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gravitational waves (gw) are generally affected by modification of a gravity theory during propagation at cosmological distances. we numerically perform a quantitative analysis on horndeski theory at the cosmological scale to constrain the horndeski theory by gw observations in a model-independent way. we formulate a parametrization for a numerical simulation based on the monte carlo method and obtain the classification of the models that agrees with cosmic accelerating expansion within observational errors of the hubble parameter. as a result, we find that a large group of the models in the horndeski theory that mimic cosmic expansion of the λ cdm model can be excluded from the simultaneous detection of a gw and its electromagnetic transient counterpart. based on our result and the latest detection of gw170817 and grb170817a, we conclude that the subclass of horndeski theory including arbitrary functions g4 and g5 can hardly explain cosmic accelerating expansion without fine-tuning. | generalized framework for testing gravity with gravitational-wave propagation. ii. constraints on horndeski theory |
we have searched for possible gravitational wave echo signals for nine binary black hole merger events observed by advanced ligo and virgo during the first and second observation runs. to construct an echo template, we consider kerr spacetime, where the event horizon is replaced by a reflective membrane. we use a frequency-dependent reflection rate at the angular potential barrier, which is fitted to the numerical data obtained by solving teukolsky equations. this reflection rate gives a frequency-dependent transmission rate that is suppressed at lower frequencies in the template. we also take into account the overall phase shift of the waveform as a parameter, which arises when the wave is reflected at the membrane and potential barrier. using this template based on black hole perturbation, we find no significant echo signals in the binary black hole merger events. | searching for black hole echoes from the ligo-virgo catalog gwtc-1 |
numerical studies of gas accretion onto supermassive black hole binaries have generally been limited to conditions where the circumbinary disk (cbd) is 10-100 times thicker than expected for disks in active galactic nuclei. this discrepancy arises from technical limitations, and also from publication bias toward replicating fiducial numerical models. here we present the first systematic study of how the binary's orbital evolution varies with disk scale height. we report three key results: (1) binary orbital evolution switches from outspiraling for warm disks (aspect ratio h/r ∼ 0.1), to inspiraling for more realistic cooler, thinner disks at a critical value of h/r ∼ 0.04, corresponding to orbital mach number ${{ \mathcal m }}_{\mathrm{crit}}\approx 25$ . (2) the net torque on the binary arises from a competition between positive torque from gas orbiting close to the black holes, and negative torque from the inner edge of the cbd, which is denser for thinner disks. this leads to increasingly negative net torques on the binary for increasingly thin disks. (3) the accretion rate is modestly suppressed with increasing mach number. we discuss how our results may influence modeling of the nano-hz gravitational-wave background, as well as estimates of the laser interferometer space antenna merger event rate. | gas-driven inspiral of binaries in thin accretion disks |
we present experimental and theoretical results on a new interferometer topology that nests a su(2) interferometer, e.g., a mach-zehnder or michelson interferometer, inside a su(1,1) interferometer, i.e., a mach-zehnder interferometer with parametric amplifiers in place of beam splitters. this su(2)-in-su(1,1) nested interferometer (sisni) simultaneously achieves a high signal-to-noise ratio (snr), sensitivity beyond the standard quantum limit (sql) and tolerance to photon losses external to the interferometer, e.g., in detectors. we implement a sisni using parametric amplification by four-wave mixing (fwm) in rb vapor and a laser-fed mach-zehnder su(2) interferometer. we observe path-length sensitivity with snr 2.2 db beyond the sql at power levels (and thus snr) 2 orders of magnitude beyond those of previous loss-tolerant interferometers. we find experimentally the optimal fwm gains and find agreement with a minimal quantum noise model for the fwm process. the results suggest ways to boost the in-practice sensitivity of high-power interferometers, e.g., gravitational wave interferometers, and may enable high-sensitivity, quantum-enhanced interferometry at wavelengths for which efficient detectors are not available. | su(2)-in-su(1,1) nested interferometer for high sensitivity, loss-tolerant quantum metrology |
recent observations with the chandra x-ray telescope continue to detect x-ray emission from the transient gw170817. in a total exposure of 96.6 ks, performed between 2020 march 9 and 16 (935-942 d after the merger), a total of 8 photons are measured at the source position, corresponding to a significance of ≈5σ. radio monitoring with the australian telescope compact array (atca) shows instead that the source has faded below our detection threshold (<33-= $\mu$ jy, 3σ). by assuming a constant spectral index of β = 0.585, we derive an unabsorbed x-ray flux of ≈1.4 × 10-15-=erg-=cm-2-=s-1, higher than earlier predictions, yet still consistent with a simple structured jet model. we discuss possible scenarios that could account for prolonged emission in x-rays. the current data set appears consistent both with energy injection by a long-lived central engine and with the onset of a kilonova afterglow, arising from the interaction of the sub-relativistic merger ejecta with the surrounding medium. long-term monitoring of this source will be essential to test these different models. | a thousand days after the merger: continued x-ray emission from gw170817 |
we present a new version of the high altitude mechanistic general circulation model (hiamcm) with specified dynamics. we utilize a spectral method that nudges only the large-scale flow to merra-2 reanalysis. the nudged hiamcm simulates gravity waves (gws) down to horizontal wavelengths of about 200 km from the troposphere to the thermosphere like the free-running model, including the generation of secondary and tertiary gws. case studies show that the simulated large-scale gws are consistent with those in the reanalysis, while the medium-scale gws compare well with observations in the northern winter 2016 stratosphere from the atmospheric infrared sounder (airs). gws having wavelengths larger than about 1,350 km can be described with the nonlinear balance equation. the gws relevant in the stratosphere, however, have smaller scales and require a different approach. we propose that the gw amplification due to kinetic energy transfer from the large-scale flow combined with gw potential energy flux convergence helps to identify the mesoscale gw sources due to spontaneous emission. the gw amplification is strongest in the region of maximum large-scale vertical wind shear in the mid-stratosphere. maps of the time-averaged stratospheric gw activity simulated by the hiamcm and computed from airs satellite data show a persistent hot spot over europe during january 2016. at about 40 km, the average gw amplitudes are maximum in the region of fastest large-scale flow. we argue that refraction of gws originating in the troposphere, as well as gws from spontaneous emission in the stratosphere contribute to this effect. | a high-resolution whole-atmosphere model with resolved gravity waves and specified large-scale dynamics in the troposphere and stratosphere |
recently, abedi, dykaar and afshordi claimed evidence for a repeating damped echo signal following the binary black hole merger gravitational-wave events recorded in the first observational period of the advanced ligo interferometers. we discuss the methods of data analysis and significance estimation leading to this claim, and identify several important shortcomings. we conclude that their analysis does not provide significant observational evidence for the existence of planck-scale structure at black hole horizons, and suggest renewed analysis correcting for these shortcomings. | comments on: "echoes from the abyss: evidence for planck-scale structure at black hole horizons" |
the final ringdown phase in a coalescence process is a valuable laboratory to test general relativity and potentially constrain additional degrees of freedom in the gravitational sector. we introduce here an effective description for perturbations around spherically symmetric spacetimes in the context of scalar-tensor theories, which we apply to study quasi-normal modes for black holes with scalar hair. we derive the equations of motion governing the dynamics of both the polar and the axial modes in terms of the coefficients of the effective theory. assuming the deviation of the background from schwarzschild is small, we use the wkb method to introduce the notion of "light ring expansion". this approximation is analogous to the slow-roll expansion used for inflation, and it allows us to express the quasinormal mode spectrum in terms of a small number of parameters. this work is a first step in describing, in a model independent way, how the scalar hair can affect the ringdown stage and leave signatures on the emitted gravitational wave signal. potential signatures include the shifting of the quasi-normal spectrum, the breaking of isospectrality between polar and axial modes, and the existence of scalar radiation. | effective field theory of black hole quasinormal modes in scalar-tensor theories |
knowledge of the shape of the mass spectrum of compact objects can be used to help break the degeneracy between the mass and redshift of the gravitational wave (gw) sources and thus can be used to infer cosmological parameters in the absence of redshift measurements obtained from electromagnetic observations. in this paper, we study extensively different aspects of this approach, including its computational limits and achievable accuracy. focusing on ground-based detectors with current and future sensitivities, we first perform the analysis of an extensive set of simulated data using a hierarchical bayesian scheme that jointly fits the source population and cosmological parameters. we consider a population model (power-law plus gaussian) which exhibits characteristic scales (extremes of the mass spectrum, presence of an accumulation point modeled by a gaussian peak) that allow an indirect estimate of the source redshift. our analysis of this catalog highlights and quantifies the tight interplay between source population and cosmological parameters, as well as the influence of initial assumptions (whether formulated on the source or cosmological parameters). we then validate our results by an "end-to-end" analysis using simulated gw h (t ) data and posterior samples generated from bayesian samplers used for gw parameter estimation, thus mirroring the analysis chain used for observational data for the first time in literature. our results then lead us to re-examine the estimation of h0 obtained with gwtc-1 in abbott et al. [ligo scientific, virgo collaborations, astrophys. j. 909, 218 (2021), 10.3847/1538-4357/abdcb7], and we show explicitly how population assumptions impact the final h0 result. together, our results underline the importance of inferring source population and cosmological parameters simultaneously (and not separately as is often assumed). the only exception, as we discuss, is if an electromagnetic counterpart was to be observed for all the bbh events; then, the population assumptions have less impact on the estimation of cosmological parameters. | on the importance of source population models for gravitational-wave cosmology |
some of the most sensitive and precise measurements—for example, of inertia1, gravity2 and rotation3—are based on matter-wave interferometry with free-falling atomic clouds. to achieve very high sensitivities, the interrogation time has to be very long, and consequently the experimental apparatus needs to be very tall (in some cases reaching ten or even one hundred metres) or the experiments must be performed in microgravity in space4-7. cancelling gravitational acceleration (for example, in atomtronic circuits8,9 and matter-wave guides10) is expected to result in compact devices with extended interrogation times and therefore increased sensitivity. here we demonstrate smooth and controllable matter-wave guides by transporting bose-einstein condensates (becs) over macroscopic distances. we use a neutral-atom accelerator ring to bring becs to very high speeds (16 times their sound velocity) and transport them in a magnetic matter-wave guide for 15 centimetres while fully preserving their internal coherence. the resulting high angular momentum of more than 40,000ħ per atom (where ħ is the reduced planck constant) gives access to the higher landau levels of quantum hall states, and the hypersonic velocities achieved, combined with our ability to control potentials with picokelvin precision, will facilitate the study of superfluidity and give rise to tunnelling and a large range of transport regimes of ultracold atoms11-13. coherent matter-wave guides are expected to enable interaction times of several seconds in highly compact devices and lead to portable guided-atom interferometers for applications such as inertial navigation and gravity mapping. | hypersonic bose-einstein condensates in accelerator rings |
pesummary is a python software package for processing and visualizing data from any parameter estimation code. the easy to use python executable scripts and extensive online documentation has resulted in pesummary becoming a key component in the international gravitational-wave analysis toolkit. pesummary has been developed to be more than just a post-processing tool with all outputs fully self-contained. pesummary has become central to making gravitational-wave inference analysis open and easily reproducible. | pesummary: the code agnostic parameter estimation summary page builder |
assessing the probability that two or more gravitational wave (gw) events are lensed images of the same source requires an understanding of the properties of the lensed images. for short enough wavelengths where wave effects can be neglected, lensed images will generically have a fixed relative phase shift that needs to be taken into account in the lensing hypothesis. for nonprecessing, circular binaries dominated by quadrupole radiation, these lensing phase shifts are degenerate with either a shift in the coalescence phase or a detector and inclination-dependent shift in the orientation angle. this degeneracy is broken by the presence of higher harmonic modes with |m |≠2 in the former and |m |≠l in the latter. the presence of precession or eccentricity will also break this degeneracy. this implies that a lensed gw image will not necessarily be consistent with (unlensed) predictions from general relativity (gr). therefore, unlike the conventional scenario of electromagnetic waves, strong lensing of gws can lead to images with a modified phase evolution that can be observed. however, we find that for a wide range of parameters, the lensed (phase modified) waveform is similar enough to an unlensed (gr) waveform that gw detection pipelines will still find it. in particular, for present detectors, we find that templates with a shifted detector-dependent orientation angle have a signal-to-noise ratio differences of less than 1% for mass ratios up to 0.1, and less than 5% for precession parameters up to 0.5 and eccentricities up to 0.4 at 20 hz. in these ranges, the mismatch is lower than 10% with the alternative detector-independent coalescence phase shift. nonetheless, for a loud enough source, even with only one image it may be possible to directly identify it as a strongly lensed image from its non-gr, phase-shifted waveform. in more extreme cases, lensing may lead to considerable distortions, and the lensed images may even be undetected with current searches. nevertheless, an exact template with a phase shift in fourier space can always be constructed to fit any lensed image. we conclude that an optimal strong lensing search strategy would incorporate phase information in all stages of the identification of strong lensing, with an exact treatment in the final assessment of the probability of multiple lensed events. this work clarifies the role that strong lensing plays in the phase evolution of gws: how it can lead to apparent deviations from gr, how it can affect the detectability of gw events, and how it can be exploited to help identify cases of strong gravitational lensing of gravitational wave sources. | phase effects from strong gravitational lensing of gravitational waves |
models of particle physics that feature phase transitions typically provide predictions for stochastic gravitational wave signals at future detectors and such predictions are used to delineate portions of the model parameter space that can be constrained. the question is: how precise are such predictions? uncertainties enter in the calculation of the macroscopic thermal parameters and the dynamics of the phase transition itself. we calculate such uncertainties with increasing levels of sophistication in treating the phase transition dynamics. currently, the highest level of diligence corresponds to careful treatments of the source lifetime; mean bubble separation; going beyond the bag model approximation in solving the hydrodynamics equations and explicitly calculating the fraction of energy in the fluid from these equations rather than using a fit; and including fits for the energy lost to vorticity modes and reheating effects. the lowest level of diligence incorporates none of these effects. we compute the percolation and nucleation temperatures, the mean bubble separation, the fluid velocity, and ultimately the gravitational wave spectrum corresponding to the level of highest diligence for three explicit examples: smeft, a dark sector higgs model, and the real singlet-extended standard model (xsm). in each model, we contrast different levels of diligence in the calculation and find that the difference in the final predicted signal can be several orders of magnitude. our results indicate that calculating the gravitational wave spectrum for particle physics models and deducing precise constraints on the parameter space of such models continues to remain very much a work in progress and warrants care. | the benefits of diligence: how precise are predicted gravitational wave spectra in models with phase transitions? |
we revisit the perturbative expansion at high temperature and investigate its convergence by inspecting the renormalisation scale dependence of the effective potential. although at zero temperature the renormalisation group improved effective potential is scale independent at one-loop, we show how this breaks down at high temperature, due to the misalignment of loop and coupling expansions. following this, we show how one can recover renormalisation scale independence at high temperature, and that it requires computations at two-loop order. we demonstrate how this resolves some of the huge theoretical uncertainties in the gravitational wave signal of first-order phase transitions, though uncertainties remain stemming from the computation of the bubble nucleation rate. | on the perturbative expansion at high temperature and implications for cosmological phase transitions |
we revisit the lower bound on binary tidal deformability \tilde{{{λ }}} imposed by a luminous kilonova/macronova, at 2017gfo, by numerical-relativity simulations of models that are consistent with gravitational waves from the binary neutron star merger gw170817. contrary to the claim made in the literature, we find that binaries with \tilde{{{λ }}}≲ 400 can explain the luminosity of at 2017gfo, as long as moderate mass ejection from the remnant is assumed as had been done in previous work. the reason is that the maximum mass of a neutron star is not strongly correlated with the tidal deformability of neutron stars with a typical mass of ≈1.4 m ⊙. if the maximum mass is so large that the binary does not collapse into a black hole immediately after merger, the mass of the ejecta can be sufficiently large irrespective of the binary tidal deformability. we present models of binary mergers with \tilde{{{λ }}} down to 242 that satisfy the requirement on the mass of the ejecta from the luminosity of at 2017gfo. we further find that the luminosity of at 2017gfo could be explained by models that do not experience bounce after merger. we conclude that the luminosity of at 2017gfo is not very useful for constraining the binary tidal deformability. accurate estimation of the mass ratio will be necessary to establish a lower bound using electromagnetic counterparts in the future. we also caution that merger simulations that employ a limited class of tabulated equations of state could be severely biased due to the lack of generality. | revisiting the lower bound on tidal deformability derived by at 2017gfo |
we explore the possibility that gw150914, the binary black hole (bbh) merger recently detected by advanced ligo, was formed by gravitational interactions in the core of a dense star cluster. using models of globular clusters (gcs) with detailed n-body dynamics and stellar evolution, we show that a typical cluster with a mass of 3× {10}5{m}⊙to 6× {10}5{m}⊙is optimal for forming gw150914-like bbhs that will merge in the local universe. we identify the most likely dynamical processes for forming gw150914 in such a cluster, and we show that the detection of gw150914 is consistent with the masses and merger rates expected for bbhs from gcs. our results show that dynamical processes provide a significant and well-understood pathway for forming bbh mergers in the local universe. understanding the contribution of dynamics to the bbh merger problem is a critical step in unlocking the full potential of gravitational-wave astronomy. | dynamical formation of the gw150914 binary black hole |
we present new (3 +1 )-dimensional numerical relativity simulations of the binary neutron star (bns) mergers that take into account the ns spins. we consider different spin configurations, aligned or antialigned to the orbital angular momentum, for equal- and unequal-mass bnss and for two equations of state. all the simulations employ quasiequilibrium circular initial data in the constant rotational velocity approach, i.e. they are consistent with the einstein equations and in hydrodynamical equilibrium. we study the ns rotation effect on the energetics, the gravitational waves (gws) and on the possible electromagnetic (em) emission associated to dynamical mass ejecta. for dimensionless spin magnitudes of χ ∼0.1 we find that both spin-orbit interactions and spin-induced quadrupole deformations affect the late-inspiral merger dynamics. the latter is, however, dominated by finite-size effects. spin (tidal) effects contribute to gw phase differences up to ∼5 (20) radians accumulated during the last eight orbits to merger. similarly, after merger the collapse time of the remnant and the gw spectrogram are affected by the nss rotation. spin effects in dynamical ejecta are clearly observed in unequal-mass systems in which mass ejection originates from the tidal tail of the companion. consequently kilonovae and other em counterparts are affected by spins. we find that spin aligned to the orbital angular momentum leads to brighter em counterparts than antialigned spin with luminosities up to a factor of 2 higher. | gravitational waves and mass ejecta from binary neutron star mergers: effect of the stars' rotation |
the first direct gravitational-wave detection was made by the advanced laser interferometer gravitational wave observatory on september 14, 2015. the gw150914 signal was strong enough to be apparent, without using any waveform model, in the filtered detector strain data. here, features of the signal visible in the data are analyzed using concepts from newtonian physics and general relativity, accessible to anyone with a general physics background. the simple analysis presented here is consistent with the fully general-relativistic analyses published elsewhere,in showing that the signal was produced by the inspiral and subsequent merger of two black holes. the black holes were each of approximately 35 msun, still orbited each other as close as ~350 km apart, and subsequently merged to form a single black hole. similar reasoning, directly from the data, is used to roughly estimate how far these black holes were from the earth, and the energy that they radiated in gravitational waves. | the basic physics of the binary black hole merger gw150914 |
mergers of stellar-mass black holes (bhs), such as gw150914 observed by laser interferometer gravitational wave observatory (ligo), are not expected to have electromagnetic counterparts. however, the fermi gbm detector identified a γ-ray transient 0.4 s after the gravitational wave (gw) signal gw150914 with consistent sky localization. i show that the two signals might be related if the bh binary detected by ligo originated from two clumps in a dumbbell configuration that formed when the core of a rapidly rotating massive star collapsed. in that case, the bh binary merger was followed by a γ-ray burst (grb) from a jet that originated in the accretion flow around the remnant bh. a future detection of a grb afterglow could be used to determine the redshift and precise localization of the source. a population of standard gw sirens with grb redshifts would provide a new approach for precise measurements of cosmological distances as a function of redshift. | electromagnetic counterparts to black hole mergers detected by ligo |
we present the steps to forecast the sensitivity of the laser interferometer space antenna (lisa) to both a stochastic gravitational wave background and deterministic wave sources. we show how to use these expressions to estimate the precision with which lisa can determine parameters associated with these sources. tools are included to enable easy calculation of the signal-to-noise ratio and draw sensitivity curves. benchmark values are given for easy comparison and checking of methods in the case of three worked examples. the first benchmark is the threshold stochastic gravitational wave background ωgwh2 that lisa can observe. the second is the signal-to-noise ratio that lisa would observe for a binary black hole system identical to gw150914, radiating four years before merger. the third is the case of a monotone source, such as a binary that is far from merger. | lisa for cosmologists: calculating the signal-to-noise ratio for stochastic and deterministic sources |
we study the strong first order electroweak phase transition (sfoewpt) with the so(6)/so(5) composite higgs model, whose scalar sector contains one higgs doublet and one real singlet. six benchmark models are built with fermion embeddings in 1, 6, and 15 of so(6). we show that sfoewpt cannot be triggered under the minimal higgs potential hypothesis, which assumes the scalar potential is dominated by the form factors from the lightest composite resonances. to get a sfoewpt, the contributions from local operators induced by physics above the cutoff scale are needed. we take the 6 + 6 model as an example to investigate the gravitational waves prediction and the related collider phenomenology. | electroweak phase transition with composite higgs models: calculability, gravitational waves and collider searches |
we present a new type of ultracompact objects, featuring lightrings and echoes in the gravitational-wave spectrum. these particle-like solutions arise in einstein-scalar-gauss-bonnet theories in four spacetime dimensions, representing globally regular spacetime manifolds. the scalar field diverges at the center, but the effective stress-energy tensor is free from pathologies. we determine their domain of existence and compare with wormhole solutions, black holes and the fisher solution. | particle-like ultracompact objects in einstein-scalar-gauss-bonnet theories |
we introduce a value-added full-sky catalogue of galaxies, named as galaxy list for the advanced detector era, or glade. the purpose of this catalogue is to (i) help identifications of host candidates for gravitational-wave events, (ii) support target selections for electromagnetic follow-up observations of gravitational-wave candidates, (iii) provide input data on the matter distribution of the local universe for astrophysical or cosmological simulations, and (iv) help identifications of host candidates for poorly localized electromagnetic transients, such as gamma-ray bursts observed with the interplanetary network. both being potential hosts of astrophysical sources of gravitational waves, glade includes inactive and active galaxies as well. glade was constructed by cross-matching and combining data from five separate (but not independent) astronomical catalogues: gwgc, 2mpz, 2mass xsc, hyperleda, and sdss-dr12q. glade is complete up to d_l=37^{+3}_{-4} mpc in terms of the cumulative b-band luminosity of galaxies within luminosity distance dl, and contains all of the brightest galaxies giving half of the total b-band luminosity up to d_l=91 mpc. as b-band luminosity is expected to be a tracer of binary neutron star mergers (currently the prime targets of joint gw+em detections), our completeness measures can be used as estimations of completeness for containing all binary neutron star merger hosts in the local universe. | glade: a galaxy catalogue for multimessenger searches in the advanced gravitational-wave detector era |
strong gravitational lensing of gravitational wave sources offers a novel probe of both the lens galaxy and the binary source population. in particular, the strong lensing event rate and the time-delay distribution of multiply imaged gravitational-wave binary coalescence events can be used to constrain the mass distribution of the lenses as well as the intrinsic properties of the source population. we calculate the strong lensing event rate for a range of second- (2g) and third-generation (3g) detectors, including advanced ligo/virgo, a+, einstein telescope (et), and cosmic explorer (ce). for 3g detectors, we find that ~0.1% of observed events are expected to be strongly lensed. we predict detections of ~1 lensing pair per year with a+, and ~50 pairs per year with et/ce. these rates are highly sensitive to the characteristic galaxy velocity dispersion, σ *, implying that observations of the rates will be a sensitive probe of lens properties. we explore using the time-delay distribution between multiply imaged gravitational-wave sources to constrain properties of the lenses. we find that 3g detectors would constrain σ * to ~21% after 5 yr. finally, we show that the presence or absence of strong lensing within the detected population provides useful insights into the source redshift and mass distribution out to redshifts beyond the peak of the star formation rate, which can be used to constrain formation channels and their relation to the star formation rate and delay-time distributions for these systems. | please repeat: strong lensing of gravitational waves as a probe of compact binary and galaxy populations |
we study gravitational perturbations of slowly rotating black holes in a general effective-field-theory extension of general relativity that includes up to eight-derivative terms. we show that two schrödinger-like equations with spin-dependent effective potentials govern the odd- and even-parity master variables. these equations are coupled for parity-violating corrections, and this coupling affects the quasinormal modes even at linear order in the higher-derivative corrections, due to their isospectrality in general relativity. we provide results for the shifts in the fundamental quasinormal mode frequencies at linear order in the spin, which we expect to be valuable for high-precision phenomenology through future gravitational wave observations. | gravitational ringing of rotating black holes in higher-derivative gravity |
we show that when the gravitational field is treated quantum-mechanically, it induces fluctuations — noise — in the lengths of the arms of gravitational wave detectors. the characteristics of the noise depend on the quantum state of the gravitational field and can be calculated exactly in several interesting cases. for coherent states, the noise is very small, but it can be greatly enhanced in thermal and (especially) squeezed states. detection of this fundamental noise would constitute direct evidence for the quantization of gravity and the existence of gravitons. | the noise of gravitons |
in this work, we present the first experimental upper limits on the presence of stochastic gravitational waves in a frequency band with frequencies above 1 thz. we exclude gravitational waves in the frequency bands from (" separators="2.7 -14 )×1014 hz and (" separators="5 -12 )×1018 hz down to a characteristic amplitude of hcmin≈6 ×10-26 and hcmin≈5 ×10-28 at 95% confidence level, respectively. to obtain these results, we used data from existing facilities that have been constructed and operated with the aim of detecting weakly interacting slim particles, pointing out that these facilities are also sensitive to gravitational waves by graviton to photon conversion in the presence of a magnetic field. the principle applies to all experiments of this kind, with prospects of constraining (or detecting), for example, gravitational waves from light primordial black-hole evaporation in the early universe. | upper limits on the amplitude of ultra-high-frequency gravitational waves from graviton to photon conversion |
white dwarf binaries with orbital periods below 1 h will be the most numerous sources for the space-based gravitational wave detector laser interferometer space antenna (lisa). based on thousands of individually resolved systems, we will be able to constrain binary evolution and provide a new map of the milky way and its close surroundings. in this paper we predict the main properties of populations of different types of detached white dwarf binaries detected by lisa over time. for the first time, we combine a high-resolution cosmological simulation of a milky way-mass galaxy (taken from the fire project) with a binary population synthesis model for low- and intermediate-mass stars. our galaxy model therefore provides a cosmologically realistic star formation and metallicity history for the galaxy and naturally produces its different components such as the thin and thick disc, the bulge, the stellar halo, and satellite galaxies and streams. thanks to the simulation, we show how different galactic components contribute differently to the gravitational wave signal, mostly due to their typical age and distance distributions. we find that the dominant lisa sources will be he-he double white dwarfs (dwds) and he-co dwds with important contributions from the thick disc and bulge. the resulting sky map of the sources is different from previous models, with important consequences for the searches for electromagnetic counterparts and data analysis. we also emphasize that much of the science-enabling information regarding white dwarf binaries, such as the chirp mass and the sky localization, becomes increasingly rich with long observations, including an extended mission up to 8 yr. | predicting the lisa white dwarf binary population in the milky way with cosmological simulations |
recent work applying the notion of pseudospectrum to gravitational physics showed that the quasinormal mode spectrum of black holes is unstable, with the possible exception of the longest-lived (fundamental) mode. the fundamental mode dominates the expected signal in gravitational wave astronomy, and there is no reason why it should have privileged status. we compute the quasinormal mode spectrum of two model problems where the schwarzschild potential is perturbed by a small "bump" consisting of either a pöschl-teller potential or a gaussian, and we show that the fundamental mode is destabilized under generic perturbations. we present phase diagrams and study a simple double-barrier toy problem to clarify the conditions under which the spectral instability occurs. | destabilizing the fundamental mode of black holes: the elephant and the flea |
the speed of gravitational waves provides us a new tool to test alternative theories of gravity. the constraint on the speed of gravitational waves from gw170817 and grb170817a is used to test some classes of horndeski theory. in particular, we consider the coupling of a scalar field to einstein tensor and the coupling of the gauss-bonnet term to a scalar field. the coupling strength of the gauss-bonnet coupling is constrained to be in the order of 10^{-15}. in the horndeski theory we show that in order for this theory to satisfy the stringent constraint on the speed of gws the mass scale m introduced in the non-minimally derivative coupling is constrained to be in the range 10^{15} {gev}≫ m ≳ 2× 10^{-35} gev taking also under consideration the early times upper bound for the mass scale m. the large mass ranges require no fine-tuning because the effect of non-minimally derivative coupling is negligible at late times. | constraints on scalar-tensor theory of gravity by the recent observational results on gravitational waves |
the spin of a black hole retains the memory of how the black hole grew, and can be a potent source of energy for powering relativistic jets. to understand the diagnostic power and astrophysical significance of black hole spin, however, we must first devise observational methods for measuring spin. here, i describe the current state of black hole spin measurements, highlighting the progress made by x-ray astronomers, as well as the current excitement of gravitational wave- and radio astronomy-based techniques. today's spin measurements are already constraining models for the growth of supermassive black holes and giving new insights into the dynamics of stellar core collapse, as well as hinting at the physics of relativistic jet production. future x-ray, radio and gravitational wave observatories will transform black hole spin into a precision tool for astrophysics and test fundamental theories of gravity. | observing black holes spin |
satellite radar altimetry collected during a number of geodetic missions has provided a new understanding of the topography and tectonics of the deep oceans. as altimeter performance and coverage improves, smaller structures are revealed. here we investigate the contribution of six altimeter missions that have been placed into geodetic mapping phases for more than one year. two types of evaluations are performed. we first compare the composite (all six altimeters) grids of east and north vertical deflection to matching grids where one altimeter has been omitted evaluate their contribution versus latitude. we then estimate the noise in each altimeter by computing the median absolute deviation of the profiles with the best composite grid. both analyses show that saral/altika provides the greatest contribution and ers-1 no longer provides any significant improvement. the major limitation for recovering small scale gravity features is the sea surface roughness from ocean waves. there have been steady improvements in instrumentation and processing methods that will continue into the future with higher frequency radars and interferometric swath altimeters planned for future missions. | gravity field recovery from geodetic altimeter missions |
we investigate the nucleosynthesis of heavy elements in the winds ejected by accretion discs formed in neutron star mergers. we compute the element formation in disc outflows from hypermassive neutron star (hmns) remnants of variable lifetime, including the effect of angular momentum transport in the disc evolution. we employ long-term axisymmetric hydrodynamic disc simulations to model the ejecta, and compute r-process nucleosynthesis with tracer particles using a nuclear reaction network containing ∼8000 species. we find that the previously known strong correlation between hmns lifetime, ejected mass and average electron fraction in the outflow is directly related to the amount of neutrino irradiation on the disc, which dominates mass ejection at early times in the form of a neutrino-driven wind. production of lanthanides and actinides saturates at short hmns lifetimes (≲10 ms), with additional ejecta contributing to a blue optical kilonova component for longer-lived hmnss. we find good agreement between the abundances from the disc outflow alone and the solar r-process distribution only for short hmns lifetimes (≲10 ms). for longer lifetimes, the rare-earth and third r-process peaks are significantly underproduced compared to the solar pattern, requiring additional contributions from the dynamical ejecta. the nucleosynthesis signature from a spinning black hole (bh) can only overlap with that from an hmns of moderate lifetime (≲60 ms). finally, we show that angular momentum transport not only contributes with a late-time outflow component, but that it also enhances the neutrino-driven component by moving material to shallower regions of the gravitational potential, in addition to providing additional heating. | signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers |
we study the perturbations to general relativistic black holes (i.e., those without scalar hair) in horndeski scalar-tensor gravity. first, we derive the equations of odd and even parity perturbations of both the metric and scalar field in the case of a schwarzschild black hole, and show that the gravitational waves emitted from such a system contain a mixture of quasinormal mode frequencies from the usual general relativistic spectrum and those from the new scalar field spectrum, with the new scalar spectrum characterized by just two free parameters. we then specialize to the subfamily of horndeski theories in which gravitational waves propagate at the speed of light c on cosmological backgrounds; the scalar quasinormal mode spectrum of such theories is characterized by just a single parameter μ acting as an effective mass of the scalar field. analytical expressions for the quasinormal mode frequencies of the scalar spectrum in this subfamily of theories are provided for both static and slowly rotating black holes. in both regimes comparisons to quasinormal modes calculated numerically show good agreement with those calculated analytically in this work. | quasinormal modes of black holes in horndeski gravity |
we investigate the analytic structure of thermal energy-momentum tensor correlators at large but finite coupling in quantum field theories with gravity duals. we compute corrections to the quasinormal spectra of black branes due to the presence of higher derivative r 2 and r 4 terms in the action, focusing on the dual to n=4 sym theory and gauss-bonnet gravity. we observe the appearance of new poles in the complex frequency plane at finite coupling. the new poles interfere with hydrodynamic poles of the correlators leading to the breakdown of hydrodynamic description at a coupling-dependent critical value of the wave-vector. the dependence of the critical wave vector on the coupling implies that the range of validity of the hydrodynamic description increases monotonically with the coupling. the behavior of the quasinormal spectrum at large but finite coupling may be contrasted with the known properties of the hierarchy of relaxation times determined by the spectrum of a linearized kinetic operator at weak coupling. we find that the ratio of a transport coefficient such as viscosity to the relaxation time determined by the fundamental non-hydrodynamic quasinormal frequency changes rapidly in the vicinity of infinite coupling but flattens out for weaker coupling, suggesting an extrapolation from strong coupling to the kinetic theory result. we note that the behavior of the quasinormal spectrum is qualitatively different depending on whether the ratio of shear viscosity to entropy density is greater or less than the universal, infinite coupling value of ℏ /4π k b . in the former case, the density of poles increases, indicating a formation of branch cuts in the weak coupling limit, and the spectral function shows the appearance of narrow peaks. we also discuss the relation of the viscosity-entropy ratio to conjectured bounds on relaxation time in quantum systems. | from strong to weak coupling in holographic models of thermalization |
in a recent paper (arxiv:1612.00266), we reported the results of the first search for echoes from planck-scale modifications of general relativity near black hole event horizons using the public data release by the advanced ligo gravitational wave observatory. while we found tentative evidence (at $\simeq 3 \sigma$ level) for the presence of these echoes, our statistical methodology was challenged by ashton, et al. (arxiv:1612.05625), just in time for the holidays! in this short note, we briefly address these criticisms, arguing that they either do not affect our conclusion or change its significance by $\lesssim 0.3\sigma$. the real test will be whether our finding can be reproduced by independent groups using independent methodologies (and ultimately more data). | echoes from the abyss: the holiday edition! |
we do a start-to-finish calculation of the stochastic gravitational wave background to be expected from cosmic strings. we start from a population of string loops taken from simulations, smooth these by lorentzian convolution as a model of gravitational backreaction, calculate the average spectrum of gravitational waves emitted by the string population at any given time, and propagate it through a standard model cosmology to find the stochastic background today. except for modeling back reaction as smoothing, we take into account all known effects, including changes in the number of cosmological relativistic degrees of freedom at early times and the possibility that some energy is in rare bursts that we might never have observed. | stochastic gravitational wave background from smoothed cosmic string loops |
the astrophysical origin of gravitational-wave (gw) events is one of the most timely problems in the wake of the ligo/virgo discoveries. in active galactic nuclei (agns), binaries form and evolve efficiently by dynamical interactions and gaseous dissipation. previous studies have suggested that binary black hole (bbh) mergers in agn disks can contribute significantly to bbh mergers observed by gw interferometers. here we examine the distribution of the effective spin parameter χeff of this gw source population. we extend our semi-analytical model of binary formation and evolution in agn disks by following the evolution of the binary orbital angular momenta and black hole (bh) spins. bh spins change due to gas accretion and bh mergers, while the binary orbital angular momenta evolve due to gas accretion and binary-single interactions. we find that the distribution of χeff predicted by our agn model is similar to the distribution observed during ligo/virgo o1 and o2. on the other hand, if radial migration of bhs is inefficient, χeff is skewed toward higher values than the observed distribution, because of the paucity of scattering events that would randomize spin directions relative to the orbital plane. we suggest that high binary masses and the positive correlation between binary mass and the standard deviation of χeff for chirp masses up to $\approx 20\,{m}_{\odot }$ can be possible signatures for mergers originating in agn disks. finally, hierarchical mergers in agn disks naturally produce properties of the recent gw event gw190412, including a low mass ratio, a high primary bh spin, and a significant spin component in the orbital plane. | spin evolution of stellar-mass black hole binaries in active galactic nuclei |
the space-based gravitational wave detector lisa will observe mergers of massive black hole binary systems (mbhbs) to cosmological distances, as well as inspiralling stellar-origin (or stellar-mass) binaries (sbhbs) years before they enter the ligo/virgo band. much remains to be explored for the parameter recovery of both classes of systems. previous mbhb analyses relied on inspiral-only signals and/or a simplified fisher matrix analysis, while sbhbs have not yet been extensively analyzed with bayesian methods. we accelerate likelihood computations by (i) using a fourier-domain response of the lisa instrument, (ii) using a reduced order model for nonspinning waveforms that include a merger-ringdown and higher harmonics, and (iii) setting the noise realization to zero and computing overlaps in the amplitude/phase representation. we present the first simulations of bayesian inference for the parameters of massive black hole systems including consistently the merger and ringdown of the signal, as well as higher harmonics. we clarify the roles of lisa response time and frequency dependencies in breaking degeneracies and illustrate how degeneracy breaking unfolds over time. we also find that restricting the merger-dominated signal to its dominant harmonic can make the extrinsic likelihood very degenerate. including higher harmonics proves to be crucial to breaking degeneracies and considerably improves the localization of the source, with a surviving bimodality in the sky position. we also present simulations of bayesian inference for the extrinsic parameters of sbhbs, and show that although unimodal, their posterior distributions can have non-gaussian features. | exploring the bayesian parameter estimation of binary black holes with lisa |
we present 2-9 ghz radio observations of gw170817 covering the period 125-200 days post-merger, taken with the australia telescope compact array (atca) and the karl g. jansky very large array (vla). our observations demonstrate that the radio afterglow peaked at 149 ± 2 days post-merger and is now declining in flux density. we see no evidence for evolution in the radio-only spectral index, which remains consistent with optically thin synchrotron emission connecting the radio, optical, and x-ray regimes. the peak implies a total energy in the synchrotron-emitting component of a few × 1050 erg. the temporal decay rate is most consistent with mildly or non-relativistic material and we do not see evidence for a very energetic off-axis jet, but we cannot distinguish between a lower-energy jet and more isotropic emission. | a turnover in the radio light curve of gw170817 |
recent detection of gravitational waves from a binary neutron star merger (gw170817) and the subsequent observations of electromagnetic counterparts provide a great opportunity to study the physics of compact binary mergers. the optical and near-infrared counterparts to gw170817 (sss17a, also known as at 2017gfo or dlt17ck) are found to be consistent with a kilonova/macronova scenario with red and blue components. however, in most previous studies wherein the contribution from each ejecta component to the lightcurves is separately calculated and composited, the red component is too massive of a dynamical ejecta, and the blue component is too fast of a post-merger ejecta. in this letter, we perform a two-dimensional radiative transfer simulation for a kilonova/macronova, consistently taking the interplay of multiple ejecta components into account. we show that the lightcurves and photospheric velocity of sss17a can be reproduced naturally by a setup that is consistent with the prediction of the numerical-relativity simulations. | radiative transfer simulation for the optical and near-infrared electromagnetic counterparts to gw170817 |
we study gravitational waves induced from the primordial scalar perturbations at second order around the reheating of the universe. we consider reheating scenarios in which a transition from an early matter-dominated era to the radiation-dominated era completes within a timescale much shorter than the hubble time at that time. we find that an enhanced production of induced gravitational waves occurs just after the reheating transition because of fast oscillations of scalar modes well inside the hubble horizon. this enhancement mechanism just after an early matter-dominated era is much more efficient than a previously known enhancement mechanism during an early matter era, and we show that the induced gravitational waves could be detectable by future observations if the reheating temperature tr is in the range tr≲7 ×10-2 gev or 20 gev ≲tr≲2 ×107 gev . this is the case even if the scalar perturbations on small scales are not enhanced relative to those on large scales, probed by the observations of the cosmic microwave background. | enhancement of gravitational waves induced by scalar perturbations due to a sudden transition from an early matter era to the radiation era |
the disintegration of the eastern antarctic peninsula's larsen a and b ice shelves has been attributed to atmosphere and ocean warming, and increased mass losses from the glaciers once restrained by these ice shelves have increased antarctica's total contribution to sea-level rise. abrupt recessions in ice-shelf frontal position presaged the break-up of larsen a and b, yet, in the ~20 years since these events, documented knowledge of frontal change along the entire ~1,400-km-long eastern antarctic peninsula is limited. here, we show that 85% of the seaward ice-shelf perimeter fringing this coastline underwent uninterrupted advance between the early 2000s and 2019, in contrast to the two previous decades. we attribute this advance to enhanced ocean-wave dampening, ice-shelf buttressing and the absence of sea-surface slope-induced gravitational ice-shelf flow. these phenomena were, in turn, enabled by increased near-shore sea ice driven by a weddell sea-wide intensification of cyclonic surface winds around 2002. collectively, our observations demonstrate that sea-ice change can either safeguard from, or set in motion, the final rifting and calving of even large antarctic ice shelves. | antarctic ice-shelf advance driven by anomalous atmospheric and sea-ice circulation |
the knowledge of the higgs potential is crucial for understanding the origin of mass and the thermal history of our universe. we show how collider measurements and observations of stochastic gravitational wave signals can complement each other to explore the multiform scalar potential in the two higgs doublet model (2hdm). accounting for theoretical and current experimental constraints, we analyze the key ingredients in the shape of the higgs potential triggering the transmutation in phase transition, from the smooth crossover to the strong first-order phase transition (ξc>1 ), focusing on the barrier formation and the upliftment of the true vacuum. in particular, we observe that the ξc>1 regime is favored for lower scalar masses, rendering strong extra motivation for collider searches. we contrast the dominant collider signals at the hl-lhc (high-luminosity lhc) with observable gravitational wave signals at lisa. we obtain that the hl-lhc will be able to cover a vast range of the ξc>1 parameter space, with scalar decays to heavy fermions (h ,a ,h±→t t ,t b ) being the most promising smoking gun signature of a strong first-order electroweak phase transition in the 2hdm. | electroweak phase transition in the 2hdm: collider and gravitational wave complementarity |
optically levitated nonspherical particles in vacuum are excellent candidates for torque sensing, rotational quantum mechanics, high-frequency gravitational wave detection, and multiple other applications. many potential applications, such as detecting the casimir torque near a birefringent surface, require simultaneous cooling of both the center-of-mass motion and the torsional vibration (or rotation) of a nonspherical nanoparticle. here we report five-dimensional cooling of a levitated nanoparticle. we cool the three center-of-mass motion modes and two torsional vibration modes of a levitated nanodumbbell in a linearly polarized laser simultaneously. the only uncooled rigid-body degree of freedom is the rotation of the nanodumbbell around its long axis. this free rotation mode does not couple to the optical tweezers directly. surprisingly, we observe that it strongly affects the torsional vibrations of the nanodumbbell. this work deepens our understanding of the nonlinear dynamics and rotation coupling of a levitated nanoparticle and paves the way towards full quantum control of its motion. | five-dimensional cooling and nonlinear dynamics of an optically levitated nanodumbbell |
we employ scattering amplitudes in curved space to model the dynamics of a light probe particle with mass $m$ orbiting in the background spacetime induced by a heavy gravitational source with mass $m$. observables are organized as an expansion in $m/m$ to all orders in $g$ -- the gravitational self-force expansion. an essential component of our analysis is the backreaction of the heavy source which we capture by including the associated light degrees of freedom. as illustration we consider a schwarzschild background and verify geodesic motion as well as the first-order self-force correction to two-body scattering through ${\cal o}(g^3)$. amplitudes in curved space offer several advantages, and further developments along these lines may advance the computation of gravitational-wave signals for extreme-mass-ratio inspirals. | gravitational self force from scattering amplitudes in curved space |
when two galaxies merge, they often produce a supermassive black hole binary (smbhb) at their center. numerical simulations with cold dark matter show that smbhbs typically stall out at a distance of a few parsecs apart, and take billions of years to coalesce. this is known as the final parsec problem. we suggest that ultralight dark matter (uldm) halos around smbhbs can generate dark matter waves due to gravitational cooling. these waves can effectively carry away orbital energy from the black holes, rapidly driving them together. to test this hypothesis, we performed numerical simulations of black hole binaries inside uldm halos. our results imply that uldm waves can lead to the rapid orbital decay of black hole binaries. | final parsec problem of black hole mergers and ultralight dark matter |
both lisa and taiji, planned space-based gravitational-wave detectors in orbit around the sun, are expected to launch in 2030-2035. assuming a one-year overlap, we explore a potential lisa-taiji network to fast and accurately localize the gravitational-wave sources. | the lisa-taiji network |
neutron star binaries and their associated gravitational wave signal facilitate precision tests of general relativity. any deviation of the detected gravitational waveform from general relativity would therefore be a smoking gun signature of new physics, in the form of additional forces, dark matter particles, or extra gravitational degrees of freedom. to be able to probe new theories, precise knowledge of the expected waveform is required. in our work, we consider a generic setup by augmenting general relativity with an additional, massive scalar field. we then compute the inspiral dynamics of a binary system by employing an effective field theoretical approach, while giving a detailed introduction to the computational framework. finally, we derive the modified gravitational waveform at next-to-leading order. as a consequence of our model-agnostic approach, our results are readily adaptable to a plethora of new physics scenarios, including modified gravity theories and scalar dark matter models. | binary systems in massive scalar-tensor theories: next-to-leading order gravitational waveform from effective field theory |
the scalar-induced gravitational waves (sigw), arising from large amplitude primordial density fluctuations, provide a unique observational test for directly probing the epoch of inflation. in this work, we provide constraints on the sigw background by taking into account the non-gaussianity in the primordial density fluctuations, using the third observing run (o3) data of the ligo-virgo-kagra collaboration. we find that the non-gaussianity gives a non-negligible effect on the gw energy density spectrum and starts to affect the analysis of the o3 data when the non-gaussianity parameter is $f_{\rm nl} > 3.55$. furthermore, the constraints exhibit asymptotic behavior given by $f_{\rm nl} a_g = \rm{const.}$ at large $f_{\rm nl}$ limit, where $a_g$ denotes the amplitude of the curvature perturbations. in the limit of large $f_{\rm nl}$, we placed a 95% confidence level upper limit $f_{\rm nl} a_g \leq 0.13, 0.09, 0.10$ at fixed scales of $10^{16}, 10^{16.5}, 10^{17}~{\rm mpc}^{-1}$, respectively. | constraints on non-gaussian primordial curvature perturbation from the ligo-virgo-kagra third observing run |
in the presence of electromagnetic fields, both axions and gravitational waves (gws) induce oscillating magnetic fields: a potentially detectable fingerprint of their presence. we demonstrate that the response is largely dictated by the symmetries of the instruments used to search for it. focussing on low mass axion haloscopes, we derive selection rules that determine the parametric sensitivity of different detector geometries to axions and gws, and which further reveal how to optimise the experimental geometry to maximise both signals. the formalism allows us to forecast the optimal sensitivity to gws in the range of 100 khz to 100 mhz for instruments such as abracadabra, base, admx slic, shaft, wisplc, and dmradio. | symmetries and selection rules: optimising axion haloscopes for gravitational wave searches |
the gravitational waves emitted (some time) after two black holes merge are well described by the theory of linear perturbations on a spacetime characterized by the mass and spin of the remnant. however, in the very early stages right after merger, both the mass and spin are changing. in this work we explore, in a set up based on vaidya's spacetime, the dynamical consequences of a change of mass in the spacetime due to the accretion of null matter (for example, gravitational waves). we show that accretion imprints time-dependent frequencies and amplitude to a ringdown waveform, and we show how to model accurately this effect in certain regimes. we also comment on the direct emission of gravitational waves due to perturbations in the in--falling matter, which is of relevance for black holes embedded in astrophysical environments. | ringdown of a dynamical spacetime |
we present calculations of the wide angle emission of short-duration gamma-ray bursts from compact binary merger progenitors. such events are expected to be localized by their gravitational wave emission, fairly irrespective of the orientation of the angular momentum vector of the system, along which the gamma-ray burst outflow is expected to propagate. we show that both the prompt and afterglow emission are dim and challenging to detect for observers lying outside the cone within which the relativistic outflow is propagating. if the jet initially propagates through a baryon contaminated region surrounding the merger site, however, a hot cocoon forms around it. the cocoon subsequently expands quasi-isotropically producing its own prompt emission and external shock powered afterglow. we show that the cocoon prompt emission is detectable by swift bat and fermi gbm. we also show that the cocoon afterglow peaks a few hours to a few days after the burst and is detectable for up to a few weeks at all wavelengths. the timing and brightness of the transient are however uncertain due to their dependence on unknown quantities such as the density of the ambient medium surrounding the merger site, the cocoon energy and the cocoon lorentz factor. for a significant fraction of the gravitationally detected neutron-star-binary mergers, the cocoon afterglow could possibly be the only identifiable electromagnetic counterpart, at least at radio and x-ray frequencies. | off-axis emission of short γ-ray bursts and the detectability of electromagnetic counterparts of gravitational-wave-detected binary mergers |
in this study, we investigated the cosmological implications of a complex singlet scalar $ {\cal{s}}$ with non-trivial $ b-l$ charges in the conformal $ u(1)_{b-l}$ theory. it was found that, in a sizable region of parameter space, $ {\cal{s}}$ may disturb the resonant leptogenesis mechanism, which is used to generate baryon asymmetry, and affect the symmetry breaking dynamics in the strong first order phase transition. the stochastic gravitational waves (gws) produced at the phase transition can be probed in future gw experiments. the gw searches prefer a relatively light $ {\cal{s}}$ at the tev-scale; however, this is difficult to detect directly at future high-energy colliders. *the work of l.b. is supported by the national natural science foundation of china (12075041, 12047564), the fundamental research funds for the central universities of china (2021cdjqy-011, 2020cdjqy-z003), chongqing natural science foundation (cstc2020jcyj-msxmx0814). w.c. is supported by the china postdoctoral science foundation (2019tq0329). h.g. is partially supported by the u.s. department of energy grant (de-sc0009956). y.z. is supported by the us department of energy (de-sc0017987) | cosmological implications of a b - l charged hidden scalar: leptogenesis and gravitational waves |
hierarchical mergers are one of the distinctive signatures of binary black hole (bbh) formation through dynamical evolution. here, we present a fast semi-analytic approach to simulate hierarchical mergers in nuclear star clusters (nscs), globular clusters (gcs) and young star clusters (yscs). hierarchical mergers are more common in nscs than they are in both gcs and yscs, because of the different escape velocity. the mass distribution of hierarchical bbhs strongly depends on the properties of first-generation bbhs, such as their progenitor's metallicity. in our fiducial model, we form black holes (bhs) with masses up to $\sim{}10^3$ m$_\odot$ in nscs and up to $\sim{}10^2$ m$_\odot$ in both gcs and yscs. when escape velocities in excess of 100 km~s$^{-1}$ are considered, bhs with mass $>10^3$ m$_\odot$ are allowed to form in nscs. hierarchical mergers lead to the formation of bhs in the pair instability mass gap and intermediate-mass bhs, but only in metal-poor environments. the local bbh merger rate in our models ranges from $\sim{}10$ to $\sim{} 60$ gpc$^{-3}$ yr$^{-1}$; hierarchical bbhs in nscs account for $\sim{}10^{-2}- 0.2$ gpc$^{-3}$ yr$^{-1}$, with a strong upper limit of $\sim{}10$ gpc$^{-3}$ yr$^{-1}$. when comparing our models with the second gravitational-wave transient catalog, we find that multiple formation channels are favored to reproduce the observed bbh population. | mass and rate of hierarchical black hole mergers in young, globular and nuclear star clusters |
black holes are unique among astrophysical sources: they are the simplest macroscopic objects in the universe, and they are extraordinary in terms of their ability to convert energy into electromagnetic and 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. | probing the nature of black holes: deep in the mhz gravitational-wave sky |
recent photometric observations of massive stars have identified a low-frequency power excess which appears as stochastic low-frequency variability in light curve observations. we present the oscillation properties of high resolution hydrodynamic simulations of a 25 $\mathrm{m}_\odot$ star performed with the ppmstar code. the model star has a convective core mass of $\approx\, 12\, \mathrm{m}_\odot$ and approximately half of the envelope simulated. from this simulation, we extract light curves from several directions, average them over each hemisphere, and process them as if they were real photometric observations. we show how core convection excites waves with a similar frequency as the convective time scale in addition to significant power across a forest of low and high angular degree $l$ modes. we find that the coherence of these modes is relatively low as a result of their stochastic excitation by core convection, with lifetimes on the order of 10s of days. thanks to the still significant power at higher $l$ and this relatively low coherence, we find that integrating over a hemisphere produces a power spectrum that still contains measurable power up to the brunt--väisälä frequency. these power spectra extracted from the stable envelope are qualitatively similar to observations, with same order of magnitude yet lower characteristic frequency. this work further shows the potential of long-duration, high-resolution hydrodynamic simulations for connecting asteroseismic observations to the structure and dynamics of core convection and the convective boundary. | 3d hydrodynamic simulations of massive main-sequence stars ii. convective excitation and spectra of internal gravity waves |
parity violation in the gravitational sector is a prediction of many theories beyond general relativity. in the propagation of gravitational waves, parity violation manifests by inducing amplitude and/or velocity birefringence between right- and left-circularly polarized modes. we study how the stochastic gravitational wave background can be used to place constraints on these birefringent effects. we consider two model scenarios, one in which we allow birefringent corrections to become arbitrarily large, and a second in which we impose stringent theory priors. in the former, we place constraints on a generic birefringent gravitational-wave signal due to the current non-detection of a stochastic background from compact binary events. we find a joint constraint on birefringent parameters, $\kappa_d$ and $\kappa_z$, of $\mathcal{o}(10^{-1})$. in the latter scenario, we forecast constraints on parity violating theories resulting from observations of the future upgraded ligo-virgo-kagra network as well as proposed third-generation detectors. we find that third-generation detectors will be able to improve the constraints by at least two orders of magnitude, yielding new stringent bounds on parity violating theories. this work introduces a novel and powerful probe of gravitational parity violation with gravitational-wave data. | a new probe of gravitational parity violation through (non-)observation of the stochastic gravitational-wave background |
general relativity (gr) yields a number of gravitational wave memory effects that correspond to symmetries of spacetime infinitely far away from gravitational fields. these symmetries and memory effects hint at the fundamental mathematical connection between gravity and quantum fields in the low-energy "infrared" regime. in this study, we propose to shift the paradigm of memory from merely a target in gravitational wave searches to a unique way of measuring symmetries of nature. thus, we extend previous memory detection efforts to the proof-of-principle parameter estimation and model selection. through simulating binary black hole (bbh) mergers in scenarios where spacetime exhibits certain sets of bondi-metzner-sachs symmetries, we point out that both the current and the future gravitational wave observatories are excellent probes of spacetime symmetries. in particular, the design sensitivity of the proposed einstein telescope (et) allows to constrain the strain amplitude of the leading-order displacement memory, associated with superrotational symmetries, to a 2% level in one year. whereas the weaker spin memory amplitude can be constrained to a 22% level, providing a pathway to probe superrotational symmetries. finally, there is almost no doubt among gr experts that displacement memory exists in nature, although its effect on parameter estimation was largely neglected in the predictions of the science output of future experiments such as lisa and et. we find that it may lead to an overestimation of the measurement uncertainties for inferred parameters of the loudest bbh mergers by the order of 10%. | inferring fundamental spacetime symmetries with gravitational-wave memory: from lisa to the einstein telescope |
general relativity, though the most successful theory of gravity, has been continuously modified to resolve its incompatibility with quantum mechanics and explain the origin of dark energy or dark matter. one way to test these modified gravity theories is to study the gravitational waves emitted during the ringdown of binary mergers, which consist of quasinormal modes. in several modified gravity theories, the even- and odd-parity gravitational perturbations of non-rotating and slowly rotating black holes have different quasinormal mode frequencies, breaking the isospectrality of general relativity. for black holes with arbitrary spin in modified gravity, there were no avenues to compute quasinormal modes except numerical relativity, until recent extensions of the teukolsky formalism. in this work, we describe how to use the modified teukolsky formalism to study isospectrality breaking in modified gravity. we first introduce how definite-parity modes are defined through combinations of weyl scalars in general relativity, and then, we extend this definition to modified gravity. we then use the eigenvalue perturbation method to show how the degeneracy in quasinormal mode frequencies of different parity is broken in modified gravity. to demonstrate our analysis, we also apply it to some specific modified gravity theories. our work lays the foundation for studying isospectrality breaking of quasinormal modes in modified gravity for black holes with arbitrary spin. | isospectrality breaking in the teukolsky formalism |
hot viscous plasmas unavoidably emit a gravitational wave background, similar to the electromagnetic black body radiation. we study the contribution from hidden particles to the diffuse background emitted by the primordial plasma in the early universe. while this contribution can easily dominate over that from standard model particles, we find that both are capped by a generic upper bound that makes them difficult to detect with interferometers in the foreseeable future. however, resonant cavity experiments could potentially observe backgrounds that saturate the upper bound. we illustrate our results for axions and heavy neutral leptons. finally, our results suggest that previous works overestimated the gravitational wave background from particle decays out of thermal equilibrium. | upper bound on thermal gravitational wave backgrounds from hidden sectors |
we show that large gauge transformations modify the structure of momentum conservation leading to non-vanishing three-point amplitudes in a simple toy model of a gravitational wave event. this phenomenon resolves an apparent tension between perturbative scattering amplitude computations and exact methods in field theory. the tension is resolved to all orders of perturbation theory once large gauge effects are included via a modified lsz prescription; if they are omitted, perturbative methods only recover a subset of terms in the full non-perturbative expression. although our results are derived in the context of specific examples, several aspects of our work have analogues in dynamical gravitational scattering processes. | large gauge effects and the structure of amplitudes |
direct detection of gravitational waves and binary black hole mergers have proven to be remarkable investigations of general relativity. in order to have a definitive answer as to whether the black hole spacetime under test is the kerr or non-kerr, one requires accurate mapping of the metric. since emris are perfect candidates for space-based detectors, laser interferometer space antenna (lisa) observations will serve a crucial purpose in mapping the spacetime metric. in this article, we consider such a study with the johannsen spacetime that captures the deviations from the kerr black hole and further discuss their detection prospects. we analytically derive the leading order post-newtonian corrections in the average loss of energy and angular momentum fluxes generated by a stellar-mass object exhibiting eccentric equatorial motion in the johannsen background. we further obtain the orbital evolution of the inspiralling object within the adiabatic approximation and estimate the orbital phase. we lastly provide the possible detectability of deviations from the kerr black hole by estimating gravitational wave dephasing and highlight the crucial role of lisa observations. | prospects of detecting deviations to kerr geometry with radiation reaction effects in emris |
we study the inflationary phenomenology of a non-minimally coupled einstein-gauss-bonnet gravity theory, in the presence of a scalar potential, under the condition that the gravitational wave speed of the primordial gravitational waves is equal to unity, that is ct2 = 1 , in natural units. the equations of motion, which are derived directly from the gravitational action, form a system of differential equations with respect to hubble's parameter and the inflaton field which are very complicated and cannot be solved analytically, even in the minimal coupling case. in this paper, we present a variety of different approximations which could be used, along with the constraint ct2 = 1 , in order to produce an inflationary phenomenology compatible with recent observations. all the different approaches are able to lead to viable results if the model coupling functions obey simple relations, however, different approaches contain different approximations which must be obeyed during the first horizon crossing, in order for the model to be rendered correct. models which may lead to a non-viable phenomenology are presented as well in order to understand better the inner framework of this theory. furthermore, since the velocity of the gravitational waves is set equal to ct2 = 1 , as stated by the striking event of gw170817 recently, the non-minimal coupling function, the gauss-bonnet scalar coupling and the scalar potential are related to each other. here, we shall assume no particular form of the scalar potential and we choose freely the scalar functions coupled to the ricci scalar and the gauss-bonnet invariant. certain models are also studied in order to assess the phenomenological validity of the theory, but we need to note that all approximations must hold true in order for a particular model to be valid. finally, even though each possible approach assumes different approximations, we summarize them in the last section for the sake of completeness. | non-minimally coupled einstein-gauss-bonnet inflation phenomenology in view of gw170817 |
we report on the realization of a matter-wave interferometer based on single-photon interaction on the ultranarrow optical clock transition of strontium atoms. we experimentally demonstrate its operation as a gravimeter and as a gravity gradiometer. no reduction of interferometric contrast was observed for a total interferometer time up to ∼10 ms , limited by geometric constraints of the apparatus. single-photon interferometers represent a new class of high-precision sensors that could be used for the detection of gravitational waves in so far unexplored frequency ranges and to enlighten the boundary between quantum mechanics and general relativity. | atom interferometry with the sr optical clock transition |
high-accuracy gravitational-wave modeling demands going beyond linear, first-order perturbation theory. particularly motivated by the need for second-order perturbative models of extreme-mass-ratio inspirals and black hole ringdowns, we present practical spherical-harmonic decompositions of the einstein equation, regge-wheeler-zerilli equations, and teukolsky equation at second perturbative order in a schwarzschild background. our formulations are covariant on the $t$--$r$ plane and on the two-sphere, and we express the field equations in terms of gauge-invariant metric perturbations. in a companion \pkg{mathematica} package, \pkg{perturbationequations}, we provide these invariant formulas as well as the analogous formulas in terms of raw, gauge-dependent metric perturbations. our decomposition of the second-order einstein equation, when specialized to the lorenz gauge, was a key ingredient in recent second-order self-force calculations~[phys. rev. lett. 124, 021101 (2020); ibid. 127, 151102 (2021); ibid. 130, 241402 (2023)]. | second-order perturbations of the schwarzschild spacetime: practical, covariant and gauge-invariant formalisms |
the third observing run of advanced ligo and advanced virgo took place between 2019 april and 2020 march and resulted in dozens of gravitational-wave candidates, many of which are now published as confident detections. a crucial requirement of the third observing run was the rapid identification and public reporting of compact binary mergers, which enabled massive follow-up observation campaigns with electromagnetic and neutrino observatories. pycbc live is a low-latency search for compact binary mergers based on frequency-domain matched filtering, which was used during the second and third observing runs, together with other low-latency analyses, to generate these rapid alerts from the data acquired by ligo and virgo. this paper describes and evaluates the improvements made to pycbc live after the second observing run, which defined its operation and performance during the third observing run. | real-time search for compact binary mergers in advanced ligo and virgo's third observing run using pycbc live |
we complete our previous derivation, at the sixth post-newtonian (6pn) accuracy, of the local-in-time dynamics of a gravitationally interacting two-body system by giving two gauge-invariant characterizations of its complementary nonlocal-in-time dynamics. on the one hand, we compute the nonlocal part of the scattering angle for hyberboliclike motions; and, on the other hand, we compute the nonlocal part of the averaged (delaunay) hamiltonian for ellipticlike motions. the former is computed as a large-angular-momentum expansion (given here to next-to-next-to-leading order), while the latter is given as a small-eccentricity expansion (given here to the tenth order). we note the appearance of ζ (3 ) in the nonlocal part of the scattering angle. the averaged hamiltonian for ellipticlike motions then yields two more gauge-invariant observables: the energy and the periastron precession as functions of orbital frequencies. we point out the existence of a hidden simplicity in the mass-ratio dependence of the gravitational-wave energy loss of a two-body system. we include a supplemental material that gives the explicit analytic form of a scattering integral which we could only evaluate numerically. | sixth post-newtonian nonlocal-in-time dynamics of binary systems |
the south pole telescope (spt) has systematically identified 81 high-redshift, strongly gravitationally lensed, dusty star-forming galaxies (dsfgs) in a 2500 square degree cosmological millimeter-wave survey. we present the final spectroscopic redshift survey of this flux-limited (s870 μm > 25 mjy) sample, initially selected at 1.4 mm. the redshift survey was conducted with the atacama large millimeter/submillimeter array across the 3 mm spectral window, targeting carbon monoxide line emission. by combining these measurements with ancillary data, the spt sample is now spectroscopically complete, with redshifts spanning 1.9 < z < 6.9 and a median of $z=3.9\pm 0.2$ . we present the millimeter through far-infrared photometry and spectral energy density fits for all sources, along with their inferred intrinsic properties. comparing the properties of the spt sources to the unlensed dsfg population, we demonstrate that the spt-selected dsfgs represent the most extreme infrared-luminous galaxies, even after accounting for strong gravitational lensing. the spt sources have a median star formation rate of $2.3(2)\times {10}^{3}{m}_{\odot }\,\,{\mathrm{yr}}^{-1}$ and a median dust mass of $1.4(1)\times {10}^{9}{m}_{\odot }$ . however, the inferred gas depletion timescales of the spt sources are comparable to those of unlensed dsfgs, once redshift is taken into account. this spt sample contains roughly half of the known spectroscopically confirmed dsfgs at z > 5, making this the largest sample of high-redshift dsfgs to date, and enabling the "high-redshift tail" of extremely luminous dsfgs to be measured. though galaxy formation models struggle to account for the spt redshift distribution, the larger sample statistics from this complete and well-defined survey will help inform future theoretical efforts. | the complete redshift distribution of dusty star-forming galaxies from the spt-sz survey |
axion inflation coupled to abelian gauge fields via a chern-simons-like term of the form ϕf f ~ represents an attractive inflationary model with a rich phenomenology, including the production of magnetic fields, black holes, gravitational waves, and the matter-antimatter asymmetry. in this work, we focus on a particular regime of axion inflation, the so-called anber-sorbo (as) solution, in which the energy loss in the gauge-field production provides the dominant source of friction for the inflaton motion. we revisit the as solution and confirm that it is unstable. contrary to earlier numerical works that attempted to reach the as solution starting from a regime of weak backreaction, we perform, for the first time, a numerical evolution starting directly from the regime of strong backreaction. our analysis strongly suggests that, at least as long as one neglects spatial inhomogeneities in the inflaton field, the as solution has no basin of attraction, not even a very small one that might have been missed in previous numerical studies. our analysis employs an arsenal of analytical and numerical techniques, some established and some newly introduced, including (1) linear perturbation theory along the lines of ref. [1], (2) the gradient expansion formalism (gef) developed in ref. [2], (3) a new linearized version of the gef, and (4) the standard mode-by-mode approach in momentum space in combination with input from the gef. all these methods yield consistent results confirming the instability of the as solution, which renders the dynamics of axion inflation in the strong-backreaction regime even more interesting than previously believed. | axion inflation in the strong-backreaction regime: decay of the anber-sorbo solution |
the presence of extra dimensions generically modify the spacetime geometry of a rotating black hole, by adding an additional hair, besides the mass m and the angular momentum j, known as the `tidal charge' parameter, β . in a braneworld scenario with one extra spatial dimension, the extra dimension is expected to manifest itself through - (a) negative values of β , and (b) modified gravitational perturbations. this in turn would affect the quasi-normal modes of rotating black holes. we numerically solve the perturbed gravitational field equations using the continued fractions method and determine the quasi-normal mode spectra for the braneworld black hole. we find that increasingly negative values of β correspond to a diminishing imaginary part of the quasi-normal mode, or equivalently, an increasing damping time. using the publicly available data of the properties of the remnant black hole in the gravitational wave signal gw150914, we check for consistency between the predicted values (for a given β ) of the frequency and damping time of the least-damped ℓ =2 ,m =2 quasi-normal mode and measurements of these quantities using other independent techniques. we find that it is highly unlikely for the tidal charge, β ≲-0.05 , providing a conservative limit on the tidal charge parameter. implications and future directions are discussed. | constraining extra dimensions using observations of black hole quasi-normal modes |
perturbative quantum corrections to primordial power spectra are important for testing the robustness and the regime of validity of inflation as an effective field theory. although this has been done extensively for the density power spectrum (and, to some extent, for the tensor spectrum) using loop corrections, we do so in an open quantum system approach to the problem. specifically, we calculate the first-order corrections to the primordial gravitational wave spectrum due to (cubic) tensor interactions alone. we show that our results match expectations from standard loop corrections only in the strict markovian limit, and therefore, establish a systematic way to relax this approximation in the future, as is generally necessary for gravitational systems. | quantum corrections to the primordial tensor spectrum: open efts & markovian decoupling of uv modes |
this study explores the generation of the observed baryon asymmetry of the universe within the complex two-higgs doublet model (c2hdm) while considering theoretical and current experimental constraints. in our investigation, we analyze critical elements of the higgs potential to understand the phase-transition pattern. specifically, we examine the formation of the barrier and the uplifting of the true vacuum state, which play crucial roles in facilitating a strong first-order phase transition. furthermore, we explore the potential gravitational wave signals associated with this phase transition pattern and investigate the parameter space points that can be probed with lisa. finally, we compare the impact of different approaches to describing the bubble profile on the calculation of the baryon asymmetry. we contrast the typically used kink profile approximation against the explicit solution of the tunneling profile. we find that a non-negligible range of the c2hdm parameter space results in significant discrepancies in the baryon asymmetry estimation between these two approaches. through an examination of the parameter space, we identify a benchmark point that satisfies the observed baryon asymmetry. | gravitational waves, bubble profile, and baryon asymmetry in the complex 2hdm |
extreme mass-ratio inspirals (emris), namely binary systems composed of a massive black hole and a compact stellar-mass object, are anticipated to be among the gravitational wave (gw) sources detected by the laser interferometer space antenna (lisa). similarly to compact binary mergers detected by current gw detectors, emris can be used as cosmic rulers to probe the expansion of the universe. motivated by tensions in current cosmological observations as well as by alternative models of dark energy, modified gravity theories can affect the propagation of gws across cosmological distances, with modifications commonly parametrised in terms of two phenomenological parameters, $\xi_0$ and $n$. in this work we adopt a bayesian approach to constrain for the first time parametrised deviations from general relativity using the loudest simulated emris detected by lisa as dark sirens with a simulated galaxy catalog. assuming all the cosmological parameters except $\xi_0$ are already tightly constrained, our forecasts show that $\xi_0$ can be constrained to a few percent level (90% c.i.) with 4 years of lisa observations, unless emri detection rates turn out to be closer to current pessimistic expectations. these results quickly degrade if additional cosmological parameters are inferred simultaneously, but become more robust with an extended lisa observation period of 10 years. overall, we find that emris with lisa are better at constraining modified gw propagation than current second-generation ground-based gw detectors, but they will only be comparable to third-generation detectors in the most optimistic scenarios. | probing modified gravitational-wave propagation with extreme mass-ratio inspirals |
extreme mass ratio inspirals (emris) are one of the key sources for future space-based gravitational wave interferometers. measurements of emri gravitational waves are expected to determine the characteristics of their sources with sub-percent precision. however, their waveform generation is challenging due to the long duration of the signal and the high harmonic content. here, we present the first ready-to-use schwarzschild eccentric emri waveform implementation in the frequency domain for use with either graphics processing units (gpus) or central processing units (cpus). we present the overall waveform implementation and test the accuracy and performance of the frequency domain waveforms against the time domain implementation. on gpus, the frequency domain waveform takes in median $0.044$ seconds to generate and is twice as fast to compute as its time domain counterpart when considering massive black hole masses $\geq 2 \times 10^6 \,{\rm m_\odot}$ and initial eccentricities $e_0 > 0.2$. on cpus, the median waveform evaluation time is $5$ seconds, and it is five times faster in the frequency domain than in the time domain. using a sparser frequency array can further speed up the waveform generation, reaching up to $ 0.3$ seconds. this enables us to perform, for the first time, emri parameter inference with fully relativistic waveforms on cpus. future emri models which encompass wider source characteristics (particularly black hole spin and generic orbit geometries) will require significantly more harmonics. frequency-domain models will be essential analysis tools for these astrophysically realistic and important signals. | fast and fourier: extreme mass ratio inspiral waveforms in the frequency domain |
the minimal-length paradigm, a possible implication of quantum gravity at low energies, is commonly understood as a phenomenological modification of heisenberg's uncertainty relation. we show that this modification is equivalent to a cut-off in the space conjugate to the position representation, i.e. the space of wave numbers, which does not necessarily correspond to momentum space. this result is generalized to several dim ensions and noncommutative geometries once a suitable definition of the wave number is provided. furthermore, we find a direct relation between the ensuing bound in wave-number space and the minimal-length scale. for scenarios in which the existence of the minimal length cannot be explicitly verified, the proposed framework can be used to clarify the situation. indeed, applying it to common models, we find that one of them does, against all expectations, allow for arbitrary precision in position measurements. in closing, we comment on general implications of our findings for the field. in particular, we point out that the minimal length is purely kinematical such that, effectively, it is not influenced by the overlying dynamics and the choice of hamiltonian. | minimal length: a cut-off in disguise? |
using ground-based gravitational-wave detectors, we probe the mass function of intermediate-mass black holes (imbhs) wherein we also include bhs in the upper mass gap at ~60-130 m ⊙. employing the projected sensitivity of the upcoming ligo and virgo fourth observing run (o4), we perform bayesian analysis on quasi-circular nonprecessing, spinning imbh binaries (imbhbs) with total masses 50-500 m ⊙, mass ratios 1.25, 4, and 10, and dimensionless spins up to 0.95, and estimate the precision with which the source-frame parameters can be measured. we find that, at 2σ, the mass of the heavier component of imbhbs can be constrained with an uncertainty of ~10%-40% at a signal-to-noise ratio of 20. focusing on the stellar-mass gap with new tabulations of the 12c(α, γ)16o reaction rate and its uncertainties, we evolve massive helium core stars using mesa to establish the lower and upper edges of the mass gap as ≃ ${59}_{-13}^{+34}$ m ⊙ and ≃ ${139}_{-14}^{+30}$ m ⊙ respectively, where the error bars give the mass range that follows from the ±3σ uncertainty in the 12c(α, γ)16o nuclear reaction rate. we find that high resolution of the tabulated reaction rate and fine temporal resolution are necessary to resolve the peak of the bh mass spectrum. we then study imbhbs with components lying in the mass gap and show that the o4 run will be able to robustly identify most such systems. finally, we reanalyze gw190521 with a state-of-the-art aligned-spin waveform model, finding that the primary mass lies in the mass gap with 90% credibility. | observing intermediate-mass black holes and the upper stellar-mass gap with ligo and virgo |
we discuss whether a multi-step electroweak phase transition (ewpt) occurs in two-higgs doublet models (2hdms). the ewpt is related to interesting phenomena such as baryogenesis and the ensuing gravitational wave. we examine parameter regions in cp-conserving 2hdms and find certain areas where multi-step ewpts occur. the parameter search shows the multi-step ewpt prefers the scalar potential with the approximate z2 symmetry and a mass hierarchy between the neutral cp-odd and cp-even extra scalar bosons ma < mh. by contrast, the multi-step ewpt whose first step is strongly first order favors a mass hierarchy ma > mh. in addition, we compute the higgs trilinear coupling in the parameter region where multi-step ewpts occur, which can be observed at future colliders. we also discuss a multi-peaked gravitational wave from a multi-step ewpt. subject index b53, b59 | possibility of a multi-step electroweak phase transition in the two-higgs doublet models |
classical soft graviton theorem gives the gravitational wave-form at future null infinity at late retarded time u for a general classical scattering. the large u expansion has three known universal terms: the constant term, the term proportional to 1/u and the term proportional to ln u/u2, whose coefficients are determined solely in terms of the momenta of incoming and the outgoing hard particles, including the momenta carried by outgoing gravitational and electromagnetic radiation produced during scattering. for the constant term, also known as the memory effect, the dependence on the momenta carried away by the final state radiation / massless particles is known as non-linear memory or null memory. it was shown earlier that for the coefficient of the 1/u term the dependence on the momenta of the final state massless particles / radiation cancels and the result can be written solely in terms of the momenta of the incoming particles / radiation and the final state massive particles. in this note we show that the same result holds for the coefficient of the ln u/u2 term. our result implies that for scattering of massless particles the coefficients of the 1/u and ln u/u2 terms are determined solely by the incoming momenta, even if the particles coalesce to form a black hole and massless radiation. we use our result to compute the low frequency flux of gravitational radiation from the collision of massless particles at large impact parameter. | classical soft graviton theorem rewritten |
we derive a gauge inspired combinatorial formula based on localization for the post-newtonian expansion of the gravitational wave form luminosity of binary systems made of objects with very different masses orbiting at large distances and small velocities. the results are tested against previous formulae in the literature for schwarschild and kerr black holes at the 5th and 3rd post newtonian order respectively beyond the quadrupole approximation. tidal effects show up in the wave form at the 5th pn order, providing a quantitative measure of the blackness/compactness properties of the heavy object. | post newtonian emission of gravitational waves from binary systems: a gauge theory perspective |
we explore color-kinematic duality for tree-level ads/cft correlators in momentum space. we start by studying the bi-adjoint scalar in ads at tree-level as an illustrative example. we follow this by investigating two forms of color-kinematic duality in yang-mills theory, the first for the integrated correlator in ads4 and the second for the integrand in general adsd+1. for the integrated correlator, we find color-kinematics does not yield additional relations among n-point, color-ordered correlators. to study color-kinematics for the adsd+1 yang-mills integrand, we use a spectral representation of the bulk-to-bulk propagator so that ads diagrams are similar in structure to their flat space counterparts. finally, we study color klt relations for the integrated correlator and double-copy relations for the ads integrand. we find that double-copy in ads naturally relates the bi-adjoint theory in adsd+3 to yang-mills in adsd+1. we also find a double-copy relation at three-points between yang-mills in adsd+1 and gravity in adsd−1 and comment on the higher-point generalization. by analytic continuation, these results on ads/cft correlators can be translated into statements about the wave function of the universe in de sitter. | on duality of color and kinematics in (a)ds momentum space |
primordial black holes may arise through ultra slow-roll inflation. in this work we study a toy model of ultra slow-roll inflation with a shallow dip. the ultra slow-roll stage enhances the curvature perturbations and thus the primordial scalar power spectrum. we analyze the features of the power spectrum numerically and analytically, and then give a rough estimate of the lower and upper bound of the enhancement. these large perturbations also produce second order gravitational waves, which are in the scope of future observations. | inflation with shallow dip and primordial black holes |
there is controversy surrounding the origin and evolution of our universe's largest supermassive black holes (smbhs). in this study, we consider the possibility that some of these black holes formed from the direct collapse of primordial density perturbations. since the mass of a primordial black hole is limited by the size of the cosmological horizon at the time of collapse, these smbhs must form rather late, and are naively in conflict with cmb spectral distortion constraints. such limits, however, can be avoided if the distribution of primordial curvature perturbations is highly non-gaussian. in this study, we present a model of multi-field inflation -- the curvaton model supplemented with self-interactions -- which can viably yield such dramatic non-gaussinities. furthermore, we calculate the maximal abundance of black holes that can be generated in this scenario and find this to be consistent with the observed population of high-redshift smbhs. this result is particularly timely in light of recent evidence from the nanograv experiment for a stochastic gravitational wave background consistent with smbh mergers. | supermassive primordial black holes from inflation |
ligo and virgo's third observing run revealed the first neutron star-black hole (nsbh) merger candidates in gravitational waves. these events are predicted to synthesize r-process elements1,2 creating optical/near-infrared `kilonova' emission. the joint gravitational wave and electromagnetic detection of an nsbh merger could be used to constrain the equation of state of dense nuclear matter3, and independently measure the local expansion rate of the universe4. here, we present the optical follow-up and analysis of two of the only three high-significance nsbh merger candidates detected to date, s200105ae and s200115j, with the zwicky transient facility5. the zwicky transient facility observed ~48% of s200105ae and ~22% of s200115j's localization probabilities, with observations sensitive to kilonovae brighter than -17.5 mag fading at 0.5 mag d-1 in the g- and r-bands; extensive searches and systematic follow-up of candidates did not yield a viable counterpart. we present state-of-the-art kilonova models tailored to nsbh systems that place constraints on the ejecta properties of these nsbh mergers. we show that with observed depths of apparent magnitude ~22 mag, attainable in metre-class, wide-field-of-view survey instruments, strong constraints on ejecta mass are possible, with the potential to rule out low mass ratios, high black hole spins and large neutron star radii. | optical follow-up of the neutron star-black hole mergers s200105ae and s200115j |
in the tropical stratosphere, deep layers of eastward and westward winds encircle the globe and descend regularly from the upper stratosphere to the tropical tropopause. with a complete cycle typically lasting almost 2.5 years, this quasi-biennial oscillation (qbo) is arguably the most predictable mode of atmospheric variability that is not linked to the changing seasons. the qbo affects climate phenomena outside the tropical stratosphere, including ozone transport, the north atlantic oscillation and the madden-julian oscillation, and its high predictability could enable better forecasts of these phenomena if models can accurately represent the coupling processes. climate and forecasting models are increasingly able to simulate stratospheric oscillations resembling the qbo, but exhibit common systematic errors such as weak amplitude in the lowermost tropical stratosphere. uncertainties about the waves that force the oscillation, particularly the momentum fluxes from small-scale gravity waves excited by deep convection, make its simulation challenging. improved representation of the processes governing the qbo is expected to lead to better forecasts of the oscillation and its impacts, increased understanding of unusual events such as the two qbo disruptions observed since 2016, and more reliable future projections of qbo behaviour under climate change. | impacts, processes and projections of the quasi-biennial oscillation |
the symmetry breaking of grand unified gauge groups in the early universe often leaves behind relic topological defects such as cosmic strings, domain walls, or monopoles. for some symmetry breaking chains, hybrid defects can form where cosmic strings attach to domain walls or monopoles attach to strings. in general, such hybrid defects are unstable, with one defect "eating" the other via the conversion of its rest mass into the other's kinetic energy and subsequently decaying via gravitational waves. in this work, we determine the gravitational wave spectrum from 1) the destruction of a cosmic string network by the nucleation of monopoles which cut up and "eat" the strings, 2) the collapse and decay of a monopole-string network by strings that "eat" the monopoles, 3) the destruction of a domain wall network by the nucleation of string-bounded holes on the wall that expand and "eat" the wall, and 4) the collapse and decay of a string-bounded wall network by walls that "eat" the strings. we call the gravitational wave signals produced from the "eating" of one topological defect by another gravitational wave gastronomy. we find that the four gravitational wave gastronomy signals considered yield unique spectra that can be used to narrow down the so(10) symmetry breaking chain to the standard model and the scales of symmetry breaking associated with the consumed topological defects. moreover, the systems we consider are unlikely to have a residual monopole or domain wall problem. | gravitational wave gastronomy |
we present pyseobnr, a python package for gravitational-wave (gw) modeling developed within the effective-one-body (eob) formalism. the package contains an extensive framework to generate state-of-the-art inspiral-merger-ringdown waveform models for compact-object binaries composed of black holes and neutron stars. we document and demonstrate how to use the built-in quasi-circular precessing-spin model seobnrv5phm, whose aligned-spin limit (seobnrv5hm) has been calibrated to numerical-relativity simulations and the nonspinning sector to gravitational self-force data using pyseobnr. furthermore, pyseobnr contains the infrastructure necessary to construct, calibrate, test, and profile new waveform models in the eob approach. the efficiency and flexibility of pyseobnr will be crucial to overcome the data-analysis challenges posed by upcoming and next-generation gw detectors on the ground and in space, which will afford the possibility to observe all compact-object binaries in our universe. | pyseobnr: a software package for the next generation of effective-one-body multipolar waveform models |
the symmetry breaking of grand unified gauge groups in the early universe often leaves behind relic topological defects such as cosmic strings, domain walls, or monopoles. for some symmetry breaking chains, hybrid defects can form where cosmic strings attach to domain walls or monopoles attach to strings. in general, such hybrid defects are unstable, with one defect "eating" the other via the conversion of its rest mass into the other's kinetic energy and, subsequently, decaying via gravitational waves. in this work, we determine the gravitational wave spectrum from 1) the destruction of a cosmic string network by the nucleation of monopoles which cut up and "eat" the strings, 2) the collapse and decay of a monopole-string network by strings that eat the monopoles, 3) the destruction of a domain wall network by the nucleation of string-bounded holes on the wall that expand and eat the wall, and 4) the collapse and decay of a string-bounded wall network by walls that eat the strings. we call the gravitational wave signals produced from the eating of one topological defect by another "gravitational wave gastronomy." we find that the four gravitational wave gastronomy signals considered yield unique spectra that can be used to narrow down the s o (10 ) symmetry breaking chain to the standard model and the scales of symmetry breaking associated with the consumed topological defects. moreover, the systems we consider are unlikely to have a residual monopole or domain wall problem. | guts, hybrid topological defects, and gravitational waves |
in this paper we have considered a quantized and linearly polarized gravitational wave interacting with a gravitational wave detector (interferometer detector) in the generalized uncertainty principle (gup) framework. following the analysis in phys. rev. lett. 127:081602 (2021), we consider a quantized gravitational wave interacting with a gravitational wave detector (ligo/virgo etc.) using a path integral approach. although the incoming gravitational wave was quantized, no planck-scale quantization effects were considered for the detector in earlier literatures. in our work, we consider a modified heisenberg uncertainty relation with a quadratic order correction in the momentum variable between the two phase space coordinates of the detector. using a path integral approach, we have obtained a stochastic equation involving the separation between two point-like objects. it is observed that random fluctuations (noises) and the correction terms due to the generalized uncertainty relation plays a crucial role in dictating such trajectories. finally, we observe that the solution to the stochastic equation leads to time dependent standard deviation due to the gup insertion, and for a primordial gravitational wave (where the initial state is a squeezed state) both the noise effect and the gup effects exponentially enhance which may be possible to detect in future generation of gravitational wave detectors. we have also given a plot of the dimensionless standard deviation with time depicting that the gup effect will carry a distinct signature which may be detectable in the future space based gravitational wave observatories. | minimal length scale correction in the noise of gravitons |
any violation of the fundamental principles of general relativity (gr), including the violations of the equivalence principle and parity/lorentz symmetries, could induce possible derivations in the gravitational wave (gw) propagations so they can be tested/constrained directly by the gw data. in this letter, we present a universal parametrization for characterizing possible derivations from gw propagations in gr. this parametrization provides a general framework for exploring possible modified gw propagations arising from a large number of modified theories of gravity. with this parameterization, we construct the modified gw waveforms generated by the coalescence of compact binaries with the effects of the gravitational parity/lorentz violations, then analyze the open data of compact binary merging events detected by ligo/virgo/kagra collaboration. we do not find any signatures of gravitational parity/lorentz violations, thereby allowing us to place several of the most stringent constraints on parity/lorentz violations in gravity and a first constraint on the lorentz-violating damping effect in gw. this also represents the most comprehensive tests on the modified gw propagations. | tests of modified gravitational wave propagations with gravitational waves |
in this paper, an innovative multitasking device (mtd) regulated by the gravity field realizing the functions of metamaterial absorber (mma) and linear polarization converter (lpc) is proposed and theoretically investigated. when the device operates in the function of mma, the engineered srr structure offers robust conditions for the formation of anapole mode. the anapole mode can lead to destructive interference in the far-field and constructive interference within the configuration synchronously; thereby, the incident wave energy can be consumed strongly. it is verified that the proposed mtd in the mma state can acquire a high absorption rate exceeding 0.9 from 10.82 to 13.55 ghz, with a broad relative bandwidth (rbw) of 22.4%. while in the lpc state, the utilization of the "l"-shaped structure successfully introduces an equivalent magnetic resonance to achieve the translation of the incident wave polarization state. in this case, the orthogonal state of the incident beam can be obtained by the mtd with the polarization conversion ratio (pcr) over 0.9 in the range of 2.62-3.72 ghz, whose rbw is 34.7%. the design accomplishes the functional combination of mma and lpc through the gravity field regulation, simultaneously staggering the operating bands to guarantee their independence and anti-interference. | multitasking device regulated by the gravity field: broadband anapole-excited absorber and linear polarization converter |
we derive the quadratic action for the physical degrees of freedom of massless spin-0, spin-1, and spin-2 perturbations on a schwarzschild-(a)ds background in arbitrary dimensions. we then use these results to compute the static response of asymptotically flat schwarzschild black holes to external fields. our analysis reproduces known facts about black hole love numbers — in particular that they vanish for all types of perturbation in four spacetime dimensions — but also leads to new results. for instance, we find that neutral schwarzschild black holes polarize in the presence of an electromagnetic background in any number of spacetime dimensions except four. moreover, we calculate for the first time black hole love numbers for vector-type gravitational perturbations in higher dimensions and find that they generically do not vanish. along the way, we shed some light on an apparent discrepancy between previous results in the literature, and clarify some aspects of the matching between perturbative calculations of static response on a schwarzschild background and the point-particle effective theory. | static response and love numbers of schwarzschild black holes |
fast radio bursts (frbs) are a newly discovered class of radio transients that emerge from cosmological sources and last for $\sim$ a few milliseconds. however, their origin remains a highly debated topic in astronomy. among the plethora of cataclysmic events proposed as potential progenitors, binary neutron star (bns) mergers have risen as compelling candidates for at least some subset of apparently non-repeating frbs. however, this connection should not be drawn solely on the basis of chance coincidence probability. in this study, we delineate necessary criteria that must be met when considering an association between frbs and bns mergers, focusing on the post-merger ejecta environment. to underscore the significance of these criteria, we scrutinize the proposed association between gw190425 and frb20190425a. our investigation meticulously accounts for the challenging condition that the frb signal must traverse the dense merger ejecta without significant attenuation to remain detectable at 400 mhz. furthermore, we find that if the frb is indeed linked to the gravitational wave event, the gw data strongly support a highly off-axis configuration, with a probability of the bns merger viewing angle $p(\theta_v$ $>$ 30$^{\circ}$) to be $\approx$ 99.99%. our findings therefore strongly exclude an on-axis system, which we find, on the other hand, to be required in order for this frb to be detectable. hence, we conclude that gw190425 is not related to frb20190425a. we also discuss implications of our results for future detections of coincident multi-messenger observations of frbs from bns remnants and gw events and argue that bns merger remnants cannot account for the formation of > 1% of frb sources. this observation suggests that short gamma-ray bursts should not be used to explain global attributes of the frb host population. | challenges for fast radio bursts as multi-messenger sources from binary neutron star mergers |
most gravitational wave (gw) events observed by the ligo and virgo detectors are consistent with mergers of binary black holes (bbhs) on quasi-circular orbits. however, some events are also consistent with non-zero orbital eccentricity, which can indicate that the binary formed via dynamical interactions. active gw search pipelines using quasi-circular waveform templates are inefficient for detecting eccentric mergers. also, analysing eccentric gw signals with waveform models neglecting eccentricity can lead to biases in the recovered parameters. we explore the detectability and characterisation of eccentric signals when searches and analyses rely on quasi-circular waveform models. we find that for a reference eccentric population, the fraction of events having fitting factor (ff) $< 0.95$ can be up to $\approx 2.2\%$ compared to $\approx 0.4\%$ for the baseline population. this leads to the loss in signal recovery fraction for up to $6\%$ for parameter space with non-negligible eccentricity ($e_{10} > 0.01$) and high mass ratio ($q > 3$). we perform parameter estimation (pe) for non-spinning and aligned-spin eccentric gw injections from bbhs with a total mass $m=35 m_\odot$, based on numerical relativity simulations and an eob based inspiral-merger-ringdown model (teobresums). we recover these injections using both quasi-circular and eccentric waveform models. for cases with $e_{20} \sim 0.1$, quasi-circular models fail to estimate chirp mass within the 90% credible interval accurately. further, for these low-mass injections, spin-induced precession does not mimic eccentricity. for injections of $e_{20}\sim 0.1$, pe conducted with an inspiral-only eccentric waveform model correctly characterises the injected signal to within 90% confidence, and recovers the injected eccentricities, suggesting that such models are sufficient for characterisation of low-mass eccentric bbh. (abridged) | blind spots and biases: the dangers of ignoring eccentricity in gravitational-wave signals from binary black holes |
the theory of superfluid dark matter is characterized by self-interacting sub-ev particles that thermalize and condense to form a superfluid core in galaxies. massive black holes at the center of galaxies, however, modify the dark matter distribution and result in a density enhancement in their vicinity known as dark matter spikes. the presence of these spikes affects the evolution of binary systems by modifying their gravitational wave emission and inducing dynamical friction effects on the orbiting bodies. in this work, we assess the role of dynamical friction for bodies moving through a superfluid core enhanced by a central massive black hole. as a first step, we compute the dynamical friction force experienced by bodies moving in a circular orbit. then, we estimate the gravitational wave dephasing of the binary, showing that the effect of the superfluid drag force is beyond the reach of space-based experiments like lisa, contrarily to collisionless dark matter, therefore providing an opportunity to distinguish these dark matter models. | dynamical friction in dark matter superfluids: the evolution of black hole binaries |
measurement of spin-precession in black hole binary mergers observed with gravitational waves is an exciting milestone as it relates to both general relativistic dynamics and astrophysical binary formation scenarios. in this study, we revisit the evidence for spin-precession in gw200129 and localize its origin to data in ligo livingston in the 20-50 hz frequency range where the signal amplitude is lower than expected from a nonprecessing binary given all the other data. these data are subject to known data quality issues as a glitch was subtracted from the detector's strain data. the lack of evidence for spin-precession in ligo hanford leads to a noticeable inconsistency between the inferred binary mass ratio and precessing spin in the two ligo detectors, something not expected from solely different gaussian noise realizations. we revisit the ligo livingston glitch mitigation and show that the difference between a spin-precessing and a nonprecessing interpretation for gw200129 is smaller than the statistical and systematic uncertainty of the glitch subtraction, finding that the support for spin-precession depends sensitively on the glitch modeling. we also investigate the signal-to-noise ratio ∼7 trigger in the less sensitive virgo detector. though not influencing the spin-precession studies, the virgo trigger is grossly inconsistent with the ones in ligo hanford and ligo livingston as it points to a much heavier system. we interpret the virgo data in the context of further data quality issues. while our results do not disprove the presence of spin-precession in gw200129, we argue that any such inference is contingent upon the statistical and systematic uncertainty of the glitch mitigation. our study highlights the role of data quality investigations when inferring subtle effects such as spin-precession for short signals such as the ones produced by high-mass systems. | curious case of gw200129: interplay between spin-precession inference and data-quality issues |
this paper explores the detection capability of space-borne detectors to the anisotropic stochastic gravitational-wave background (sgwb) without relying on the low-frequency approximation. to assess the detection performance, we calculate the power-law integrated sensitivity (plis) curve. our results demonstrate that a single detector has limited capabilities in detecting multipole moments beyond the monopole ($l=0$), quadrupole ($l=2$), and hexadecapole ($l=4$). however, when multiple detectors are combined, the presence of multiple pointing directions and the separation between detectors significantly enhance the detection capabilities for the other multipole moments. for instance, when considering the dipole ($l=1$), combining tianqin with tianqin ii and lisa with tianqin significantly improves the detection sensitivity by 2-3 orders of magnitude, compared with using a single tianqin and a single lisa, respectively. | sensitivity to anisotropic stochastic gravitational-wave background with space-borne networks |
the gravitational wave sky is starting to become very crowded, with the fourth science run (o4) at ligo expected to detect $\mathcal{o}(100)$ compact object coalescence signals. data analysis issues start to arise as we look further forwards, however. in particular, as the event rate increases in e.g. next generation detectors, it will become increasingly likely that signals arrive in the detector coincidentally, eventually becoming the dominant source class. it is known that current analysis pipelines will struggle to deal with this scenario, predominantly due to the scaling of traditional methods such as monte carlo markov chains and nested sampling, where the time difference between analysing a single signal and multiple can be as significant as days to months. in this work, we argue that sequential simulation-based inference methods can solve this problem by breaking the scaling behaviour. specifically, we apply an algorithm known as (truncated marginal) neural ratio estimation (tmnre), implemented in the code peregrine and based on swyft. to demonstrate its applicability, we consider three case studies comprising two overlapping, spinning, and precessing binary black hole systems with merger times separated by 0.05 s, 0.2 s, and 0.5 s. we show for the first time that we can recover, with full precision (as quantified by a comparison to the analysis of each signal independently), the posterior distributions of all 30 model parameters in a full joint analysis. crucially, we achieve this with only $\sim 15\%$ of the waveform evaluations that would be needed to analyse even a single signal with traditional methods. | what to do when things get crowded? scalable joint analysis of overlapping gravitational wave signals |
in this work we introduce phenomxo4a, the first phenomenological, frequency-domain gravitational waveform model to incorporate multipole asymmetries and precession angles tuned to numerical relativity. we build upon the modeling work that produced the phenompnr model and incorporate our additions into the imrphenomx framework, retuning the coprecessing frame model and extending the tuned precession angles to higher signal multipoles. we also include, for the first time in frequency-domain models, a recent model for spin-precession-induced multipolar asymmetry in the coprecessing frame to the dominant gravitational-wave multipoles. the accuracy of the full model and its constituent components is assessed through comparison to numerical relativity and numerical relativity surrogate waveforms by computing mismatches and performing parameter estimation studies. we show that, for the dominant signal multipole, we retain the modeling improvements seen in the phenompnr model. we find that the relative accuracy of current full imr models varies depending on location in parameter space and the comparison metric, and on average they are of comparable accuracy. however, we find that variations in the pointwise accuracy do not necessarily translate into large biases in the parameter estimation recoveries. | phenomxo4a: a phenomenological gravitational-wave model for precessing black-hole binaries with higher multipoles and asymmetries |
f(q) symmetric-teleparallel gravity is considered in view of quantum cosmology. specifically, we derive cosmological equations for f(q) models and then investigate the related energy conditions. in the minisuperspace formalism, the point-like f(q) hamiltonian is taken into account. in this framework, we obtain and solve the wheeler-de witt equation, thus finding the wave function of the universe in different cases. we show that the hartle criterion can be applied and classical observable universes occur. | minisuperspace quantum cosmology in f(q) gravity |
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