A design study is currently in progress for a third generation gravitational-wave (GW) detector called Einstein Telescope (ET). An important kind of source for ET will be the inspiral and merger of binary neutron stars (BNS) up to z ∼ 2. If BNS mergers are the progenitors of short-hard γ-ray bursts, then some fraction of them will be seen both electromagnetically and through GW, so that the luminosity distance and the redshift of the source can be determined separately. An important property of these 'standard sirens' is that they are self-calibrating: the luminosity distance can be inferred directly from the GW signal, with no need for a cosmic distance ladder. Thus, standard sirens will provide a powerful independent check of the ΛCDM model. In previous work, estimates were made of how well ET would be able to measure a subset of the cosmological parameters (such as the dark energy parameter w 0 ) it will have access to, assuming that the others had been determined to great accuracy by alternative means. Here we perform a more careful analysis by explicitly using the potential Planck CMB data as prior information for these other parameters. We find that ET will be able to constrain w 0 and w a with accuracies ∆w 0 = 0.099 and ∆w a = 0.302, respectively. These results are compared with projected accuracies for the JDEM Baryon Acoustic Oscillations (BAO) project and the SNAP Type Ia supernovae (SNIa) observations.

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 C XX 0 ' for X, X 0 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 ''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 ' 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.

Abstract.Gravitational waves bring about the relative motion of free test masses. The detailed knowledge of this motion is important conceptually and practically, because the mirrors of laser interferometric detectors of gravitational waves are essentially free test masses. There exists an analogy between the motion of free masses in the field of a gravitational wave and the motion of free charges in the field of an electromagnetic wave. In particular, a gravitational wave drives the masses in the plane of the wave-front and also, to a smaller extent, back and forth in the direction of the wave's propagation. To describe this motion, we introduce the notion of "electric" and "magnetic" components of the gravitational force. This analogy is not perfect, but it reflects some important features of the phenomenon. Using different methods, we demonstrate the presence and importance of what we call the "magnetic" component of motion of free masses. It contributes to the variation of distance between a pair of particles. We explicitly derive the full response function of a 2-arm laser interferometer to a gravitational wave of arbitrary polarization. We give a convenient description of the response function in terms of the spin-weighted spherical harmonics. We show that the previously ignored "magnetic" component may provide a correction of up to 10%, or so, to the usual "electric" component of the response function. The "magnetic" contribution must be taken into account in the data analysis, if the parameters of the radiating system are not to be mis-estimated.

The detection of primordial gravitational waves is one of the biggest challenges of the present time. The existing (Wilkinson Microwave Anisotropy Probe) observations are helpful on the road to this goal, and the forthcoming experiments (Planck) are likely to complete this mission. We show that the 5-year Wilkinson Microwave Anisotropy Probe T E data contains a hint of the presence of gravitational wave contribution. In terms of the parameter R, which gives the ratio of contributions from gravitational waves and density perturbations to the temperature quadrupole, the best-fit model produced R = 0.24. Because of large residual noises, the uncertainty of this determination is still large, and it easily includes the R = 0 hypothesis. However, the uncertainty will be strongly reduced in the forthcoming observations which are more sensitive. We numerically simulated the Planck data and concluded that the relic gravitational waves with R = 0.24 will be present at a better than 3σ level in the T E observational channel, and at a better than 2σ level in the 'realistic' BB channel. The balloon-borne and ground-based observations may provide a healthy competition to Planck in some parts of the lower-ℓ spectrum.

Detection of magnetic-type (B-type) polarization in the Cosmic Microwave Background (CMB) radiation plays a crucial role in probing the relic gravitational wave (RGW) background. In this paper, we propose a new method to deconstruct a polarization map on an incomplete sky in real space into purely electric and magnetic polarization type maps, E(γ) and B(γ), respectively. The main properties of our approach are as follows: Firstly, the fields E(γ) and B(γ) are constructed in real space with a minimal loss of information.This loss of information arises due to the removal of a narrow edge of the constructed map in order to remove various numerical errors, including those arising from finite pixel size. Secondly, this method is fast and can be efficiently applied to high resolution maps due to the use of the fast spherical harmonics transformation. Thirdly, the constructed fields, E(γ) and B(γ), are scalar fields. . Basing our results on the performance of this estimator, we discuss the RGW detection ability of two future ground-based CMB experiments, QUIET and POLARBEAR.

The prospect of detecting relic gravitational waves (RGWs), through their imprint in the cosmic microwave background radiation, provides an excellent opportunity to study the very early Universe. In simplest viable theoretical models the RGW background is characterized by two parameters, the tensor-to-scalar ratio r and the tensor spectral index n t . In this paper, we analyze the potential joint constraints on these two parameters, r and n t , using the data from the upcoming cosmic microwave background radiation experiments. Introducing the notion of the best pivot multipole ℓ * t , we find that at this pivot multipole the parameters r and n t are uncorrelated, and have the smallest variances. We derive the analytical formulae for the best pivot multipole number ℓ * t , and the variances of the parameters r and n t . We verify these analytical calculations using numerical simulation methods, and find agreement to within 20%. The analytical results provides a simple way to estimate the detection ability for the relic gravitational waves by the future observations of the cosmic microwave background radiation.

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 specific type of gravitational waves, namely gravitational wave burst with memory (BWM), using pulsar timing. We study the unique signature produced by BWM in anomalous pulsar timing residuals. We show that the present day pulsar timing precision allows one to detect BWM due to SMBH mergers from distances up to 1 Gpc (for case of equal mass 10^8 Msun SMBH). Improvements in precision of pulsar timing together with the increase in number of observed pulsars should eventually lead to detection of a BWM signal due to SMBH merger, thereby making the proposed technique complementary to the capabilities of the planned LISA mission.Comment: 9 pages, 1 figure, generally matches the MNRAS versio

In this work, analyzing the propagation of electromagnetic waves in the field of gravitational waves, we show the presence and significance of the so called surfing effect for pulsar timing measurements. It is shown that, due to the transverse nature of gravitational waves, the surfing effect leads to enormous pulsar timing residuals if the speed of gravitational waves is smaller than speed of light. This fact allows to place significant constraints on parameter ǫ, which characterizes the relative deviation of the speed of gravitational waves from the speed of light. We show that the existing constraints from pulsar timing measurements already place stringent limits on ǫ and consequently on the mass of graviton m g . These limits on m g are three orders of magnitude stronger than the current constraints from Solar System tests. The current constraints also allow to rule out massive gravitons as possible candidates for cold dark matter in galactic halo. In the near future, the gravitational wave background from extragalactic super massive black hole binaries, along with the expected sub-microsecond pulsar timing accuracy, will allow to achieve constrains of ǫ 0.4% and possibly stronger.