We present an investigation into the statistical properties of light traveling through a turbulent medium. Specifically, we analyze the probability density function (PDF) of the light intensity I on a detector for different values of I and the beam path length. The PDF, P(I), exhibits two tails with stretched exponents smaller than one. This indicates a significantly higher probability of rare events with light intensities much greater than the average than would be predicted by a naive Gaussian estimate. We find that these rare events are caused by a randomly located lens in the light path, which allows us to predict the shape of bright spots on the detector.

Biography
Prof. V.V. Lebedev obtained a B.S. in Physics (1974) and an M.S. in Theoretical Physics (1976), both from the Moscow Institute of Physics and Technology. Later, he received his PhD in Theoretical Physics (1979) from the Landau Institute for Theoretical Physics. He has been a Corresponding Member of the Russian Academy of Sciences since 2003, a Chair Professor at the Moscow Institute of Physics and Technology since 2008, and a Principal Researcher at the Landau Institute for Theoretical Physics since 2019. He served as Director of the Landau Institute for Theoretical Physics (2003-2018). He has over 150 scientific publications, with research focusing on the theory of soft condensed matter, the theory of nonequilibrium dynamical phenomena (including turbulence), statistical theory, and theoretical biophysics.

This talk elucidates the vortex-dominated flows and unsteady lift underpinning the high-performance flight of bats—the only mammals capable of active flapping flight. A key kinematic feature examined is the dynamic wingspan variation observed during flapping flight. Based on numerical simulations of flows over a slow-flying bat, it is found that the dynamically changing wingspan can significantly enhance the lift. Analysis of the resultant vortex structures and a decomposition of aerodynamic forces show that the enhancement is primarily attributable to an intensified leading-edge vortex system, whose strength is promoted by the dynamic wing morphing. A quantitative lift formulation developed for unsteady aerodynamic analysis under these conditions will also be presented.

Biography
Prof. Shi-Zhao Wang received his doctoral degree in fluid dynamics from University of Chinese Academy of Sciences in 2011. He is currently a professor at Institute of Mechanics, Chinese Academy of Sciences. His research focuses on unsteady aerodynamics, aeroacoustics, and biolocomotion. He has authored more than 90 peer reviewed papers in leading journals in fluid mechanics, including Annual Review of Fluid Mechanics, Journal of Fluid Mechanics, and Physical Review Fluids.

I will make a few comments on heavy tetraquarks using the gauge/string duality. In particular, I describe the structure of the two low-lying Born-Oppenheimer potentials.

This talk presents results of a comprehensive study of the classical and quantum dynamics of spin 1/2 Dirac fermion particles with dipole moments under the action of arbitrary external fields (including gravitational, inertial, electromagnetic, axion ones). The gauge-theoretic framework of the general-relativistically covariant Dirac theory is used to describe in a consistent way the minimal and nonminimal couplings of fermions to external fields of different physical nature. The quantum and quasiclassical equations of motion are derived and a complete consistency of the quantum and classical spin dynamics is demonstrated. Applications range from astrophysics, to precision experiments with polarized particles in accelerators and storage rings, to the heavy-ion collisions.

Synchronization between the internal dynamics of the superconducting phase in a Josephson junction (JJ) and an external ac signal is a fundamental physical phenomenon, manifesting as constant-voltage Shapiro steps in the current-voltage characteristic. Mathematically, this phase-locking effect is captured by the Resistively Shunted Junction (RSJ) model, an important example of a nonlinear dynamical system. The standard RSJ model considers an overdamped JJ with a sinusoidal (single-harmonic) current-phase relation (CPR) in the current-driven regime with a monochromatic ac component. While this model predicts only integer Shapiro steps, the inclusion of higher Josephson harmonics is known to generate fractional Shapiro steps. In this paper, we show that only two Josephson harmonics in the CPR are sufficient to produce all possible fractional Shapiro steps within the RSJ framework. Using perturbative methods, we analyze amplitudes of these fractional steps. Furthermore, by introducing a phase shift between the two Josephson harmonics, we reveal an asymmetry between positive and negative fractional steps — a signature of the Josephson diode effect.

The unitarity of the 4D lattice theory of gravity in the case of the Minkowski signature is proved. The proof is valid only for lattices that conserve the number of degrees of freedom during time evolution. The Euclidean signature and the Minkowski signature are related by the deformation of the integration contours of dynamic variables in a discrete lattice functional integral. It is important that the result is obtained directly on the lattice. Since the studied lattice theory of gravity in the long-wave limit transforms into the well-known Einstein-Cartan-Palatini theory, the obtained result means that this lattice theory of gravity has the right to be considered as a discrete regularization of the generally accepted continuous physical theory of gravity.

We develop a theoretical framework, using the slow variables method in the RSJ model, and perform numerical simulations to explain the peculiarities of the Josephson diode effect observed in an asymmetric SQUID with a superconducting nanobridge and an SNS junction in recent experiments by Vasiliy Stolyarov’s group at MIPT. For this case we predict the new (amplitude) mechanism of the diode effect which originates from the presence of a superconducting nanobridge exhibiting a multivalued current-phase relation (CPR). Theoretically, this mechanism manifests itself in the dependence of the amplitude of the first Josephson harmonic in the CPR of the SQUID on the current direction. We demonstrate that this mechanism accounts for the experimentally observed pronounced asymmetry of the Shapiro steps, which coexists with a relatively small asymmetry in the critical current. Additionally, we investigate how the diode efficiency (quantified via the Shapiro steps asymmetry) depends on both the magnetic flux through the superconducting loop and the power of the external microwave irradiation. Our theoretical predictions are found to be in good agreement with the experimental observations. This talk is based on the article Phys. Rev. B 112, 144504 (2025).

The Novikov problem on the level lines of quasiperiodic potentials on a plane with additional (quasi-crystalline) symmetry is considered. For potentials of this type, the possibility of the emergence of open level lines at only a single energy level is shown in the general case. Possible estimates of the growth rate of closed level lines as the energy approaches the percolation threshold are also discussed.

We study triggered by an a.c. external electric field weakly nonlinear stages of flexoelectric instability in nematic liquid crystals. The instability occurs at a finite wave vector. We analyze behavior on time scales much larger than the period of the external electric field. We focus on the case where the increment of the most-unstable mode has an imaginary part, so-called Hopf bifurcation. The existence of such regime was established in our previous work [E.S. Pikina, A.R. Muratov, E.I.Kats, V.V. Lebedev, Dynamic flexoelectric instabilities in nematic liquid crystals, Phys. Rev. E, 110, 024701 (2024)]. Then above the instability threshold a variety patterns of nematic director distortions could appear including standing and travelling structures. Our numerical simulations based on the full nonlinear electro-nematodynamics system of equations. We found that the stable dynamic pattern in the vicinity of the Hopf bifurcation travelling oblique rolls of the nematic director distortions. The establishment of this regime occurs abnormally slowly, which is determined not only by the critical Landau-like slowdown of dynamics, but also by the presence of a long-lived intermediate unstable but long-lived dynamic patterns oscillating in time (standing but not traveleling rolls). Depending on liquid crystal material parameters, the bifurcation corresponding to the formation of the travelling oblique rolls, can be soft (i.e.continues, ‘’critical’’ or close to ‘’tricritical’’ one), or hard (discontinues).