arXiv subjects

Matthew F. Carney

Publications and source records attributed to Matthew F. Carney.

7 recordsLinked to original sources

arXiv2026

No persuasive evidence yet of gravitational-wave tails from perturbers along the line of sight in LVK observations

Observations of compact binary coalescences (CBCs) by the LIGO-Virgo-KAGRA collaboration resulted in 90 events in the first three observing runs. We search the data near the loudest of these detections for so-called "gravitational glints," by performing Bayesian model comparison. Gravitational glints are gravitational-wave tails caused by interactions between a signal and a spacetime perturber and are theorized to present as echoes of the primary signal. We do not find convincing evidence of gravitational glints in binary black hole or intermediate-mass black hole binary events with a signal-to-noise ratio (SNR) of at least 12. We also found that standard matched-filter CBC searches with template banks that do not contain gravitational glints would likely not have missed signals containing a gravitational glint. We therefore estimate upper limits on the probability of a glint as a function of its relative amplitude and use these estimates to constrain the properties of perturbers in the Universe. With increased sensitivity in the fourth observing run, which will increase the number and SNR of detectable events, we remain optimistic that glints will soon be detectable.

gr-qc↗

arXiv2023

Constraining the quantum gravity polymer scale using LIGO data

We present the first empirical constraints on the polymer scale describing polymer quantized GWs propagating on a classical background. These constraints are determined from the polymer-induced deviation from the classically predicted propagation speed of GWs. We leverage posterior information on the propagation speed of GWs from two previously reported sources: 1) inter-detector arrival time delays for signals from the LIGO-Virgo Collaboration's first gravitational-wave transient catalog, GWTC1, and 2) from arrival time delays between GW signal GW170817 and its associated gamma-ray burst GRB170817A. For pure-GW constraints, we find relatively uninformative combined constraints of $ν= 0.96\substack{+0.15 \\ -0.21} \times 10^{-53} \, \rm{kg}^{1/2}$ and $μ= 0.94\substack{+0.75 \\ -0.20} \times 10^{-48} \, \rm{kg}^{1/2} \cdot s$ at the $90\%$ credible level for the two polymer quantization schemes, where $ν$ and $μ$ refer to polymer parameters associated to the polymer quantization schemes of propagating gravitational degrees of freedom. For constraints from GW170817/GRB170817A, we report much more stringent constraints of $ν_{\mathrm{low}} =2.66\substack{+0.60 \\ -0.10}\times 10^{-56}$, $ν_{\mathrm{high}} = 2.66\substack{+0.45 \\ -0.10}\times 10^{-56} $ and $μ_{\mathrm{low}} = 2.84\substack{+0.64 \\ -0.11}\times 10^{-52}$, $μ_{\mathrm{high}} = 2.76\substack{+0.46 \\ -0.11}\times 10^{-52}$ for both representations of polymer quantization and two choices of spin prior indicated by the subscript. Additionally, we explore the effect of varying the lag between emission of the GW and EM signals in the multimessenger case.

gr-qc↗

arXiv2022

What do gravitational wave detectors say about polymer quantum effects?

We compute the expected response of detector arms of gravitational wave observatories to polymerized gravitational waves. The mathematical and theoretical features of these waves were discussed in our previous work. In the present manuscript, we find both perturbative analytical, and full nonperturbative numerical solutions to the equations of motion of the detector arms using the method of geodesic deviations. These results show the modifications to both frequency and amplitude of the signal measured by the detector. Furthermore, we study the detectability of these signals in LISA by analyzing the modes in the frequency space.

gr-qc↗

arXiv2022

What is flat ΛCDM, and may we choose it?

The Universe is neither homogeneous nor isotropic, but it is close enough that we can reasonably approximate it as such on suitably large scales. The inflationary-$Λ$-Cold Dark Matter ($Λ$CDM) concordance cosmology builds on these assumptions to describe the origin and evolution of fluctuations. With standard assumptions about stress-energy sources, this system is specified by just seven phenomenological parameters, whose precise relations to underlying fundamental theories are complicated and may depend on details of those fields. Nevertheless, it is common practice to set the parameter that characterizes the spatial curvature, $Ω_K$, exactly to zero. This parameter-fixed $Λ$CDM is awarded distinguished status as separate model, "flat $Λ$CDM.'' Ipso facto this places the onus on proponents of "curved $Λ$CDM'' to present sufficient evidence that $Ω_K\neq0$, and is needed as a parameter. While certain inflationary model Lagrangians, with certain values of their parameters, and certain initial conditions, will lead to a present-day universe well-described as containing zero curvature, this does not justify distinguishing that subset of Lagrangians, parameters and initial conditions into a separate model. Absent any theoretical arguments, we cannot use observations that suggest small $Ω_K$ to enforce $Ω_K=0$. Our track record in picking inflationary models and their parameters a priori makes such a choice dubious, and concerns about tensions in cosmological parameters and large-angle cosmic-microwave-background anomalies strengthens arguments against this choice. We argue that $Ω_K$ must not be set to zero, and that $Λ$CDM remains a phenomenological model with at least 7 parameters.

astro-ph.CO↗

arXiv2021

Accurate relativistic observables from post-processing light cone catalogues

We introduce and study a new scheme to construct relativistic observables from post-processing light cone data. This construction is based on a novel approach, LC-Metric, which takes general light cone or snapshot output generated by arbitrary N-body simulations or emulations and solves the linearized Einstein equations to determine the spacetime metric on the light cone. We find that this scheme is able to determine the metric to high precision, and subsequently generate accurate mock cosmological observations sensitive to effects such as post-Born lensing and nonlinear ISW contributions. By comparing to conventional methods in quantifying those general relativistic effects, we show that this scheme is able to accurately construct the lensing convergence signal. We also find the accuracy of this method in quantifying the ISW effects in the highly nonlinear regime outperforms conventional methods by an order of magnitude. This scheme opens a new path for exploring and modeling higher-order and nonlinear general relativistic contributions to cosmological observables, including mock observations of gravitational lensing and the moving lens and Rees-Sciama effects.

astro-ph.CO↗

arXiv2021

On the question of measuring spatial curvature in an inhomogeneous universe

The curvature of a spacetime, either in a topological sense, or averaged over super-horizon-sized patches, is often equated with the global curvature term that appears in Friedmann's equation. In general, however, the Universe is inhomogeneous, and gravity is a nonlinear theory, thus any curvature perturbations violate the assumptions of the FLRW model; it is not necessarily true that local curvature, averaged over patches of constant-time surfaces, will reproduce the observational effects of global symmetry. Further, the curvature of a constant-time hypersurface is not an observable quantity, and can only be inferred indirectly. Here, we examine the behavior of curvature modes on hypersurfaces of an inhomogeneous spacetime non-perturbatively in a numerical relativistic setting, and how this curvature corresponds with that inferred by observers. We also note the point at which observations become sensitive to the impact of curvature sourced by inhomogeneities on inferred average properties, finding general agreement with past literature.

astro-ph.CO↗

arXiv2019

Comparing two models for measuring the neutron star equation of state from gravitational-wave signals

Observations of gravitational-wave signals from binary neutron-star mergers, like GW170817, can be used to constrain the neutron-star equation of state (EoS). One method involves modeling the EoS and measuring the model parameters through Bayesian inference. A previous study has demonstrated the effectiveness of using a phenomenologically parameterized piecewise polytrope to extract constraining information from a simulated population of binary neutron-star mergers. Despite its advantages compared to more traditional methods of measuring the tidal deformability of neutron stars, notable deficiencies arise when using this EoS model. In this work, we describe in detail the implementation of a model built from a spectral decomposition of the adiabatic index that was used by the LIGO-Virgo Collaboration in to constrain the neutron star EoS from GW170817. We demonstrate its overall consistency in recovering the neutron star EoS from a simulated signal to the piecewise polytropic implementation used in and explain any differences that arise. We find that both models recover consistent tidal information from the simulate signals with tightest constraints on the EoS around twice nuclear saturation density. As expected, the statistical error that arises in the piecewise polytropic representation near the fixed joining densities is greatly reduced by using the spectral model. In addition, we find that our choice of prior can have a dominant effect on EoS constraints

gr-qc↗