Bulk Oscillations Research Articles

Kaluza-Klein spectroscopy from neutron oscillations into hidden dimensions

Neutrons and neutrinos are natural probes for new physics. Since they carry no conserved gauge quantum numbers, both can easily mix with the fermions from hidden sectors. A particularly interesting effect is the oscillation of a neutron or a neutrino into a fermion propagating in large extra dimensions. In fact, such a mixing has been identified as the possible origin of small neutrino mass. In this paper, we study neutron oscillations into an extradimensional fermion and show that this effect provides a resonance imaging of the Kaluza-Klein tower. The remarkable feature of this phenomenon is its generic nature: because of a fine spacing of the Kaluza-Klein tower, neutrons at a variety of energy levels, both free or within nuclei, find a bulk oscillation partner. In particular, the partner can be a Kaluza-Klein mode of the same species that gives mass to the neutrino. The existence of bulk states matching the neutron energy levels of nuclear spectra gives rise to tight constraints as well as to potentially observable effects. For a free neutron, we predict recurrent resonant oscillations occurring with the values of the magnetic field correlated with the KK levels. We derive bounds on extra dimensions from ultracold neutron experiments and suggest signatures for refined measurements, which, in particular, can probe the parameter space motivated by the hierarchy problem. Ultracold neutron experiments offer a unique way of Kaluza-Klein spectroscopy. Published by the American Physical Society 2024

Energy harnessing and storage from surface switching with a ferroelectric electrolyte.

In the quest for innovative energy solutions suitable for mobile, stationary and digital applications, ferroelectric topological insulators (FETIs)1 emerge as promising candidates. These materials combine topologically protected states with spontaneous and switchable polarization. This study reveals emergent phenomena in FETI-electrolytes through experiments and simulations, specifically in the A3-2xBaxClO family (where A = Li, Na or K, and x = 0 or 0.005). Here, it is shown that surface oscillations of the potential (V), temperature, and mass may synchronize with the bulk's oscillations, and be harnessed and stored in the form of electrical energy either in a sole FETI or in a battery-type cell presenting a panoply of applications from wireless batteries to transistors, memories, sensors, and selective catalysts.

Stationary state of harmonic chains driven by boundary resetting

We study the nonequilibrium steady state of an ordered harmonic chain of N oscillators connected to two walls which undergo diffusive motion with stochastic resetting. The intermittent resetting of the walls effectively emulates two nonequilibrium reservoirs that exert temporally correlated forces on the boundary oscillators. These reservoirs are characterized by the diffusion constants and resetting rates of the walls. We find that, for any finite N, the velocity distribution of the bulk oscillators remains non-Gaussian, as evidenced by a non-zero bulk kurtosis that decays . We calculate the spatio-temporal correlation of the velocity of the oscillators both analytically as well as using numerical simulation. The signature of the boundary resetting is present at the bulk in terms of the two-time velocity correlation of a single oscillator and the equal-time spatial velocity correlation. For the resetting driven chain, the two-time velocity correlation decay as at the large time, and there exists a non-zero equal-time spatial velocity correlation when . A non-zero average energy current will flow through the system when the boundary walls reset to their initial positions at different rates. This average energy current can be computed exactly in the thermodynamic limit. Numerically we show that the distribution of the instantaneous energy current at the boundary is independent of the system size. However, the distribution of the instantaneous energy current in the bulk approaches a stationary distribution in the thermodynamic limit.

Systematic study of peak power scaling for an Yb-doped Kerr-lens mode-locked bulk oscillator

We study systematically and experimentally the peak power scalability of a femtosecond Yb:YAG bulk oscillator with separate Kerr and gain medium. We demonstrate that small resonator modifications result in a peak power increase from 93 to 424 kW, corresponding to a repetition rate decrease from 70 to 11 MHz while keeping the pulse duration mostly constant in the range of 90–100 fs. The results are of importance for designing and building up femtosecond oscillators for different applications requiring different repetition rates, such as multiphoton microscopy and ultra-broadband infrared radiation generation.

Kerr-lens mode-locked femtosecond Yb:CALYO oscillator with more than 20-W average power.

We report on the demonstration of a pure Kerr-lens mode-locked Yb:CALYO laser which can directly deliver sub-200 fs pulses with more than 20-W average power. With an incident pump power of 89 W, 153-fs pulses were generated with an average power of 21.5 W at a repetition rate of 77.9 MHz. The corresponding peak power and single pulse energy were 1.6 MW and 0.27 µJ, respectively. The stable operation of the mode-locking was confirmed by very small fluctuations in both spectrum and output power recorded over an hour. Second harmonic generation (SHG) was conducted with 59% conversion efficiency, which indicated that the high-power mode-locking pulses are of good quality. Stable Kerr-lens mode-locking (KLM) with 156-fs pulse duration and 27.2-W average power was also achieved with 109-W pump power. To the best of our knowledge, this is the highest average output power ever reported from a femtosecond mode-locked bulk oscillator.

High-power 50 fs Kerr-lens mode-locked Yb:CALGO oscillator

We report on a Kerr-lens mode-locked Yb:CALGO (Yb:CaGdAlO4) oscillator providing 50 fs pulses at 59.4 MHz repetition with an output power of 8.6 W that is pumped by a diode laser coupled to a multimode fiber. The mode-locking was initiated near the cavity stability edge of the CW mode, where the Kerr lensing at the gain crystal in the pulse mode reduces the cavity loss of the spatial mode and suppresses the CW mode build-up. The obtained pulse energy of 0.15 μJ and peak power of 2.5 MW from a simple laser cavity without saturable absorber, pumped by a conventional diode laser, are competitive in comparison to other Yb-doped bulk oscillators. An overview of previously demonstrated mode-locked oscillators reveals that the Yb:CALGO oscillator employing Kerr-lens mode-locking is a promising candidate to achieve ultrashort high-power pulses near 1040 nm.

Observation of grain boundary plasmon and associated deconvolution techniques for low-loss electron energy-loss (EEL) spectra acquired from grain boundaries

Spatially resolved valence electron energy-loss spectroscopy (VEELS) was used to acquire low-loss EEL spectra from Al grain boundaries (GBs) with different GB energies. The loss signal from the GB is highly delocalized and is mixed with the bulk loss, therefore requiring separation. Three different separation techniques, i.e., Fourier-log, Fourier-ratio deconvolution and direct subtraction, were employed to extract the GB response from the low-loss spectra and produced similar results. The GB response consists of a positive intensity peak from the excitation of GB plasmons (GBP) and a negative intensity begrenzungs (Bgs) peak from reduced scattering from bulk oscillations. Also, lower electron density at the GB reduces the inelastic scattering of the bulk plasmon. The intensity of GBP scattering and begrenzungs peak is found to increase toward the GBs, with maximum intensity when the electron probe is positioned on the GB, connecting the begrenzungs effect with the creation of a GBP.

17.8 fs broadband Kerr-lens mode-locked Yb:CALGO oscillator.

Pulses as short as 17.8 fs with a spectral bandwidth of 145 nm and central wavelength of 1118 nm have been generated from a Kerr-lens mode-locked Yb:CALGO oscillator. The oscillator operating at an average power of 26 mW and a repetition rate of 95.9 MHz is pumped by a cost-effective single-mode fiber coupled laser diode emitting 800 mW at 976 nm. The dispersion is compensated using a prism pair combined with broadband chirp mirrors. To the best of our knowledge, the pulse durations corresponding to approximately 4.8 optical cycle pulses are the shortest achieved durations through a Yb-doped bulk oscillator.

Non-Hermitian topology of one-dimensional spin-torque oscillator arrays

Magnetic systems have been extensively studied both from a fundamental physics perspective and as building blocks for a variety of applications. Their topological properties, in particular those of excitations, remain relatively unexplored due to their inherently dissipative nature. The recent introduction of non-Hermitian topological classifications opens up new opportunities for engineering topological phases in dissipative systems. Here, we propose a magnonic realization of a non-Hermitian topological system. A crucial ingredient of our proposal is the injection of spin current into the magnetic system, which alters and can even change the sign of terms describing dissipation. We show that the magnetic dynamics of an array of spin-torque oscillators can be mapped onto a non-Hermitian Su-Schrieffer-Heeger model exhibiting topologically protected edge states. Using exact diagonalization of the linearized dynamics and numerical solutions of the non-linear equations of motion, we find that a topological magnonic phase can be accessed by tuning the spin current injected into the array. In the topologically nontrivial regime, a single spin-torque oscillator on the edge of the array is driven into auto-oscillation and emits a microwave signal, while the bulk oscillators remain inactive. Our findings have practical utility for memory devices and spintronics neural networks relying on spin-torque oscillators as constituent units.

Dynamic self-tuning, flickering and shedding in buoyant droplet diffusion flames under acoustic excitation

We report the mechanism of acoustic-flame coupling for buoyant diffusion flame in droplets. The flame under acoustic excitation exhibits differential varicose and sinuous modes including partial extinction and pinch offs at certain shedding heights. Contrary to traditional buoyant flames, the diameter (d) regression of a droplet results in self-tuning of the instability modes with progression in burning times. In essence, we show that a droplet exhibits multi frequency response with advent of new oscillations modes at different points of the burning lifetime. The acoustic perturbations modulate the flame surface or heat release only at lower frequency bands by feeding energy into the natural vortical stability modes of a buoyant plume. Interestingly, we unearth that a flame is naturally unstable at all frequencies lower than g/d. Acoustic pumping at any such frequency (<g/d) corresponds to a unique convective length scale h such that fflame=g/h. We therefore establish that the flame exhibits multiple convective length scales throughout the burning cycle. We subsequently established that the shedding length scale of the droplet flame shortens by more than 25% with increase in acoustic pressure. We theoretically proved that using critical circulation argument, one can uniquely determine the shedding length scale at any acoustic loading. However, it is interesting to note that while the acoustic pressure amplitude is crucial for determining the convective length at which a flame rolls up, the frequency of excitation has no role to play. In other words, the velocity field introduced by the acoustic pressure is responsible for the shedding of the flame. The acoustic perturbations also lead to bulk oscillation of the flame surface near the forward stagnation zone. This is attributed to the acoustic induced velocity that leads to transient shifting of the stoichiometric surface.

Effect of Temperature on the Dynamic Properties of Mixed Surfactant Adsorbed Layers at the Water/Hexane Interface under Low-Gravity Conditions

An increase in temperature typically leads to a decrease in the interfacial tension of a water/oil interface. The addition of surfactants to the system can complicate the situation significantly, i.e., the interfacial tension can increase or decrease with an increasing temperature. For most concentrations of the two studied surfactants, the cationic tetradecyl trimethyl ammonium bromide (TTAB) and the nonionic tridecyl dimethyl phosphine oxide (C13DMPO), the measured interfacial tension of the aqueous mixed surfactant solutions against hexane increases when the temperature decreases between 30 °C and 20 °C. However, with a further temperature decrease between 20 °C and 15 °C, the reverse effect has also been observed at some concentrations, i.e., a decrease of interfacial tension. Additionally, the corresponding dilational interfacial visco-elasticity shows some discrepant temperature effects, depending on the bulk concentration and oscillation frequency. The experiments have been performed with a capillary pressure tensiometer under the conditions of micro-gravity. The reason for the positive and negative interfacial tension and visco-elasticity gradients, respectively, within certain ranges of the temperature, concentration and mixing ratios, are discussed on the basis of all available parameters, such as the solubility and partitioning of the surfactants in the two liquid phases and the oscillation frequency.

Detection of topology via entanglement oscillations

We introduce a characterization of topological order based on bulk oscillations of the entanglement entropy and the definition of an `entanglement gap', showing that it is generally applicable to pure and disordered quantum systems. Using exact diagonalization and the strong disorder renormalization group method, we demonstrate that this approach gives results in agreement with the use of traditional topological invariants, especially in cases where topological order is known to persist in the presence of off-diagonal bond disorder. The entanglement gap is then used to analyze classes of quantum systems with alternating bond types, allowing us to construct their topological phase diagrams. The validity of these phase diagrams is verified in limiting cases of dominant bond types, where the solution is known.

Yb:CALGO bulk oscillator generating ultrashort pulses at high efficiency by cross-polarized optical pumping

Yb:CALGO bulk oscillator generating ultrashort pulses at high efficiency by cross-polarized optical pumping

Finite element simulation of laser-generated surface acoustic wave for identification of subsurface defects

The characteristics of laser-generated ultrasonic wave with subsurface defects are investigated by finite element method (FEM). We used this method to model a subsurface hollow with a rectangular shape, which was used to represent a subsurface defect. The diffracted bulk modes and oscillation modes result from the interaction between R-waves (Rayleigh waves) and subsurface defects are analyzed in detail. The amplitude of RE-waves (Echo waves) and O-waves (oscillating waves) results from subsurface defects change when the depth of subsurface defects increases. The sources and mechanism of E-waves and O-waves were studied. The maximum amplitude of 1–2 MHz, 2–3 MHz and 3–4 MHz changed very obvious and performed oscillation characteristics, we can select the maximum amplitude of laser-generated ultrasonic wave at different frequency can be used to detect the size and location of subsurface defect. The proposed method may provide a useful way to detect other types of subsurface structures.

Fixed- and variable-frequency sliding mode controller–maximum power point tracking converter for two-stage grid-integrated photovoltaic system employing nonlinear loads with power quality improvement features

This article presents a reliable and efficient photovoltaic sliding mode voltage-controlled maximum power point tracking DC-DC converter–active power filter integration system to supply real power to grid. This integrated active power filter system performs power quality enhancement features to compensate current harmonics to make distortion-free grid supply current and reactive power employing nonlinear loads. The proposed proportional–integral–derivative–based sliding mode controller is designed with fixed-frequency pulse-width modulation based on equivalent control approach. The main objective of this paper is to design a photovoltaic system with a new sliding surface to force the photovoltaic voltage to follow the reference maximum power point voltage with the alleviation of slow transient response and disadvantages of chattering effects of variable-frequency hysteresis modulation sliding mode controller–maximum power point tracking. The perturbations caused by the uncertainties in climatic conditions and converter output bulk oscillations during grid integration are also mitigated. The features of the proposed photovoltaic–active power filter integration system are confirmed at different operating conditions through PSIM simulation software, and its performance is also compared with a conventional variable-frequency sliding mode-controlled maximum power point tracking. The obtained simulation and experimental results give good dynamic response under various operating conditions of environmental and local load conditions.

Experimental study on the characteristics of capillary surface waves on a liquid film on an ultrasonically vibrated substrate

In this paper, we report experimental results on the propagation speed, wavelength, and frequency of capillary surface waves induced by imposing ultrasonic vibration on the substrate of a few millimeter thick water film. It is common knowledge that imposing a low frequency vertical vibration (∼1–102 Hz) on a liquid body or layer results in bulk oscillation of the liquid and creation of standing surface waves with a frequency comparable to the excitation frequency (harmonic and subharmonic Faraday waves). Our experiments showed that the response of a liquid layer excited by horizontal and vertical ultrasonic frequency (20–68 kHz) is quite different, hypothetically because of a huge difference and mismatch between the characteristic times of vibration (small) and momentum diffusion (large) at high excitation frequencies. We observed that an excitation frequency of the order of 104 Hz results in the formation of traveling waves with frequencies of the order of 102 Hz, i.e. much smaller than the excitation frequency. In addition, we measured the speed of the Marangoni flow on the surface of a liquid film. We found that imposing ultrasonic vibration did not affect the speed of the Marangoni flow, corroborating that the ultrasonic vibration-induced traveling waves do not cause a bulk translational motion, and thus the flow on the surface is potential, whereas adjacent to the substrate a boundary layer forms. The studied problem is not only an intriguing fluid dynamics problem, it also has an existing application in the fabrication of thin coatings and solid films under ultrasonic excitation for emerging technologies, such as printed electronics and photovoltaics.

Turing-Hopf front invasion: Rings and shells

Invasion of Turing patterns into a region of bulk oscillations was investigated in the Belousov-Zhabotinsky-Aerosol OT reverse microemulsion system. Three distinct mechanisms for the formation of Turing structures at the expense of the bulk oscillation region were observed: frozen waves, which have been reported previously in this system, and reflecting waves and Turing-Hopf fronts, which have not. Turing-Hopf fronts appeared as the outer rings in this quasi-two-dimensional system with an amplitude intermediate between those of the Turing pattern and the phase waves in the bulk oscillation region. Three-dimensional (3D) Turing-Hopf shells (outer layers of 3D balls) were also observed.

A Porous Medium As an Acoustic Metamaterial with Negative Inertial and Elastic Properties

Abstract—The paper considers the effective inertial and elastic properties of a dispersive composite in the form of an elastic porous medium with empty spherical cavities. It is shown that when the translational vibrations and bulk oscillations of the cavities are in resonance, the dynamic density and compressibility of the porous medium take negative values. Estimates are presented for the internal dynamic parameters, for which the inertial and elastic properties determining the phase velocity and sound attenuation can simultaneously be negative in certain frequency ranges. The porous medium then assumes the properties of a metamaterial with negative sound refraction and other unique acoustic effects.

Birth and Death of Invading Standing Waves in the BZ‐AOT Reaction‐diffusion System

AbstractWe report our experimental observation of modulated standing waves that invade bulk oscillations exhibited by the Belousov‐Zhabotinsky‐Aerosol OT reverse microemulsion system. The modulated standing waves form within domains bounded by a traveling wave. We also observe that the modulated standing waves give way to traveling waves, which we connect to numerical simulations in a simple chemical model.

Kerr lens mode-locked Yb:CALGO thin-disk laser.

We demonstrate the first Kerr lens mode-locked Yb:CaGdAlO4 (Yb:CALGO) thin-disk laser oscillator. It generates pulses with a duration of 30fs at a central wavelength of 1048nm and a repetition rate of 124MHz. The laser emits the shortest pulses generated by a thin-disk laser oscillator, equal to the shortest pulse duration obtained by Yb-doped bulk oscillators. The average output power is currently limited to 150mW by the low gain and limited disk quality. We expect that more suitable Yb:CALGO disks will enable substantially higher power levels with similar pulse durations.