分类： 物理学 >> 核物理学 分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2024-02-29
摘要： It is hypothesized that, though atomic nuclei are made of nucleons, strongly interacting matter with baryon number from $A simeq 10^{3-9}$ to $ sim 10^{57}$ would be composed of strangeons if Nature favors always the flavor symmetry of quarks.According to that logic, strangeon matter with $A sim 10^{57}$ could manifest in the form of pulsar-like compact stars, and multi-messenger observations with advanced facilities (e.g., China’s FAST) could eventually provide a disproof/proof.It is worth emphasizing that this point of view, based on established “old physics”, may have particular consequences for understanding our material world, for both normal luminous matter and the dark sector.
分类： 天文学 >> 天文学 提交时间： 2023-12-18
摘要： The Five-hundred-meter Aperture Spherical radio Telescope (FAST) has discovered more than 650 new pulsars, which account for 20% of our known Galactic pulsar population. In this paper, we estimate the prospect of a pulsar survey with a radio telescope array to be planned -- the FAST Array (FASTA), consists of six FAST-type telescopes. Such a sensitive radio telescope array would be a powerful instrument in probing the pulsar population deep into our Galaxy as well as in nearby galaxies. We simulate the FASTA pulsar discovery prospects with different Galactic pulsar population models and instrumental parameter combinations. We find that FASTA could detect tens of thousands of canonical pulsars and well-over thousands of millisecond pulsars. We also estimate the potential yield if the FASTA is used to search for pulsars from the nearby spiral galaxy M31, and find that it would probably discover around a hundred new radio pulsars.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： A crossover QCD phase transition in the early Universe, involving a formation scenario of stable strangeon nuggets is studied. The Polyakov-Nambu-Jona-Lasinio model is applied to calculate the thermodynamics of the QCD phase with u, d, s quarks, and the relativistic mean-field model describes the hadronic matter. The crossover phase transition from quarks to hadrons occurred at cosmic temperature of T~170 MeV, and those two phases are connected in a three-window model. Due to quark's non-perturbative coupling, quark clusters with net strangeness (i.e., strangeons) and then strangeon nuggets could form during the transition process. A distribution function of the nugget baryon number, A, is introduced to describe the nuggets' number density. All the strangeon nuggets with A>A_c are considered to be stable, where the critical number, A_c, is determined by both the weak and strong interactions. A non-relativistic equation of state is applied to calculate the thermodynamics of stable nuggets. The calculation shows that the thermodynamical contributions (pressure, entropy, etc.) of the stable strangeon nuggets are negligible. The resultant mass density of the strangeon nuggets survival from the early Universe is comparable to the dark matter, that indicates a possible explanation of the cold dark matter without introducing any exotic particles beyond the standard model.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： A crossover QCD phase transition in the early Universe, involving a formation scenario of stable strangeon nuggets is studied. The Polyakov-Nambu-Jona-Lasinio model is applied to calculate the thermodynamics of the QCD phase with u, d, s quarks, and the relativistic mean-field model describes the hadronic matter. The crossover phase transition from quarks to hadrons occurred at cosmic temperature of T~170 MeV, and those two phases are connected in a three-window model. Due to quark's non-perturbative coupling, quark clusters with net strangeness (i.e., strangeons) and then strangeon nuggets could form during the transition process. A distribution function of the nugget baryon number, A, is introduced to describe the nuggets' number density. All the strangeon nuggets with A>A_c are considered to be stable, where the critical number, A_c, is determined by both the weak and strong interactions. A non-relativistic equation of state is applied to calculate the thermodynamics of stable nuggets. The calculation shows that the thermodynamical contributions (pressure, entropy, etc.) of the stable strangeon nuggets are negligible. The resultant mass density of the strangeon nuggets survival from the early Universe is comparable to the dark matter, that indicates a possible explanation of the cold dark matter without introducing any exotic particles beyond the standard model.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shi Dai
Jiguang Lu
Chen Wang
Weiyang Wang
Renxin Xu
Yuanpei Yang
Songbo Zhang
George Hobbs
Di Li
Rui Luo
Miroslav Filipovic
Jinchen Jiang
摘要： Fast spinning (e.g., sub-second) neutron star with ultra-strong magnetic fields (or so-called magnetar) is one of the promising origins of repeating fast radio bursts (FRBs). Here we discuss circularly polarised emissions produced by propagation effects in the magnetosphere of fast spinning magnetars. We argue that the polarisation-limiting region is well beyond the light cylinder, suggesting that wave mode coupling effects are unlikely to produce strong circular polarisation for fast spinning magnetars. Cyclotron absorption could be significant if the secondary plasma density is high. However, high degrees of circular polarisation can only be produced with large asymmetries in electrons and positrons. We draw attention to the non-detection of circular polarisation in current observations of known repeating FRBs. We suggest that the circular polarisation of FRBs could provide key information on their origins and help distinguish different radiation mechanisms.
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