arXiv subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

At least 253 records · Page 14Linked to original sources

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↗

arXiv2023

Angular distribution of the FCNC process $B_{c}\to{D}_{s}^{*}(\to{D}_{s}π)\ell^{+}\ell^{-}$

In this work, we study the flavor-changing neutral-current process $B_{c}\to{D}_{s}^{*}(\to{D}_{s}π)\ell^{+}\ell^{-}$ ($\ell$= $e$, $μ$, $τ$). The relevant weak transition form factors are obtained by using the covariant light-front quark model, in which, the main inputs, i.e., the meson wave functions of $B_{c}$ and $D_{s}^{*}$, are adopted as the numerical wave functions from the solution of the Schrödinger equation with the modified Godfrey-Isgur model. With the obtained form factors, we further investigate the relevant branching fractions and their ratios, and some angular observables, i.e., the forward-backward asymmetry $A_{FB}$, the polarization fractions $F_{L(T)}$, and the $CP$-averaged angular coefficients $S_{i}$ and the $CP$ asymmetry coefficients $A_{i}$. We also present our results of the clean angular observables $P_{1,2,3}$ and $P^{\prime}_{4,5,6,8}$, which can reduce the uncertainties from the form factors. Our results show that the corresponding branching fractions of the electron or muon channels can reach up to $10^{-8}$. With more data being accumulated in the LHCb experiment, our results are helpful for exploring this process, and deepen our understanding of the physics around the $b\to{s}\ell^{+}\ell^{-}$ process.

hep-ph↗

arXiv2023

Multi-band Cross-correlated Radio Variability of the Blazar 3C 279

We present the results of our study of cross-correlations between long-term multi-band observations of the radio variability of the blazar 3C 279. More than a decade (2008-2022) of radio data were collected at seven different frequencies ranging from 2 GHz to 230 GHz. The multi-band radio light curves show variations in flux, with the prominent flare features appearing first at higher-frequency and later in lower-frequency bands. This behavior is quantified by cross-correlation analysis, which finds that the emission at lower-frequency bands lags that at higher-frequency bands. Lag versus frequency plots are well fit by straight lines with negative slope, typically ~-30 day/GHz. We discuss these flux variations in conjunction with the evolution of bright moving knots seen in multi-epoch VLBA maps to suggest possible physical changes in the jet that can explain the observational results. Some of the variations are consistent with the predictions of shock models, while others are better explained by a changing Doppler beaming factor as the knot trajectory bends slightly, given a small viewing angle to the jet.

astro-ph.HE↗

arXiv2023

Braids and linked periodic orbits of disc homeomorphisms

This paper concerns on linked periodic orbits of orientation-preserving homeomorphisms of the $2$-disc in the sense of Gambaudo. We interpret the linking of periodic orbits by using their induced braids. Then based on the forcing relation of braids, we present a method for finding periodic orbits which are linked with a given one. In particular, for $3$-periodic orbits of pseudo-Anosov braid types, we provide new examples of linked orbits of periods at most $4$.

math.DS↗

arXiv2023

New type of doubly charmed molecular pentaquarks containing most strange quarks: Mass spectra, radiative decays, and magnetic moments

In this work, we first predict the mass spectra of the $Ω_{c}^{(*)}{D}_s^{(*)}$-type doubly charmed molecular pentaquark candidates, where the one-boson-exchange model is adopted by considering both the $S$-$D$ wave mixing effect and the coupled channel effect. Our findings indicate that the $Ω_{c}{D}_s^*$ state with $J^P={1}/{2}^{-}$, the $Ω_{c}^*{D}_s^*$ state with $J^P={1}/{2}^{-}$, and the $Ω_{c}^*{D}_s^*$ state with $J^P={3}/{2}^{-}$ can be considered as the most promising doubly charmed molecular pentaquark candidates, and the $Ω_{c}{D}_s$ state with $J^P={1}/{2}^{-}$, the $Ω_{c}^*{D}_s$ state with $J^P={3}/{2}^{-}$, and the $Ω_{c}{D}_s^*$ state with $J^P={3}/{2}^{-}$ are the possible doubly charmed molecular pentaquark candidates. Furthermore, we further explore the radiative decays and the magnetic moments of the most promising doubly charmed molecular pentaquark candidates in the constituent quark model. As a crucial aspect of spectroscopy, the information of the radiative decays and the magnetic moments can provide the valuable clues to reflect their inner structures. With the accumulation of higher statistical data at the Large Hadron Collider, we propose that the LHCb Collaboration should focus on the problem of searching for these predicted doubly charmed molecular pentaquark candidates containing most strange quarks in the coming years.

hep-ph↗

arXiv2023

Spectroscopic survey of higher-lying states of $B_c$ meson family

In this work, we investigate the spectroscopy of higher $B_c$ mesons, with a special focus on the consideration of the unquenched effects. To account for such effects, we employ the modified Godfrey-Isgur model and introduce a screening potential. The resulting mass spectrum of the concerned higher $B_c$ states is then presented, showing significant deviations after considering the unquenched effects. This emphasizes the importance of considering the unquenched effects when studying of the higher $B_c$ mesons. Furthermore, we determine the corresponding spatial wave functions of these $B_c$ mesons, which have practical applications in subsequent studies of their decays. These decays include two-body Okuba-Zweig-Iizuka allowed strong decays, dipion transitions between $B_c$ mesons, radiative decays, and some typical weak decays. With the ongoing high-luminosity upgrade of the Large Hadron Collider, we expect the discovery of additional $B_c$ states in the near future. The knowledge gained from the mass spectrum and the different decay modes will undoubtedly provide valuable insights for future experimental explorations of these higher $B_c$ mesons.

hep-ph↗

arXiv2023

Precessing jet nozzle connecting to a spinning black hole in M87

The nearby radio galaxy M87 offers a unique opportunity to explore the connections between the central supermassive black hole and relativistic jets. Previous studies of the inner region of M87 revealed a wide opening angle for the jet originating near the black hole. The Event Horizon Telescope resolved the central radio source and found an asymmetric ring structure consistent with expectations from General Relativity. With a baseline of 17 years of observations, there was a shift in the jet's transverse position, possibly arising from an eight to ten-year quasi-periodicity. However, the origin of this sideways shift remains unclear. Here we report an analysis of radio observations over 22 years that suggests a period of about 11 years in the position angle variation of the jet. We infer that we are seeing a spinning black hole that induces the Lense-Thirring precession of a misaligned accretion disk. Similar jet precession may commonly occur in other active galactic nuclei but has been challenging to detect owing to the small magnitude and long period of the variation.

astro-ph.HE↗

arXiv2023

Explaining the 'outliers' track in Black Hole X-ray Binaries with the BZ-jet and inner-disk coupling

In this paper, we investigate the black hole (BH) spin contribution to jet power, especially for the magnetic arrested disk (MAD), where only inner accretion disk luminosity is closely coupled with the spin-jet power, and try to explain the `outliers' track of the radio $L_{\rm R}$ to X-ray luminosity $L_{\rm X}$ in two black hole X-ray binaries (BHXBs). Our results suggest that the BZ-jet and the inner-disk coupling could account for the `outliers' track of the radio/X-ray correlation in two BHXBs, H1743-322 and MAXI J1348-630. Although the accretion disk of H1743-322 in the outburst could be in the MAD state, there is a lower probability that MAXI J1348-630 is in the MAD state due to its low jet production efficiency. The difference in the inner-disk bolometric luminosity ratio of the two sources implies that these two BHXBs are in different inner-disk accretion states. We further investigate the phase-changing regime of MAXI J1348-630 and find that there is a phase transition around $L_{\rm X}/L_{\rm Edd}\sim 10^{-3}$. The assumption of sub-MAD is discussed as well.

astro-ph.HE↗

arXiv2023

TrialView: An AI-powered Visual Analytics System for Temporal Event Data in Clinical Trials

Randomized controlled trials (RCT) are the gold standards for evaluating the efficacy and safety of therapeutic interventions in human subjects. In addition to the pre-specified endpoints, trial participants' experience reveals the time course of the intervention. Few analytical tools exist to summarize and visualize the individual experience of trial participants. Visual analytics allows integrative examination of temporal event patterns of patient experience, thus generating insights for better care decisions. Towards this end, we introduce TrialView, an information system that combines graph artificial intelligence (AI) and visual analytics to enhance the dissemination of trial data. TrialView offers four distinct yet interconnected views: Individual, Cohort, Progression, and Statistics, enabling an interactive exploration of individual and group-level data. The TrialView system is a general-purpose analytical tool for a broad class of clinical trials. The system is powered by graph AI, knowledge-guided clustering, explanatory modeling, and graph-based agglomeration algorithms. We demonstrate the system's effectiveness in analyzing temporal event data through a case study.

cs.HC↗

arXiv2023

Constructing the $J^{P(C)}=1^{-(+)}$ light flavor hybrid nonet with the newly observed $η_1(1855)$

The recently discovered $η_1(1855)$ and the previously observed $π_1(1600)$ state present a valuable opportunity for the investigation of the $J^{P(C)}=1^{-(+)}$ light hybrid nonet. In this study, we employ a semirelativistic quark potential model to examine the masses of the $J^{P(C)}=1^{-(+)}$ light hybrid states. The static potential, which portrays the confinement force between the quark-antiquark pair in a hybrid system, is borrowed from the SU$(3)$ lattice gauge theory. Additionally, we utilize a constituent gluon model to analyze the strong decay characteristics of these light $1^{-+}$ hybrids. Our findings suggest that the $π_1(1600)$ and $η_1(1855)$ states could be potential candidates for $1^{-+}$ $(u\bar{u}-d\bar{d})g/\sqrt{2}$ and $s\bar{s}g$ hybrids, respectively. To ensure comprehensiveness, we also investigate the isospin partners of the $π_1(1600)$ and $η_1(1855)$ states within the $1^{-(+)}$ nonet$-$specifically, the $(u\bar{u}+d\bar{d})g/\sqrt{2}$ and $s\bar{q}g$ ($q=u$ and $d$ quarks) states. We propose some potential decay channels which could be explored in experimental settings to detect these undiscovered states.

hep-ph↗

arXiv2023

Higher molecular $P_{ψs}^{Λ/Σ}$ pentaquarks arising from the $Ξ_c^{(\prime,)}\bar D_1/Ξ_c^{(\prime,)}\bar D_2^*$ interactions

The discoveries of the $P_{ψs}^Λ(4459)$ and $P_{ψs}^Λ(4338)$ as the potential $Ξ_c\bar D^{(*)}$ molecules have sparked our curiosity in exploring a novel class of molecular $P_{ψs}^{Λ/Σ}$ pentaquarks. In this study, we carry out an investigation into the higher molecular pentaquarks, specifically focusing on the $P_{ψs}^{Λ/Σ}$ states arising from the $Ξ_c^{(\prime,*)}\bar D_1/Ξ_c^{(\prime,*)}\bar D_2^*$ interactions. Our approach employs the one-boson-exchange model, incorporating both the $S$-$D$ wave mixing effect and the coupled channel effect. Our numerical results suggest that the $Ξ_c\bar D_1$ states with $I(J^P)=0({1}/{2}^+,\,{3}/{2}^+)$, the $Ξ_c\bar D_2^*$ states with $I(J^P)=0({3}/{2}^+,\,{5}/{2}^+)$, the $Ξ_c^{\prime}\bar D_1$ states with $I(J^P)=0({1}/{2}^+,\,{3}/{2}^+)$, the $Ξ_c^{\prime}\bar D_2^*$ states with $I(J^P)=0({3}/{2}^+,\,{5}/{2}^+)$, the $Ξ_c^{*}\bar D_1$ states with $I(J^P)=0({1}/{2}^+,\,{3}/{2}^+,\,{5}/{2}^+)$, and the $Ξ_c^{*}\bar D_2^*$ states with $I(J^P)=0({1}/{2}^+,\,{3}/{2}^+,\,{5}/{2}^+,\,{7}/{2}^+)$ can be recommended as the most promising molecular $P_{ψs}^Λ$ pentaquark candidates, and there may exist the potential molecular $P_{ψs}^Σ$ pentaquark candidates for several isovector $Ξ_c^{(\prime,*)}\bar D_1/Ξ_c^{(\prime,*)}\bar D_2^*$ states. With the higher statistical data accumulation at the LHCb's Run II and Run III status, there is the possibility that our predicted $P_{ψs}^{Λ/Σ}$ states can be detected through the weak decay of the $Ξ_b$ baryon, especially in hunting for the predicted $P_{ψs}^Λ$ states.

hep-ph↗

arXiv2023

Spectroscopy behavior of fully heavy tetraquarks

Stimulated by the observation of the $X(6900)$ from LHCb in 2020 and the recent results from CMS and ATLAS in the di-$J/ψ$ invariant mass spectrum, in this work we systemically study all possible configurations for the ground fully heavy tetraquark states in constituent quark model. By our calculation, we present their spectroscopy behaviors like binding energy, lowest meson-meson thresholds, specific wave function, magnetic moment, transition magnetic moment, radiative decay width, rearrangement strong width ratio, internal mass contributions, relative lengths between (anti)quarks, and the spatial distribution of four valence (anti)quarks. We cannot find stable S-wave state for the fully heavy tetraquark system. We hope that our results are valuable to further explore fully heavy tetraquark states in experiment.

hep-ph↗

arXiv2023

Exploring the electromagnetic properties of the $Ξ_c^{(\prime,\,)} \bar D_s^$ and $Ω_c^{()} \bar D_s^$ molecular states

This paper presents a systematic investigation of the electromagnetic properties of the hidden-charm molecular pentaquarks within the constituent quark model. Specifically, it focuses on two types of pentaquarks: the $Ξ_c^{(\prime,*)} \bar{D}_s^{*}$-type pentaquarks with double strangeness and the $Ω_{c}^{(*)}\bar D_s^{*}$-type pentaquarks with triple strangeness. The study explores various electromagnetic properties, including the magnetic moments, the transition magnetic moments, and the radiative decay behavior of these pentaquarks. To ensure realistic calculations, the $S$-$D$ wave mixing effect and the coupled channel effect are taken into account. By examining the electromagnetic properties of the hidden-charm molecular pentaquarks with double and triple strangeness, this research contributes to the deeper understanding of their spectroscopic behavior. These findings form a valuable addition to the ongoing investigation into the broader spectrum of properties exhibited by the hidden-charm molecular pentaquarks.

hep-ph↗

arXiv2023

Quantitative KAM theory, with an application to the three-body problem

Based on quantitative ``{\sc kam} theory'', we state and prove two theorems about the continuation of maximal and whiskered quasi--periodic motions to slightly perturbed systems exhibiting proper degeneracy. Next, we apply such results to prove that, in the three--body problem, there is a small set in phase space where it is possible to detect both such families of tori. We also estimate the density of such motions in proper ambient spaces. Up to our knowledge, this is the first proof of co--existence of stable and whiskered tori in a physical system.

math.DS↗

arXiv2023

Depression Detection Using Digital Traces on Social Media: A Knowledge-aware Deep Learning Approach

Depression is a common disease worldwide. It is difficult to diagnose and continues to be underdiagnosed. Because depressed patients constantly share their symptoms, major life events, and treatments on social media, researchers are turning to user-generated digital traces on social media for depression detection. Such methods have distinct advantages in combating depression because they can facilitate innovative approaches to fight depression and alleviate its social and economic burden. However, most existing studies lack effective means to incorporate established medical domain knowledge in depression detection or suffer from feature extraction difficulties that impede greater performance. Following the design science research paradigm, we propose a Deep Knowledge-aware Depression Detection (DKDD) framework to accurately detect social media users at risk of depression and explain the critical factors that contribute to such detection. Extensive empirical studies with real-world data demonstrate that, by incorporating domain knowledge, our method outperforms existing state-of-the-art methods. Our work has significant implications for IS research in knowledge-aware machine learning, digital traces utilization, and NLP research in IS. Practically, by providing early detection and explaining the critical factors, DKDD can supplement clinical depression screening and enable large-scale evaluations of a population's mental health status.

cs.CL↗