257 research outputs found
The road to deterministic matrices with the restricted isometry property
The restricted isometry property (RIP) is a well-known matrix condition that
provides state-of-the-art reconstruction guarantees for compressed sensing.
While random matrices are known to satisfy this property with high probability,
deterministic constructions have found less success. In this paper, we consider
various techniques for demonstrating RIP deterministically, some popular and
some novel, and we evaluate their performance. In evaluating some techniques,
we apply random matrix theory and inadvertently find a simple alternative proof
that certain random matrices are RIP. Later, we propose a particular class of
matrices as candidates for being RIP, namely, equiangular tight frames (ETFs).
Using the known correspondence between real ETFs and strongly regular graphs,
we investigate certain combinatorial implications of a real ETF being RIP.
Specifically, we give probabilistic intuition for a new bound on the clique
number of Paley graphs of prime order, and we conjecture that the corresponding
ETFs are RIP in a manner similar to random matrices.Comment: 24 page
The Path-Integral Approach to the N=2 Linear Sigma Model
In QFT the effective potential is an important tool to study symmetry
breaking phenomena. It is known that, in some theories, the canonical approach
and the path-integral approach yield different effective potentials. In this
paper we investigate this for the Euclidean N=2 linear sigma model. Both the
Green's functions and the effective potential will be computed in three
different ways. The relative merits of the various approaches are discussed.Comment: 2 figure
Weak lensing generated by vector perturbations and detectability of cosmic strings
We study the observational signature of vector metric perturbations through
the effect of weak gravitational lensing. In the presence of vector
perturbations, the non-vanishing signals for B-mode cosmic shear and curl-mode
deflection angle, which have never appeared in the case of scalar metric
perturbations, naturally arise. Solving the geodesic and geodesic deviation
equations, we drive the full-sky formulas for angular power spectra of weak
lensing signals, and give the explicit expressions for E-/B-mode cosmic shear
and gradient-/curl-mode deflection angle. As a possible source for seeding
vector perturbations, we then consider a cosmic string network, and discuss its
detectability from upcoming weak lensing and CMB measurements. Based on the
formulas and a simple model for cosmic string network, we calculate the angular
power spectra and expected signal-to-noise ratios for the B-mode cosmic shear
and curl-mode deflection angle. We find that the weak lensing signals are
enhanced for a smaller intercommuting probability of the string network, ,
and they are potentially detectable from the upcoming cosmic shear and CMB
lensing observations. For , the minimum detectable tension of
the cosmic string will be down to . With a
theoretically inferred smallest value , we could even detect the
string with .Comment: 39 pages, 5 figures, v2: references added, minor corrections, v3:
matches version published in JCA
The Atacama Cosmology Telescope: A Catalog of >4000 SunyaevâZelâdovich Galaxy Clusters
We present a catalog of 4195 optically confirmed SunyaevâZel'dovich (SZ) selected galaxy clusters detected with signal-to-noise ratio >4 in 13,211 deg2 of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multifrequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008 to 2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ signal versus mass-scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M500c > 3.8 Ă 1014 Mâ, evaluated at z = 0.5, for clusters detected at signal-to-noise ratio >5 in maps filtered at an angular scale of 2farcm4. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ signal mass-scaling relation, such as the Dark Energy Survey (4566 deg2), the Hyper Suprime-Cam Subaru Strategic Program (469 deg2), and the Kilo Degree Survey (825 deg2). We highlight some noteworthy objects in the sample, including potentially projected systems, clusters with strong lensing features, clusters with active central galaxies or star formation, and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr
Fine-Scale Mapping of the 4q24 Locus Identifies Two Independent Loci Associated with Breast Cancer Risk
Background: A recent association study identified a common variant (rs9790517) at 4q24 to be associated with breast cancer risk. Independent association signals and potential functional variants in this locus have not been explored.
Methods: We conducted a fine-mapping analysis in 55,540 breast cancer cases and 51,168 controls from the Breast Cancer Association Consortium.
Results: Conditional analyses identified two independent association signals among women of European ancestry, represented by rs9790517 [conditional P = 2.51 Ă 10â4; OR, 1.04; 95% confidence interval (CI), 1.02â1.07] and rs77928427 (P = 1.86 Ă 10â4; OR, 1.04; 95% CI, 1.02â1.07). Functional annotation using data from the Encyclopedia of DNA Elements (ENCODE) project revealed two putative functional variants, rs62331150 and rs73838678 in linkage disequilibrium (LD) with rs9790517 (r2 â„ 0.90) residing in the active promoter or enhancer, respectively, of the nearest gene, TET2. Both variants are located in DNase I hypersensitivity and transcription factorâbinding sites. Using data from both The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC), we showed that rs62331150 was associated with level of expression of TET2 in breast normal and tumor tissue.
Conclusion: Our study identified two independent association signals at 4q24 in relation to breast cancer risk and suggested that observed association in this locus may be mediated through the regulation of TET2.
Impact: Fine-mapping study with large sample size warranted for identification of independent loci for breast cancer risk
Threshold Ï<sup>0</sup> photoproduction on transverse polarised protons at MAMI
Polarisation-dependent differential cross sections ÏTÏT associated with the target asymmetry T have been measured for the reaction View the MathML sourceÎłpââpÏ0 with transverse target polarisation from Ï0Ï0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ballâ/âTAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for ÏTÏT have been used in combination with our previous measurements of the unpolarised cross section Ï0Ï0 and the beam asymmetry ÎŁ for a model-independent determination of S- and P -wave multipoles in the Ï0Ï0 threshold region, which includes for the first time a direct determination of the imaginary part of the E0+E0+ multipole
On ecological conceptualizations of perceptual systems and action systems
This article examines Gibson's concept of perceptual system and Reed's concept of action system. After discussing several assumptions underlying these concepts, the ontological status of these systems is considered. It is argued that perceptual systems and action systems should be conceptualized neither as parts of an animal's body nor as softly (temporarily) assembled devices; rather, they are best understood as animals' abilities to achieve functional relationships, that is, as dispositional properties. This conceptualization entails that these systems are relatively permanent properties of the animal that are causally supported by, though not identical to, anatomical substrates. Further, it entails that it is the animal that perceives and acts, not its perceptual and action systems
Measurement of the cross section of high transverse momentum ZâbbÌ production in protonâproton collisions at âs = 8 TeV with the ATLAS detector
This Letter reports the observation of a high transverse momentum ZâbbÌ signal in protonâproton collisions at âs=8 TeV and the measurement of its production cross section. The data analysed were collected in 2012 with the ATLAS detector at the LHC and correspond to an integrated luminosity of 19.5 fbâÂč. The ZâbbÌ decay is reconstructed from a pair of b -tagged jets, clustered with the anti-ktkt jet algorithm with R=0.4R=0.4, that have low angular separation and form a dijet with pT>200 GeVpT>200 GeV. The signal yield is extracted from a fit to the dijet invariant mass distribution, with the dominant, multi-jet background mass shape estimated by employing a fully data-driven technique that reduces the dependence of the analysis on simulation. The fiducial cross section is determined to be
ÏZâbbÂŻfid=2.02±0.20 (stat.) ±0.25 (syst.)±0.06 (lumi.) pb=2.02±0.33 pb,
in good agreement with next-to-leading-order theoretical predictions
International workshop on next generation gamma-ray source
A workshop on The Next Generation Gamma-Ray Source sponsored by the Office of Nuclear Physics at the Department of Energy, was held November 17-19, 2016 in Bethesda, Maryland. The goals of the workshop were to identify basic and applied research opportunities at the frontiers of nuclear physics that would be made possible by the beam capabilities of an advanced laser Compton beam facility. To anchor the scientific vision to realistically achievable beam specifications using proven technologies, the workshop brought together experts in the fields of electron accelerators, lasers, and optics to examine the technical options for achieving the beam specifications required by the most compelling parts of the proposed research programs. An international assembly of participants included current and prospective Îł-ray beam users, accelerator and light-source physicists, and federal agency program managers. Sessions were organized to foster interactions between the beam users and facility developers, allowing for information sharing and mutual feedback between the two groups. The workshop findings and recommendations are summarized in this whitepaper
International workshop on next generation gamma-ray source
A workshop on The Next Generation Gamma-Ray Source sponsored by the Office of Nuclear Physics at the Department of Energy, was held November 17-19, 2016 in Bethesda, Maryland. The goals of the workshop were to identify basic and applied research opportunities at the frontiers of nuclear physics that would be made possible by the beam capabilities of an advanced laser Compton beam facility. To anchor the scientific vision to realistically achievable beam specifications using proven technologies, the workshop brought together experts in the fields of electron accelerators, lasers, and optics to examine the technical options for achieving the beam specifications required by the most compelling parts of the proposed research programs. An international assembly of participants included current and prospective Îł-ray beam users, accelerator and light-source physicists, and federal agency program managers. Sessions were organized to foster interactions between the beam users and facility developers, allowing for information sharing and mutual feedback between the two groups. The workshop findings and recommendations are summarized in this whitepaper
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