14,888 research outputs found
Aspects of Defects in 3d-3d Correspondence
In this paper we study supersymmetric co-dimension 2 and 4 defects in the
compactification of the 6d theory of type on a 3-manifold
. The so-called 3d-3d correspondence is a relation between complexified
Chern-Simons theory (with gauge group ) on and a 3d
theory . We establish a dictionary for this
correspondence in the presence of supersymmetric defects, which are knots/links
inside the 3-manifold. Our study employs a number of different methods:
state-integral models for complex Chern-Simons theory, cluster algebra
techniques, domain wall theory , 5d SYM, and also
supergravity analysis through holography. These methods are complementary and
we find agreement between them. In some cases the results lead to highly
non-trivial predictions on the partition function. Our discussion includes a
general expression for the cluster partition function, in particular for
non-maximal punctures and . We also highlight the non-Abelian description
of the 3d theory with defect included, as well as its
Higgsing prescription and the resulting `refinement' in complex CS theory. This
paper is a companion to our shorter paper arXiv:1510.03884, which summarizes
our main results.Comment: 129 pages (sorry), 22 figure
uvby-Hbeta CCD photometry and membership segregation of the open cluster NGC 2548; Gaps in the Main Sequence of open clusters
Deep CCD photometry in the uvby-Hbeta intermediate-band system is presented
for the cluster NGC 2548 (M 48). A complete membership analysis based on
astrometric and photometric criteria is applied. The photometric analysis of a
selected sample of stars yields a reddening value of E(b-y)=0.06\pm0.03, a
distance modulus of V_0-M_V=9.3\pm0.5 (725 pc) and a metallicity of [Fe/H]=
-0.24\pm0.27. Through isochrone fitting we find an age of log t = 8.6\pm0.1
(400 Myr). Our optical photometry and JHK from 2MASS are combined to derive
effective temperatures of cluster member stars. The effective temperature
distribution along the main sequence of the cluster shows several gaps. A test
to study the significance of these gaps in the main sequence of the HR diagram
has been applied. The method is also applied to several other open clusters
(Pleiades, Hyades, NGC 1817 and M 67) to construct a sequence of metallicities
and ages. The comparison of the results of each cluster gives four gaps with
high significance (one of them, centred at 4900 K, has not been previously
reported).Comment: 11 pages, 8 figures, A&A in press. Corrected typos on Table
Jellyfish: The origin and distribution of extreme ram-pressure stripping events in massive galaxy clusters
We investigate the observational signatures and physical origin of ram-pressure stripping (RPS) in 63 massive galaxy clusters at z = 0.3â0.7, based on images obtained with the Hubble Space Telescope. Using a training set of a dozen âjellyfishâ galaxies identified earlier in the same imaging data, we define morphological criteria to select 211 additional, less obvious cases of RPS. Spectroscopic follow-up observations of 124 candidates so far confirmed 53 as cluster members. For the brightest and most favourably aligned systems, we visually derive estimates of the projected direction of motion based on the orientation of apparent compression shocks and debris trails. Our findings suggest that the onset of these events occurs primarily at large distances from the cluster core (>400 kpc), and that the trajectories of the affected galaxies feature high-impact parameters. Simple models show that such trajectories are highly improbable for galaxy infall along filaments but common for infall at high velocities, even after observational biases are accounted for, provided the duration of the resulting RPS events is âČ500 Myr. We thus tentatively conclude that extreme RPS events are preferentially triggered by cluster mergers, an interpretation that is supported by the disturbed dynamical state of many of the host clusters. This hypothesis implies that extreme RPS might occur also near the cores of merging poor clusters or even merging groups of galaxies. Finally, we present nine additional âjellyfishâ galaxies at z > 0.3 discovered by us, thereby doubling the number of such systems known at intermediate redshift
The Co-Evolution of Test Maintenance and Code Maintenance through the lens of Fine-Grained Semantic Changes
Automatic testing is a widely adopted technique for improving software
quality. Software developers add, remove and update test methods and test
classes as part of the software development process as well as during the
evolution phase, following the initial release. In this work we conduct a large
scale study of 61 popular open source projects and report the relationships we
have established between test maintenance, production code maintenance, and
semantic changes (e.g, statement added, method removed, etc.). performed in
developers' commits.
We build predictive models, and show that the number of tests in a software
project can be well predicted by employing code maintenance profiles (i.e., how
many commits were performed in each of the maintenance activities: corrective,
perfective, adaptive). Our findings also reveal that more often than not,
developers perform code fixes without performing complementary test maintenance
in the same commit (e.g., update an existing test or add a new one). When
developers do perform test maintenance, it is likely to be affected by the
semantic changes they perform as part of their commit.
Our work is based on studying 61 popular open source projects, comprised of
over 240,000 commits consisting of over 16,000,000 semantic change type
instances, performed by over 4,000 software engineers.Comment: postprint, ICSME 201
Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
We present cosmological parameter constraints based on the final nine-year
WMAP data, in conjunction with additional cosmological data sets. The WMAP data
alone, and in combination, continue to be remarkably well fit by a
six-parameter LCDM model. When WMAP data are combined with measurements of the
high-l CMB anisotropy, the BAO scale, and the Hubble constant, the densities,
Omegabh2, Omegach2, and Omega_L, are each determined to a precision of ~1.5%.
The amplitude of the primordial spectrum is measured to within 3%, and there is
now evidence for a tilt in the primordial spectrum at the 5sigma level,
confirming the first detection of tilt based on the five-year WMAP data. At the
end of the WMAP mission, the nine-year data decrease the allowable volume of
the six-dimensional LCDM parameter space by a factor of 68,000 relative to
pre-WMAP measurements. We investigate a number of data combinations and show
that their LCDM parameter fits are consistent. New limits on deviations from
the six-parameter model are presented, for example: the fractional contribution
of tensor modes is limited to r<0.13 (95% CL); the spatial curvature parameter
is limited to -0.0027 (+0.0039/-0.0038); the summed mass of neutrinos is <0.44
eV (95% CL); and the number of relativistic species is found to be 3.84+/-0.40
when the full data are analyzed. The joint constraint on Neff and the
primordial helium abundance agrees with the prediction of standard Big Bang
nucleosynthesis. We compare recent PLANCK measurements of the
Sunyaev-Zel'dovich effect with our seven-year measurements, and show their
mutual agreement. Our analysis of the polarization pattern around temperature
extrema is updated. This confirms a fundamental prediction of the standard
cosmological model and provides a striking illustration of acoustic
oscillations and adiabatic initial conditions in the early universe.Comment: 32 pages, 12 figures, v3: Version accepted to Astrophysical Journal
Supplement Series. Includes improvements in response to referee and
community; corrected 3 entries in Table 10, (w0 & wa model). See the Legacy
Archive for Microwave Background Data Analysis (LAMBDA):
http://lambda.gsfc.nasa.gov/product/map/current/ for further detai
Real-time Cosmology
In recent years the possibility of measuring the temporal change of radial
and transverse position of sources in the sky in real time have become
conceivable thanks to the thoroughly improved technique applied to new
astrometric and spectroscopic experiments, leading to the research domain we
call Real-time cosmology. We review for the first time great part of the work
done in this field, analysing both the theoretical framework and some endeavor
to foresee the observational strategies and their capability to constrain
models. We firstly focus on real time measurements of the overall redshift
drift and angular separation shift in distant source, able to trace background
cosmic expansion and large scale anisotropy, respectively. We then examine the
possibility of employing the same kind of observations to probe peculiar and
proper acceleration in clustered systems and therefore the gravitational
potential. The last two sections are devoted to the short time future change of
the cosmic microwave background, as well as to the temporal shift of the
temperature anisotropy power spectrum and maps. We conclude revisiting in this
context the effort made to forecast the power of upcoming experiments like
CODEX, GAIA and PLANCK in providing these new observational tools.Comment: 44 pages, 23 figures. References added; revised text, tables and
plots. Accepted for publication in Physics Report
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Characterization of the woody biomass feedstock potential resulting from California's drought.
Regional tree die-off events generate large quantities of standing dead wood, raising concern over catastrophic wildfire and other hazards. Governmental responses to tree die-off have often focused on incentivizing biomass energy production that utilizes standing dead trees removed for safety concerns. However, the full distribution of potential woody bioenergy feedstock after tree die-off has not been evaluated due to the complexities of surveying and precisely measuring large forested areas. In this paper, we present a novel method for estimating standing dead biomass at a fine spatial resolution that combines aerial survey data with forest structure maps. Using this method, we quantify biomass generated by the unprecedented tree die-off that occurred in California following a 4-year drought and widespread pest outbreaks. The results are used to estimate feasibly recoverable feedstock for energy production. We find that approximately 95.1 million bone-dry tons (BDT) of dead biomass resulted from 2012-2017 mortality, with a lower bound of 26.2 million BDT. In other words, of the aboveground live tree biomass in 2012, ~1.3-4.8% died by 2017. Of the standing dead biomass, 29% meets minimum constraints for potential cost-effective bioenergy feedstock. This proportion drops to as low as 15% in the most affected areas due to terrain slope, wilderness status, and other factors, highlighting the need to complement disposal via biomass energy with other strategies to mitigate the risks of the tree mortality crisis, which is likely to only become more severe over time due to climate change
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