Monopole Mode Research Articles

Observation of monopole topological mode

Among the many far-reaching consequences of the potential existence of a magnetic monopole, it induces a topological zero mode in the Dirac equation, which was derived by Jackiw and Rebbi 48 years ago and has been elusive ever since. Here, we show that the monopole and multi-monopole solutions can be constructed in the band theory by gapping the three-dimensional Dirac points in hedgehog mass configurations. We then experimentally demonstrate such a monopole bound state in an optimized Dirac acoustic crystal structurally modulated in full solid angles. The monopole mode exhibits the optimal scaling behavior — whose modal spacing is inversely proportional to the cubic root of the modal volume. This work completes the kink-vortex-monopole zero-mode trilogy and paves the way for exploring higher-dimensional bulk-topological-defect correspondence.

Accelerating analysis of Boltzmann equations using Gaussian mixture models: Application to quantum Bose-Fermi mixtures

The Boltzmann equation is a powerful theoretical tool for modeling the collective dynamics of quantum many-body systems subject to external perturbations. Analysis of the equation gives access to linear response properties including collective modes and transport coefficients, but often proves intractable due to computational costs associated with multidimensional integrals describing collision processes. Here, we present a method to resolve this bottleneck, enabling the study of a broad class of many-body systems that appear in fundamental science contexts and technological applications. Specifically, we demonstrate that a Gaussian mixture model can accurately represent equilibrium distribution functions, thereby allowing efficient evaluation of collision integrals. Inspired by cold atom experiments, we apply this method to investigate the collective behavior of a quantum Bose-Fermi mixture of cold atoms in a cigar-shaped trap, a system that is particularly challenging to analyze. We focus on monopole and quadrupole collective modes above the Bose-Einstein transition temperature, and find a rich phenomenology that spans interference effects between bosonic and fermionic collective modes, dampening of these modes, and the emergence of hydrodynamics in various parameter regimes. These effects are readily verifiable experimentally. Published by the American Physical Society 2024

Superradiant instability of a charged regular black hole

We show that a charged, massive scalar field in the vicinity of an electrically charged Ayón-Beato–García (ABG) regular black hole has a spectrum of quasibound states that (in a certain parameter regime) grow exponentially with time, due to black hole superradiance. Superradiant quasibound states are made possible by the enhancement of the electrostatic potential at the horizon in nonlinear electrodynamics; in contrast, the Reissner-Nordström black hole does not appear to possess such superradiant quasibound states. Here we compute the spectrum for a range of multipoles ℓ across the parameter space, and we find the fastest growth rate in the monopole mode. We find that a regular black hole with a small charge can still trigger a significant superradiant instability if the charge-to-mass ratio of the field is compensatingly large. We estimate the amount of black hole mass that can be deposited in the scalar field, finding an upper bound of circa 20% in the extreme charge scenario. Finally, we consider the stationary bound states at the superradiant threshold, and we conjecture that, due to this instability, the ABG black hole will evolve toward a configuration with charged scalar hair. Published by the American Physical Society 2024

Enhanced wave absorption due to local flexibility on wide beams using mass-spring-damper scatterers

It is known that total absorption of flexural waves in a thin beam is possible through the use of monopole-dipole scatterers. In this study, we introduce a pair of identical monopole scatterers for near-total absorption of flexural waves in a thin and wide beam. Despite the two scatterers being both of the monopole type, the resonant modes of the scatterer pair exhibit monopole and dipole properties. By selecting the proper width for the beam, the two resonant modes degenerate, which leads to the total absorption. Although the beam is considerably wide, the frequency range of interest remains below the cut-on frequency of the n = 1 propagating mode, ensuring one-dimensional flexural wave propagation. Further simulations and theoretical analysis revealed that the degeneracy of the monopole and dipole modes results from their interaction with a higher-order localized flexural mode. The simulation results demonstrate absorption exceeding 99%, complemented by experimental data showing approximately 90% absorption.

Differing roles of North Atlantic oceanic and atmospheric transports in the winter Eurasian Arctic sea-ice interannual-to-decadal variability

In recent decades, winter Arctic sea-ice concentration (SIC) has experienced a most prominent decline over Barents-Kara Seas (BKS). However, what regulates the time scale and spatial structure of the SIC variability over the Eurasian Arctic is unclear. Here, we find that the SIC variability over the Eurasian Arctic exhibits two major modes: decadal dipole mode with antiphase variation between the BKS and East Greenland (EG), and interannual monopole mode with in-phase variation between the BKS and EG. This decadal mode mainly results from interdecadal changes in ocean heat transports (OHTs) through Barents Sea Opening (BSO) and EG, lagging the Atlantic Multidecadal Oscillation by 7–16 years. The positive SIC dipole mode with a decrease over the BKS and an increase over the EG is also tied to the negative Arctic Oscillation comprised of Ural blocking and the negative North Atlantic Oscillation (NAO). However, the SIC loss of the interannual monopole mode mainly stems from the positive Arctic dipole comprised of Ural blocking and positive NAO through interannual changes in the BSO OHT and atmospheric moisture or heat transport. We further highlight that interannual atmospheric transports and BSO OHT associated with the Arctic dipole contribute to ~66% and ~34% of the interannual variability of the Eurasian Arctic SIC during 1960-2017, respectively. On decadal timescales, the relative contributions of atmospheric transports associated with Arctic Oscillation and OHT to the Eurasian Arctic SIC variability are ~19% and ~81%, respectively. Especially, the contribution of decadal atmospheric transports is significantly intensified during 2000–2017.

A high‐integration dual‐resonance element with independent frequency tuning for wideband reflectarrays

AbstractIn this letter, a novel design methodology of dual‐resonance elements for wideband reflectarrays is proposed for the first time. The alluring merits of this design lie in the compact common‐via dual‐resonance element with weak inner coupling and independent frequency tuning. To improve compactness, a traditional dipole is terminated by a metallic via connected to the ground plane. The element operates in monopole mode, decreasing the size by half. To realize a high‐integration dual‐resonance element, two monopoles operating at different frequencies are adopted to construct an asymmetric common‐via element, with an equivalent size to the traditional dipole resonating at merely one frequency. The first‐ever proposed element embodies superiorities of compactness, independent frequency tuning, and low profile. The proof‐of‐concept is validated by a fabricated reflectarray. The elaborately designed element with a compact size of 0.42 λ × 0.105 λ × 0.0737 λ exhibits an extended phase range of 484° at 14 GHz. The measured 3‐dB gain bandwidth is 36% (12.5–18 GHz) with a maximum gain of 26.9 dBi. The design strategy is capable of integrating more resonant structures in a compact area, rendering it suitable for broadband reflectarrays.

Multipole Excitation of Localized Plasmon Resonance in Asymmetrically Coated Core–Shell Nanoparticles Using Optical Vortices

AbstractPlasmonic interactions between an asymmetrically coated core–shell (ACCS) nanoparticle and an optical vortex produce a novel engagement of the spin angular momentum (SAM) and the orbital angular momentum (OAM) of the input. Simulations based on a discrete dipole approximation (DDA) indicate that the SAM and the OAM of the incident beam determine the modal order of resonance, correctly identifying the peak wavelength, and both the direction and magnitude of optical torque exerted upon the excited, localized plasmon resonance in the ACCS particle. These simulations also indicate higher‐order resonances, including hexapole and octupole modes, and a zero‐order resonance (expressible as a monopole mode), can be excited by judicious selection of the SAM and OAM. A detailed symmetry analysis shows how the multipoles associated with eigenmode excitations connect to the radiation multipoles at the heart of the multipole expansion. It is also shown how additional, distorted resonance modes due to the asymmetricity of the structure are also exhibited. These specific plasmonic characteristics, which cannot be realized by plane wave excitation, become possible through the ACCS asymmetry engaging with the distinct optical vortex nature of the excitation.

The greybody factor for the monopole and odd-parity modes of the Proca field in the Schwarzschild black hole spacetimes

The greybody factor is one of the famous results of the black hole perturbation theory, which describes the transmission probability of a particle radiated by a black hole into spatial infinity. In this work, we separated the angular parts of the equations of motion and derived the radial equations for the Proca field in the Schwarzschild black hole spacetime. The radial equations for the monopole and odd-parity modes are fully decoupled in the Schrödinger-like form. We study the greybody factor by determining the rigorous bound.

Design of Singly Fed Dual-Band Antenna With a Large Frequency Ratio by Introducing a Monopole Mode to Yagi–Uda Antenna

Design of Singly Fed Dual-Band Antenna With a Large Frequency Ratio by Introducing a Monopole Mode to Yagi–Uda Antenna

Dominant modes and mechanisms of the interannual variability of atmospheric water vapor content during winter over Central Asia

Atmospheric water vapor content (WVC)—a key component of the water cycle—plays a crucial role as an indicator of precipitation changes and directly influences precipitation in the arid areas of Central Asia. These areas are extremely sensitive to global climate change because of their dry climates and fragile water resource systems, especially during winter. This study analyzes the main interannual variation patterns of the atmospheric WVC during winter over Central Asia and reveals the possible physical mechanism behind the changes in the dominant modes (EOF1 and EOF2) of water vapor. The results show that EOF1 (49.4%)—responsible for the interannual variation of the winter atmospheric WVC in Central Asia—has a uniform monopole mode, while EOF2 (23.7%) shows a reverse north–south dipole distribution (with the boundary being at approximately 44° N). The negative geopotential height anomaly over the high latitudes of Europe and the positive geopotential height anomaly over Central Asia are the major impact factors of EOF1, whereas Central Asia has a prevalence of westerly airflow during winter. By influencing the geopotential height anomaly in Central Asia, the winter Niño 3.4 index intensifies the convergence of Atlantic Ocean moisture with tropical Indian Ocean moisture and their eastward transport. In contrast, EOF2 is mainly affected by the positive geopotential height anomaly over the high latitudes of Europe and the negative geopotential height anomaly over the middle latitudes of this region. In particular, the negative anomaly center of the geopotential height on the eastern side of Central Asia extends westward into Central Asia, resulting in reverse moisture transport by westerly and easterly airflows in the southern and northern parts of Central Asia, respectively. This anomaly is correlated with the formation of anomalous cyclonic circulation over North Africa and Europe because of the negative phase of the Arctic Oscillation, leading to prevailing southerly winds in the south of Central Asia, which correspond to abnormal vertical upward movement; however, the situation in the northern part of Central Asia is the opposite. Therefore, the distribution of winter precipitation in Central Asia shows the following pattern: more in the south and less in the north. This study provides scientific and technological support for the formation of research mechanisms and the prediction of winter precipitation in Central Asia.

A shared aperture antenna with reconfigurable pattern by common and differential modes

AbstractIn this letter, a compact pattern‐reconfigurable (PR) antenna for indoor communication is proposed, which can provide one conical, one broadside, and two tilted patterns. The proposed antenna comprises a shared radiation patch with two highly isolated ports and a reconfigurable feeding network. By activating each port independently, a dipole mode with broadside pattern and a monopole mode with conical pattern are acquired, respectively. Meanwhile, inspired by the theory of common and differential modes, two tilted patterns toward and are realized by combining dipole and monopole modes. As a result, four‐type reconfigurable patterns can be obtained. To realize reconfigurability, a functional reconfigurable feeding network is designed with innovation. The proposed antenna is fabricated and measured. The measured overlapped −10 dB impedance bandwidth is 3.28–3.71 GHz (12.3%), and the peak radiation efficiency is superior to 82.7%. The experimental results indicate that the proposed PR antenna has a wide bandwidth and stable radiation patterns, which exhibits attractive potential for fifth‐generation indoor communication in sub‐6 GHz.

Study on the Interference of the HVDC Transmission Grounding Electrode to the Pipeline Cathodic Protection System.

Oil and gas are still largely transported by long-distance pipelines. In this study, we aimed to examine the impact of the high-voltage DC transmission grounding electrode on long-distance pipelines' cathodic protection system nearby. The writer built the interference model of the DC transmission grounding electrode on the pipeline using COMSOL Multiphysics based on the parameters of the actual project and considering the cathodic protection system within and then tested the model using experimental data. By simulating and calculating the model under different conditions of grounding electrode inlet current, grounding electrode-pipe distance, soil conductivity, and pipeline coating surface resistance, we obtained the current density distribution in the pipeline and the cathodic protection potential distribution law. The outcome presents a visual representation of the corrosion occurring in adjacent pipes as a result of DC grounding electrodes operating in monopole mode.

A Pattern-Reconfigurable Cylindrical Dielectric Resonator Antenna With Three Switchable Radiation Patterns

A pattern-reconfigurable antenna with three switchable radiation patterns is investigated. It consists of a three-layer cylindrical dielectric resonator antenna (DRA) and a parasitic monopole antenna. Its feed network comprises a Y-shaped feedline, a square ring slot, and seven diodes. For the first time, by controlling the operation states of the diodes, the radiation pattern of the antenna can be switched between the omnidirectional, broadside, and unilateral modes. The omnidirectional pattern is obtained by virtue of the parasitic monopole, whereas the broadside pattern can be obtained when the DRA and radiation mode of the feeding ring slot are excited. If the parasitic monopole, DRA, and radiation mode of the slot are all excited, their radiation fields can be superimposed to give a unilateral radiation pattern. The radiated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -field is vertically polarized for all of the three radiation modes. A prototype working in 2.4-GHz ISM band was fabricated and tested to verify the idea, and reasonable agreement between the measured and simulated results is observed.

Quantum Monte Carlo-based density functional for one-dimensional Bose-Bose mixtures

We propose and benchmark a Gross-Pitaevskii-like equation for two-component Bose mixtures with competing interactions in 1D. Our approach follows the density-functional theory with the energy functional based on the exact Quantum Monte Carlo (QMC) simulations. Our model covers, but goes beyond, the popular approach with the Lee-Huang-Yang corrections. We first benchmark our approach against available QMC data in all interaction regimes and then study dynamical properties, inaccessible by ab initio many-body simulations. Our analysis includes a study of monopole modes and reveals the presence of anomalous dark solitons.

Properties of scalar wave emission in a scalar-tensor theory with kinetic screening

We study numerically the scalar wave emission by a non-spherical oscillation of neutron stars in a scalar-tensor theory of gravity with kinetic screening, considering both the monopole and quadrupole mode emission. In agreement with previous results in the literature, we find that the monopole is always suppressed by the screening effect, regardless of the size of the screening radius, $r_{\rm sc}$. For the quadrupole mode, however, our analysis shows that the suppression only occurs for screening radius larger than the wavelength of scalar waves, $\lambda_{\rm wave}$, but not for $r_{\rm sc} < \lambda_{\rm wave}$. This demonstrates that to fully understand the nature of this theory, it is necessary to study other more complex systems, such as neutron star binaries, considering a wide range of $r_{\rm sc}$ values.

Wideband Pattern-Reconfigurable Antenna With Switchable Monopole and Vivaldi Modes

A novel design for radiation pattern-reconfigurable antenna is described in this letter. The design is based on a wideband Vivaldi antenna structure. Two different radiation patterns are achieved by switching the feeding paths to obtain two antennas operation modes, monopole mode and Vivaldi mode. The reconfigurable antenna can adjust the radiation patterns by controlling the bias voltage of pin diodes. Therefore, by combining the two radiation patterns, a broad coverage of reconfigurable pattern is generated. In addition, the pattern reconfigurable antenna can operate at a wide frequency band from 2.7 to 12 GHz. Details of the simulated and experimented results for the pattern-reconfigurable antenna are shown.

Isoscalar monopole strength in 100Mo: an indicator for static triaxial deformation in the ground state* *Supported by the National Natural Science Foundation of China (12075068, 11705038), the Fundamental Research Funds for the Central Universities (HIT.BRET.2021003) and the UK STFC (ST/V001108/1)

We perform deformation constraint symmetry-unrestricted three-dimensional time-dependent density functional theory (TDDFT) calculations for the isoscalar monopole (ISM) mode in 100Mo. Monopole moments are obtained as a function of time using time propagating states based on different deformations. A Fourier transform is then performed on the obtained response functions. The resulting ISM strength functions are compared with experimental data. For the static potential-energy-surface (PES) calculations, the results using the SkM* and UNEDF1 energy-density functionals (EDFs) show spherical ground states and considerable softness in the triaxial deformation. The PES obtained with the SLy4 EDF shows static triaxial deformation. The TDDFT results based on different deformations show that a quadrupole deformation (characterized by ) value of 0.25–0.30 gives a two-peak structure of the strength functions. Increasing triaxial deformation (characterized by γ) from 0 to 30 results in the occurrence of an additional peak between the two, making the general shape of the strength functions closer to that of the data. Our microscopic TDDFT analyses suggest that 100Mo is triaxially deformed in the ground state. The calculated isoscalar and strength functions show peaks at lower energies. The coupling of these two modes with the ISM mode is the reason for the three-peak/plateau structure in the strengths of 100Mo.

Self-Decoupled MIMO Antenna Realized by Adjusting the Feeding Positions

This paper proposes a novel decoupling technique achieved by adjusting the position of feeding probes of antennas. Two inherent radiation modes (patch mode and monopole mode), with different patterns and polarizations, are simultaneously excited by the same feeding probe. High isolation is realized based on manipulating the relationship of two-mode couplings by moving the feeding positions. Since the two radiation modes are generated by the same antenna element, the proposed MIMO antenna features a simple structure and compact size. For verification, a two-element array with center-to-center spacing of 0.404 λ0 (λ0 is the wavelength in the air) is prototyped and characterized. Simulation and experimental results show that the proposed novel technique can offer higher port isolation (&gt;18.1 dB), increased efficiency (&gt;70%), and a lower envelope correlation coefficient (ECC &lt; 0.1) in the operating frequency band (11.61–12.49 GHz).

A High-Efficiency Microstrip Antenna Pair with Similar Pi-Shaped Decoupling Structure for 3.5 GHz 5G Ultrathin Smartphones

In this paper, a low profile and high-efficiency decoupling antenna pair for multiunit smartphones is proposed using a similar π-shaped feed structure that can excite the dipole radiation mode of microstrip antenna. Ordinarily, symmetrical single-port T-shaped microstrip antennas can only excite monopole modes of bilateral radiation. This paper changes the vertical feeding microstrip structure into two oblique, similar π-shaped feeding structures. This oblique feeding structure can excite the dipole mode of unilateral radiation of the microstrip antenna. Using this method, the antenna design can be simplified, and the low-coupling independent radiation on both sides of the microstrip antenna can be freely controlled without the need for additional structures. Considering the ultra-thin characteristics of 5G smartphone devices, the parameters of the antenna are further optimized: the optimized antenna profile is only 3.7 mm. The measured results show that the 2 × 2 microstrip antenna pairs can effectively cover the 3.5 GHz band (3.4–3.6 GHz), with a coupling that varies from −16.14 dB to −11.01 dB and an efficiency that varies from 80% to 94.1%. The 8 × 8 MIMO smartphone antenna results show that the coupling varies from −20.1 dB to −12.17 dB, the efficiency varies from 79.72% to 93.7%, and the envelope correlation coefficient (ECC) is lower than 0.05. The microstrip antenna decoupling pair with a similar π-shaped feed structure proposed in this paper has high efficiency and low-profile characteristics have important application value in the decoupling design of 3.5 GHz 5G ultra-thin smartphone antennas.

Compact 8 × 8 MIMO Antenna Design for 5G Terminals

In this paper, a compact 8 × 8 MIMO antenna design for 5G terminals is proposed. The 8 × 8 MIMO antenna consists of two quad-element antenna pairs, each of which includes two symmetrical T-shaped monopole mode elements and two symmetrical edge-coupled fed dipole mode elements. The size of the quad-element antenna is 38 × 7 × 0.8 mm3. T-shaped monopoles are decoupled by parasitic elements, and dipoles are decoupled by grounding strips. Meanwhile, both T-shaped monopoles and dipoles are also decoupled by the orthogonal mode. The results show that the operating frequency band of each antenna element meets the requirement of 3.4–3.6 GHz, the reflection coefficient is less than −6 dB, and the isolation between any antenna element is more than 10 dB. The antenna radiation efficiency is over 50% in the entire operating frequency band for the 8 × 8 MIMO system.