231 citations · 1.9k across the 26 of their papers we have counts for
7 papers · 1 filter
A gigaparsec-scale local void and the Hubble tension
Qianhang Ding, Tomohiro Nakama, Yi Wang
We explore the possibility of using a gigaparsec-scale local void to reconcile the Hubble tension. Such a gigaparsec-scale void can be produced by multi-stream inflation where diff…
Ultracompact minihalos associated with stellar-mass primordial black holes
Tomohiro Nakama, Kazunori Kohri, Joseph Silk
The possibility that primordial black hole binary mergers of stellar mass can explain the signals detected by the gravitational-wave interferometers has attracted much attention. I…
Spectral Distortions of the CMB as a Probe of Inflation, Recombination, Structure Formation and Particle Physics
J. Chluba, A. Kogut, S. P. Patil +98
Following the pioneering observations with COBE in the early 1990s, studies of the cosmic microwave background (CMB) have focused on temperature and polarization anisotropies. CMB…
Enhancement of Gravitational Waves Induced by Scalar Perturbations due to a Sudden Transition from an Early Matter Era to the Radiation Era
Keisuke Inomata, Kazunori Kohri, Tomohiro Nakama +1
We study gravitational waves induced from the primordial scalar perturbations at second order around the reheating of the Universe. We consider reheating scenarios in which a trans…
Gravitational Waves Induced by Scalar Perturbations during a Gradual Transition from an Early Matter Era to the Radiation Era
Keisuke Inomata, Kazunori Kohri, Tomohiro Nakama +1
We revisit the effects of an early matter-dominated era on gravitational waves induced by scalar perturbations. We carefully take into account the evolution of the gravitational po…
Gravitational Production of Superheavy Dark Matter and Associated Cosmological Signatures
Lingfeng Li, Tomohiro Nakama, Chon Man Sou +2
We study the gravitational production of super-Hubble-mass dark matter in the very early universe. We first review the simplest scenario where dark matter is produced mainly during…
Detectability of Gravitational Waves from the Coalescence of Massive Primordial Black Holes with Initial Clustering
Qianhang Ding, Tomohiro Nakama, Joseph Silk +1
We show that the effect of initial non-Gaussian clustering can significantly enhance the event rate for primordial black hole (PBH) coalescence. The impact of such clustering is st…