We point out that there are only three polarizations for gravitational waves in $f(R)$ gravity, and the polarization due to massive scalar mode is a mix of pure longitudinal transverse breathing polarization. The classification six by Newman-Penrose quantities based on weak, plane null waves, so it not applicable mode.

In this work we discuss the polarization contents of Einstein-\ae{}ther theory and generalized tensor-vector-scalar (TeVeS) theory, as both theories have a normalized timelike vector field. We derive linearized equations motion around flat spacetime background using gauge-invariant variables to easily separate physical degrees freedom. find plane wave solutions identify polarizations by examining geodesic deviation equations. that there are five in six TeVeS theory. particular, transverse...

We analyze the polarization content of gravitational waves in Horndeski theory. Besides familiar plus and cross polarizations Einstein's General Relativity, there is one more state which mixture transverse breathing longitudinal polarizations. The additional mode excited by massive scalar field. In massless limit, disappears, while persists. upper bound on graviton mass severely constrains amplitude polarization, makes its detection highly unlikely ground-based or space-borne interferometers...

The gravitational wave provides a new method to examine General Relativity and its alternatives in the high speed, strong field regime. Alternative theories of gravity generally predict more polarizations than Relativity, so it is important study polarization contents reveal nature gravity. In this talk, we analyze Horndeski theory f(R) We find out that addition familiar plus cross polarizations, massless predicts an extra transverse polarization, there mix pure longitudinal breathing...

The gravitational waves of Ho\v{r}ava gravity, their polarization states and possible observational signatures are discussed. Using the gauge-invariant variable formalism, we found three modes in gravity excited by physical degrees freedom contained this theory. In particular, scalar degree excites a mix transverse breathing longitudinal polarizations. constraints from previous experimental observations taken into account, especially including speed bound GW170817 GRB 170817A. It was that...

The gravitational lensing of waves might cause beat patterns detectable by interferometers. feature this kind signal is the existence pattern in early inspiral phase, followed a seemingly randomly changing profile. After strain peaks for first time, takes usual waveform and second time. Once detected, actual magnification factors can be obtained, so true luminosity distance binary system known. If lens described point mass or singular isothermal sphere, functional forms time delay are simple...

The relation between gravitational memory effects and Bondi-Metzner-Sachs symmetry of the asymptotically flat spacetimes is studied in scalar-tensor theory. For this purpose, solutions to equations motion near future null infinity are obtained generalized Bondi-Sachs coordinates with a suitable determinant condition. It turns out that group also semi-direct product an infinitesimal dimensional supertranslation Lorentz as general relativity. There degenerate vacua both tensor scalar sectors...

Abstract Dynamical Chern-Simons (DCS) gravity, a typical parity-violating gravitational theory, modifies both the generation and propagation of waves from general relativity (GR). In this work, we derive waveform radiated binary slowly-rotating black hole system with eccentric orbits under spin-aligned assumption in DCS theory. Compared GR, modification enters second-order post-Newtonian (2PN) approximation, affecting spin-spin coupling monopole-quadrupole motion. This produces an extra...

In this paper, the polarization contents of Einstein-\ae ther theory and generalized TeVeS are studied. The has five polarizations, while six. particular, transverse longitudinal breathing mixed. The~possibility using pulsar timing arrays to detect extra polarizations in Einstein-\ae{}ther was also investigated. analysis showed that different cannot be easily distinguished by theory. For theory, one propagating modes travels much faster than speed light due bound set GW170817. some parameter...

Abstract Emergence of gravitational wave (GW) astronomy revived the interest in exploring low-frequency GW spectrum inaccessible from ground. Satellite observatory DECihertz Interferometer Gravitational Observatory (DECIGO) its original configuration and currently proposed smaller-scale B-DECIGO are aimed to cover decihertz part spectrum, which fills gap between LISA millihertz deca- kilohertz range probed by ground-based detectors. In this paper we forecast detection rates inspiraling...

General relativity predicts the existence of only two tensorial gravitational wave polarizations, while a generic metric theory gravity can possess up to four additional including vectors and scalar ones. These vector/scalar polarizations are in general generated by intrinsic new degrees freedom specific theories gravity. In this paper, we show that, with violation Lorentz symmetry framework standard model extension, nontensorial be directly excited freedom. We consider diffeomorphism...

Similar to the light, gravitational waves traveling in multiple paths may arrive at same location if there is a lens on their way. Apart from magnification of amplitudes and time delay between wave rays, lensing also rotates polarization planes. This results changes antenna pattern function, which describes response detector its relative orientation wave. These effects are all reflected strain, signal registered by interferometers. The rays various directions stimulate different strains....

The recently proposed Skordis-Z\l{}o\ifmmode \acute{s}\else \'{s}\fi{}nik theory is the first relativistic modified Newtonian dynamics (MOND) that can recover success of standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model at matching observations cosmic microwave background. This paper aims to revisit and MOND approximations gravitational wave analysis theory. For local parameters, we show one could obtain both time-varying effective constant ${G}_{\mathrm{N}}$ characteristic...

The detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory opens a new era to use test alternative theories gravity. We investigate polarizations in f (R) gravity and Horndeski theory, both containing scalar modes. These predict that addition familiar + × polarizations, there are transverse breathing longitudinal excited massive mode polarization is single mixed state. It would be very difficult detect interferometers, while pulsar timing array may better...

We study the asymptotically flat spacetime in Chern-Simons modified gravity and then gravitational memory effects are considered this work. If scalar does not directly couple with ordinary matter fields, there also displacement, spin, center-of-mass as general relativity. This is because term of action that violates parity invariance linear field but quadratic curvature tensor. results violation occurring at higher orders inverse luminosity radius. Although exists field, interferometers,...

This work analyzes the asymptotic behaviors of asymptotically flat solutions Einstein-\ae{}ther theory in linear case. The vacuum for tensor, vector, and scalar modes are first obtained, written as sums various multipolar moments. suitable coordinate transformations then determined, so-called pseudo-Newman-Unti systems constructed all radiative modes. In these coordinates, it is easy to identify symmetries. It turns out that three kinds possess familiar Bondi-Metzner-Sachs symmetries or...

Abstract The asymptotic symmetries in the Brans-Dicke theory are analyzed using Penrose's conformal completion method, which is independent of coordinate system used. These symmetries, indeed, include supertranslations and Lorentz transformations for an asymptotically flat spacetime. With Wald-Zoupas formalism, “conserved charges” fluxes Bondi-Metzner-Sachs algebra computed. scalar degree freedom contributes only to boost charge, even though it plays a role various fluxes. flux-balance laws...

The coherent nature of gravitational wave emanating from a compact binary system makes it possible to detect some interference patterns in two (or more) signals registered simultaneously by the detector. Gravitational lensing effect can be used bend trajectories waves, which might reach detector at same time. Once this happens, beat pattern may form, and obtain luminosity distance source, lens mass, cosmological parameters such as Hubble constant. Crucial question is how many kind events...

Alternative theories of gravity not only modify the polarization contents gravitational wave, but also affect motions stars and energy radiated away via radiation. These aspects leave imprints in observational data, which enables test General Relativity its alternatives. In this work, Nordtvedt effect Shapiro time delay are calculated order to constrain Horndeski theory using observations lunar laser ranging experiments Cassini time-delay data. The effective stress-energy tensor is obtained...

There exist gravitational memory effects in Brans-Dicke theory. They are closely related to the Bondi-Metzner-Sachs symmetries living on null infinity an isolated system. By studying asymptotically flat spacetime theory and asymptotic symmetries, one discovers that displacement effect tensor sector is due vacuum transition caused by energy fluxes panetrating infinity, while scalar sector, angular momentum fluxes. Together with spin center-of-mass effects, memories constrained various...

In this work, conserved charges and fluxes at the future null infinity are determined in asymptotically flat spacetime for Chern-Simons modified gravity. The flux-balance laws used to constrain memory effects. For tensor memories, Penrose's conformal completion method is analyze asymptotic structures symmetries, then, Bondi-Metzner-Sachs algebra constructed with Wald-Zoupas formalism. These take very similar forms those Brans-Dicke theory. scalar memory, gravity rewritten first-order...

This paper investigates a particular type of wormhole. The wormhole solutions studied are obtained by sewing together two static, spherically symmetric, charged black-hole metrics at their horizons. wormholes in background Kalb-Ramond field, which is the source necessary tension gravitational field. metric-tensor elements numerically solving Einstein's equations with stress-energy-tensor given combination static electric and fields. For certain range charge positive away from throat, but...

Gravitational lensing has long been used to measure or constrain cosmology models. Although the effect of gravitational waves not observed by LIGO/Virgo, it is expected that there can be a few hundreds lensed events detected future Japanese space-borne interferometers DECIGO and B-DECIGO, if they are running for 4 years. Given predicted wave events, one estimate constraints on cosmological parameters via statistics time delay methods. With method, knowledge lens redshifts, even with moderate...

In this work, we consider the burst signal of dark photon, hypothetical vector boson $U(1{)}_{B}$ or $U(1{)}_{B\ensuremath{-}L}$ gauge group, generated by a compact binary star system. The absence in laser interferometer puts bounds on coupling constant $\ensuremath{\epsilon}$ to ordinary matter. It turns out that if photon is massless, ${\ensuremath{\epsilon}}^{2}$ order ${10}^{\ensuremath{-}37}--{10}^{\ensuremath{-}33}$ at most; massive case, upper bound about...