Angular Momentum Research Articles

Multi-band photometric study of the short period eclipsing binary ATO J007.0177+43.4841: physical properties and evolutionary status

We present a detailed photometric analysis of the newly identified binary system, ATOJ007.0177+43.4841, based on observations from the Kottamia Astronomical Observatory and the Zwicky Transient Facility. The system is classified as an A-type W UMa binary with a low mass ratio of q=0.182±0.001. A temperature difference of approximately 450 K between the components is observed, along with evidence of magnetic activity (manifested as the O’Connell effect) in the secondary star. This activity is attributed to a cool spot with a radius of 16 degrees and a temperature 30% lower than the surrounding region. The system’s geometry, characterized by an almost zero fill-out ratio, suggests that it is in a transient phase between detached and contact configurations, commonly referred to as shallow contact. This interpretation is further supported by an analysis of the system’s dynamical evolution and its thermal stability parameter, S=-0.02, indicating marginal stability. Additionally, the evolutionary status of the system is examined in the context of its position along the zero-age main sequence and terminal-age main sequence. The analysis suggests that the system’s evolution is primarily driven by angular momentum loss due to magnetic stellar wind and tidal coupling mechanisms.

Parameter constraints on a black hole with Minkowski core through quasiperiodic oscillations

We investigate the geodesic motion of charged particles in the vicinity of regular black holes with a Minkowski core, embedded in a uniform magnetic field, and study the influences of magnetic field and regular black hole parameter on the radial effective potential and angular momentum of the particles’ orbits. We perturb the circular orbit and analyze the characteristic frequencies of the epicyclic oscillations, which are closely related with the quasiperiodic oscillations (QPOs) phenomena of the accretion disc surrounding the black hole. Then using the MCMC simulation, we fit our theoretical results with four observational QPOs events (GRO J1655-40, XTE J1550-564, XTE J1859+226, and GRS 1915+105) and provide constraints on the magnetic field strength B, the characteristic radius r, the mass M, and the regular black hole parameter g. In particular, since the parameter g describes the degree of deviation from the classical Schwarzschild black hole, our studies suggest that, within a certain level of confidence, the black holes in the current model can deviate from the classical singularity structure of Schwarzschild black holes, and exhibit quantum corrections near the core.

Topological structure synthesized by three-dimensional spin angular momentum of light

Topological structure synthesized by three-dimensional spin angular momentum of light

Orbital angular momentum light interacted with double quantum dot-metal nanoparticle hybrid structure under spontaneous coherence

This work studies the generation of the orbital angular momentum (OAM) beam in the double quantum dot-metal nanoparticle (DQD-MNP) system under the application of the OAM beam. First, an analytical model is derived to attain the relations of probe and generated fields as a distance function in the DQD-MNP system under OAM applied field and spontaneously generated coherence (SGC) components. The calculation here is of material property; it differs from others by calculating energy states of the DQDs and the computation of the transition momenta between quantum dot (QD)-QD and QD-wetting layer (WL) transitions. The orthogonalized plane wave (OPW) calculates QD-WL transitions and their momenta. The momentum calculation is essential to specify the Rabi frequency of the input field. Such characteristics are not used in earlier models. The results show that SGC is vital in increasing the generated field. The signal field generated in the DQD-MNP system doubles that from the DQD system alone. So, the DQD-MNP system is preferred to the DQD system. The generated field in the DQD-MNP for the strong coupling DQD-MNP system is higher than that for the weak coupling. Increasing the distance separating the DQD-MNP reduces the generated field. Higher OAM number reduce the generated field at a long distance in the device. The model is then extended to study the effect of incoherent pumping () and the relations are modified to cover this part. The results show that reduces the generated field. While the results that compare the weak and strong coupling appear for the first, others compare well to the literature.

Attosecond Rescattering of Laser-Assisted Electron-Proton Collision in Coulomb Potential.

This study investigates the motion of an electron in a Coulomb potential driven by an intense linearly polarized XUV laser pulse analyzed using Gordon-Volkov wave functions. The wave function is decomposed into spherical partial waves to model the scattered electron wave packet after the recollision with a proton. This interaction triggers high harmonic generation, producing coherent X-ray pulses with frequencies that are integer multiples of the XUV field. The research presents a novel method for achieving atomic-scale resolution at nanometer and subfemtosecond levels, enabling observation of electron-proton collisions on an attosecond time scale. It emphasizes the coupling of fields that create resonances in the scattered electron through photon energy exchange with XUV and X-ray pulses, leading to the formation of a Rydberg electron with energy levels up to n = 27 and angular momentum components l = 13 and m = ± 1. The combination of XUV and high-frequency X-ray fields introduces new nonperturbative nonlinear phenomena characterized by differential cross sections derived using the Floquet-Lippmann-Schwinger equation in the first-order Born approximation. The analysis shows that backward-forward scattering involves XUV-electron energy exchange, with peak intensity along the laser polarization vector, while sideways scattering, dominated by X-ray-electron interaction, peaks perpendicular to the polarization. Additionally, the laser-assisted scattering process results in temporary electron capture in a dressed proton-bound state, followed by escape and ejection, with the free electron ponderomotive energy exceeding 10Up.

Measurement-device-independent quantum secure direct communication based on quantum cover channel and multiple degrees of freedom of hyperentanglement

Abstract Quantum secure direct communication (QSDC) achieves direct and secure transmission of information which does not need a pre-shared key. To improve the practical reliability of QSDC systems, Measurement-device-independent quantum secure direct communication protocol (MDI-QSDC) have emerged, which provide a more secure communication method by eliminating the dependence on measurement devices. This paper proposes an MDI-QSDC protocol based on polarization-spatial-orbital angular momentum mode hyperentanglement and quantum covert channel (QCC). This protocol can transmit 6-bit information in one round of communication, eliminating security vulnerability and information leakage associated with measurement devices. Compared with the previous MDI-QSDC protocols, this paper further clarifies the enhancement of channel capacity and security through numerical simulation studies. Further, the protocol introduces imperceptible QCC on polarization-spatial mode, which is significantly more secure than direct coding on polarization-spatial mode only. Based on the above features, the potential of the proposed high-capacity MDI-QSDC protocol in quantum communication is highlighted.

Hot Jupiters Are Asynchronous Rotators

Abstract Hot Jupiters are typically assumed to be synchronously rotating, from tidal locking. Their thermally driven atmospheric winds experience Lorentz drag on the planetary magnetic field anchored at depth. We find that the magnetic torque does not integrate to zero over the entire atmosphere. The resulting angular momentum feedback on the bulk interior can thus drive the planet away from synchronous rotation. Using a toy tidal–ohmic model and atmospheric general circulation model outputs for HD189733b, HD209458b, and Kepler7b, we establish that off-synchronous rotation can be substantial at tidal–ohmic equilibrium for sufficiently hot and/or magnetized hot Jupiters. Potential consequences of asynchronous rotation for hot Jupiter phenomenology motivate follow-up work on the tidal–ohmic scenario with approaches that go beyond our toy model.

Versatile manipulation of orbital angular momentum combs enabled by diffractive neural networks

Versatile manipulation of orbital angular momentum combs enabled by diffractive neural networks

Thermal Profile of Accretion Disk Around Black Hole in 4D Einstein–Gauss–Bonnet Gravity

In this study, we investigate the properties of a thin accretion disk around a static spherically symmetric black hole in 4D Einstein–Gauss–Bonnet gravity, with an additional coupling constant, α, appearing in the spacetime metric. Using the Novikov–Thorne accretion disk model, we examine the thermal properties of the disk, finding that increasing α reduces the energy, angular momentum, and effective potential of a test particle orbiting the black hole. We demonstrate that α can mimic the spin of a Kerr black hole in general relativity up to a≃ 0.23 M for the maximum value of α. Our analysis of the thermal radiation flux shows that larger α values increase the flux and shift its maximum towards the central black hole, while far from the black hole, the solution recovers the Schwarzschild limit. The impact of α on the radiative efficiency of the disk is weak but can slightly alter it. Assuming black-body radiation, we observe that the disk’s temperature peaks near its inner edge and is higher for larger α values. Lastly, the electromagnetic spectra reveal that the disk’s luminosity is lower in Einstein–Gauss–Bonnet gravity compared to general relativity, with the peak luminosity shifting toward higher frequencies, corresponding to the soft X-ray band as α increases.

Circular motion and chaos-bound violation for dyonic global monopole spacetime surrounded by a perfect fluid

In this paper, we investigate the circular motion and chaotic behavior of charged particles in the dyonic global monopole spacetime surrounded by a perfect fluid. We classified the black hole into three special regimes: dark matter, dust, and radiation. We precisely calculated the Lyapunov exponent for each regime as an eigenvalue of the Jacobian matrix. We examine, through numerical and graphical analysis, the circular motion and chaos bound violation across all the regimes. In the dark matter regime, stable orbits conform to the chaos bound. Even though the bound brings orbits with small charges and those far from the event horizon closer, they never violate it. In the dust regime, there can be more than one orbit for a fixed mass, charge, topological defect, and fluid parameter, especially when the angular momentum is small. At this point, the orbits are unstable, and those that are closer to the event horizon violate the bound. Similarly, in the radiation regime, orbits that are closer to the event horizon are unstable and chaotic, especially with greater angular momentum. In fact, regardless of the charge, topological defect, and fluid parameter, all orbits, whether they are far from or close to the horizon, become unstable and violate the bound when the angular momentum is significantly large.

Driving Rotational Circulation in a Microfluidic Chamber Using Dual Focused Surface-Acoustic-Wave Beams

In this paper, enhanced rotational circulation in a circular microfluidic chamber driven by dual focused surface-acoustic-wave (SAW) beams is presented. To characterize the resonant frequency and focusing effect, we simulate the focused SAW field excited by an arc-shaped interdigital transducer patterned on a 128°Y-cut lithium-niobate (LiNbO3) substrate using a finite element method. A full three-dimensional perturbation model of the combined system of the microfluidic chamber and the SAW device is conducted to obtain the acoustic pressure and acoustic streaming fields, which show rotational acoustic pressure and encircling streaming resulted in the chamber. Accordingly, the SAW acoustofluidic system is realized using microfabrication techniques and applied to perform acoustophoresis experiments on submicron particles suspending in the microfluidic chamber. The result verifies the rotational circulation motion of the streaming flow, which is attributed to enhanced angular momentum flux injection and Eckart streaming effect through the dual focused SAW beams. Our results should be of importance in driving particle circulation and enhancing mass transfer in chamber embedded microfluidic channels, which may have promising applications in accelerating bioparticle or cell reactions and fusion, enhancing biochemical and electrochemical sensing, and efficient microfluidic mixing.

Giant Vortex Dichroism in Simplified-Chiral-Double-Elliptical Metamaterials

Vortex dichroism in chiral metamaterials is of great significance to the study of photoelectric detection, optical communication, and the interaction between light and matter. Here we propose a compact chiral metamaterials structure composed of two elliptical SiO2 rods covered with a Au film on a substrate to achieve a significant vortex-dichroism effect. Such a structure has different responses to a Laguerre-Gaussian beam carrying opposite-orbital angular momentum, resulting in giant vortex dichroism. The influences of various structural parameters are analyzed, and the optimal parameters are obtained to realize a remarkable vortex dichroism of about 58.5%. The simplicity and giant VD effect of the proposed metamaterials make it a promising candidate for advancing chiral optical applications such as optical communication and sensing.

Re-revealing dark-field scanning imaging via modal decomposition of bright-field light in the OAM domain

An alternative dark-field (DF) scanning imaging is re-revealed via modal decomposition of the bright-field (BF) light in the orbital angular momentum (OAM) domain. A Gaussian beam containing only the zeroth-order OAM mode illuminates the surface. The BF light scattered from the surface carries the phase shift induced by the surface feature and then diffracts into a distorted light field, which is a coherent sum of the different OAM modes. The amplitude weight and inter-modal phase of each mode are obtained by modal decomposition. As the surface is scanned transversely, the DF image contrast results from either the square amplitude or the inter-modal phase at the nonzero orders of OAM modes. The results verified that the first-order OAM mode produces a DF image with the highest contrast for the high-spatial-frequency surface features. The inter-modal phase DF image is less sensitive to the rough surface than the square amplitude DF image, thus producing a cleaner DF background. The square amplitude DF image is more advantageous in observing high-spatial-frequency surface features. The proposed DF scanning imaging in the OAM domain provides an additional degree of freedom for surface characterization.

Appearance of the hindrance to complete fusion in heavy-ion collisions

The small cross-section of the synthesis of the superheavy elements (SHEs) is caused by the hindrance to complete fusion and small survival probability of the compound nucleus against fission. The hindrance to complete fusion is related with such peculiarities of the entrance channel as the mutual orientation angles of the axial symmetry of the colliding deformed nuclei, their mass (charge) asymmetry, the shell effects in their microscopic structure and orbital angular momentum. The appearance of the hindrance to complete fusion has been analyzed in the framework of the dinuclear system (DNS) model by the description of the experimental data obtained in the reactions of the SHE synthesis.

A Pride of Satellites in the Constellation Leo? Discovery of the Leo VI Milky Way Satellite Ultra-faint Dwarf Galaxy with DELVE Early Data Release 3

Abstract We report the discovery and spectroscopic confirmation of an ultra-faint Milky Way satellite in the constellation of Leo. This system was discovered as a spatial overdensity of resolved stars observed with Dark Energy Camera (DECam) data from an early version of the third data release of the DECam Local Volume Exploration (or DELVE) survey. The low luminosity ( M V = − 3.5 6 − 0.37 + 0.47 ; L V = 230 0 − 700 + 1200 L ⊙ ), large size ( R 1 / 2 = 9 0 − 30 + 30 pc), and large heliocentric distance ( D = 11 1 − 6 + 9 kpc) are all consistent with the population of ultra-faint dwarf galaxies (UFDs). Using Keck/DEIMOS observations of the system, we were able to spectroscopically confirm nine member stars, while measuring a tentative mass-to-light ratio of 70 0 − 500 + 1400 M ⊙ / L ⊙ and a nonzero metallicity dispersion of σ [ Fe / H ] = 0.1 9 − 0.11 + 0.14 , further confirming Leo VI’s identity as a UFD. While the system has a highly elliptical shape, ϵ = 0.5 4 − 0.29 + 0.19 , we do not find any conclusive evidence that it is tidally disrupting. Moreover, despite the apparent on-sky proximity of Leo VI to members of the proposed Crater-Leo infall group, its smaller heliocentric distance and inconsistent position in energy–angular momentum space make it unlikely that Leo VI is part of the proposed infall group.

Angular Momentum Superposition Beams‐Based Interferometer

AbstractOrbital‐angular‐momentum (OAM) beams‐based interferometer has been found various applications in high‐precision metrology. However, most of its applications reported to date are limited to 1D ones, and the simultaneous measurements for multidimensional displacement have rarely been explored. Here an angular momentum superposition beams‐based interferometer is first proposed and demonstrated, in which the phases‐changes induced by rotational and linear displacements, are independently carried by an angular momentum superposition (SOAMS) beam containing different spin and orbital angular momenta, and thus can be simultaneously detected. In accordance with the proposed interferometry, a new phase‐demodulation method is experimentally demonstrated, which is operated in the domain of the OAM complex spectrum and thus enables accurate yet high efficient extraction of the phase‐change information from the captured OAM interferograms. As typical results, rotational and linear displacements are simultaneously and accurately measured with accuracies of 2.89° and 16.04 nm, respectively. The proposed interferometry and the corresponding phase demodulation method may open a new way to realize the OAM beams‐based multidimensional metrology.

Magnetic nutation: Transient separation of magnetization from its angular momentum

Magnetic nutation: Transient separation of magnetization from its angular momentum

An orbital angular momentum incorporated UWOC system employing WMZCC and DPS codes under pure sea, clear ocean and coastal sea

An orbital angular momentum incorporated UWOC system employing WMZCC and DPS codes under pure sea, clear ocean and coastal sea

Graviton number radiated during binary inspiral and its link to angular momentum radiation

Graviton number radiated during binary inspiral and its link to angular momentum radiation

Plantar sensation associates with gait instability in older adults

BackgroundAdvanced age brings a loss of plantar sensation, represented, for example, as higher sensation thresholds in standardized testing. This is thought to contribute to an increased risk of falls among older adults – an intuitive premise that has yet to be fully investigated, especially in the context of walking balance. The purpose of this study was to quantify the association between plantar sensation and the instability elicited by a suite of walking balance perturbations that differ in direction and context in a cohort of n = 28 older adults (73.0 ± 5.9 yrs).MethodsWe measured plantar sensation using Semmes-Weinstein monofilaments and quantified margins of stability (MoS) and whole-body angular momentum (WBAM) during habitual walking and in response to optical flow perturbations, lateral waist-pull perturbations, and treadmill-induced slips.ResultsOur two major results were that higher monofilament thresholds (i.e., worse plantar sensation) in older adults associated with: (1) larger anterior-posterior (AP) and mediolateral (ML) MoS and increased transverse plane WBAM (p ≤ 0.031) during habitual walking, and (2) larger decreases in MoSAP, MoSML and larger increases in transverse plane WBAM in response to lateral waist pull perturbations (p ≤ 0.018). We found no associations between plantar sensation and responses to other perturbation contexts.ConclusionsWe conclude that there is an association between worse plantar sensation and gait instability, both during habitual unperturbed walking and in response to some perturbation contexts. These results should build confidence that interventions designed to improve plantar sensation for older adults, possibly through insoles or footwear modifications, could be critical for reducing gait-related falls in at-risk populations.