Showing papers on "Amplitude published in 2022"
TL;DR: In this article , the International Pulsar Timing Array (IPTA) was used to search for an isotropic stochastic gravitational wave background in the second data release of the PTA.
Abstract: ABSTRACT We searched for an isotropic stochastic gravitational wave background in the second data release of the International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns in North America, Europe, and Australia. In our reference search for a power-law strain spectrum of the form $h_c = A(f/1\, \mathrm{yr}^{-1})^{\alpha }$, we found strong evidence for a spectrally similar low-frequency stochastic process of amplitude $A = 3.8^{+6.3}_{-2.5}\times 10^{-15}$ and spectral index α = −0.5 ± 0.5, where the uncertainties represent 95 per cent credible regions, using information from the auto- and cross-correlation terms between the pulsars in the array. For a spectral index of α = −2/3, as expected from a population of inspiralling supermassive black hole binaries, the recovered amplitude is $A = 2.8^{+1.2}_{-0.8}\times 10^{-15}$. None the less, no significant evidence of the Hellings–Downs correlations that would indicate a gravitational-wave origin was found. We also analysed the constituent data from the individual pulsar timing arrays in a consistent way, and clearly demonstrate that the combined international data set is more sensitive. Furthermore, we demonstrate that this combined data set produces comparable constraints to recent single-array data sets which have more data than the constituent parts of the combination. Future international data releases will deliver increased sensitivity to gravitational wave radiation, and significantly increase the detection probability.
110 citations
TL;DR: In this article , the authors investigated the effect of cyclic uniaxial increasing-amplitude decreasing-frequency (CUIADF) loads on the fatigue strength, deformation, AE output activities, damage propagation and crack coalescence.
55 citations
TL;DR: In this paper , a multistage constant-amplitude-cyclic (MCAC) loading experiments were conducted on interbedded skarns to investigate and characterize fatigue mechanical behavior of the tested rock.
53 citations
24 Mar 2022
TL;DR: In this paper , a series of review articles on scattering amplitudes in gauge theory, gravity, and superstring theory is presented, from basic aspects to a selection of current research and developments.
Abstract: This is an introduction to, and invitation to read, a series of review articles on scattering amplitudes in gauge theory, gravity, and superstring theory. Our aim is to provide an overview of the field, from basic aspects to a selection of current (2022) research and developments.
49 citations
48 citations
43 citations
24 Mar 2022
TL;DR: In this article , the double copy of three-point amplitudes has been studied in the context of gravity and general relativity, and it has been shown that it can extend elegantly to exact solutions.
Abstract: Scattering amplitudes have their origin in quantum field theory, but have wide-ranging applications extending to classical physics. We review a formalism to connect certain classical observables to scattering amplitudes. An advantage of this formalism is that it enables us to study implications of the double copy in classical gravity. We discuss examples of observables including the total change of a particle’s momentum, and the gravitational waveform, during a scattering encounter. The double copy also allows direct access to classical solutions in gravity. We review this classical double copy starting from its linearised level, where it originates in the double copy of three-point amplitudes. The classical double copy extends elegantly to exact solutions, making a connection between scattering amplitudes and the geometric formulation of general relativity.
42 citations
TL;DR: In this article , a review summarizes the research status of four main aspects of multiaxial fatigue under random/variable amplitude loadings, namely, multi-axial fatigue criterion, method for critical plane determination, cycle counting method and damage accumulation criterion.
Abstract: PurposeEngineering components/structures with geometric discontinuities normally bear complex and variable loads, which lead to a multiaxial and random/variable amplitude stress/strain state. Hence, this study aims how to effectively evaluate the multiaxial random/variable amplitude fatigue life.Design/methodology/approachRecent studies on critical plane method under multiaxial random/variable amplitude loading are reviewed, and the computational framework is clearly presented in this paper.FindingsSome basic concepts and latest achievements in multiaxial random/variable amplitude fatigue analysis are introduced. This review summarizes the research status of four main aspects of multiaxial fatigue under random/variable amplitude loadings, namely multiaxial fatigue criterion, method for critical plane determination, cycle counting method and damage accumulation criterion. Particularly, the latest achievements of multiaxial random/variable amplitude fatigue using critical plane methods are classified and highlighted.Originality/valueThis review attempts to provide references for further research on multiaxial random/variable amplitude fatigue and to promote the development of multiaxial fatigue from experimental research to practical engineering application.
39 citations
TL;DR: In this paper , it was shown that the produced gravitational wave spectrum matches the NANOGrav SGWB signal only when this process happens through a first-order phase transition, which is the same as in this paper.
35 citations
TL;DR: In this paper , the authors investigated the soliton wave structures of the nonlinear potential Kadomtsev-Petviashvili and Calogero-Degasperis equations by employing the direct algebraic method.
Abstract: This paper investigates the soliton wave structures of the nonlinear potential Kadomtsev–Petviashvili and Calogero–Degasperis equations by employing the direct algebraic method. These equations are used to investigate the (2+1)-dimensional interaction of a Riemann wave propagating along the y-axis with a long wave along the x-axis and the stability of the one-soliton solution of the well-known Korteweg–de Vries (KdV) equation under transverse perturbations. Since the wavelength of weakly dispersive, nonlinear waves is longer than their amplitude and their variations in the second spatial dimension (rescaled y) are slower than those in the principal propagation direction (rescaled x), the studied models’ soliton wave solutions are used to describe wave dynamics. Many solutions are obtained and demonstrated by plotting them in 2D, 3D, and contour plots. The implemented analytical scheme’s performance verifies its effectiveness and power. All solutions’ accuracy is checked by putting them back into their original model.
35 citations
TL;DR: In this paper , the authors compute the infrared divergent contribution to the real part of the two-loop eikonal and from it derive the radiative contribution of the deflection angle for spins aligned to the orbital angular momentum, the loss of angular momentum and the zero frequency limit of the energy spectrum for any spin.
24 Mar 2022
TL;DR: The soft limits of scattering amplitudes have been extensively studied due to their essential role in the computation of physical observables in collider physics, and the universal factorisation that occurs in these kinematic limits has been shown to be related to conservation laws associated with asymptotic, or large, gauge symmetries as mentioned in this paper .
Abstract: The soft limits of scattering amplitudes have been extensively studied due to their essential role in the computation of physical observables in collider physics. The universal factorisation that occurs in these kinematic limits has been shown to be related to conservation laws associated with asymptotic, or large, gauge symmetries. This connection has led to a deeper understanding of the symmetries of gauge and gravitational theories and to a reformulation of scattering amplitudes in a basis of boost eigenstates which makes manifest the two-dimensional global conformal symmetry of the celestial sphere. The recast, or celestial, amplitudes possess many of the properties of conformal field theory (CFT) correlation functions which has suggested a path towards a holographic description of asymptotically flat spacetimes. In this review we consider these interconnected developments in our understanding of soft theorems, asymptotic symmetries and CFT with a focus on the structure and symmetries of the celestial amplitudes and their holographic interpretation.
TL;DR: In this paper , the characteristics of acoustic gravity waves from the eruption of the Hunga-Tonga-Hunga-Hapai volcano detected at different infrasound stations of the Infrasound Monitoring System and at a network of low-frequency microbarographs in the Moscow region are studied.
Abstract: The characteristics of acoustic-gravity waves (waveforms, time durations, amplitudes, azimuths and horizontal phase speeds) from the eruption of the Hunga-Tonga-Hunga-Hapai volcano detected at different infrasound stations of the Infrasound Monitoring System and at a network of low-frequency microbarographs in the Moscow region are studied. Using the correlation analysis of the signals at different locations, six arrivals of signals from the volcano, which made up to two revolutions around the Earth, were detected. The Lamb mode of acoustic gravity waves from the volcano eruption is identified and the effect of this mode on generation of tsunami waves and variation of aerosol concentration is studied. The energy released from an underwater volcano into the atmosphere is estimated from the parameters of the Lamb wave and compared with the energy released from the most powerful nuclear bomb of 58 Mt TNT.
TL;DR: In this article , the amplitude-action relation was used to obtain the radial action directly from the amplitude, and matched the known overlapping terms in the post-Newtonian expansion.
Abstract: We complete the calculation of conservative two-body scattering dynamics at fourth post-Minkowskian order, i.e., O(G^{4}) and all orders in velocity, including radiative contributions corresponding to the tail effect in general relativity. As in previous calculations, we harness powerful tools from the modern scattering amplitudes program including generalized unitarity, the double copy, and advanced multiloop integration methods, in combination with effective field theory. The classical amplitude involves complete elliptic integrals, and polylogarithms with up to transcendental weight 2. Using the amplitude-action relation, we obtain the radial action directly from the amplitude, and match the known overlapping terms in the post-Newtonian expansion.
TL;DR: In this paper , the symmetry resolution of entanglement in the presence of long-range couplings is investigated, where the entropy of each symmetry sector is calculated via the charged moments of the reduced density matrix.
Abstract: We investigate the symmetry resolution of entanglement in the presence of long-range couplings. To this end, we study the symmetry-resolved entanglement entropy in the ground state of a fermionic chain that has dimerised long-range hoppings with power-like decaying amplitude—a long-range generalisation of the Su–Schrieffer–Heeger model. This is a system that preserves the number of particles. The entropy of each symmetry sector is calculated via the charged moments of the reduced density matrix. We exploit some recent results on block Toeplitz determinants generated by a discontinuous symbol to obtain analytically the asymptotic behaviour of the charged moments and of the symmetry-resolved entropies for a large subsystem. At leading order we find entanglement equipartition, but comparing with the short-range counterpart its breaking occurs at a different order and it does depend on the hopping amplitudes.
TL;DR: In this article , the authors investigated resonant collisions of lumps with periodic solitons of the Kadomtsev-Petviashvili I equation and showed that the lumps would become instantons, as a result of two types of resonant collision with spatially periodic (quasi-1D) soliton chains.
Abstract: Resonant collisions of lumps with periodic solitons of the Kadomtsev–Petviashvili I equation are investigated in detail. The usual lump is a stable weakly localized two-dimensional soliton, which keeps its shape and velocity in the course of the evolution from t → −∞ to t → +∞. However, the lumps would become localized in time as instantons, as a result of two types of resonant collisions with spatially periodic (quasi-1D) soliton chains. These are partly resonant and fully resonant collisions. In the former case, the lump does not exist at t → −∞, but it suddenly emerges from the periodic soliton chain, keeping its amplitude and velocity constant as t → +∞; or it exists as t → −∞ and merges into the periodic chain, disappearing at t → +∞. In the case of the fully resonant interaction, the lump is an instanton, which emerges from the periodic chain and then merges into another chain, keeping its identify for a short time. Thus, in the case of the fully resonant collisions, the lumps are completely localized in time as well as in two-dimensional space, and they are call rogue lumps.
TL;DR: In this paper , the authors examined the presence and maturation of low-frequency (<12 Hz) cortical speech tracking in infants by recording EEG longitudinally from 60 participants when aged 4-, 7- and 11- months as they listened to nursery rhymes.
TL;DR: In this paper , the authors explore whether freeing the total neutrino mass, which can suppress small-scale structure growth, improves EDE's fit to galaxy clustering, and they find that the baseline EDE model (with $M_{
u}=0.06\,{\rm eV}$) provides the overall best fit.
Abstract: The early dark energy (EDE) solution to the Hubble tension comes at the cost of an increased clustering amplitude that has been argued to worsen the fit to galaxy clustering data. We explore whether freeing the total neutrino mass $M_{
u}$, which can suppress small-scale structure growth, improves EDE's fit to galaxy clustering. Using Planck Cosmic Microwave Background and BOSS galaxy clustering data, a Bayesian analysis shows that freeing $M_{
u}$ does not appreciably increase the inferred EDE fraction $f_{\rm EDE}$: we find the 95% C.L. upper limits $f_{\rm EDE}<0.092$ and $M_{
u}<0.15\,{\rm eV}$. Similarly, in a frequentist profile likelihood setting (where our results support previous findings that prior volume effects are important), we find that the baseline EDE model (with $M_{
u}=0.06\,{\rm eV}$) provides the overall best fit. For instance, compared to baseline EDE, a model with $M_
u=0.24\,{\rm eV}$ maintains the same $H_0$(km/s/Mpc)=(70.08, 70.11, respectively) whilst decreasing $S_8$=(0.837, 0.826) to the $\Lambda$CDM level, but worsening the fit significantly by $\Delta \chi^2=7.5$. For the datasets used, these results are driven not by the clustering amplitude, but by background modifications to the late-time expansion rate due to massive neutrinos, which worsen the fit to measurements of the BAO scale.
TL;DR: In this paper , the amplitude and power index of GWs induced by the peaked curvature perturbation with a dust-like post inflationary era with $-0.091/lesssim w\lesssim 0.048
Abstract: Recently, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) claimed the detection of a stochastic common-spectrum process of the pulsar timing array (PTA) time residuals from their 12.5 year data, which might be the first detection of the stochastic background of gravitational waves (GWs). We show that the amplitude and the power index of such waves imply that they could be the secondary GWs induced by the peaked curvature perturbation with a dust-like post inflationary era with $-0.091\lesssim w\lesssim0.048$. Such stochastic background of GWs naturally predicts substantial existence of planet-mass primordial black holes (PBHs), which can be the lensing objects for the ultrashort-timescale microlensing events observed by the Optical Gravitational Lensing Experiment (OGLE).
TL;DR: In this paper , a one-dimensional air-sea coupled tsunami simulation with bathymetry data was presented, showing that an input atmospheric pressure pulse with a short half-wavelength of 50 km, which is shorter than the length of the ocean bottom slopes, caused an amplitude increase via the Proudman resonance effect near the deep trench.
Abstract: Abstract A large eruption of the Hunga Tonga-Hunga Haʻapai volcano in Tonga on January 15, 2022 generated air–sea coupled tsunamis observed at the ocean-bottom pressure sensor network along the Japan Trench (S-net) in Japan. Initial tsunamis from the 2022 Tonga eruption, detected by 106 ocean-bottom pressure sensors, were well modeled by an air–sea coupled tsunami simulation, with a simple atmospheric pressure pulse as sine function, having a half-wavelength of 300 km and a peak amplitude of 2 hPa. A one-dimensional air–sea coupled tsunami simulation having a simple bathymetry shows that an input atmospheric pressure pulse with a short half-wavelength of 50 km, which is shorter than the length of the ocean bottom slopes, caused an amplitude increase via the Proudman resonance effect near the deep trench. The wavefront distortion due to the separation of the air–sea coupled wave propagating with a speed of 312 m/s and tsunami propagating with that of $$\sqrt{gd}$$ gd , where g is gravity acceleration and d is the ocean depth, is also significant near the shore. In contrast, these effects are not significant for the half-wavelength of the input atmospheric pressure pulse of 300 km. These results indicate that the air–sea coupled tsunami propagating through the trench is sensitive to the wavelength of an atmospheric pressure pulse. Graphical Abstract
TL;DR: Chin et al. as discussed by the authors investigated a generalized variable-coefficient version of the Kadomtsev-Petviashvili equation, making use of symbolic computation, with respect to the amplitude or elevation of the relevant wave.
TL;DR: In this paper , Raman-active charge-density wave (CDW) amplitude modes were observed in CsV3Sb5, which are collective excitations typically thought to emerge out of frozen soft phonons, although phonon softening is elusive experimentally.
Abstract: The kagome lattice provides a fertile platform to explore novel symmetry-breaking states. Charge-density wave (CDW) instabilities have been recently discovered in a new kagome metal family, commonly considered to arise from Fermi-surface instabilities. Here we report the observation of Raman-active CDW amplitude modes in CsV3Sb5, which are collective excitations typically thought to emerge out of frozen soft phonons, although phonon softening is elusive experimentally. The amplitude modes strongly hybridize with other superlattice modes, imparting them with clear temperature-dependent frequency shift and broadening, rarely seen in other known CDW materials. Both the mode mixing and the large amplitude mode frequencies suggest that the CDW exhibits the character of strong electron-phonon coupling, a regime in which phonon softening can cease to exist. Our work highlights the importance of the lattice degree of freedom in the CDW formation and points to the complex nature of the mechanism.
TL;DR: In this paper , the authors applied the theoretical framework of antisymmetrized molecular dynamics with the Gogny D1S density functional to describe the shape coexistence in the N = 28 isotones 40Mg, 42Si, and 44S.
Abstract: In neutron-rich nuclei neighboring 42Si, the quenching of the N = 28 shell gap occurs and is expected to induce shape coexistence in their excitation spectra. We have applied the theoretical framework of antisymmetrized molecular dynamics with the Gogny D1S density functional to describe the shape coexistence in the N = 28 isotones 40Mg, 42Si, and 44S. We show that different nuclear shapes coexist in these nuclei: Rigid shapes with different deformations coexist in 40Mg and 42Si, while 44S exhibits large-amplitude collective motion and does not have any particular shape. These characteristics are reflected well in the monopole transition strengths that can be utilized as a probe for the shape coexistence.
TL;DR: In this article , a novel ultrawideband branch waveguide coupler with low amplitude imbalance was proposed, which is based on a new waveguide obtained by symmetrically increasing the waveguide width.
Abstract: In this article, we present a novel ultrawideband branch waveguide coupler (BWC) with low amplitude imbalance. This novel design is based on a new structure of branch waveguide obtained by symmetrically increasing the waveguide width. The coupling degree can be independently controlled by the height and width of the new branch waveguide, which significantly increases the design flexibility. In addition, this structure can produce a transmission zero (TZ), and a concept to improve the fractional bandwidth of the BWC with out-of-band TZ is proposed. Based on the analysis, the design guidelines for the novel BWC are provided. For a given center frequency, an n-branch novel BWC can be easily designed. Moreover, because of the larger branch waveguide height, this novel design has greatly eased the machining difficulty. Finally, to verify the design concept, a $W$ -band eight-branch prototype is processed and measured. In full $W$ -band, the amplitude imbalance is less than 0.52 dB, the phase imbalance is less than 2.5°, the return loss (RL) is greater than 21.4 dB, and the isolation is greater than 20.5 dB. The simulation and experimental results are in good agreement.
TL;DR: In this paper , the authors analyzed nonlinear effects on dynamical feathers of soliton waves in a nonlinear Schrödinger equation (NLSE) including the parabolic law, and retrieved a group of dark solitons to the governing model using the Kudryashov method.
TL;DR: Based on a variable-boostable chaotic system, a conservative chaotic system with controllable amplitude and offset is proposed in this paper , which exhibits rich symmetrical dynamics under different parameters and initial conditions.
Abstract: Based on a variable-boostable chaotic system, a conservative chaotic system with controllable amplitude and offset is proposed. The system exhibits rich symmetrical dynamics under different parameters and initial conditions. More interestingly, a parameter of memristor poses a partial amplitude control to a system variable. Furthermore, the derived memristive system has the property of offset boosting, where an independent constant can be introduced for free rescaling of the average value of a system variable. Experimental circuit with a memristor rheostat is designed for amplitude control. Circuit simulation based on Multisim software agrees well with the systematic analysis and numerical exploration. To the best of our knowledge, in the literature there is no 3D conservative memristive system reported with such properties as amplitude control and offset boosting.
TL;DR: In this article , the authors incorporate massless bosonic particles in the initial states into the formalism and show that in the classical limit they emerge from coherent states due to their nature as superpositions of multiparticle states.
Abstract: Waveforms play an important role in the detection of gravitational-wave events from binary mergers. A useful formalism to deal with the two-body problem in gravity is to use quantum scattering amplitudes in a particular expansion and extract classical observables. As an extension to previous work, the authors incorporate massless bosonic particles in the initial states into the formalism and show that in the classical limit they emerge from coherent states due to their nature as superpositions of multiparticle states.
TL;DR: In this paper , a perfect terahertz (THz) metamaterial absorber (MMA) based on bulk Dirac semimetal (BDS) and strontium titanate (STO) is proposed and numerically analyzed.
Abstract: A perfect terahertz (THz) metamaterial absorber (MMA) based on bulk Dirac semimetal (BDS) and strontium titanate (STO) is proposed and numerically analyzed. By integrating two new materials with adjustable dielectric constant in one structure, the performance of this design can be flexibly controlled. The simulation results show that as the Fermi energy (EF) of BDS varies from 10 meV to 70 meV, the absorption rate can be tuned from 89% to 100%, with the resonant frequency exhibits a tiny blue shift. Meanwhile, the center frequency can be tuned by varying the temperature of STO from 150 K to 300 K. In addition, the absorption reaches 1 at 0.69 THz when the temperature of STO and EF of BDS are set as 200 K and 30 meV, respectively. The coupled-mode theory (CMT) and perturbation theory are used to explore the reason of perfect absorption and frequency tunable mechanism, respectively. Further research and analysis prove that this designed absorber shows outstanding feature of angular insensitivity. Our work provides a potential guide for designing multifunctional THz devices, such as photodetectors, modulators, sensors, and so on.
01 Apr 2022
TL;DR: In this article , a decoupled fractional Laplacian (DFL) viscoelastic wave equation is proposed to characterize the Earth's frequency-independent Q behavior in the vertical transversely isotropic (VTI) media.
Abstract: Seismic velocity and attenuation anisotropy are ubiquitous in the crust and upper mantle, significantly modulating the characteristics of seismic wave propagation in the Earth's interior. Accurate seismic wave modeling of velocity and attenuation anisotropy is essential for the understanding of wave propagation in the Earth's interior as well as constructing global and region-scale seismic full waveform tomography. Here, we derive a decoupled fractional Laplacian (DFL) viscoelastic wave equation to characterize the Earth's frequency-independent Q behavior in the vertical transversely isotropic (VTI) media. We verify the accuracy of the proposed viscoelastic wave equation by 2D synthetic examples; to show its applicability in crustal-scale seismic modeling, we present an example of 3D seismic wave propagation in the realistic Salton Trough model. Through extensive numerical tests, we conclude that the proposed viscoelastic wave equation is superior in four aspects. First, the viscoelastic wave equation takes VTI anisotropy of both velocity and attenuation into account and can describe the strong direction-dependent attenuation. Second, our derivation contains spatially independent Laplacians, and thus the proposed wave equation enjoys higher simulation accuracy for heterogeneous Q media. Third, the new viscoelastic wave equation can decouple the amplitude decay and the phase distortion, which is appealing for improving the resolution in seismic imaging and inversion. Lastly, compared to viscoelastic wave equations with time-fractional operators, our scheme has higher computational efficiency by avoiding substantial wavefield storage.