Sommerfeld Theory Colloquium (ASC)

Sommerfeld Theory Colloquium, The physics of elementary particles is governed by symmetries. A particular symmetry stands out: the one between left and right, called parity. Its breaking in beta decay created a bombshell more than fifty years ago, and ultimately led to the creation of the Standard Model of particle interactions, whose final crowning confirmation is to be provided by the Large Hadron Collider (LHC) at CERN. The Standard Model is based on the premise of parity being broken al- ways, at all energies. I argue, on the contrary, that in nature left-right symmetry is fundamental, and that at high energies of the LHC one could actually see its restoration in full glory. I show how this would probe the nature of neutrino, through the spectacular signatures of lepton number violation.

Sommerfeld Theory Colloquium, Reflection positivity is a useful tool in statistical mechanics and con- densed matter physics. A recent application is to the determination of the possible distortions of the hexagonal graphene lattice. Other applications, such as to potential theory, the flux-phase problem, Peierls instability and stripe formation, will also be given.

Sommerfeld Theory Colloquium, Much of condensed matter physics is concerned with understanding how different kinds of order emerge from interactions between a large number of simple constituents. In ordered phases such as crystals, magnets, and superfluids, the order is understood through ”symme- try breaking”: in a crystal, for example, the continuous symmetries of space under rotations and translations are not reflected in the ground state. A major discovery of the 1980s was that electrons confined to two dimensions and in a strong magnetic field exhibit a completely different, ”topological” type of order that underlies the quantum Hall effect.

In the past few years, we have learned that topological order also occurs in some three-dimensional materials, dubbed ”topological in- sulators”, in zero magnetic field. Spin-orbit coupling, an intrinsic property of all solids, drives the formation of the topological state. This talk will explain what topological order means, how topologi- cal were predicted and discovered, and how they realize the ”axion electrodynamics” studied by particle physicists in the 1980s. Some possible applications of these new materials are discussed in closing.

Sommerfeld Theory Colloquium, In collisions of ultra-intense laser-pulse with relativistic electrons as well as in ultra relativistic heavy ion collisions at RHIC and at LHC it is possible to probe critical acceleration a=mc^3/hbar. The behavior of a particle undergoing critical acceleration challenges the limits of the current understanding of basic interactions: little is known about this physics frontier; both classical and quantum physics will need further development in order to be able to address this newly accessible area of physics. The problem of critical acceleration is closely connected to strong field particle production, Mach's Principle, Unruh and Hawking radiation.

Sommerfeld Theory Colloquium, In this lecture I propose to discuss some issues concerning the founda- tions of quantum mechanics and its interplay with space-time physics. I start by clarifying the distinction between ’realistic theories’ and ’probabilistic theories’ of Nature and sketch how the latter can often be viewed as ’deformations’ of the former. I then briefly recall some of the intriguing features of atomistic Quantum Mechanics, which belongs to the second class of theories. I attempt to describe, in con- ceptual terms, what it is that Quantum Mechanics predicts about Nature when appropriate experiments are done. I try to sketch some implications of this discussion for our views of space and time. I will conclude by sketching some recent results on the ’effective quantum dynamics’ of Open Systems, in particular on ’Quantum Brownian Motion’.

Quantum Criticality, High Tc Superconductivity and the AdS/CFT Correspondence of String Theory , The central mystery in quantum matter is the general nature of mat- ter formed from fermions. The methods of many body quantum physics fail and one can only rely on the phenomenological Fermi- liquid and BCS theories. However, in heavy fermion systems and cuprates one deals with non Fermi-liquid quantum critical metals, and to understand the superconductivity one needs to understand these normal states first. Remarkably, it might well be that the mathematics of string theory is capable of describing such states of fermion matter. The AdS/CFT correspondence translates this problem into an equivalent general-relativity problem involving the propagation of classical fields in an Anti-de-Sitter space-time with a black hole in its center. This development started with the demon- stration that AdS/CFT predicts correctly the low viscosity of the quark-gluon plasma of the Brookhaven heavy ion collider. In 2007 it was realized that it could have relevance to high Tc superconductors but only last year the focus shifted to the way AdS/CFT processes fermions, creating much excitement: it appears that both emergent heavy Fermi-liquids and non Fermi-liquids can be gravitationally encoded, as well as holographic superconductors having suggestive traits in common with the real life high Tc variety.

Imaging Astrophysical Turbulent Convection and Dynamo Action in the Sun, The Sun is a most remarkable object: it is filled with vibrantly evolv- ing magnetic fields, well-mixed hierarchically-arranged turbulent con- vective cells, and also poorly-mixed sunspots that persist with im- punity. Solar variability has direct consequences for the earth and space weather, an important reason to develop an appreciation for the physics of the solar cycle (dynamo).

Direct observation of the solar subsurface is impossible due to the high degree of optical scattering by the partially ionized plasma that inhabits the near-surface layers of the Sun. The deepest part of the Sun visible to us, known as the photosphere (also the solar surface), appears as a roiling, turbulent, radiative, magnetized, convecting plasma. At first glance, it would seem therefore that subtle ques- tions relating to the subsurface constitution of the Sun seem com- pletely unanswerable and the interior properties unknowable. How- ever, analogous to geoseismology, a great deal can be gleaned about the internal structure and dynamics of the Sun by carefully observ- ing and analyzing the surface wavefield. This has been made possible over the last few decades through the development and application of techniques of helioseismology.

In this talk I will outline some of the major results in this area over the last two decades and discuss some recent developments pertaining to the properties of turbulence in the deep-convection zone of the Sun.

Gravitational Waves from Coalescing Binary Black Holes: Theoretical and Experimental Challenges, A network of ground-based interferometric gravitational wave detectors (LIGO/VIRGO/GEO/...) is currently taking data near its planned sensitivity. Coalescing black hole binaries are among the most promising, and most exciting, gravitational wave sources for these detectors. The talk will review the theoretical and experimental challenges that must be met in order to successfully detect gravitational waves from coalescing black hole binaries, and to be able to reliably measure the physical parameters of the source (masses, spins, ...).

The apparent crisis of black holes inconsistency with foundational physical principles provides a sharp focus for the conflict between quantum mechanics and classical spacetime. Various resolutions have

been proposed; a very plausible one is that small interactions can transfer sufficient information between the black hole and outgoing radiation, with a quantum enhancement from the enormous number of black hole states. Such interactions must however violate conventional notions of locality, perhaps as a symptom of the more basic subtlety of information localization in quantum gravity, and hinting at aspects of the fundamental structure of quantum gravity. An intriguing question is whether further clues can be found from new observational windows on black holes.

The apparent crisis of black holes inconsistency with foundational physical principles provides a sharp focus for the conflict between quantum mechanics and classical spacetime. Various resolutions have

been proposed; a very plausible one is that small interactions can transfer sufficient information between the black hole and outgoing radiation, with a quantum enhancement from the enormous number of black hole states. Such interactions must however violate conventional notions of locality, perhaps as a symptom of the more basic subtlety of information localization in quantum gravity, and hinting at aspects of the fundamental structure of quantum gravity. An intriguing question is whether further clues can be found from new observational windows on black holes.