The QMAP colloquium aims is to bring high profile speakers to address audiences of both physicists and mathematicians interested in the core topics of the QMAP center. The colloquium series is slated to resume in Fall 2024 after a brief haitus during the pandemic.

## Past colloquia

##### May 24, 2022

**Speaker:** Martin Fraas, UC Davis

**Title:** Quantum Trajectories

**Abstract:** Quantum trajectory models time evolution of a quantum system including a particular measurement strategy. Quantum trajectories were introduced in the 1970s and, in the last decade, became a standard experimental tool to monitor and control quantum systems with few degrees of freedom. In this talk, I will introduce the theory of quantum trajectories, describe the standard experimental setup to realize them in quantum optics, and discuss two model examples.

**Time ****& Location:** 3:30pm, Mathematical Science Building, room 1147. Light refreshment served at 3:15pm before the talk.

Colloquium flyer: QMAP_colloquium_5_24.pdf

Past colloquia

##### May 24, 2019

**Speaker:** Stephen Shenker, Stanford

**Title:** Black holes, random matrices, topological recursion and D-branes

**Abstract:** I will discuss recent progress in understanding gravitational signatures of the discreteness of the energy spectrum of a toy quantum black hole. The black hole is described by the Sachdev-Ye-Kitaev (SYK) model, a quantum mechanical system displaying quantum chaos. The SYK model's low energy limit is given, via gauge/gravity duality, by Jackiw-Teitelboim gravity in 2 spacetime dimensions. This gravitational theory computes Weil-Petersson volumes of the moduli space of Riemann surfaces. Mirzakhani's recursion for these volumes has been related to the Eynard-Orantin topological recursion for a certain matrix integral. The eigenvalues of this matrix are the energies of the black hole, which therefore have random matrix statistics, characteristic of a quantum chaotic system with discrete spectrum. The properties of the eigenvalues are probed by a spacetime analog of a D-brane. Analysis of another type of D-brane yields new large genus asymptotic formulas for Weil-Petersson volumes. This is joint work with Phil Saad and Douglas Stanford.

**Time ****& Location:** 3:10pm, Mathematical Science Building, room 1147. Light refreshment served before the talk.

Colloquium flyer can be downloaded here.

##### March 1, 2019

**Speaker:** Nathan Seiberg, IAS

**Title:** Symmetries, Duality, and the Unity of Physics

**Abstract:** Global symmetries and gauge symmetries have played a crucial role in physics. The idea of duality demonstrates that gauge symmetries can be emergent and might not be fundamental. During the past decades it became clear that the circle of ideas about emergent gauge symmetries and duality is central in different branches of physics including Condensed Matter Physics, Quantum Field Theory, and Quantum Gravity. We will review these developments, which highlight the unity of physics.

**Time & Location**: 4:10pm, Mathematical Science Building, room 1147. Light refreshment served before the talk.

Colloquium flyer can be downloaded here.

##### February 8, 2019

**Speaker:** Robert Wald, Chicago

**Title:** Quantum Superposition of Massive Bodies

**Abstract:** We analyse a gedankenexperiment previously considered by Mari et al. that involves quantum superpositions of charged and/or massive bodies ("particles'') under the control of the observers, Alice and Bob. In the electromagnetic case, we show that the quantization of electromagnetic radiation (which causes decoherence of Alice's particle) and vacuum fluctuations of the electromagnetic field (which limits Bob's ability to localize his particle to better than a charge-radius) both are essential for avoiding apparent paradoxes with causality and complementarity. We then analyze the gravitational version of this gedankenexperiment. We correct an error in the analysis of Mari et al. and of Baym and Ozawa, who did not properly account for the conservation of center of mass of an isolated system. We show that the analysis of the gravitational case is in complete parallel with the electromagnetic case provided that gravitational radiation is quantized and that vacuum fluctuations limit the localization of a particle to no better than a Planck length. This provides support for the view that (linearized) gravity should have a quantum field description.

**Time & Location**: 4:10pm, Mathematical Science Building, room 1147. Light refreshment served before the talk.

Colloquium flyer can be downloaded here.

##### April 11, 2018

**Speaker:** Roberto Emparan, Barcelona

**Title:** Black hole fusion made easy

**Abstract:** The fusion of two black holes --- a signature phenomenon of General Relativity --- is usually regarded as a process so complex that nothing short of a supercomputer simulation can accurately capture it. But this is not quite so – not always. I will explain how the event horizon of the fusion can be found in a very simple way when one of the black holes is much smaller than the other. The construction is not only simple but also accurate, general, and realistic: these fusions are occurring out there, all the time. Remarkably, the ideas and techniques involved are elementary, so the construction can be understood with only a basic knowledge of General Relativity.

**Time & Location**: 3:10pm, Mathematical Science Building, room 1147. Light refreshment served before the talk.

Colloquium flyer can be downloaded here.

##### February 27, 2018

**Speaker:** Sergei Gukov, Caltech

**Title:** Conformal Symmetry and 4-Manifolds

**Time & Location**: 3:10pm, Mathematical Science Building, room 1147. Light refreshment served before the talk.

Colloquium flyer can be downloaded here.

##### November 21, 2017

**Speaker:** Nicolai Reshetikhin, UC Berkeley

**Title:** Superintegrable Systems

**Time & Location**: 11:00am, Mathematical Science Building, room 1147. Coffee before the talk and a lunch afterwards.

Colloquium flyer can be downloaded here.

##### October 24, 2017

**Speaker:** Maxim Kontsevich, IHES Paris

**Title:** Quaternionic D-branes

**Time & Location**: 10:30am (refreshment at 10:15am), Mathematical Science Building, room 1147.

Colloquium flyer can be downloaded here.

##### October 17, 2017

**Speaker:** Nima Arkani-Hamed, IAS Princeton

**Title:** Spacetime, Quantum Mechanics and Positive Geometry

**Time & Location**: 10:30am (refreshment at 10:15am, reception after colloquium), Mathematical Science Building, room 1147.

**Abstract:** Spacetime and Quantum Mechanics form the pillars of our understanding of modern physics, but there are several indications that these concepts are approximate and must emerge from deeper principles, undoubtedly involving new mathematics. In this talk I will describe some emerging ideas along these lines, and present a new formulation of some very basic physics-- fundamental to particle scattering and to cosmology--not following from quantum evolution in space-time, but associated with simple new mathematical structures in "positive geometry". In these examples we can concretely see how the usual rules of space-time and quantum mechanics can arise, joined at the hip, from fundamentally geometric and combinatorial origins.

Colloquium flyer can be downloaded here.