Integrated Calendar

Zoom Link: https://weizmann.zoom.us/j/93181739182?pwd=YTd0K1drTmZSdnB0bElFZVI4K0NXdz09

The cosmological constant, also known as dark energy, was believed to be caused by vacuum fluctuations, but naive calculations give results in stark disagreement with fact. In the Casimir effect, vacuum fluctuations cause forces in dielectric media, which is very well described by Lifshitz theory. Recently, using the analogy between geometries and media, a cosmological constant of the correct order of magnitude was calculated with Lifshitz theory [U. Leonhardt, Ann. Phys. (New York)  411, 167973 (2019)]. This lecture discusses the empirical evidence and the ideas behind the Lifshitz theory of the cosmological constant without requiring prior knowledge of cosmology and quantum field theory.

Astrophysical phenomena play a definitive role in our understanding of fundamental particle physics, and vice-verse.
I will present two lines of research, showcasing the interplay between particle physics theory and astrophysics.

In the first half of the talk, I will show how the viable parameter space for dark matter can be established using gravity alone.
At the lowest end of the possible range for the dark matter particle mass, the de Broglie wavelength of ultralight dark matter (ULDM) attains astronomical scales. The ensuing wave mechanics phenomena can be tested observationally in a variety of astrophysical systems. I will describe a search for the imprint of ULDM on the gas kinematics of low-surface-brightness galaxies, leading to an absolute lower bound on the mass of dark matter. A host of other systems, ranging from supermassive black holes to gravitational lensing, offer promising means to advance the search for ULDM by orders of magnitude.

In the second half of the talk, I will show how an analysis of cosmic ray antimatter — long considered a smoking gun for dark matter in the TeV range — has taken a surprising turn, leading us to new theoretical insights on the problem of the origin of loosely-bound nuclei in hadronic collisions (sometimes referred to as ``Snowballs in Hell”). The resulting research programme, now explored at the Large Hadron Collider, offers a bridge between two-particle correlation analyses to the study of nuclear clusters.

The understanding of strongly-correlated quantum matter has challenged physicists for decades.
Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for
simulating quantum materials. In this talk I will present a new platform to investigate strongly correlated physics, namely moiré quantum matter. In particular, I will show that when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a strongly-correlated electronic system. These flat bands systems exhibit a plethora of quantum phases, such as correlated
insulators, superconductivity, magnetism, Chern insulators, and more. Furthermore, it is possible to extend the moiré quantum matter paradigm to systems beyond magic angle graphene, and I will present an outlook of some exciting directions in this emerging field.