Showing papers by "Xiang Liu published in 2023"

The newly observed $\Omega_c(3327)$: A good candidate for a $D$-wave charmed baryon

Abstract: The newly observed $\Omega_c(3327)$ gives us a good chance to construct the $\Omega_c$ charmed baryon family. In this work, we carry out the mass spectrum analysis by a non-relativistic potential model using Gaussian Expansion Method, and the study of its two-body Okubo-Zweig-Iizuka allowed strong decay behavior. Our results imply that the $\Omega_c(3327)$ is good candidate of $\Omega_c(1D)$ state with $J^P=5/2^+$. We also predict the spectroscopy behavior of other $\Omega_c(1D)$ states, which may provide further clues to their search.

Investigating the spectroscopy behavior of undetected $1F$-wave charmed baryons

Abstract: In this work, we investigate the spectroscopic properties of $1F$-wave charmed baryons, which have not yet been observed in experiments. We employ a non-relativistic potential model and utilize the Gaussian expansion method to obtain the mass spectra of these charmed baryons. Additionally, we focus on the two-body Okubo-Zweig-Iizuka allowed strong decay behaviors, which plays a crucial role in characterizing the properties of these baryons. Our comprehensive analyses of the mass spectra and two-body Okubo-Zweig-Iizuka allowed decay behaviors provides valuable insights for future experimental investigations. This study significantly contributes to our understandings of the spectroscopic properties of $1F$-wave charmed baryons.

Radiative decays and magnetic moments of the predicted <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> -like molecules

Abstract: In this work, we first perform a systematic study of the transition magnetic moments and the corresponding radiative decay behaviors of the $B_c$-like molecular states associated with their mass spectra, where the constituent quark model is adopted by considering the $S$-$D$ wave mixing effect. Our numerical results show that the radiative decay properties can be considered as the effective physical observable to reflect the inner structures of these $B_c$-like molecular states. Meanwhile, we also discuss the magnetic moments of the $B_c$-like molecular states, and we find that the magnetic moment properties can be used to distinguish the $B_c$-like molecular states from the conventional $B_c$ mesonic states, which have the same quantum numbers and similar masses. We expect that the present study can inspire the interest of the experimentalist in exploring the electromagnetic properties of the $B_c$-like molecular states, especially the radiative decay properties.

New type of hydrogenlike charm-pion or charm-kaon matter

Abstract: Borrowing the structures of the hydrogen atom, molecular ion, and diatomic molecule, we predict the nature of a new type of hydrogenlike charm-pion or charm-kaon matter that could be obtained by replacing the proton and electron in hydrogen matter with a charmed meson and a pion or a kaon, respectively. We find that the spectra of the atom, molecular ion, and diatomic molecule can be obtained simultaneously with the Coulomb potential for the hydrogen, the charm-pion, and the charm-kaon systems. The predicted charm-pion matter also allows us to explore the mass shift mediated by the strong interaction. For the charm-pion and charm-kaon systems, the strong interactions could lead to binding energy shifts. Our calculations suggests that the binding energy shifts in charm-pion systems are in the order of several to tens of eV. For the charm-kaon systems, the results are in the order of tens to hundreds of eV. Exploring hydrogenlike charm-pion matter must lead to new demands for high-precision experiments.

Effects of network junctions and defects on the crystallization of model poly(ethylene glycol) networks.

Abstract: Polymer crystallization drastically changes the physical properties of polymeric materials. However, the crystallization in polymer networks has been little explored. This study investigated the crystallization behavior of a series of poly(ethylene glycol) (PEG) networks consisting of well-defined branched precursors. The PEG networks were prepared by drying gels synthesized at various conditions. The PEG networks showed slower crystallization with lower final crystallinity than uncrosslinked PEGs with amine end groups. Surprisingly, the effect of network formation was not as significant as that of the relatively bulky end-groups introduced in the uncrosslinked polymer. The molecular weight of the precursor PEG, or equivalently the chain length between neighboring junctions, was the primary parameter that affected the crystallization of the PEG networks. Shorter network chains led to lower crystallization rates and final crystallinity. This effect became less significant as the network chain length increased. On the other hand, the spatial and topological defects formed in the gel synthesis process did not affect the crystallization in the polymer networks at all. The crystallization in the polymer networks seems insensitive to these mesoscopic defects and can be solely controlled by the chain length between junctions.

Electromagnetic properties of the predicted B c -like molecular states

Abstract: In this work, we first perform a systematic study of the magnetic moments of the B c -like molecular states associated with their mass spectra, where the constituent quark model is adopted by considering the S - D wave mixing e ff ect. Our numerical results suggest that the magnetic moment property can be considered as the ef-fective physical observable to reflect the inner structures of these B c -like molecular states. In particular, the magnetic moment property can be used to distinguish the B c -like molecular states from the conventional B c mesonic states, which have the same quantum numbers and similar masses. Meanwhile, we extend our theoretical framework to discuss the transition magnetic moments and the corresponding radiative decay behaviors of the B c -like molecular states. We expect that the present study can inspire the interest of experimentalist in exploring the electromagnetic properties of the B c -like molecular states.

AI of Brain and Cognitive Sciences: From the Perspective of First Principles

Abstract: Nowadays, we have witnessed the great success of AI in various applications, including image classification, game playing, protein structure analysis, language translation, and content generation. Despite these powerful applications, there are still many tasks in our daily life that are rather simple to humans but pose great challenges to AI. These include image and language understanding, few-shot learning, abstract concepts, and low-energy cost computing. Thus, learning from the brain is still a promising way that can shed light on the development of next-generation AI. The brain is arguably the only known intelligent machine in the universe, which is the product of evolution for animals surviving in the natural environment. At the behavior level, psychology and cognitive sciences have demonstrated that human and animal brains can execute very intelligent high-level cognitive functions. At the structure level, cognitive and computational neurosciences have unveiled that the brain has extremely complicated but elegant network forms to support its functions. Over years, people are gathering knowledge about the structure and functions of the brain, and this process is accelerating recently along with the initiation of giant brain projects worldwide. Here, we argue that the general principles of brain functions are the most valuable things to inspire the development of AI. These general principles are the standard rules of the brain extracting, representing, manipulating, and retrieving information, and here we call them the first principles of the brain. This paper collects six such first principles. They are attractor network, criticality, random network, sparse coding, relational memory, and perceptual learning. On each topic, we review its biological background, fundamental property, potential application to AI, and future development.

D̄s molecular states

Abstract: Fu-Lai Wang1,2,3,∗ Si-Qiang Luo1,2,3,† Hong-Yan Zhou1,2,‡ Zhan-Wei Liu1,2,3,§ and Xiang Liu1,2,3,4¶ 1School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China 2Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS, Lanzhou 730000, China 3Lanzhou Center for Theoretical Physics, Key Laboratory of Theoretical Physics of Gansu Province, and Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China 4Key Laboratory of Quantum Theory and Applications of MoE, Lanzhou University, Lanzhou 730000, China

Newly observed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="normal">Ω</mml:mi><mml:mi>c</mml:mi></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:mn>3327</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math> : A good candidate for a <mm

Abstract: The newly observed $\Omega_c(3327)$ gives us a good chance to construct the $\Omega_c$ charmed baryon family. In this work, we carry out the mass spectrum analysis by a non-relativistic potential model using Gaussian Expansion Method, and the study of its two-body Okubo-Zweig-Iizuka allowed strong decay behavior. Our results imply that the $\Omega_c(3327)$ is good candidate of $\Omega_c(1D)$ state with $J^P=5/2^+$. We also predict the spectroscopy behavior of other $\Omega_c(1D)$ states, which may provide further clues to their search.

Constructing the $J^{P(C)}=1^{-(+)}$ light flavor hybrid nonet with the newly observed $\eta_1(1855)$

Abstract: The recently discovered $\eta_1(1855)$ and the previously observed $\pi_1(1600)$ 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 $\pi_1(1600)$ and $\eta_1(1855)$ 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 $\pi_1(1600)$ and $\eta_1(1855)$ 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.

VLBI astrometry on the white dwarf pulsar AR Scorpii

Abstract: AR Scorpii (AR Sco), the only-known radio-pulsing white dwarf binary, shows unusual pulsating emission at the radio, infrared, optical and ultraviolet bands. To determine its astrometric parameters at the radio band independently, we conducted multi-epoch Very Long Baseline Interferometry (VLBI) phase-referencing observations with the European VLBI Network (EVN) at 5 GHz and the Chinese VLBI Network (CVN) plus the Warkworth 30-metre telescope (New Zealand) at 8.6 GHz. By using the differential VLBI astrometry, we provide high-precision astrometric measurements on the parallax ($\pi =8.52_{-0.07}^{+0.04}$ mas), and proper motion ($\mu _{\alpha }=9.48_{-0.07}^{+0.04}$ mas yr−1, $\mu _{\delta }=-51.32_{-0.38}^{+0.22}$ mas yr−1). The new VLBI results agree with the optical Gaia astrometry. Our kinematic analysis reveals that the Galactic space velocities of AR Sco are quite consistent with that of both intermediate polars (IPs) and polars. Combined with the previous tightest VLBI constraint on the size, our parallax distance suggests that the radio emission of AR Sco should be located within the light cylinder of its white dwarf.

Radiative decays and magnetic moments of the predicted $B_c$-like molecules

Abstract: In this work, we first perform a systematic study of the transition magnetic moments and the corresponding radiative decay behaviors of the $B_c$-like molecular states associated with their mass spectra, where the constituent quark model is adopted by considering the $S$-$D$ wave mixing effect. Our numerical results show that the radiative decay properties can be considered as the effective physical observable to reflect the inner structures of these $B_c$-like molecular states. Meanwhile, we also discuss the magnetic moments of the $B_c$-like molecular states, and we find that the magnetic moment properties can be used to distinguish the $B_c$-like molecular states from the conventional $B_c$ mesonic states, which have the same quantum numbers and similar masses. We expect that the present study can inspire the interest of the experimentalist in exploring the electromagnetic properties of the $B_c$-like molecular states, especially the radiative decay properties.