Sommerfeld Lecture Series (ASC)

The Arnold Sommerfeld Center for Theoretical Physics (ASC)
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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.

  1. JUL 11 · VIDEO

    Comments on the phase of the Euclidean gravity partition function on spheres

    Euclidean gravity on a sphere (euclidean de-Sitter) gives rise to some phase factors. We discuss how these phase factors change when we include an observer. We also discuss situations involving products of spheres.

    1h 13m

  2. JUL 11 · VIDEO

    The meaning of spacetime: Black holes, wormholes and quantum entanglement

    We start by describing the geometrical notions central to Einstein's theory of gravity. We then discuss current ideas for how spacetime geometry could emerge in a quantum theory of gravity. We will see that quantum entanglement plays a crucial role.

    46 min

  3. JUL 4 · VIDEO

    Public Lecture: From Atoms to Novel Materials: A Quantum Engineer's Dream

    Which 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 we master quantum mechanics well enough today to explain how materials behave from the only knowledge of the atoms which build them? Have we reached the stage where the principles of quantum mechanics allow for the design of a novel material with specific functionalities?

    1h 20m

  4. JUL 4 · VIDEO

    Sommerfeld Theory Colloquium: Quantum Matter with Strong Correlations

    From 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 paradigm of solid-state physics, in which electrons form a gas of wave-like quasiparticles, must be seriously revised for strongly correlated materials. Instead, a description accounting for both atomic-like excitations in real-space and quasiparticle excitations in momentum space is requested. I will review how Dynamical Mean-Field Theory -an approach that has led to significant advances in our understanding of strongly correlated materials- fulfills this goal. New frontiers are also opening up, which bring together condensed-matter physics and quantum optics. `Artificial materials' made of ultra-cold atoms trapped by laser beams can be engineered with a remarkable level of controllability, and allow for the study of strong- correlation physics in previously unexplored regimes.

    1h 19m

  5. JUL 4 · VIDEO

    Solid State Theory Seminar: Death of a Quasiparticle: Strong Correlations from Hund's Coupling

    According 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-insulator transition, for example as a result of the Hund's rule coupling. I will provide evidence that this is relevant for many materials, especially oxides of the 4d transition metals. In other materials, such as cuprates, quasiparticles are destroyed selectively in specific regions of momentum-space. The understanding of charge and thermal transport in such ``bad metals'' is a key issue, with both fundamental and practical implications.

    1h 23m

  6. JUL 4 · VIDEO

    Public Lecture: Many Worlds in One

    Recent 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.

    1h 8m

  7. JUL 4 · VIDEO

    Sommerfeld Theory Colloquium: Looking for Cosmic Strings

    Cosmic 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.

    1h 8m

  8. JUL 4 · VIDEO

    Public Lecture: The quantum phases of matter

    In 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.

    1h 4m
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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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