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众多粒子物理超标准模型中都预言了自旋有关的新相互作用存在. 极化的核子间通过交换自旋为1的轴矢量玻色子可以产生额外的吸引力进而改变无穷大核物质状态方程性质. 本文在相对论平均场模型的框架下加入额外的轴矢量玻色子后计算发现, 当相互作用强度与玻色子质量之比达到
$g_{\rm A}^2/m_{\rm Z'}^2 $ ～${\cal O}(10 \, {\rm GeV^{-2}})$ 时, 低密处无穷大核物质的稳定性和对应的相变行为将发生显著的改变; 而当$g_{\rm A}^2/m_{\rm Z'}^2 > 130 \, {\rm GeV^{-2}}$ 时核物质将在发生相变前率先到达零压点. 对中子星而言这意味着其内核物质将在保持稳定的状态下形成表面而不会发生相变形成壳层结构, 这与普遍存在于中子星天文观测中的星震现象矛盾, 因此反过来对新相互作用的强度提出了额外的限制. 通过与已有的地面实验结果对比, 本文发现对于力程为微米到厘米间的新相互作用, 中子星对其强度的约束最高可有8个量级的提升.It is predicted in many theories beyond the standard model that the new interaction relevant to spin is existent. The exchange of an axial vector particle will result in attractive dipole-dipole interaction which can be viewed as an effective magnetic potential that looks quite different from those expected from electromagnetism. In this work, we demonstrate that, instead of the laboratory spin source, stringent constraints can be set on these attractive spin-spin interactions from polarized nuclear matters within neutron stars which have extremely strong magnetic fields (up to 1015 G in some cases). By considering such an exotic interaction within the framework of relativistic mean field model, we find that the stability of infinite nuclear matter can be influenced significantly when the ratio of coupling strength to boson mass become larger than$g_{\rm A}^2/m_{\rm Z'}^2 \sim {\cal O}(10 \, {\rm GeV^{-2}})$ . Furthermore, based on the curvature matrix approach, when$g_{\rm A}^2/m_{\rm Z'}^2 > 130 \, {\rm GeV^{-2}}$ , phase transition inside low-density nuclear matter will no longer take place before the pressure of nuclear matter becomes zero, which forbids core-crust transition at the inner edge separating the liquid core from the solid crust of neutron stars. Thus bare neutron stars without any crusts are predicted. However, observations of pulsar glitches, i.e., the occasional disruptions of the extremely regular pulsations from magnetized, rotating neutron stars, imply the existence of crusts inside these dense objects. This in turn constrains the strength of the exotic interaction. In fact, in the case of dipole-dipole force on a length scale between µm to cm, the highest value of these constraints can be 8 orders of magnitude higher than those from existing laboratory results.-
Keywords:
- neutron star /
- theories beyond standard model /
- new interactions
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图 1 中子星物质状态方程(能量密度、压强)随重子数密度的变化, 其中轴矢量相互作用的有效耦合常数分别等于
$\bar{g}_{\rm A}^2/m_{\rm Z'}^2 = 0, \; 9.9 $ 和30 GeV–2Fig. 1. Equation of states inside neutron stars as a function of the baryon density for β-stable nuclear matter where the effective couplings to Z' field are
$\bar{g}_{\rm A}^2/m_{\rm Z'}^2 = 0, \; 9.9$ and 30 GeV–2, respectively.
图 2 中子星壳-芯转变密度(
$n_{\rm t}$ )与核物质零压点($n_{\rm c}$ )随$\bar{g}_{\rm A}^2/m_{\rm Z'}^2$ 的变化曲线Fig. 2. Core-crust transition density
$n_{\rm t}$ as well as zero-pressure point density$n_{\rm c}$ of nuclear matter as functions of$\bar{g}_{\rm A}^2/m_{\rm Z'}^2$ .
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[1] ATLAS Collaboration 2012 Phys. Lett. B 716 1
Google Scholar
[2] CMS Collaboration 2012 Phys. Lett. B 716 30
Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
[26] Piegsa F M 2012 Phys. Rev. Lett. 108 181801
Google Scholar
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