1,180,766 research outputs found
Separating weak lensing and intrinsic alignments using radio observations
We discuss methods for performing weak lensing using radio observations to
recover information about the intrinsic structural properties of the source
galaxies. Radio surveys provide unique information that can benefit weak
lensing studies, such as HI emission, which may be used to construct galaxy
velocity maps, and polarized synchrotron radiation; both of which provide
information about the unlensed galaxy and can be used to reduce galaxy shape
noise and the contribution of intrinsic alignments. Using a proxy for the
intrinsic position angle of an observed galaxy, we develop techniques for
cleanly separating weak gravitational lensing signals from intrinsic alignment
contamination in forthcoming radio surveys. Random errors on the intrinsic
orientation estimates introduce biases into the shear and intrinsic alignment
estimates. However, we show that these biases can be corrected for if the error
distribution is accurately known. We demonstrate our methods using simulations,
where we reconstruct the shear and intrinsic alignment auto and cross-power
spectra in three overlapping redshift bins. We find that the intrinsic position
angle information can be used to successfully reconstruct both the lensing and
intrinsic alignment power spectra with negligible residual bias.Comment: 17 pages, 10 figures, submitted to MNRA
Modes of Information Flow
Information flow between components of a system takes many forms and is key
to understanding the organization and functioning of large-scale, complex
systems. We demonstrate three modalities of information flow from time series X
to time series Y. Intrinsic information flow exists when the past of X is
individually predictive of the present of Y, independent of Y's past; this is
most commonly considered information flow. Shared information flow exists when
X's past is predictive of Y's present in the same manner as Y's past; this
occurs due to synchronization or common driving, for example. Finally,
synergistic information flow occurs when neither X's nor Y's pasts are
predictive of Y's present on their own, but taken together they are. The two
most broadly-employed information-theoretic methods of quantifying information
flow---time-delayed mutual information and transfer entropy---are both
sensitive to a pair of these modalities: time-delayed mutual information to
both intrinsic and shared flow, and transfer entropy to both intrinsic and
synergistic flow. To quantify each mode individually we introduce our
cryptographic flow ansatz, positing that intrinsic flow is synonymous with
secret key agreement between X and Y. Based on this, we employ an
easily-computed secret-key-agreement bound---intrinsic mutual
information&mdashto quantify the three flow modalities in a variety of systems
including asymmetric flows and financial markets.Comment: 11 pages; 10 figures;
http://csc.ucdavis.edu/~cmg/compmech/pubs/ite.ht
Drivers of organizational creativity
A path model of organizational creativity was presented; it conceptualized the influences of information sharing, learning culture, motivation, and networking on creative climate. A structural equation model was fitted to data from the pharmaceutical industry to test the proposed model. The model accounted for 86% of the variance in the creative climate dependent variable. Information sharing had a positive effect on learning culture, which in turn had a positive effect on creative climate, while there were negative direct effects of information sharing on creative climate and on intrinsic motivation. This study suggests that information sharing and intrinsic motivation are important drivers for organizational creativity in a complex R&D environment in the pharmaceutical industry. Implications of the model are discussed
Dimension Estimation Using Random Connection Models
Information about intrinsic dimension is crucial to perform dimensionality
reduction, compress information, design efficient algorithms, and do
statistical adaptation. In this paper we propose an estimator for the intrinsic
dimension of a data set. The estimator is based on binary neighbourhood
information about the observations in the form of two adjacency matrices, and
does not require any explicit distance information. The underlying graph is
modelled according to a subset of a specific random connection model, sometimes
referred to as the Poisson blob model. Computationally the estimator scales
like n log n, and we specify its asymptotic distribution and rate of
convergence. A simulation study on both real and simulated data shows that our
approach compares favourably with some competing methods from the literature,
including approaches that rely on distance information
CNN based Learning using Reflection and Retinex Models for Intrinsic Image Decomposition
Most of the traditional work on intrinsic image decomposition rely on
deriving priors about scene characteristics. On the other hand, recent research
use deep learning models as in-and-out black box and do not consider the
well-established, traditional image formation process as the basis of their
intrinsic learning process. As a consequence, although current deep learning
approaches show superior performance when considering quantitative benchmark
results, traditional approaches are still dominant in achieving high
qualitative results. In this paper, the aim is to exploit the best of the two
worlds. A method is proposed that (1) is empowered by deep learning
capabilities, (2) considers a physics-based reflection model to steer the
learning process, and (3) exploits the traditional approach to obtain intrinsic
images by exploiting reflectance and shading gradient information. The proposed
model is fast to compute and allows for the integration of all intrinsic
components. To train the new model, an object centered large-scale datasets
with intrinsic ground-truth images are created. The evaluation results
demonstrate that the new model outperforms existing methods. Visual inspection
shows that the image formation loss function augments color reproduction and
the use of gradient information produces sharper edges. Datasets, models and
higher resolution images are available at https://ivi.fnwi.uva.nl/cv/retinet.Comment: CVPR 201
Simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy number density correlations
Cosmic shear is a powerful method to constrain cosmology, provided that any
systematic effects are under control. The intrinsic alignment of galaxies is
expected to severely bias parameter estimates if not taken into account. We
explore the potential of a joint analysis of tomographic galaxy ellipticity,
galaxy number density, and ellipticity-number density cross-correlations to
simultaneously constrain cosmology and self-calibrate unknown intrinsic
alignment and galaxy bias contributions. We treat intrinsic alignments and
galaxy biasing as free functions of scale and redshift and marginalise over the
resulting parameter sets. Constraints on cosmology are calculated by combining
the likelihoods from all two-point correlations between galaxy ellipticity and
galaxy number density. The information required for these calculations is
already available in a standard cosmic shear dataset. We include contributions
to these functions from cosmic shear, intrinsic alignments, galaxy clustering
and magnification effects. In a Fisher matrix analysis we compare our
constraints with those from cosmic shear alone in the absence of intrinsic
alignments. For a potential future large area survey, such as Euclid, the extra
information from the additional correlation functions can make up for the
additional free parameters in the intrinsic alignment and galaxy bias terms,
depending on the flexibility in the models. For example, the Dark Energy Task
Force figure of merit is recovered even when more than 100 free parameters are
marginalised over. We find that the redshift quality requirements are similar
to those calculated in the absence of intrinsic alignments.Comment: 22 pages, 10 figures; extended discussion, otherwise minor changes to
match accepted version; published in Astronomy and Astrophysic
The Impact of Intrinsic Alignments: Cosmological Constraints from a Joint Analysis of Cosmic Shear and Galaxy Survey Data
Constraints on cosmology from recent cosmic shear observations are becoming
increasingly sophisticated in their treatment of potential systematic effects.
Here we present cosmological constraints which include modelling of intrinsic
alignments. We demonstrate how the results are changed for three different
intrinsic alignment models, and for two different models of the cosmic shear
galaxy population. We find that intrinsic alignments can either reduce or
increase measurements of the fluctuation amplitude parameter sigma_8 depending
on these decisions, and depending on the cosmic shear survey properties. This
is due to the interplay between the two types of intrinsic alignment, II and
GI. It has been shown that future surveys must make a careful treatment of
intrinsic alignments to avoid significant biases, and that simultaneous
constraints from shear-shear and shear-position correlation functions can
mitigate the effects. For the first time we here combine constraints from
cosmic shear surveys (shear-shear correlations) with those from "GI" intrinsic
alignment data sets (shear-position correlations). We produce updated
constraints on cosmology marginalised over two free parameters in the halo
model for intrinsic alignments. We find that the additional freedom is well
compensated by the additional information, in that the constraints are very
similar indeed to those obtained when intrinsic alignments are ignored, both in
terms of best fit values and uncertainties.Comment: 16 pages, 11 figure
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