This thesis is dedicated to the exploration of the primordial dark ages: unknown physics during the earliest stages of the Universe’s expansion that have not yet been directly probed by... Show moreThis thesis is dedicated to the exploration of the primordial dark ages: unknown physics during the earliest stages of the Universe’s expansion that have not yet been directly probed by observations. Cosmic inflation is a burst of exponential expansion of space after the “Big Bang”. The energy that drives inflation must be transferred to elementary particles and radiation. This process is called reheating. The unknown expansion history of the universe during the reheating era connects the cosmic microwave background (CMB) observations to inflationary physics. CMB is a relic radiation that provides us a snapshot of the primordial universe. Both the inflationary and reheating eras generate signatures to be seen via upcoming gravitational waves and CMB polarization experiments. In this thesis we show analytically a scaling behaviour that allows for an easy estimate of the reheating efficiency for one broad family of multi-field models of inflation that is called α-attractors. We show the influence of the asymmetry around the minimum of potential on the reheating efficiency. Moreover, we study the predictions for chiral gravitational waves production by a spectator gauge field sector in scalar single-field inflation. Finally, we present a new class of inflationary models that is called “shift-symmetric orbital inflation”. Show less
In the early universe, the dynamics of the Higgs field can give rise to many interesting phenomena. In the first part of this thesis, we study the behavior of the Higgs field during the reheating... Show moreIn the early universe, the dynamics of the Higgs field can give rise to many interesting phenomena. In the first part of this thesis, we study the behavior of the Higgs field during the reheating phase after cosmological inflation. We investigate the stability of the electroweak vacuum when the Higgs field is nonminimally coupled to gravity. We also study reheating in the scenario where the Higgs field itself drives inflation. In the second part, we study the possibility of generating the asymmetry between matter and antimatter during the electroweak phase transition -- the moment when the Higgs field starts to give mass to the other particles of the Standard Model. We show that it is not possible to constrain this process in a model-independent way. We also demonstrate that the predicted value of the baryon asymmetry is enhanced when leptons are included in the computation. Show less
