**Gravitational** **waves** triggered by $B-L$ charged hidden scalar and
leptogenesis

**gravitational**

**wave**(GW) prospects at future space-based interferometer LISA and other GW experiments. The baryon asymmetry of the Universe is addressed by the resonant leptogenesis mechanism, which is potentially disturbed by the hidden scalar. To make the GW spectra detectable by LISA and resonant leptogenesis work in the conformal $U(1)_{B-L}$ theory, the hidden scalar can not fully saturate the observed DM relic density.

8/10 relevant

arXiv

The Fredholm Approach to Charactize **Gravitational** **Wave** Echoes

**Gravitational**

**waves**are a sensitive probe into the structure of compact astronomical objects and the nature of

**gravity**in the strong regime. Expand abstract.

**Gravitational**

**waves**are a sensitive probe into the structure of compact astronomical objects and the nature of

**gravity**in the strong regime. Modifications of near-horizon physics can imprint on the late time ringdown waveform, leaving behind a train of echoes, from which useful information about new physics in the strong

**gravity**regime can be extracted. We propose a novel approach to compute the ringdown waveform and characterize individual echoes perturbatively using the Fredholm determinants, which can be intuitively represented via a diagrammatical scheme. Direct non-perturbative treatments can also be easily implemented for some cases. Numerically, the method is also effective and accurate even for relatively low resources.

4/10 relevant

arXiv

Constraints on primordial curvature perturbations from primordial black
hole dark matter and secondary **gravitational** **waves**

**gravitational**

**waves**produced after the horizon reentry, we derive an analytical formula for the time integral of the source and analytical behavior of the time dependence of the energy density of induced

**gravitation**al

**wave**s is obtained. Expand abstract.

**gravitational**

**waves**can be used to probe the small scale physics at very early time. For secondary

**gravitational**

**waves**produced after the horizon reentry, we derive an analytical formula for the time integral of the source and analytical behavior of the time dependence of the energy density of induced

**gravitational**

**waves**is obtained. By proposing a piecewise power law parametrization for the power spectrum of primordial curvature perturbations, we use the observational constraints on primordial black hole dark matter to obtain an upper bound on the power spectrum, and discuss the test of the model with future space based

**gravitational**

**wave**antenna.

10/10 relevant

arXiv

Neutron Star Merger Afterglows: Population Prospects for the
**Gravitational** **Wave** Era

**gravitational**

**waves**and electromagnetic bands. Expand abstract.

**gravitational**

**wave**signals during the next science runs of the

**gravitational**interferometer network. The diversity of the observed population of afterglows of these future events is subject to various factors, which are (i) intrinsic, such as the energy of the ejecta, (ii) environmental, such as the ambient medium density or (iii) observational, such as the viewing angle and distance of the source. Through prescribing a population of mergers and modelling their afterglows, we study the diversity of those events to be observed jointly in

**gravitational**

**waves**and electromagnetic bands. In the future, observables of detected events such as viewing angle, distance, afterglow peak flux or proper motion will form distributions which together with predictions from our study will provide insight on neutron star mergers and their environments.

4/10 relevant

arXiv

Astrophysical signal consistency test adapted for **gravitational**-wave
transient searches

**gravitational**

**wave**transients from the noisy glitches. Expand abstract.

**Gravitational**

**wave**astronomy is established with direct observation of

**gravitational**

**wave**from merging binary black holes and binary neutron stars during the first and second observing run of LIGO and Virgo detectors. The

**gravitational**-

**wave**transient searches mainly categories into two families: modeled and modeled-independent searches. The modeled searches are based on matched filtering techniques and model-independent searches are based on the extraction of excess power from time-frequency representations. We have proposed a hybrid method, called wavegraph that mixes the two approaches. It uses astrophysical information at the extraction stage of model-independent search using a mathematical graph. In this work, we assess the performance of wavegraph clustering in real LIGO and Virgo noises (the sixth science run and the first observing run) and using the coherent WaveBurst transient search as a backbone. Further, we propose a new signal consistency test for this algorithm. This test uses the amplitude profile information to distinguish between the

**gravitational**

**wave**transients from the noisy glitches. This test is able to remove a large fraction of loud glitches, which thus results in additional overall sensitivity in the context of searches for binary black-hole mergers in the low-mass range.

4/10 relevant

arXiv

Parametric solutions of the generalized short pulse equations

**wave**with cusps is also worth remarking in connection with Gerstner's trochoidal solution in deep

**gravity**

**waves**. Expand abstract.

**waves**with cusp singularity. In addition, the smooth periodic traveling

**wave**solutions are provided by employing phase plane analysis. Several new features of solutions are exhibited. As for non-periodic solutions, smooth breather solutions are of particular interest from the perspective of applications to real physical phenomena. The cycloid reduced from the periodic traveling

**wave**with cusps is also worth remarking in connection with Gerstner's trochoidal solution in deep

**gravity**

**waves**. A number of works are left for future study, some of which will be addressed in concluding remarks.

4/10 relevant

arXiv

Space Based **Gravitational** **Wave** Astronomy Beyond LISA

**gravitational**

**wave**spectrum, around 2034, the surge of

**gravitation**al-wave astronomy will strongly compel a subsequent mission to further explore the frequency bands of the GW spectrum that can only be accessed from space. Expand abstract.

**gravitational**

**wave**(GW) spectrum between 0.1 and 100 mHz, the mHz band. This band is expected to be the richest part of the GW spectrum, in types of sources, numbers of sources, signal-to-noise ratios and discovery potential. When LISA opens the low-frequency window of the

**gravitational**

**wave**spectrum, around 2034, the surge of

**gravitational**-

**wave**astronomy will strongly compel a subsequent mission to further explore the frequency bands of the GW spectrum that can only be accessed from space. The 2020s is the time to start developing technology and studying mission concepts for a large-scale mission to be launched in the 2040s. The mission concept would then be proposed to Astro2030. Only space based missions can access the GW spectrum between 10 nHz and 1 Hz because of the Earths seismic noise. This white paper surveys the science in this band and mission concepts that could accomplish that science. The proposed small scale activity is a technology development program that would support a range of concepts and a mission concept study to choose a specific mission concept for Astro2030. In this white paper, we will refer to a generic GW mission beyond LISA as bLISA.

4/10 relevant

arXiv

Chirping compact stars: **gravitational** radiation and detection degeneracy
with binary systems A conceptual pathfinder for space-based
**gravitation**al-**wave** observatories

**gravitational**

**waves**(GWs) with a chirp-like behavior (hereafter chirping ellipsoids, CELs). We show that the GW frequency-amplitude evolution of CELs (mass $\sim 1$~M$_\odot$, radius $\sim10^3$~km, polytropic equation of state with index $n\approx 3$) is indistinguishable from that emitted by double white dwarfs (DWDs) and by extreme mass-ratio inspirals (EMRIs) composed of an intermediate-mass (e.g.~$10^3~M_\odot$) black hole and a planet-like (e.g.~$10^{-4}~M_\odot$) companion, in a specific frequency interval within the detector sensitivity band in which the GWs of all these systems are quasi-monochromatic. We estimate that for reasonable astrophysical assumptions, the rates in the local Universe of CELs, DWDs and EMRIs in the mass range considered here, are very similar, posing a detection-degeneracy challenge for space-based GW detectors. The astrophysical implications of this CEL-binary detection degeneracy by space-based GW-detection facilities, are outlined.

4/10 relevant

arXiv

**Gravitational** **wave** probes of dark matter: challenges and opportunities

**gravitational**

**waves**, covering a wide range of dark matter candidate types and signals. Expand abstract.

**gravitational**waves, covering a wide range of dark matter candidate types and signals. We argue that present and upcoming

**gravitational**

**wave**probes offer unprecedented opportunities for unraveling the nature of dark matter and we identify the most urgent challenges and open problems with the aim of encouraging a strong community effort at the interface between these two exciting fields of research.

4/10 relevant

arXiv

Unique Quantum Topological State with Emergent Quantum **Gravity**

**waves**that are really spin-2

**gravitational**

**wave**s. Expand abstract.

**gravity**. To enforce the global topological constraint, we introduce topological spin space (or topological spinor spacetime in long

**wave**-length limit). Such a spiral state is denoted by a mapping between a topological spin space and the Cartesian space. To enforce the local topological constraint, a topological BF term on topological spinor spacetime becomes the Einstein-Hilbert action that exactly reproduces the low energy physics of the general relativity. The topological excitations for the system are fermions that are really the unit of the topological spinor spacetime and the collective excitations are spinor-

**waves**that are really spin-2

**gravitational**

**waves**. In addition, we provide several new effects from the theory of the emergent quantum

**gravity**that could be verified in experiments in the future.

4/10 relevant

arXiv