Talks

Albert Einstein developed the general theory of relativity 100 years ago as an answer to fundamental problems of contemporary physics. Yet the theory remained a marginal phenomenon of physics, especially in comparison to quantum theory, until the second half of the 20th century. That's when the renaissance in general relativity combined with the rise of relativistic astrophysics, turning general relativity into a key instrument in astrophysics. This talk will trace the genesis of general relativity, look at Einstein's research and the work of many other scientists who contributed to the theory, and show how general relativity eventually became not only a highly active field of research but one of the principal challenges to the conceptual unification of physics.

Thousands of exoplanets are known to orbit nearby stars, with further evidence that every star in our Milky Way Galaxy has planets. Beyond their discovery, a new era of “exoplanet characterization” is underway with an astonishing diversity of exoplanets driving the fields of planet formation and evolution, interior structure, atmospheric science, and orbital dynamics to new depths. The push to find smaller and smaller planets down to Earth size is succeeding and motivating the next generation of space telescopes to have the capability to find and identify planets that may have suitable conditions for life or even signs of life by way of atmospheric biosignature gases. After thousands of years of people wondering “Are we alone?”, we are the first generation in human history to be able to make quantitative progress in answering this age-old question.

In this talk I'll survey the current observational status in cosmology, highlighting recent developments such as results from the Planck satellite, and speculate on what we might achieve in the future. In the near future some important milestones will be exploration of the neutrino sector, and much better constraints on the physics of the early universe via B-mode polarization. In the far future we can hope to measure a variety of cosmological parameters to much higher precision than they are currently constrained.

The Event Horizon Telescope, global array of millimetre telescopes, has now enabled studies of nearby supermassive black holes on sub-horizon length scales. This unprecedented access opens a window onto not only the high-energy astrophysics of black hole accretion and jet formation, but also the nature of gravity in the heretofore unexplored strongly non-linear regime near the black hole horizon. I will summarize the state of the Event Horizon Telescope, what results obtained over the past 7 years, and how a revolution in capability will produce precision tests of strong gravity over the next 2-3 years.

For nearly a century, we have known that the majority of matter in the universe is not luminous. In the past few decades we have come to be certain that this matter is not only not luminous but not made out of any of the particle ever observed in a laboratory. I will describe the ongoing hunt for this matter and the prospects for the discovery in the next decade. I will further discuss recent claims the dark matter may have been discovered in various signals, and prospects for resolving these claims in the next few years. Finally I will touch on the idea of "dark forces," the idea of an expansive dark sector that is much greater than a single dark particle.

Apart from high temperature superconductivity, the cuprate compounds also display fascinating new types of metallic states from which the superconductivity descends. These metals have served as a remarkable laboratory for modern ideas on long-range quantum entanglement and its consequences for the properties of quantum matter. In the low carrier density “pseudogap” regime we observe a metal which is similar in many respects to simple metals like silver; however, there is increasing evidence that the simple metallic character co-exists with more exotic topological order. At higher dopings we have the “strange metal” which differs in almost all respects from simple metals, and has no well-defined quasiparticle excitations. I will describe a mean-field model of a strange metal which, remarkably, yields the Bekenstein-Hawking entropy of charged black holes.

More than 30 years ago, Richard Feynman outlined the visionary concept of a quantum simulator for carrying out complex physics calculations. Today, his dream has become a reality in laboratories around the world. All this has become possible using complex experimental setups of thousands of optical elements, allowing atoms to be cooled to Nanokelvin temperatures, where they almost come to rest. The atoms can then be trapped and manipulated in arrays of millions of microscopic light traps. Such 'light crystals' allow an unprecedented view into the microscopic world of quantum materials and have enabled the most precise atomic clocks to date that are fundamental to next generation timing and navigation applications. In my talk, I will give an introduction how such quantum simulators can be realized at the lowest man-made known temperatures and outline some of their applications ranging from condensed matter physics over statistical physics to high energy physics with table-top experiment.

Emmy Noether was a giant of mathematics whose work tied together two fundamental concepts: conservation laws and symmetries in nature. But who was she, and why does her work still have such impact? Mathematician Peter Olver explores Noether’s life and career, and delves into the curious history of her famous theorems. Physicist Ruth Gregory looks at the lasting impact of Noether’s theorem, and how it connects with the Standard Model and Einstein’s general relativity.

Some of the most violent events in the Universe are accompanied by spectacular warpages of space-time that travel to us in the form of gravitational waves. Gravitational waves were predicted by Einstein's theory of general relativity over a century ago, but scientists have not yet detected them directly. Learn about how we search for these tiny space-time ripples and decode the unique information they carry about mysterious events in space as far back in time as the first moments after the Big Bang.

A new quantum age is dawning in which humans will be able to build and control scalable quantum systems with amazing properties and applications. Aside from enabling revolutionary future technologies, quantum information science is providing powerful new tools for attacking deep problems in fundamental physical science. In particular, the recent convergence of quantum information and quantum gravity is sparking exciting progress on some old and very hard questions.

Determining causal relationships is central to scientific understanding. Knowledge of such relations permit us not only to predict how a system will behave naturally, but also how it would behave under different hypothetical circumstances, including those where we exert control over some component. In the context of quantum theory, the problem of figuring out what causes what is particularly vexing. One of the central results in the foundations of quantum theory, Bell's theorem, can be understood as demonstrating that it is impossible to provide a causal explanation of the correlations that arise for entangled quantum systems without resorting to fine-tuning. Impossible, that is, using the standard framework of causal models. A new quantum notion of causal model, however, holds promise for achieving such an explanation. It also has practical applications, allowing one to infer causal relationships from observed correlations in scenarios where classically one could not. Correlation does not imply causation. Except in a quantum world, where sometimes it does.