Big Bang Nucleosynthesis, the CMB, and the Origin of Matter and Space-Time
Grant.J.Mathews, Mayukh Gangopadhyay, Nishanth Sasankan, Kiyotomo, Ichiki, Toshitaka Kajino

TL;DR
This paper reviews how big bang nucleosynthesis and the cosmic microwave background constrain early universe physics, including higher dimensions, inflation, and potential evidence of superstring excitations in the CMB.
Contribution
It introduces novel constraints on higher-dimensional models, inflationary parameters, and proposes a method to detect superstring signatures in the CMB power spectrum.
Findings
Constraints on dark radiation from BBN and CMB.
Impact of extra dimensions on inflationary parameters.
Potential observational signatures of superstring excitations in the CMB.
Abstract
We summarize some applications of big bang nucleosythesis (BBN) and the cosmic microwave background (CMB) to constrain the first moments of the creation of matter in the universe. We review the basic elements of BBN and how it constraints physics of the radiation-dominated epoch. In particular, how the existence of higher dimensions impacts the cosmic expansion through the projection of curvature from the higher dimension in the "dark radiation" term. We summarize current constraints from BBN and the CMB on this brane-world dark radiation term. At the same time, the existence of extra dimensions during the earlier inflation impacts the tensor to scalar ratio and the running spectral index as measured in the CMB. We summarize how the constraints on inflation shift when embedded in higher dimensions. Finally, one expects that the universe was born out of a complicated multiverse landscape…
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