Field Perturbations Research Articles

Interaction of upper hybrid waves with dust-ion-magnetoacoustic waves and stable two-dimensional solitons in dusty plasmas

We obtain a two-dimensional (2D) nonlinear system of equations for the electrostatic potential envelope and the low-frequency magnetic field perturbation to describe the interaction of the upper hybrid wave propagating perpendicular to an external magnetic field with the dust-ion-magnetoacoustic (DIMA) wave in a magnetized dusty plasma. The equations contain both scalar and vector nonlinearities. A nonlinear dispersion relation is derived, and the decay and modulation instability thresholds and growth rates are obtained. Numerical estimates show that instability thresholds can easily be exceeded in real dusty plasmas. In the static (subsonic) approximation, a 2D soliton solution (ground state) is found numerically by the generalized Petviashvili relaxation method. The perturbations of the magnetic field and plasma density in the soliton are nonmonotonic in space, and, along with the perturbation in the form of a well, there are also perturbation humps. Such peculiar radial soliton profiles differ significantly from previously known results on 2D solitons. The key point is that the presence of a gap in the DIMA wave dispersion due to the Rao cutoff frequency causes the nonlinearity to be nonlocal. We show that due to nonlocal nonlinearity the Hamiltonian is bounded below at fixed energy, proving the stability of the ground state.

Evidence of Unusually Strong Equatorial Ionization Anomaly at Three Local Time Sectors During the Mother's Day Geomagnetic Storm On 10–11 May 2024

AbstractThis study uses multiple ground and satellite‐based measurements to investigate the extreme ionospheric response to the Mother's Day storm on May 10–11, 2024. Prompt penetration electric field caused a significant enhancement in the ionospheric vertical drift ( 95 m/s) and the equatorial electrojet strength ( 275 nT) over Jicamarca. These extreme eastward electric field perturbations, along with the large meridional wind, significantly altered the F‐region plasma fountain at different local times. The afternoon equatorial ionization anomaly (EIA) not only sustained for an exceptionally long duration ( 12 hr) but also expanded spatially over time. The separation between the two peaks of EIA crests exceeded and in the morning and evening sectors, respectively. This study shows, for the first time, that unusually strong EIA can not only develop at different local times but can also sustain for long duration under favorable conditions, which has implications for space weather applications.

Evidence for magneto-gravitational processes in supermassive black hole binary PG 1553+113

ABSTRACT PG 1553+113 has drawn significant attention for its quasi-periodic oscillation (QPO) in $\gamma$-ray variability, though the origin of its variability remains uncertain. In this study, we propose a physical mechanism to explain the observed $\gamma$-ray variability within the framework of a supermassive black hole binary (SMBHB) system, supported by a newly identified component hidden in the light curve. A detailed analysis for its $\sim$16-yr light curve obtained from Fermi-LAT observations is performed by Gaussian process. As anticipated, the QPO of 2.1 yr ($771\pm 8$ d) is effectively captured by the stochastically driven damped simple harmonic oscillator kernel within the underdamped regime, and the overall stochastic nature of the variability is described by the damped random walk (DRW) kernel albeit with an unconstrained damping time-scale. Additionally, our results reveal a previously unrecognized component in active galactic nuclei variability, characterized by the Mat$\acute{\rm e}$rn$-3/2$ kernel, which is typically associated with systems undergoing abrupt energy release. These findings can be consistently interpreted within the SMBHB framework. The QPO of $\sim$2.1 yr is likely attributed to the orbital motion in a SMBHB system. The Mat$\acute{\rm e}$rn$-3/2$ component is interpreted as resulting from magnetic reconnection events triggered by gravitational perturbations of the magnetic field within the jet, occurring as one black hole approaches the other. Meanwhile, in this case, the damping time-scale of the common DRW kernel remains unconstrained due to the influence of new perturbations within the system.

Scalable Synthesis of 2D ErOCl with Sub-meV Narrow Emissions at Telecom Band.

Van der Waals (vdWs) materials are promising candidates for hetero-integration with silicon photonics toward miniaturization and integration. VdWs materials like molybdenum telluride and black phosphorus, despite being prominent, exhibit air sensitivity, and their room temperature emissions can be significantly broadened by tens of meV. Here, a self-encapsulation strategy is developed to scalably synthesize robust 2D vdWs ErOCl with sub-meV narrow emissions at the telecom C-band. Diverse 2D rare earth materials are also grown via chemical vapor deposition (TmOCl, YbOCl, HoOCl, DyOCl, SmOCl, NdOCl, TbOCl, GdOCl, EuOCl, and PrOCl), demonstrating the strategy's generalizability. The as-grown ErOCl exhibits high crystalline quality and excellent ambientand thermal stability (300°C). Photoluminescence analysis reveals a series of narrow emissions across the visible to near-infrared spectrum. The ErOCl's emission at the telecom band is narrowest among 2D luminescent materials, and suitable for integrating with photonic chips. Temperature-dependent photoluminescence spectra facilitate the understanding of emission mechanisms, analyzed using a crystal field perturbation model. Moreover, these emissions can be tuned by external magnetic fields. This research not only pioneers a novel strategy for synthesizing 2D rare earth materials but also paves the way for innovative building blocks in the realm of on-chip optical communications.

Quantum integration of decay rates at second order in perturbation theory

Abstract We present the first quantum computation of a total decay rate in high-energy physics at second order in
perturbative quantum field theory. This work underscores the confluence of two recent cutting-edge advances.
On the one hand, the quantum integration algorithm Quantum Fourier Iterative Amplitude Estimation (QFIAE),
which efficiently decomposes the target function into its Fourier series through a quantum neural network before quantumly integrating the corresponding Fourier components. On the other hand, causal unitary in the
loop-tree duality (LTD), which exploits the causal properties of vacuum amplitudes in LTD to coherently generate all contributions with different numbers of final-state particles to a scattering or decay process, leading to
singularity-free integrands that are well suited for Fourier decomposition. We test the performance of the quantum algorithm with benchmark decay rates in a quantum simulator and in quantum hardware, and find accurate
theoretical predictions in both settings.

Influence of pedestal pressure on plasma response to resonant magnetic perturbation field

Influence of pedestal pressure on plasma response to resonant magnetic perturbation field

Revealing exchange bias in spin compensated systems for spintronics applications

Antiferromagnetic materials offer potential for spintronic applications due to their resilience to magnetic field perturbations and lack of stray fields. Achieving exchange bias in these materials is crucial for certain applications; however, discovering such materials remains challenging due to their compensated spin structure. The quest for antiferromagnetic materials with exchange bias became a reality through our experimental study and theoretical simulation on Sr2FeIrO6 and Sr2CoIrO6. This study also unveils the impact of ionic disorder and lattice distortion on magnetic properties. The presence of exchange bias in both materials, given their antiferromagnetic nature, is intriguing. This study opens up new avenues for achieving exchange bias in spin-compensated systems, offering potential for low power and ultra fast antiferromagnetic spintronic applications in future research endeavors.

Influences of δB contribution and parallel inertial term of energetic particles on MHD-kinetic hybrid simulations: a case study of the 1/1 internal kink mode

Abstract The magnetohydrodynamic-kinetic (MHD-kinetic) hybrid model (Park et al 1992 Phys. Fluids B 4 2033–7) has been widely applied in studying energetic particles (EPs) problems in fusion plasmas for past decades. The pressure-coupling scheme or the current-coupling scheme is adopted in this model. However, two noteworthy issues arise in the model application: firstly, the coupled term introduced in the pressure-coupling scheme, ( ∇ ⋅ P h ) ⊥ , is often simplified by ∇ ⋅ P h , which is equivalent to neglecting the parallel inertial term of EPs; secondly, besides the δ f contribution caused by changing in the EP distribution function, the magnetic field perturbation (the δ B contribution) generated during development of the instabilities should also be considered, but it is often ignored in existing hybrid simulations. In this paper, we derive the analytical formulations under these two coupling schemes and then numerically study the representative case of the linear stability of the m / n = 1 / 1 internal kink mode (IKM) (Fu et al 2006 Phys. Plasmas 13 052517) by using the CLT-K code. It is found that the approximated models can still yield reasonable results when EPs are isotopically distributed. But it fails completely in cases with anisotropic EP distributions. In addition, we further investigate the influence of EP’s orbit width on the stability of IKM and verify the equivalence between pressure-coupling scheme and the current-coupling scheme.

Enabling Electric Field Model of Microscopically Realistic Brain.

Modeling brain stimulation at the microscopic scale may reveal new paradigms for various stimulation modalities. We present the largest map to date of extracellular electric field distributions within a layer L2/L3 mouse primary visual cortex brain sample. This was enabled by the automated analysis of serial section electron microscopy images with improved handling of image defects, covering a volume of 250 × 140 × 90 μm³. The map was obtained by applying a uniform brain stimulation electric field at three different polarizations and accurately computing microscopic field perturbations using the boundary element fast multipole method. We used the map to identify the effect of microscopic field perturbations on the activation thresholds of individual neurons. Previous relevant studies modeled a macroscopically homogeneous cortical volume. Our result shows that the microscopic field perturbations - an 'electric field spatial noise' with a mean value of zero - only modestly influence the macroscopically predicted stimulation field strengths necessary for neuronal activation. The thresholds do not change by more than 10% on average. Under the stated limitations and assumptions of our method, this result essentially justifies the conventional theory of "invisible" neurons embedded in a macroscopic brain model for transcranial magnetic and transcranial electrical stimulation. However, our result is solely sample-specific and is only relevant to this relatively small sample with 396 neurons. It largely neglects the effect of the microcapillary network. Furthermore, we only considered the uniform impressed field and a single-pulse stimulation time course.

Quasinormal modes of regular black holes with sub-Planckian curvature and Minkowskian core

We investigate the perturbation of the scalar field as well as the electromagnetic field over a sort of regular black holes which are characterized by the sub-Planckian curvature and the Minkowskian core. Specifically, we compute the quasinormal modes (QNMs) by employing the pseudo-spectral method. The outburst of overtones is manifestly observed in the QNMs of these regular black holes, which can be attributed to the deviation of the Schwarzschild black hole by quantum effects of gravity. Furthermore, the QNMs under the perturbation of electromagnetic field exhibit smaller real and imaginary parts than those under scalar field perturbation. By comparing the QNMs of the regular black hole featured by Minkowskian core with those of Bardeen black hole featured by de Sitter core, we find they may be an effective tool to distinguish these BHs.

Topography‐dependent eikonal solver in tilted transverse isotropic media with anelliptical factorization

AbstractIncorporating anisotropy and complex topography is necessary to perform traveltime tomography in complex land environments while being a computational challenge when traveltimes are computed with finite‐difference eikonal solvers. Previous studies have taken this challenge by computing traveltimes in transverse isotropic media involving complex topography with a finite‐difference eikonal equation solver on a curvilinear grid. In this approach, the source singularity, which is a major issue in eikonal solvers, is managed with the elliptical multiplicative factorization method, where the total traveltime field is decomposed into an elliptical base traveltime map, which has a known analytical expression and an unknown perturbation field. However, the group velocity curve can deviate significantly from an ellipse in anellipitically anisotropic media. In this case, the elliptical base traveltime field differs significantly from the anelliptical counterpart, leading to potentially suboptimal traveltime solutions, even though it helps to mitigate the detrimental effects of the source singularity. To overcome this issue, we develop a more accurate topography‐dependent eikonal solver in transverse isotropic media that relies on anelliptical factorization. To achieve this, we first define the coordinate transform from the Cartesian to the curvilinear coordinate system, which provides the necessary framework to implement the topography‐dependent transverse isotropic finite‐difference eikonal solver with arbitrary source and receiver positioning. Then, we develop a semi‐analytical method for the computation of the topography‐dependent anelliptical base traveltime field. Finally, we efficiently solve the resulting quadratic elliptical equation using the fast sweeping method and a quartic anelliptical source term through fixed‐point iteration. We assess the computational efficiency, stability and accuracy of the new eikonal solver against the solver based on elliptical factorization using several transverse isotropic numerical examples. We conclude that this new solver provides a versatile and accurate forward engine for traveltime tomography in complex geological environments such as foothills and thrust belts. It can also be used in marine environments involving complex bathymetry when tomography is applied to redatumed data on the sea bottom.

Quasinormal modes and shadow of Schwarzschild black holes embedded in a Dehnen-type dark matter halo exhibiting a cloud of strings

In this paper we consider a static spherically symmetric black hole (BH) embedded in a Dehnen-(1, 4, 0)-type dark matter (DM) halo in the presence of a cloud string. We examine and present data on how the core density of the DM halo parameter and the cloud string parameter affect BH attributes such as quasinormal modes (QNMs) and shadow cast. To do this, we first look into the effective potential of perturbation equations for three types of perturbation fields with different spins: massless scalar field, electromagnetic field and gravitational field. Then, using the sixth-order Wentzel–Kramers–Brillouin approximation, we examine QNMs of the BH disturbed by the three fields and derive quasinormal frequencies. The changes in QNM versus the core density parameter and the cloud string parameter for three disturbances are explored. We also investigate how the core density and the cloud string parameter affect the photon sphere and shadow radius. Interestingly, the study shows that the influence of Dehnen-type DM and cloud strings increases both the photon sphere and the shadow radius. Finally, we employ observational data from Sgr A⋆ and M87⋆ to set limitations on the BH parameters.

Short-hair black holes and the strong cosmic censorship conjecture

The singularity problem has always been a key focus of physicists’ research. To address this issue, Penrose proposed the cosmic censorship conjecture, with the Strong Cosmic Censorship Conjecture (SCCC) being particularly crucial. However, verifying SCCC in different scenarios still faces many challenges. This paper, set against the background of short-hair black holes, explores whether they obey SCCC when subjected to scalar field perturbations. Using the WKB method, Prony method, Lyapunov exponent, and Weak Gravity Conjecture (WGC), the behavior of a short-hair black hole under different parameter conditions was systematically analyzed. Numerical results indicate that as the charge Q of the short-hair black hole approaches its extremal value, the SCCC is violated. However, as the order k of the metric equation and the angular quantum number ℓ increase, the violation of SCCC is delayed. These results suggest that the proximity of the black hole’s charge Q to its extremal value, along with the size of the angular quantum number ℓ and the order k, play key roles in exploring the physical properties of black holes and verifying SCCC. Finally, research using the WGC shows that when the charge-to-mass ratio in a scalar field meets certain conditions, short-hair black holes can still comply with the SCCC under extreme conditions. This study not only reveals the behavior of short-hair black holes in extreme situations but also offers a new perspective for further exploration of such black holes.

Effective dimensionality of space-time in f(R)-general relativity with quantum boundary terms included

I study an extended theory of General Relativity that incorporates normalized relativistic velocities, where the boundary terms in the varied f(R)-action are considered as a part of the physical system to be studied. Within this context, I investigate how the classical perturbations can be originated by quantum geometric perturbations, that alters the dynamics of the physical system without perturbations. To do it we use a modified nonlinear quantum algebra recently introduced. The quantum field perturbations of space-time also alter the geodesic equations that describe the dynamics of the relativistic velocities, the metric tensor and the Ricci tensor. But perhaps the most intriguing of this phenomena is that these space-time alterations change the effective number of space-time dimensions of the system with perturbations included N(z), in a such manner that N(z) can take an irrational value N(z=2)=8/(1+5)≃2.4721, when the nonlinear quantum perturbations of space-time are related to the relativistic velocities U¯μ. To illustrate the theory, we calculate exactly the cosmological parameter in an early inflationary universe.

Electromechanical flight stabilization system for CubeSat nanosatellites

The objective of the research was to design and simulate a stabilization system for attitude control of CubeSat nanosatellites in LEO orbit. The electronic system was inside the mechanical system, designed in Proteus. The mechanical system was designed in SolidWorks, then a CubeSat 3U CAD was downloaded for simulation and finally, all CAD designs were assembled. These data were used for the analysis of the spatial environmental perturbations of aerodynamic drag, gradient, gravity and magnetic field. Attitude representation was done by analyzing the Euler, Poisson and Quaternions equations. Then, a fuzzy logic control was created with two cases for automatic control. The analysis and virtual reality simulation revealed the correct attitude control on the CubeSat 3U nanosatellite, considering the perturbations of the space environment and a new 25° orientation of each axis.

Impacts of Thunderstorm-Generated Gravity Waves on the Ionosphere-Thermosphere Using TIEGCM-NG/MAGIC Simulations and Comparisons With GNSS TEC, ICON, and COSMIC-2 Observations.

We use the TIEGCM-NG nudged by MAGIC gravity waves to study the impacts of a severe thunderstorm system, with a hundred tornado touchdowns, on the ionospheric and thermospheric disturbances. The generated waves induce a distinct concentric ring pattern on GNSS TIDs with horizontal scales of 150-400km and phase speeds of 150-300m/s, which is well simulated by the model. The waves show substantial vertical evolution in period, initially dominated by 0.5hr at 200km, shifting to 0.25hr and with more higher-frequency waves appearing at higher altitudes (∼400km). The TADs reach amplitudes of 100m/s, 60m/s, 80K, and 10% in horizontal winds, vertical wind, temperature, and relative neutral density, respectively. Significantly perturbations in electron density cause dramatic changes in its nighttime structure around 200km and near the EIA crest. The concentric TIDs are also simulated in ion drifts and mapped from the Tornado region to the conjugate hemisphere likely due to neutral wind-induced electric field perturbations. The waves manage to impact the ionosphere at altitudes of ICON and COSMIC-2, which pass through the region of interest on a total of 8 separate orbits. In situ ion density observations from these spacecrafts reveal periodic fluctuations that frequently show good agreement with the TIEGCM-NG simulation. The O+ fraction observations from ICON indicate that the density fluctuations are the result of vertical transport of the ions in this region, which could result from either direct forcing by neutral winds or electrodynamic coupling.

Enabling Electric Field Model of Microscopically Realistic Brain.

This study is arguably the first attempt to model brain stimulation at the microscopic scale, enabled by automated analysis of modern scanning electron microscopy images of the brain. It concentrates on modeling microscopic perturbations of the extracellular electric field caused by the physical cell structure and is applicable to any type of brain stimulation. Post-processed cell CAD models (383, stl format), microcapillary CAD models (34, stl format), post-processed neuron morphologies (267, swc format), extracellular electric field and potential distributions at different polarizations (267x3, MATLAB format), *.ses projects files for biophysical modeling with Neuron software (267x2, Neuron format), and computed neuron activating thresholds at different conditions (267x8, Excel tables, without the sample polarization correction from Section 2.8) are made available online through BossDB , a volumetric open-source database for 3D and 4D neuroscience data.

The Sine–Gordon QFT in de Sitter spacetime

We consider the massless Sine–Gordon model in de Sitter spacetime, in the regime β2<4π and using the framework of perturbative algebraic quantum field theory. We show that a Fock space representation exists for the free massless field, but that the natural one-parameter family of vacuum-like states breaks the de Sitter boost symmetries. We prove convergence of the perturbative series for the S matrix in this representation and construct the interacting Haag–Kastler net of local algebras from the relative S matrices. We show that the net fulfills isotony, locality and de Sitter covariance (in the algebraic adiabatic limit), even though the states that we consider are not invariant. We furthermore prove convergence of the perturbative series for the interacting field and the vertex operators, and verify that the interacting equation of motion holds.

Finite basis topologies for multiloop high-multiplicity Feynman integrals

In this work, we systematically analyze Feynman integrals in the ‘t Hooft-Veltman scheme. We write an explicit reduction resulting from partial fractioning the high-multiplicity integrands to a finite basis of topologies at any given loop order. We find all of these finite basis topologies at two loops in four external dimensions. Their maximal cut and the leading singularity are expressed in terms of the Gram determinant and Baikov polynomial. By performing an integration-by-parts reduction without any cut constraint on a numerical probe for one of these topologies, we show that the computational complexity drops significantly compared to the conventional dimensional regularization scheme. Formally, our work implies an upper bound on the rigidity of special functions appearing in the iterated integral solutions at each loop order in perturbative quantum field theory. Phenomenologically, the integrand-level reduction we present will substantially simplify the task of providing high-precision predictions for future high-multiplicity collider observables. Published by the American Physical Society 2024

Topological protection of optical skyrmions through complex media

Optical Skyrmions have many important properties that make them ideal units for high-density data applications, including the ability to carry digital information through a discrete topological number and the independence of spatially varying polarization to other dimensions. More importantly, the topological nature of the optical Skyrmion heuristically suggests a strong degree of robustness to perturbations, which is crucial for reliably carrying information in noisy environments. However, the study of the topological robustness of optical Skyrmions is still in its infancy. Here, we quantify this robustness precisely by proving that the topological nature of the Skyrmion arises from its structure on the boundary and, by duality, is resilient to spatially varying perturbations provided they respect the relevant boundary conditions of the unperturbed Skyrmion. We then present experimental evidence validating this robustness in the context of paraxial Skyrmion beams against complex polarization aberrations. Our work provides a framework for handling various perturbations of Skyrmion fields and offers guarantees of robustness in a general sense. This, in turn, has implications for applications of the Skyrmion where their topological nature is exploited explicitly, and, in particular, provides an underpinning for the use of optical Skyrmions in communications and computing.