.

In quantum gravity, the gravitational path integral involves a sum over topologies, representing the joining and splitting of multiple universes. To account for topology change, one is led to allow the creation and annihilation of both closed and open universes in a framework often called third quantization or universe field theory. We argue that since topology change in gravity is a rare event, its contribution to late-time physics should be universally governed by a Poisson distribution. In the Fock space of closed baby universes, this Poisson distribution corresponds to the statistics of the number operator in a coherent state, whereas allowing for the creation of asymptotic open universes calls for a non-commutative generalization of a Poisson process. We propose such an operator algebraic framework, called Poissonization, which takes as input the observable algebra and a (unnormalized) state of a quantum system and outputs a von Neumann algebra represented on its symmetric Fock space. Physically, our construction is a generalization of the coherent state vacua of bipartite quantum systems.

We construct algebras of diff-invariant observables in a global de Sitter universe with two observers and a free scalar QFT in two dimensions. In the limit when the observers have infinite mass and are localized along geodesics at the North and South poles, it was shown in previous work (CLPW) that their algebras are mutually commuting type II_1 factors. Away from this limit, we show that the algebras fail to commute and that they are type I non-factors. Physically, this is because the observers' trajectories are uncertain and state-dependent, and they may come into causal contact. We compute out-of-time-ordered correlators along an observer's worldline, and observe a Lyapunov exponent given by 4πβ_dS, as a result of observer recoil and de Sitter expansion. This should be contrasted with results from AdS gravity, and exceeds the chaos bound associated with the de Sitter temperature by a factor of two. We also discuss how the cosmological horizon emerges in the large mass limit and comment on implications for de Sitter holography.

The talk will go over some crucial developments in astronomy over the last hundred years, such as the classification of stars, the distance scale of the universe, the abundance and production of the chemical elements, compact objects like neutron stars and black holes, and many more. Women astronomers had a crucial role in all of these examples

 

In the two sessions we will explore what it means to approach physics through the lens of computation. I’ll introduce some of the ways in which computation has shaped physics in terms of modelling, measurement and also how we learn the subject. No prior programming knowledge is expected. We’ll begin from first principles, using just our hands, some paper, and a few simple rules to build up a system. 

In the second session, we’ll move to a visual programming environment (Tinkercad and Seelab). You’ll use a laptop (preferable) or smartphone to try out basic computational constructs like loops, conditionals, and sensor-based responses. The goal is to begin thinking computationally in a  physics context, and to see how we can even start doing simple experiments by interfacing with real hardware.

In the two sessions we will explore what it means to approach physics through the lens of computation. I’ll introduce some of the ways in which computation has shaped physics in terms of modelling, measurement and also how we learn the subject. No prior programming knowledge is expected. We’ll begin from first principles, using just our hands, some paper, and a few simple rules to build up a system. 
 

In the second session, we’ll move to a visual programming environment (Tinkercad and Seelab). You’ll use a laptop (preferable) or smartphone to try out basic computational constructs like loops, conditionals, and sensor-based responses. The goal is to begin thinking computationally in a  physics context, and to see how we can even start doing simple experiments by interfacing with real hardware.

 Why can’t we predict the behavior of a gas molecule the same way we track a planet? In this talk, we’ll explore why classical and quantum mechanics alone are not enough to explain the messy, complex world around us—and why we need statistical mechanics to bridge the gap between microscopic particles and macroscopic behavior. Along the way, we’ll look at stochastic processes as powerful tools for dealing with randomness and uncertainty in nature. We’ll also touch on big ideas like chaos, self-organization, networks, biological complexity, and even how diseases spread—all from a statistical perspective. This talk aims to give you a fresh way of looking at the world: not as a set of exact rules, but as a dynamic system full of patterns, surprises, and probabilities

We will talk about large scale flows in the atmosphere, containing droplet or particulate matter, such as snow avalanches and pollutant dispersal. Being a late evening lecture, we'll not go into too much of the mathematics, but we'll try to appreciate why these problems are beautiful, hard and important.