Lorentz Institute

July 5, 2023, 7:30 p.m.
Sitterzaal

Quantum statistical mechanics of charged black holes and strange metals

Subir Sachdev

Complex many-particle quantum entanglement is a central theme in two distinct major topics in physics: the strange metal state found in numerous correlated electron compounds, and the quantum theory of black holes in Einstein gravity. I will describe recent progress on both topics. Hawking’s result on black hole entropy has now been improved to a universal, low energy density of quantum states of non-supersymmetric charged black holes in 3+1 dimensional asymptotically Minkowski space. A model of a metal with fermionic excitations on a Fermi surface with a spatially random Yukawa coupling to a critical boson provides a universal theory of strange metals which matches numerous observations. This progress has relied upon insights gained from the Sachdev-Ye-Kitaev model of many-particle quantum states without quasiparticle excitations.

Sept. 6, 2023, 7:30 p.m.
Sitterzaal

Towards interpretable AI and artificial agency in quantum science

Hans Jurgen Briegel

The use of machine learning and artificial intelligence (AI) in basic research is changing scientific practices. For basic science it seems desirable, if not mandatory, that its methods remain transparent and that new findings can be explained. We think that the physical sciences, including quantum physics, can play a special role for the development of explainable AI. In this talk, we will review some of our recent work on the development of AI for quantum physics, and on the interplay of machine learning with quantum information, more generally. We will focus on the model of projective simulation (PS), which is an interpretable model for learning and decision-making that has found applications, e.g., in quantum error correction and the design of quantum information experiments, but also in robotics and the modelling of biological behavior. We will first discuss some of these applications and then discuss more foundational issues of modelling artificial agency in the context of quantum physics.

Oct. 18, 2023, 7:30 p.m.
Sitterzaal

Friction, Earthquakes and Everything in Between

Jay Fineberg

Friction is generally described by a single degree of freedom, a ‘friction coefficient’. We experimentally study the space-time dynamics of the onset of frictional motion when two contacting bodies start to slide. We first show that the transition from static to dynamic sliding is governed by rupture fronts (essentially earthquakes) that break the contacts along the interface separating the two bodies. Moreover, the structure of these ‘laboratory earthquakes’ is quantitatively described by singular solutions originally derived to describe the motion of rapid cracks under applied shear. We demonstrate that this framework essentially replaces the idea of a ‘friction coefficient’ as a description for the onset of frictional motion. Moreover, this framework quantitatively describes both ‘laboratory earthquake’ motion and arrest. The results establish a new (and fruitful) paradigm for describing friction and provide a fundamental understanding of how earthquakes develop, progress and eventually arrest.

Oct. 18, 2023, 7:30 p.m. CE Jay Fineberg (Hebrew University of Jerusalem) Friction, Earthquakes and Everything in Between

Nov. 1, 2023, 7:30 p.m. CE Alessandra Buonanno (Max Planck Institute for Gravitational Physics) TBA

Nov. 29, 2023, 7:30 p.m. CE Annette Zippelius (University of Gottenburg) TBA

LS = Lorentz Seminar, Casimir room (276), Oort building
CE = Colloquium Ehrenfestii, De Sitter lecture room, Oort building
SBM = Soft & Biological Matter Seminar, Casimir room (276), Oort building
CS = Cosmology Seminar, Casimir room (276), Oort building
ST = String Theory Seminar, Casimir room (276), Oort building