Comparisons of binary black hole merger waveforms

This a particularly exciting time for gravitational wave physics. Ground-based gravitational wave detectors are now operating at a sensitivity such that gravitational radiation may soon be directly detected, and recently several groups have independently made significant breakthroughs that have finally enabled numerical relativists to solve the Einstein field equations for coalescing black-hole binaries, a key source of gravitational radiation. The numerical relativity community is now in the position to begin providing simulated merger waveforms for use by the data analysis community, and it is therefore very important that we provide ways to validate the results produced by various numerical approaches. Here, we present a simple comparison of the waveforms produced by two very different, but equally successful approaches--the generalized harmonic gauge and the moving puncture methods. We compare waveforms of equal-mass black hole mergers with minimal or vanishing spins. The results show exceptional agreement for the final burst of radiation, with some differences attributable to small spins on the black holes in one case.Comment: Revtex 4, 5 pages. Published versio

Next generation ice core technology reveals true minimum natural levels of lead (Pb) in the atmosphere: insights from the Black Death

Current policies to reduce lead pollution in the air are based on the assumption that pre-industrial levels of lead in the air were negligible, safe or non-existent. This trans-disciplinary article shows that this is not the case, using ‘next-generation’ laser technology in climate science, in combination with detailed historical and archaeological records in as many as 7 languages, from all over Europe. We show that lead levels in the air have been elevated for the past 2000 years, except for a single 4-year period. This 4-year period corresponds with the largest known pandemic ever to ravage western Europe (the Black Death), resulting in a 40-50% reduction in population. This unprecedented historic population collapse was accompanied by dramatic economic collapse that halted lead mining and smelting, and related emissions in the air. This trans-disciplinary study is a collaboration led by Harvard University and the Climate Change Institute at the University of Maine, and researchers from the University of Heidelberg (Germany) and the University of Nottingham (UK). It uses next-generation technology and expertise in history, climate science, archaeology and toxicology, brought to bear in a highly detailed contribution to planetary health, with crucial implications for public health and environmental policy, and the history of human exposure to lead

Aperture synthesis for gravitational-wave data analysis: Deterministic Sources

Gravitational wave detectors now under construction are sensitive to the phase of the incident gravitational waves. Correspondingly, the signals from the different detectors can be combined, in the analysis, to simulate a single detector of greater amplitude and directional sensitivity: in short, aperture synthesis. Here we consider the problem of aperture synthesis in the special case of a search for a source whose waveform is known in detail: \textit{e.g.,} compact binary inspiral. We derive the likelihood function for joint output of several detectors as a function of the parameters that describe the signal and find the optimal matched filter for the detection of the known signal. Our results allow for the presence of noise that is correlated between the several detectors. While their derivation is specialized to the case of Gaussian noise we show that the results obtained are, in fact, appropriate in a well-defined, information-theoretic sense even when the noise is non-Gaussian in character. The analysis described here stands in distinction to ``coincidence analyses'', wherein the data from each of several detectors is studied in isolation to produce a list of candidate events, which are then compared to search for coincidences that might indicate common origin in a gravitational wave signal. We compare these two analyses --- optimal filtering and coincidence --- in a series of numerical examples, showing that the optimal filtering analysis always yields a greater detection efficiency for given false alarm rate, even when the detector noise is strongly non-Gaussian.Comment: 39 pages, 4 figures, submitted to Phys. Rev.

Protein structures and optimal folding emerging from a geometrical variational principle

Novel numerical techniques, validated by an analysis of barnase and chymotrypsin inhibitor, are used to elucidate the paramount role played by the geometry of the protein backbone in steering the folding to the correct native state. It is found that, irrespective of the sequence, the native state of a protein has exceedingly large number of conformations with a given amount of structural overlap compared to other compact artificial backbones; moreover the conformational entropies of unrelated proteins of the same length are nearly equal at any given stage of folding. These results are suggestive of an extremality principle underlying protein evolution, which, in turn, is shown to be associated with the emergence of secondary structures.Comment: Revtex, 5 pages, 5 postscript figure

Lack of Assortative Mating for Tail, Body Size, or Condition in the Elaborate Monomorphic Turquoise-Browed Motmot (\u3cem\u3eEumomota superciliosa\u3c/em\u3e)

Elaborate male and female plumage can be maintained by mutual sexual selection and function as a mate-choice or status signal in both sexes. Both male and female Turquoise-browed Motmot (Eumomota superciliosa) have long tails that terminate in widened blue-and-black rackets that appear to hang, unattached, below the body of the bird. I tested whether mutual sexual selection maintains the Turquoise-browed Motmot’s elaborate tail plumage by testing the prediction that mating occurs in an assortative manner for tail plumage. I also tested whether assortative mating occurs for body size, a potential measure of dominance, and for phenotypic condition, a measure of individual quality. Assortative mating was measured (1) within all pairs in the study population, (2) within newly formed pairs, and (3) within experimentally induced pairs that formed after removal of females from stable pairs. Assortative mating was not found for tail plumage, body size, or phenotypic condition in any of these samples. Therefore, there was no support for the “mutual sexual selection” hypothesis. I discuss the hypothesis that the tail is sexually selected in males only, and that natural selection accounts for the evolutionary maintenance of the elaborate female tail. La existencia de plumaje elaborado en los machos y las hembras puede ser mantenida por selecci´on sexual mutua, y funcionar como una se˜nal para la selecci´on de parejas o del estatus de los individuos en ambos sexos. Tanto los machos como las hembras de la especie Eumomota superciliosa tienen colas largas que terminan en unas raquetas ensanchadas de color azul y negro, que parecen colgar debajo del cuerpo de las aves. En este estudio prob´e si el plumaje elaborado de la cola de esta especie es mantenido mediante selecci´on sexual mutua, evaluando la predicci´on de que el apareamiento es asociativo con respecto al plumaje de la cola. Tambi´en prob´e si existe apareamiento asociativo con respecto al tama˜no (una medida potencial de la dominancia) y con respecto a la condici´on fenot´ıpica (una medida de la calidad de los individuos). El apareamiento asociativo fue medido para todas las parejas de la poblaci´on de estudio, para parejas formadas recientemente y para parejas cuya formaci´on fue inducida experimentalmente mediante la remoci´on de las hembras de parejas estables. No se encontr´o apareamiento asociativo con respecto al plumaje de la cola, al tama˜no corporal, ni a la condici´on fenot´ıpica en ninguna de estas muestras. Por lo tanto, no existi´o respaldo para la hip´otesis de selecci´on sexual mutua. Discuto la hip´otesis que plantea que la cola es objeto de selecci´on sexual s´olo en los machos, y que la selecci´on natural permite explicar el mantenimiento evolutivo de la cola elaborada en las hembras

Constraints on Cosmic Strings from the LIGO-Virgo Gravitational-Wave Detectors

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10−8 in some regions of the cosmic string parameter space

First all-sky search for continuous gravitational waves from unknown sources in binary systems

We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to ∼2; 254 h and a frequency- and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from ∼0.6 × 10−3 ls to ∼6; 500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3 × 10−24 at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz

Search for long-lived gravitational-wave transients coincident with long gamma-ray bursts

Long gamma-ray bursts (GRBs) have been linked to extreme core-collapse supernovae from massive stars. Gravitational waves (GW) offer a probe of the physics behind long GRBs. We investigate models of long-lived (~10–1000 s) GW emission associated with the accretion disk of a collapsed star or with its protoneutron star remnant. Using data from LIGO’s fifth science run, and GRB triggers from the Swift experiment, we perform a search for unmodeled long-lived GW transients. Finding no evidence of GW emission, we place 90% confidence-level upper limits on the GW fluence at Earth from long GRBs for three waveforms inspired by a model of GWs from accretion disk instabilities. These limits range from FtoFcm-2, depending on the GRB and on the model, allowing us to probe optimistic scenarios of GW production out to distances as far as = 33 Mpc. Advanced detectors are expected to achieve strain sensitivities 10x better than initial LIGO, potentially allowing us to probe the engines of the nearest long GRBs

Directed search for continuous gravitational waves from the Galactic center

We present the results of a directed search for continuous gravitational waves from unknown, isolated neutron stars in the Galactic center region, performed on two years of data from LIGO’s fifth science run from two LIGO detectors. The search uses a semicoherent approach, analyzing coherently 630 segments, each spanning 11.5 hours, and then incoherently combining the results of the single segments. It covers gravitational wave frequencies in a range from 78 to 496 Hz and a frequency-dependent range of first-order spindown values down to −7.86×10−8  Hz/s at the highest frequency. No gravitational waves were detected. The 90% confidence upper limits on the gravitational wave amplitude of sources at the Galactic center are ∼3.35×10−25 for frequencies near 150 Hz. These upper limits are the most constraining to date for a large-parameter-space search for continuous gravitational wave signals

Modifications of the BTZ black hole by a dilaton/scalar

We investigate some modifications of the static BTZ black hole solution due to a chosen asymptotically constant dilaton/scalar. New classes of static black hole solutions are obtained. One of the solutions contains the Martinez-Zanelli conformal black hole solution as a special case. Using quasilocal formalism, we calculate their mass for a finite spatial region that contains the black hole. Their temperatures are also computed. Finally, using some of the curvature singularities as examples, we investigate whether a quantum particle behaves singularly or not.Comment: 18 pages, Latex, in press in Phys. Rev.