2,920 research outputs found
Visualizing genetic constraints
Principal Components Analysis (PCA) is a common way to study the sources of
variation in a high-dimensional data set. Typically, the leading principal
components are used to understand the variation in the data or to reduce the
dimension of the data for subsequent analysis. The remaining principal
components are ignored since they explain little of the variation in the data.
However, evolutionary biologists gain important insights from these low
variation directions. Specifically, they are interested in directions of low
genetic variability that are biologically interpretable. These directions are
called genetic constraints and indicate directions in which a trait cannot
evolve through selection. Here, we propose studying the subspace spanned by low
variance principal components by determining vectors in this subspace that are
simplest. Our method and accompanying graphical displays enhance the
biologist's ability to visualize the subspace and identify interpretable
directions of low genetic variability that align with simple directions.Comment: Published in at http://dx.doi.org/10.1214/12-AOAS603 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Planet Hunters X: Searching for Nearby Neighbors of 75 Planet and Eclipsing Binary Candidates from the K2 Kepler Extended Mission
We present high-resolution observations of a sample of 75 K2 targets from
Campaigns 1-3 using speckle interferometry on the Southern Astrophysical
Research (SOAR) telescope and adaptive optics (AO) imaging at the Keck II
telescope. The median SOAR -band and Keck -band detection limits at 1"
were ~mag and ~mag, respectively. This
sample includes 37 stars likely to host planets, 32 targets likely to be
eclipsing binaries (EBs), and 6 other targets previously labeled as likely
planetary false positives. We find nine likely physically bound companion stars
within 3" of three candidate transiting exoplanet host stars and six likely
EBs. Six of the nine detected companions are new discoveries; one of the six,
EPIC 206061524, is associated with a planet candidate. Among the EB candidates,
companions were only found near the shortest period ones ( days), which is
in line with previous results showing high multiplicity near short-period
binary stars. This high-resolution data, including both the detected companions
and the limits on potential unseen companions, will be useful in future planet
vetting and stellar multiplicity rate studies for planets and binaries.Comment: Accepted in A
Critical temperature for kaon condensation in color-flavor locked quark matter
We study the behavior of Goldstone bosons in color-flavor-locked (CFL) quark
matter at nonzero temperature. Chiral symmetry breaking in this phase of cold
and dense matter gives rise to pseudo-Goldstone bosons, the lightest of these
being the charged and neutral kaons K^+ and K^0. At zero temperature,
Bose-Einstein condensation of the kaons occurs. Since all fermions are gapped,
this kaon condensed CFL phase can, for energies below the fermionic energy gap,
be described by an effective theory for the bosonic modes. We use this
effective theory to investigate the melting of the condensate: we determine the
temperature-dependent kaon masses self-consistently using the two-particle
irreducible effective action, and we compute the transition temperature for
Bose-Einstein condensation. Our results are important for studies of transport
properties of the kaon condensed CFL phase, such as bulk viscosity.Comment: 24 pages, 8 figures, v2: new section about effect of electric
neutrality on critical temperature added; references added; version to appear
in J.Phys.
Planet Hunters. VIII. Characterization of 41 Long-Period Exoplanet Candidates from Kepler Archival Data
The census of exoplanets is incomplete for orbital distances larger than 1
AU. Here, we present 41 long-period planet candidates in 38 systems identified
by Planet Hunters based on Kepler archival data (Q0-Q17). Among them, 17
exhibit only one transit, 14 have two visible transits and 10 have more than
three visible transits. For planet candidates with only one visible transit, we
estimate their orbital periods based on transit duration and host star
properties. The majority of the planet candidates in this work (75%) have
orbital periods that correspond to distances of 1-3 AU from their host stars.
We conduct follow-up imaging and spectroscopic observations to validate and
characterize planet host stars. In total, we obtain adaptive optics images for
33 stars to search for possible blending sources. Six stars have stellar
companions within 4". We obtain high-resolution spectra for 6 stars to
determine their physical properties. Stellar properties for other stars are
obtained from the NASA Exoplanet Archive and the Kepler Stellar Catalog by
Huber et al. (2014). We validate 7 planet candidates that have planet
confidence over 0.997 (3-{\sigma} level). These validated planets include 3
single-transit planets (KIC-3558849b, KIC-5951458b, and KIC-8540376c), 3
planets with double transits (KIC-8540376b, KIC-9663113b, and KIC-10525077b),
and 1 planet with 4 transits (KIC-5437945b). This work provides assessment
regarding the existence of planets at wide separations and the associated false
positive rate for transiting observation (17%-33%). More than half of the
long-period planets with at least three transits in this paper exhibit transit
timing variations up to 41 hours, which suggest additional components that
dynamically interact with the transiting planet candidates. The nature of these
components can be determined by follow-up radial velocity and transit
observations.Comment: Published on ApJ, 815, 127 Notations of validated planets are changed
in accordance with naming convention of NASA Exoplanet Archiv
Planet Hunters VII. Discovery of a New Low-Mass, Low-Density Planet (PH3 c) Orbiting Kepler-289 with Mass Measurements of Two Additional Planets (PH3 b and d)
We report the discovery of one newly confirmed planet ( days,
) and mass determinations of two previously
validated Kepler planets, Kepler-289 b ( days,
) and Kepler-289-c ( days,
), through their transit timing variations
(TTVs). We also exclude the possibility that these three planets reside in a
Laplace resonance. The outer planet has very deep (), high
signal-to-noise transits, which puts extremely tight constraints on its host
star's stellar properties via Kepler's Third Law. The star PH3 is a young
( Gyr as determined by isochrones and gyrochronology), Sun-like star
with , , and
K. The middle planet's large TTV amplitude (
hours) resulted either in non-detections or inaccurate detections in previous
searches. A strong chopping signal, a shorter period sinusoid in the TTVs,
allows us to break the mass-eccentricity degeneracy and uniquely determine the
masses of the inner, middle, and outer planets to be ,
, and , which we designate PH3 b, c, and
d, respectively. Furthermore, the middle planet, PH3 c, has a relatively low
density, g/cm for a planet of its mass, requiring a
substantial H/He atmosphere of by mass, and joins a
growing population of low-mass, low-density planets.Comment: 21 pages, 10 figures, 5 tables, accepted into Ap
Bulk viscosity in 2SC quark matter
The bulk viscosity of three-flavor color-superconducting quark matter
originating from the nonleptonic process u+s u+d is computed. It is assumed
that up and down quarks form Cooper pairs while the strange quark remains
unpaired (2SC phase). A general derivation of the rate of strangeness
production is presented, involving contributions from a multitude of different
subprocesses, including subprocesses that involve different numbers of gapped
quarks as well as creation and annihilation of particles in the condensate. The
rate is then used to compute the bulk viscosity as a function of the
temperature, for an external oscillation frequency typical of a compact star
r-mode. We find that, for temperatures far below the critical temperature T_c
for 2SC pairing, the bulk viscosity of color-superconducting quark matter is
suppressed relative to that of unpaired quark matter, but for T >~ 10^(-3) T_c
the color-superconducting quark matter has a higher bulk viscosity. This is
potentially relevant for the suppression of r-mode instabilities early in the
life of a compact star.Comment: 18 pages + appendices (28 pages total), 8 figures; v3: corrected
numerical error in the plots; 2SC bulk viscosity is now larger than unpaired
bulk viscosity in a wider temperature rang
When who and how matter: explaining the success of referendums in Europe
This article aims to identify the institutional factors that make a referendum successful. This comparative analysis seeks to explain the success of top-down referendums organized in Europe between 2001 and 2013. It argues and tests for the main effect of three institutional factors (popularity of the initiator, size of parliamentary majority, and political cues during referendum campaigns) and controls for the type of referendum and voter turnout. The analysis uses data collected from referendums and electoral databases, public opinion surveys, and newspaper articles. Results show that referendums proposed by a large parliamentary majority or with clear messages from political parties during campaign are likely to be successful
Evidence for dark energy from the cosmic microwave background alone using the Atacama Cosmology Telescope lensing measurements
For the first time, measurements of the cosmic microwave background radiation
(CMB) alone favor cosmologies with dark energy over models without dark
energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing
deflection power spectrum from the Atacama Cosmology Telescope with temperature
and polarization power spectra from the Wilkinson Microwave Anisotropy Probe.
The lensing data break the geometric degeneracy of different cosmological
models with similar CMB temperature power spectra. Our CMB-only measurement of
the dark energy density confirms other measurements from
supernovae, galaxy clusters and baryon acoustic oscillations, and demonstrates
the power of CMB lensing as a new cosmological tool.Comment: 4 pages, 3 figures; replaced with version accepted by Physical Review
Letters, added sentence on models with non-standard primordial power spectr
The Atacama Cosmology Telescope: Sunyaev-Zel'dovich Selected Galaxy Clusters at 148 GHz from Three Seasons of Data
[Abridged] We present a catalog of 68 galaxy clusters, of which 19 are new
discoveries, detected via the Sunyaev-Zel'dovich effect (SZ) at 148 GHz in the
Atacama Cosmology Telescope (ACT) survey of 504 square degrees on the celestial
equator. A subsample of 48 clusters within the 270 square degree region
overlapping SDSS Stripe 82 is estimated to be 90% complete for M_500c > 4.5e14
Msun and 0.15 < z < 0.8. While matched filters are used to detect the clusters,
the sample is studied further through a "Profile Based Amplitude Analysis"
using a single filter at a fixed \theta_500 = 5.9' angular scale. This new
approach takes advantage of the "Universal Pressure Profile" (UPP) to fix the
relationship between the cluster characteristic size (R_500) and the integrated
Compton parameter (Y_500). The UPP scalings are found to be nearly identical to
an adiabatic model, while a model incorporating non-thermal pressure better
matches dynamical mass measurements and masses from the South Pole Telescope. A
high signal to noise ratio subsample of 15 ACT clusters is used to obtain
cosmological constraints. We first confirm that constraints from SZ data are
limited by uncertainty in the scaling relation parameters rather than sample
size or measurement uncertainty. We next add in seven clusters from the ACT
Southern survey, including their dynamical mass measurements based on galaxy
velocity dispersions. In combination with WMAP7 these data simultaneously
constrain the scaling relation and cosmological parameters, yielding \sigma_8 =
0.829 \pm 0.024 and \Omega_m = 0.292 \pm 0.025. The results include
marginalization over a 15% bias in dynamical mass relative to the true halo
mass. In an extension to LCDM that incorporates non-zero neutrino mass density,
we combine our data with WMAP7+BAO+Hubble constant measurements to constrain
\Sigma m_\nu < 0.29 eV (95% C. L.).Comment: 32 pages, 21 figures To appear in J. Cosmology and Astroparticle
Physic
Planet Hunters. VI: An Independent Characterization of KOI-351 and Several Long Period Planet Candidates from the Kepler Archival Data
We report the discovery of 14 new transiting planet candidates in the Kepler
field from the Planet Hunters citizen science program. None of these candidates
overlapped with Kepler Objects of Interest (KOIs) at the time of submission. We
report the discovery of one more addition to the six planet candidate system
around KOI-351, making it the only seven planet candidate system from Kepler.
Additionally, KOI-351 bears some resemblance to our own solar system, with the
inner five planets ranging from Earth to mini-Neptune radii and the outer
planets being gas giants; however, this system is very compact, with all seven
planet candidates orbiting AU from their host star. A Hill
stability test and an orbital integration of the system shows that the system
is stable. Furthermore, we significantly add to the population of long period
transiting planets; periods range from 124-904 days, eight of them more than
one Earth year long. Seven of these 14 candidates reside in their host star's
habitable zone.Comment: 27 pages, 6 figures, 5 tables, Accepted to AJ (in press) (updated
title from original astro-ph submission
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