У оквиру семинара Института за физику у Београду, у уторак, 28. маја 2024. године у 13 часова у сали Звонко Марић Института за физику у Београду, др Дејан Стојковић (Универзитет у Бафалу, Државни универзитет Њујорка), одржаће предавање:

Limits of physics and how to cross them

САЖЕТАК:

Theoretical high-energy physics faces fundamental problems which will most likely not be resolved using the standard framework of quantum field theory plus general relativity. In this talk, we will first try to identify what physics (and science in general) can and cannot do. Among other things, it is not possible to acquire any objective knowledge about the system even in principle, which implies that we have to address the role of an observer in science. This question literally crosses the boundary between physics and metaphysics; however, it cannot be ignored for much longer. A closer look at it implies that for any substantial further progress we would have to understand infinities much better and learn how to deal with them.

У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, у четвртак, 23. маја 2024. године у 14 часова путем Zoom платформе, проф. Дорон Коен (Департман за физику, Бен Гурион Универзитет, Израел) одржаће предавање:

Quantum irreversibility

САЖЕТАК:

Quantum mechanically, a driving process is expected to be reversible in the quasistatic limit, also known as the adiabatic theorem. This statement stands in opposition to classical mechanics, where a mix of regular and chaotic dynamics implies irreversibility. A paradigm for demonstrating the signatures of chaos in quantum irreversibility is a sweep process whose objective is to transfer condensed bosons from a source orbital. In this talk we will show that such a protocol is dominated by an interplay of adiabatic-shuttling and chaos-assisted depletion processes [1]. The latter is implied by interaction terms that spoil the Bogoliubov integrability of the Hamiltonian. As the sweep rate is lowered, a crossover to a regime that is dominated by quantum fluctuations is encountered, featuring a breakdown of quantum-to-classical correspondence. The major aspects of this picture are not captured by the common two-orbital approximation, which implies failure of the familiar many-body Landau-Zener paradigm.

[1] Y. Winsten and D. Cohen, Phys. Rev. A 107 (2023) 052202.

У оквиру семинара Групе за гравитацију, честице и поља Института за физику у Београду, у петак, 17. маја 2023. године у 11 часова у сали 360, Павле Стипсић (Институт за физику у Београду) одржаће предавање:

Symmetry breaking mechanisms of the 3BF action for the Standard Model coupled to gravity

САЖЕТАК:

We study the details of the explicit and spontaneous symmetry breaking of the constrained 3BF action representing the Standard Model coupled to Einstein-Cartan gravity. First, we discuss how each particular constraint breaks the original symmetry of the topological 3BF action. Then we investigate the spontaneous symmetry breaking and the Higgs mechanism for the electroweak theory in the constrained 3BF form, in order to demonstrate that they can indeed be performed in the framework of higher gauge theory. A formulation of the Proca action as a constrained 3BF theory is also studied in detail.

У оквиру традиционалног колоквијума Института за физику у Београду, у четвртак, 16. маја 2024. године, у 12 часова у сали „Звонко Марић“ предавање под насловом:

Elasticity and graph architecture of animal tissues

одржаће др Матеј Крајнц (Јожеф Стефан институт, Љубљана, Словенија)

САЖЕТАК:

It has been known since the work by Sir d’Arcy Thompson in the early 1900s that animal cells in many respects mechanistically behave similarly to soap bubbles or liquid droplets. Much like collections of soap bubbles, animal cells also form aggregates in which they interact and rearrange, and, due to their living nature, they also grow, divide, and migrate. We study these complex dynamics both theoretically and computationally using various approaches including variants of the finite-elements method and basic principles of elasticity theory and theory of dynamical systems. In the first part of the talk, we will derive the elasticity theory of epithelial monolayers, starting from a single-cell mechanical description in which cells are phenomenologically described as liquid droplets. Using this theory, we will show that unlike non-living thin elastic plates, which wrinkle only when they are supported by thick elastic substrates, epithelia may undergo wrinkling instability even in the absence of the substrate [1]. The second part of the talk will focus on three-dimensional cell aggregates as models of tumors and tumor spheroids. We will introduce Graph vertex model, a new computational approach to studying complex dynamics of space filling cell aggregates in which the topology of the network of cell-cell interfaces is encoded in a graph format and stored in a graph database [2]. Topological transformations associated with cell rearrangements and divisions are in this model performed by elementary graph transformations that are quite straight-forward to implement computationally.

[1] U. Andrensek, P. Ziherl, and M. Krajnc, Phys. Rev. Lett. 130, 198401 (2023).
[2] T. Sarkar and M. Krajnc, arXiv: 2309.04818, to appear in PLOS Comput. Biol.