120 research outputs found
Criteria for flatness and injectivity
Let be a commutative Noetherian ring. We give criteria for flatness of
-modules in terms of associated primes and torsion-freeness of certain
tensor products. This allows us to develop a criterion for regularity if
has characteristic , or more generally if it has a locally contracting
endomorphism. Dualizing, we give criteria for injectivity of -modules in
terms of coassociated primes and (h-)divisibility of certain \Hom-modules.
Along the way, we develop tools to achieve such a dual result. These include a
careful analysis of the notions of divisibility and h-divisibility (including a
localization result), a theorem on coassociated primes across a \Hom-module
base change, and a local criterion for injectivity.Comment: 19 page
Measurable versions of the LS category on laminations
We give two new versions of the LS category for the set-up of measurable
laminations defined by Berm\'udez. Both of these versions must be considered as
"tangential categories". The first one, simply called (LS) category, is the
direct analogue for measurable laminations of the tangential category of
(topological) laminations introduced by Colman Vale and Mac\'ias Virg\'os. For
the measurable lamination that underlies any lamination, our measurable
tangential category is a lower bound of the tangential category. The second
version, called the measured category, depends on the choice of a transverse
invariant measure. We show that both of these "tangential categories" satisfy
appropriate versions of some well known properties of the classical category:
the homotopy invariance, a dimensional upper bound, a cohomological lower bound
(cup length), and an upper bound given by the critical points of a smooth
function.Comment: 22 page
Euclidean Configuration Space Renormalization, Residues and Dilation Anomaly1
Configuration (x-)space renormalization of euclidean Feynman amplitudes in a massless quantum field theory is reduced to the study of local extensions of associate homogeneous distributions. Primitively divergent graphs are renormalized, in particular, by subtracting the residue of an analytically regularized expression. Examples are given of computing residues that involve zeta values. The renormalized Green functions are again associate homogeneous distributions of the same degree that transform under indecomposable representations of the dilation group
High-precision molecular dynamics simulation of UO2-PuO2: superionic transition in uranium dioxide
Our series of articles is devoted to high-precision molecular dynamics
simulation of mixed actinide-oxide (MOX) fuel in the rigid ions approximation
using high-performance graphics processors (GPU). In this article we assess the
10 most relevant interatomic sets of pair potential (SPP) by reproduction of
the Bredig superionic phase transition (anion sublattice premelting) in uranium
dioxide. The measurements carried out in a wide temperature range from 300K up
to melting point with 1K accuracy allowed reliable detection of this phase
transition with each SPP. The {\lambda}-peaks obtained are smoother and wider
than it was assumed previously. In addition, for the first time a pressure
dependence of the {\lambda}-peak characteristics was measured, in a range from
-5 GPa to 5 GPa its amplitudes had parabolic plot and temperatures had linear
(that is similar to the Clausius-Clapeyron equation for melting temperature).Comment: 7 pages, 6 figures, 1 tabl
Nucleosomes in gene regulation: theoretical approaches
This work reviews current theoretical approaches of biophysics and
bioinformatics for the description of nucleosome arrangements in chromatin and
transcription factor binding to nucleosomal organized DNA. The role of
nucleosomes in gene regulation is discussed from molecular-mechanistic and
biological point of view. In addition to classical problems of this field,
actual questions of epigenetic regulation are discussed. The authors selected
for discussion what seem to be the most interesting concepts and hypotheses.
Mathematical approaches are described in a simplified language to attract
attention to the most important directions of this field
Reproducibility in the absence of selective reporting : An illustration from large-scale brain asymmetry research
Altres ajuts: Max Planck Society (Germany).The problem of poor reproducibility of scientific findings has received much attention over recent years, in a variety of fields including psychology and neuroscience. The problem has been partly attributed to publication bias and unwanted practices such as p-hacking. Low statistical power in individual studies is also understood to be an important factor. In a recent multisite collaborative study, we mapped brain anatomical left-right asymmetries for regional measures of surface area and cortical thickness, in 99 MRI datasets from around the world, for a total of over 17,000 participants. In the present study, we revisited these hemispheric effects from the perspective of reproducibility. Within each dataset, we considered that an effect had been reproduced when it matched the meta-analytic effect from the 98 other datasets, in terms of effect direction and significance threshold. In this sense, the results within each dataset were viewed as coming from separate studies in an "ideal publishing environment," that is, free from selective reporting and p hacking. We found an average reproducibility rate of 63.2% (SD = 22.9%, min = 22.2%, max = 97.0%). As expected, reproducibility was higher for larger effects and in larger datasets. Reproducibility was not obviously related to the age of participants, scanner field strength, FreeSurfer software version, cortical regional measurement reliability, or regional size. These findings constitute an empirical illustration of reproducibility in the absence of publication bias or p hacking, when assessing realistic biological effects in heterogeneous neuroscience data, and given typically-used sample sizes
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