106 citations · 263 across the 5 of their papers we have counts for
9 papers · 1 filter
Precision calculations of the gravitational wave background spectrum from inflation
Sachiko Kuroyanagi, Takeshi Chiba, Naoshi Sugiyama
The spectrum of the gravitational wave background originating from quantum fluctuations during inflation is calculated numerically for various inflation models over a wide range of…
A Null Test of the Cosmological Constant
Takeshi Chiba, Takashi Nakamura
We provide a consistency relation between cosmological observables in general relativity with the cosmological constant. Breaking of this relation at any redshift would imply the b…
A Consistency Relation in Cosmology
Takeshi Chiba, Ryuichi Takahashi
We provide a consistency relation between cosmological observables in general relativity without relying on the equation of state of dark energy. The consistency relation should be…
Solar System constraints to general f(R) gravity
Takeshi Chiba, Tristan L. Smith, Adrienne L. Erickcek
It has been proposed that cosmic acceleration or inflation can be driven by replacing the Einstein-Hilbert action of general relativity with a function f(R) of the Ricci scalar R.…
Classifying the Future of Universes with Dark Energy
Takeshi Chiba, Ryuichi Takahashi, Naoshi Sugiyama
We classify the future of the universe for general cosmological models including matter and dark energy. If the equation of state of dark energy is less then -1, the age of the uni…
Does Positronium Form in the Universe ?
Takeshi Chiba, Naoshi Sugiyama
Positronium (the bound state of electron and positron) has been thought to be formed after proton decay (yr) through collisional recombination and then decays by pair ann…