News: Institute of Physics

Milgromian dynamics (MOND) is an alternative to non-baryonic cold dark matter, proposed by Moti Milgrom in 1983. In this talk, I will review the successes and challenges that the MOND paradigm faces on the scales of galaxies, galaxy groups, and galaxy clusters. Firstly, I will focus on the dynamical regularities and empirical laws shown by galaxies, which point to the existence of a characteristic acceleration scale. These observational facts that were predicted a-priori by MOND. Next, I will illustrate the problem of galaxy clusters in MOND and discuss possible solutions to this long-standing challenge.

Controlling the chemical structure of matter at the atomic level with light seemed impossible until now. Now, scientists have developed a technique to control photochemical reactions at the level of individual molecules. An international team of researchers, including Tomáš Neuman from the Institute of Physics at CAS, has published a method for controlling molecular dynamics in Nature Nanotechnology. This breakthrough could open a new chapter in photochemistry research.

The radial acceleration relation (RAR) is a strong correlation of late-type galaxy dynamics, seeming to describe a mysterious link between baryonic and total dynamical mass. Its properties are so striking that it has even been argued to manifest a new law of gravity in galaxies, the so-called Modified Newtonian Dynamics (MOND). I will describe four recent works analysing the RAR in novel ways. The first (arXiv:2303.11314) marginalises over the galaxy parameters upon which the RAR variables depend, revealing an extremely small intrinsic scatter of 0.034 dex. The second (arXiv:2301.04368) applies a technique called symbolic regression to generate and score all possible functional forms for the RAR, suggesting the data is insufficient to infer Newtonian and deep-MOND limits with statistical confidence. The third (arXiv:2305.19978) uses machine learning to present evidence that the RAR is fundamental: it has no residual correlations, is the tightest projection of galaxies' dynamical parameter space and is uniquely capable of explaining all other dynamical correlations. The last (arXiv:2401.04796) shows that under a “classic” MOND interpretation, the RAR is inconsistent with planetary ephemerides and the kinematics of local wide binaries. I close with an abortive attempt to tie this all together.

The Excellent Research call in the Johannes Amos Comenius Programme (P JAK) is one of the most important Czech grant calls with a total allocation of CZK 12.2 billion, which aims to enable Czech research to reach European and global excellence. The Institute of Physics of the Czech Academy of Sciences (FZU) has achieved a significant success in this competition and will participate in the investigation of six projects out of the total of 26 projects that received funding in an extremely demanding evaluation process.

For the first time, an international team of scientists has successfully developed a polyradical nanographene by combining two concepts: pi-magnetism formation in nanographene and strong interaction between electrons and topological frustration and they detected the magnetic signal using advanced scanning microscopy and quantum mechanical calculations. Graphene nanoparticles exhibit magnetic properties in certain shapes, making them suitable for information storage and processing in quantum computing.  

The coefficients of the operators of an effective field theory (EFT) are constrained to satisfy certain inequalities, under the (mild) assumption that the UV completion satisfies general requirements of causality and unitarity. I discuss the extension of these ideas to theories where the Lorentz symmetry is spontaneously broken, as it happens in cosmology and condensed matter physics. I explain why the use of the S-Matrix run into immediate problems. Constraints can be derived using dispersive arguments for the 2-point function of conserved currents and applied to models of interest in high-energy and condensed matter.

The program is composed of four sessions. Each session starts with a lecture and continues with practical exercises. For practical exercises, the users will be provided with a cookbook, installation files and necessary data. Preliminary experience with Jana2006/Jana2020 is not required. The workshop is OFF LINE.

"A scientific discovery has no merit unless it can be explained to a barmaid.” This quote by Nobel laureate Ernest Rutherford could be applied to the recent achievements of Libor Šmejkal. He was selected from hundreds of nominated scientists to be awarded the Breakthrough Scientific Discovery of the Year 2023 title in the Falling Walls competition for his theoretical work on altermagnetism and non-dissipative nanoelectronics.

In an article published in Nature an international team of scientists breaks down the traditional idea of dividing magnetism into two branches – the ferromagnetic one, known for several millennia, and the antiferromagnetic, discovered about a century ago. Researchers have now succeeded in directly experimentally demonstrating a third altermagnetic branch theoretically predicted by researchers in Prague and Mainz several years ago.

This year, for the first time, we will participate in the ABC Festival at the National Museum of Agriculture in Prague! This event will take place on the weekend of April 27 and 28, 2024. We are preparing the program for you.

Do you sometimes find an error in the largest internet encyclopedia? Are you missing Wikipedia articles about eminent scientists? We can change that together! In March, we’re going to start with the topic of Women in Science and join this year’s "Měsíc žen na Wikipedii" (Women's month on Wikipedia). Newbies need not worry; experienced editors will be at their disposal to help them with the articles. All you need is to bring your laptop. We will arrange refreshments for you in the beautiful building of the Academy of Sciences. We are looking forward to welcoming you at the edit-a-thon! P.S.: Some of us organizers are newbies too. We are going to learn best practices in editing together!

The Institute of Physics of the Czech Academy of Sciences organizes the Physics Photography 2024 competition, which this year is thematically dedicated to "transformation".  The main goal of the competition is to popularize the beauty of physics and to break the stereotypes of the perception of this field of science. The photography competition ends with the announcement of winners and an exhibition of the awarded and selected photos during the Night of Scientists, which is organized by the institute in the Na Slovance facility on Friday, September 27, 2024.

In this talk I will discuss the potentialities of future ground-based millimeter-wavelength line intensity mapping for constraining the properties of gravity at cosmological scales. I shall first introduce line intensity mapping experiments, focusing on their key properties and differences with respect to galaxy surveys. I will describe the main reasons to consider alternative theories of gravity. I will concentrate on the properties of the theories that have been tested in arXiv:2304.08471. Finally, I will present and discuss the results obtained.

Part1: The Scalar Field Dark Matter (SFDM) model assumes an ultralight scalar particle (m~1e-22 eV) as a candidate to explain the Dark Matter nature. This model obeys the Schrodinger-Poisson (SP) system of equations coupled to gravity in the non-relativistic approximation. While on a large scale, it behaves as a non-relativistic and pressureless fluid, equivalent to CDM, on a galactic scale, it leads to effective "quantum pressure" and the formation of Bose-Einstein condensates (BEC). This implies an interesting phenomenology which is different from CDM. In fact, the SFDM model shows a cut-off on small-scale structures and predicts cored halos. In this presentation, I will show how to construct the initial conditions for the SP system and the evolution for both small-scale and cosmological simulations. Additionally, I will show some examples of mergers of different halos assembly and the final states of such systems. Finally, I will discuss some perspectives that include Zoom-in cosmological simulations for this model. Since these efforts are expected to be compared with observations, we will use the rotation curves derived from the MaNGA galaxy catalogue to constrain the SFDM-free parameters of the model. Part2: Given that the nature of dark matter is currently unknown, exploring alternative theories to the Standard Model and their implications on galactic scales is both feasible and compelling, partly because of the continuous development of computational resources. In this talk, we will review the implementation of numerical methods to study the properties and evolution of some astrophysical systems in dark matter models. First, we will study the impact of the Generalized Dark Matter (GDM) model on the formation and distribution of Hickson Compact Groups (HCGs) using the merger trees method and mock catalogues. Studying these systems is interesting for understanding the effects of dark matter on galactic scales in dynamically active structures. Additionally, we will explore the evolution at small scales of halos within the Cold Dark Matter (CDM) and Scalar Field Dark Matter (SFDM) models, using initial conditions from cosmological N-body simulations to compare the final state of the halos, including the shape of the density profile and the process of virialization. In both cases, the properties of astrophysical systems can be compared to observations of nearby galaxies through their rotational curves, as well as distant galaxies, by studying the hierarchy of each model. This allows us to describe the weaknesses and strengths of the dark matter candidates.

We invite you to a seminar by Professor Kenichi L. Ishikawa of The University of Tokyo at the HiLASE Centre on the topic of Building artificial intelligence and science-and-theory-based simulations toward cyber-physical-system (CPS) laser manufacturing.

Calculation of the mass-transfer rate of a Roche lobe overflowing star is a fundamental task in binary star evolution theory. First, we introduce existing mass-transfer prescriptions that are based on a common set of assumptions that combine optically-thick and optically-thin regimes with different flow geometries. Next, we present our new model of mass transfer based on the assumption that the Roche potential sets up a nozzle converging on the inner Lagrangian point and that the gas flows mostly along the axis connecting both stars. We derive a set of 1D hydrodynamic equations governing the gas flow with the value of the mass-transfer rate being determined as the eigenvalue of the system. The inner boundary condition directly relates our model to the structure of the donor obtained from 1D stellar evolution codes. For the polytropic equation of state we obtain an algebraic solution that gives the mass-transfer rate within a factor of 0.9 to 1.0 of existing optically-thick prescriptions and reduces to the existing optically-thin prescription for isothermal gas. For a realistic EOS, we find that the mass-transfer rate differs by up to a factor of 4 from existing prescriptions. We illustrate the effects of our new model on a realistic binary star system. Finally, we explain how additional physics such as radiation or magnetic fields can be implemented into our new model.

Dear colleagues, we would like to invite you to the seminar of Division of Elementary Particle Physics of Institute of Physics, presented by Dr. Roman Lysák. For more info, please see invitation.