arXiv subjects

Yun-Long Zhang

Publications and source records attributed to Yun-Long Zhang.

At least 37 records · Page 2Linked to original sources

arXiv2026

Slowly rotating charges from Weyl double copy for Kerr black hole with Chern-Simons correction

The Weyl double copy builds the relation between gauge theory and gravity theory, especially the correspondence between gauge solutions and gravity solutions. In this paper, we obtain the slowly rotating charge solutions from Weyl double copy for the Kerr black hole with small Chern-Simons correction. Based on the Weyl double copy relation, for the Petrov type D solution, we find the additional correction to the electromagnetic field strength tensor of rotating charge. For the Petrov type I solution, we find that the additional electromagnetic field strength tensors have the exogenous properties, while the total sources vanish at the leading order.

gr-qc↗

arXiv2025

Detectability of dark matter density distribution via gravitational waves from binary black holes in the Galactic center

The fundamental nature of dark matter (DM) remains unknown, with significant uncertainties in its density profile. DM environments surrounding massive binary black holes (BBHs) modify their orbital dynamics, thereby altering gravitational wave (GW) emissions. For BBH systems at the Galactic Center, dynamical friction induced by DM spikes could produce detectable deviations in GW spectra, potentially observable by future space-based detectors. To address the uncertainties in the Galactic Center's DM profile, we systematically examine two scenarios: the generalized Navarro-Frenk-White (gNFW) profile and its post-spike modification. We investigate the evolutionary effects of DM dynamical friction and accretion on the eccentricity and semi-latus rectum of secondary black holes (BHs) in elliptical orbits. By constructing orbital models with varying initial eccentricities across the mass-semi-latus rectum parameter space and utilizing 30 years of simulated pulsar timing array data from the Square Kilometer Array (SKA), we identify detectable parameter regimes of DM effects and employ these GW observational signatures to constrain different DM density profiles. Our analysis reveals that among gNFW profiles ($γ=2,1.5,1,0.5$), only $γ=2$ produces significant detectable signatures. The formation of DM spikes further enhances these observable waveform deviations for all gNFW slopes.

astro-ph.HE↗

arXiv2025

Superradiant instability of area quantized Kerr black hole with discrete reflectivity

Ultralight bosons can condense to form the so-called bosonic clouds around spinning black holes by superradiance instability. When quantum effects are taken into account, the classical black holes were replaced by exotic compact objects including area quantized black holes. In this work, we consider the superradiant instabilities of massive scalar fields around area quantized Kerr black hole. We introduce the reflectivity of area quantized black hole possesses the distinct discrete feature, and the scalar fields have the superradiant modes solution only within the specific mass range. In addition, the area quantization may terminate the superradiance when the black hole spins down, or even suppress the formation of the bosionic cloud.

gr-qc↗

arXiv2025

Circularly Polarized Gravitational Wave Background Search with a Network of Space-borne Triangular Detectors

Circularly polarized gravitational wave backgrounds are predicted in many well-motivated models of inflation and phase transitions involving spontaneous parity violation. In this work, we investigate the detection of such parity-violating signals with the network of two space-borne triangular detectors. We derive the general analytical formula for the overlap reduction functions of networks composed of two triangular detectors, by exploiting the system's symmetrical properties under the long-wave approximation. Based on these results, we further assess the detectability of a parity-violating background with alternative LISA-Taiji network configurations. We find that the sensitivity to the parity-violating component can be significantly enhanced at low frequencies by adjusting the orientation of Taiji's constellation plane. This sensitivity gain is approximately an order of magnitude around the millihertz band, making the peak sensitivity comparable to that of the total intensity. This provides a promising opportunity to constrain various parity-violating theories in the millihertz band with upcoming space-borne detectors.

gr-qc↗

arXiv2025

Alternative LISA-TAIJI networks: Detectability of the Parity Violation in Stochastic Gravitational Wave Background

The detection of parity violation in the isotropic stochastic gravitational wave background (SGWB) will serve a crucial probe for new physics, particularly in parity-violating theories of gravity. The joint observations by the planned space-borne gravitational wave detectors, LISA and TAIJI, will offer a unique opportunity to observe such effects in the millihertz (mHz) band. This study evaluates the detectability of parity violation in the SGWB using two network configurations: LISA-TAIJIp and LISA-TAIJIm. The former configuration consists of LISA (inclined at $+60^\circ$ relative to the ecliptic plane) and TAIJIp (also inclined at $+60^\circ$), while the latter network pairs LISA with TAIJIm (inclined at $-60^\circ$). Our analysis demonstrates that the sensitivity of the LISA-TAIJIm network to parity violation in the SGWB is approximately one order of magnitude greater than that of the LISA-TAIJIp network at lower frequencies. To quantify the performance of the two networks, we evaluate the signal-to-noise ratios for different spectral shapes, including power-law, single-peak, and broken power-law models, and estimate parameter determination using the Fisher information matrix. The results confirm that LISA-TAIJIm outperforms LISA-TAIJIp in detecting the SGWB with circular polarization components, offering a superior opportunity to test parity-violating gravitational constraints on various mechanisms in the mHz band.

gr-qc↗

arXiv2025

Parameter extraction of the stochastic gravitational wave background with peak-like templates in millihertz

We investigate a framework for extracting parameters of stochastic gravitational wave background (SGWB) with peak-like templates in the millihertz frequency band, and analyzing transient contamination effects on parameter reconstruction. We present the spectrum and spectrogram under different conditions and provide the results of parameter reconstruction. Using templates from the early universe, we demonstrate that the peak-like templates outperform the broken power law (BPL) templates in power-law exponents recovery and peak frequency localization. The reconstruction results obtained using data from Fast Fourier Transform (FFT) are better than those obtained using data from Short-Time Fourier Transform (STFT) which is based on the spectrogram. For the single-peak template, the estimation accuracy of the exponent and peak frequency surpasses that of the BPL template by an order of magnitude, but demonstrates less precision in amplitude estimation compared to BPL. Regarding the double-peak template, parameter estimation results derived from the FFT methodology consistently outperform those obtained using STFT. Nevertheless, transient signals exhibit a detrimental impact on parameter estimation precision, causing errors to increase by an order of magnitude, particularly in multi-peak scenarios. This framework provides an example for using templates to analyze data from space-based gravitational wave detectors.

gr-qc↗

arXiv2025

Detectability of the chiral gravitational wave background from audible axions with the LISA-Taiji network

The chiral gravitational wave background (GWB) can be produced by axion-like fields in the early universe. We perform parameter estimation for two types of chiral GWB with the LISA-Taiji network: axion-dark photon coupling and axion-Nieh-Yan coupling. We estimate the spectral parameters of these two mechanisms induced by axion and determine the normalized model parameters using the Fisher information matrix. For highly chiral GWB signals that we choose to analyze in the mHz band, the normalized model parameters are constrained with a relative error less than $6.7\%$ (dark photon coupling) and $2.2\%$ (Nieh-Yan coupling) at the one-sigma confidence level. The circular polarization parameters are constrained with a relative error around $21\%$ (dark photon coupling) and $6.2\%$ (Nieh-Yan coupling) at the one-sigma confidence level.

astro-ph.CO↗

arXiv2024

DarkSHINE Baseline Design Report: Physics Prospects and Detector Technologies

DarkSHINE is a newly proposed fixed-target experiment initiative to search for the invisible decay of Dark Photon via missing energy/momentum signatures, based on the high repetition rate electron beam to be deployed/delivered by the Shanghai High repetition rate XFEL and Extreme light facility (SHINE). This report elaborates the baseline design of DarkSHINE experiment by introducing the physics goals, experimental setups, details of each sub-detector system technical designs, signal and backgground modelings, expected search sensitivities and future prospects, which mark an important step towards the further prototyping and technical demonstrations.

physics.ins-det↗

arXiv2023

Resonant Electric Probe to Axionic Dark Matter

The oscillating light axion field is known as wave dark matter. We propose an LC-resonance enhanced detection of the narrow band electric signals induced by the axion dark matter using a solenoid magnet facility. We provide full 3D electromagnetic simulation results for the signal electric field. The electric signal is enhanced by the high $Q$-factor of a resonant LC circuit and then amplified and detected by the state-of-the-art cryogenic electrical transport measurement technique. The cryogenic amplifier noise is the dominant noise source in the proposed detection system. We estimate that the detection system can have a promising sensitivity to axion dark matter with mass below $10^{-6}$ eV. The projected sensitivities improve with the size of the magnetic field, and the electric signal measurement can be potentially sensitive to the quantum chromodynamics (QCD) axion with $g_{aγ} \sim 10^{-16}$ GeV$^{-1}$ around $m_a \sim 10^{-8}$eV, with a multi-meter scale magnetized region. This limit is around five orders of magnitude below the current constraint from the cosmic rays.

hep-ph↗

arXiv2022

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.

astro-ph.CO↗

arXiv2022

Dark Fluxes from Accreting Black Holes and Direct Detections

We discuss the possibility that accreting black hole systems can be sources for dark matter flux through several different mechanisms. We firstly discuss two types of systems: coronal thermal plasmas around supermassive black holes in active galactic nuclei (AGNs), and accretion disks of stellar-mass X-ray black hole binaries (BHBs). We explore how these black hole systems may produce keV light dark matter fluxes and find that the dark fluxes from those sources might be too weak to account for the current XENON1T excess. On the other hand, black holes can be good accelerators to accrete and boost heavy dark matter particles. If considering collisions or dark electromagnetism, those particles can then escape and reach the benchmark speed of 0.1c at the detector. We also extend the black hole mass region to primordial black holes (PBHs) and discuss the possibility of contributing to keV light dark flux via superradiance of PBHs.

hep-ph↗

arXiv2021

A Weyl-$\mathrm{Z}_2$ semimetal from holography

We present effective field theories for the weakly coupled Weyl-$\mathrm{Z}_2$ semimetal, as well as the holographic realization for the strongly coupled case. In both cases, the anomalous systems have both the chiral anomaly and the $\mathrm{Z}_2$ anomaly and possess topological quantum phase transitions from the Weyl-$\mathrm{Z}_2$ semimetal phases to partly or fully topological trivial phases. We find that the topological phase transition is characterized by the anomalous transport parameters, i.e. the anomalous Hall conductivity and the $\mathrm{Z}_2$ anomalous Hall conductivity. These two parameters are nonzero at the Weyl-$\mathrm{Z}_2$ semimetal phase and vanish at the topologically trivial phases. In the holographic case, the different behavior between the two anomalous transport coefficients is discussed. Our work reveals the novel phase structure of strongly interacting Weyl-$\mathrm{Z}_2$ semimetal with two pairs of nodes.

hep-th↗

arXiv2021

Gravitational Waves and Possible Fast Radio Bursts from Axion Clumps

The axion objects such as axion mini-clusters and axion clouds around spinning black holes induce parametric resonances of electromagnetic waves through the axion-photon interaction. In particular, it has been known that the resonances from the axion with the mass around $10^{-6}$eV may explain the observed fast radio bursts (FRBs). Here we argue that similar bursts of high frequency gravitational waves, which we call the fast gravitational wave bursts (FGBs), are generated from axion clumps with the presence of gravitational Chern-Simons (CS) coupling. The typical frequency is half of the axion mass, which in general can range from kHz to GHz. We also discuss the secondary gravitational wave production associated with FRB, as well as the possible host objects of the axion clouds, such as primordial black holes with typical masses around $10^{-5}M_{\odot}$. Future detections of FGBs together with the observed FRBs are expected to provide more evidence for the axion.

hep-ph↗

arXiv2021

Notes on the Quantum Corrections of Swampland and Trans-Planckian Censorship Conjecture

We discuss the de Sitter swampland and trans-Planckian censorship conjectures (TCC) from the entropy bound with quantum corrections, namely quantum version of Bousso bound and energy conditions. We include the typical contributions from the entanglement entropy in quasi-de Sitter spacetime. The TCC is not much corrected, whereas the bounds on de Sitter swampland conjecture from energy conditions can be relaxed due to quantum corrections.

hep-th↗

arXiv2021

Observational Constraints on the Cosmology with Holographic Dark Fluid

We consider the holographic Friedman-Robertson-Walker (hFRW) universe on the 4-dimensional membrane embedded in the 5-dimensional bulk spacetime and fit the parameters with the observational data. In order to fully account for the phenomenology of this scenario, we consider the models with the brane cosmological constant and the negative bulk cosmological constant. The contribution from the bulk is represented as the holographic dark fluid on the membrane. We derive the universal modified Friedmann equation by including all of these effects in both braneworld and holographic cutoff approaches. For three specific models, namely, the pure hFRW model, the one with the brane cosmological constant, and the one with the negative bulk cosmological constant, we compare the model predictions with the observations. The parameters in the considered hFRW models are constrained with observational data. In particular, it is shown that the model with the brane cosmological constant can fit data as well as the standard $Λ$CDM universe. We also find that the $σ_8$ tension observed in different large-structure experiments can be effectively relaxed in this holographic scenario.

astro-ph.CO↗

arXiv2020

Comparison of proton shower developments in the BGO calorimeter of the Dark Matter Particle Explorer between GEANT4 and FLUKA simulations

The DArk Matter Particle Explorer (DAMPE) is a satellite-borne detector for high-energy cosmic rays and $γ$-rays. To fully understand the detector performance and obtain reliable physical results, extensive simulations of the detector are necessary. The simulations are particularly important for the data analysis of cosmic ray nuclei, which relies closely on the hadronic and nuclear interactions of particles in the detector material. Widely adopted simulation softwares include the GEANT4 and FLUKA, both of which have been implemented for the DAMPE simulation tool. Here we describe the simulation tool of DAMPE and compare the results of proton shower properties in the calorimeter from the two simulation softwares. Such a comparison gives an estimate of the most significant uncertainties of our proton spectral analysis.

physics.ins-det↗

arXiv2020

Correction Method for the Readout Saturation of the DAMPE Calorimeter

The DArk Matter Particle Explorer (DAMPE) is a space-borne high energy cosmic-ray and $γ$-ray detector which operates smoothly since the launch on December 17, 2015. The bismuth germanium oxide (BGO) calorimeter is one of the key sub-detectors of DAMPE used for energy measurement and electron proton identification. For events with total energy deposit higher than decades of TeV, the readouts of PMTs coupled on the BGO crystals would become saturated, which results in an underestimation of the energy measurement. Based on detailed simulations, we develop a correction method for the saturation effect according to the shower development topologies and energies measured by neighbouring BGO crystals. The verification with simulated and on-orbit events shows that this method can well reconstruct the energy deposit in the saturated BGO crystal.

physics.ins-det↗

arXiv2020

Universal Upper Bound on the Inflationary Energy Scale from the Trans-Planckian Censorship Conjecture

We study the constraint on the inflationary energy scale from the recently proposed Trans-Planckian Censorship Conjecture (TCC). We find a universal upper bound on the inflationary Hubble expansion rate $H_\text{inf}$ which is solely determined by the reheating temperature $T_\text{rh}$: $H_\text{inf}/M_\text{Pl}\lesssim T_0/T_\text{rh}$, where $T_0$ is the photon temperature today. The upper limit can be saturated by a post-inflationary oscillatory stage with the critical equation-of-state parameter $w\approx-1/3$, or by an inflation model with multiple stages. In the lowest reheating temperature required for big bang nucleosynthesis, the upper bound on the tensor-to-scalar ratio $r$ at the CMB scales is $r\lesssim10^{-8}$, which can be realized in many string-inspired inflation models.

astro-ph.CO↗