Speaker
Dr
Takahiro Terada
(KEK)
Description
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 transition from an early
matter dominated era to the radiation dominated era completes within a
timescale much shorter than the Hubble time at that time. We find that
an enhanced production of induced gravitational waves occurs just
after the reheating transition because of fast oscillations of
scalar modes well inside the Hubble horizon. This enhancement
mechanism just after an early matter-dominated era is much more
efficient than a previously known enhancement mechanism during an
early matter era, and we show that the induced gravitational
waves could be detectable by future observations if the reheating
temperature $T_{\text{R}}$ is in the range
$T_\text{R}$ \lesssim $7\times 10^{-2} \, \text{GeV}$ or
$20 \, \text{GeV}$ \lesssim $T_\text{R}$ \lesssim 2 $\times 10^7 \, \text{GeV}$.
This is the case even if the scalar perturbations on small scales are
not enhanced relative to those on large scales, probed by the
observations of the cosmic microwave background.
This talk will be based on our paper, arXiv:1904.12879.
Primary author
Dr
Takahiro Terada
(KEK)
Co-authors
Prof.
Kazunori Kohri
(KEK)
Mr
Keisuke Inomata
(ICRR, The University of Tokyo)
Dr
Tomohiro Nakama
(Hong Kong University of Science and Technology)