Zobrazeno 1 - 10
of 129
pro vyhledávání: '"Namba, Ryo"'
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 connected to the latter by field redefinitions. During an inflationar
Externí odkaz:
http://arxiv.org/abs/2407.02882
Publikováno v:
J. High Energ. Phys. 2024, 57 (2024)
The recent analysis of the Planck 2018 polarization data shows a nonzero isotropic cosmic birefringence (ICB) that is not explained within the $\Lambda$CDM paradigm. We then explore the question of whether the nonzero ICB is interpreted by the framew
Externí odkaz:
http://arxiv.org/abs/2310.09152
We construct an asymmetric bouncing scenario within the VCDM model - also known as type-II minimally modified gravity -, a modified gravity theory with two local physical degrees of freedom. The scenario is exempt of any ghost or gradient instability
Externí odkaz:
http://arxiv.org/abs/2212.13561
We explore a mechanism to produce a light dark photon dark matter through a coupling between the dark photon field and a spectator scalar field which plays no role in the inflationary expansion of the Universe while rolling down its potential during
Externí odkaz:
http://arxiv.org/abs/2212.11516
We present a cosmological model of an early-time scenario that incorporates a relaxation process of the would-be large vacuum energy, followed by a reheating era connecting to the standard hot big bang universe. Avoiding fine-tuning the cosmological
Externí odkaz:
http://arxiv.org/abs/2205.11754
Publikováno v:
Phys. Rev. D 105, 103518 (2022)
We prove the universality of predictions for linear perturbations from the entire class of models of inflation driven by a pseudo-scalar field coupled to an SU($N$) gauge boson, where SU($2$) subgroups in the SU($N$) crossed with the background spati
Externí odkaz:
http://arxiv.org/abs/2203.03977
We show how a class of multi-field scalar-field theories in a Lorentz-breaking background imposes consistency conditions on its effective theory of a single field and provides an example of order-unity violation of a naively applied positivity bound,
Externí odkaz:
http://arxiv.org/abs/2107.01755
Autor:
Shiga, Mihiro, Asari, Masaru, Takahashi, Yuta, Isozaki, Shotaro, Hoshina, Chisato, Mori, Kanae, Namba, Ryo, Okuda, Katsuhiro, Shimizu, Keiko
Publikováno v:
In Legal Medicine March 2024 67
Autor:
Mukohyama, Shinji, Namba, Ryo
The $k$-essence theory is a prototypical class of scalar-field models that already gives rich phenomenology and has been a target of extensive studies in cosmology. General forms of shift-symmetric $k$-essence are known to suffer from formation of ca
Externí odkaz:
http://arxiv.org/abs/2010.09184
Autor:
Namba, Ryo, Suzuki, Motoo
Publikováno v:
Phys. Rev. D 102, 123527 (2020)
The coherent oscillation of axionic fields naturally drives copious production of dark photon particles in the early universe, due to resonance and tachyonic enhancement. During the process, energy is abruptly transferred from the former to the latte
Externí odkaz:
http://arxiv.org/abs/2009.13909