64 research outputs found
Prospects for determination of thermal history after inflation with future gravitational wave detectors
Thermal history of the Universe between inflation and big-bang
nucleosynthesis has not yet been revealed observationally. It will be probed by
the detection of primordial gravitational waves generated during inflation,
which contain information on the reheating temperature as well as the equation
of state of the Universe after inflation. Based on Fisher information
formalism, we examine how accurately the tensor-to-scalar ratio and reheating
temperature after inflation can be simultaneously determined with space-based
gravitational wave detectors such as the DECI-hertz Interferometer
Gravitational-wave Observatory (DECIGO) and the Big-Bang Observer (BBO). We
show that the reheating temperature is best determined if it is around 10^7 GeV
for tensor-to-scalar ratio of around 0.1, and explore the detectable parameter
space. We also find that equation of state of the early Universe can be also
determined accurately enough to distinguish different equation-of-state
parameters if the inflationary gravitational waves are successfully detected.
Thus future gravitational wave detectors provide a unique and promising
opportunity to reveal the thermal history of the Universe around 10^7 GeV.Comment: 21 pages, 8 figure
Gravitational waves as a probe of dark matter mini-spikes
Recent studies show that an intermediate mass black hole (IMBH) may develop a
dark matter (DM) mini-halo according to some BH formation scenarios. We
consider a binary system composed of an IMBH surrounded by a DM mini-spike and
a stellar mass object orbiting around the IMBH. The binary evolves due to
gravitational pull and dynamical friction from the DM mini-spike and
back-reaction from its gravitational wave (GW) radiation which can be detected
by future space-borne GW experiments such as eLISA/NGO. We consider a single
power-law model for the DM mini-spike which is assumed to consist of
non-annihilating DM particles and demonstrate that an eLISA/NGO detection of GW
from such a binary enables us to measure the DM mini-spike parameters very
accurately. For instance, in our reference case originally advocated by Zhao
and Silk (2005) and Bertone et al. (2005), we could determine the power-law
index of the DM mini-spike radial profile with a 1 relative
error of for a GW signal with signal-to-noise-ratio 10
and assuming a 5 year observation with eLISA. We also investigate how
accurately the DM parameters can be determined for various DM parameters and
the masses of the IMBH-stellar mass object binary surrounded by a DM
mini-spike. We find that we can determine the power-law index at 10 %
level even for a slightly flatter radial distribution of .Comment: 19 pages, 8 figure
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