57 citations · 332 across the 19 of their papers we have counts for
19 papers
Semiclassical analysis of axion-assisted and axion-driven pair production
Hiroyuki Kitamoto, Masaki Yamada
We study the pair production of fermions in a time dependent axion background with and without an electric background. We construct the adiabatic mode functions which incorporate t…
Holographic beta function in de Sitter space
Yoshihisa Kitazawa
The scale invariance of the universe is slightly broken by slow roll parameters. It is likely the slow roll is dual to the random walk. We investigate the distribution function of…
No-go theorem of anisotropic inflation via Schwinger mechanism
Hiroyuki Kitamoto
In the presence of a dilatonic coupling between an inflaton and a gauge field, a persistent electric field (i.e., an anisotropic inflation) is obtained as a solution of the…
Holographic function in de Sitter space
Hiroyuki Kitamoto, Yoshihisa Kitazawa
We investigate infrared logarithms in de Sitter space from holographic perspective. We employ a gravitational Fokker-Planck equation to investigate the time evolution of the de Sit…
de Sitter duality and logarithmic decay of dark energy
Hiroyuki Kitamoto, Yoshihisa Kitazawa, Takahiko Matsubara
We investigate infrared dynamics of four-dimensional Einstein gravity in de Sitter space. We set up a general framework to investigate dynamical scaling relations in quantum/classi…
Entropy Generation at the Horizon Diffuses Cosmological Constant in 2D de Sitter Space
Hiroyuki Kitamoto, Yoshihisa Kitazawa
We investigate a solution of the exactly renormalized Liouville action to foresee the fate of the two-dimensional de Sitter space. We work in the semiclassical region with a large…
Infrared resummation for derivative interactions in de Sitter space
Hiroyuki Kitamoto
In de Sitter space, scale invariant fluctuations give rise to infrared logarithmic corrections to physical quantities, which eventually spoil perturbation theories. For models with…
Schwinger Effect in Inflaton-Driven Electric Field
Hiroyuki Kitamoto
In a four dimensional inflation theory, a persistent electric field can be established by making the inflaton coupled to the gauge field like a dilaton. We investigate the pair pro…
Non-Gaussian and loop effects of inflationary correlation functions in BRST formalism
Hiroyuki Kitamoto, Yoshihisa Kitazawa, Ryota Kojima
We investigate inflationary correlation functions in single field inflation models. We adopt a BRST formalism where locality and covariance at the sub-horizon scale are manifest. T…
Effective Lagrangian in de Sitter Spacetime
Hiroyuki Kitamoto, Yoshihisa Kitazawa
Scale invariant fluctuations of metric are universal feature of quantum gravity in de Sitter spacetime. We construct an effective Lagrangian which summarizes their implications on…
Stochastic Dynamics of Infrared Fluctuations in Accelerating Universe
Gihyuk Cho, Cook Hyun Kim, Hiroyuki Kitamoto
We extend investigations of infrared dynamics in accelerating universes. In the presence of massless and minimally coupled scalar fields, physical quantities may acquire growing ti…
Time Dependent Couplings as Observables in de Sitter Space
Hiroyuki Kitamoto, Yoshihisa Kitazawa
We summarize and expand our investigations concerning the soft graviton effects on microscopic matter dynamics in de Sitter space. The physical couplings receive IR logarithmic cor…
Soft gravitational effects in Kadanoff-Baym approach
Hiroyuki Kitamoto, Yoshihisa Kitazawa
In de Sitter space, the gravitational fluctuation at the super-horizon scale may make physical quantities time dependent by breaking the de Sitter symmetry. We adopt the Kadanoff-B…
Scheme dependence of quantum gravity on de Sitter background
Hiroyuki Kitamoto, Yoshihisa Kitazawa
We extend our investigation of the IR effects on the local dynamics of matter fields in quantum gravity. Specifically we clarify how the IR effects depend on the change of the quan…
Soft Graviton effects on Gauge theories in de Sitter Space
Hiroyuki Kitamoto, Yoshihisa Kitazawa
We extend our investigation of soft graviton effects on the microscopic dynamics of matter fields in de Sitter space. We evaluate the quantum equation of motion in generic gauge th…
Soft Gravitons Screen Couplings in de Sitter Space
Hiroyuki Kitamoto, Yoshihisa Kitazawa
The scale invariance of the quantum fluctuations in de Sitter space leads to the appearance of de Sitter symmetry breaking infra-red logarithms in the graviton propagator. We inves…
Infra-red effects of Non-linear sigma model in de Sitter space
Hiroyuki Kitamoto, Yoshihisa Kitazawa
We extend our investigation on a possible de Sitter symmetry breaking mechanism in non-linear sigma models. The scale invariance of the quantum fluctuations could make the cosmolog…
Non-linear sigma model in de Sitter space
Hiroyuki Kitamoto, Yoshihisa Kitazawa
We investigate infra-red dynamics of the non-linear sigma model in de Sitter space. In the presence of minimally coupled massless scalar fields, the de Sitter symmetry is dynamical…
Boltzmann equation in de Sitter space
Hiroyuki Kitamoto, Yoshihisa Kitazawa
In a time dependent background like de Sitter space, Feynman-Dyson perturbation theory breaks down due to infra-red divergences. We investigate an interacting scalar field theory i…