Using a suitably noncommutative flat matrix model, it is shown that the quantum permutation group has free orbitals: that is, a monomial in the generators of the algebra of functions can be zero for ...trivial reasons only. It is shown that any strictly intermediate quantum subgroup between the classical and quantum permutation groups must have free three-orbitals, and this is used to derive some elementary bounds for the Haar state on degree four monomials in such quantum permutation groups. Exploiting the main character, explicit formulae are given in the case of the quantum permutation group.
ABSTRACT
We present reduced images and catalogues of photometric and emission-line data (∼230 000 and ∼8000 sources, respectively) for the WFC3 (Wide Field Camera 3) Infrared Spectroscopic Parallel ...(WISP) survey. These data are made publicly available on the Mikulski Archive for Space Telescopes and include reduced images from various facilities: ground-based ugri, Hubble Space Telescope (HST) WFC3, and Spitzer IRAC (Infrared Array Camera). Coverage in at least one additional filter beyond the WFC3/IR data are available for roughly half of the fields (227 out of 483), with ∼20 per cent (86) having coverage in six or more filters from u band to IRAC 3.6 $\mu$m (0.35–3.6 $\mu$m). For the lower spatial resolution (and shallower) ground-based and IRAC data, we perform PSF (point spread function)-matched, prior-based, deconfusion photometry (i.e. forced-photometry) using the tphot software to optimally extract measurements or upper limits. We present the methodology and software used for the WISP emission-line detection and visual inspection. The former adopts a continuous wavelet transformation that significantly reduces the number of spurious sources as candidates before the visual inspection stage. We combine both WISP catalogues and perform spectral energy distribution fitting on galaxies with reliable spectroscopic redshifts and multiband photometry to measure their stellar masses. We stack WISP spectra as functions of stellar mass and redshift and measure average emission-line fluxes and ratios. We find that WISP emission-line sources are typically ‘normal’ star-forming galaxies based on the mass–excitation diagram (O iii/Hβ versus M⋆; 0.74 < zgrism < 2.31), the galaxy main sequence (SFR versus M⋆; 0.30 < zgrism < 1.45), S32 ratio versus M⋆ (0.30 < zgrism < 0.73), and O32 and R23 ratios versus M⋆ (1.27 < zgrism < 1.45).
Necessary and sufficient conditions for a Markov chain to be ergodic are that the chain is irreducible and aperiodic. This result is manifest in the case of random walks on finite groups by a ...statement about the support of the driving probability: a random walk on a finite group is ergodic if and only if the support is not concentrated on a proper subgroup, nor on a coset of a proper normal subgroup. The study of random walks on finite groups extends naturally to the study of random walks on finite quantum groups, where a state on the algebra of functions plays the role of the driving probability. Necessary and sufficient conditions for ergodicity of a random walk on a finite quantum group are given on the support projection of the driving state.
The final chapter in the long-standing mystery of the gamma-ray bursts (GRBs) centres on the origin of the short-hard class of bursts, which are suspected on theoretical grounds to result from the ...coalescence of neutron-star or black-hole binary systems. Numerous searches for the afterglows of short-hard bursts have been made, galvanized by the revolution in our understanding of long-duration GRBs that followed the discovery in 1997 of their broadband (X-ray, optical and radio) afterglow emission. Here we present the discovery of the X-ray afterglow of a short-hard burst, GRB 050709, whose accurate position allows us to associate it unambiguously with a star-forming galaxy at redshift z = 0.160, and whose optical lightcurve definitively excludes a supernova association. Together with results from three other recent short-hard bursts, this suggests that short-hard bursts release much less energy than the long-duration GRBs. Models requiring young stellar populations, such as magnetars and collapsars, are ruled out, while coalescing degenerate binaries remain the most promising progenitor candidates.
A central tool in the study of ergodic random walks on finite groups is the Upper Bound Lemma of Diaconis and Shahshahani. The Upper Bound Lemma uses Fourier analysis on the group to generate upper ...bounds for the distance to random and thus can be used to determine convergence rates for ergodic walks. The Fourier analysis of quantum groups is remarkably similar to that of classical groups. This allows for a generalisation of the Upper Bound Lemma to an Upper Bound Lemma for finite quantum groups. The Upper Bound Lemma is used to study the convergence of ergodic random walks on the dual group
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as well as on the truly quantum groups of Sekine.
Established guidelines for causal inference in epidemiological studies may be inappropriate for genetic associations. A consensus process was used to develop guidance criteria for assessing ...cumulative epidemiologic evidence in genetic associations. A proposed semi-quantitative index assigns three levels for the amount of evidence, extent of replication, and protection from bias, and also generates a composite assessment of ‘strong’, ‘moderate’ or ‘weak’ epidemiological credibility. In addition, we discuss how additional input and guidance can be derived from biological data. Future empirical research and consensus development are needed to develop an integrated model for combining epidemiological and biological evidence in the rapidly evolving field of investigation of genetic factors.
This paper presents the development of an enhanced analytical approach for modelling the load distribution in multi-bolt composite joints. The model is a closed-form extension of a spring-based ...method, where bolts and laminates are represented by a series of springs and masses. The enhancement accounts for static friction effects between the laminates, a primary mechanism of load transfer in highly torqued bolted joints. The method is validated against detailed three-dimensional finite element models and where possible, experimental results. The effect of varying bolt-torque and bolt-hole clearance on the load distribution in a three-bolt, single-lap joint is investigated and the method proves to be robust, accurate and highly efficient. Finally, the method is employed in a parameter study, where increasing bolt torque levels can be used for achieving a more even load distribution in multi-bolt joints.
This paper presents the development and validation of a global bolted joint model (GBJM), a highly efficient modelling strategy for bolted composite joints. Shell elements are used to model the ...composite laminates and the bolt is represented by a combination of beam elements coupled to rigid contact surfaces. The GBJM can capture effects such as bolt–hole clearance, bolt-torque, friction between laminates, secondary and tertiary bending in the laminates as well as the load distribution in multi-bolt joints. The GBJM is validated using both three-dimensional finite element models and experiments on both single- and multi-bolt joints. The GBJM was found to be robust, accurate and highly efficient, with time savings of up to 97% realised over full three-dimensional finite element models.
► A user-defined finite element for modelling bolted composites joints is presented. ► The element represents non-linear load-displacement behaviour of single-bolt joints. ► A combined ...analytical/numerical approach is used to formulate the element. ► The method is used to model the load distribution in twenty-bolt joints. ► The method was found to be robust, accurate and highly efficient.
This paper presents the development of a highly efficient user-defined finite element for modelling the bolt–load distribution in large-scale composite structures. The method is a combined analytical/numerical approach and is capable of representing the full non-linear load–displacement behaviour of bolted composite joints both up to, and including, joint failure. In the elastic range, the method is generic and is a numerical extension of a closed-form method capable of modelling the load distribution in single-column joints. A semi-empirical approach is used to model failure initiation and energy absorption in the joint and this has been successfully applied in models of single-bolt, single-lap joints. In terms of large-scale applications, the method is validated against an experimental study of complex load distributions in multi-row, multi-column joints. The method is robust, accurate and highly efficient, thus demonstrating its potential as a time/cost saving design tool for the aerospace industry and indeed other industries utilising bolted composite structures.
Climate change predictions derived from coupled carbon-climate models are highly dependent on assumptions about feedbacks between the biosphere and atmosphere. One critical feedback occurs if C ...uptake by the biosphere increases in response to the fossil-fuel driven increase in atmospheric CO2 ("CO2 fertilization"), thereby slowing the rate of increase in atmospheric CO2. Carbon exchanges between the terrestrial biosphere and atmosphere are often first represented in models as net primary productivity (NPP). However, the contribution of CO2 fertilization to the future global C cycle has been uncertain, especially in forest ecosystems that dominate global NPP, and models that include a feedback between terrestrial biosphere metabolism and atmospheric CO2 are poorly constrained by experimental evidence. We analyzed the response of NPP to elevated CO2 (approximately equal to 550 ppm) in four free-air CO2 enrichment experiments in forest stands. We show that the response of forest NPP to elevated CO2 is highly conserved across a broad range of productivity, with a stimulation at the median of 23 +/- 2%. At low leaf area indices, a large portion of the response was attributable to increased light absorption, but as leaf area indices increased, the response to elevated CO2 was wholly caused by increased light-use efficiency. The surprising consistency of response across diverse sites provides a benchmark to evaluate predictions of ecosystem and global models and allows us now to focus on unresolved questions about carbon partitioning and retention, and spatial variation in NPP response caused by availability of other growth limiting resources.
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