934 citations · 12.9k across the 205 of their papers we have counts for
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Large gauge transformation, Soft theorem, and Infrared divergence in inflationary spacetime
Takahiro Tanaka, Yuko Urakawa
It is widely known that the primordial curvature perturbation has several universal properties in the infrared (IR) such as the soft theorem, which is also known as the consist…
Vacuum State of the Dirac Field in de Sitter Space and Entanglement Entropy
Sugumi Kanno, Misao Sasaki, Takahiro Tanaka
We compute the entanglement entropy of a free massive Dirac field between two causally disconnected open charts in de Sitter space. We first derive the Bunch-Davies vacuum mode fun…
Primordial fluctuations from inflation in dRGT bimetric theory of gravity
Yuki Sakakihara, Takahiro Tanaka
We investigate primordial gravitational waves and curvature perturbations in de Rham-Gabadadze-Tolley (dRGT) bimetric gravity. We evaluate the power-spectra in the leading order in…
Conservation of with radiative corrections from heavy field
Takahiro Tanaka, Yuko Urakawa
In this paper, we address a possible impact of radiative corrections from a heavy scalar field on the curvature perturbation . Integrating out , we derive the effective a…
Bigravity from gradient expansion
Yasuho Yamashita, Takahiro Tanaka
We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The…
Effective theory of Black Holes in the 1/D expansion
Roberto Emparan, Tetsuya Shiromizu, Ryotaku Suzuki +2
The gravitational field of a black hole is strongly localized near its horizon when the number of dimensions D is very large. In this limit, we can effectively replace the black ho…
Appearance of Boulware-Deser ghost in bigravity with doubly coupled matter
Yasuho Yamashita, Antonio De Felice, Takahiro Tanaka
We discuss the ghost freeness in the case when we add matter coupled to two metrics to the ghost-free bigravity. In this paper we show that the Boulware-Deser ghost generally reviv…
Viable cosmology in bimetric theory
Antonio De Felice, A. Emir Gumrukcuoglu, Shinji Mukohyama +2
We study cosmological perturbations in bimetric theory with two fluids each of which is coupled to one of the two metrics. Focusing on a healthy branch of background solutions, we…
Strong restriction on inflationary vacua from the local gauge invariance III: Infrared regularity of graviton loops
Takahiro Tanaka, Yuko Urakawa
It has been claimed that the super Hubble modes of the graviton generated during inflation can make loop corrections diverge. Even if we introduce an infrared (IR) cutoff at a como…
Schwinger effect in de Sitter space
Markus B. Fröb, Jaume Garriga, Sugumi Kanno +4
We consider Schwinger pair production in 1+1 dimensional de Sitter space, filled with a constant electric field . This can be thought of as a model for describing false vacuum d…
Mapping de Rham-Gabadadze-Tolley bigravity into braneworld setup
Yasuho Yamashita, Takahiro Tanaka
We discuss whether or not bigravity theory can be embedded into the braneworld setup. As a candidate, we consider Dvali-Gabadadze-Porrati two-brane model with the Goldberger-Wise r…
Loops in inflationary correlation functions
Takahiro Tanaka, Yuko Urakawa
We review the recent progress regarding the loop corrections to the correlation functions in the inflationary universe. A naive perturbation theory predicts that loop corrections g…
Rest frame of bubble nucleation
Jaume Garriga, Sugumi Kanno, Takahiro Tanaka
Vacuum bubbles nucleate at rest with a certain critical size and subsequently expand. But what selects the rest frame of nucleation? This question has been recently addressed in [1…
Strong restriction on inflationary vacua from the local gauge invariance II: Infrared regularity and absence of the secular growth in Euclidean vacuum
Takahiro Tanaka, Yuko Urakawa
We investigate the initial state of the inflationary universe. In our recent publications, we showed that requesting the gauge invariance in the local observable universe to the in…
Strong restriction on inflationary vacua from the local gauge invariance I: Local gauge invariance and infrared regularity
Takahiro Tanaka, Yuko Urakawa
The primordial perturbation is widely accepted to be generated through the vacuum fluctuation of the scalar field which drives inflation. It is, however, not completely clear what…
Chiral Phase Transitions around Black Holes
Antonino Flachi, Takahiro Tanaka
In this paper we discuss the possibility that chiral phase transitions, analogous to those of QCD, occur in the vicinity of a black hole. If the black hole is surrounded by a gas o…
Black holes in braneworld models
Norihiro Tanahashi, Takahiro Tanaka
In this review, we summarize current understandings of black hole solutions in various braneworld models, including the Arkani-Hamed-Dimopoulos-Dvali model, the Randall-Sundrum (RS…
Open inflation in the landscape
Daisuke Yamauchi, Andrei Linde, Atsushi Naruko +2
Open inflation scenario is attracting a renewed interest in the context of string landscape. Since there are a large number of metastable de Sitter vacua in string landscape, tunne…
Chiral Modulations in Curved Space I: Formalism
Antonino Flachi, Takahiro Tanaka
The goal of this paper is to present a formalism that allows to handle four-fermion effective theories at finite temperature and density in curved space. The formalism is based on…
Natural selection of inflationary vacuum required by infra-red regularity and gauge-invariance
Yuko Urakawa, Takahiro Tanaka
It has been an issue of debate whether the inflationary infrared(IR) divergences are physical or not. Our claim is that, at least, in single-field models, the answer is "No," and t…
IR divergence does not affect the gauge-invariant curvature perturbation
Yuko Urakawa, Takahiro Tanaka
We address the infrared(IR) divergence problem during inflation that appears in the loop corrections to the primordial perturbations. In our previous paper, we claimed that, at lea…
Casimir Effect on the brane
Antonino Flachi, Takahiro Tanaka
We consider the Casimir effect between two parallel plates localized on a brane. In order to properly compute the contribution to the Casimir energy due to any higher dimensional f…
On the full trispectrum in single field DBI-inflation
Frederico Arroja, Shuntaro Mizuno, Kazuya Koyama +1
We compute the tree-level connected four-point function of the primordial curvature perturbation for a fairly general minimally coupled single field inflationary model, where the i…
Lorentz boost and non-Gaussianity in multi-field DBI-inflation
Shuntaro Mizuno, Frederico Arroja, Kazuya Koyama +1
We show that higher-order actions for cosmological perturbations in the multi-field DBI-inflation model are obtained by a Lorentz boost from the rest frame of the brane to the fram…