Detectability of inflation-produced gravitational waves

Abstract

Detection of the gravitational waves excited during inflation as quantum mechanical fluctuations is a key test of inflation and crucial to learning about the specifics of the inflationary model. We discuss the potential of Cosmic Background Radiation (CBR) anisotropy and polarization and of laser interferometers such as LIGO, VIRGO/GEO and LISA to detect these gravity waves.

Figures (4)

• Figure 1: Angular power spectra ($C_l \equiv \langle |a_{lm}|^2\rangle$) of CBR anisotropy for gravity waves (lower curves) and density perturbations (upper curves), normalized to the quadrupole anisotropy; broken lines indicate sampling variance. Temperature fluctuations measured on angular scale $\theta$ are approximately, $(\delta T/T)_\theta \sim \sqrt{l(l+1)C_l/2\pi}$ with $l\sim 200^\circ /\theta$ (courtesy of M. White and U. Seljak).
• Figure 2: Polarization angular power spectra for gravity waves (broken) and density perturbations (solid). The polarization of the CBR anisotropy is roughly $\sqrt{C_l^P/C_l}$ (courtesy of M. White and U. Seljak).
• Figure 3: Spectral energy density in gravity waves produced by inflation; for $T/S = 0.018$, $dn_T/d\ln k = -10^{-3}$, 0, $10^{-3}$. $T/S =0.18$ (heavy curve) maximizes the energy density at $f=10^{-4}\,$Hz. Curves are from Eq. (\ref{['eq:energy']}) using $H_0=60{\rm km\,s^{-1}\,Mpc^{-1}}$, $\Omega_0 =1$, and $g_*=3.36$.
• Figure 4: The range of $T/S$ probed (interval interior to parabola) as a function of energy sensitivity for $f=10^{-4}\,$Hz (solid curves) and $f=100\,$Hz (broken curves). The "pessimistic" (left) parabola assumes $dn_T/d\ln k = -10^{-3}$ and the "optimistic" (right) parabola assumes $dn_T/d\ln k = 10^{-3}$. Also shown are the limiting sensitivity of CBR anisotropy and polarization.