Particle Oscillations Research Articles

Electroweak Axion in Light of GRB221009A

Very high energy (VHE) photons may have a higher survival rate than that expected in standard-model physics, as suggested by the recently reported gamma ray burst GRB221009A. While a photon-axion like particle (ALP) oscillation can boost the survival rate of the VHE photons, current works have not been based on concrete particle models, leaving the identity of the corresponding ALP unclear. Here, we show that the required ALP scenario is consistent with the electroweak axion with an anomaly free Z 10 Froggatt–Nielsen symmetry.

Massive particle pair production and oscillation in Friedman Universe: reheating energy and entropy, and cold dark matter

Suppose that the early Universe starts with a cosmological Lambda -term (dark energy) originating from quantum spacetime at the Planck scale. Dark energy drives inflation and reheating by reducing its value for massive particle–antiparticle pairs production and oscillation, resulting in a holographic and massive pair plasma state. The back-and-forth reaction of dark energy and massive pairs slows inflation to its end and starts reheating by rapidly producing stable and unstable pairs. We introduce the Boltzmann-type rate equation describing the back-and-forth reaction. It forms a close set with Friedman equations and reheating equations for unstable pairs decay to relativistic particles. The numerical solutions show preheating, massive pairs dominated and genuine reheating episodes. We obtain the reheating temperature and entropy in terms of the tensor-to-scalar ratio 0< r < 0.047 consistently with observations. Stable massive pairs represent cold dark matter particles and weakly interact with dark energy. The resultant cold dark matter abundance Omega _csim 10^{-1} is about a constant in time.

Axion effects on gamma-ray spectral irregularities with AGN redshift uncertainty

We investigate the photon-axionlike particle (ALP) oscillation effects on TeV gamma-ray spectral irregularities from the uncertain redshift active galactic nuclei (AGN) VER J0521+211. The gamma-ray spectra are measured by Fermi-LAT and VERITAS with the three flux states in 2013 and 2014. We set the combined constraints on the ALP parameter ($m_a, g_{a\gamma}$) space with these states and test the extragalactic background light (EBL) absorption effect on ALP constraints with the redshift limit scenarios $z_0\sim\mathcal{O}(0.1-0.3)$. The 99% $\rm C.L.$ photon-ALP combined constraints set by VER J0521+211 are roughly at $g_{a\gamma} \gtrsim 2.0\times 10^{-11} \rm \, GeV^{-1}$ for $1.0\times10^{-9} \, {\rm eV} \lesssim m_a \lesssim 1.0\times10^{-7} \, {\rm eV}$. We find no clear connection between the redshift limit scenarios and the photon-ALP constraints. Both the underestimated and overestimated redshifts can affect the constraint results.

Quantifying fabric anisotropy of granular materials using wave velocity anisotropy: a numerical investigation

Fabric anisotropy is a sought-after micro index to correlate macro mechanical responses of granular materials. In this work, the discrete-element method is utilised to simulate multi-directional bender element tests in granular soils to obtain the evolution of wave velocities during drained conventional triaxial (CT) and true triaxial (TT) tests; the contact normal-based fabric is simultaneously monitored for bridging the fabric anisotropy and wave velocity anisotropy. The results show that stress-normalised wave velocities and microscopic fabric, including contact normal distribution and coordination number, remain nearly constant until a stress ratio threshold is reached. After the threshold value is reached, stress-normalised wave velocities start to decrease, especially in the minor principal stress direction, accompanied by significant adjustment of coordination number and fabric anisotropy. The results also reveal that the normalised wave velocity depends on the contact normal densities in the wave propagation and particle oscillation directions. With the contact normal distribution represented by a density function, a good linear relationship between the microscopic fabric anisotropy and macroscopic wave velocity anisotropy is obtained for both CT and TT tests.

On the quadratic wave equation with randomized oscillating coefficients

In this paper, we consider the asymptotic behavior of the solutions of the quadratic wave equations with perturbed oscillating coefficients which are very important mathematical models in describing the oscillation of particles imposed with time‐dependent electromagnetic fields. By the application of microlocal analysis and stochastic analysis, this paper makes a delicate classification of various types of time‐dependent oscillating coefficients on the principal quantum harmonic oscillator part and explores the corresponding regularity behavior and ‐estimates of the solution of the equation. It is interesting to find out that weak or mild oscillations will not cause any energy growth, while regular and strong oscillations will lead to polynomial or exponential growth of the energy. This is meaningful to help us explore the energy conversion mechanism in the electromagnetic field. Furthermore, in order to demonstrate the optimality of the ‐estimates, typical counterexamples with periodic coefficients will be constructed to show the lower bound of growth rate by the application of harmonic analysis and instability arguments. Compared with formal literatures focusing on the constant coefficients, current results in this paper reveal the essential relation between oscillation types and energy growth.

Massive particle pair production and oscillation in Friedman Universe: its effect on inflation

We study the classical Friedman equations for the time-varying cosmological term tilde{Lambda } and Hubble function H, together with quantised field equations for the production of massive Mgg H particles, namely, the tilde{Lambda }CDM scenario of dark energy and matter interactions. Classical slow components {mathcal O}(H^{-1}) are separated from quantum fast components {mathcal O}(M^{-1}). The former obeys the Friedman equations, and the latter obeys a set of nonlinear differential equations. Numerically solving equations for quantum fast components, we find the production and oscillation of massive particle-antiparticle pairs in microscopic time scale {mathcal O}(M^{-1}). Their density and pressure averages over microscopic time do not vanish. It implies the formation of a massive pair plasma state in macroscopic time scale {mathcal O}(H^{-1}), whose effective density and pressure contribute to the Friedman equations. Considering the inflation driven by the time-varying cosmological term and slowed down by the massive pair plasma state, we obtain the relation of spectral index and tensor-to-scalar ratio in agreement with recent observations. We discuss the singularity-free pre-inflation, the CMB large-scale anomaly, and dark-matter density perturbations imprinting on power spectra.

Correlation between Density of Reentry Plasma and Frequency of Attenuated Electromagnetic Signals Based on Laboratory Measurements

Upon reentering the Earth’s atmosphere from space, a reentry vehicle becomes enshrouded in an ionization layer. This layer is known as the reentry plasma sheath and is caused by aerodynamic heating. Owing to the oscillation of charged particles in the reentry plasma sheath, the electromagnetic waves for communication between the vehicle and ground are attenuated. Analysis of the plasma density and attenuation of electromagnetic waves in a reentry plasma environment would require experimentation in an environment in which an actual aircraft reenters the atmosphere. Alternatively, an experiment in a large-scale plasma wind tunnel would be necessary. Unfortunately, these experiments would be extremely costly. Therefore, in this study, the reentry plasma was reproduced at laboratory scale using the hot refractory anode vacuum arc (HRAVA) method. In addition, the pressure in the vacuum chamber was used as a variable to probe the characteristics of the reentry plasma according to the altitude. The plasma density and attenuation of electromagnetic waves propagating through the plasma medium were measured using heterodyne interferometry and reflectometry capable of frequency analysis in the range of 10−35 GHz. The results confirmed that the plasma density and attenuation of the electromagnetic waves increased as the pressure in the vacuum chamber increased.

The one-dimensional Coulomb oscillator

We consider the one-dimensional oscillations of a charged point particle under the restoring Coulomb force. We find that, for very small amplitudes, the speed of the particle remains almost constant. We also obtain the exact analytical expression for finding the oscillation period. It turns out to be a monotonically increasing function of the amplitude. For small amplitudes, this quantity is directly proportional to the amplitude itself.

Propagation characteristics of longitudinal modes in dusty plasmas

The space-time correlation function has been obtained in strongly coupled dusty plasmas (SCDPs) using equilibrium molecular dynamics (EMD) simulations. The simulated results for three-dimensional (3D) SCDPs with suitable normalization are computed over a wide domain of plasma parameters (Γ, κ) in a microcanonical ensemble. The EMD simulations indicate that different modes of propagated wave in SCDPs are analyzed for four different values of wave number (k). New investigations of normalized longitudinal current correlation function CL(k, t) show that the amplitude of oscillation and frequency of propagated modes increase with an increase in k. The obtained results for longitudinal modes of oscillation indicate that the dust particles remain in damping behavior at the low Γ, damped oscillation with decreasing amplitude inside decaying exponential envelope at intermediate Г, and sinusoidal oscillation at high Г, depending on κ. The system size (N) does not significantly affect the propagated modes of oscillation, while the periodic oscillation shifts toward higher Γ with increasing N and κ. The computations show that normalized longitudinal CL(k, t) current correlation particularly depend on Coulomb coupling (Γ), Debye screening (κ), and wave number (k). In our simulations, the frequency and the amplitude of oscillation of the dust particles decrease with an increment of κ and system size (N), but the frequency increases and the amplitude decreases with increasing Γ, as expected. It has been demonstrated that the EMD method is used to study the different propagated modes in dusty plasma systems and can be used to predict the damping behavior, damped oscillation, and periodic phenomena in 3D strongly coupled SCDPs.

Spontaneous symmetry-breaking of the active cluster drives the directed movement and self-sustained oscillation of symmetric rod-like passive particles.

Active particles without detailed balance can rectify their random motions to drive the directed movement or rotation of asymmetric passive obstacles. However, whether they can drive the directed movement of symmetric passive obstacles is still unclear. Here, we show that a rod-like passive particle which is fixed to move along the x-axis in an active bath can keep long-lived directed movement at nearly constant speed due to the spontaneous symmetry breaking of the neighboring active particle cluster. If the passive particle is further confined by a harmonic potential, it may undergo self-sustained periodic oscillation for an appropriate length of the passive particle and self-propelled velocity of active particles. The restoring force from the harmonic potential will trigger the velocity jump-off and thus lead to self-sustained periodic oscillation. Remarkably, the relationship between the velocity of the passive particle and the external force shows that the effective viscosity of the active bath may become negative in some regime. Finally, we develop a minimum 1D theoretical model to further probe the mechanism underlying the directed movement and self-sustained oscillation of the passive particle. Our findings reveal the effect of the moving boundary on the active bath and demonstrate a novel method to extract practical mechanical work from the active bath to propel microdevices.

Inertial migration of non-spherical particles in straight microfluidic channels

The paper reports on simulations of particulate flows in square ducts with oblate and prolate particles at a bulk Reynolds number of 100 and dilute particle concentration. Inertial migration leads to focusing of particles in specific regions of the cross section. It is observed that these positions are different for the non-spherical particles compared to those obtained with spherical ones. Prolate particles exhibit Jeffery-type orbits, while oblate particles rotate around their axis of symmetry. As a result, the rotation-induced migration of prolates is much slower than for spheres and oblates. An analysis of the surrounding flow is used to show differences in the velocity field. In a second set of simulations, the particle concentration was increased by a factor of 4 with the same domain size, so that neighboring particles influence each other. The duration until focusing is achieved is substantially increased. The focusing position moves slightly to the wall, and further effects are generated. Steady particle oscillations in position are seen for spheres, and the formation of particle trains is observed in all cases. The interaction of prolate particles is particularly complex and addressed in substantial detail.

Nonlinear field effects in the collector ring due to large-amplitude particle oscillations

In the frame of the FAIR project, the Collector Ring (CR) is planned to be built for efficient cooling of antiprotons and rare isotope beams [1]. In order to accept hot beam from separators large acceptances are required. This paper examines the effects which can influence the beam dynamics due to large betatron oscillation amplitude and momentum spread. Using analytic expressions, the amplitude-dependent tune shifts driven by sextupole magnets, the fringe field of quadrupole magnets, and kinematics effects have been calculated. The obtained results have been compared with numerical simulations by means of precise multi-turn particle tracing. The tracking analysis for the CR has been performed considering the real shape of the magnetic field of the wide aperture quadrupole. We report on quantitative studies of the effects on the dynamic aperture of the rings.

Relativistic Hydrodynamic Interpretation of de Broglie Matter Waves

We present a classical hydrodynamic analog of free relativistic quantum particles inspired by de Broglie’s pilot wave theory and recent developments in hydrodynamic quantum analogs. The proposed model couples a periodically forced Klein–Gordon equation with a nonrelativistic particle dynamics equation. The coupled equations may represent both quantum particles and classical particles driven by the gradients of locally excited Faraday waves. Exact stationary solutions of the coupled system reveal a highly nonlinear mechanism responsible for the self-propulsion of free particles, leading to the onset of unsteady motion. Although the model is essentially nonrelativistic, a stabilizing mechanism for any particle traveling close to the wave signaling speed emerges through the coupling with the wavefield. Consequently, inline particle oscillations comparable to de Broglie’s wavelength are realized through this fully-classical model, suggesting a new classical interpretation for the motion of relativistic quantum particles.

Quasiperiodic oscillation around charged black holes in Einstein–Maxwell-scalar theory

In the present paper, first, we study the event horizon properties of charged black holes (BHs) in Einstein Maxwell-scalar (EMS) gravity. Then, we investigate the circular motion of test particles’ around the BH in the EMS gravity. We also analyze the effects of the EMS parameters on the position of innermost circular orbits (ISCOs), energy, and angular momentum of the test particles corresponding to circular orbits. We provide detailed studies of the efficiency of energy release from EMS BHs based on the Hartle–Thorne model and fundamental frequencies of oscillations of particles along their circular stable orbits. Moreover, we have explored possible values of upper and lower frequencies of twin-peak quasiperiodic oscillations (QPOs) around the BHs. Finally, we obtain relationships between the BH charge and the EMS parameters using observational data from the QPOs detected in the microquasars: GRS 1905+105, GRO J 1655-40, H 1745+322, and XTE 1550-564.

Particle oscillation at corrugated membrane-water interface: An in-situ direct observation and implication to membrane fouling control

Membrane surface patterning is an emerging technique for membrane fouling control. However, the underlying mechanism for this technique has not been well understood due to the lack of direct evidence on the flow field and the associated contaminant transport at the membrane-water interface. Therefore, an in-situ real-time observation system was constructed in this study with the assistance of computational fluid dynamics (CFD) simulation, and used to determine the transport and deposition behaviors of particle tracers on a corrugated microfiltration membrane surface (sawtooth shape, height ≈ 197 ± 14.7 μm, width ≈ 805.5 ± 44.5 μm). It was observed that most particles traveled wavily along the membrane surface pattern. Meanwhile, The particles entering the pattern valley were (i) trapped stagnantly at Ul = 0.05 m/s (Re = 228), while oscillated (ii) spirally in the direction of the pattern valley at Ul = 0.08 m/s (Re = 364), and (iii) irregularly at Ul = 0.1 m/s (Re = 445). During oscillation, some particles were able to escape the valley and return to the bulk flow. Complementary numerical simulation results indicated that the surface pattern induced local turbulence (wake) and boundary layer separation were the major mechanisms underlying the observed particle behaviors. These intriguing results gave rise to an intuitive understanding of the dynamics of particle transportation associated with patterned membrane filtration. Accordingly, a self-cleaning membrane may be prepared by optimizing the patterns as well as the superficial liquid velocities to invoke strong wake flow capable of mitigating particle deposition on membrane surfaces.

Quasi-periodic oscillations of test particles and red–blue shifts of photons in the charged-Kiselev black hole with cloud of strings

Here we examine the circular motion of test particles and photons in the spacetime geometry of the charged black hole surrounded by quintessence and clouds of strings for the equation of state parameter ω q = − 2 / 3 . We observe that there exist stable circular orbits in this geometry for very small values of the quintessence and the string cloud parameters, i.e., 0 < γ < < 1 and 0 < α < < 1 . We also observe that if the values of γ and α get increase, then the test particle can more easily escape the gravitational field of the black hole. While the effect of the charge Q of the black hole on the effective potential is just opposite to that of the parameters γ and α . Further we investigate the quasi-periodic oscillations of test particles near the stable circular orbits in the vicinity of the black hole considered here. With the increasing values of Q , the stable circular orbits move away from the central black hole, therefore, one can observe lower epicyclic frequencies away from the central gravitating source with the increase in the values of Q . The stable circular orbits get closer to the central object as the parameters γ and α increases. Thus, one can observe the epicyclic frequencies closer to the central object and would be higher as compared to the epicyclic frequencies observed in the case of pure Riessner-Nordstrom black hole, i.e., without quintessence and string clouds. The redshift parameter z , of the photons emitted by the charged test particles moving in the stable circular orbits around the charged quintessential black hole with clouds of strings, increases with an increase in the values of the parameter α and decreases with an increase in the values of the charge Q of the black hole. For different values of the parameter γ , it stays constant. In the study of the Banados-Silk-West (BSW) process, in the spacetime geometry of the charged-Kiselev black hole with string cloud, we notice that the centre-of-mass energy at the horizon of the black hole increases indefinitely if the charge of one of the colliding particles attains its critical value. We observe that the effective force on the test particles decreases as the values of the parameters γ and α go on increasing, and it increases with the increasing values of the charge Q of the black hole. For a better understanding of the study, we show the dependence of the radii of the circular orbits, energy and angular momentum of the particles, effective potential, effective force, quasi-periodic oscillations and red-blue shifts of photons of the test particles in the circular orbits on the parameters α , γ and Q graphically. • We have examined the circular motion of test particles and photons for the spacetime with a charged black hole surrounded by quintessence and clouds of strings. • We observe that if the values of γ and α increase, the test particle can more easily escape the gravitational field of the black hole. • With the increasing values of Q , the stable circular orbits move away from the central black hole. • The epicyclic frequencies closer to the central object would be higher than the epicyclic frequencies observed in the case of the pure Riessner-Nordstrom black hole. • The redshift parameter z of the photons emitted by the charged test particles moving in the stable circular orbits around the black hole.

Inducing oscillations of trapped particles in a near-critical Gaussian field.

We study the nonequilibrium dynamics of two particles confined in two spatially separated harmonic potentials and linearly coupled to the same thermally fluctuating scalar field, a cartoon for optically trapped colloids in contact with a medium close to a continuous phase transition. When an external periodic driving is applied to one of these particles, a nonequilibrium periodic state is eventually reached in which their motion synchronizes thanks to the field-mediated effective interaction, a phenomenon already observed in experiments. We fully characterize the nonlinear response of the second particle as a function of the driving frequency, in particular far from the adiabatic regime in which the field can be assumed to relax instantaneously. We compare the perturbative, analytic solution to its adiabatic approximation, thus determining the limits of validity of the latter, and we qualitatively test our predictions against numerical simulations.

Chaotic rotation of a finite-size spheroidal particle in oscillating shear flows with fluid inertia

Rotational dynamics of a prolate spheroid in oscillating shear flows is studied by fully resolved direct numerical simulations with an immersed boundary method. In this flow configuration, we extend the work of Nilsen and Andersson [“Chaotic rotation of inertial spheroids in oscillating shear flow,” Phys. Fluids 25, 013303 (2013)] with focusing on the fluid inertia effect. We observe that the spheroid could rotate in chaotic and nonchaotic modes, which are identified by the sign of a largest Lyapunov exponent of the dynamic system. These two distinct rotation modes depend on both particle Reynolds number and oscillation frequency. For a certain Reynolds number, chaotic rotation appears when oscillation frequency is lower than a critical value, which decreases linearly with the increase of the particle Reynolds number. Based on this finding, we propose an empirical expression to predict the rotation mode. We, furthermore, discuss the mechanism of the emergence of the chaotic rotation, which is ascribed to a nonlinear interaction between time-varying orientation of the inertial spheroid and the oscillation of the shear rate.

Pulsar timing residual induced by wideband ultralight dark matter with spin 0,1,2

The coherent oscillation of ultralight dark matter in the mass regime around $10^{-23}$ eV induces changes in gravitational potential with the frequency in the nanohertz range. This effect is known to produce a monochromatic signal in the pulsar timing residuals. Here we discuss a multifield scenario that produces a wide spectrum of frequencies, such that the ultralight particle oscillation can mimic the pulsar timing signal of stochastic common spectrum process. We discuss how ultralight dark matter with various spins produces such a wide band spectrum on pulsar timing residuals and perform the Bayesian analysis to constrain the parameters. It turns out that the stochastic background detected by NANOGrav can be associated with a wideband ultralight dark matter.

Origin of oscillatory structures in the magnetothermal conductivity of the putative Kitaev magnet α-RuCl3

The layered honeycomb magnet α-RuCl3 has been suggested to exhibit a field-induced quantum spin liquid state, in which the reported large thermal Hall effect close to the half-quantized value still remains a subject of debate. Recently, oscillatory structures of the magnetothermal conductivity were reported and interpreted as quantum oscillations of charge-neutral particles. To investigate the origin of these oscillatory structures, we performed a comprehensive measurement of the in-plane magnetothermal conductivity κ(H) down to low temperature (100 mK), as well as magnetization M, for single crystals grown by two different techniques: Bridgman and chemical vapor transport. The results show a series of dips in κ(H) and peaks in the field derivative of M located at the same fields independent of the growth method. We argue that these structures originate from the field-induced phase transitions rather than from quantum oscillations. The positions of several of these features are temperature-dependent and connected to the magnetic phase transitions in zero field: the main transition at 7 K and weaker additional transitions, which likely arise from secondary phases at 10 K and 13 K. In contrast to what is expected for quantum oscillations, the magnitude of the structure in κ(H) is smaller for the higher conductivity crystal and decreases rapidly upon cooling below 1 K.