Waveform of **gravitational** **waves** in the ghost-free parity-violating
gravities

**Gravitational**

**waves**(GWs) provide an excellent opportunity to test the gravity in the strong

**gravitation**al fields. Expand abstract.

**Gravitational**

**waves**(GWs) provide an excellent opportunity to test the gravity in the strong

**gravitational**fields. In this article, we calculate the waveform of GWs, produced by the coalescence of compact binaries, in an extension of the Chern-Simons gravity by including higher derivatives of the coupling scalar field. By comparing the two circular polarization modes, we find the effects of amplitude birefringence and velocity birefringence of GWs in their propagation caused by the parity violation in gravity, which are explicitly presented in the GW waveforms by the amplitude and phase modifications respectively. Combining the two modes, we obtain the GW waveforms in the Fourier domain, and find that the deviations from those in General Relativity are dominated by effects of velocity birefringence of GWs. In addition, we also map the effects of the parity violation on the waveform onto the parameterized post-Einsteinian (PPE) framework and identify explicitly the PPE parameters.

10/10 relevant

arXiv

**Gravitational** **Waves** as a Probe of Left-Right Symmetry Breaking

**gravitational**

**wave**background induced by the phase transition in which $SU(3)_C \times SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ is broken down to the Standard Model gauge symmetry group. A prerequisite for

**gravitational**

**wave**production in this context is a first-order phase transition, the occurrence of which we find in a significant portion of the parameter space. Although the produced

**gravitational**

**waves**are typically too weak for a discovery at any current or future detector, upon investigating correlations between all relevant terms in the scalar potential, we have identified values of parameters leading to observable signals. This indicates that, given a certain moderate fine-tuning, the minimal left-right symmetric model with scalar triplets features another powerful probe which can lead to either novel constraints or remarkable discoveries in the near future. Let us note that some of our results, such as the full set of thermal masses, have to the best of our knowledge not been presented before and might be useful for future studies, in particular in the context of electroweak baryogenesis.

10/10 relevant

arXiv

Electroweak phase transition with composite Higgs models: calculability,
**gravitational** **waves** and collider searches

**gravitational**

**waves**prediction and the related collider phenomenology.

10/10 relevant

arXiv

Analytic Waveforms for Eccentric **Gravitational** **Wave** Bursts

**wave**forms designed to accurately capture the burst of

**gravitational**radiation from the closest approach of highly eccentric compact binaries. Expand abstract.

**gravitational**radiation from the closest approach of highly eccentric compact binaries. The waveforms are constructed by performing a re-summation procedure on the well-known Fourier series representation of the two-body problem at leading post-Newtonian order. This procedure results in two models: one in the time-domain, and one in the Fourier domain, which makes use of the stationary phase approximation. We discuss the computational efficiency of both these models, and validate the time domain model against numerical waveforms. We further show how to use these individual waveforms to detect a repeated burst source.

5/10 relevant

arXiv

Propagation of **Gravitational** **Waves** in Chern-Simons Axion Einstein
Gravity

**gravitational**

**waves**in a flat Friedman-Robertson-Walker background, in the context of a string motivated corrected Einstein gravity. Particularly, we shall consider a misalignment axion Einstein gravity in the presence of a string originating Chern-Simons coupling of the axion field to the Chern-Pontryagin density in four dimensions. We shall focus our study on the propagation of the

**gravitational**waves, and we shall investigate whether there exists any difference in the propagation of the polarization states of the

**gravitational**

**waves**. As we demonstrate, the dispersion relations are different in the Right-handed mode and the Left-handed mode. Finally, we compare the propagation of the axion Chern-Simons Einstein theory with that of standard $F(R)$ gravity.

10/10 relevant

arXiv

The speed of gravity

**gravitational**

**waves**deviates, ever so slightly, from luminality on cosmological and other spontaneously Lorentz-breaking backgrounds. This effect results from loop contributions from massive fields of any spin, including Standard Model fields, or from tree level effects from massive higher spins $s \ge 2$. We show that for the choice of interaction signs implied by S-matrix and spectral density positivity bounds suggested by analyticity and causality, the speed of

**gravitational**

**waves**is in general superluminal at low-energies on NEC preserving backgrounds, meaning

**gravitational**

**waves**travel faster than allowed by the metric to which photons and Standard Model fields are minimally coupled. We show that departure of the speed from unity increases in the IR and argue that the speed inevitably returns to luminal at high energies as required by Lorentz invariance. Performing a special tuning of the EFT so that renormalization sensitive curvature-squared terms are set to zero, we find that finite loop corrections from Standard Model fields still lead to an epoch dependent modification of the speed of

**gravitational**

**waves**which is determined by the precise field content of the lightest particles with masses larger than the Hubble parameter today. Depending on interpretation, such considerations could potentially have far-reaching implications on light scalar models, such as axionic or fuzzy cold dark matter.

5/10 relevant

arXiv

Implications of the binary coalescence events found in O1 and O2 for the
stochastic background of **gravitational** events

**gravitational**

**waves**, including the search for

**gravitation**al

**wave**polarizations outside of what is predicted from general relativity. Expand abstract.

**Gravitational**

**waves**from the merger of binary black hole systems and a binary neutron star system have been observed. A major goal for LIGO and Virgo is to detect or set limits on a stochastic background of

**gravitational**

**waves**. A stochastic background of

**gravitational**

**waves**is expected to arise from a superposition of a large number of unresolved cosmological and/or astrophysical sources. A cosmologically produced background would carry unique signatures from the earliest epochs in the evolution of the Universe. Similarly, an astrophysical background would provide information about the astrophysical sources that generated it. The observation of

**gravitational**

**waves**from compact binary mergers implies that there will be a stochastic background from these sources that could be observed by Advanced LIGO and Advanced Virgo in the coming years. The LIGO and Virgo search for a stochastic background should probe interesting regions of the parameter space for numerous astrophysical and cosmological models. Presented here is an outline of LIGO and Virgo's search strategies for a stochastic background of

**gravitational**waves, including the search for

**gravitational**

**wave**polarizations outside of what is predicted from general relativity. Also discussed is how global electromagnetic noise (from the Schumann resonances) could affect this search; possible strategies to monitor and subtract this potential source of correlated noise in a the global detector network are explained. The results from Advanced LIGO's observing runs O1 and O2 will be presented, along with the implications of the

**gravitational**

**wave**detections. The future goals for Advanced LIGO and Advanced Virgo will be explained.

9/10 relevant

arXiv

A guide to LIGO-Virgo detector noise and extraction of transient
**gravitational**-**wave** signals

**gravitational**-

**wave**events. Expand abstract.

**gravitational**-

**wave**events during the first two observing runs of the advanced detector era. All eleven events were consistent with being from well-modeled mergers between compact stellar-mass objects: black holes or neutron stars. The data around the time of each of these events have been made publicly available through the

**Gravitational**-

**Wave**Open Science Center. The entirety of the

**gravitational**-

**wave**strain data from the first and second observing runs have also now been made publicly available. There is considerable interest among the broad scientific community in understanding the data and methods used in the analyses. In this paper, we provide an overview of the detector noise properties and the data analysis techniques used to detect

**gravitational**-

**wave**signals and infer the source properties. We describe some of the checks that are performed to validate the analyses and results from the observations of

**gravitational**-

**wave**events. We also address concerns that have been raised about various properties of LIGO-Virgo detector noise and the correctness of our analyses as applied to the resulting data.

9/10 relevant

arXiv

The Missing Link in **Gravitational**-**Wave** Astronomy: Discoveries waiting in
the decihertz range

**gravitational**-

**wave**astronomical revolution began in 2015 with LIGO's observation of the coalescence of two stellar-mass black holes. Over the coming decades, ground-based detectors like LIGO will extend their reach, discovering thousands of stellar-mass binaries. In the 2030s, the space-based LISA will enable

**gravitational**-

**wave**observations of the massive black holes in galactic centres. Between LISA and ground-based observatories lies the unexplored decihertz

**gravitational**-

**wave**frequency band. Here, we propose a Decihertz Observatory to cover this band, and complement observations made by other

**gravitational**-

**wave**observatories. The decihertz band is uniquely suited to observation of intermediate-mass ($\sim 10^2-10^4$ M$_\odot$) black holes, which may form the missing link between stellar-mass and massive black holes, offering a unique opportunity to measure their properties. Decihertz observations will be able to detect stellar-mass binaries days to years before they merge and are observed by ground-based detectors, providing early warning of nearby binary neutron star mergers, and enabling measurements of the eccentricity of binary black holes, providing revealing insights into their formation. Observing decihertz

**gravitational**-

**waves**also opens the possibility of testing fundamental physics in a new laboratory, permitting unique tests of general relativity and the Standard Model of particle physics. Overall, a Decihertz Observatory will answer key questions about how black holes form and evolve across cosmic time, open new avenues for multimessenger astronomy, and advance our understanding of gravitation, particle physics and cosmology.

10/10 relevant

arXiv

Probing the Nature of Black Holes: Deep in the mHz **Gravitational**-Wave
Sky

**gravitational**-

**wave**detectors will probe general relativity and fundamental physics in previously inaccessible regimes, and allow us to address some of these fundamental issues in our current understanding of nature. Expand abstract.

**gravitational**radiation. Our capacity to probe their nature is limited by the sensitivity of our detectors. The LIGO/Virgo interferometers are the

**gravitational**-

**wave**equivalent of Galileo's telescope. The first few detections represent the beginning of a long journey of exploration. At the current pace of technological progress, it is reasonable to expect that the

**gravitational**-

**wave**detectors available in the 2035-2050s will be formidable tools to explore these fascinating objects in the cosmos, and space-based detectors with peak sensitivities in the mHz band represent one class of such tools. These detectors have a staggering discovery potential, and they will address fundamental open questions in physics and astronomy. Are astrophysical black holes adequately described by general relativity? Do we have empirical evidence for event horizons? Can black holes provide a glimpse into quantum gravity, or reveal a classical breakdown of Einstein's gravity? How and when did black holes form, and how do they grow? Are there new long-range interactions or fields in our universe, potentially related to dark matter and dark energy or a more fundamental description of gravitation? Precision tests of black hole spacetimes with mHz-band

**gravitational**-

**wave**detectors will probe general relativity and fundamental physics in previously inaccessible regimes, and allow us to address some of these fundamental issues in our current understanding of nature.

8/10 relevant

arXiv