A study of grid failure mode drivers and methods for accelerated life testing of a 30cm diameter ion thruster

In view of the high cost caused by the 1:1 lifetime verification test of ion thrusters,the lifetime acceleration test should be considered.This work uses the PIC-MCC(Particle-in-Cell MonteCarlo Collision)method to analyze the five failure factors that lead to the failure of the accelerator grid of a 30 cm diameter ion thruster under the working mode of 5 k W.Meanwhile,the acceleration stress levels corresponding to different failure factors are obtained.The results show that background pressure has the highest stress level on the grid's erosion.The accelerator grid aperture's mass sputtering rate under the rated vacuum degree(1×10^(-4)Pa)of 5 k W work mode is 8.78 times that of the baseline vacuum degree(1×10^(-6)Pa),and the mass sputtering rate under worse vacuum degree(5×10^(-3)Pa)is 5.08 times that of 1×10^(-4)Pa.Under the influence of the other four failure factors,namely,the voltage of the accelerator grid,upstream plasma density,the screen grid voltage and mass utilization efficiency,the mass sputtering rates of the accelerator grid hole are 2.32,2.67,1.98 and 2.51 times those of the accelerator grid hole under baseline condition,respectively.The ion sputtering results of two 30 cm diameter ion thrusters(both installed with new grids assembly)after working for 1000 h show that the mass sputtering rate of the accelerator grid hole under vacuum conditions of 5×10^(-3)Pa is 4.54 times that under the condition of 1×10^(-4)Pa,and the comparison error between simulation results and test results of acceleration stress is about 10%.In the subsequent ion thruster lifetime verification,the working vacuum degree can be adjusted according to the acceleration stress level of background pressure,so as to shorten the test time and reduce the test cost.

A study of pulsed high voltage driven hollow-cathode electron beam sources through synchronous optical trigger

In this study,a pulsed,high voltage driven hollow-cathode electron beam sources through an optical trigger is designed with characteristics of simple structure,low cost,and easy triggering.To validate the new design,the characteristics of hollow-cathode discharge and electron beam characterization under pulsed high voltage drive are studied experimentally and discussed by discharge characteristics and analyses of waveform details,respectively.The validation experiments indicate that the pulsed high voltage supply significantly improves the frequency and stability of the discharge,which provides a new solution for the realization of a high-frequency,high-energy electron beam source.The peak current amplitude in the high-energy electron beam increases from 6.2 A to 79.6 A,which indicates the pulsed power mode significantly improves the electron beam performance.Besides,increasing the capacitance significantly affects the highcurrent,lower-energy electron beam more than the high-energy electron beam.

Supermassive Primordial Black Holes for Nano-Hertz Gravitational Waves and High-redshift JWST Galaxies

Recently,observational hints for supermassive black holes have been accumulating,prompting the question:Can primordial black holes(PBHs)be supermassive,particularly with masses M■10^(9)M_(⊙)?A supercritical bubble,containing an inflating baby universe,that nucleated during inflation can evolve into a PBH in our observable universe.We find that when the inflaton slowly transitions past a neighboring vacuum,the nucleation rate of supercritical bubbles inevitably peaks,leading to a mass distribution of multiverse PBHs with a peak mass up to M■10^(11)M_(⊙).Thus,our mechanism naturally provides a primordial origin for supermassive black holes.

Characteristics of the pressure profile in the accelerator on the RF negative ion source at ASIPP

Neutral beam injection(NBI)systems based on negative hydrogen ion sources-rather than the positive ion sources that have typically been used to date-will be used in the future magnetically confined nuclear fusion experiments to heat the plasma.The collisions between the fast negative ions and neutral background gas result in a significant number of high-energy positive ions being produced in the acceleration area,and for the high-power long-pulse operation of NBI systems,this acceleration of positive ions back to the ion source creates heat load and material sputtering on the source backplate.This difficulty cannot be ignored,with the neutral gas density in the acceleration region having a significant impact on the flux density of the backstreaming positive ions.In the work reported here,the pressure gradient in the acceleration region was estimated using an ionization gauge and a straightforward 1D computation,and it was found that once gas traveled through the acceleration region,the pressure dropped by nearly one order of magnitude,with the largest pressure drop occurring at the plasma grid.The computation also revealed that the pressure drop in the grid gaps was substantially smaller than that in the grid apertures.

Variational quantum simulation of thermal statistical states on a superconducting quantum processer

Quantum computers promise to solve finite-temperature properties of quantum many-body systems,which is generally challenging for classical computers due to high computational complexities.Here,we report experimental preparations of Gibbs states and excited states of Heisenberg X X and X X Z models by using a 5-qubit programmable superconducting processor.In the experiments,we apply a hybrid quantum–classical algorithm to generate finite temperature states with classical probability models and variational quantum circuits.We reveal that the Hamiltonians can be fully diagonalized with optimized quantum circuits,which enable us to prepare excited states at arbitrary energy density.We demonstrate that the approach has a self-verifying feature and can estimate fundamental thermal observables with a small statistical error.Based on numerical results,we further show that the time complexity of our approach scales polynomially in the number of qubits,revealing its potential in solving large-scale problems.

The pseudospectrum and spectrum(in)stability of quantum corrected Schwarzschild black hole

In this study,we investigate the pseudospectrum and spectrum(in)stability of quantum corrected Schwarzschild black hole.Methodologically,we use the hyperboloidal framework to cast the quasinormal mode(QNM)problem into an eigenvalue problem associated with a non-selfadjoint operator,and then the spectrum and pseudospectrum are depicted.Besides,the invariant subspace method is exploited to improve the computational efficiency for pseudospectrum.The investigation into the spectrum(in)stability entails two main aspects.On the one hand,we calculate the spectra of the quantum corrected black hole,then by the means of the migration ratio,the impact of the quantum correction effect on the Schwarzschild black hole has been studied.The results indicate that the so-called“migration ratio instability”will occur for small black holes with small angular momentum number l.In the eikonal limit,the migration ratios remain the same for each overtone.On the other hand,we study the spectrum(in)stability of the quantum corrected black hole by directly adding some particular perturbations into the effective potential,where perturbations are located at the event horizon and null infinity,respectively.There are two interesting observations under the same perturbation energy norm.First,perturbations at infinity are more capable of generating spectrum instability than those at the event horizon.Second,we find that the peak distribution can lead to the instability of QNM spectrum more efficiently than the average distribution.

Observations on spontaneous chiral symmetry breaking and the mass gap of QCD in finite volume

We present a lattice quantum chromodynamics(QCD)simulation with 2+1+1 flavor full QCD ensembles using near-physical quark masses and different spatial sizes L,at a~0.055 fm.The results show that the scalar and pesudoscalar 2-point correlator with a valence pion mass of approximately 230 MeV become degenerated at L≤1.0 fm,and such an observation suggests that the spontaneous chiral symmetry breaking disappears effectively at this point.At the same time,the mass gap between the nucleon and pion masses remains larger thanΛQCDin the entire L∈[0.2,0.7]fm range.

Model construction of soybean average diameter and hole parameters of seed-metering wheel based on DEM

To satisfy the demands of soybean precision sowing,this article starts with statistics of the physical parameters of soybean seeds in Heilongjiang province,China.The filling process of soybean seeds was analyzed,and the ratio relationship between the diameter,depth,chamfer length of seed-metering wheel’s holes and the mean diameter of soybean seeds was determined.EDEM was used to simulate seeding circumstances of hole seed-metering wheel with different holes’sizes.The hole diameter ratio,hole depth ratio,and chamfer length ratio were the test factors,while the percentage of single multiple and the empty seeds were test indexes.The triple quadratic regression orthogonal rotation combination test was designed,and the mathematical model between test indexes and test factors was established.Results showed that the influence of hole diameter ratio and hole depth ratio was significant(p<0.01)in the case of single,multiple and empty seed percentage while chamfer length ratio was only significant in single seed percentage compared to multiple and empty seeds percentage(p>0.05).The chamfer length ratio was 0.15,the hole diameter ratio was 1.63-1.73,the hole depth ratio was 0.81-1.20,the quality of seeding index was more than 90,and multiple and missing indexes were less than 6%and 4%,respectively.The soybean hole wheel seeding device was produced under the optimal parameter combination,to perform a comparative verification test with non-optimized parameters.The test showed anastomotic simulation results,verified the validity of the simulation.The seeding device after optimization expressed the best operating performance,which might satisfy the demands of soybean precision sowing.The study results can provide a theoretical reference for the optimization design of soybean seeding devices.

Gravidynamics,spinodynamics and electrodynamics within the framework of gravitational quantum field theory

By noticing the fact that the charged leptons and quarks in the standard model are chirality-based Dirac spinors since their weak interaction violates maximally parity symmetry though they behave as Dirac fermions in electromagnetic interaction,we show that such a chirality-based Dirac spinor possesses not only electric charge gauge symmetry U(1)but also inhomogeneous spin gauge symmetry WS(1,3)=SP(1,3)?W1,3,which reveals the nature of gravity and spacetime.The gravitational force and spin gauge force are governed by the gauge symmetries W1,3and SP(1,3),respectively,and a biframe spacetime with globally fiat Minkowski spacetime as base spacetime and locally fiat gravigauge spacetime as a fiber is described by the gravigauge field through emergent non-commutative geometry.The gauge-geometry duality and renormalizability in gravitational quantum field theory(GQFT)are carefully discussed.A detailed analysis and systematic investigation on gravidynamics and spinodynamics as well as electrodynamics are carried out within the framework of GQFT.A full discussion on the generalized Dirac equation and Maxwell equation as well as Einstein equation and spin gauge equation is made in biframe spacetime.New effects of gravidynamics as extension of general relativity are particularly analyzed.All dynamic equations of basic fields are demonstrated to preserve the spin gauge covariance and general coordinate covariance due to the spin gauge symmetry and emergent general linear group symmetry GL(1,3,R),so they hold naturally in any spinning reference frame and motional reference frame.

Critical scalarization and descalarization of black holes in a generalized scalar-tensor theory

We study the critical dynamics in scalarization and descalarization in the fully nonlinear dynamical evolution in the class of theories with a scalar field coupling with both Gauss-Bonnet(GB) invariant and Ricci scalar. We explore the manner in which the GB term triggers black hole(BH) scalarization. A typical type Ⅰ critical phenomenon is observed, in which an unstable critical solution emerges at the threshold and acts as an attractor in the dynamical scalarization. For the descalarization, we reveal that a marginally stable attractor exists at the threshold of the first-order phase transition in shedding off BH hair. This is a new type Ⅰ critical phenomenon in the BH phase transition. Implications of these findings are discussed from the perspective of thermodynamic properties and perturbations for static solutions. We examine the effect of scalar-Ricci coupling on the hyperbolicity in the fully nonlinear evolution and observe that such coupling can suppress the elliptic region and enlarge parameter space in computations.

Accuracy of numerical relativity waveforms with respect to space-based gravitational wave detectors

As with the laser interferometer gravitational-wave observatory(LIGO),the matched filtering technique will be critical to the data analysis of gravitational wave detection by space-based detectors,including LISA,Taiji and Tianqin.Waveform templates are the basis for such matched filtering techniques.To construct ready-to-use waveform templates,numerical relativity waveforms are a starting point.Therefore,the accuracy issue of numerical relativity waveforms is critically important.There are many investigations regarding this issue with respect to LIGO.But unfortunately there are few results on this issue with respect to space-based detectors.The current paper investigates this problem.Our results indicate that the existing numerical relativity waveforms are as accurate as 99%with respect to space-based detectors,including LISA,Taiji and Tianqin.Such an accuracy level is comparable to that with respect to LIGO.

Custodial symmetry violation in scalar extensions of the standard model

The new measurement of the W boson mass from the CDF collaboration shows a significant tension with the standard model prediction,which evidences violation of custodial symmetry in the scalar sector.We study the scalar extensions of the standard model,which can be categorized into two classes,the scalar sector with custodial symmetry(Georgi-Machacek model and its generalizations)and the scalar sector without custodial symmetry,and explore how these extensions fit to electroweak precision data and the new CDF mW.The favored oblique parameters originate from either the large mass splitting in the multiplet via the loop contribution or the large vacuum expectation value,which breaks custodial symmetry at the tree level.In particular,we find that O(100)GeV new particles are allowed in the scalar extension scenarios.

Newtonian limit of Einstein equation with a cosmological constant

Traditionally,the cosmological constant has been viewed as dark energy that mimics matter with negative energy.Given that matter with negative energy provides a repulsive force,which fundamentally differs from typical gravitational forces,it has been believed that the cosmological constant effectively contributes a repulsive force.However,it is important to note that the concept of gravitational force is valid only within the framework of Newtonian dynamics.In this study,we demonstrate that the traditional understanding of the gravitational force contributed by the cosmological constant is not entirely correct.Our approach involves investigating the Newtonian limit of the Einstein equation with a cosmological constant.The subtleties involved in this analysis are discussed in detail.Interestingly,we find that the effect of the cosmological constant on Newtonian gravity is an attractive force rather than a repulsive one for ordinary matter.As expected,this corrective force is negligibly small.However,our findings may offer a way to distinguish between dark energy and the cosmological constant,as one contributes a repulsive force while the other contributes an attractive force.

New signature of low mass Z'in J/ψdecays

We explored a new approach to search for a low-mass Z′particle through J/ψdecays by identifying its existence through parity-violating phenomena in the isospin-violating final states ofΛΣ¯^(0)and the corresponding charge conjugated states ofΛΣ¯^(0).Our investigation centered on a generation-independent and leptophobic Z′with mass below 10 GeV.Given the present experimental conditions at Beijing Spectrometer III(BESIII)and the anticipated opportunities at the Super Tau Charm Factory(STCF),we conducted Monte-Carlo simulations to predict possible events at both facilities.Notably,we foresee a substantial enhancement in the precision of the lower limit estimation ofαNP as well as a reduction in statistical uncertainty with upcoming STCF experiments.Furthermore,it is essential to highlight that a null result in the measurement ofαNP would impose stringent constraints,requiring the Z′−q−q couplings to be in the order of 10^(−2).

Gravitational waves and primordial black hole productions from gluodynamics by holography

Understanding the nature of quantum chromodynamics(QCD)matter is important but challenging due to the presence of nonperturbative dynamics under extreme conditions.We construct a holographic model describing the gluon sector of QCD at finite temperatures in the non-perturbative regime.The equation of state as a function of temperature is in good accordance with the lattice QCD data.Moreover,the Polyakov loop and the gluon condensation,which are proper order parameters to capture the deconfinement phase transition,also agree quantitatively well with the lattice QCD data.We obtain a strong first-order confinement/deconfinement phase transition at Tc=276.5 Me V that is consistent with the lattice QCD prediction.Based on our model for a pure gluon hidden sector,we compute the stochastic gravitational waves and primordial black hole(PBH)productions from this confinement/deconfinement phase transition in the early Universe.The resulting stochastic gravitational-wave backgrounds are found to be within detectability in the International Pulsar Timing Array and Square Kilometre Array in the near future when the associated productions of PBHs saturate the current observational bounds on the PBH abundances from the LIGO-Virgo-Collaboration O3 data.

Post-Newtonian binary dynamics in the effective field theory of Horndeskigravity

General relativity has been very successful since its proposal more than a century ago.However,various cosmological observations and theoretical consistency still motivate us to explore extended gravity theories.Horndeski gravity stands out as one attractive theory by introducing only one scalar field.Here we formulate the post-Newtonian effective field theory of Horndeski gravity and investigate the conservative dynamics of inspiral compact binary systems.We calculate the leading effective Lagrangian for a compact binary and obtain the periastron advance per period.In particular,we apply our analytical calculation to two binary systems,PSR B 1534+12 and PSR J0737-3039,and constrain the relevant model parameters.This theoretical framework can also be systematically extended to higherorders.

Gravitational wave search by time-scale-recursive denoising and matched filtering

In our previous work [Physical Review D,2024,109(4):043009],we introduced MSNRnet,a framework integrating deep learning and matched filtering methods for gravitational wave(GW) detection.Compared with end-to-end classification methods,MSNRnet is physically interpretable.Multiple denoising models and astrophysical discrimination models corresponding to different parameter space were operated independently for the template prediction and selection.But the MSNRnet has a lot of computational redundancy.In this study,we propose a new framework for template prediction,which significantly improves our previous method.The new framework consists of the recursive application of denoising models and waveform classification models,which solve the problem of computational redundancy.The waveform classification network categorizes the denoised output based on the signal's time scale.To enhance the denoising performance for long-time-scale data,we upgrade the denoising model by incorporating Transformer and ResNet modules.Furthermore,we introduce a novel training approach that allows for the simultaneous training of the denoising network and waveform classification network,eliminating the need for manual annotation of the waveform dataset required in our previous method.Real-data analysis results demonstrate that our new method decreases the false alarm rate by approximately 25%,boosts the detection rate by roughly 5%,and slashes the computational cost by around 90%.The new method holds potential for future application in online GW data processing.

Color-kinematics duality and dual conformal symmetry for a four-loop form factor in N=4 SYM

We obtain the integrand of full-color four-loop three-point form factor of the stress-tensor supermultiplet in N=4 SYM,based on the color-kinematics(CK)duality and generalized unitarity method.Our result not only manifests all dual Jacobi relations via CK duality but also contains 133 free parameters.This suggests the constructibility of the form factor at even higher loops via CK duality.We also find that the planar form factor has a hidden dual conformal symmetry in the lightlike limit of the operator momentum,which is checked up to four loops.

Symbology of Feynman integrals from twistor geometries

We study the symbology of planar Feynman integrals in dimensional regularization by considering geometric configurations in momentum twistor space corresponding to their leading singularities(LS). Cutting propagators in momentum twistor space amounts to intersecting lines associated with loop and external dual momenta, including the special line associated with the point at infinity, which breaks dual conformal symmetry. We show that cross-ratios of intersection points on these lines, especially those on the infinity line, naturally produce symbol letters for Feynman integrals in D = 4-2∈, which include and generalize their LS. At one loop, we obtain all symbol letters using intersection points from quadruple cuts for integrals up to pentagon kinematics with two massive corners, which agree perfectly with canonical differential equation(CDE) results. We then obtain all two-loop letters, for up to four-mass box and one-mass pentagon kinematics, by considering more intersections arising from two-loop cuts. Finally we comment on how cluster algebras appear from this construction, and importantly how we may extend the method to non-planar integrals.

Impacts of gravitational-wave background from supermassive black hole binaries on the detection of compact binaries by LISA

In the frequency band of the Laser Interferometer Space Antenna(LISA),extensive research has been conducted on the impact of foreground confusion noise generated by galactic binaries within the Milky Way Galaxy.Additionally,recent evidence of a stochastic signal,announced by the NANOGrav,EPTA,PPTA,CPTA,and InPTA,indicates that the stochastic gravitational-wave background(SGWB)generated by supermassive black hole binaries(SMBHBs)can contribute strong background noise within the LISA band.Given the presence of such strong noise,it is expected to have significant impacts on LISA's scientific missions.In this study,we investigate the impacts of the SGWB generated by SMBHBs on the detection of individual massive black hole binaries,verified galactic binaries,and extreme mass ratio inspirals in the context of LISA.We find it essential to resolve and eliminate the excess noise from the SGWB to guarantee the success of LISA's missions.