D. Baskaran

Imprints of relic gravitational waves in cosmic microwave background radiation

A strong variable gravitational field of the very early Universe inevitably generates relic gravitational waves by amplifying their zero-point quantum oscillations. We begin our discussion by contrasting the concepts of relic gravitational waves and inflationary “tensor modes”. We explain and summarize the properties of relic gravitational waves that are needed to derive their effects on cosmic microwave background (CMB) temperature and polarization anisotropies. The radiation field is characterized by four invariants I, V, E, B. We reduce the radiative transfer equations to a single integral equation of Voltairre type and solve it analytically and numerically. We formulate the correlation functions ClXX′ for X, X′=T, E, B and derive their amplitudes, shapes and oscillatory features. Although all of our main conclusions are supported by exact numerical calculations, we obtain them, in effect, analytically by developing and using accurate approximations. We show that the TE correlation at lower l’s must be negative (i.e. an anticorrelation), if it is caused by gravitational waves, and positive if it is caused by density perturbations. This difference in TE correlation may be a signature more valuable observationally than the lack or presence of the BB correlation, since the TE signal is about 100 times stronger than the expected BB signal. We discuss the detection by WMAP of the TE anticorrelation at l≈30 and show that such an anticorrelation is possible only in the presence of a significant amount of relic gravitational waves (within the framework of all other common assumptions). We propose models containing considerable amounts of relic gravitational waves that are consistent with the measured TT, TE and EE correlations.

Observing gravitational wave bursts in pulsar timing measurements

ABSTRACT We propose a novel method for observing the gravitational wave signature of super-massive black hole (SMBH) mergers. This method is based on detection of a specifictype of gravitational waves, namely gravitational wave burst with memory (BWM),using pulsar timing. We study the unique signature produced by BWM in anomalouspulsar timing residuals. We show that the present day pulsar timing precision allowsone to detect BWM due to SMBH mergersfrom distances up to 1 Gpc (forcase ofequalmass 10 8 M ⊙ SMBH). Improvements in precision of pulsar timing together with theincrease in number of observed pulsars should eventually lead to detection of a BWMsignal due to SMBH merger, thereby making the proposed technique complementaryto the capabilities of the planned LISA mission.Key words: gravitational waves – galaxies: evolution – (stars:) pulsars: general –cosmology: miscellaneous 1 INTRODUCTIONThe prospects of detecting gravitational waves (GWs) in the coming decade are looking ever more promising (Grishchuk et al.2001; Cutler & Thorne 2002; Sathyaprakash & Schutz 2009). There is currently a considerable experimental effort to detectgravitational waves in a wide range of frequencies. At high frequencies ν ∼ 10

Detecting relic gravitational waves in the CMB: Optimal parameters and their constraints

The prospect of detecting relic gravitational waves, through their imprint in the cosmic microwave background radiation, provides an excellent opportunity to study the very early Universe. In the simplest viable theoretical models the relic gravitational wave background is characterized by two parameters, the tensor-to-scalar ratio

Relic gravitational waves in light of the 7-year Wilkinson Microwave Anisotropy Probe data and improved prospects for the Planck mission

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Separating E and B types of polarization on an incomplete sky

and the tensor spectral index

Detecting relics of a thermal gravitational wave background in the early Universe

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Limits on high-frequency gravitational wave background from its interplay with large scale magnetic fields

. In this paper, we analyze the potential joint constraints on these two parameters,

Determination of Dark Energy by the Einstein Telescope: Comparing with CMB, BAO and SNIa Observations

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Components of the Gravitational Force in the Field of a Gravitational Wave

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On the road to discovery of relic gravitational waves : The TE and BB correlations in the cosmic microwave background radiation

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