暗物质或因宇宙中某种不稳定所致

正希格斯场的不稳定性可能导致原初黑洞的形成。这类黑洞也许正在充当暗物质。理论家推测希格斯场正处亚稳态,因而我们的宇宙可能位于希格斯深渊的边缘。如果希格斯场隧穿至"真正的"基态,将释放巨大能量。这有点危言耸听,或许其他未知物理过程还会保障宇宙在历史上稳定。不过,导致暗物质的形成亦可能是希格斯场不稳定性的宇宙学后果之一。这一构想认为,暗物质其实就是宇宙早期经过不稳定希格斯场涨落而形成的那些黑     

钱德拉塞卡和白矮星

1983年,73岁的钱德拉塞卡（Chandrasekhar）获得当年的诺贝尔物理学奖。得奖主要原因是他在恒星结构和演化领域所做的贡献,即对白矮星质量上限的研究。这部分工作,是他本人在20世纪30年代完成的,距获奖时隔50年。当时媒体称此为钱德拉塞卡“迟来的春天”。21世纪的今天,当我们再度回顾这段历史,深感带给人们的启发还是相当深刻的。     

中子星内部结构

中子星是宇宙中一类极端致密的天体,其平均密度超过饱和核物质密度。对这类天体的研究,可以帮助人们了解极端条件下的物理性质,特别是深化关于引力和强力的认识。文章介绍了脉冲星和中子星的概念,并重点阐述了中子星内部结构的不同模型,以及如何通过最大质量和潮汐形变量等观测来检验这些模型。未来发现更多的双中子星并合或中子星黑洞并合事件,有望最终揭开中子星内部结构之谜。     

在黑洞附近检验万有引力

<正>射手座A*是位于银河系中心的一颗巨型黑洞,其强大的引力为人们提供了一个理想的场所来检验引力理论(包括广义相对论GR)。之前人们往往用较低质量的天体(如太阳或白矮星)作这类检验,而现在GRAVITY合作组则用围绕射手座A*黑洞做轨道运动的恒星来检验。尽管科学家再三证实了GR的     

Quark-clustering in cold quark matter

Quarks are proposed to be grouped together to make quark-clusters due to the strong interaction in cold quark matter at a few nuclear densities,because a weakly coupling treatment of the interaction between quarks there would be inadequate.Cold quark matter is then conjectured to be in solid state （i.e.,forming a crystal structure） if the inter-cluster potential is deep enough to localize clusters in lattice.Such a solid state of cold quark matter would be very necessary for us to understand different manifestations of pulsar-like compact stars,and could not be ruled by first principles.     

在遗忘之前，记忆变得模糊和混乱

<正>大脑信息存储模型揭示了记忆如何随着年龄增长而衰退。理论上构建的“吸引子网络”(attractor networks)可用于模拟大脑的记忆。基于该网络的一项研究再现了记忆存储并被最终遗忘的过程。计算模拟表明,随着年龄的增长,保留记忆的神经活动图案变得混乱,无法预测,最终成为随机噪声。虽然大脑中是否会真的如此尚不清楚,     

A new parametric equation of state and quark stars

It is still a matter of debate to understand the equation of state of cold matter with supra-nuclear density in compact stars because of unknown non-perturbative strong interaction between quarks. Nevertheless, it is speculated from an astrophysical view point that quark clusters could form in cold quark matter due to strong coupling at realistic baryon densities. Although it is hard to calculate this conjectured matter from first principles, one can expect that the inter-cluster interaction will share some general features with the nucleon-nucleon interaction successfully depicted by various models. We adopt a two-Gaussian component soft-core potential with these general features and show that quark clusters can form stable simple cubic crystal structure if we assume that the wave function of quark clusters have a Gaussian form. With this parametrization, the Tolman-Oppenheimer-Volkoff equation is solved with reasonably constrained parameter space to give mass-radius relations of crystalline solid quark stars. With baryon number densities truncated at 2_n0 at surface and the range of the interaction fixed at 2 fm we can reproduce similar mass-radius relations to that obtained with bag model equations of state. The maximum mass ranges from 0.5M_⊙ to 3M_⊙. The recently measured high pulsar mass ( 2M_⊙) is then used to constrain the parameters of this simple interaction potential.     

A corresponding-state approach to quark-cluster matter~

The state of super-dense matter is essential for us to understand the nature of pulsars; however, non-perturbative quantum chromodynamics makes it very difficult to make direct calculations of the state of cold matter at realistic baryon number densities inside compact stars. Nevertheless, from an observational point of view, it is conjectured that pulsars could be made up of quark clusters since the strong coupling between quarks might render the quarks to be grouped in clusters. In this paper, we attempt to find an equation of state of condensed quark-cluster matter in a phenomenological way. Supposing that the quark-clusters could be analogized to inert gases, we apply here the corresponding-state approach to derive the equation of state of quark-cluster matter, as was similarly demonstrated for nuclear and neutron-star matter in the 1970s. According to the calculations that we have presented, the quark-cluster stars, which are composed of quark-cluster matter, could have a high maximum mass that is consistent with observations and, in turn, further observations of pulsar mass could also place a constraint on the properties of quark-cluster matter. We will also briefly discuss the melting heat during the solid-liquid phase conversion and its related astrophysical consequences.     

宇宙双折射?

微波背景辐射(CMB)是宇宙中最古老的光,其偏振越来越受到关注,以寻求新物理的迹象.偏振方向的微小旋转即为一种征兆,正如光经过不同偏振方向折射率有异的双折射材料那样.这种"宇宙双折射"未被标准模型预言,可能是由CMB光子跟假想的粒子和场耦合所致.已有的实验尚未发现双折射,但实验灵敏度受到系统误差的限制.