81 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
Observational signatures of the parametric amplification of gravitational waves during reheating after inflation
We study the evolution of Gravitational Waves (GWs) during and after
inflation as well as the resulting observational consequences in a
Lorentz-violating massive gravity theory with one scalar (inflaton) and two
tensor degrees of freedom. We consider two explicit examples of the tensor mass
that depends either on the inflaton field or on its time
derivative , both of which lead to parametric excitations of GWs
during reheating after inflation. The first example is Starobinsky's
inflation model with a -dependent and the second is a
low-energy-scale inflation model with a -dependent . We
compute the energy density spectrum today of the GW
background. In the Starobinsky's model, we show that the GWs can be amplified
up to the detectable ranges of both CMB and DECIGO, but the bound from the big
bang nucleosynthesis is quite tight to limit the growth. In low-scale inflation
with a fast transition to the reheating stage driven by the potential
around (where is
the reduced Planck mass), we find that the peak position of induced by the parametric resonance can reach the sensitivity region of
advanced LIGO for the Hubble parameter of order 1 GeV at the end of inflation.
Thus, our massive gravity scenario offers exciting possibilities for probing
the physics of primordial GWs at various different frequencies.Comment: 17 pages, 8 figure
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