Sommerfeld Lecture Series (ASC)
48 episodes - English - Latest episode: 10 months ago -Every semester the Arnold Sommerfeld Center for Theoretical Physics invites a distinguished theoretical physicist in order to present a short series of lectures with increasing level of specialization. Usually it includes a public talk for a general audience, a theory colloquium and a specialized seminar.
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Episodes
Hirosi Ooguri: Symmetry Resolution at High Energy
June 30, 2023 11:16 - 1 hour - 574 MB VideoThe density of states of a unitary quantum field theory is known to have a universal behavior at high energy. In two dimensions, this behavior is described by the Cardy formula. When the theory has symmetry, it is interesting to find out how the Hilbert space is decomposed into irreducible representation of the symmetry. In this talk, I will derive universal formulas for the decomposition of states at high energy with respect to both internal global symmetry and spacetime symmetry. The formul...
Biophysics Seminar: Statistical Physics in Biology: Twisting transitions for DNA, and Ising Models for cell Membranes
June 30, 2023 09:39 - 1 hour - 1.05 GB VideoThe theory of phase transitions splits between abrupt transitions (nucleation and growth, critical droplets) and continuous transitions (scaling and universality). I’ll discuss wonderful biophysics examples for each: Michelle Wang’s twisting single molecules of DNA, and with Sarah Veatch’s discovery of universal Ising critical fluctuations in living cell membranes. (1) Plectonemes are the helically wound loops formed in garden hoses and electrical cords when they are overtwisted. Wang's group...
Condensed Matter Theory Seminar: Electronic Squeezing of Pumped Phonons: Negative U and Transient Superconductivity
June 30, 2023 09:39 - 1 hour - 1.06 GB VideoAdvances in light sources and time resolved spectroscopy have made it possible to excite specific atomic vibrations in solids and to observe the resulting changes in electronic properties. I argue that in narrow-band systems the dominant symmetry-allowed coupling between electron density and dipole active modes implies an electron density-dependent squeezing of the phonon state which provides an attractive contribution to the electron-electron interaction, independent of the sign of the bare ...
Condensed Matter Theory Seminar: Shining Light on Transition Metal Oxides: Resilient Quasiparticles and the Unveiling of the Hidden Fermi Liquid
June 30, 2023 09:39 - 1 hour - 1.03 GB VideoStrongly correlated metals exhibit anomalous transport properties which have puzzled condensed matter physicists for many years. They are characterized by large resistivities which exceed the Mott Ioffe Reggel limit and large thermoelectric responses, which cannot be explained in terms of standard Fermi liquid quasiparticles. Dynamical Mean Field Theory (DMFT) calculations [1,2] carried out on a doped one band Hubbard model suggest that this behavior originate in the strong temperature depend...
Fields and Strings Seminar: Duality in 2 + 1 Dimensions
June 30, 2023 09:39 - 1 hour - 1.06 GB VideoA combination of ideas originating from Condensed Matter physics, Supersymmetric Field Theory, and AdS/CFT has led to a detailed web of conjectured dualities. These relate the long distance behavior of different short distance theories. These dualities clarify a large number of confusing and controversial issues in Condensed Matter physics and in the study of 2+1 dimensional quantum field theory.
Fields and Strings Seminar: Holographic Quantum Codes
June 30, 2023 09:39 - 1 hour - 1.13 GB VideoTwo of the most amazing ideas in physics are the holographic principle and quantum error correction. The holographic principle asserts that all the information contained in a region of space is encoded on the boundary of the region, albeit in a highly scrambled form. Quantum error correction is the foundation of our hope that large-scale quantum computer can be operated to solve hard problems. I will argue that these two ideas are closely related, and will describe quantum codes which realize...
Fields and Strings Seminar: What is dark matter?
June 30, 2023 09:39 - 1 hour - 1.56 GB VideoI review what we know about dark matter right now and some hints about its nature. In particular, I discuss candidates away from the conventional WIMP (Weakly Interactive Massive Particle) paradigm.
Hirosi Ooguri: Constraints on Quantum Gravity
June 30, 2023 09:39 - 1 hour - 823 MB VideoAlthough predictions of quantum gravity are typically at extremely high energy, several non-trivial constraints on its low energy effective theory have been found over the last decade or so. I will start by explaining why the unification of general relativity and quantum mechanics has been difficult. After introducing the holographic principle as our guide to the unification, I will discuss its use in finding constraints on symmetry in quantum gravity. I will also discuss other conjectural co...
Public Lecture: Adventures of an Idea – the Life and Travels of Maxwell’s Demon
June 30, 2023 09:39 - 1 hour - 1.62 GB VideoIn a letter written in 1867, James Clerk Maxwell described a hypothetical creature: a “neat-fingered being” capable of separating fast molecules from slow ones. Maxwell mused that such a creature would seem to violate the second law of thermodynamics, which had recently been enunciated by Rudolf Clausius and is now a pillar of our understanding of the natural world. Over the past century and a half, that hypothetical creature – Maxwell’s demon – has wandered through the thoughts of eminent sc...
Public Lecture: Crackling Noise
June 30, 2023 09:39 - 1 hour - 1.02 GB VideoA piece of paper or candy wrapper crackles when it is crumpled. A magnet crackles when you change its magnetization slowly. The earth crackles as the continents slowly drift apart, forming earthquakes. Crackling noise happens when a material, when put under a slowly increasing strain, slips through a series of short, sharp events with an enormous range of sizes. There are many thousands of tiny earthquakes each year, but only a few huge ones. The sizes and shapes of earthquakes show regular p...
Public Lecture: From Atoms to Novel Materials: A Quantum Engineer's Dream
June 30, 2023 09:39 - 1 hour - 762 MB VideoWhich property of a material is more familiar to us than its color? And yet, the strange laws of quantum mechanics, which rule atoms, electrons and photons, are key to the understanding of this most beautiful feature! The invention and engineering of novel materials has shaped human civilization, from the Bronze age to the Silicon age. This lecture is an invitation to explore materials down to the scale of their intimate constituents – atoms and electrons. We'll address questions such as: do ...
Public Lecture: How to tell quantum condensates from pendulul clocks?
June 30, 2023 09:39 - 1 hour - 524 MB VideoDuring more than 100 years of its history Quantum Mechanics passed all of the experimental checks and transformed itself from a counterintuitive concept to the undisputable foundation of the modern physics. Along with this it did not lose its ability to surprise and still allows for new astonishing discoveries such as Bose-Einstein condensation of ultracold gases. Manifestations of the quantum mechanics on the macroscopic scales are especially impressive. In recent years the interest in conde...
Public Lecture: Many Worlds in One
June 30, 2023 09:39 - 1 hour - 402 MB VideoRecent developments in cosmology suggest that the big bang was not a unique event in the cosmic history. Other big bangs constantly erupt in remote parts of the uni- verse, producing new worlds with great variety of physical properties. Some of these worlds are similar to ours, while others are strikingly different and even obey different laws of physics. I will discuss the origin of this new worldview, its possible observational tests, and some of its bizarre implications.
Public Lecture: On the Possibility of Evolutionary Forecasting
June 30, 2023 09:39 - 1 hour - 1.09 GB VideoWhen we think about evolution, it is typically in the context of natural history, seeking an explanation for the amazing diversity of life. Yet evolution is not only the matter of the past, but an ongoing dynamical process linking the past with the future. Evolutionary dynamics is particularly apparent in rapidly mutating microbes and viruses. For example, the virus causing seasonal flu continuously evolves to escape human immunity generated by previous infections: because of this process, we...
Public Lecture: Quantum Beauty
June 30, 2023 09:39 - 1 hour - 1.34 GB VideoDoes the world embody beautiful ideas? Pythagoras and Plato intuited that it should, Newton and Maxwell showed, in impressive examples, how it could. Modern physics demonstrates, in depth and detail, that it does. I will narrate, through notable examples, how the concept of beauty in physical law has evolved – and how it continues to guide our quest for ultimate understanding.
Public Lecture: Quantum Computing and the Entanglement Frontier
June 30, 2023 09:39 - 1 hour - 1.1 GB VideoThe quantum laws governing atoms and other tiny objects seem to defy common sense, and information encoded in quantum systems has weird properties that baffle our feeble human minds. John Preskill will explain why he loves quantum entanglement, the elusive feature making quantum information fundamentally different from information in the macroscopic world. By exploiting quantum entanglement, quantum computers should be able to solve otherwise intractable problems, with far-reaching applicatio...
Public Lecture: Quantum Universe
June 30, 2023 09:39 - 1 hour - 1.59 GB VideoWhere do we come from? Science is making progress on this age-old question of humankind. The Universe was once much smaller than the size of an atom. Small things mattered in the small Universe, where quantum physics dominated the scene. To understand the way the Universe is today, we have to solve remaining major puzzles. The Higgs boson that was discovered recently is holding our body together from evaporating in a nanosecond. But we still do not know what exactly it is. The mysterious dark...
Public Lecture: Superconductivity
June 30, 2023 09:39 - 1 hour - 1 GB VideoSuperconductivity, the ability of certain materials to conduct electricity with no resistance whatsoever, has fascinated scientists since its discovery by Kammerlingh-Onnes in 1911. While much has been understood, the question of predicting which materials will become superconducting, and at what temperatures, remains one of the grand challenges of modern materials theory. This talk will outline the evolution of our understanding as the subject has progressed from its primitive beginnings thr...
Public Lecture: The Frontiers of Fundamental Physics
June 30, 2023 09:39 - 1 hour - 1.03 GB VideoIn recent decades, physicists and astronomers have discovered two beautiful Standard Models, one for the quantum world of extremely short distances, and one for the universe as a whole. Both models have had spectacular success, but there are also strong arguments for new physics beyond these models. In this lecture, we will review these models, their successes and their shortfalls. We will describe how experiments in the near future could point to new physics suggesting a profound conceptual ...
Public Lecture: The Principle of Least Action, from the “Vis-viva” to Quantum Black Holes
June 30, 2023 09:39 - 1 hour - 1.22 GB VideoThe Principle of Least Action is both profound and practical. Since its first formulation by Maupertuis and Euler nearly three centuries ago, the Principle has been, and continues to be, a formidable battlehorse for penetrating unchartered territory in theoretical physics. The Principle, its connection with, and implications for, our ideas of symmetry, space, time, quantum mechanics, thermodynamics and gravitation, are glanced at.
Public Lecture: The quantum phases of matter
June 30, 2023 09:39 - 1 hour - 511 MB VideoIn many modern materials, electrons quantum‐entangle with each other across long distances, and produce new phases of matter, such as high temperature super‐conductors. We face the challenge of describing the entanglement of 10^{23} electrons, which is being met by many ideas, including some drawn from string theory.
Public Lecture: The Quest for High Temperature Superconductivity
June 30, 2023 09:39 - 1 hour - 1.04 GB VideoSuperconductivity is a state of matter where electrons can flow without resistance and where magnetic fields are expelled. It was discovered serendipitously more than a hundred years ago. Today, superconductors are essential components of medical imaging devices as well as high energy particles accelerators. Understanding this phenomena was one of the greatest intellectual challenges of the twentieth century. A dramatic advance was provided by the BCS (Bardeen Cooper Schrieffer) theory 45 yea...
Public Lecture: The Unreasonable Effectiveness of Quantum Physics in Mathematics
June 30, 2023 09:39 - 1 hour - 1.49 GB VideoMathematics has proven to be "unreasonably effective" in understanding nature. The fundamental laws of physics can be captured in beautiful formulae. Remarkably, ideas from quantum theory turn out to carry tremendous mathematical power as well, even though we have little daily experience dealing with elementary particles. The bizarre world of quantum physics not only represents a more fundamental description of nature than what preceded it, it also provides a rich context for modern mathemati...
Solid State Theory Seminar: Death of a Quasiparticle: Strong Correlations from Hund's Coupling
June 30, 2023 09:39 - 1 hour - 731 MB VideoAccording to the Landau description of Fermi liquids, low- energy excitations in metals are constructed out of quasiparticles – long-lived excitations which have the same quantum numbers as those of an electron in vacuum. In metals with strong correlations however, quasiparticles become fragile: they are destroyed above a characteristic energy or temperature scale, the quasiparticle coherence scale. This energy scale can be remarkably low, even in materials which are not close to a Mott metal...
Solid State Theory Seminar: Dipole Excitations in 2D insulators. Quantum Levy flights
June 30, 2023 09:39 - 1 hour - 562 MB VideoThis talk is devoted to quantum propagation of dipole excitations in two dimensions in the presence of disorder. This problem differs from the conventional Anderson localization due to existence of long range hops. We found that the critical wave functions of the dipoles always exist which manifest themselves by a scale independent diffusion constant. If the system is T-invariant the states are critical for all values of the parameters. Otherwise, there can be a “normal metal - perfect metal"...
Solid State Theory Seminar: Quantum phase transitions, and the high temperature superconductors
June 30, 2023 09:39 - 1 hour - 601 MB VideoThe last three decades have witnessed the discovery of many new superconductors, with properties dramatically different from the conventional low temperature superconductors described by the Bardeen-Cooper- Schrieffer theory. These new superconductors can have much higher critical temperature, and all display antiferromagnetism in their phase diagrams. I will introduce the theory of quantum phase transitions, and use it to interpret recent experiments on these materials.
Sommerfeld Theory Colloquium: Looking for Cosmic Strings
June 30, 2023 09:39 - 1 hour - 566 MB VideoCosmic strings are linear defects that could be formed at a phase transition in the early universe. Strings are predicted in a wide class of particle physics models. In particular, fundamental strings of superstring theory can have astronomical dimensions and play the role of cosmic strings. I will discuss recent progress in understanding the evolution of cosmic strings and possible ways of detecting them.
Sommerfeld Theory Colloquium: Many- Body Anderson Localization
June 30, 2023 09:39 - 1 hour - 615 MB VideoLocalization of the eigenfunctions of quantum particles in a random potential was discovered by P.W. Anderson more than 50 years ago in connection with spin relaxation and charge transport in disordered solids. Later experimentally was realized localization of other quantum particles and classical waves: light, microwaves, sound, cold atoms. At the same time it became clear that the domain of applicability of the concept of localization is much broader. In particular, it can be extended to va...
Sommerfeld Theory Colloquium: Quantum Matter with Strong Correlations
June 30, 2023 09:39 - 1 hour - 705 MB VideoFrom copper-oxide superconductors to rare-earth compounds, materials with strong electronic correlations have focused enormous attention over the last two decades. Solid-state chemistry, new elaboration techniques and improved experimental probes are constantly providing us with examples of novel materials with surprising electronic properties, the latest example being the recent discovery of iron-based high-temperature superconductors. In this colloquium, I will emphasize that the classic pa...
Sommerfeld Theory Colloquium: Sloppy Models and How Science Works
June 30, 2023 09:39 - 1 hour - 1.08 GB Video“With four parameters I can fit an elephant; with five I can make it wag its tail.” Systems biology models of the cell have an enormous number of reactions between proteins, RNA, and DNA whose rates (parameters) are hard to measure. Models of climate change, ecosystems, and macroeconomics also have parameters that are hard or impossible to measure directly. If we fit these unknown parameters, fiddling with them until they agree with past experiments, how much can we trust their predictions? M...
Sommerfeld Theory Colloquium: What can string theory teach us about condensed matter physics?
June 30, 2023 09:39 - 1 hour - 561 MB VideoString theory was originally constructed as a unification of the quantum field theory of elementary particles with Einstein's theory of gravitation. Unexpectedly, it has led to the discovery of new "dualities" which have given us a new perspective on quantum field theories not coupled to gravity. Some of the latter theories are relevant to the strongly-interacting quantum many body problems of condensed matter physics. I will survey some of the challenging open problems associated with conden...
Statistical Physics Seminar: Quantum Impulse Control
June 30, 2023 09:39 - 1 hour - 1.49 GB VideoThe quantum adiabatic theorem governs the evolution of a wavefunction under a slowly time-varying Hamiltonian. I will consider the opposite limit of a Hamiltonian that is varied impulsively: a strong perturbation U(x,t) is applied over a time interval of infinitesimal duration e->0. When the strength of the perturbation scales like 1/eˆ2, there emerges an interesting dynamical behavior characterized by an abrupt displacement of the wave function in coordinate space. I will solve for the evolu...
Theory Colloquium: Meeting Dirac’s Challenge: modern approaches to the Correlated Electron Problem
June 30, 2023 09:39 - 1 hour - 1.05 GB VideoThis talk will present an overview of recent progress towards a solution of one of the grand-challenges of modern science: understanding the properties of interacting electrons in molecules and solids. After an introduction to the physics I will argue our theoretical understanding of a basic model system, the two dimensional Hubbard model, has reached the level that we can say with confidence that its superconducting properties capture key aspect of the high-Tc superconductivity in copper-oxi...
Theory Colloquium: Quantum Information and Spacetime
June 30, 2023 09:39 - 1 hour - 1.18 GB VideoAside 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.
Theory Colloquium: Scaling Down the Laws of Thermodynamics
June 30, 2023 09:39 - 1 hour - 1.65 GB VideoThermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems also exhibit “thermodynamic-like” behavior – for instance, biomolecular motors convert chemical fuel into mechanical work. To what extent can the laws of thermodynamics be scaled down to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describ...
Theory Colloquium: Symmetries, Duality, and the Unity of Physics
June 30, 2023 09:39 - 1 hour - 1.02 GB VideoGlobal 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.
Theory Colloquium: The Life and Death of Turbulence
June 30, 2023 09:39 - 1 hour - 1.53 GB VideoTurbulence is the last great unsolved problem of classical physics. But there is no consensus on what it would mean to actually solve this problem. In this colloquium, I propose that turbulence is most fruitfully regarded as a problem in non-equilibrium statistical mechanics, and will show that this perspective explains turbulent drag behavior measured over 80 years, and makes predictions that have been experimentally tested in 2D turbulent soap films. I will also explain how this perspective...
Theory Colloquium: Topological Gravity and Matrix Models
June 30, 2023 09:39 - 1 hour - 1.65 GB VideoRandom matrix models are ubiquitous in physics and have been studied from many perspectives. One important application is producing exactly solvable toy models of quantum gravity and string theory. These models relate to deep mathematical structures of the moduli space of Riemann surfaces. Recent work has extended these models to open strings and surfaces with boundaries. This generalization is less straightforward that one imagines and involves the introduction of additional degrees of freed...
Theory Colloquium: Towards Material Design Using Strongly Correlated Electron Materials
June 30, 2023 09:39 - 1 hour - 1.04 GB VideoOur understanding of simple solids, is firmly grounded on the Fermi liquid concept and powerful computational techniques built around the density functional theory. These ideas form the basis of our “standard model” of solid state physics and have provided us with an accurate description of many materials of great technological significance. Correlated electron systems are materials for which the the standard model of solid state physics fails dramatically. The best known example being the co...
Theory Colloquium: When a Symmetry Breaks
June 30, 2023 09:39 - 1 hour - 1.51 GB VideoSpontaneous Symmetry Breaking is a very universal concept applicable for a wide range of subjects: crystal, superfluid, neutron stars, Higgs boson, magnets, and many others. Yet there is a variety in the spectrum of gapless excitations even when the symmetry breaking patterns are the same. We unified all known examples of internal symmetries in a single-line Lagrangian of the low-energy effective theory. In addition, we now have a better understanding of what happens with spacetime symmetries...
Thibault Damour: 100 Years of General Relativity
June 30, 2023 09:39 - 1 hour - 528 MB VideoIn November 2015, Albert Einstein finalized a new theory of gravitation, General Relativity (GR), which describes gravitation as a deformation of the structure of space-time. It took many years of conceptual deepening and observational discoveries to fully grasp several of the most novel predictions of GR (gravitational waves, black holes, cosmological expansion). GR is the current standard model for the gravitational interaction, and plays a crucial role in the description of many physical s...
Thibault Damour: Black Hole Binary Dynamics from Classical and Quantum Gravitational Scattering
June 30, 2023 09:39 - 1 hour - 683 MB VideoGravitational wave signals from coalescing binary black holes are detected, and analyzed, by using large banks of template waveforms. The construction of these templates makes an essential use of the analytical knowledge of the motion and radiation of gravitationally interacting binary systems. A new angle of attack on gravitational dynamics consists of considering (classical or quantum) scattering states. Modern amplitude techniques have recently given interesting novel results. These result...
Thibault Damour: Gravitational Waves and Binary Black Holes
June 30, 2023 09:39 - 1 hour - 1.41 GB VideoThe observation of gravitational wave signals by the two interferometers of the Laser Interferometer Gravitational-Wave Observatory (LIGO), and by the Virgo interferometer, has brought the first direct evidence for the existence of black holes, and has also been the first observation of gravitational waves in the wave-zone. After reviewing the historical path that led to our understanding of gravitational waves and black holes, the colloquium will present the theoretical developments on the ...
What can Theoretical Physics tell us about the Origin and Evolution of Early Life?
June 30, 2023 09:39 - 1 hour - 1.61 GB VideoLife on Earth is wonderfully diverse, with a multitude of life forms, structures and evolutionary mechanisms. However, there are two aspects of life that are universal --- shared by all known organisms. These are the genetic code, which governs how DNA is converted into the proteins making up your body, and the unexpected left-handedness of the amino acids in your body. One would expect that your amino acids were a mixture of left and right-handed molecules, but none are right handed! In this...
Yaron Oz: Entanglement, Chaos and Quantum Computation
June 30, 2023 09:39 - 1 hour - 754 MB VideoWe consider information spreading measures in randomly initialized variational quantum circuits and introduce entanglement diagnostics for efficient computation. We study the correlation between quantum chaos diagnostics, the circuit expressibility and the optimization of the control parameters.
Yaron Oz: The Quantum Universe: Information, Communication and Computation
June 30, 2023 09:39 - 1 hour - 637 MB VideoThe amazing and mysterious laws of the quantum world will be outlined: superposition, entanglement and no cloning. Their impact on science and technology will be discussed, including quantum teleportation, secure quantum communication, quantum money, powerful quantum algorithms and quantum machine learning.
ASC Theory Colloquium: Physics and Geometry of Morphogenesis
June 30, 2023 09:39 - 1 hour - 1.26 GB VideoOne hundred years ago, D’Arcy Thompson – a nineteenth century polymath, working at the turn of the twentieth century – wrote a beautiful monograph, “On Growth and Form”, in which he pondered the geometry of living forms and how it emerges in the process of Morphogenesis. Thompson was ahead of his time. Genetics and Developmental Biology have since come a long way in elucidating the general and particular aspects of Morphogenesis, uncovering the key genes and molecules that underlie the proces...
Yaron Oz: Unraveling Turbulence: Modern Viewpoints on an Unsolved Problem
June 30, 2023 09:39 - 1 hour - 1.07 GB VideoFluid turbulence is a major unsolved problem of physics exhibiting an emergent complex structure from simple rules. We will briefly review the problem and discuss three avenues towards its solution: field theory, holography and machine learning.