论文标题
MEV时代的宇宙：中微子进化和宇宙学可观察到
The Universe at the MeV era: neutrino evolution and cosmological observables
论文作者
论文摘要
早期宇宙中的中微子物理学是我们对以后宇宙学阶段的理解的关键，例如原始核合成（BBN）或大规模结构的形成。未来十年有望更精确地探索和限制宇宙学模型的新实验结果 - 这需要强大的理论预测。该博士学位论文介绍了大爆炸后的第一秒钟中中微子的演变的研究，更确切地说，当宇宙的温度达到一个mega-electronvolt时。通过求解我们提出新推导的动力学方程来从数值上获得这种进化。第一个应用是计算所谓的“标准”解耦，以计算量化原始相对论物种的能量密度的宇宙学参数，即$ n_ \ mathrm {eff} $，以精确到几分之一。这项研究强调了利用涉及的时间尺度大分离的优势，有效地描述了风味振荡现象的可能性。然后，在中微子和抗肿瘤之间的非零不对称情况下，对这种近似值进行了调整和验证。最后，我们半分析研究了不完全中微子在BBN上的后果，以了解氦气和氘的原始丰度如何受到这种物理学的影响。
Neutrino physics in the early Universe is key to our understanding of later cosmological stages, such as primordial nucleosynthesis (BBN) or the formation of large-scale structures. The coming decade promises new experimental results to explore and constrain cosmological models even more precisely - which requires robust theoretical predictions. This PhD thesis presents a study of the evolution of neutrinos in the first seconds after the Big Bang, more precisely when the temperature of the Universe is of the order of one mega-electronvolt. This evolution is obtained numerically by solving kinetic equations for which we propose a new derivation. A first application is the calculation of the so-called "standard" decoupling in order to calculate the cosmological parameter quantifying the energy density of the primordial relativistic species, $N_\mathrm{eff}$, to a precision of a few ten-thousandths. This study has highlighted the possibility of effectively describing the phenomenon of flavour oscillations, taking advantage of the large separation of time scales involved. Such an approximation is then adapted and validated in the case of non-zero asymmetries between neutrinos and antineutrinos. Finally, we study semi-analytically the consequences of incomplete neutrino decoupling on BBN, in order to understand how the primordial abundances of helium and deuterium are affected by this physics.
