121 research outputs found
Computation of displacement and spin gravitational memory in numerical relativity
We present the first numerical relativity waveforms for binary black hole mergers produced using spectral methods that show both the displacement and the spin memory effects. Explicitly, we use the SXS (Simulating eXtreme Spacetimes) Collaboration’s SpEC code to run a Cauchy evolution of a binary black hole merger and then extract the gravitational wave strain using SpECTRE’s version of a Cauchy-characteristic extraction. We find that we can accurately resolve the strain’s traditional m=0 memory modes and some of the m≠0 oscillatory memory modes that have previously only been theorized. We also perform a separate calculation of the memory using equations for the Bondi-Metzner-Sachs charges as well as the energy and angular momentum fluxes at asymptotic infinity. Our new calculation uses only the gravitational wave strain and two of the Weyl scalars at infinity. Also, this computation shows that the memory modes can be understood as a combination of a memory signal throughout the binary’s inspiral and merger phases, and a quasinormal mode signal near the ringdown phase. Additionally, we find that the magnetic memory, up to numerical error, is indeed zero as previously conjectured. Last, we find that signal-to-noise ratios of memory for LIGO, the Einstein Telescope, and the Laser Interferometer Space Antenna with these new waveforms and new memory calculation are larger than previous expectations based on post-Newtonian or minimal waveform models
Computation of Displacement and Spin Gravitational Memory in Numerical Relativity
We present the first numerical relativity waveforms for binary black hole
mergers produced using spectral methods that show both the displacement and the
spin memory effects. Explicitly, we use the SXS Collaboration's
code to run a Cauchy evolution of a binary black hole merger and then extract
the gravitational wave strain using 's version of a
Cauchy-characteristic extraction. We find that we can accurately resolve the
strain's traditional memory modes and some of the oscillatory
memory modes that have previously only been theorized. We also perform a
separate calculation of the memory using equations for the Bondi-Metzner-Sachs
charges as well as the energy and angular momentum fluxes at asymptotic
infinity. Our new calculation uses only the gravitational wave strain and two
of the Weyl scalars at infinity. Also, this computation shows that the memory
modes can be understood as a combination of a memory signal throughout the
binary's inspiral and merger phases, and a quasinormal mode signal near the
ringdown phase. Additionally, we find that the magnetic memory, up to numerical
error, is indeed zero as previously conjectured. Lastly, we find that
signal-to-noise ratios of memory for LIGO, the Einstein Telescope (ET), and the
Laser Interferometer Space Antenna (LISA) with these new waveforms and new
memory calculation are larger than previous expectations based on
post-Newtonian or Minimal Waveform models.Comment: 20 pages, 11 figures; 10.1103/PhysRevD.102.104007. Corrected a minor
sign error in Eqs. 27, 40, 42, 43, and 5
Collective filters: a new approach to analyze the gravitational-wave ringdown of binary black-hole mergers
We propose two frequency-domain filters to analyze ringdown signals of binary
black hole mergers. The first rational filter is constructed based on a set of
(arbitrary) quasi-normal modes (QNMs) of the remnant black holes, whereas the
second full filter comes from the transmissivity of the remnant black holes.
The two filters can remove corresponding QNMs from original time-domain
ringdowns, while changing early inspiral signals in a trivial way - merely a
time and phase shift. After filtering out dominant QNMs, we can visualize the
existence of various subdominant effects. For example, by applying our filters
to a GW150914-like numerical relativity (NR) waveform, we find second-order
effects in the (l = 4, m = 4), (l = 5, m = 4) and (l = 5, m = 5) harmonics; the
spherical-spheroidal mixing mode in the (l = 2,m = 2) harmonic; and a mixing
mode in the (l = 2,m = 1) harmonic due to a gravitational recoil. In another NR
simulation where two component spins are anti-aligned with the orbital angular
momentum, we also find retrograde modes. Additionally, we propose to use the
rational filter to estimate the start time of a QNM. The filters are sensitive
to the remnant properties (i.e., mass and spin) and thus have a potential
application to future data analyses and parameter estimations. We also
investigate the stability of the full filter. Its connection to the instability
of QNM spectra is discussed
Numerical relativity surrogate model with memory effects and post-Newtonian hybridization
Numerical relativity simulations provide the most precise templates for the
gravitational waves produced by binary black hole mergers. However, many of
these simulations use an incomplete waveform extraction technique --
extrapolation -- that fails to capture important physics, such as gravitational
memory effects. Cauchy-characteristic evolution (CCE), by contrast, is a much
more physically accurate extraction procedure that fully evolves Einstein's
equations to future null infinity and accurately captures the expected physics.
In this work, we present a new surrogate model, NRHybSur3dq8CCE, built from
CCE waveforms that have been mapped to the post-Newtonian (PN) BMS frame and
then hybridized with PN and effective one-body (EOB) waveforms. This model is
trained on 102 waveforms with mass ratios and aligned spins
. The model spans the
entire LIGO-Virgo-KAGRA (LVK) frequency band (with
) for total masses and
includes the and spin-weight spherical
harmonic modes, but not the , or modes. We find that
NRHybSur3dq8CCE can accurately reproduce the training waveforms with
mismatches for total masses and can, for a modest degree of extrapolation, capably model
outside of its training region. Most importantly, unlike previous waveform
models, the new surrogate model successfully captures memory effects.Comment: 14 pages, 11 figures. Accepted for publication in PR
Comparing Remnant Properties from Horizon Data and Asymptotic Data in Numerical Relativity
We present a new study of remnant black hole properties from 13 binary black
hole systems, numerically evolved using the Spectral Einstein Code. The mass,
spin, and recoil velocity of each remnant were determined quasi-locally from
apparent horizon data and asymptotically from Bondi data computed at future null infinity using SpECTRE's Cauchy
characteristic evolution. We compare these independent measurements of the
remnant properties in the bulk and on the boundary of the spacetime, giving
insight into how well asymptotic data are able to reproduce local properties of
the remnant black hole in numerical relativity. We also discuss the theoretical
framework for connecting horizon quantities to asymptotic quantities and how it
relates to our results. This study recommends a simple improvement to the
recoil velocities reported in the Simulating eXtreme Spacetimes waveform
catalog, provides an improvement to future surrogate remnant models, and offers
new analysis techniques for evaluating the physical accuracy of numerical
simulations.Comment: 14 pages, 4 figures, 1 table; published Physical Review
The REFLECT Statement: Methods and Processes of Creating Reporting Guidelines for Randomized Controlled Trials for Livestock and Food Safety by Modifying the CONSORT Statement
The conduct of randomized controlled trials in livestock with production, health and food-safety outcomes presents unique challenges that may not be adequately reported in trial reports. The objective of this project was to modify the CONSORT (Consolidated Standards of Reporting Trials) statement to reflect the unique aspects of reporting these livestock trials. A 2-day consensus meeting was held on 18–19 November 2008 in Chicago, IL, USA, to achieve the objective. Prior to the meeting, a Web-based survey was conducted to identify issues for discussion. The 24 attendees were biostatisticians, epidemiologists, food-safety researchers, livestock-production specialists, journal editors, assistant editors and associate editors. Prior to the meeting, the attendees completed a Web-based survey indicating which CONSORT statement items may need to be modified to address unique issues for livestock trials. The consensus meeting resulted in the production of the REFLECT (Reporting Guidelines for Randomized Control Trials) statement for livestock and food safety and 22-item checklist. Fourteen items were modified from the CONSORT checklist and an additional sub-item was proposed to address challenge trials. The REFLECT statement proposes new terminology, more consistent with common usage in livestock production, to describe study subjects. Evidence was not always available to support modification to or inclusion of an item. The use of the REFLECT statement, which addresses issues unique to livestock trials, should improve the quality of reporting and design for trials reporting production, health and food-safety outcomes
Mutations in FGF17, IL17RD, DUSP6, SPRY4, and FLRT3 Are Identified in Individuals with Congenital Hypogonadotropic Hypogonadism
Congenital hypogonadotropic hypogonadism (CHH) and its anosmia-associated form (Kallmann syndrome [KS]) are genetically heterogeneous. Among the >15 genes implicated in these conditions, mutations in FGF8 and FGFR1 account for ∼12% of cases; notably, KAL1 and HS6ST1 are also involved in FGFR1 signaling and can be mutated in CHH. We therefore hypothesized that mutations in genes encoding a broader range of modulators of the FGFR1 pathway might contribute to the genetics of CHH as causal or modifier mutations. Thus, we aimed to (1) investigate whether CHH individuals harbor mutations in members of the so-called "FGF8 synexpression" group and (2) validate the ability of a bioinformatics algorithm on the basis of protein-protein interactome data (interactome-based affiliation scoring [IBAS]) to identify high-quality candidate genes. On the basis of sequence homology, expression, and structural and functional data, seven genes were selected and sequenced in 386 unrelated CHH individuals and 155 controls. Except for FGF18 and SPRY2, all other genes were found to be mutated in CHH individuals: FGF17 (n = 3 individuals), IL17RD (n = 8), DUSP6 (n = 5), SPRY4 (n = 14), and FLRT3 (n = 3). Independently, IBAS predicted FGF17 and IL17RD as the two top candidates in the entire proteome on the basis of a statistical test of their protein-protein interaction patterns to proteins known to be altered in CHH. Most of the FGF17 and IL17RD mutations altered protein function in vitro. IL17RD mutations were found only in KS individuals and were strongly linked to hearing loss (6/8 individuals). Mutations in genes encoding components of the FGF pathway are associated with complex modes of CHH inheritance and act primarily as contributors to an oligogenic genetic architecture underlying CHH
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