Article
Geosciences, Multidisciplinary
David Gubbins, Yi Jiang, Simon E. Williams, Keke Zhang
Summary: Mars has a magnetic field originating in its strongly magnetized crust. The decomposition of simple candidate magnetic structures helps separate the responsible parts for anomalies from those that are invisible. A uniform magnetic layer does not produce anomalies, while secondary magnetization may reflect the primordial dynamo field. A magnetized crust with variable thickness can produce large anomalies, but they are absent if the magnetic layer lies deeper than the crater floor.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Computer Science, Software Engineering
Quoc T. Le Gia, Ming Li, Yu Guang Wang
Summary: Vector spherical harmonics on the unit sphere of R-3 have broad applications in geophysics, quantum mechanics, and astrophysics. Fast algorithms (FaVeST) for vector spherical harmonic transforms are developed in this article, with numerical examples illustrating their accuracy, efficiency, and stability. The forward FaVeST evaluates Fourier coefficients with computational cost proportional to N log root N, while the adjoint FaVeST evaluates a linear combination of vector spherical harmonics with cost proportional to M log root M.
ACM TRANSACTIONS ON MATHEMATICAL SOFTWARE
(2021)
Article
Optics
F. Camas-Aquino, P. A. Quinto-Su, R. Jauregui
Summary: In this study, we theoretically identify the spherical vector wave (SVW) fields that can be approximately generated from incident cylindrical beams using a 4 pi optical array. A comparison is made between the near electromagnetic field of ideal SVW and that of the spherical spots generated by cylindrical incident laser beams with selected angular spectra and a finite lens aperture of the 4 pi system, using fidelity as a figure of merit. Finally, some challenges in the implementation of SVW are briefly discussed.
Article
Acoustics
Deepika Kumari, Lalan Kumar
Summary: This paper proposes the use of a spherical sector microphone array for beamforming, and designs a new beamformer with maximum directivity and white noise gain for the spherical sector microphone array. The performance of the proposed method is validated through experiments and compared with other beamforming techniques, showing that the beamformer based on the spherical sector microphone array provides relatively better results.
Article
Engineering, Electrical & Electronic
Josef Knapp, Thomas F. Eibert
Summary: Explicit formulas are presented in this article for converting spherical wave expansions with vector basis functions and scalar expansion coefficients into spherical wave expansions with scalar basis functions and vector expansion coefficients, and vice versa. These formulas are given in terms of Wigner-3-j-symbols and derived through spherical harmonics expansions. The redundancy in the expansions with vector coefficients is utilized to find compact expansions with a minimum order. The correctness of all the expansions is verified using a computer code, showing a high level of agreement between the near and far fields.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2023)
Article
Acoustics
Adrian Herzog, Emanuel A. P. Habets
Summary: This paper investigates different distance estimation methods using compact spherical microphone arrays. Two existing methods are discussed and a new method utilizing the recurrence relations of spherical Hankel functions is proposed. In addition, a frequency averaging method for broad-band distance estimation is studied. The effectiveness of the proposed methods is evaluated through simulations and recordings.
Article
Mathematics, Applied
Jean-Baptiste Bellet, Jean -Pierre Croisille
Summary: The Cubed Sphere grid is an important tool for approximating functions or data on the sphere. In this study, we propose an approximation framework based on least squares and a specifically chosen subspace of spherical harmonics. Our main claim is that for the equiangular Cubed Sphere grid with a step size of pi/(2N), the relevant subspace of spherical harmonics consists of functions with a degree less than 2N. This choice ensures a well-posed and well-conditioned approximation problem, which is supported by theoretical and numerical results.
JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS
(2023)
Article
Materials Science, Multidisciplinary
Jeong-Young Ji, Boyd F. Edwards, J. Andrew Spencer, Eric D. Held
Summary: This study demonstrates that the energy, force, and torque between two spherically symmetric multipole density distributions are equivalent to those between two point multipoles, extending recent work on interactions between uniformly magnetized dipole spheres to interactions between spherically-symmetric multipole spheres. By expanding the inverse-distance potential in terms of harmonic tensors and utilizing their properties, the potential energy, force, and torque for two arbitrary source distributions can be expressed in a series of point-multipole interactions.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2021)
Article
Computer Science, Interdisciplinary Applications
R. D. M. Garcia
Summary: A stable spherical harmonics (P-N) method is proposed for solving multi-region sphere problems by iterating locally and using an effective post-processing step. The method can achieve very accurate results for problems with strong flux gradients without relying on space and angle discretizations.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Computer Science, Artificial Intelligence
Tian Zhang, Yongquan Zhou, Guo Zhou, Wu Deng, Qifang Luo
Summary: This paper proposes a Discrete Mayfly Algorithm (DMA) for solving spherical asymmetric traveling salesman problem. The algorithm proves to be superior to others, especially in high-dimensional cases, through experimentation and comparison with other metaheuristic algorithms.
EXPERT SYSTEMS WITH APPLICATIONS
(2023)
Article
Computer Science, Artificial Intelligence
Priyadarshini Dwivedi, Gyanajyoti Routray, Rajesh M. Hegde
Summary: This letter proposes a new learning-based range estimation technique using spherical harmonics intensity (SH-INT) coefficients for near-field acoustic range estimation. The SH-INT coefficients are well distinguished at high frequencies for accurate range estimation. A convolutional neural network (CNN) model is adopted to map the SH-INT coefficients with the range classes. Experimental results validate the effectiveness of the proposed method.
PATTERN RECOGNITION LETTERS
(2023)
Article
Computer Science, Software Engineering
Hanggao Xin, Zhiqian Zhou, Di An, Ling-Qi Yan, Kun Xu, Shi-Min Hu, Shing-Tung Yau
Summary: Spherical harmonics (SH) are a powerful tool for rendering, but computation of triple and multiple products can be a bottleneck. This paper proposes a fast and accurate method for computing spherical harmonics triple and multiple products, demonstrating efficiency in rendering applications.
ACM TRANSACTIONS ON GRAPHICS
(2021)
Article
Multidisciplinary Sciences
Valentin Lychagin
Summary: This work investigates the algebraic and differential SO(3)-invariants of spherical harmonics, and explores the fields of rational algebraic and rational differential invariants in describing the regular SO(3)-orbits of spherical harmonics.
Article
Geosciences, Multidisciplinary
Tristan Weber, Kimberly Moore, John Connerney, Jared Espley, Gina DiBraccio, Norberto Romanelli
Summary: In this study, we analyzed the internal magnetic dynamo of Ganymede using data from the Juno and Galileo spacecraft. Ganymede, the only known moon with a strong internal magnetic field, is of unique interest in understanding planetary magnetospheres. Our findings suggest that a dipole approximation is more accurate than a quadrupole fit. The estimated magnetic moments can be used as a baseline for interpreting future spacecraft data and for numerical modeling of Ganymede's magnetosphere.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Computer Science, Information Systems
Zhiming Zhang, Shyi-Ming Chen
Summary: A new group decision making method based on multiplicative consistency-and-consensus preference analysis for incomplete q-rung orthopair fuzzy preference relations is proposed in this paper. Novel concepts and optimization models are introduced to ascertain unknown values and obtain acceptable multiplicative consistency for q-rung orthopair fuzzy preference relations. The proposed method shows practicality and outperforms existing group decision making methods in incomplete q-rung orthopair fuzzy environments.
INFORMATION SCIENCES
(2021)
Article
Physics, Multidisciplinary
Rikuto Oiwa, Hiroaki Kusunose
Summary: This paper proposes a systematic method for identifying essential parameters in linear and nonlinear response tensors, and provides an application example in the ferroelectric SnTe monolayer for the nonlinear Hall effect.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Review
Chemistry, Multidisciplinary
Jun-ichiro Kishine, Hiroaki Kusunose, Hiroshi M. Yamamoto
Summary: This article discusses the order parameter for molecular and crystal chirality and the various effects associated with it, such as spin selectivity and chiral resolution.
ISRAEL JOURNAL OF CHEMISTRY
(2022)
Article
Physics, Condensed Matter
Hiroaki Kusunose, Satoru Hayami
Summary: The generalization of atomic-scale multipoles is discussed in this article, introducing augmented multipoles defined in hybrid orbitals or site/bond clusters to express any electronic degrees of freedom according to the crystallographic point group. These multipole descriptors are useful for describing cross-correlated phenomena, band-structure deformation, and the generation of effective spin-orbit coupling due to antiferromagnetic ordering in a systematic and comprehensive manner. A symmetry-adapted multipole basis set like this could be promising for materials design and informatics.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Physics, Multidisciplinary
Satoru Hayami, Rikuto Oiwa, Hiroaki Kusunose
Summary: This study investigates the theoretical consequences of the electric ferro-axial moment, revealing its role in functional materials and providing new possibilities for future material development.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Article
Physics, Multidisciplinary
Rikuto Oiwa, Hiroaki Kusunose
Summary: This paper investigates the microscopic origin of chirality, possible electric-field induced static rotational lattice deformation, and rotation-field induced electric polarization. By constructing a realistic tight-binding model for the elemental Te crystal, the authors identify the microscopic origin of chirality and essential couplings among polar and axial vectors. Based on this model, they quantitatively elucidate that an interband process driven by nearest-neighbor spin-dependent imaginary hopping is the key factor in electric-field induced rotation. These couplings and responses are characteristic and common to any chiral material, suggesting a possible experimental approach for achieving absolute enantioselection.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Hirokazu Tsunetsugu, Hiroaki Kusunose
Summary: We have developed a microscopic theory on the energy dispersion of phonons in chiral crystals and have shown that the splitting of sound velocity of acoustic phonons with opposite crystal angular momenta must be zero. We have also derived a formula for the k-linear splitting of chiral optical phonons. In addition, we have found that certain types of antisymmetric interactions of atomic displacements are not allowed in microscopic Hamiltonians for chiral phonons.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2023)
Article
Physics, Multidisciplinary
Satoru Hayami, Hiroaki Kusunose
Summary: We theoretically investigate the antiferromagnetic structure in a hexagonal zigzag-chain compound Ce3TiBi5. We find a partial magnetic order and show that magnetic frustration arising from competing exchange interactions plays an important role in realizing this order. The magnetic toroidal dipole moment is found to be responsible for the observed behaviors.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Article
Chemistry, Medicinal
Kyosuke Ishito, Huiling Mao, Kaya Kobayashi, Yusuke Kousaka, Yoshihiko Togawa, Hiroaki Kusunose, Jun-ichiro Kishine, Takuya Satoh
Summary: Recently, the study of chiral phonons, which possess angular and pseudoangular momenta, has gained significant attention. The detection of peak splitting in circularly polarized Raman spectroscopy provides evidence for the presence of chiral phonons in chiral crystals. This study presents observation of chiral phonons in a unary crystal, Te, and confirms the conservation law of pseudoangular momentum in Raman scattering, which determines the handedness of chiral crystals. The true chirality of the phonons is evaluated using a measure similar to an electric toroidal monopole.
Article
Materials Science, Multidisciplinary
Hiroaki Kusunose, Rikuto Oiwa, Satoru Hayami
Summary: We have developed a symmetry-adapted modeling procedure for molecules and crystals, which can systematically generate the complete symmetry-adapted multipole basis set to describe electronic degrees of freedom. By expressing the Hamiltonian in terms of linear combinations of these bases, we can determine the model parameters to reproduce electronic structures. This method provides a fundamental basis for symmetry-based analysis in materials science and complements the standard Wannier tight-binding modeling.
Article
Materials Science, Multidisciplinary
Yuki Yanagi, Hiroaki Kusunose, Takuya Nomoto, Ryotaro Arita, Michi-To Suzuki
Summary: We propose a systematic method for generating symmetry-adapted magnetic structures to analyze complex modulated magnetic structures. The method extends the generation scheme based on multipole expansion, which was previously only applicable for k = 0. By mapping the multipole magnetic alignments to the periodic crystal structure with the phase factor for wave vector k, symmetry-adapted magnetic structures with ordering vector k can be obtained. This method provides all magnetic bases compatible with irreducible representations under a k group for a given crystal structure and wave vector k.
Article
Materials Science, Multidisciplinary
Satoru Hayami, Megumi Yatsushiro, Hiroaki Kusunose
Summary: This article theoretically investigates the nonlinear spin Hall effect in PT-symmetric antiferromagnetic metals and elucidates its microscopic origin and conditions for enhancement through analyzing a microscopic model. A table with useful correspondences is also provided.
Article
Materials Science, Multidisciplinary
Megumi Yatsushiro, Rikuto Oiwa, Hiroaki Kusunose, Satoru Hayami
Summary: The study investigates the nonlinear transport phenomena in PT symmetric collinear antiferromagnetic metals with a magnetic toroidal moment. By analyzing the second-order nonlinear conductivity, it is found that the effective coupling between the magnetic toroidal moment and the antisymmetric spin-orbit interaction is a crucial source of the nonlinear conductivity. Moreover, the nonreciprocal longitudinal current and nonlinear transverse current are significantly enhanced just below the transition temperature of the antiferromagnetic ordering.
Article
Materials Science, Multidisciplinary
Megumi Yatsushiro, Hiroaki Kusunose, Satoru Hayami
Summary: The paper examines the mutual interplay between electronic degrees of freedom in solids, particularly focusing on the classification and role of multipoles in various responses, which provides important insights for the discovery and design of functional multiferroic materials.
Article
Materials Science, Multidisciplinary
Satoru Hayami, Hiroaki Kusunose
Summary: This study investigates the electronic states caused by an emergent odd-parity magnetic quadrupole, showing that spontaneous ordering leads to an antisymmetric spin-orbital polarization in momentum space and a spin-orbital-momentum locking. It is demonstrated that the orbital or sublattice degree of freedom is essential for this locking to occur, and modulation of electronic band structures is observed in the presence of magnetic quadrupole ordering. The spin-orbital-momentum locking is related to various cross-correlated phenomena, indicating the importance of these odd-parity multipoles in multiferroic and nonreciprocal optical effects.
Article
Materials Science, Multidisciplinary
Satoru Hayami, Hiroaki Kusunose
Summary: The study examines the emergent anomalous Hall effect in collinear antiferromagnets, which does not require net magnetization or external magnetic field. It is shown that this effect is essentially caused by the ferroic ordering of anisotropic magnetic dipoles, providing an effective coupling between ordered magnetic moments and electronic motion. The behavior of the effect in the orthorhombic lattice system is analyzed, with significant enhancement observed due to the coupling between the anisotropic magnetic dipoles and the spin-orbit interaction.
