A New Window into Stochastic Gravitational Wave Background
  A stochastic gravitational wave background (SGWB) would gravitationally lens
the cosmic microwave background (CMB) photons. We find that the lensing due to
gravitational waves(GW) is more efficient as compared to lensing due to scalar
density perturbations. Though the effect of lensing due to GW is found to
effect all the four CMB power spectra, its effect is most prominently seen in
the CMB polarization power spectra. This suggests that the measurements of the
CMB angular power spectra could be used to constraining the energy density
($\Omega_{GW}$) of the SGBW. In our analysis we find that the most stringent
constraints on $\Omega_{GW}$ are due to measurements of the angular power
spectra of CMB temperature anisotropies. We show that in the future it will be
possible to place more stringent bounds on $\Omega_{GW}$ using improved upper
limits or detections of the angular power spectra of the B-modes of CMB
polarization at large multipoles.
