Department of Theoretical Physics

Herbi Dreiner: Testing Locality via Bell's Inequality at Colliders?
2024-09-24 11:00 - 12:00 (Europe/Ljubljana) | C/2-X – F1 čajnica (Jamova)
https://indico.ijs.si/event/2274/

Domen Vaupotič, "Programmable RNA Condensates"
2024-10-10 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
https://indico.ijs.si/event/2280/

Joshua Lockyer: Exploring near-conformal dark sector theories
2024-10-10 15:30 - 16:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (A/1-106 – Seminarska soba fizike (F5))
Dark-showers offer a compelling collider signature for Hidden Valley models featuring a confining dark sector. Our work extends the investigation of these models to near-conformal theories where the running coupling, controlled by renormalization group equations (RGE), flows near to an infra-red fixed point. We establish a framework of two classes of RGE solutions which cover much of the parameter space of confining theories, allowing us to present the first phenomenological results of such near-conformal dark sector theories.
https://indico.ijs.si/event/2271/

Benjamin Fuks: Signatures of toponium formation in LHC run 2 data
2024-10-16 11:00 - 12:00 | https://zoom.us/j/3601731049?pwd=[REDACTED] (Jamova)
We study reported deviations between observations and theoretical predictions associated with the production of a pair of di-leptonically decaying top quarks at the LHC, and we examine the possibility that they reflect a signal of toponium formation. We investigate the production by gluon fusion of a colour-singlet spin-0 toponium bound state of a top and anti-top quark, that then decays di-leptonically. We find strong correlations favouring the production of di-lepton systems featuring a small angular separation in azimuth and a small invariant mass. Although toponium production only contributes to 0.8% of the total top-quark pair-production cross section at the 13 TeV LHC, there is a possibility that it can account for observed excesses in the narrow edges of phase space. We propose a method to discover toponium formation by `reconstructing’ both its top and anti-top quark constituents in the di-lepton channel.
https://indico.ijs.si/event/2276/

Zala Korenjak, "Smectic and soap bubble optofluidic lasers"
2024-10-17 14:15 - 15:15 | Seminar room of physics (106) (IJS)
We have demonstrated for the first time that soap bubbles can be used as lasers. Soap bubbles are simple, yet very unique and marvelous objects. They are very interesting to the wide audience, from children of all ages, to researchers of a number of disciplines including mathematics, physics, chemistry and biology. To realize the soap bubble lasers, we doped the bubbles with a fluorescent dye and pumped them with an external laser. The generated light circulated in the wall of the bubble, which consequently worked as a laser cavity. Instead of soap, we also made bubbles from surfactant-like molecules without any water present. Specifically, smectic liquid crystals, which molecules form well defined molecular layers, were used for this purpose. Such bubbles had a completely uniform thickness with an integer number of molecular layers and most importantly they were extremely stable. The bubbles were attached to a tube or free floating in a container filled with carbon dioxide. The resulting whispering gallery mode lasing was observed in the spectrum of the emitted light as hundreds of regularly spaced sharp peaks. Shifts in the lasing wavelengths enabled the measurement of subtle size changes as small as 10 nm in a millimeter-sized bubble. This incredible precision allowed the bubbles to be used as one of the best pressure and electric field sensors developed till now. This unique physical system may in future allow the study of novel optical and mechanical phenomena in thin films.Video: https://youtu.be/oMXFM70Bmh4
https://indico.ijs.si/event/2342/

Maxim Mai: Lattice studies of resonances that decay to three-hadrons
2024-10-17 15:30 - 16:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (A/1-106 – Seminarska soba fizike (F5))
I will present the lattice results and underlying formalism on resonances omega and a1 that both strongly decay to three-hadron state pi-pi-pi. These are the first and only two resonances extracted from a three-hadron decay on lattice so far.
https://indico.ijs.si/event/2246/

Katarina Kokalj, "Structural analysis of partially fluorinated liquid ethanol"
2024-10-24 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic fluorinated organic compounds that are indispensable in various applications, from consumer products to scientific research, due to their unique chemical and physical properties. Recently, these compounds have been found to be hazardous to both the environment and human health, and their remediation poses numerous challenges due to their stability and chemical inertness. Therefore, structural analysis of PFAS compounds is crucial to address this issue. Molecular dynamics (MD) simulations are an important tool in this regard as they allow the study of atomic behavior over time. In this work, we have focused on fluorinated alcohols. MD simulations were performed with the liquid 2,2,2-trifluoroethanol system (TFE) to determine how different force fields behave in describing the properties of fluorinated compounds. We have investigated six different force fields: TRAPPE, GROMOS-UA, GROMOS-AA, CHARMM, AMBER and OPLS. The suitability of these force fields for the prediction of structural and dynamic properties was evaluated by comparing the calculated results of simulation model systems with experimental X-ray scattering data, conformational analyses from the literature and certain thermodynamic quantities such as density and molecular diffusion coefficient. It was found that the TRAPPE, GROMOS-UA and GROMOS-AA force fields better describe the intermolecular correlations, while CHARMM, AMBER and OPLS are better suited to describe the intramolecular characteristics of TFE. The latter more accurately predicted the conformational forms of the molecules (gauche vs. trans), which we observed from the intramolecular spatial distribution functions and the average molecular end-to-end distances. On the other hand, the position of the maximum of the theoretical scattering curves was in better agreement with the experimental peak with the TRAPPE, GROMOS-UA and GROMOS-AA force fields.
https://indico.ijs.si/event/2338/

Emanuela Bianchi, "Modeling and simulating heterogeneously charged particles: from materials design to biological phenomena"
2024-11-05 10:00 - 11:00 | Seminar room of physics (106) (IJS)
Globular proteins and recently synthesized colloids engineered with differently charged surface regions share a direction-dependent interaction characterized by a reduced bonding valence and a competition between like-charge attraction and opposite-charge repulsion. Understanding the large-scale behavior of heterogeneously charged particles is thus critical for exploring both biological processes, such as the liquid-liquid phase separation of globular proteins, and the assembly of target structures with specific properties at the nano- and micro-scale. Recently, we developed a simple coarse-grained model that, within well-defined limits, accurately reproduces the reference electrostatic potential derived from the linearized Poisson-Boltzmann framework . This model is straightforward to implement in Monte Carlo and Molecular Dynamics (MD) simulations, enabling the exploration of how varying parameters — such as net particle charge and surface charge pattern — affect the self-assembly of these particles.As illustrative examples, I will present our findings on how non-uniform electrostatics at the particle surface can influence the self-assembly of ordered phases as well as the liquid-liquid phase separation . Soft Matter, 7, 8313 (2011), J.Chem. Phys., 142, 114905 (2015) Nanoscale, 9, 1956 (2017), Current Opinion in Colloid & Interface Science, 30, 18 (2017) arXiv:2401.10655, Soft Matter, 20, 7601(2024)
https://indico.ijs.si/event/2461/

Yannick Dengler: Scattering of dark pions
2024-11-07 15:00 - 16:00 | https://zoom.us/j/3601731049?pwd=[REDACTED] (F1 tea room)
https://indico.ijs.si/event/2168/

Fabio Staniscia, "Nanoconfined fluids"
2024-11-14 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
https://indico.ijs.si/event/2337/

Yannick Dengler: Scattering of dark pions
2024-11-14 15:30 - 16:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (A/1-106 – Seminarska soba fizike (F5))
https://indico.ijs.si/event/2267/

Miha Modic (TBA)
2024-11-20 11:00 - 12:00 | Seminar room of physics (106) (IJS)
https://indico.ijs.si/event/2462/

Abhishek Mohapatra: One Born Oppenheimer Effective Theory to rule all Exotics
2024-11-21 15:30 - 16:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (A/1-106 – Seminarska soba fizike (F5))
The XYZ exotic states discovered in the hadronic sector with two heavy quarks constitute one of the most important open problems in particle theory. In this talk, I show that an effective field theory derived from QCD, the Born Oppenheimer effective field theory (BOEFT), can describe exotics of any composition. I show the results of general Schr”odinger coupled equations for arbitrary angular momentum of the light degrees of freedom. The coupled equations describe hybrids, tetraquarks, pentaquarks, doubly heavy baryons, and quarkonia in leading order, including nonadiabatic terms. Additionally, I also present the results of the predicted multiplets, corresponding selection rules, and expressions of the nonperturbative gauge invariant correlators, which are the input of the BOEFT: static energies, generalized Wilson loops, gluelumps, and adjoint mesons that should be calculated on the lattice. Moreover, I show for the first time new results on the behavior of static energies at short distances and mixing with the threshold at long distances based on BOEFT. As an application of this BOEFT, I show results for the hybrid spectrum, hybrid decays to quarkonium and some preliminary results for X(3872) and T_cc (3875).
https://indico.ijs.si/event/2268/

Darius A. Faroughy: Generative modelling for Particle-Clouds with Quantum Numbers
2024-11-27 13:30 - 14:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (C/2-X – F1 čajnica)
https://indico.ijs.si/event/2561/

Ilja Doršner: Is Doublet-Triplet Splitting Necessary?
2024-11-28 14:00 - 15:00 | C/2-X – F1 čajnica (Jamova)
I will demonstrate that it is not necessary to substantially break the mass degeneracy between the Standard Model Higgs boson doublet and the accompanying scalar leptoquark. More precisely, I will show that the experimental proton decay lifetime data cannot place any meaningful bound on the mass of the scalar leptoquark, a.k.a. the color triplet, if one includes effects of higher-dimensional operators. I use particle content of the Georgi-Glashow model for this demonstration but the proposed mechanism can also work in other popular unification frameworks. Interestingly enough, the complete suppression of proton decay via the scalar leptoquark mediation is not in any conflict with the partial suppression of the gauge mediated two-body proton decay signatures. Finally, I will introduce a method that yields a proper upper limit on the cutoff scale of the aforementioned higher-dimensional operators.
https://indico.ijs.si/event/2272/

Tanmoy Sarkar, "Active Junctional Fluctuation-Driven Ordering in 3D Cellular Aggregates"
2024-11-28 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
https://indico.ijs.si/event/2467/

Primož Ziherl, "Intrinsic curvature of lipids"
2024-12-05 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
https://indico.ijs.si/event/2476/

XBW rehearsal
2024-12-12 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
Speakers:Fran Ivan VrbanVeronika BukinaMarin Šako
https://indico.ijs.si/event/2562/

Matej Kanduč, "On foam stability"
2025-01-16 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
Soft, light, and visually captivating, liquid foams are enigmatic – complex systems with intricate multiscale structures. Beneficial in some cases and undesired in others, their inherent instability raises a critical question: how can we stabilize foams? In this seminar, I will discuss our current understanding of foam decay and strategies to enhance foam stability.
https://indico.ijs.si/event/2638/

Primož Ziherl, "Soft cells and the geometry of sea shells"
2025-01-30 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
https://indico.ijs.si/event/2689/

Alessandro Dondarini: Constraining the Minimal Dark Matter 5-plet with Indirect Detection
2025-02-13 15:30 - 16:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (A/1-106 – Seminarska soba fizike (F5))
We critically reassess the Minimal Dark Matter model and propose new indirect detection signatures. Specifically, for the originally proposed accidentally stable SU(2) 5-plet, we compute the photon flux arising from Dark Matter Bound State Formation and Sommerfeld Enhancement, highlighting the appearance of several spectral lines. After analyzing the key features of this flux, we explore the constraints on the 5-plet imposed by FERMI-LAT observations of the galactic diffuse emission, as well as the projected sensitivity of the upcoming Cherenkov Telescope Array (CTA) in searches targeting Dwarf Spheroidal Galaxies.
https://indico.ijs.si/event/2639/

Matej Krajnc, "Hybrid mechanical model of epithelia supported by substrate"
2025-02-20 14:15 - 15:15 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
https://indico.ijs.si/event/2778/

Nicklas Ramberg: Unveiling Hidden Sectors with Gravitational Waves ("The Gravitational Wave Stairway")
2025-02-20 15:30 - 16:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (A/1-106 – Seminarska soba fizike (F5))
In this talk we explore the potential of gravitational wave (GW) observations to probe the structure of hidden sectors beyond the Standard Model (BSM). We argue that the sequential decoupling of new degrees of freedom in these sectors can leave a distinctive imprint on the GW spectrum, resembling a “stairway” pattern. We investigate how this signature can distinguish between different hidden sectors, focusing on two benchmark scenarios: a dark QCD-like theory and a model with a Kaluza-Klein (KK) tower of states. We analyze the sensitivity of current and future GW detectors, such as LISA and Einstein Telescope, to these multi-step spectral features, demonstrating the potential to uncover rich information about the particle content and dynamics of hidden sectors.
https://indico.ijs.si/event/2500/

Michael Zantedeschi: On the fate of evaporating black holes: how the burden of their memory stabilizes them
2025-02-27 15:30 - 16:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (A/1-106 – Seminarska soba fizike (F5))
The “memory burden” effect describes how an object’s stored information resists its own decay. This effect is especially pronounced in “saturons”—systems with maximal entropy consistent with unitarity—of which black holes are prime examples. I will show how this memory burden can halt Hawking evaporation, stabilizing black holes against complete decay. Importantly, this mechanism is not limited to gravitational systems: it also appears in renormalizable field theories. To illustrate its broader relevance, I will present a soliton model that shares key features with black holes and is similarly stabilized by its memory content. Finally, I will discuss unique phenomenological implications and potential observational signatures, particularly for dark matter scenarios.
https://indico.ijs.si/event/2637/

Jonathan Ron, "Deterministic cell motility patterns across scales and sizes"
2025-03-06 14:15 - 15:15 | Seminar room of physics (106) (IJS)
Cell motility plays a crucial role in various biological processes, such as embryogenesis, wound healing, and immune response. Although the complex molecular machinery driving cell motility is relatively well understood, it remains unclear how cells exhibit such diverse migration patterns, both individually and collectively. This seminar will focus on a recently developed theoretical framework for cellular migration, which couples migration features such as polarization, speed, and size to traction forces and adhesion dynamics. The discussion will begin with the model’s predictions for one-dimensional migration of single cells, emphasizing how symmetry is broken during directional decision-making. The model will then be extended to describe cell-cell interactions and the collective behavior of one-dimensional multicellular trains. A two-dimensional stochastic version of the model will also be introduced, explaining the run-and-tumble behavior commonly exhibited by cells. Finally, a new theory will be introduced, linking cell migration to volume regulation via active ion transport. The results presented in the seminar will be supported by extensive experimental validation conducted on various cell types.
Ron, J.E., Monzo, P., Gauthier, N.C., Voituriez, R. and Gov, N.S., 2020. One-dimensional cell motility patterns. Physical review research, 2(3), p.033237.
Mukherjee, A., Ron, J.E., Hu, H.T., Nishimura, T., Hanawa‐Suetsugu, K., Behkam, B., Mimori‐Kiyosue, Y., Gov, N.S., Suetsugu, S. and Nain, A.S., 2023. Actin Filaments Couple the Protrusive Tips to the Nucleus through the I‐BAR Domain Protein IRSp53 during the Migration of Cells on 1D Fibers. Advanced science, 10(7), p.2207368.
Ron, J. E., d’Alessandro, J., Cellerin, V., Voituriez, R., Ladoux, B., & Gov, N. S. (2023). Polarization and motility of one-dimensional multi-cellular trains. Biophysical Journal, 122(23), 4598-4613.
Ron, J. E., Crestani, M., Kux, J. M., Liu, J., Al-Dam, N., Monzo, P., … & Gov, N. S. (2024). Emergent seesaw oscillations during cellular directional decision-making. Nature Physics, 20(3), 501-511.
https://indico.ijs.si/event/2691/

Enrico Morgante: Gravitational waves from confinement in improved holographic QCD
2025-03-06 15:30 - 16:30 | https://zoom.us/j/3601731049?pwd=[REDACTED] (A/1-106 – Seminarska soba fizike (F5))
I will discuss gravitational waves produced during the confinement phase transition in SU(N) Yang-Mills, using a holographic description. The key ingredient will be the construction of the effective action, with the kinetic term playing an important role.
https://indico.ijs.si/event/2680/

V. S. Rao Jampani, "Self-shaping liquids"
2025-03-13 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
https://indico.ijs.si/event/2745/

Petr Šulc, "DNA and RNA nanotechnology: molecular computing, therapeutics, and the quest for the holy grail of self-assembly"
2025-03-20 14:15 - 15:30 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
The control over the self-assembly of complex structures is a long-standing challenge of biomimetic nanotechnology, as the desired assembly pathway is often kinetically derailed by the formation of competing alternative structures or amorphous aggregates. The goal of inverse design problem is hence to find a set of blocks that reliably assemble in high yield into a target structure while avoiding kinetic traps and alternative competing states. We present here a framework called SAT-assembly, which solves this problem by combination of multiscale molecular simulation, graph theory, and constrained optimization methods. While the general approach is abstract, the proposed designs can be realized experimentally e.g. with building blocks made out of DNA or RNA strands. We then show how our models are used to guide experimental realization of highly coveted nanostructure shapes with applications ranging from therapeutic delivery to nanoscale templating, including designs such as capsids, diamond lattices, 3D polycube assemblies, and dynamic reconfigurable multifarious structures, which can switch between multiple possible stable folds.
https://indico.ijs.si/event/2744/

Marko Popovic, "Biological tissues as active amorphous solids"
2025-03-25 14:00 - 15:00 | C/2-X – F1 čajnica (Jamova)
https://indico.ijs.si/event/2784/

Sifan Yin, "Developmental mechanics of divergent buckling patterns in chick gut"
2025-03-27 14:00 - 15:00 | A/1-106 – Seminarska soba fizike (F5) (Jamova)
https://indico.ijs.si/event/2785/
