Abstract Turbulent polymeric flows show strong deviations from Kolomogorov-like behaviour resulting from more complex dynamics compared to Newtonian turbulence. We now study the nature of mixing in polymeric turbulence via Eulerian passive scalar fields of varying molecular diffusivities, given by the Schmidt number Sc. We show that polymeric turbulence is a less efficient mixer than the Newtonian one at small to moderate Sc numbers. Newtonian scalar turbulence (NST) forms large islands of fluctuations with extended, contiguous fronts. In contrast, polymeric scalar turbulence (PST) is marked by small, interspersed patches of strong but less intermittent fluctuations. These patches collectively comprise a larger volume fraction of strong fluctuations, indicating a less efficient mixing, alongwith smaller gradients and therefore smaller scalar flux across their boundaries. We also show that PST shows a novel, distinct self-similarity with the scalar fluctuation spectrum scaling as $k^{-4/3}$ as opposed to $k^{-5/3}$ in NST. Real space statistics also reveal that, while fluctuations are stronger in PST, they remain less intermittent.
Abstract We uncover universal features of nonequilibrium phase transitions in all-to-all Ising models coupled to two thermal reservoirs with arbitrary temperatures, interactions, and external drivings. We show that the symmetry of external parameters fundamentally controls the nature of phase transitions: symmetric drivings allow for continuous, discontinuous, and tricritical behavior, whereas antisymmetric drivings suppress the tricriticality, yielding only critical or discontinuous transitions. Remarkably, in the latter case and in the fast-switching limit, the nonequilibrium stationary distribution acquires a Boltzmann-Gibbs–like form irrespective of the model details,. Our work sheds light on the differences between equilibrium and nonequilibrium ingredients and genuinely nonequilibrium features in collective phase transitions.
Abstract It is shown explicitly within a purely world framework that any formal Weyl-like tensor in a curved spacetime which occurs in the realm of Einstein-Cartan's theory may never vanish identically. This property reinstates a result obtained earlier in connection with the derivation of a two-component spinor expression for such a tensor, whereby it is not possible to attain in a spacetime endowed with a torsionful affinity any general condition for conformal flatness that might resemble in form the classical one of general relativity. Some elementary features of the existing torsional cosmological models are likewise brought forward.
Abstract Urban noise pollution has become a significant threat to public health, and traditional soundproof windows often fail to meet ventilation requirements. This paper proposes a novel ventilated soundproof structure based on Archimedean spiral acoustic metamaterials (ASMs). The structure consists of two ventilation channels of equal width on both sides and a centrally mirrored, asymmetrically arranged Archimedean spiral channel. By leveraging the linear resonance effect of the spiral channels to regulate sound wave propagation, the design achieves an efficient balance between sound insulation and natural ventilation. Through a combination of finite element simulations and experimental testing, the study systematically investigates the effects of parameters such as inner and outer diameters, polar angle, and thickness on sound insulation performance. Results show that the ventilated soundproof window achieves transmission loss greater than 13.5 dB within the 525-895 Hz frequency range. Additionally, increasing the inner diameter broadens the operational frequency band but reduces sound insulation effectiveness, while enlarging the outer diameter enhances sound insulation performance at the expense of ventilation rate. Adjustments to the polar angle and thickness further optimize the frequency characteristics.
Abstract This study presents predictions for the low-energy cross-section set and analyses the kinetics of molecular hydrogen ions in argon, which represents a crucial step toward reliable modelling of various technologically significant processes. Although ions can be detected in such plasmas, the conditions in an idealized, isolated system, where only their interaction with argon atoms is considered, differ significantly. Under these conditions, ions undergo rapid destruction, leading to a disruption of the hydrodynamic regime of the charged-particle ensemble. To accurately determine the kinetic properties in this non-hydrodynamic regime, a Monte Carlo simulation method is employed. As functions of weak and moderate reduced electric fields, the following kinetic quantities are provided: bulk and flux velocities, half-life, mean free path, diffusion coefficients and reaction rate coefficients. It is shown that, due to rapid ion loss through reactive collisions, the transport characteristics evolve toward well-defined asymptotic limits without establishing steady-state conditions during the swarm lifetime.
Abstract Pentamode metamaterials (PMs) are characterized by their unique solid morphology and fluid properties, and hold significant potential for underwater acoustic control. However, the pentamode metamaterials based on the spring-mass model, which is formed by a simple connection of soft and hard materials, have been unable to achieve both excellent acoustic properties and pressure resistance in the low-frequency range. Here, a three-dimensional three-layer symmetric double-cone element which was inspired by “hamburger” is proposed. Systematically, by using the finite element method and pressure resistance theory, the low-frequency acoustic characteristics such as single mode, phonon bandgap, figure of merit and critical force are studied. The results show a broader single-mode region with a maximum single-mode frequency difference of 1679.25 Hz. Additionally, the figure of merit remains above 150 across the entire operating range. Furthermore, through mechanical analysis, it was found that this structure exhibits remarkable universality and pressure resistance. Compared to traditional PMs, the pressure resistance has been improved by 222%. This research provides a useful solution to the instability issue of pentamode metamaterials in the low-frequency range, and offers theoretical guidance for their application in low-frequency acoustic wave control underwater.
Abstract The dispersion characteristics of bounded dust acoustic (DA) waves in an ultradense cylindrical Thomas-Fermi dusty plasma are investigated using a fluid model approach. Dispersion properties —including frequency, phase and group velocities— are systematically compared between the cylindrical geometry and the one-dimensional planar limit. The results demonstrate that radial confinement modifies the propagation characteristics of DA waves in the long-wavelength regime, thereby distinguishing the cylindrical configuration from its planar counterpart. In the short-wavelength limit, both systems approach the same saturation frequency, accompanied by strong radial energy localization. Furthermore, the theoretical analysis reveals a distinctive feature of completely degenerate dusty plasmas: the wave frequency increases monotonically with the Havnes parameter H . This prediction stands in quantitative contradiction to the experimentally observed inverse relationship for classic dusty plasmas. The findings of this work are critically relevant to the design of dusty plasma waveguides, the stability analysis of dust crystals, and the diagnostic characterization of laboratory and astrophysical dusty plasmas.
Abstract Channel-driven inertial fusion offers precise control over energy deposition and hot-spot formation by guiding high-intensity ion beams through pre-formed low-density plasma channels. In this study, we present a fully PIC-enhanced comparative analysis of three candidate fusion fuels —deuterium–tritium (D–T), deuterium–helium-3 (D–He 3 ), and proton–boron-11 (p–B 11 ). Radial plasma dynamics, energy deposition, hot-spot temperature evolution, fusion reactivity, and gain metrics are quantified across a 10–500 keV temperature range. D–T demonstrates the fastest radial compression, highest central energy deposition, and the most efficient fusion gain, whereas D–He 3 requires higher confinement and temperature, and p–B 11 demands extreme energy input due to its higher Coulomb barrier. Normalized Lawson proxies and fusion gain metrics provide quantitative insight for fuel selection in both near-term D–T applications and long-term aneutronic fusion strategies. This work establishes a roadmap bridging numerical simulation and experimental design for high-efficiency, low-radioactivity fusion energy.
Abstract Controlling both amplitude and frequency concurrently in a nonlinear dynamical system is a challenging problem. We propose a hybrid control scheme that combines unidirectional drive-response (DR)–type coupling along with linear augmentation (LA) of a nonlinear dynamical system to achieve simultaneous regulation of both quantities. Unidirectional DR-type coupling effectively synchronizes the response oscillator frequency with that of the driver, while maintaining the response amplitude unchanged. The addition of control through LA in response system dynamics stabilizes the oscillatory state, enabling amplitude regulation. The effectiveness of the proposed scheme is demonstrated using Stuart-Landau and Van der Pol limit cycle oscillators, revealing its ability to achieve control and offering a unified framework for amplitude-frequency regulation in nonlinear oscillators.
Abstract For over a century, the fine-structure constant ( α ) has remained one of the most enigmatic dimensionless numbers in physics, often relegated to the realm of pure numerology. In this work, we provide a physical foundation based on the Fluctuation-Dissipation Theorem (FDT). By establishing an identity between the electromagnetic coupling strength and the reciprocal of the photon-number variance within a black-body cubic cavity, we demonstrate that these quantities correspond to a dynamic “line constant” rather than a static value. We show that the Sommerfeld value emerges as a resonance condition where the geometric confinement scale ( L = 3.3 cm) and the thermal energy of the emission fine-structure line (equivalent temperature of 0.516 K) satisfy a reciprocal duality between the field strength (stiffness) and the photon gas fluctuations (compliance). This statistical framework extends to the entire Mendeleev table of elements, suggesting that atomic properties are local manifestations of vacuum fluctuations of the photon gas.
Abstract This work re-examines the mean effective viscosity theory for polymer drag reduction (DR) in turbulent wall-bounded flows by proposing a closure-free validation of the effective viscosity theory originally proposed by Benzi et al. [1]. By introducing a novel polymer stress decomposition that distinguishes between extended and unextended macromolecules, we show that the polymer stress can be described in terms of an effective viscosity profile, plus a fluctuating contribution that vanishes in the Maximum Drag Reduction regime. The slope of the effective viscosity profile is related to the slope of the wall-normal mean square polymer extension of the fully stretched population contributing to DR.
Abstract Wavelets localize position and scale, but the nondispersive wave equation organizes high-frequency energy on characteristic cones. This Letter gives a quantitative obstruction to using ordinary isotropic wavelets as atoms of cone-concentrated propagation and shows how it is removed by adding Lorentz rapidity. The analysis is a finite-window microlocal benchmark for band-limited packets near one regular branch of the cone. In light-cone frequency variables, a normalized wave packet with transverse cone width $\eps$ has covariance $\diag(1,\eps^2)$. Its largest possible squared overlap with any isotropically dilated Gaussian wavelet is exactly $4\eps/(1+\eps)^2$, whereas a boosted wavelet, or boostlet, with rapidity $\theta=\frac12\log \eps^{-1}$ and scale $a=\eps^{-1/2}$ matches the covariance and attains unit overlap, up to the exponentially small admissibility correction of a Morlet window. Hence an isotropic wavelet expansion has entropy at least $\log[(1+\eps)^2/(4\eps)]$ and requires $\Omega(\eps^{-1})$ coefficients to capture fixed energy, while one boostlet coefficient suffices in the local Gaussian model. A weak quartic cone deformation produces a boostlet sparsity defect proportional to $\lambda^2K^6/\eps^2$ under the stated perturbative scale assumption.
Abstract For the dinuclear spin crossover [Fe(qsal) 2 ][Ni(dmit) 2 ], (where qsal = N(8quinolyl)salicylaldimine and dmit 2-= 1,3-dithiol-2-thione-4,5-dithiolato) complex, elemental X-ray magnetic circular dichroism (XMCD) measurements at the Fe and Ni L 3,2 X-ray absorption edges indicate antiferromagnetic alignment of the Fe and Ni. This anti-ferromagnetic alignment is consistent with the ab initio calculations performed using the DFT+U method. The DFT+U calculations indicate that while the moments residing in the Fe cation are localized on the metal, there is a significant delocalization of the spin density on the Ni(dmit) 2 moiety, with considerable magnetic moment associated with the ligand. This placement of some moment on the dmit ligand explains the XMCD signal at photon energies well above the metal absorption edge. This dmit ligand moment is consistent with the large inverse photoemission signal that is most sensitive to the surface layer dmit, the known surface termination of [Fe(qsal) 2 ][Ni(dmit) 2 ]. The organic ligand clearly can mediate antiferromagnetic coupling between metal centers with significant separation.
Abstract We report by ab initio calculations an all-sp3 hybridized carbon allotrope with Ia3d symmetry containing 152 carbon atoms, the carbon atoms form all-six-membered carbon rings. The equilibrium energy of bcc-C152 carbon is lower than the previously reported BC12, BC8, R16, and O16 carbon. The dynamical stability of bcc-C152 carbon has been confirmed with phonon band spectrum calculations, its thermal stability up to 1000 K has been confirmed using ab initio molecular dynamics simulations. The electronic band structures calculations show that bcc-C152 is a semiconductor with a direct band gap about 2.82 eV. Simulated x-ray diffraction patten of bcc-C152 carbon, which shows an excellent match with the experimental data derived from the milled fullerene soot. Previously the R16 carbon was proposed to explain this experiment, the bcc-C152 carbon shows a better match with this experiment and has lower equilibrium energy, so bcc-C152 is a more competitive explanation.
Abstract We study the (2 + 1)-dimensional Duffin-Kemmer-Petiau equation for spin-1 bosons in a noncommutative phase space under a uniform magnetic field. By introducing an effective frequency that incorporates the magnetic interaction and noncommutative parameters, the energy spectrum is split into two regions separated by critical frequencies. These points mark a change in the spectral structure, while preserving the energy continuity. The corresponding magnetic response is derived analytically and exhibits discontinuities at the critical frequencies, providing a clear signature of the transition between the spectral regions. The results show how phase-space noncommutativity modifies both the spectrum and its magnetic response.
Abstract New results of the experimental search for dark matter using the isomer are presented. To measure the γ -spectra of the isomer target, an anti-Compton spectrometer has been used in the γ - γ coincidence mode. γ -rays that usually are not emitted during the spontaneous decay of this isomer but might arise from the population of excited nuclear levels in 178 Hf due to the inelastic scattering of dark matter particles are analyzed in detail. The combined limit on the half-life of the dark-matter–induced transitions, obtained from limits on these γ -ray intensities, has reached 10 5 years for 10 + , 9 + , 8 + and 7 + excited levels of the rotational band built on the , 6 level with energy of 1553.997 keV. The influence of the model-dependent nuclear form factor on constraints for the inelastic scattering cross-section on nucleon and further progress of such experimental and computational efforts are discussed.
Abstract The spin-orbit coupling of star-planet systems results from the competition between magnetic braking and tidal interactions, especially in systems hosting close-in gas giants. In this work, we apply the non-extensive tidal index q , which we introduced in a previous study based on the Tsallis statistical formalism, to a restricted working sample of cool main-sequence exoplanet hosts with measured stellar rotation periods and the stellar, planetary and orbital parameters required to evaluate tidal coupling. The index q is computed directly from observable stellar and planetary parameters, providing a physically grounded proxy for the strength of tidal coupling. Our dataset spans planetary masses from 0.0017 to and orbital periods from 0.28 to 282.5 days and F-, G-, K-, and M-type host stars. We find that most close-in giants in our sample exhibit and orbit inside the stellar corotation radius, a configuration consistent with enhanced tidal coupling. We also identify systematic trends between q and planetary mean density, stellar rotation, and corotation radius, with high- q systems preferentially associated with inflated, low-density gas giants around rapidly rotating stars. These results suggest that q can be a useful diagnostic of the observed tidal state of close-in giant exoplanets, tracing long-term spin-orbit coupling and proximity to corotation within the restricted parameter space explored here.
Abstract Post-inhibitory rebound (PIR) spiking, as an alternative firing mechanism triggered after an inhibitory input, is important for maintaining neurophysiological functions. In this paper, inhibitory networks composed of type-II and type-III neurons are constructed separately to explore the effects of PIR spikes on network activity. We found that, through PIR spikes generated by mutual inhibitory inputs among neurons, the networks exhibit persistent firing activity with different synchronous patterns. Networks of type-II neurons exhibit a higher tendency toward synchronization than those of type-III neurons. Furthermore, noise is found to affect network synchronization by regulating PIR spiking. Moderate noise can enhance synchronization by facilitating PIR spiking, and strong noise can reduce synchronization by suppressing PIR spiking. Networks of type-III neurons have better anti-noise capability. This study not only demonstrates differences in synchronization regulation between type-II and type-III neurons in inhibitory networks, but also reveals how noise affects synchronization by modulating PIR spiking.
