Physics

We employ a two-dimensional fluid simulation approach to study the nonlinear turbulent dynamics of internal gravity waves (IGWs) in the weakly ionized Earth’s ionospheric F-layer with the effects of Pedersen conductivity. We observe that the presence of Pedersen conductivity leads to the formation of intermediate-scale structures in the velocity potential, along with the development of small-scale density fluctuations. The characteristic turbulent energy spectrum exhibits a non-Kolmogorov scaling of $k^{-2.40}$ in the presence of Pedersen conductivity, while a Kolmogorov-like $k^{-5/3}$ scaling is observed when it is absent, where k denotes the wave number. Due to energy loss caused by Pedersen conductivity, the wave’s amplitude reduces gradually with time. The cross-field diffusion coefficient related to the velocity potential also reduces as Pedersen conductivity increases. The results in the F-layer are compared with those in the literature, where the Ampère force and hence the Pedersen conductivity effect were ignored compared to the pressure gradient and gravity forces, as relevant in the Earth’s D-layer. Full article

Models for dual cascades in power-spectra for fully three-dimensional (3D) incompressible turbulence are reviewed and summarized. Special attention is given to analyses where the basic equations for 3D incompressible flows are expanded in terms of the eigenfunctions for the curl-operator. The possibilities for forward and inverse cascades in 3D fluid turbulence are illustrated and quantified. Conditions for dual- and forward-energy cascades in wavenumber space are presented. The forward or unidirectional cascade is found to dominate, a result consistent with the basic physical arguments formulated by vortex-line stretching. The analysis gives additional details to quantify the cascade conditions including dual cascades. Selected initial or boundary value conditions can give transient space or time intervals, where a dual cascade is dominating. Full article

We show how a source-aware fluid closure framework for turbulent transport performs well on the confinement timescale in magnetically confined plasmas. A central result is that whether a source is resonant with the turbulence determines which fluid moments must be retained. Using a nonlinear current formulation, we show that resonance broadening—the dominant kinetic nonlinearity—cancels linear resonances and thereby justifies a quasilinear fluid closure already on the turbulence timescale. We derive a practical negative-energy criterion and identify parameter regimes satisfied by ion-temperature-gradient (ITG) modes (slab and toroidal), with parallel ion compressibility and magnetic curvature controlling the sign. The framework clarifies when velocity-space dynamics must be retained in the kinetic Fokker–Planck equation (for example, for fast-particle instabilities at frequencies about 10² higher than drift-wave frequencies). The present study provides additional support for our model by predicting transport that increases with radius and by showing—consistent with nonlinear kinetic simulations—that the diamagnetic flow dominates the Reynolds stress. Altogether, the results obtained provide a consistent, reduced-cost path to fluid closures that retain the essential kinetic physics while remaining tractable on confinement timescales. Full article

We present a brief review of a nontraditional but significant application for a high-temperature charged plasma. The unorthodox proposition was made by Barry Ninham concerning a contribution from Casimir forces across high-temperature electron–positron plasma in nuclear interactions. The key message in this review is that high temperatures (about ${10}^{11}$ K) are found to be essential. Certainly, classical, semi-classical, and quantum considerations for the background media impact both the Casimir effect and the physics of stars and the Universe. Full article

We analyze shortcuts to adiabaticity (STA) and their completions for the quantum harmonic oscillator (QHO) with time-dependent frequency, as well as for quantum field theory (QFT) in non-stationary backgrounds. We exploit the analogy with one-dimensional quantum mechanics, and the known correspondence between Bogoliubov coefficients in the QHO and transmission/reflection amplitudes in scattering theory. Within this framework, STA protocols for the QHO are equivalent to transmission resonances, while STA in QFT with homogeneous backgrounds correspond to reflectionless potentials. Moreover, using the connection between particle creation and squeezed states, we show how STA completions can be understood in terms of the anti-squeezing operator. Full article

Laser-induced breakdown spectrometry (LIBS), known as an express analysis technique, is for the first time applied in this study for determining selenium in soil. Modern agriculture requires elemental analysis methods to perform the continuous automated online control of microelement content in soil. However, selenium has never been quantitatively determined in soil by LIBS so far. Different sample preparation techniques (loose soil powder, mounted on adhesive tape and tableted soil) are employed here for LIBS determination of selenium in soil. The optimal choice of analytical line is challenging for selenium because of spectral interference with the minor and major soil components (Fe, Si, Zn, Al, Sb), but the Se I 196.09 nm line has the lowest spectral interference. A limit of detection of 3 mg/kg for selenium in soil is achieved in the present study using LIBS. The analytical performance of tape-mounted and loose soil powder samples with appropriate data averaging is found to be comparable to that achieved for tablets. Full article

We present two complementary approaches to the Gorini–Kossakowski–Sudarshan–Lindblad equation for an open qubit. First, based on linearity, yields solutions illustrated by mixed-state trajectories in the Bloch ball, including non-random asymptotic fixed points and exceptional points. Second, exploiting the SU$\left(2\right)$ symmetry, leads to a nonlinear dynamical system that separates angular dynamics from radial dissipation. This symmetry-based perspective presents a promising route toward generalization to open qudits. Full article

The Spanish conquest of the Inca empire in the early 16th century stands as one of the most striking examples of asymmetric historical collapse. In this paper, a simplified mathematical formulation is developed being inspired by Lotka–Volterra dynamics to describe, in a stylized quantitative manner, the interactions between the Inca state and the invading Spanish forces. The model is not intended to explain the historical events in a causal or predictive sense, but rather to capture and represent key mechanisms commonly identified in historical analyses. These include the demographic and political weakening caused by smallpox epidemics prior to direct contact, the internal fragmentation produced by the civil war and the introduction of external shocks such as the capture of Atahualpa and the fall of Cusco. Although intentionally minimalistic, the framework provides a dynamical illustration of how combined internal and external pressures can destabilize a complex society. This descriptive perspective situates the Inca collapse within the broader conceptual language of complex systems, emphasizing how nonlinear interactions, feedback and structural asymmetry shape trajectories of resilience and failure. Full article

Polyurea, a novel spray-applied composite polymer, is of high application importance for rapid roadway support in coal mines. The current study investigates the dynamic process and mechanisms governing the impact and spreading of polyurea droplets on rough surfaces through experimental and theoretical approaches. The key novelty lies in revealing how spontaneously varying viscosity couples with surface microstructure to produce novel scaling laws distinct from classical Newtonian behavior. The droplet impact and wetting process can be divided into three stages. In the pinning stage, droplet behavior is dominated by kinetic energy, leading to inertia-driven spreading in which the contact line radius increases quite slowly with time. In the penetration stage, the apparent three-phase contact line (TPCL) is pinned by surface microstructures, while the real TPCL evolves with time following a temporal scaling law t^3/2. In the spreading stage, surface roughness becomes decisive. On low-roughness substrates, limited pinning allows the real and apparent TPCLs to spread synchronously, with TPCL evolution governed by surface tension and viscous forces, following a t^1/8 scaling law. As roughness increases, pinning effects strengthen, causing divergence: the real TPCL is driven by surface tension and viscous dissipation between microstructures, whereas the apparent TPCL is additionally influenced by pinning and reaction-induced viscosity, scaling as t^1/24. This t^1/24 scaling for the apparent contact line on relatively high-roughness surfaces represents a significant deviation from established scaling relations. Experiments on rock-like substrates confirm these mechanisms for polyurea droplets. These findings provide theoretical and engineering guidance for optimizing spray-coating parameters in coal mines, with the goal of improving coating uniformity and interfacial adhesion. Full article

We present the effective optical potential describing the interaction between an electron and a neon atom in a dense plasma. This potential accounts not only for the screening effect but also for the quantum non-locality and electronic correlation effects, which lead to an increase in the interaction energy between the electron and the neon atom. Within this framework, differential and momentum transport cross-sections for elastic electron–neon scattering are determined. The obtained results are compared with the available experimental data and theoretical predictions, showing exceptionally good agreement. Full article

The environmental pollution caused by emerging organic contaminants—such as ibuprofen—is becoming increasingly a cause for alarm. New treatments for their removal are currently being developed, but the nature and toxicity of the transformation products (TPs) formed during the processes cannot be readily assessed experimentally. Atomistic simulations are thus of high interest in predicting the chemical structure of these TPs. In this paper, we demonstrate that the transformation of a contaminant molecule under irradiation can be studied using the threshold algorithm combined with the density functional-based tight-binding (DFTB) method. The fragmentation pathways of an ibuprofen molecule under irradiation are studied as a function of the energy added to the system. Specifically, the chemical structures of ibuprofen’s TPs, the paths between them, their stabilities, probabilities of occurrence, and the related mass spectra were obtained as a function of the amount of energy absorbed. We also simulated the evolution of the ibuprofen molecule as a function of the number of pulses, i.e., for a sequence of energy depositions. A dominant fragmentation scheme is identified, where first the OH group is released, followed by the loss of the CO group. The photon energy and the number of pulses are found to be key parameters for the selection of this degradation route among all identified fragmentation pathways. Full article

First-principles calculations of the structural and magnetic properties of kotoite Ni₂Co(BO₃)₂ are carried out. The minimization of the lattice parameters shows the values to be in good agreement with the experimental data (the difference is less than 1%). The atomic coordinates are calculated. Cobaltions are found tending to occupy position 2a and nickel ions tending to occupy position 4f. The same magnetic cell as in Ni₃(BO₃)₂, but quadrupled in size (2a × b × 2c), found having the minimum exchange energy for Ni₂Co(BO₃)₂. In Ni₂Co(BO₃)₂, the magnetic moments are obtained oriented along the baxis, similar to that in Co₃(BO₃)₂. Full article

The cosmological constant (CC, $\Lambda$) problem stands as one of the most profound puzzles in the theory of gravity, representing a remarkable discrepancy of about 120 orders of magnitude between the observed value of dark energy and its natural expectation from quantum field theory. This paper synthesizes two innovative paradigms—holographic naturalness (HN) and pre-geometric gravity (PGG)—to propose a unified and natural resolution to the problem. The HN framework posits that the stability of the CC is not a matter of radiative corrections but rather of quantum information and entropy. The large entropy $S_{\mathrm{dS}}\sim M_{\mathrm{P}}^2/\Lambda$ of the de Sitter (dS) vacuum (with $M_{\mathrm{P}}$ being the Planck mass) acts as an entropic barrier, exponentially suppressing any quantum transitions that would otherwise destabilize the vacuum. This explains why the universe remains in a state with high entropy and relatively low CC. We then embed this principle within a pre-geometric theory of gravity, where the spacetime geometry and the Einstein–Hilbert action are not fundamental, but emerge dynamically from the spontaneous symmetry breaking of a larger gauge group, SO($1,4$)→SO($1,3$), driven by a Higgs-like field ${\varphi }^A$. In this mechanism, both $M_{\mathrm{P}}$ and $\Lambda$ are generated from more fundamental parameters. Crucially, we establish a direct correspondence between the vacuum expectation value (VEV) v of the pre-geometric Higgs field and the de Sitter entropy: $S_{\mathrm{dS}}\sim v$ (or $v^3$). Thus, the field responsible for generating spacetime itself also encodes its information content. The smallness of $\Lambda$ is therefore a direct consequence of the largeness of the entropy $S_{\mathrm{dS}}$, which is itself a manifestation of a large Higgs VEV v. The CC is stable for the same reason a large-entropy state is stable: the decay of such state is exponentially suppressed. Our study shows that new semi-classical quantum gravity effects dynamically generate particles we call “hairons”, whose mass is tied to the CC. These particles interact with Standard Model matter and can form a cold condensate. The instability of the dS space, driven by the time evolution of a quantum condensate, points at a dynamical origin for dark energy. This paper provides a comprehensive framework where the emergence of geometry, the hierarchy of scales and the quantum-information structure of spacetime are inextricably linked, thereby providing a novel and compelling path toward solving the CC problem. Full article

We consider a model problem of polarization-dependent light bending and time delays in the vicinity of neutron stars endowed with magnetar-strength magnetic fields (B∼${10}^{15}\mathrm{G}$), combining an effective-metric formulation of Heisenberg–Euler nonlinear electrodynamics with general-relativistic ray tracing. The spacetime geometry is analyzed using both the Kerr metric and a quadrupole-deformed q-metric, characterized by a quadrupole parameter varying in the range $q\in [{10}^{-3},0.5]$. In addition, the impact of complex magnetic-field topologies is examined by introducing a magnetic quadrupole component alongside the dipole configuration. The simulations performed in this study demonstrate that the inclusion of the quadrupole deformation parameter significantly modifies photon trajectory deflections compared to the standard Kerr solution. We further quantify the geometric dilution of the photon beam, finding a cross-section expansion ratio of approximately $4.7\times {10}^{13}$ for rays reaching Earth. This strong dilution imposes stringent constraints on the detectability of polarization-dependent signatures and time-delay echoes. Finally, characteristic illustrations are presented for trajectory distortions, bending-angle distributions, and intensity valleys produced by the combined gravitational and magnetic lensing effects. Full article

By solving the three-dimensional Schrödinger equation with a second-order implicit Finite Difference Method (FDM), the combined effects of temperature, morphology, hydrostatic pressure, and transverse electric field on the nonlinear optical rectification (NOR) of GaAs/Al_εGa_1−εAs elliptical quantum rings are examined. The NOR amplitude is twelve times enhanced and a noticeable blue shift is induced in the THz region when the electric field is increased. Consequently, with the electric field of 1 × 10⁵ V/m, the NOR magnitude achieves its maximum value of 17.116 × 10⁵ m/V. Additionally, when the electric field is aligned along one side of the system’s in-plane cross-section, the strongest amplification takes place. However, with corresponding spectrum shifts, the NOR intensity rises with temperature and falls with hydrostatic pressure. Additionally, changing the transverse profile of the quantum ring from triangular to parabolic broadens the carrier wave functions and has a considerable impact on the NOR coefficient. These findings provide important information for the construction of high-performance, tunable THz optoelectronic devices by demonstrating effective external and structural tuning of NOR. Full article

In this study, we present the custom development and implementation of a mobile application designed specifically to experiment with Malus’s law, leveraging the integration of a LEGO EV3 and the light sensor of a mobile device. Unlike previous studies that utilize pre-designed mobile applications, our approach focuses on creating a tailored solution that meets the unique requirements of this optical experiment. Using MIT App Inventor, we developed a customized interface that allows for the rotation of polarizers controlled by motors connected to a LEGO EV3 while simultaneously measuring the light intensity using the mobile’s light sensor. The block-based programming in App Inventor facilitates the application of programming concepts in creating physics experiments in a straightforward manner. This innovative approach not only facilitates the understanding of fundamental optical concepts but also integrates accessible technology to enrich the educational experience in physics, offering a customizable solution adaptable to various educational settings. Preliminary results indicate a significant improvement in students’ comprehension of optical polarization principles, demonstrating the effectiveness of our approach. Full article

The quantizer–dequantizer method is employed. Using the construction of probability distributions describing density operators of a quantum system states, the connection between the Feynman path integral and the time evolution of the density operator (Landau density matrix) as well as the wave function of the stateconsidered. For single–mode systems with continuous variables, a tomographic propagator is introduced in the probability representation of quantum mechanics. An explicit expression for the probability in terms of the Green function of the Schrödinger equation is obtained. Equations for the Green functions defined by arbitrary integrals of motion are derived. Examples of probability distributions describing the evolution of state of a free particle, as well as states of systems with integrals of motion that depend on time (oscillator type) are discussed. Full article

Over the past thirty years, the focus in singular optics has been on structured beams carrying orbital angular momentum (OAM) for diverse applications in science and technology. However, as practice has shown, the OAM-free structured Gaussian beams with several degrees of freedom are no worse than the OAM beams, especially when propagating through turbulent flows. In this paper, we partially fillthis gap by theoretically and experimentally mapping cyclic changes in vortex-free states (including OAM) as a phase portrait of the beam evolution in an astigmatic optical system. We show that those cyclic variations in the beam parameters are accompanied by the accumulation of the geometric Berry phase, which is an additional degree of freedom. We find also that the geometric phase of cyclic changes in the intensity ellipse shape does not depend on the radial numbers of the Laguerre–Gaussian mode with zero topological charge and is always set by changing the shape of the Gaussian beam. The Stokes parameter formalism was developed to map the beam states’ evolution onto a Poincaré sphere based on physically measurable second-order intensity moments. Theory and experiment are found to be in a good enough agreement. Full article

We present the concept of an ultracold neutron (UCN) source with a superfluid He-4 (SF ⁴He) converter located in the thermal column of the WWR-K research reactor at the Institute of Nuclear Physics (INP) in Almaty, Kazakhstan. The conceptual design is based on the proposal of accumulating UCNs in the source and effectively transporting them to experimental setups. We propose to improve the UCN density in the source by separating the heat and UCN transport from the production volume and decreasing the temperature of the SF ⁴He converter to below about 1 K. To obtain operation temperatures below 1 K, we plan to use a He-3 pumping cryogenic system and minimize the thermal load on the UCN accumulation trap walls. Additional gain in the total number of accumulated UCNs can be achieved through the use of a material with a high critical velocity for the walls of the accumulation trap. The implementation of such a design critically depends on the availability of materials with specific UCN and cryogenic properties. This paper describes the conceptual design of the source, discusses its implementation methods and material requirements, and plans for material testing studies. Full article