Events
Astrophysics and Cosmology Seminar
Magnetic field dissipation in neutron star cores
Dr. Dmitry Ofengeim Jr.
HUJI
Wed, 29 Mar 2023, 11:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: Neutron stars are one of the most extreme types of objects in the modern Universe. They have masses about 1−2 solar masses and radii about 10−15 km. This makes them very compact stars with extremely strong gravitational fields. Density of their interiors exceeds the density of atomic nuclei by several times. Magnetic fields of neutron stars are in the range 10^8−10^15 G on the surface and possibly larger inside. Evolution of magnetic fields is thought to be a source of various observational phenomena related to these stars. It is well studied in the outer layers of the neutron star (the crust). Study of magnetic field evolution in the inner layers (the core) is a more complicated task due to much more complicated physics of the core matter. It can be superfluid, superconducting, and its transport microphysics is still poorly understood. However, there is significant progress in such studies in recent years, especially in assumption of the minimum beta-equilibrated composition of the core (neutrons, protons and electrons only). In this talk I describe the modern approach to magnetic field evolution in neutron star cores and show my recent results concerning a realistic core composition which includes muons.
Quantum optics seminar
A quantum lens for testing quantum features of gravity
Dr. Matteo Carlesso
Queen’s University Belfast
Wed, 29 Mar 2023, 16:00
ZOOM only
Abstract: Zoom Link: https://us02web.zoom.us/j/86478278003
Abstract:
In this talk, I will introduce the problem of testing possible quantum features of gravity with quantum systems. After an overview of the problem, I will dig into some of the experimental proposals that appeared in the literature. I will discuss the main obstacles in realising such experiments and try to delineate alternative paths to test the quantumness of gravity.
Biological and soft-matter physics
Cytoskeletal gels are intrinsically active elastic materials that design their own shape in response to system geometry
Prof. Anne Bernheim-Groswasser
Department of Chemical Engineering and the Ilse Kats Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev
Thu, 30 Mar 2023, 12:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: Living systems adopt a variety of shapes. These morphologies commonly rely on contractile stresses generated by myosin motors in cytoskeletal networks. How these intrinsically active stresses arise in complex 3D shapes remains poorly understood. Here, initially flat not-prepatterned actomyosin gel discs of varying aspect ratio spontaneously self-organize into a family of 3D shapes through robust dynamical pathways. Shape deformation is encoded in system initial aspect ratio – all shapes collapse onto a universal line indicating shaping scalability. Despite the evolved dynamics and lack of pre-programming, the final configurations show surprisingly simple scaling dependence on system initial thickness and radius. Altogether, actomyosin gels form a class of intrinsically active elastic materials, designing their own shape in response to system geometry, without needing specific pre-programming and/or regulation. Our system paves the way for developing elastic active materials with controllable, molecularly induced, active stresses, to create tunable bio-soft robots with desired target shapes.
Biological and soft-matter physics
Self-organization principles in active matter systems
Prof. Erwin Frey
Ludwig-Maximilians University (LMU) Munich, Germany
Sun, 02 Apr 2023, 11:00
Bldg. 43 (Chemistry), Room 015 -SPECIAL SEMINAR (Joint with the Dept. of Chemistry)
Abstract: Active matter systems have emerged as a key paradigm for studying non-equilibrium
systems, offering unique insights into the rich phenomenology of living matter. In
particular, microtubule-motor mixtures and the actin motility assay exemplify how
relatively simple constituents can self-organize into complex structures with novel
phases of matter, such as polar flocks, active foams, and phases exhibiting topological
defects. In this talk, I will review recent advances in understanding the emergence of
these collective phenomena based on agent-based simulations and active field
theories. Additionally, active systems that self-organize through communication
between agents are an area of active research. I will highlight the latest progress in the
field and discuss the significance of these findings for fundamental science and potential
applications in soft robotics.
Physics Colloquium
Conformal Field Theory of the 3D Ising Model
Prof. Slava Rychkov
Institut des Hautes Etudes Scientifiques (Bures-sur-Yvette)
Tue, 04 Apr 2023, 15:15
Zoom
Abstract: The two-dimensional Ising model was solved exactly as a lattice model at any temperature (Onsager, 1941) or as a conformal field theory at the critical temperature (Belavin, Polyakov, Zamolodchikov, 1984). On the other hand, the three-dimensional Ising model has so far resisted all attempts at the exact solution as a lattice model, although renormalization group methods (Wilson, 1971) have been successful at providing approximate understanding at T=Tc. Recently, conformal field theory methods ("conformal bootstrap") have been shown to provide a very accurate description of the 3D Ising model at the critical temperature. I will review these successes, which offer a tantalizing hope that the 3D Ising model may after all be exactly solvable.
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