Sommerfeld Theory Colloquium (ASC)

Various aspects of lattice gauge theory will be briefly discussed including, general principles, sources of systematic errors, dynamical fermions, QCD phenomenology, the FLAG project and, if time allows, some applications of lattice theory to other non-perturbative BSM phenomena.

The role of Type Ia supernovae in observational cosmology has evolved from being ”avant-garde” in the early 1990’s until today’s mature status of precision cosmology. Several large transient surveys have been detecting supernovae routinely, near and far, with the aim of probing what is causing the accelerated expansion of the Universe. With time, the focus has changed towards addressing the intric...

Sommerfeld Theory Colloquium

To pinpoint the microscopic mechanism for superconductivity has proven to be one of the most outstanding challenges in the physics of correlated quantum matter. Thus far, the most direct evidence for an electronic pairing mechanism is the observation of a new symmetry of the order-parameter, as done in the cuprate high-temperature superconductors. Like distinctions based on the symmetry of a local...

I will review the basic defi�nitions and ideas of the twistor program for fundamental physics, as started by Roger Penrose around 1970. I will give particular attention to certain conformally invariant struc- tures involving deformed helicities, relevant to scattering amplitudes for massless �elds. These played a role in Penrose's earliest contour integral expressions, but have more recently been...

We review the current status of measurements of the spectrum, an isotropy and polarization of the CMB, and their impact on cos- mology. We show that there is still a large discovery potential in these measurements, complementing and synergic to other cosmology observations. We also describe a selection of new measurement eff�orts, including high precision measurements of CMB polarization with grou...

The hard-disk model has exerted outstanding influence on computational physics and statistical mechanics. Decades ago, hard disks were the first system to be studied by Markov-chain Monte Carlo methods and by molecular dynamics. It was in hard disks, through numerical simulations, that a two-dimensional melting transition was first seen to occur even though such systems cannot develop long-range c...

All flows show a transition from a laminar phase to a turbulent one for sufficiently high flow speeds. In many cases turbulence develops in a succession of instabilities that create flows of increasing temporal and spatial complexity (Lord Rayleigh, Sommerfeld, Heisenberg, Taylor, Landau etc), For the classroom example of pipe flow and several other flows, the linear stability analysis of the lami...

2015 is the International Year of Light, and of its purposes is “to raise awareness of optical technologies”. One such technology, high-power lasers of the petawatt class and beyond, provides the most intense light sources created by humankind so far. The intensities and field strengths in question are in excess of 1022 W/cm2 and 1014 V/m, respectively magnitudes that correspond to concentrating t...

Highest resolution Event Horizon Telescope (EHT) observations will probably soon tell us more about the supermassive black hole at the Galactic Centre (Sgr A*) and the cores of active galactic nuclei (AGN). It might also help to clarify the long-standing question whether the central massive objects in AGN are instead close pairs of black holes. Mergers of supermassive black hole pairs would provid...

Quantum mechanics is important for determining the geometry of spacetime. We will review the role of quantum fluctuations that determine the large scale structure of the universe. In some model universes we can give an alternative description of the physics in terms of a theory of particles that lives on its boundary. This implies that the geometry is an emergent property. Furthermore, entanglemen...

Do quantum many-body systems necessarily come to thermal equilibrium after a long enough time evolution? The conventional wisdom has long been that they do and that, in the process, any quantum information encoded in the initial state is lost irretrievably. Thus the dynamics of many-interacting particles becomes effectively classical. But these ingrained notions of thermalization and ergodicity ha...

New Physics searches at the LHC are mostly being performed with the aim of detecting new states. A complementary strategy is to look for new interactions, something that typically involves precise measurements. In this talk I argue how many of the current SM (and BSM) measurements in the top sector could be used to efficiently and consistently determine of the couplings of an effective field theor...

Sommerfeld Theory Colloquium

Condensed matter provides us deep insights into quantum physics. Giving just two examples, wave-corpuscle duality manifests itself in spectroscopy of strongly correlated systems as coexistence of itinerant and atomic-like features, and graphene and other Dirac materials provide a natural playground to study vacuum reconstruction, Klein tunneling and other fundamental quantum relativistic phenomena...

Protoplanetary discs are natural consequence of star formation. These discs hold the left-over material from star formation, which constitutes the reservoir from which new planetary systems may form. The fate of a new planetary is then intimately linked to the evolution and final dispersal of the disk from which is born, which determines also the striking diversity observed in extra-solar planetary...

Metals are found frequently in nature and their properties are usually very well described within Landaus Fermi liquid theory. Various strongly correlated materials exhibit strange metallic phases which do not fit into the Fermi-liquid framework, however. The theoretical description of such non-Fermi liquids remains one of the main unsolved problems in condensed matter physics. In this talk I will...

Low-mass boson dark matter particles produced after the Big Bang form a classical field and/or topological defects. Effects produced by the interaction of ordinary matter with dark matter may be first power in the underlying interaction strength rather than the second power. This may give a big advantage, since the dark matter interaction constant is extremely small. Limits on certain types of dar...

In this talk I will discuss connections between the physics of complex systems such as spin glasses and attempts to solve optimization problems by ”Adiabatic Quantum Computing” (AQC), a version of ”Quantum Annealing” (QA). An optimization problem is one in which one has to minimize (or maximize) an energy function in which there is competition between different terms so no single configuration of...

I describe the physics of black holes and show how the traditional approach leads to the information paradox. I will then discuss some of the proposed resolutions and the difficulties they need to overcome. I then discuss soft black hole hair and describe how it may help to resolve the information paradox. Finally, I will review the problems that still need to be overcome.

I will review for a general audience some recent developments in our understanding of the mathematical structure of scattering amplitudes in quantum field theory. Many of these developments involve properties that have been discovered ”experimentally”: not in actual experiments, but by carrying out a tedious calculation and then observing that the result has some remarkable hidden simplicity. I wi...

Over the past ten years, there has been a growing interest among physicists for ‘active matter’, a codename that encompasses systems in which energy is taken from the environment to generate self-propulsion at the single particle level. Active particles, such as run-and-tumble bacteria, self-diffusiophoretic colloids or actin filaments in motility assays, are strongly out-of-equilibrium and exhibi...

The upshot of extensive studies of �uctuations in condensed matter systems is that their qualitative importance is typically con#ned to isolated critical points of continuous transitions between phases of matter. This conventional wisdom also predicts the number of low energy Goldstone modes based on the so-called “G/H” pattern of symmetry breaking. I will discuss a class of systems, some quite we...

In February 2016 the LIGO team announced the detection of gravitational waves (GW) created by the merger of two black holes. In addition to confirming a major prediction of general relativity, successful GW detection would provide a powerful new tool for astrophysics. Given their evident importance, the LIGO results and the methods which led to them deserve independent critical analysis. This talk...

The observed deviations from the laws of gravity of Newton and Einstein in galaxies and clusters can logically speaking be either due to the presence of unseen dark matter particles or due to a change in the way gravity works in these situations. Until recently there was little reason to doubt that general relativity correctly describes gravity in all circumstances. In the past few year insights f...