6,066 research outputs found
Astrophage of neutron stars from supersymmetric dark matter Q-balls
The gauge-mediated model of supersymmetry breaking implies that stable
non-topological solitons, Q-balls, could form in the early universe and
comprise the dark matter. It is shown that the inclusion of the effects from
gravity-mediation set an upper limit on the size of Q-balls. When in a dense
baryonic environment Q-balls grow until reaching this limiting size at which
point they fragment into two equal-sized Q-balls. This Q-splitting process will
rapidly destroy a neutron star that absorbs even one Q-ball. The new limits on
Q-ball dark matter require an ultralight gravitino m_3/2 < keV, naturally
avoiding the gravitino overclosure problem, and providing the MSSM with a dark
matter candidate where gravitino dark matter is not viable.Comment: 4 pages, 1 figure, Published in Phys. Rev. D. Rapid Communication
Probing the Binary Black Hole Merger Regime with Scalar Perturbations
We present results obtained by scattering a scalar field off the curved
background of a coalescing binary black hole system. A massless scalar field is
evolved on a set of fixed backgrounds, each provided by a spatial hypersurface
generated numerically during a binary black hole merger. We show that the
scalar field scattered from the merger region exhibits quasinormal ringing once
a common apparent horizon surrounds the two black holes. This occurs earlier
than the onset of the perturbative regime as measured by the start of the
quasinormal ringing in the gravitational waveforms. We also use the scalar
quasinormal frequencies to associate a mass and a spin with each hypersurface,
and observe the compatibility of this measure with the horizon mass and spin
computed from the dynamical horizon framework.Comment: 10 Pages and 6 figure
Precession during merger 1: Strong polarization changes are observationally accessible features of strong-field gravity during binary black hole merger
The short gravitational wave signal from the merger of compact binaries
encodes a surprising amount of information about the strong-field dynamics of
merger into frequencies accessible to ground-based interferometers. In this
paper we describe a previously-unknown "precession" of the peak emission
direction with time, both before and after the merger, about the total angular
momentum direction. We demonstrate the gravitational wave polarization encodes
the orientation of this direction to the line of sight. We argue the effects of
polarization can be estimated nonparametrically, directly from the
gravitational wave signal as seen along one line of sight, as a slowly-varying
feature on top of a rapidly-varying carrier. After merger, our results can be
interpreted as a coherent excitation of quasinormal modes of different angular
orders, a superposition which naturally "precesses" and modulates the
line-of-sight amplitude. Recent analytic calculations have arrived at a similar
geometric interpretation. We suspect the line-of-sight polarization content
will be a convenient observable with which to define new high-precision tests
of general relativity using gravitational waves. Additionally, as the nonlinear
merger process seeds the initial coherent perturbation, we speculate the
amplitude of this effect provides a new probe of the strong-field dynamics
during merger. To demonstrate the ubiquity of the effects we describe, we
summarize the post-merger evolution of 104 generic precessing binary mergers.
Finally, we provide estimates for the detectable impacts of precession on the
waveforms from high-mass sources. These expressions may identify new precessing
binary parameters whose waveforms are dissimilar from the existing sample.Comment: 11 figures; v2 includes response to referee suggestion
Intrinsic selection biases of ground-based gravitational wave searches for high-mass BH-BH mergers
The next generation of ground-based gravitational wave detectors may detect a
few mergers of comparable-mass M\simeq 100-1000 Msun ("intermediate-mass'', or
IMBH) spinning black holes. Black hole spin is known to have a significant
impact on the orbit, merger signal, and post-merger ringdown of any binary with
non-negligible spin. In particular, the detection volume for spinning binaries
depends significantly on the component black hole spins. We provide a fit to
the single-detector and isotropic-network detection volume versus (total) mass
and arbitrary spin for equal-mass binaries. Our analysis assumes matched
filtering to all significant available waveform power (up to l=6 available for
fitting, but only l<= 4 significant) estimated by an array of 64 numerical
simulations with component spins as large as S_{1,2}/M^2 <= 0.8. We provide a
spin-dependent estimate of our uncertainty, up to S_{1,2}/M^2 <= 1. For the
initial (advanced) LIGO detector, our fits are reliable for
(). In the online version of this
article, we also provide fits assuming incomplete information, such as the
neglect of higher-order harmonics. We briefly discuss how a strong selection
bias towards aligned spins influences the interpretation of future
gravitational wave detections of IMBH-IMBH mergers.Comment: 18 pages, 15 figures, accepted by PRD. v2 is version accepted for
publication, including minor changes in response to referee feedback and
updated citation
Queering Secondary Education: An Inquiry to the Necessity of Queer Studies for All Students
In the current state of secondary education, queer studies are appallingly underexposed. The subject matter is often completely disregarded due to a perceived discomfort around themes and content regarding LGBTQ+ sexualities. This process of elimination is a disservice to all students as they continue their education and move on to the adult world. Queer studies must be included for all students to ensure a society of empathy and understanding. Including the queer identity in the secondary education, classroom gives LGBTQ+ students the usable past that is essential to their wellbeing and mental health, and it provides exposure and understanding for students who fall outside the queer umbrella. This process is not one of addition or elimination, but rather, it is striving to acknowledge the information already present in most curriculums. An educator must create a culturally inclusive classroom that reflects the world in which their students live. Diversity is not simply a matter of race or religion. It is acknowledging and engaging in all aspects of intersectionality within a text, community, and the world
Spray Ejected from the Lunar Surface by Meteoroid Impact
Fragments ejected from lunar surface by meteoroid impact analyzed on basis of studies of hypervelocity impact in rock and san
Comment on `Formation of a Dodecagonal Quasicrystalline Phase in a Simple Monatomic Liquid'
In a recent paper M. Dzugutov, Phys. Rev. Lett. 70 2924 (1993), describes a
molecular dynamics cooling simulation where he obtained a large monatomic
dodecagonal quasicrystal from a melt. The structure was stabilized by a special
potential [Phys. Rev. A46 R2984 (1992)] designed to prevent the nucleation of
simple dense crystal structures. In this comment we will give evidence that the
ground state structure for Dzugutov's potential is an ordinary bcc crystal
Mapping the magic numbers in binary Lennard-Jones clusters
Using a global optimization approach that directly searches for the
composition of greatest stability, we have been able to find the particularly
stable structures for binary Lennard-Jones clusters with up to 100 atoms for a
range of Lennard-Jones parameters. In particular, we have shown that just
having atoms of different size leads to a remarkable stabilization of
polytetrahedral structures, including both polyicosahedral clusters and at
larger sizes structures with disclination lines.Comment: 5 pages, 5 figure
One-step Metabolomics: Carbohydrates, Organic and Amino Acids Quantified in a Single Procedure
Every infant born in the US is now screened for up to 42 rare genetic disorders called "inborn errors of metabolism". The screening method is based on tandem mass spectrometry and quantifies acylcarnitines as a screen for organic acidemias and also measures amino acids. All states also perform enzymatic testing for carbohydrate disorders such as galactosemia. Because the results can be non-specific, follow-up testing of positive results is required using a more definitive method. The present report describes the "urease" method of sample preparation for inborn error screening. Crystalline urease enzyme is used to remove urea from body fluids which permits most other water-soluble metabolites to be dehydrated and derivatized for gas chromatography in a single procedure. Dehydration by evaporation in a nitrogen stream is facilitated by adding acetonitrile and methylene chloride. Then, trimethylsilylation takes place in the presence of a unique catalyst, triethylammonium trifluoroacetate. Automated injection and chromatography is followed by macro-driven custom quantification of 192 metabolites and semi-quantification of every major component using specialized libraries of mass spectra of TMS derivatized biological compounds. The analysis may be performed on the widely-used Chemstation platform using the macros and libraries available from the author. In our laboratory, over 16,000 patient samples have been analyzed using the method with a diagnostic yield of about 17%--that is, 17% of the samples results reveal findings that should be acted upon by the ordering physician. Included in these are over 180 confirmed inborn errors, of which about 38% could not have been diagnosed using previous methods
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