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Dark radiation in cosmology

Dark radiation in cosmology. 张益 重庆邮电大学 2011.4.3. Dark Energy! Dark Matter! What is dark radiation ? Observations! Theory!. 宇宙中的组分. 不同组分的演化规律. Friedmann Equation. Radiation. Matter. Cosmological constant. Curvature term. 集中讨论两个加速膨胀阶段. Radiation. 通常 :

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Dark radiation in cosmology

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  1. Dark radiation in cosmology 张益 重庆邮电大学 2011.4.3

  2. Dark Energy! • Dark Matter! • What is dark radiation? Observations! Theory!

  3. 宇宙中的组分

  4. 不同组分的演化规律 FriedmannEquation Radiation Matter Cosmological constant Curvature term

  5. 集中讨论两个加速膨胀阶段

  6. Radiation 通常: 辐射是指静止质量为零的粒子组成的气体 在温度为T的早期宇宙中: 当温度T显著超过粒子静质量m,这种粒子会作为辐射的组分存在; 辐射气体是一切满足m<T的粒子组成的混合气体。

  7. 辐射物质 光子, 正反中微子, 正反电子, 质子和中子

  8. BBN(Big Bang Nucleosynthesis) 热碰撞(1MeV) 温度降到0.1MeV: 电子俘获 碰撞 Next 温度降到0.01MeV, 热核反应结束

  9. The radiation dominating universe

  10. 辐射项对BBN 的影响 有效中微子数目大 宇宙的膨胀率大 弱退耦发生的时间得更早 冻结下来的中子数密度更多 氦的产额更大

  11. CMBR(微波背景辐射) CMBR各向异性可分为: 宇宙早期产生的初级各向异性 从光子退耦到现在产生的二级各向异性

  12. ISW 效应( Integrated Sachs-Wolfe effect ) • 宇宙不是完全均匀的,所以到处存在着引力势阱。当微波背景辐射的光子掉进引力势阱的时候就会获得能量,爬出这个势阱的时候就会损失能量。 • 该效应是光子路径上所有引力势变化的累加效应,称为积分Sachs-Wolfe效应.

  13. 1, 对于一个固定的能量密度 辐射能量密度增加 物质-辐射相等的时刻延迟 ISW效应加强 2, 没有和光子-重子流体耦合的相对论性粒子,可以比声速更快地逃出势阱。

  14. Motivation from Observations • WMAP shows: • BBN Observations limit(68% CL) (astro-ph:0408033) • CMBR (68% CL) (arxiv:1001.4538, 1009.0866) ATACAMA COSMOLOGY TELESCOPE: ACT measures fluctuations at scale 500<l<3000

  15. Possibilities!( astro-ph:0612150,1103.4132) • Motivated by the LSND(Liquid Scintillator Neutrino Detector) oscillation claim,assume a (light) massive sterile neutrino (1006.5276); • The neutrinos acquire a mass from a broken lepton flavor symmetry(astroph:0312267,1009.4666,1011.0911); • Allow for a violation of the spin-statistics theorem; • A Brans-Dicke field with non trivial potential which could mimic the effect of adding extra radiation between the BBN and CMB epochs(astro-ph:0510359); • An extra interaction between the dark energy and radiation (or dark matter); • A quintessence with a tracking potential behavior; • Decaying matter(1011.3501); • Nonstandard thermal history; • ……

  16. Theories • Brane Cosmology • Hovara-Lifshitz cosmology • Electroweak phase transition • EDE(Early Dark Energy) • ………..

  17. Brane Cosmology(astro-ph:0211285) Dark radiation term arises from the projection of Weyl curvature of the bulk black hole on the brane and behaves like an additional collisionless and isotropic massless component.

  18. 其中BBN的限制是 • CMB的限制:把CMB的峰移到高l处 对于

  19. Electroweak phase transition(0902.4699)

  20. Triple coincidence problem • Coincidence problem: why the cosmological constant and the matter have comparable energy density today even through their time evolution is so different • Triple coincidence problem: why the radiation energy density today is only three orders of magnitude smaller than the dark-matter and dark-energy ones, although it also scales very differently

  21. Scalar field dark energy Interaction 1 Interaction 2

  22. Phase-space analysis

  23. Quintessence

  24. Phantom

  25. Conclusion • “Triple coincidence problem”still need fine-tunning。 • This model can recover the history of our universe.

  26. The Future • Data:Planck, BAO, new result on primordial nuclei abundance? • Models: based on string theory, particle physics or others?

  27. THANKS ALL !

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