In this work the accelerated-decelerated transition in a primordial Universe is investigated by using the dynamics of fermion fields within the context of Einstein-Cartan theory, where apart from the curvature the space-time is also described by a torsion field. The model analyzed here has only a fermion field as the source of the gravitational field. The term associated with the spin of the fermion field plays the role of the inflaton which contributes to an accelerated regime whereas the one related to the fermion mass behaves as a matter field and is the responsible for a decelerated regime. Hence, by taking into account the spin of a massive fermion field it is possible to characterize the transition from the accelerated to the decelerated periods of the primordial Universe.
Cosmological magnetic helicity and birefrigence from primordial torsion in Lorentz violation theories
宇宙学磁螺旋度被认为是宇宙中磁场放大的基本因素。最近Semikoz和Sokoloff [Phys Rev Lett 92（2004）：131.301.]表明种子场的弱并不一定意味着磁宇宙螺旋度的弱。本文推导了Riemann-Cartan时空中基于平扭光子非最小耦合的发电机方程。从这个推导，我们可以从宇宙学的磁螺旋度，计算出一个平坦的扭转场产生银河发电机种子的必要条件。这个发电机方程的一个特点是电阻率依赖于Ricci标量曲率。这一特征也存在于湍流发电机模型中。这里的有效电导率是利用$R(Γ)F^{2}$拉格朗日的平扭模得到的，其中R是指Ricci-Cartan时空。计算了磁场的功率谱。光子的双折射与挠率的半极小耦合自然地产生洛伦兹破坏。尽管Dobado和Maroto [Mod Phys Lett A 12：3003（1997）]之前已经研究了原始扭转在光传播各向异性中的作用，但他们使用QED拉格朗日的费米子部分进行了研究，而我们使用光子部分获得了类似的结果。他们也使用了伪挠迹，而我们这里用挠迹本身来计算。
A Unified Fermionic Origin for Density-Driven Waterfall Inflation and its Multi-Messenger Signatures
Leung Center for Cosmology and Particle Astrophysics, National Taiwan University（台湾大学梁氏宇宙学与粒子天体物理中心）；Department of Physics and Graduate Institute of Astrophysics, National Taiwan University（台湾大学物理系及天体物理研究所）；Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford University（斯坦福大学SLAC国家加速器实验室卡弗里粒子天体物理与宇宙学研究所）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Center for Field Theory and Particle Physics & Department of Physics, Fudan University（复旦大学场论与粒子物理中心及物理系）；Center for Astronomy and Astrophysics, Fudan University（复旦大学天体物理中心）；Laboratori Nazionali di Frascati INFN（INFN弗拉斯卡蒂国家实验室）；INFN sezione Roma Tor Vergata（INFN罗马托维加塔分部）；Asia Pacific Center for Theoretical Physics（亚太理论物理中心）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo（东京大学前沿研究院宇宙物理数学卡弗里研究所（WPI））；Center for Gravitational Physics, Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理中心引力物理中心）
