标题： 宇宙学中略微偏斜的应力限制 显示英文标题

标题： Cosmological Limits on Slightly Skew Stresses

摘要： 我们分析了具有小各向异性压力的物质源在宇宙学演化中的行为。 这包括电场和磁场、非碰撞相对论粒子、引力子、低能弦宇宙中的反对称轴子场、空间曲率各向异性以及由简单拓扑缺陷引起的应力。 我们计算了它们在几乎各项同性宇宙的辐射时代和尘埃时代的演化。 在许多有趣的情况下，这种演化表现出一种特殊的临界行为，这是由压力和膨胀各向异性的非线性演化造成的。 微波背景的各向同性被用来对这些物质源可能对宇宙总密度的贡献施加强限制，其中 $\Omega _{a0}\leq 5\times 10^{-6}\Delta (1+z_{rec})^{-\Delta }$表征这种限制的强度，而 $1\leq \Delta \leq 3$ 表征各向异性应力。 我们还计算了在特征低能量尺度下变得非相对论的各向异性应力的当前丰度。 我们解释了为什么从原初核合成获得的限制通常比由微波背景各向同性所施加的限制更弱。 我们也计算了这些应力在暴胀过程中的效应。 显示英文摘要

摘要： We present an analysis of the cosmological evolution of matter sources with small anisotropic pressures. This includes electric and magnetic fields, collisionless relativistic particles, gravitons, antisymmetric axion fields in low-energy string cosmologies, spatial curvature anisotropies, and stresses arising from simple topological defects. We calculate their evolution during the radiation and dust eras of an almost isotropic universe. In many interesting cases the evolution displays a special critical behaviour created by the non-linear evolution of the pressure and expansion anisotropies. The isotropy of the microwave background is used to place strong limits of order $\Omega _{a0}\leq 5\times 10^{-6}\Delta (1+z_{rec})^{-\Delta }$on the possible contribution of these matter sources to the total density of the universe, where $1\leq \Delta \leq 3$ characterises the anisotropic stress. The present abundance of an anisotropic stress which becomes non-relativistic at a characteristic low-energy scale is also calculated. We explain why the limits obtained from primordial nucleosynthesis are generally weaker than those imposed by the microwave background isotropy. The effect of inflation on these stresses is also calculated.