Pub Date : 2024-04-18DOI: 10.1007/s11433-023-2362-x
Dengke Zhou, Pei Wang, Di Li, Jianhua Fang, Chenchen Miao, Paulo C. C. Freire, Lei Zhang, Dandan Zhang, Huaxi Chen, Yi Feng, Yifan Xiao, Jintao Xie, Xu Zhang, Chenwu Jin, Han Wang, Yinan Ke, Xuerong Guo, Rushuang Zhao, Chenhui Niu, Weiwei Zhu, Mengyao Xue, Yabiao Wang, Jiafu Wu, Zhenye Gan, Zhongyi Sun, Chengjie Wang, Jie Zhang, Junshuo Zhang, Jinhuang Cao, Wanjin Lu
Globular clusters harbor numerous millisecond pulsars, but long-period pulsars (P ≳ 100 ms) are rarely found. In this study, we employed a fast folding algorithm to analyze observational data from multiple globular clusters obtained by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), aiming to detect the existence of long-period pulsars. We estimated the impact of the median filtering algorithm in eliminating red noise on the minimum detectable flux density (Smin) of pulsars. Subsequently, we successfully discovered two isolated long-period pulsars in M15 with periods approximately equal to 1.928451 and 3.960716 s, respectively. On the (P - dot P) diagram, both pulsars are positioned below the spin-up line, suggesting a possible history of partial recycling in X-ray binary systems disrupted by dynamical encounters later on. According to timing results, these two pulsars exhibit remarkably strong magnetic fields. If the magnetic fields were weakened during the accretion process, then a short duration of accretion might explain the strong magnetic fields of these pulsars.
球状星团蕴藏着大量毫秒脉冲星,但长周期脉冲星(P ≳ 100 ms)却很少被发现。在这项研究中,我们采用了一种快速折叠算法来分析由五百米孔径球面射电望远镜(FAST)获得的多个球状星团的观测数据,目的是探测长周期脉冲星的存在。我们估算了中值滤波算法在消除红噪方面对脉冲星最小可探测通量密度(Smin)的影响。随后,我们成功地在M15中发现了两颗孤立的长周期脉冲星,它们的周期分别约等于1.928451秒和3.960716秒。在(P - dot P )图上,这两颗脉冲星都位于自旋线的下方,这表明X射线双星系统可能存在部分循环的历史,后来因为动力学遭遇而中断。根据定时结果,这两颗脉冲星表现出明显的强磁场。如果磁场在吸积过程中被削弱,那么短时间的吸积也许可以解释这些脉冲星的强磁场。
{"title":"A discovery of two slow pulsars with FAST: “Ronin” from the globular cluster M15","authors":"Dengke Zhou, Pei Wang, Di Li, Jianhua Fang, Chenchen Miao, Paulo C. C. Freire, Lei Zhang, Dandan Zhang, Huaxi Chen, Yi Feng, Yifan Xiao, Jintao Xie, Xu Zhang, Chenwu Jin, Han Wang, Yinan Ke, Xuerong Guo, Rushuang Zhao, Chenhui Niu, Weiwei Zhu, Mengyao Xue, Yabiao Wang, Jiafu Wu, Zhenye Gan, Zhongyi Sun, Chengjie Wang, Jie Zhang, Junshuo Zhang, Jinhuang Cao, Wanjin Lu","doi":"10.1007/s11433-023-2362-x","DOIUrl":"https://doi.org/10.1007/s11433-023-2362-x","url":null,"abstract":"<p>Globular clusters harbor numerous millisecond pulsars, but long-period pulsars (<i>P</i> ≳ 100 ms) are rarely found. In this study, we employed a fast folding algorithm to analyze observational data from multiple globular clusters obtained by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), aiming to detect the existence of long-period pulsars. We estimated the impact of the median filtering algorithm in eliminating red noise on the minimum detectable flux density (<i>S</i><sub>min</sub>) of pulsars. Subsequently, we successfully discovered two isolated long-period pulsars in M15 with periods approximately equal to 1.928451 and 3.960716 s, respectively. On the <span>(P - dot P)</span> diagram, both pulsars are positioned below the spin-up line, suggesting a possible history of partial recycling in X-ray binary systems disrupted by dynamical encounters later on. According to timing results, these two pulsars exhibit remarkably strong magnetic fields. If the magnetic fields were weakened during the accretion process, then a short duration of accretion might explain the strong magnetic fields of these pulsars.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140798312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-12DOI: 10.1007/s11433-023-2311-3
Xiuhui Hou, Bin Wang, Zichen Deng
In comparison to conventional hexagonal honeycomb structures, auxetic metamaterials with re-entrant configurations have exhibited superior mechanical properties in terms of energy absorption. To further enhance the energy absorption capacity of these materials, a novel re-entrant honeycomb configuration, named novel auxetic re-entrant honeycomb (NARH), is developed by incorporating “<>”-shaped cell walls into the conventional auxetic re-entrant honeycomb (ARH). Two analytical models for the plateau stress are formulated to consider the plastic deformation of NARH during quasi-static compression and the dynamic impact using the linear momentum theorem. Quasi-static compression tests on 3D printed NARH honeycomb specimens and finite element simulations are performed to verify the effectiveness of the theoretical models. NARH exhibits higher plateau stresses compared with ARH during compression, which can be attributed to the presence of more plastic hinges formed in NARH. These hinges, the embedded parts with inclined cell walls, not only improve stability by forming stable triangles during compression but also enhance the energy absorption capacity. A parametric study is conducted to analyze the effect of impact velocity, thickness, and incline angle of cell walls on crashworthiness. Numerical simulations demonstrate higher sensitivity of the mechanical properties to impact velocity and cell wall thickness. Adding ribs to the “<>”-shaped cell walls in NARH further reduces the initial peak force during dynamic crushing while maintaining high energy absorption. The research provides valuable guidelines for the design of energy absorption metamaterials.
{"title":"Tailored energy absorption for a novel auxetic honeycomb structure under large deformation","authors":"Xiuhui Hou, Bin Wang, Zichen Deng","doi":"10.1007/s11433-023-2311-3","DOIUrl":"https://doi.org/10.1007/s11433-023-2311-3","url":null,"abstract":"<p>In comparison to conventional hexagonal honeycomb structures, auxetic metamaterials with re-entrant configurations have exhibited superior mechanical properties in terms of energy absorption. To further enhance the energy absorption capacity of these materials, a novel re-entrant honeycomb configuration, named novel auxetic re-entrant honeycomb (NARH), is developed by incorporating “<>”-shaped cell walls into the conventional auxetic re-entrant honeycomb (ARH). Two analytical models for the plateau stress are formulated to consider the plastic deformation of NARH during quasi-static compression and the dynamic impact using the linear momentum theorem. Quasi-static compression tests on 3D printed NARH honeycomb specimens and finite element simulations are performed to verify the effectiveness of the theoretical models. NARH exhibits higher plateau stresses compared with ARH during compression, which can be attributed to the presence of more plastic hinges formed in NARH. These hinges, the embedded parts with inclined cell walls, not only improve stability by forming stable triangles during compression but also enhance the energy absorption capacity. A parametric study is conducted to analyze the effect of impact velocity, thickness, and incline angle of cell walls on crashworthiness. Numerical simulations demonstrate higher sensitivity of the mechanical properties to impact velocity and cell wall thickness. Adding ribs to the “<>”-shaped cell walls in NARH further reduces the initial peak force during dynamic crushing while maintaining high energy absorption. The research provides valuable guidelines for the design of energy absorption metamaterials.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-12DOI: 10.1007/s11433-023-2332-5
Ruoyun Huang, Baitian Tang, Chengyuan Li, Doug Geisler, Mario Mateo, Ying-Yi Song, Holger Baumgardt, Julio A. Carballo-Bello, Yue Wang, Jundan Nie, Bruno Dias, José G. Fernández-Trincado
Star clusters were historically considered simple stellar populations, with all stars sharing the same age and initial chemical composition. However, the presence of chemical anomalies in globular clusters (GCs), called multiple stellar populations (MPs), has challenged star formation theories in dense environments. Literature studies show that mass, metallicity, and age are likely controlling parameters for the manifestation of MPs. Identifying the limit between clusters with/without MPs in physical parameter space is crucial to reveal the driving mechanism behind their presence. In this study, we look for MP signals in Whiting 1, which is traditionally considered a young GC. Using the Magellan telescope, we obtained low-resolution spectra within λλ = 3850–5500 Å for eight giants of Whiting 1. We measured the C and N abundances from the CN and CH spectral indices. C and N abundances have variations comparable with their measurement errors (∼ 0.1 dex), suggesting that MPs are absent from Whiting 1. Combining these findings with literature studies, we propose a limit in the metallicity vs. cluster compactness index parameter space, which relatively clearly separates star clusters with/without MPs (GCs/open clusters). This limit is physically motivated. On a larger scale, the galactic environment determines cluster compactness and metallicity, leading to metal-rich, diffuse, old clusters formed ex situ. Our proposed limit also impacts our understanding of the formation of the Sagittarius dwarf galaxy: star clusters formed after the first starburst (age≲ 8–10 Gyr). These clusters are simple stellar populations because the enriched galactic environment is no longer suitable for MP formation.
星团历来被认为是简单的恒星群,所有恒星都具有相同的年龄和初始化学成分。然而,球状星团(GCs)中出现的化学反常现象,即多恒星群(MPs),对致密环境中的恒星形成理论提出了挑战。文献研究表明,质量、金属性和年龄可能是多恒星群表现的控制参数。在物理参数空间中确定有/无多恒星的星团之间的界限,对于揭示多恒星存在背后的驱动机制至关重要。在这项研究中,我们在传统上被认为是年轻 GC 的 Whiting 1 中寻找 MP 信号。利用麦哲伦望远镜,我们获得了惠廷 1 号八个巨星在 λλ = 3850-5500 Å 范围内的低分辨率光谱。我们根据 CN 和 CH 光谱指数测量了 C 和 N 丰度。C 丰度和 N 丰度的变化与其测量误差相当(∼ 0.1 dex),表明惠廷 1 号不存在 MPs。结合这些发现和文献研究,我们提出了金属性与星团紧密度指数参数空间的一个极限,它能相对清晰地将有/无MPs的星团(GCs/开放星团)区分开来。这个极限是以物理为基础的。在更大的尺度上,星系环境决定了星团的紧密度和金属度,从而导致了富含金属、弥散的、原地形成的古老星团。我们提出的极限还影响到我们对人马座矮星系形成过程的理解:在第一次恒星爆发(年龄≲ 8-10 Gyr)之后形成的星团。这些星团是简单的恒星群,因为富集的星系环境不再适合形成MP。
{"title":"Driving factors behind multiple populations","authors":"Ruoyun Huang, Baitian Tang, Chengyuan Li, Doug Geisler, Mario Mateo, Ying-Yi Song, Holger Baumgardt, Julio A. Carballo-Bello, Yue Wang, Jundan Nie, Bruno Dias, José G. Fernández-Trincado","doi":"10.1007/s11433-023-2332-5","DOIUrl":"https://doi.org/10.1007/s11433-023-2332-5","url":null,"abstract":"<p>Star clusters were historically considered simple stellar populations, with all stars sharing the same age and initial chemical composition. However, the presence of chemical anomalies in globular clusters (GCs), called multiple stellar populations (MPs), has challenged star formation theories in dense environments. Literature studies show that mass, metallicity, and age are likely controlling parameters for the manifestation of MPs. Identifying the limit between clusters with/without MPs in physical parameter space is crucial to reveal the driving mechanism behind their presence. In this study, we look for MP signals in Whiting 1, which is traditionally considered a young GC. Using the Magellan telescope, we obtained low-resolution spectra within <i>λλ</i> = 3850–5500 Å for eight giants of Whiting 1. We measured the C and N abundances from the CN and CH spectral indices. C and N abundances have variations comparable with their measurement errors (∼ 0.1 dex), suggesting that MPs are absent from Whiting 1. Combining these findings with literature studies, we propose a limit in the metallicity vs. cluster compactness index parameter space, which relatively clearly separates star clusters with/without MPs (GCs/open clusters). This limit is physically motivated. On a larger scale, the galactic environment determines cluster compactness and metallicity, leading to metal-rich, diffuse, old clusters formed ex situ. Our proposed limit also impacts our understanding of the formation of the Sagittarius dwarf galaxy: star clusters formed after the first starburst (age≲ 8–10 Gyr). These clusters are simple stellar populations because the enriched galactic environment is no longer suitable for MP formation.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-12DOI: 10.1007/s11433-023-2333-8
Yingjie Jing, Jie Wang, Chen Xu, Ziming Liu, Qingze Chen, Tiantian Liang, Jinlong Xu, Yixian Cao, Jing Wang, Huijie Hu, Chuan-Peng Zhang, Qi Guo, Liang Gao, Mei Ai, Hengqian Gan, Xuyang Gao, Jinlin Han, Ligang Hou, Zhipeng Hou, Peng Jiang, Xu Kong, Fujia Li, Zerui Liu, Li Shao, Hengxing Pan, Jun Pan, Lei Qian, Jinghai Sun, Ningyu Tang, Qingliang Yang, Bo Zhang, Zhiyu Zhang, Ming Zhu
The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has the largest aperture and a 19-beam L-band receiver, making it powerful for investigating the neutral hydrogen atomic gas (Hi) in the universe. We present HiFAST (https://hifast.readthedocs.io), a dedicated, modular, and self-contained calibration and imaging pipeline for processing the Hi data of FAST. The pipeline consists of frequency-dependent noise diode calibration, baseline fitting, standing wave removal using an FFT-based method, flux density calibration, stray radiation correction, and gridding to produce data cubes. These modules can be combined as needed to process the data from most FAST observation modes: tracking, drift scanning, On-The-Fly mapping, and most of their variants. With HiFAST, the root-mean-square (RMS) noises of the calibrated spectra from all 19 beams were only slightly (∼5%) higher than the theoretical expectation. The results for the extended source M33 and the point sources are consistent with the results from Arecibo. The moment maps (0, 1 and 2) of M33 agree well with the results from the Arecibo Galaxy Environment Survey (AGES) with a fractional difference of less than 10%. For a common sample of 221 sources with signal-to-noise ratio S/N > 10 from the Arecibo Legacy Fast ALFA (ALFALFA) survey, the mean value of fractional difference in the integrated flux density, Sint, between the two datasets is approximately 0.005%, with a dispersion of 15.4%. Further checks on the integrated flux density of 23 sources with seven observations indicate that the variance in the flux density of the source with luminous objects (Sint > 2.5 Jy km s−1) is less than 5%. Our tests suggest that the FAST telescope, with the efficient, precise, and user-friendly pipeline HiFAST, will yield numerous significant scientific findings in the investigation of the Hi in the universe.
五百米孔径球面射电望远镜(FAST)拥有最大的孔径和 19 波束 L 波段接收器,使其成为研究宇宙中性氢原子气体(Hi)的强大工具。我们介绍了用于处理 FAST 氢气数据的专用、模块化和独立的校准和成像管道 HiFAST (https://hifast.readthedocs.io)。该管道包括频率相关噪声二极管校准、基线拟合、使用基于 FFT 的方法去除驻波、通量密度校准、杂散辐射校正和网格划分以生成数据立方体。这些模块可根据需要进行组合,以处理来自大多数 FAST 观测模式的数据:跟踪、漂移扫描、"即时 "绘图及其大多数变体。使用HiFAST,所有19个波束的校准光谱的均方根噪声(RMS)仅略高于理论预期(∼5%)。扩展源 M33 和点源的结果与阿雷西博的结果一致。M33 的矩图(0、1 和 2)与阿雷西博星系环境巡天(AGES)的结果非常吻合,分数差异小于 10%。对于来自阿雷西博遗留快速 ALFA(ALFALFA)巡天的 221 个信噪比 S/N > 10 的共同样本,两个数据集的积分通量密度 Sint 的分数差异平均值约为 0.005%,离散度为 15.4%。对 23 个源的 7 次观测的综合通量密度的进一步检查表明,有发光物体的源的通量密度(Sint > 2.5 Jy km s-1)的方差小于 5%。我们的测试表明,FAST望远镜与高效、精确和用户友好的管道HiFAST一起,将在宇宙中的Hi的研究中产生许多重要的科学发现。
{"title":"HiFAST: An Hi data calibration and imaging pipeline for FAST","authors":"Yingjie Jing, Jie Wang, Chen Xu, Ziming Liu, Qingze Chen, Tiantian Liang, Jinlong Xu, Yixian Cao, Jing Wang, Huijie Hu, Chuan-Peng Zhang, Qi Guo, Liang Gao, Mei Ai, Hengqian Gan, Xuyang Gao, Jinlin Han, Ligang Hou, Zhipeng Hou, Peng Jiang, Xu Kong, Fujia Li, Zerui Liu, Li Shao, Hengxing Pan, Jun Pan, Lei Qian, Jinghai Sun, Ningyu Tang, Qingliang Yang, Bo Zhang, Zhiyu Zhang, Ming Zhu","doi":"10.1007/s11433-023-2333-8","DOIUrl":"https://doi.org/10.1007/s11433-023-2333-8","url":null,"abstract":"<p>The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has the largest aperture and a 19-beam L-band receiver, making it powerful for investigating the neutral hydrogen atomic gas (H<span>i</span>) in the universe. We present HiFAST (https://hifast.readthedocs.io), a dedicated, modular, and self-contained calibration and imaging pipeline for processing the H<span>i</span> data of FAST. The pipeline consists of frequency-dependent noise diode calibration, baseline fitting, standing wave removal using an FFT-based method, flux density calibration, stray radiation correction, and gridding to produce data cubes. These modules can be combined as needed to process the data from most FAST observation modes: tracking, drift scanning, On-The-Fly mapping, and most of their variants. With HiFAST, the root-mean-square (RMS) noises of the calibrated spectra from all 19 beams were only slightly (∼5%) higher than the theoretical expectation. The results for the extended source M33 and the point sources are consistent with the results from Arecibo. The moment maps (0, 1 and 2) of M33 agree well with the results from the Arecibo Galaxy Environment Survey (AGES) with a fractional difference of less than 10%. For a common sample of 221 sources with signal-to-noise ratio S/N > 10 from the Arecibo Legacy Fast ALFA (ALFALFA) survey, the mean value of fractional difference in the integrated flux density, <i>S</i><sub>int</sub>, between the two datasets is approximately 0.005%, with a dispersion of 15.4%. Further checks on the integrated flux density of 23 sources with seven observations indicate that the variance in the flux density of the source with luminous objects (<i>S</i><sub>int</sub> > 2.5 Jy km s<sup>−1</sup>) is less than 5%. Our tests suggest that the FAST telescope, with the efficient, precise, and user-friendly pipeline HiFAST, will yield numerous significant scientific findings in the investigation of the H<span>i</span> in the universe.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We discuss a novel window to probe the origin of our universe via the mass functions of primordial black holes (PBHs). The mass functions of PBHs are simply estimated using the conventional Press-Schechter formalism for two paradigms of cosmic origin, including inflationary ΛCDM and bounce cosmology. The standard inflationary ΛCDM model cannot generate an appreciable number of massive PBHs; however, non-trivial inflation models with blue-tilted power spectra at small scales and matter bounce cosmology provide formation mechanisms for heavy PBHs, which in turn, may seed the observed supermassive black holes (SMBHs). By fitting the SMBH mass functions at high redshift (z ∼ 6) derived from Sloan Digital Sky Survey (SDSS) and Canada-France High-z Quasar Survey (CFHQS) quasars, for two paradigms of cosmic origin, we derive constraints on the PBH density fraction fPBH at z ∼ 6 and the characteristic mass M⋆, with the prior assumption that all SMBHs stem from PBHs. We demonstrate that this newly proposed procedure, relying on astronomical measurements that utilize deep-field surveys of SMBHs at high redshift, can be used to constrain models of cosmic origin. Additionally, although not the main focus of this paper, we evolve the mass function from z ∼ 6 to z ∼ 0 through an assumption of 3 × 108-year Eddington’s accretion, and give a rough estimation of fPBH at z ∼ 0.
我们讨论了通过原始黑洞(PBHs)的质量函数探测宇宙起源的一个新窗口。我们使用传统的普雷斯-舍赫特(Press-Schechter)形式对两种宇宙起源范式(包括暴胀ΛCDM和反弹宇宙学)的原始黑洞质量函数进行了简单估算。标准的通胀ΛCDM模型无法产生数量可观的大质量PBH;然而,在小尺度上具有蓝倾功率谱的非三轴通胀模型和物质反弹宇宙学提供了重PBH的形成机制,而这反过来又可能为观测到的超大质量黑洞(SMBH)提供种子。通过拟合斯隆数字巡天(SDSS)和加拿大-法国高兹类星体巡天(CFHQS)类星体在高红移(z ∼ 6)时的超大质量黑洞质量函数,我们得出了两种宇宙起源范式的约束条件,即z ∼ 6时的PBH密度分数fPBH和特征质量M⋆,并预先假定所有超大质量黑洞都来自PBH。我们证明,这个新提出的程序,依靠利用对高红移 SMBH 的深场巡天测量,可以用来约束宇宙起源模型。此外,虽然这不是本文的重点,但我们通过 3 × 108 年爱丁顿吸积的假设,演化了从 z ∼ 6 到 z ∼ 0 的质量函数,并给出了 z ∼ 0 时 fPBH 的粗略估计值。
{"title":"Primordial black hole mass functions as a probe of cosmic origin","authors":"Yi-Fu Cai, Chengfeng Tang, Geyu Mo, Sheng-Feng Yan, Chao Chen, Xiao-Han Ma, Bo Wang, Wentao Luo, Damien A. Easson, Antonino Marcianò","doi":"10.1007/s11433-023-2314-1","DOIUrl":"https://doi.org/10.1007/s11433-023-2314-1","url":null,"abstract":"<p>We discuss a novel window to probe the origin of our universe via the mass functions of primordial black holes (PBHs). The mass functions of PBHs are simply estimated using the conventional Press-Schechter formalism for two paradigms of cosmic origin, including inflationary ΛCDM and bounce cosmology. The standard inflationary ΛCDM model cannot generate an appreciable number of massive PBHs; however, non-trivial inflation models with blue-tilted power spectra at small scales and matter bounce cosmology provide formation mechanisms for heavy PBHs, which in turn, may seed the observed supermassive black holes (SMBHs). By fitting the SMBH mass functions at high redshift (<i>z</i> ∼ 6) derived from Sloan Digital Sky Survey (SDSS) and Canada-France High-<i>z</i> Quasar Survey (CFHQS) quasars, for two paradigms of cosmic origin, we derive constraints on the PBH density fraction <i>f</i><sub>PBH</sub> at <i>z</i> ∼ 6 and the characteristic mass <i>M</i><sub>⋆</sub>, with the prior assumption that all SMBHs stem from PBHs. We demonstrate that this newly proposed procedure, relying on astronomical measurements that utilize deep-field surveys of SMBHs at high redshift, can be used to constrain models of cosmic origin. Additionally, although not the main focus of this paper, we evolve the mass function from <i>z</i> ∼ 6 to <i>z</i> ∼ 0 through an assumption of 3 × 10<sup>8</sup>-year Eddington’s accretion, and give a rough estimation of <i>f</i><sub>PBH</sub> at <i>z</i> ∼ 0.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Three-dimensional (3D) phononic topological insulators (TIs) featuring two-dimensional (2D) surface states and one-dimensional (1D) hinge states have opened up a new route for multi-dimensional robust wave transport, providing unprecedented methods for integrated acoustic sensors and energy harvesting devices. However, aiming at the elastic 3D phononic TI with gapless surface states and hinge states, the realization of elastic 3D phononic TIs with gapless surface states and hinge states is a significant challenge due to the complicated multi-mode polarization of elastic waves in 3D structures. In this study, we demonstrate an elastic 3D phononic TI with a Dirac hierarchy by elaborately operating the corresponding spatial symmetries of the chiral honeycomb lattice. First, a 3D double Dirac cone of elastic wave can be achieved by doubling the lattice along the out-of-plane direction to fold two iso-frequency Weyl points. The topological phase transitions and 2D gapless two-fold Dirac surface states of elastic wave are realized by breaking the half-lattice spatial translation symmetry. Subsequently, based on the Brillouin zone folding along the in-plane direction, the 2D gapless two-fold surface Dirac cones are folded into four-fold surface Dirac cones. Finally, by inducing the relative radius of adjacent holes to break the in-plane spatial inversion symmetry, the fourfold surface Dirac cones are gapped and associated with a surface state inversion, in which the gapless 1D hinge Dirac dispersion is achieved. This research offers a route for engineering the hierarchies of TIs in 3D elastic wave systems and provides new possibilities for designing 3D ultrasonic devices with unconventional functions.
以二维(2D)表面态和一维(1D)铰链态为特征的三维(3D)声波拓扑绝缘体(TIs)为多维稳健波传输开辟了一条新途径,为集成声学传感器和能量收集设备提供了前所未有的方法。然而,针对具有无间隙表面态和铰链态的弹性三维声子 TI,由于弹性波在三维结构中的多模极化非常复杂,因此实现具有无间隙表面态和铰链态的弹性三维声子 TI 是一项重大挑战。在本研究中,我们通过精心操作手性蜂巢晶格的相应空间对称性,展示了具有狄拉克层次结构的弹性三维声波 TI。首先,通过将晶格沿平面外方向加倍,折叠两个等频 Weyl 点,可以实现弹性波的三维双 Dirac 锥。通过打破半晶格空间平移对称性,实现了弹性波的拓扑相变和二维无间隙双折叠狄拉克表面态。随后,基于布里渊区沿面内方向的折叠,二维无间隙两折表面狄拉克锥被折叠成四折表面狄拉克锥。最后,通过诱导相邻孔的相对半径来打破面内空间反转对称性,使四倍表面狄拉克锥产生间隙并与表面态反转相关联,从而实现无间隙一维铰链狄拉克色散。这项研究为三维弹性波系统中 TI 的分层工程提供了一条途径,并为设计具有非常规功能的三维超声器件提供了新的可能性。
{"title":"Elastic three-dimensional phononic topological insulators with Dirac hierarchy","authors":"Shao-Yong Huo, Qiu-Shuang Yang, Jiu-Jiu Chen, Hong-Kang Li, Long-Chao Yao, Fu-Chun He, Chun-Ming Fu","doi":"10.1007/s11433-023-2331-5","DOIUrl":"https://doi.org/10.1007/s11433-023-2331-5","url":null,"abstract":"<p>Three-dimensional (3D) phononic topological insulators (TIs) featuring two-dimensional (2D) surface states and one-dimensional (1D) hinge states have opened up a new route for multi-dimensional robust wave transport, providing unprecedented methods for integrated acoustic sensors and energy harvesting devices. However, aiming at the elastic 3D phononic TI with gapless surface states and hinge states, the realization of elastic 3D phononic TIs with gapless surface states and hinge states is a significant challenge due to the complicated multi-mode polarization of elastic waves in 3D structures. In this study, we demonstrate an elastic 3D phononic TI with a Dirac hierarchy by elaborately operating the corresponding spatial symmetries of the chiral honeycomb lattice. First, a 3D double Dirac cone of elastic wave can be achieved by doubling the lattice along the out-of-plane direction to fold two iso-frequency Weyl points. The topological phase transitions and 2D gapless two-fold Dirac surface states of elastic wave are realized by breaking the half-lattice spatial translation symmetry. Subsequently, based on the Brillouin zone folding along the in-plane direction, the 2D gapless two-fold surface Dirac cones are folded into four-fold surface Dirac cones. Finally, by inducing the relative radius of adjacent holes to break the in-plane spatial inversion symmetry, the fourfold surface Dirac cones are gapped and associated with a surface state inversion, in which the gapless 1D hinge Dirac dispersion is achieved. This research offers a route for engineering the hierarchies of TIs in 3D elastic wave systems and provides new possibilities for designing 3D ultrasonic devices with unconventional functions.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-11DOI: 10.1007/s11433-023-2324-0
Jiaqing Gao, Zhenyu Zhang, Ping Cui
Two-dimensional systems that simultaneously harbor superconductivity and nontrivial band topology may serve as appealing platforms for realizing topological superconductivity with promising applications in fault-tolerant quantum computing. Here, based on first-principles calculations, we show that monolayered CoN and CoP with the isovalent FeSe-like structure are stable in freestanding form, even though their known bulk phases have no resemblance to layering. The two systems are further revealed to display intrinsic band inversions due to crystal field splitting, and such orderings are preserved with the inclusion of spin-orbit coupling (SOC), which otherwise is able to open a curved band gap, yielding a non-zero Z2 topological invariant in each case. Such a mechanism of topologicalization is distinctly contrasted with that identified recently for the closely related monolayers of CoX (X = As, Sb, Bi), where the SOC plays an indispensable role in causing a nontrivial band inversion. Next, we demonstrate that, by applying equi-biaxial tensile strain, the electron-phonon coupling strength in monolayered CoN can be significantly enhanced, yielding a superconducting transition temperature (Tc) up to 7–12 K for the Coulomb pseudopotential of μ* = 0.2–0.1, while the CoP monolayer shows very low Tc even under pronounced strain. Their different superconducting behaviors can be attributed to different variations in lattice softening and electronic density of states around the Fermi level upon pressuring. Our central findings enrich the understanding of different mechanisms of band inversions and topologicalization and offer platforms for achieving the coexistence of superconductivity and nontrivial band topology based on two-dimensional systems.
{"title":"Topological and superconducting properties of monolayered CoN and CoP: A first-principles comparative study","authors":"Jiaqing Gao, Zhenyu Zhang, Ping Cui","doi":"10.1007/s11433-023-2324-0","DOIUrl":"https://doi.org/10.1007/s11433-023-2324-0","url":null,"abstract":"<p>Two-dimensional systems that simultaneously harbor superconductivity and nontrivial band topology may serve as appealing platforms for realizing topological superconductivity with promising applications in fault-tolerant quantum computing. Here, based on first-principles calculations, we show that monolayered CoN and CoP with the isovalent FeSe-like structure are stable in freestanding form, even though their known bulk phases have no resemblance to layering. The two systems are further revealed to display intrinsic band inversions due to crystal field splitting, and such orderings are preserved with the inclusion of spin-orbit coupling (SOC), which otherwise is able to open a curved band gap, yielding a non-zero <i>Z</i><sub>2</sub> topological invariant in each case. Such a mechanism of topologicalization is distinctly contrasted with that identified recently for the closely related monolayers of CoX (X = As, Sb, Bi), where the SOC plays an indispensable role in causing a nontrivial band inversion. Next, we demonstrate that, by applying equi-biaxial tensile strain, the electron-phonon coupling strength in monolayered CoN can be significantly enhanced, yielding a superconducting transition temperature (<i>T</i><sub>c</sub>) up to 7–12 K for the Coulomb pseudopotential of <i>μ*</i> = 0.2–0.1, while the CoP monolayer shows very low <i>T</i><sub>c</sub> even under pronounced strain. Their different superconducting behaviors can be attributed to different variations in lattice softening and electronic density of states around the Fermi level upon pressuring. Our central findings enrich the understanding of different mechanisms of band inversions and topologicalization and offer platforms for achieving the coexistence of superconductivity and nontrivial band topology based on two-dimensional systems.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-11DOI: 10.1007/s11433-023-2321-9
Ruizhi Dong, Yihuan Zhu, Dongxing Mao, Xu Wang, Yong Li
Devices that surpass the restriction of reciprocity of classical physical waves have brought intriguing possibilities for wave modulation. Non-reciprocal acoustic devices that rely on the viscosity of the medium or nonlinear effect have low efficiency and distortion problems respectively, and poor immunity to defects. The appearance of acoustic topological insulators achieves non-reciprocal transport with high robustness. However, the local nature of topological states means that their appearance depends on a system with a larger dimension. That is, most of the area of a topological device is occupied by useless lattices that do not directly contribute to non-reciprocal transport. The extra cost of topology protection severely limits the application scenarios of topology states, decreases the cost-effectiveness of topology devices, and is not conducive to device miniaturization and integration. In this work, we construct an acoustic three-layer heterojunction by introducing two types of domain walls into a conventional quantum Hall effect acoustic topological insulator, and successfully construct a non-reciprocal scattering network that forms topological modes spanning the interlayer domain. These extended states are still protected by bulk-band topology, making their non-reciprocity robust against disorder. This structure flawlessly realizes the path broadening in a two-dimensional topological system and can accomplish functions such as non-reciprocal acoustic splitting and multichannel transmission. Our work opens up opportunities for developing topological-insulator-based non-reciprocal devices in acoustics.
{"title":"Topological non-reciprocal robust waveguide transport","authors":"Ruizhi Dong, Yihuan Zhu, Dongxing Mao, Xu Wang, Yong Li","doi":"10.1007/s11433-023-2321-9","DOIUrl":"https://doi.org/10.1007/s11433-023-2321-9","url":null,"abstract":"<p>Devices that surpass the restriction of reciprocity of classical physical waves have brought intriguing possibilities for wave modulation. Non-reciprocal acoustic devices that rely on the viscosity of the medium or nonlinear effect have low efficiency and distortion problems respectively, and poor immunity to defects. The appearance of acoustic topological insulators achieves non-reciprocal transport with high robustness. However, the local nature of topological states means that their appearance depends on a system with a larger dimension. That is, most of the area of a topological device is occupied by useless lattices that do not directly contribute to non-reciprocal transport. The extra cost of topology protection severely limits the application scenarios of topology states, decreases the cost-effectiveness of topology devices, and is not conducive to device miniaturization and integration. In this work, we construct an acoustic three-layer heterojunction by introducing two types of domain walls into a conventional quantum Hall effect acoustic topological insulator, and successfully construct a non-reciprocal scattering network that forms topological modes spanning the interlayer domain. These extended states are still protected by bulk-band topology, making their non-reciprocity robust against disorder. This structure flawlessly realizes the path broadening in a two-dimensional topological system and can accomplish functions such as non-reciprocal acoustic splitting and multichannel transmission. Our work opens up opportunities for developing topological-insulator-based non-reciprocal devices in acoustics.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-11DOI: 10.1007/s11433-023-2328-1
Qichao Tian, Chi Ding, Xiaodong Qiu, Qinghao Meng, Kaili Wang, Fan Yu, Yuyang Mu, Can Wang, Jian Sun, Yi Zhang
Layered material TaS2 hosts multiple structural phases and exotic correlated quantum states, including charge density wave (CDW), superconductivity, quantum spin liquid, and Mott insulating state. Here, we synthesized TaS2 monolayers in H and T phases using the molecular beam epitaxial (MBE) method and studied their electronic structures via angle-resolved photo-emission spectroscopy (ARPES). We found that the H phase TaS2 (H-TaS2) monolayer is metallic, with an energy band crossing the Fermi level. In contrast, the T phase TaS2 (T-TaS2) monolayer shows an insulated energy gap at the Fermi level, while the normal calculated band structure implies it should be metallic without any band gap. However, by considering Hubbard interaction potential U, further density functional theory (DFT) calculation suggests that monolayer T-TaS2 could be a CDW Mott insulator, and the DFT+U calculation matches well with the ARPES result. More significantly, the temperature-dependent ARPES result indicates that the CDW Mott state in the T-TaS2 monolayer is more robust than its bulk counterpart and can persist at room temperature. Our results reveal that the dimensional effect can enhance the CDW Mott state and provide valuable insights for further exploring the exotic properties of monolayer TaS2.
{"title":"Electronic structures and Mott state of epitaxial TaS2 monolayers","authors":"Qichao Tian, Chi Ding, Xiaodong Qiu, Qinghao Meng, Kaili Wang, Fan Yu, Yuyang Mu, Can Wang, Jian Sun, Yi Zhang","doi":"10.1007/s11433-023-2328-1","DOIUrl":"https://doi.org/10.1007/s11433-023-2328-1","url":null,"abstract":"<p>Layered material TaS<sub>2</sub> hosts multiple structural phases and exotic correlated quantum states, including charge density wave (CDW), superconductivity, quantum spin liquid, and Mott insulating state. Here, we synthesized TaS<sub>2</sub> monolayers in H and T phases using the molecular beam epitaxial (MBE) method and studied their electronic structures via angle-resolved photo-emission spectroscopy (ARPES). We found that the H phase TaS<sub>2</sub> (H-TaS<sub>2</sub>) monolayer is metallic, with an energy band crossing the Fermi level. In contrast, the T phase TaS<sub>2</sub> (T-TaS<sub>2</sub>) monolayer shows an insulated energy gap at the Fermi level, while the normal calculated band structure implies it should be metallic without any band gap. However, by considering Hubbard interaction potential <i>U</i>, further density functional theory (DFT) calculation suggests that monolayer T-TaS<sub>2</sub> could be a CDW Mott insulator, and the DFT+<i>U</i> calculation matches well with the ARPES result. More significantly, the temperature-dependent ARPES result indicates that the CDW Mott state in the T-TaS<sub>2</sub> monolayer is more robust than its bulk counterpart and can persist at room temperature. Our results reveal that the dimensional effect can enhance the CDW Mott state and provide valuable insights for further exploring the exotic properties of monolayer TaS<sub>2</sub>.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-11DOI: 10.1007/s11433-023-2345-3
GuangHui Xing, Qi Hao, Fan Zhu, Yun-Jiang Wang, Yong Yang, Hidemi Kato, Eloi Pineda, Si Lan, JiChao Qiao
Relaxation dynamics, essential for the structural evolution of non-equilibrium systems like glassy materials, remain enigmatic. Here, we explore relaxation dynamics and viscoelastic properties in three types of metallic glasses with distinct β relaxation behavior. In systems with significant β relaxation, stress relaxation and creep experiments reveal a transition from two-step to one-step relaxation with rising temperature. However, such a phenomenon is absent in systems with weaker β relaxation. We model the two-step relaxation process using a double Kohlrausch-Williams-Watts equation, and the obtained relaxation times elegantly adhere to the Arrhenius relationship. By combining fitted activation energies with theoretical analysis, we conclusively attribute these relaxation processes to β relaxation and α relaxation, respectively. Finally, we analyze the relaxation time spectra of two processes and establish a comprehensive picture linking dynamic relaxation with viscoelasticity. Our study provides new strategies for probing the complex relaxation behaviors of glasses from the perspective of viscoelasticity.
{"title":"Correlating dynamic relaxation and viscoelasticity in metallic glasses","authors":"GuangHui Xing, Qi Hao, Fan Zhu, Yun-Jiang Wang, Yong Yang, Hidemi Kato, Eloi Pineda, Si Lan, JiChao Qiao","doi":"10.1007/s11433-023-2345-3","DOIUrl":"https://doi.org/10.1007/s11433-023-2345-3","url":null,"abstract":"<p>Relaxation dynamics, essential for the structural evolution of non-equilibrium systems like glassy materials, remain enigmatic. Here, we explore relaxation dynamics and viscoelastic properties in three types of metallic glasses with distinct β relaxation behavior. In systems with significant β relaxation, stress relaxation and creep experiments reveal a transition from two-step to one-step relaxation with rising temperature. However, such a phenomenon is absent in systems with weaker β relaxation. We model the two-step relaxation process using a double Kohlrausch-Williams-Watts equation, and the obtained relaxation times elegantly adhere to the Arrhenius relationship. By combining fitted activation energies with theoretical analysis, we conclusively attribute these relaxation processes to β relaxation and α relaxation, respectively. Finally, we analyze the relaxation time spectra of two processes and establish a comprehensive picture linking dynamic relaxation with viscoelasticity. Our study provides new strategies for probing the complex relaxation behaviors of glasses from the perspective of viscoelasticity.</p>","PeriodicalId":774,"journal":{"name":"Science China Physics, Mechanics & Astronomy","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140567994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}