Events
Condensed Matter Seminar
Topological superconductivity in phase-controlled Josephson junction arrays
Prof. Yuval Oreg
WIS
Mon, 19 May 2025, 11:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: The search for low-dimensional topological superconductivity is fueled by the promise of new and exotic physics, such as chiral superconductivity and non-Abelian anyons. However, the need to break time-reversal symmetry, usually by applying a relatively large external magnetic field, has hindered the realization of these novel phases of matter due to the deterioration effects of the field on the superconductor. We propose to break the time-reversal symmetry by controlling and tuning the superconductors' phases only to a regime where topological superconductivity emerges without needing an external exchange field. Our platforms rely on commonly available semiconductor-superconductor heterostructures, where spin-orbit coupling plays a central role. The main advantages of our approach over the existing ones are its tunability, suitability to a wide range of materials, and lack of magnetic field-induced impurity states.
Particles and Fields Seminar
Dynamical String Tension Theories with target space scale invariance, new braneworlds, modifying the swampland, explaining 4D and a new model for Dark Matter
Eduardo Guendelman
BGU
Mon, 19 May 2025, 14:00
Sacta-Rashi Building for Physics (54), room 207
Abstract: The string and brane tensions do not have to be put in by hand, they can be dynamically generated, as in the case when we formulate string and brane theories in the modified measure formalism. Then string and brane tensions appears, but as an additional dynamical degree of freedom. It can be seen however that these string or brane tensions are not universal, but rather each string and each brane generates its own tension, which can have a different value for each string or brane. We consider new background fields that can couple to these new types of extended objects, one of them, the “tension scalar” is capable of changing locally along the world sheet the value of the tension of the extended object. When many strings probing the same region of space are considered this tension scalar is constrained by the requirement of quantum conformal invariance. For the case of two strings probing the same region of space with different dynamically generated tensions, there are two different metrics, associated to the different strings, that have to satisfy vacuum Einstein’s equations and the consistency of these two Einstein’s equation determines the tension scalar. We discuss one of the examples where this solutions where the strings are confined by surfaces where the string tensions grow very big. The dynamical string tensions imply dynamical Planck scale and this can modify the swampland constraints. The demand that the effective low energy theory still respects the target space scale invariance, where gravity appears by integrating out the closed strings and open strings model matter leads to 4D. A new model of Dark Matter (DM), where DM appears as strings with tensions different to ours .
Physics Colloquium
Fast Radio Bursts - Far Reaching Beacons
Paz Beniamini
Open University
Tue, 20 May 2025, 12:00
Ilse Katz Institute for Nanoscale Science & Technology (51), room 015
Abstract: Fast Radio Bursts (FRBs) are bright, intense and rapid flashes of radio waves that can reach us from across the cosmos. First discovered less than two decades ago, FRBs have rapidly become one of the most exciting mysteries in astrophysics. Recent discoveries — including a burst from a magnetar (a highly magnetized neutron star) in our own galaxy, and the precise localization of over a hundred FRBs to distant galaxies — have reshaped our understanding of these enigmatic signals. Yet fundamental questions remain: Are all FRBs produced by magnetars? Do all sources repeat? What is the mechanism that powers the bursts themselves? In this talk, I will introduce the key observational features of FRBs and the leading ideas about their origins. I will also highlight how, even without a full understanding of their sources, FRBs offer remarkable opportunities for cosmology — from mapping "missing" baryonic matter in the Universe to probing the epoch of cosmic reionization. These radio flashes are not just puzzles to solve, but also powerful tools to explore the structure and history of the Universe.
*** Refreshments at 12:00, talk at 12:15.
Biological and soft-matter physics
Membrane remodelling in life processes: Unravelling membrane interactions, one vesicle at a time
Dr. Raya Sorkin
School of Chemistry, Tel Aviv University
Thu, 22 May 2025, 12:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: Fundamental understanding of physiological processes that occur at biological membranes, such as membrane fusion, necessitates addressing not only the biochemical aspects, but also biophysical aspects such as membrane mechanical properties and membrane curvature. In this talk, I will show how we combine membrane model systems, micropipette aspiration, optical tweezers and confocal fluorescence microscopy to study membrane shaping and membrane fusion processes. I will describe a new tool we developed, where we form membrane bilayers supported on polystyrene microspheres which can be trapped and manipulated using optical tweezers. Using this approach, we demonstrate successful measurements of the interaction forces between the Spike protein of SARS CoV-2 and its human receptor, ACE2. We further use bead-supported membranes interacted with aspirated vesicles to reveal the inhibitory effect of membrane tension on hemifusion. I will also describe a particular case of membrane shaping during the formation of the newly discovered organelle termed migrasome. We show that tetraspanin proteins involved in migrasome formation strongly partition into curved membrane tethers, and we reveal a novel, two-step process of migrasome biogenesis.
Physics Colloquium
TBA
Ido Regev
BGU
Tue, 27 May 2025, 12:00
Ilse Katz Institute for Nanoscale Science & Technology (51), room 015
Abstract:
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