Resonance Poles Research Articles

Adaptive Digital Notch Filter for Enhanced Stability in Grid-Connected Inverter Systems

Grid-connected inverters with LCL filters are crucial components in renewable energy systems, but they face stability challenges due to varying grid impedances and resonant frequencies. This paper presents a novel adaptive digital notch filter designed to enhance the stability of such systems across a wide range of operating conditions. The proposed filter employs a three-step adaptive mechanism: resonance detection, determination of resonant frequency change direction, and dynamic notch frequency adjustment. A comprehensive stability analysis in the z-plane reveals the behavior of the resonant pole under different scenarios, informing the filter's design. The adaptive filter's performance was evaluated through simulations. Results demonstrate significant improvements in system stability compared to conventional fixed-frequency notch filters. In scenarios where the resonant frequency was lower than the initial notch frequency, the adaptive filter prevented current divergence and reduced the line current harmonic magnitude at the resonant frequency by up to 75%. In scenarios where the resonant frequency was higher than the notch frequency, the proposed filter successfully suppressed current oscillations, maintaining stability where conventional filters failed. The adaptive mechanism responded to instability within 2 ms, adjusting the notch frequency to optimal levels within 10 ms. This research contributes to the advancement of grid-connected power electronics, offering a robust solution that can enhance the reliability and efficiency of renewable energy integration by up to 30% under varying grid conditions.

Formulae for enhanced cross sections induced by unusual resonant poles

Abstract We extend a traditional effective range theory, which is possible to explain a low-energy scattering phenomena by a real potential in neutron plus target systems, to describe the scattering by a complex potential. The extension is achieved based on an analytic Jost function, and we construct analytic formulae to describe enhanced cross sections in a neutron scattering, which is originated from unusual resonant states, such as an anti-resonant state and an unstable bound state, appearing around zero momentum. The formulae are checked by comparing them with numerical calculations, and we have found that the analytic formulae are quite valid in reproducing the cross sections for the shape elastic scattering and the compound nucleus formation in the low-energy neutron scattering.

Toward a unified description of hadron scattering at all energies

The construction of general amplitudes satisfying symmetries and S-matrix constraints has been the primary tool in studying the spectrum of hadrons for over half a century. In this work, we present a new parametrization, which can fulfill many expectations of S-matrix and Regge theory and connects the essential physics of hadron scattering in the resonance region and in asymptotic limits. In this construction, dynamical information is entirely contained in Regge trajectories that generalize resonance poles in the complex energy plane to moving poles in the angular momentum plane. We highlight the salient features of the model, compare with existing literature on dispersive and dual amplitudes, and benchmark the formalism with an initial numerical application to the ρ and σ/f0(500) mesons in ππ scattering. Published by the American Physical Society 2024

Timelike meson form factors beyond the elastic region from lattice QCD

We present a calculation of the vector-isovector timelike form factors of the pion and the kaon using lattice quantum chromodynamics. We calculate two-point correlation functions with mπ∼280 MeV, extracting both the finite-volume spectrum and matrix elements for these states created from the vacuum by a vector current. After determining the coupled-channel ππ,KK¯ scattering amplitudes, we perform the necessary correction for the significant finite-volume effects present in the current matrix elements, leading to the timelike form factors. We find these to be dominated by the presence of the ρ resonance, and we extract its decay constant by an analytic continuation of the amplitudes to the resonance pole. In addition, the spacelike pion form factor is determined on the same lattice configurations, and a dispersive parametrization is used to simultaneously describe the spacelike and elastic timelike regions. Published by the American Physical Society 2024

Piezoelectric deicing system for aeronautics: Extensional mode actuator and power supply

AbstractRecent research shows a growing interest in low‐power avionic deicing systems, in particular, those based on piezoelectric actuators for their energy efficiency. The system generates micrometric vibrations in the structure to delaminate and break the ice with a low power requirement. However, designing the power supply and its control for driving piezoelectric actuators is challenging due to their distinctive capacitive behavior at most frequencies, especially in deicing applications requiring high operational frequency. This contribution addresses the two cross‐dependent parts of the deicing system, that is the piezoelectric actuator designed for breaking any kind of ice on a large area and its power supply made of a 1 kW/200 V/2 MHz auxiliary resonant commutated pole inverter (ARCPI). The choice of this converter is based on the specific constraints of the application, such as varying the operating frequency with the actuator working conditions, the long cables and necessary insulation between the actuator and its supply, the soft‐switching operation and reactive energy balancing for a good efficiency. Based on these criteria, the converter was developed and realized in the laboratory. Deicing tests confirmed effective operation with a power input density of 122 mW/cm2, using nine piezoelectric patches per dm2.

An Improved Auxiliary Resonant Pole TNPC Inverter and Its Modulation Strategy

An Improved Auxiliary Resonant Pole TNPC Inverter and Its Modulation Strategy

Oscillating direct electric current formed by a resonant tunneling diode inside a cavity with periodically oscillating mirrors.

A novel phenomenon is described that enables the control of the flux of free electrons through a resonance tunneling diode (RTD) via coupling the RTD to a quantized electromagnetic mode in a dark cavity. As the control parameter, one uses here the distance between the two cavity mirrors (which are set to oscillate in time). The effect is illustrated by carrying out standard scattering calculations of the electron flux. However, the only efficient way to rationalize the phenomenon and to be able to select the proper distance between the two cavity mirrors is to employ non-Hermitian quantum mechanics and the language of discrete resonance poles of the scattering matrix. The demonstrated ability to control the flux of free electrons by using a dark cavity might open a new field of research and development of controllable RTD devices.

Unified framework of forced magnetic reconnection and Alfvén resonance

A unified linear theory that includes forced reconnection as a particular case of Alfvén resonance is presented. We consider a generalized Taylor problem in which a sheared magnetic field is subject to a time-dependent boundary perturbation oscillating at frequency ω0. By analyzing the asymptotic time response of the system, the theory demonstrates that the Alfvén resonance is due to the residues at the resonant poles, in the complex frequency plane, introduced by the boundary perturbation. Alfvén resonance transitions towards forced reconnection, described by the constant-psi regime for (normalized) times t≫S1/3, when the forcing frequency of the boundary perturbation is ω0≪S−1/3, allowing the coupling of the Alfvén resonances across the neutral line with the reconnecting mode, as originally suggested in Uberoi and Zweibel, (1999). Additionally, it is shown that even if forced reconnection develops for finite, albeit small, frequencies, the reconnection rate and reconnected flux are strongly reduced for frequencies ω0≫S−3/5.

Mixed NNLO QCD × electroweak corrections to single-Z production in pole approximation: differential distributions and forward-backward asymmetry

Radiative corrections in pole approximation, which are based on the leading contribution in a systematic expansion of amplitudes about resonance poles, naturally decompose into factorizable corrections attributed to the production or decay of the resonance and non-factorizable corrections induced by soft photon (or gluon) exchange between those subprocesses. In this paper we complete an earlier calculation of mixed QCD × electroweak corrections of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{O}\\left({\\alpha }_{{\ ext{s}}}\\alpha \\right)$$\\end{document} to the neutral-current Drell-Yan cross section in pole approximation by including the previously neglected corrections that are solely related to the Z-boson production process. We present numerical results both for differential distributions and for the forward-backward asymmetry differential in the lepton-pair invariant mass, which is the key observable in the measurement of the effective weak mixing angle at the LHC. Carefully disentangling the various types of factorizable and non-factorizable corrections, we find (as expected in our earlier work) that the by far most important contribution at \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{O}\\left({\\alpha }_{{\ ext{s}}}\\alpha \\right)$$\\end{document} originates from the interplay of initial-state QCD corrections and electroweak final-state corrections.

Quantum soft waveguides with resonances induced by broken symmetry

We consider two-dimensional, non-relativistic quantum system with asymptotically straight soft waveguide. We show that the local deformation of the symmetric waveguide can lead to the emerging of the embedded eigenvalues living in the continuous spectrum. The main problem of this paper is devoted to the analysis of weak perturbation of the symmetric system. We show that the original embedded eigenvalues turn to the second sheet of the resolvent analytic continuation and constitute resonances. We describe the asymptotics of the real and imaginary components of the complex resonant pole depending on deformation. Finally, we generalize the problem to three dimensional system equipped with a soft layer.

Unitary model analysis of f0(500) pole positions by continuously varying mπ : Comparison with discrete lattice predictions

Resonance, bound-state, and virtual-state pole positions of the f0(500) scalar meson are computed as a continuous function of pion mass in the framework of a unitarized and analytic coupled-channel model for scalar mesons, described as dynamical quark-antiquark states. The f0(500) is modeled with both light and strange qq¯ seeds, mixing with each other through the common S-wave ππ, KK¯, and ηη meson-meson decay channels. The few model parameters are fitted to experimental S-wave ππ phase shifts up to 1 GeV. In the case of the physical π± mass of 139.57 MeV, resonance poles at (460−i222) MeV and (978−i37.2) MeV are found for the f0(500) and f0(980), respectively. Resonance, bound-state, and virtual-state pole trajectories are computed and plotted as a function of pion masses up to 500 MeV, both in the complex-energy and complex-momentum planes. The results are discussed and compared to the most advanced lattice QCD computations employing interpolators that correspond to the qq¯ and meson-meson channels in the present model, that is, for a few discrete values of the unphysical pion mass in those lattice calculations. Published by the American Physical Society 2024

An improved soft-switching inverter to eliminate pre-charge current

To address the current stress problem brought on by the auxiliary resonant pole inverter’s pre-charge state, this paper gives an improved auxiliary circuit based on the original inverter. The improved circuit avoids a pre-charge state by adding auxiliary capacitors to form a resonant branch. In contrast to the original inverter, this inverter lowers the current stress on both the auxiliary and primary switches by resolving the pre-charge state’s current stress issue. As a result, the inverter’s losses are decreased, which raises the system’s efficiency. The working principle of this inverter is given in the paper. After a comparison and analysis of the inverter’s pre-charge state, an experiment is used to confirm the device’s viability.

Elastic nucleon-pion scattering amplitudes in the Δ channel at physical pion mass from lattice QCD

We present an investigation of pion-nucleon elastic scattering in the I(JP)=32(32+) channel using lattice QCD with degenerate up and down, strange and charm quarks with masses tuned to their physical values. We use an ensemble of twisted mass fermions with box size L=5.1 fm and lattice spacing a=0.08 fm and we consider the πN system in rest and moving frames up to total momentum P→2=3(2π/L)2=0.17 GeV2. We take into account the finite volume symmetries and S- and P-wave mixing, and use the Lüscher formalism to simultaneously constrain the J=1/2,ℓ=0 and J=3/2,ℓ=1 scattering amplitudes. We estimate the Δ resonance pole in the P-wave channel as well as the S-wave isospin-3/2 scattering length. Published by the American Physical Society 2024

Enhanced Classical Radiation Damping of Electronic Cyclotron Motion in the Vicinity of the Van Hove Singularity in a Waveguide

Abstract We study the damping process of electron cyclotron motion and the resulting emission in a waveguide using the classical Friedrichs model without relying on perturbation analysis such as Fermi’s golden rule. A Van Hove singularity appears at the lower bound (or cutoff frequency) of the dispersion associated with each of the electromagnetic field modes in the waveguide. In the vicinity of the Van Hove singularity, we found that not only is the decay process associated with the resonance pole enhanced (amplification factor ∼104) but the branch-point effect is also comparably enhanced. As a result, the timescale on which most of the decay occurs is dramatically shortened. Further, this suggests that the non-Markovian branch-point effect should be experimentally observable in the vicinity of the Van Hove singularity. Our treatment yields a physically acceptable solution without the problematic runaway solution that is well known to appear in the traditional treatment of classical radiation damping based on the Abraham–Lorentz equation.

Controlling collisional loss and scattering lengths of ultracold dipolar molecules with static electric fields

Trapped samples of ultracold molecules are often short-lived because close collisions between them result in trap loss. We investigate the use of shielding with static electric fields to create repulsive barriers between polar molecules to prevent such loss. Shielding is very effective even for RbCs, with a relatively low dipole moment, and even more effective for molecules such as NaK, NaRb, and NaCs, with progressively larger dipoles. Varying the electric field allows substantial control over the scattering length, which will be crucial for the stability or collapse of molecular Bose-Einstein condensates. This arises because the dipole-dipole interaction creates a long-range attraction that is tunable with electric field. For RbCs, the scattering length is positive across the range where shielding is effective because the repulsion responsible for shielding dominates. For NaK, the scattering length can be tuned across zero to negative values. For NaRb and NaCs, the attraction is strong enough to support tetra-atomic bound states, and the scattering length passes through resonant poles where these states cross threshold. For KAg and CsAg, there are multiple bound states and multiple poles. For each molecule, we calculate the variation of the scattering length with field and comment on the possibilities for exploring new physics. Published by the American Physical Society 2024

Lattice QCD study of πΣ−K¯N scattering and the Λ(1405) resonance

A lattice QCD computation of the coupled channel πΣ–K¯N scattering amplitudes in the Λ(1405) region is detailed. Results are obtained using a single ensemble of gauge field configurations with Nf=2+1 dynamical quark flavors and mπ≈200 MeV and mK≈487 MeV. Hermitian correlation matrices using both single baryon and meson-baryon interpolating operators for a variety of different total momenta and irreducible representations are used. Several parametrizations of the two-channel scattering K-matrix are utilized to obtain the scattering amplitudes from the finite-volume spectrum. The amplitudes, continued to the complex energy plane, exhibit a virtual bound state below the πΣ threshold and a resonance pole just below the K¯N threshold. Published by the American Physical Society 2024

Two-Pole Nature of the Λ(1405) Resonance from Lattice QCD.

This Letter presents the first lattice QCD computation of the coupled channel πΣ-K[over ¯]N scattering amplitudes at energies near 1405MeV. These amplitudes contain the resonance Λ(1405) with strangeness S=-1 and isospin, spin, and parity quantum numbers I(J^{P})=0(1/2^{-}). However, whether there is a single resonance or two nearby resonance poles in this region is controversial theoretically and experimentally. Using single-baryon and meson-baryon operators to extract the finite-volume stationary-state energies to obtain the scattering amplitudes at slightly unphysical quark masses corresponding to m_{π}≈200 MeV and m_{K}≈487 MeV, this study finds the amplitudes exhibit a virtual bound state below the πΣ threshold in addition to the established resonance pole just below the K[over ¯]N threshold. Several parametrizations of the two-channel K matrix are employed to fit the lattice QCD results, all of which support the two-pole picture suggested by SU(3) chiral symmetry and unitarity.

\(\sigma (500)\) Resonance Pole Positions as a~Function of \(m_\pi \): Analysis with a Unitary Coupled-channel Model

\(\sigma (500)\) Resonance Pole Positions as a~Function of \(m_\pi \): Analysis with a Unitary Coupled-channel Model

Measurement of KN scattering below the KN mass threshold

Abstract. We measured πE invariant mass spectra below and above the K¯N mass threshold in the K−d → NπE reaction in order to study the K¯N interaction and the Λ(1405) resonance. This reaction can be described by the two-step process: (i) K¯N1 → K¯N followed by (ii) K¯N2 → πΣ, where N1 and N2 are nucleons bound in the deuteron. We deduced the S -wave scattering amplitude of K¯N →K¯N in the framework of the K¯N πΣ coupled channel so as to reproduce the observed πΣ spectra in the I = 0 channel. We found a resonance pole at 1417.7-7.4+6.0 (fitting error)-1.0+1.1 (systematic error) - i[26.9-7.9+6.0 (fitting error)-2.0+1.7 (systematic error)]MeV/c2.

An Efficient Resonant Pole Inverter With Reliability Improvement of Soft-Switching in the Case of Open Failure of Any Auxiliary Device on Each Bridge Arm

An Efficient Resonant Pole Inverter With Reliability Improvement of Soft-Switching in the Case of Open Failure of Any Auxiliary Device on Each Bridge Arm