arXiv subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

At least 235 records · Page 13Linked to original sources

arXiv2024

Tests of the Kerr Hypothesis with MAXI J1803-298 Using Different RELXILL_NK Flavors

Iron line spectroscopy has been one of the leading methods not only for measuring the spins of accreting black holes but also for testing fundamental physics. Basing on such a method, we present an analysis of a dataset observed simultaneously by NuSTAR and NICER for the black hole binary candidate MAXI J1803-298, which shows prominent relativistic reflection features. Various relxill_nk flavors are utilized to test the Kerr black hole hypothesis. The results obtained from our analysis provide stringent constraints on Johannsen deformation parameter $α_{13}$ with the highest precise to date, namely $α_{13}=0.023^{+0.071}_{-0.038}$ from relxillD_nk and $α_{13}=0.006^{+0.045}_{-0.022}$ from relxillion_nk respectively in 3-$σ$ credible lever, where Johannsen metric reduces to Kerr metric when $α_{13}$ vanishes. Furthermore, we investigate the best model-fit results using Akaike Information Criterion and assess its systematic uncertainties.

astro-ph.HE↗

arXiv2024

Investigating the M1 radiative decay behaviors and the magnetic moments of the predicted triple-charm molecular-type pentaquarks

In this work, we systematically study the electromagnetic properties including the M1 radiative decay widths and the magnetic moments of the isoscalar $Ξ_{c c} D^{(*)}$, $Ξ_{cc}D_{1}$, and $Ξ_{cc}D_{2}^{*}$ triple-charm molecular-type pentaquark candidates, where we adopt the constituent quark model and consider both the $S$-$D$ wave mixing effect and the coupled channel effect. Our numerical results suggest that the M1 radiative decay widths and the magnetic moments of the isoscalar $Ξ_{c c} D^{(*)}$, $Ξ_{cc}D_{1}$, and $Ξ_{cc}D_{2}^{*}$ triple-charm molecular-type pentaquark candidates can reflect their inner structures, and the study of the electromagnetic properties is the important step to construct the family of the triple-charm molecular-type pentaquarks. With the accumulation of the experimental data during the high-luminosity phase of LHC, we expect that the present work combined with the corresponding mass spectrum information can encourage the experimental colleagues at LHCb to focus on the isoscalar $Ξ_{c c} D^{(*)}$, $Ξ_{cc}D_{1}$, and $Ξ_{cc}D_{2}^{*}$ triple-charm molecular-type pentaquark candidates.

hep-ph↗

arXiv2024

Structure of the $\mathbf{Λ(1670)}$ resonance

We examine the internal structure of the $Λ(1670)$ through an analysis of lattice QCD simulations and experimental data within Hamiltonian effective field theory. Two scenarios are presented. The first describes the $Λ(1670)$ as a bare three-quark basis state, which mixes with the $πΣ$, $\bar{K}N$, $ηΛ$ and $KΞ$ meson-baryon channels. In the second scenario, the $Λ(1670)$ is dynamically generated from these isospin-0 coupled channels. The $K^-p$ scattering data and the pole structures of the $Λ(1405)$ and the $Λ(1670)$ can be simultaneously described well in both scenarios. However, a comparison of the finite-volume spectra to lattice QCD calculations reveals significant differences between these scenarios, with a clear preference for the first case. Thus the lattice QCD results play a crucial role in allowing us to distinguish between these two scenarios for the internal structure of the $Λ(1670)$.

hep-ph↗

arXiv2024

Analysis of strong coupling constant with machine learning and its application

In this work, we investigate the nature of the strong coupling constant and related physics. Through the analysis of accumulated experimental data from around the world, we employ the ability of machine learning to unravel its physical laws. The result of our efforts is a formula that captures the expansive panorama of the distribution of the strong coupling constant across the entire energy range. Importantly, this newly derived expression is very similar to the formula derived from the Dyson-Schwinger equations based on the framework of Yang-Mills theory. By introducing the Euler number, $e$, into the functional formula of the strong coupling constant at high energies, we have successfully solved the puzzle of the infrared divergence, which allows for a seamless transition of the strong coupling constant from the perturbative to the non-perturbative energy regime. Moreover, the obtained ghost and gluon dressing function distribution results confirm that the obtained strong coupling constant formula can well describe the physical properties of the non-perturbed regime. In addition, we investigate the QCD strong coupling constant result of the Bjorken sum rule $Γ_1^{p-n}$ and the quark-quark static energy $E_0(r)$, and find that the global energy scale can effectively interpret the experimental data. The results presented in this work shed light on the puzzling properties of quantum chromodynamics and the intricate interplay of strong coupling constants at both low and high energy scales.

hep-ph↗

arXiv2024

Molecular-type $QQss\bar{s}$ pentaquarks predicted by an extended hidden gauge symmetry approach

In this work, we investigate the double-heavy molecular pentaquark states with the quark contents $ccss\bar{s}$, $bbss\bar{s}$, and $bcss\bar{s}$ by using the coupled channel approach. The extended local hidden gauge Lagrangians are used to obtain the meson-baryon interactions by exchanging the vector mesons. We predict some candidates for the molecular states with the quantum numbers $I(J^{P}) = 0(1/2^{-}, 3/2^{-}, 5/2^{-})$, whose binding energies are of the order of $20-30$ MeV and whose widths are all less than $8$ MeV. These predicted exotic double-heavy molecular pentaquark states may be accessible in future experiments such as LHCb.

hep-ph↗

arXiv2024

ParZC: Parametric Zero-Cost Proxies for Efficient NAS

Recent advancements in Zero-shot Neural Architecture Search (NAS) highlight the efficacy of zero-cost proxies in various NAS benchmarks. Several studies propose the automated design of zero-cost proxies to achieve SOTA performance but require tedious searching progress. Furthermore, we identify a critical issue with current zero-cost proxies: they aggregate node-wise zero-cost statistics without considering the fact that not all nodes in a neural network equally impact performance estimation. Our observations reveal that node-wise zero-cost statistics significantly vary in their contributions to performance, with each node exhibiting a degree of uncertainty. Based on this insight, we introduce a novel method called Parametric Zero-Cost Proxies (ParZC) framework to enhance the adaptability of zero-cost proxies through parameterization. To address the node indiscrimination, we propose a Mixer Architecture with Bayesian Network (MABN) to explore the node-wise zero-cost statistics and estimate node-specific uncertainty. Moreover, we propose DiffKendall as a loss function to directly optimize Kendall's Tau coefficient in a differentiable manner so that our ParZC can better handle the discrepancies in ranking architectures. Comprehensive experiments on NAS-Bench-101, 201, and NDS demonstrate the superiority of our proposed ParZC compared to existing zero-shot NAS methods. Additionally, we demonstrate the versatility and adaptability of ParZC by transferring it to the Vision Transformer search space.

cs.CV↗

arXiv2024

Surveying the mass spectra and the electromagnetic properties of the $Ξ_c^{(\prime,)} D^{()}$ molecular pentaquarks

Motivated by the observed $P_{ψs}^Λ(4459)/P_{ψs}^Λ(4338)$ and $T_{cc}(3875)^+$ states as the $Ξ_c \bar D^{*}/Ξ_c \bar D$ and $DD^{*}$ molecular candidates, respectively, in this work we investigate the $Ξ_c^{(\prime,*)} D^{(*)}$ molecular systems. We obtain the mass spectra and the corresponding spatial wave functions of the $Ξ_c^{(\prime,*)} D^{(*)}$-type double-charm molecular pentaquark candidates with single strangeness, where we utilise the one-boson-exchange model and take into account both the $S$-$D$ wave mixing effect and the coupled channel effect. Our results show that the most promising candidates of the double-charm molecular pentaquarks with single strangeness include the $Ξ_c D$ state with $I(J^P)=0(1/2^-)$, the $Ξ_c^{\prime} D$ state with $I(J^P)=0(1/2^-)$, the $Ξ_c D^{*}$ states with $I(J^P)=0(1/2^-,3/2^-)$, the $Ξ_c^{*} D$ state with $I(J^P)=0(3/2^-)$, the $Ξ_c^{\prime} D^{*}$ states with $I(J^P)=0(1/2^-,3/2^-)$, and the $Ξ_c^{*} D^{*}$ states with $I(J^P)=0(1/2^-,3/2^-,5/2^-)$. To gain further insight into the inner structures and the properties of the isoscalar $Ξ_c^{(\prime,*)} D^{(*)}$ molecular candidates, we utilize the constituent quark model to analyze their M1 radiative decay behaviors and magnetic moments based on the obtained mass spectra and spatial wave functions, which can offer the significant information to determine their spin-parity quantum numbers and configurations in the forthcoming experiments. We suggest that our experimental colleagues search for the predicted $Ξ_c^{(\prime,*)} D^{(*)}$ molecular states.

hep-ph↗

arXiv2024

Dynamically generated states from the $ηK^\bar{K}^$, $πK^\bar{K}^$, and $K K^\bar{K}^$ systems within the fixed-center approximation

The three-body systems $ηK^* \bar{K}^*$, $πK^* \bar{K}^*$, and $K K^* \bar{K}^*$ are further investigated within the framework of fixed-center approximation, where $K^* \bar{K}^*$ is treated as the fixed-center, corresponding to the possible scalar meson $a_0(1780)$ or the tensor meson $f_2'(1525)$. The interactions between $η$, $π$, $K$, and $K^*$ are taken from the chiral unitary approach. The resonance structures appear in the modulus squared of the three-body scattering amplitude and suggest that $η/ π/ K$-$(K^*\bar{K}^*)_{a_0(1780)/f'_2(1525)}$ hadron state can be formed. By scattering the $η$ meson on the fixed-center $(K^* \bar{K}^*)_{a_0(1780)}$, it is found that there is a distinct peak around 2100 MeV, as shown in the modulus squared of the three-body scattering amplitude, which can be associated with the meson $π(2070)$. For the scattering of the $η$ meson on the $(K^* \bar{K}^*)_{f_2'(1525)}$, a resonance structure around 1890 MeV is found and it can be associated with the $η_2(1870)$ meson. Other resonance structures are also found and can be associated with $π_2(1880)$ and $η(2010)$.

hep-ph↗

arXiv2024

TrajVis: a visual clinical decision support system to translate artificial intelligence trajectory models in the precision management of chronic kidney disease

Objective: Our objective is to develop and validate TrajVis, an interactive tool that assists clinicians in using artificial intelligence (AI) models to leverage patients' longitudinal electronic medical records (EMR) for personalized precision management of chronic disease progression. Methods: We first perform requirement analysis with clinicians and data scientists to determine the visual analytics tasks of the TrajVis system as well as its design and functionalities. A graph AI model for chronic kidney disease (CKD) trajectory inference named DEPOT is used for system development and demonstration. TrajVis is implemented as a full-stack web application with synthetic EMR data derived from the Atrium Health Wake Forest Baptist Translational Data Warehouse and the Indiana Network for Patient Care research database. A case study with a nephrologist and a user experience survey of clinicians and data scientists are conducted to evaluate the TrajVis system. Results: The TrajVis clinical information system is composed of four panels: the Patient View for demographic and clinical information, the Trajectory View to visualize the DEPOT-derived CKD trajectories in latent space, the Clinical Indicator View to elucidate longitudinal patterns of clinical features and interpret DEPOT predictions, and the Analysis View to demonstrate personal CKD progression trajectories. System evaluations suggest that TrajVis supports clinicians in summarizing clinical data, identifying individualized risk predictors, and visualizing patient disease progression trajectories, overcoming the barriers of AI implementation in healthcare. Conclusion: TrajVis bridges the gap between the fast-growing AI/ML modeling and the clinical use of such models for personalized and precision management of chronic diseases.

cs.HC↗

arXiv2024

Identifying a characterized energy level structure of higher charmonium well matched to the peak structures in $e^+e^-\to π^+ D^0 D^{*-}$

Recent advancements in charmoniumlike state have significantly enriched the discovery of new hadronic states, providing exciting opportunities for further investigations into the fascinating realm of charmonium physics. In this letter, we focus on the vector charmonium family and perform a detailed analysis of the recently observed $e^+e^-\to π^+ D^0 D^{*-}$ process. Our findings demonstrate a striking agreement between the observed peak structures and the predicted characterized energy level structure of higher vector charmonia including the $ψ(4220)$, $ψ(4380)$, $ψ(4415)$, and $ψ(4500)$, which are derived from an unquenched potential model. This discovery challenges conventional understanding of higher charmonia above 4 GeV and offers fresh insights into the dynamics of charm and anti-charm quarks in the formation of these states. Furthermore, the identification of these higher charmonia in the precisely measured $π^+ D^0D^{*-}$ open-charm decay channel would serve as compelling evidence supporting the unquenched scenario and contribute to a deeper understanding of the nonperturbative aspects of the strong interaction.

hep-ph↗

arXiv2024

Noise-Aware Speech Separation with Contrastive Learning

Recently, speech separation (SS) task has achieved remarkable progress driven by deep learning technique. However, it is still challenging to separate target speech from noisy mixture, as the neural model is vulnerable to assign background noise to each speaker. In this paper, we propose a noise-aware SS (NASS) method, which aims to improve the speech quality for separated signals under noisy conditions. Specifically, NASS views background noise as an additional output and predicts it along with other speakers in a mask-based manner. To effectively denoise, we introduce patch-wise contrastive learning (PCL) between noise and speaker representations from the decoder input and encoder output. PCL loss aims to minimize the mutual information between predicted noise and other speakers at multiple-patch level to suppress the noise information in separated signals. Experimental results show that NASS achieves 1 to 2dB SI-SNRi or SDRi over DPRNN and Sepformer on WHAM! and LibriMix noisy datasets, with less than 0.1M parameter increase.

cs.SD↗

arXiv2023

An Updated Lagrangian Particle Hydrodynamics (ULPH)-NOSBPD Coupling Approach for Modeling Fluid-Structure Interaction Problems

In order to solve the fluid-structure interaction problem of Newtonian fluid, a fluid-structure interaction approach is proposed based on Non-ordinary State-based Peridynamics (NOSB-PD) and Updated Lagrangian particle Hydrodynamics (ULPH), to simulate the fluid-structure interaction problem in which large geometric deformation and material failure are considered. In the coupled framework, the NOSB-PD theory is used to describe the deformation and fracture of the solid material structure. ULPH is applied to describe the flow of Newtonian fluids due to its advantages in computational accuracy. The framework effectively utilizes the advantages of NOSB-PD theory for solving discontinuous problems and ULPH theory for solving fluid problems and has good computational stability and robustness. To deal with the interface of fluid structure, a fluid-structure coupling algorithm using pressure as the transmission medium is established. The dynamic model of solid structure and the PD-ULPH fluid-structure interaction model involving large deformation are verified by several numerical validations, which are in good agreement with the analytical solution, the available experimental data and other numerical results, that demonstrates the accuracy and effectiveness of the proposed method in solving the fluid-structure interaction problem. Overall, the fluid-structure interaction model based on ULPH and NOSB-PD established in this paper provides a new idea for the numerical solution of fluid-structure interaction and a promising approach for engineering design and experimental prediction.

physics.flu-dyn↗

arXiv2023

An Updated Lagrangian particle hydrodynamics (ULPH) implementation of heat conduction model in weakly-compressive fluid

Heat conduction is quite common in natural, industrial, and military applications. In this work, the updated Lagrangian particle hydrodynamics (ULPH) theory, is utilized and applied to solve heat conduction problems. Since heat conduction is a second-order problem, the high-order ULPH theory is employed to establish the governing equations of heat conduction in ULPH, which is then validated using various numerical simulations. In this work, numerical simulations have been carried out to solve both static heat conduction problems and dynamic heat convection problems. The results show good accuracy and capability of the ULPH heat conduction model, suggesting promising prospects of the ULPH theory in multiphysics problems. The findings of this paper suggest that ULPH is effective in addressing convective heat transfer problems.

physics.flu-dyn↗

arXiv2023

Dissecting the Runtime Performance of the Training, Fine-tuning, and Inference of Large Language Models

Large Language Models (LLMs) have seen great advance in both academia and industry, and their popularity results in numerous open-source frameworks and techniques in accelerating LLM pre-training, fine-tuning, and inference. Training and deploying LLMs are expensive as it requires considerable computing resources and memory, hence many efficient approaches have been developed for improving system pipelines as well as operators. However, the runtime performance can vary significantly across hardware and software stacks, which makes it difficult to choose the best configuration. In this work, we aim to benchmark the performance from both macro and micro perspectives. First, we benchmark the end-to-end performance of pre-training, fine-tuning, and serving LLMs in different sizes , i.e., 7, 13, and 70 billion parameters (7B, 13B, and 70B) on three 8-GPU platforms with and without individual optimization techniques, including ZeRO, quantization, recomputation, FlashAttention. Then, we dive deeper to provide a detailed runtime analysis of the sub-modules, including computing and communication operators in LLMs. For end users, our benchmark and findings help better understand different optimization techniques, training and inference frameworks, together with hardware platforms in choosing configurations for deploying LLMs. For researchers, our in-depth module-wise analyses discover potential opportunities for future work to further optimize the runtime performance of LLMs.

cs.PF↗

arXiv2023

VLBI detection of the AE Aqr twin, LAMOST J024048.51+195226.9

LAMOST J024048.51+195226.9 (J0240+1952) was recently identified as the second AE Aquarii (AE Aqr)-type cataclysmic variable, possessing the fastest known rotating white dwarf. We performed a Very Long Baseline Interferometry (VLBI) observation of J0240+1952 utilizing the European VLBI Network at 1.7\,GHz, to obtain the first view of the radio morphology on mas scale. Our high-resolution VLBI image clearly shows that the radio emission is compact on mas scale ($\lesssim2$\,AU), with no evidence for a radio jet or extended emission. The compact radio source has an average flux density of $\sim0.37$\,mJy, and its brightness temperature is given at $\gtrsim2.3\times10^{7}$\,K, confirming a non-thermal origin. The emission exhibits irregular variations on a time-scale of tens of minutes, similar to the radio flares seen in AE Aqr. The measured VLBI position of J0240+1952 is consistent with that derived from \textit{Gaia}. Our results favour the model in which the radio emission is attributed to a superposition of synchrotron radiation from expanding magnetized blobs of this system.

astro-ph.SR↗

arXiv2023

Tribaryons with lattice QCD and one-boson exchange potentials

Motivated by the existence of two-body hadronic molecules composed of $ΩΩ$, $Ω_{ccc}Ω_{ccc}$ and $Ω_{bbb}Ω_{bbb}$ predicted by lattice QCD simulations, we use the Gaussian expansion method to investigate whether three-body systems composed of $ΩΩΩ$, $Ω_{ccc}Ω_{ccc}Ω_{ccc}$ and $Ω_{bbb}Ω_{bbb}Ω_{bbb}$ can bind with the two-body $^1S_0$ interactions provided by lattice QCD. Our results show that none of the three-body systems bind. On the other hand, we find that with the one-boson exchange potentials the $ΩΩΩ$ system develops a bound state, for which the $^5S_2$ interaction plays an important role. Our studies support the existence of the $\frac{3}{2}^+$ $ΩΩΩ$ bound state and the nonexistence of the $\frac{3}{2}^+$ $Ω_{ccc}Ω_{ccc}Ω_{ccc}$ and $Ω_{bbb}Ω_{bbb}Ω_{bbb}$ bound states, due to the suppressed $^5S_2$ interactions in heavier systems.

hep-ph↗

arXiv2023

Higher strangeonium decays into light flavor baryon pairs like $Λ\barΛ$, $Σ\barΣ$, and $Ξ\barΞ$

In this work, we investigate the decay behaviors of several higher strangeonia into $Λ\barΛ$ through a hadronic loop mechanism, enabling us to predict some physical observables, including the branching ratios. Furthermore, we assess the reliability of our research by successfully reproducing experimental data related to the cross section of $e^+e^-\toΛ\barΛ$ interactions. In this context, we account for the contributions arising from higher strangeonia, specifically $ϕ(4S)$ and $ϕ(3D)$. Additionally, we extend this study to encompass higher strangeonia decays into other light flavor baryon pairs, such as $Σ\barΣ$ and $Ξ\barΞ$. By employing the same mechanism, we aim to gain valuable insights into the decay processes involving these particles. By conducting this investigation, we hope to shed light on the intricate decay mechanisms of higher strangeonia and their interactions with various baryons pairs.

hep-ph↗

arXiv2023

Production of charmonium $χ_{cJ}(2P)$ plus one $ω$ meson by $e^+e^-$ annihilation

Inspired by the recent observation of $e^+e^-\to ωX(3872)$ by the BESIII Collaboration, in this work we study the production of the charmonium $χ_{cJ}(2P)$ by $e^+e^-$ annihilation. We find that the $e^+e^-\toωχ_{c0}(2P)$ and $e^+e^-\to ωχ_{c2}(2P)$ have sizable production rates, when taking the cross section data from $e^+e^-\to ωX(3872)$ as the scaling point and treating the $X(3872)$ as the charmonium $χ_{c1}(2P)$. Considering that the dominant decay modes of $χ_{c0}$ and $χ_{c2}(2P)$ involve $D\bar{D}$ final states, we propose that $e^+e^-\to ωD\bar{D}$ is an ideal process to identify $χ_{c0}(2P)$ and $χ_{c2}(2P)$, which is similar to the situation that happens in the $D\bar{D}$ invariant mass spectrum of the $γγ\to D\bar{D}$ and $B^+\to D^+{D}^- K^+$ processes. With continuous accumulation of experimental data, these proposed production processes offer a promising avenue for exploration by the BESIII and Belle II collaborations.

hep-ph↗