4 papers
Imprints of flat space analyticity in de Sitter S-matrix
Jason Kristiano, Ryo Namba, Atsushi Naruko +2
The analytic structure of the flat-space S-matrix provides non-perturbative constraints on low-energy effective field theories based on the properties of high-energy theory. While…
Exact WKB Formulation of Quantization and Particle Production in Time-Dependent Backgrounds
Ryo Namba, Motoo Suzuki
Divergence in perturbative expansions is where interesting physics takes place. Particle production on time-dependent backgrounds, as one such example, is interpreted as transition…
Bispectrum from inflation/bouncing Universe in VCDM
Alexander Ganz, Paul Martens, Shinji Mukohyama +1
We discuss the non-linear interactions within the VCDM model, a type II minimally modified gravity model with the same number of degrees of freedom as in General Relativity but not…
Can we explain cosmic birefringence without a new light field beyond Standard Model?
Yuichiro Nakai, Ryo Namba, Ippei Obata +2
The recent analysis of the Planck 2018 polarization data shows a nonzero isotropic cosmic birefringence (ICB) that is not explained within the CDM paradigm. We then explore the…