1,102 research outputs found
High-spin binary black hole mergers
We study identical mass black hole binaries with spins perpendicular to the
binary's orbital plane. These binaries have individual spins ranging from
to 0.90, ( in all cases) which is near the limit
possible with standard Bowen-York puncture initial data. The extreme cases
correspond to the largest initial spin simulations to date. Our results expand
the parameter space covered by Rezzolla {\it et al.} and, when combining both
data sets, we obtain estimations for the minimum and maximum values for the
intrinsic angular momenta of the remnant of binary black hole mergers of
and respectively. Note, however, that
these values are reached through extrapolation to the singular cases and thus remain as {\it estimates} until full-fledged numerical
simulations provide confirmation.Comment: 8 pages, 7 figures. Changed to match the version accepted for
publication in PR
Improving the NRTidal model for binary neutron star systems
Accurate and fast gravitational waveform (GW) models are essential to extract
information about the properties of compact binary systems that generate GWs.
Building on previous work, we present an extension of the NRTidal model for
binary neutron star (BNS) waveforms. The upgrades are: (i) a new closed-form
expression for the tidal contribution to the GW phase which includes further
analytical knowledge and is calibrated to more accurate numerical relativity
data than previously available; (ii) a tidal correction to the GW amplitude;
(iii) an extension of the spin-sector incorporating equation-of-state-dependent
finite size effects at quadrupolar and octupolar order; these appear in the
spin-spin tail terms and cubic-in-spin terms, both at 3.5PN. We add the new
description to the precessing binary black hole waveform model IMRPhenomPv2 to
obtain a frequency-domain precessing binary neutron star model. In addition, we
extend the SEOBNRv4_ROM and IMRPhenomD aligned-spin binary black hole waveform
models with the improved tidal phase corrections. Focusing on the new
IMRPhenomPv2_NRTidalv2 approximant, we test the model by comparing with
numerical relativity waveforms as well as hybrid waveforms combining tidal
effective-one-body and numerical relativity data. We also check consistency
against a tidal effective-one-body model across large regions of the BNS
parameter space.Comment: Accepted manuscrip
Binary Neutron Stars with Generic Spin, Eccentricity, Mass ratio, and Compactness - Quasi-equilibrium Sequences and First Evolutions
Information about the last stages of a binary neutron star inspiral and the
final merger can be extracted from quasi-equilibrium configurations and
dynamical evolutions. In this article, we construct quasi-equilibrium
configurations for different spins, eccentricities, mass ratios, compactnesses,
and equations of state. For this purpose we employ the SGRID code, which allows
us to construct such data in previously inaccessible regions of the parameter
space. In particular, we consider spinning neutron stars in isolation and in
binary systems; we incorporate new methods to produce highly eccentric and
eccentricity reduced data; we present the possibility of computing data for
significantly unequal-mass binaries; and we create equal-mass binaries with
individual compactness up to 0.23. As a proof of principle, we explore the
dynamical evolution of three new configurations. First, we simulate a
mass ratio which is the highest mass ratio for a binary neutron star evolved in
numerical relativity to date. We find that mass transfer from the companion
star sets in a few revolutions before merger and a rest mass of
is transferred between the two stars. This configuration
also ejects a large amount of material during merger, imparting a substantial
kick to the remnant. Second, we simulate the first merger of a precessing
binary neutron star. We present the dominant modes of the gravitational waves
for the precessing simulation, where a clear imprint of the precession is
visible in the (2,1) mode. Finally, we quantify the effect of an eccentricity
reduction procedure on the gravitational waveform. The procedure improves the
waveform quality and should be employed in future precision studies, but also
other errors, notably truncation errors, need to be reduced in order for the
improvement due to eccentricity reduction to be effective. [abridged]Comment: (37pages, 26 figures
Quasi-equilibrium binary black hole sequences for puncture data derived from helical Killing vector conditions
We construct a sequence of binary black hole puncture data derived under the
assumptions (i) that the ADM mass of each puncture as measured in the
asymptotically flat space at the puncture stays constant along the sequence,
and (ii) that the orbits along the sequence are quasi-circular in the sense
that several necessary conditions for the existence of a helical Killing vector
are satisfied. These conditions are equality of ADM and Komar mass at infinity
and equality of the ADM and a rescaled Komar mass at each puncture. In this
paper we explicitly give results for the case of an equal mass black hole
binary without spin, but our approach can also be applied in the general case.
We find that up to numerical accuracy the apparent horizon mass also remains
constant along the sequence and that the prediction for the innermost stable
circular orbit is similar to what has been found with the effective potential
method.Comment: 6 pages, 3 figures, 1 tabl
Strong decays of radially excited mesons in a chiral approach
We study radial excitations of pseudoscalar and vector (q bar q) mesons
within a chiral approach. We derive a general form for a chiral Lagrangian
describing processes involving excited pseudoscalar and vector mesons. The
parameters of the chiral Lagrangian are fitted using data and previous
calculations in the framework of the 3P0 model. Finite-width effects are
examined and predictions for mesons previously not discussed are given.
Available experimental data is analyzed whenever possible. Possible hints for
exotic mesons and open interpretation-issues are discussed.Comment: 16 page
Investigating GW190425 with numerical-relativity simulations
The third observing run of the LIGO-Virgo collaboration has resulted in abouthundred gravitational-wave triggers including the binary neutron star mergerGW190425. However, none of these events have been accompanied with anelectromagnetic transient found during extensive follow-up searches. In thisarticle, we perform new numerical-relativity simulations of binary neutron starand black hole - neutron star systems that have a chirp mass consistent withGW190425. Assuming that the GW190425's sky location was covered with sufficientaccuracy during the electromagnetic follow-up searches, we investigate whetherthe non-detection of the kilonova is compatible with the source parametersestimated through the gravitational-wave analysis and how one can use thisinformation to place constraints on the properties of the system. Oursimulations suggest that GW190425 is incompatible with an unequal mass binaryneutron star merger with a mass ratio $qmoderately stiff equations of state if the binary was face-on and covered bythe observation. Our analysis shows that a detailed observational result forkilonovae will be useful to constrain the mass ratio of binary neutron stars infuture events.<br
Radiation content of Conformally flat initial data
We study the radiation of energy and linear momentum emitted to infinity by
the headon collision of binary black holes, starting from rest at a finite
initial separation, in the extreme mass ratio limit. For these configurations
we identify the radiation produced by the initially conformally flat choice of
the three geometry. This identification suggests that the radiated energy and
momentum of headon collisions will not be dominated by the details of the
initial data for evolution of holes from initial proper separations
. For non-headon orbits, where the amount of radiation is orders of
magnitude larger, the conformally flat initial data may provide a relative even
better approximation.Comment: 4 pages, 4 figure
Can the post-Newtonian gravitational waveform of an inspiraling binary be improved by solving the energy balance equation numerically?
The detection of gravitational waves from inspiraling compact binaries using
matched filtering depends crucially on the availability of accurate template
waveforms. We determine whether the accuracy of the templates' phasing can be
improved by solving the post-Newtonian energy balance equation numerically,
rather than (as is normally done) analytically within the post-Newtonian
perturbative expansion. By specializing to the limit of a small mass ratio, we
find evidence that there is no gain in accuracy.Comment: 13 pages, RevTeX, 5 figures included via eps
A robust Pax7EGFP mouse that enables the visualization of dynamic behaviors of muscle stem cells.
BACKGROUND: Pax7 is a transcription factor involved in the specification and maintenance of muscle stem cells (MuSCs). Upon injury, MuSCs leave their quiescent state, downregulate Pax7 and differentiate, contributing to skeletal muscle regeneration. In the majority of regeneration studies, MuSCs are isolated by fluorescence-activated sorting (FACS), based on cell surface markers. It is known that MuSCs are a heterogeneous population and only a small percentage of isolated cells are true stem cells that are able to self-renew. A strong Pax7 reporter line would be valuable to study the in vivo behavior of Pax7-expressing stem cells.
METHODS: We generated and characterized the muscle properties of a new transgenic Pax7EGFP mouse. Utilizing traditional immunofluorescence assays, we analyzed whole embryos and muscle sections by fluorescence microscopy, in addition to whole skeletal muscles by 2-photon microscopy, to detect the specificity of EGFP expression. Skeletal muscles from Pax7EGFP mice were also evaluated in steady state and under injury conditions. Finally, MuSCs-derived from Pax7EGFP and control mice were sorted and analyzed by FACS and their myogenic activity was comparatively examined.
RESULTS: Our studies provide a new Pax7 reporter line with robust EGFP expression, detectable by both flow cytometry and fluorescence microscopy. Pax7EGFP-derived MuSCs have identical properties to that of wild-type MuSCs, both in vitro and in vivo, excluding any positional effect due to the transgene insertion. Furthermore, we demonstrated high specificity of EGFP to label MuSCs in a temporal manner that recapitulates the reported Pax7 expression pattern. Interestingly, immunofluorescence analysis showed that the robust expression of EGFP marks cells in the satellite cell position of adult muscles in fixed and live tissues.
CONCLUSIONS: This mouse could be an invaluable tool for the study of a variety of questions related to MuSC biology, including but not limited to population heterogeneity, polarity, aging, regeneration, and motility, either by itself or in combination with mice harboring additional genetic alterations
Risk Theory with Affine Dividend Payment Strategies
We consider a classical compound Poisson risk model with affine dividend payments. We illustrate how both by analytical and probabilistic techniques closed-form expressions for the expected discounted dividends until ruin and the Laplace transform of the time to ruin can be derived for exponentially distributed claim amounts. Moreover, numerical examples are given which compare the performance of the proposed strategy to classical barrier strategies and illustrate that such affine strategies can be a noteworthy compromise between profitability and safety in collective risk theory
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