School of Mathematics

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Mr. Joan Simon

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Research Interests

The most important driving force in my research is the understanding of spacetime. This involves learning what it is made of, how emerges from a more fundamental (discrete) nature and includes understanding the meaning and origin of time.

This is why I am interested in black holes, resolution of singularities and thermodynamics of horizon (null) hypersurfaces. In more modern language, I am interested in holography and duality.

I am currently interested in the interplay between holography (mainly through the AdS/CFT correspondence), quantum information & computation, and condensed matter physics, through tensor networks and MERA, to explore the relevance of quantum entanglement to describe the intrinsic fabric of spacetime. This should allow us to improve our understanding of what quantum gravity is, and to extend our ideas to asymptotically flat and cosmological spacetimes, where our success has been poorer.

In the past, I have worked on a number of topics, including : -Toy models for Big Bang singularities using lorentzian orbifolds in string theory, both in flat space and in the AdS/CFT correspondence. I also studied possible resolution of these singularities using higher spin theories.

- Physics of closed timelike curves in string theory.

- Cosmology : constraints on the red shift dependence of the dark energy potential & string theory large volume constructions relating cosmological observables to UV completion parameters.

- The origin of gravitational thermodynamics, its relation to the fuzzball programme, and its connection to typicality in more mathematical approaches to the foundations of statistical mechanics.

- Construction of non-BPS extremal black holes and their microscopic description.

- Microscopics of extremal black holes in terms of chiral CFTs and their relation to Kerr/CFT.

- Brief explorations of AdS/CFT applications to condensed matter physics : helical Luttinger liquids and strongly coupled zig-zag transitions.

- Flat holography in 3d and the power of the BMS group.

- 2d CFT calculations of entanglement entropy, mutual information and calculations of scrambling time when locally perturbing a thermal state, together with their holographical bulk descriptions.

Research Groups

Current and Recent PhD Students

Andrius Stikonas Maria Johnstone

Recent Conference and Workshop Involvement

"Gravitational aspects in string theory", Pre-Strings held at Granada (Spain), from June 17th to June 22nd (2007).

"Gravitational thermodynamics and the quantum nature of spacetime", workshop held in Edinburgh, from June 16th-20th (2008).

KITP programme "Bits, Branes and black holes", Santa Barbara (USA), March-May 2012.

KITP conference "Black holes & information", Santa Barbara (USA), May 15-19th 2012.

Workshop "Quantum aspects of Black holes", Seoul, Korea, January 7-11th, 2013.

Workshop "String Theory", Benasque (Spain), July 1-15th, 2013

Workshop on "Flat holography", Stony Brook, Simons' center, April 4-8th 2016.

Biographical Statement

I was born in Barcelona (Spain) on a September 23rd, one sunday morning, a few hours before Barcelona (the team of my heart) defeated Espanyol by 3-0. Some hours later my father registered me as an official supporter, before being registered in the social security. I believe this still describes rather accurately who I am and who I will be. After that, I enjoyed playing basketball and hiking in the Pyrenees, before deciding that I wanted to devote my life to the understanding of nature at its most fundamental level (theoretical physics). Fortunately, being a string theorist did not prevent me from learning some of the most fundamental truths of our existence (not necessarily scientifical).

Education Background

Undergraduate studies in Physics in Barcelona. Ph D in physics in Barcelona.

Previous Employment

Three year postdoc at the Weizmann Institute in Israel, from october 2000 to august 2003. Three year postdoc at the University of Pennsylvania, in Philadelphia, from september 2003 to august 2006. One year postdoc at the University of California in Berkeley, from september 2006 to july 2007.