University of Warsaw

About: University of Warsaw is a education organization based out in Warsaw, Poland. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 20832 authors who have published 56617 publications receiving 1185084 citations. The organization is also known as: Uniwersytet Warszawski & Warsaw University.

Semistable sheaves in positive characteristic

Abstract: We prove Maruyama’s conjecture on the boundedness of slope semistable sheaves on a projective variety defined over a noetherian ring. Our approach also gives a new proof of the boundedness for varieties defined over a characteristic zero field. This result implies that in mixed characteristic the moduli spaces of Gieseker semistable sheaves are projective schemes of finite type. The proof uses a new inequality bounding slopes of the restriction of a sheaf to a hypersurface in terms of its slope and the discriminant. This inequality also leads to effective restriction theorems in all characteristics, improving earlier results in characteristic zero.

Solar neutrino results in Super-Kamiokande-III

Abstract: The results of the third phase of the Super-Kamiokande solar neutrino measurement are presented and compared to the first and second phase results. With improved detector calibrations, a full detector simulation, and improved analysis methods, the systematic uncertainty on the total neutrino flux is estimated to be $\ifmmode\pm\else\textpm\fi{}2.1%$, which is about two thirds of the systematic uncertainty for the first phase of Super-Kamiokande. The observed $^{8}\mathrm{B}$ solar flux in the 5.0 to 20 MeV total electron energy region is $2.32\ifmmode\pm\else\textpm\fi{}0.04(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.05(\mathrm{sys})\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{sec}}^{\ensuremath{-}1}$ under the assumption of pure electron-flavor content, in agreement with previous measurements. A combined oscillation analysis is carried out using SK-I, II, and III data, and the results are also combined with the results of other solar neutrino experiments. The best-fit oscillation parameters are obtained to be ${sin }^{2}{\ensuremath{\theta}}_{12}={0.30}_{\ensuremath{-}0.01}^{+0.02}({tan }^{2}{\ensuremath{\theta}}_{12}={0.42}_{\ensuremath{-}0.02}^{+0.04})$ and $\ensuremath{\Delta}{m}_{21}^{2}={6.2}_{\ensuremath{-}1.9}^{+1.1}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }{\mathrm{eV}}^{2}$. Combined with KamLAND results, the best-fit oscillation parameters are found to be ${sin }^{2}{\ensuremath{\theta}}_{12}=0.31\ifmmode\pm\else\textpm\fi{}0.01({tan }^{2}{\ensuremath{\theta}}_{12}=0.44\ifmmode\pm\else\textpm\fi{}0.03)$ and $\ensuremath{\Delta}{m}_{21}^{2}=7.6\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }{\mathrm{eV}}^{2}$. The $^{8}\mathrm{B}$ neutrino flux obtained from global solar neutrino experiments is $5.3\ifmmode\pm\else\textpm\fi{}0.2(\mathrm{stat}+\mathrm{sys})\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$, while the $^{8}\mathrm{B}$ flux becomes $5.1\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{stat}+\mathrm{sys})\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ by adding KamLAND results. In a three-flavor analysis combining all solar neutrino experiments, the upper limit of ${sin }^{2}{\ensuremath{\theta}}_{13}$ is 0.060 at 95% C.L.. After combination with KamLAND results, the upper limit of ${sin }^{2}{\ensuremath{\theta}}_{13}$ is found to be 0.059 at 95% C.L.

Computer-Assisted Synthetic Planning: The End of the Beginning.

Abstract: Exactly half a century has passed since the launch of the first documented research project (1965 Dendral) on computer-assisted organic synthesis. Many more programs were created in the 1970s and 1980s but the enthusiasm of these pioneering days had largely dissipated by the 2000s, and the challenge of teaching the computer how to plan organic syntheses earned itself the reputation of a "mission impossible". This is quite curious given that, in the meantime, computers have "learned" many other skills that had been considered exclusive domains of human intellect and creativity-for example, machines can nowadays play chess better than human world champions and they can compose classical music pleasant to the human ear. Although there have been no similar feats in organic synthesis, this Review argues that to concede defeat would be premature. Indeed, bringing together the combination of modern computational power and algorithms from graph/network theory, chemical rules (with full stereo- and regiochemistry) coded in appropriate formats, and the elements of quantum mechanics, the machine can finally be "taught" how to plan syntheses of non-trivial organic molecules in a matter of seconds to minutes. The Review begins with an overview of some basic theoretical concepts essential for the big-data analysis of chemical syntheses. It progresses to the problem of optimizing pathways involving known reactions. It culminates with discussion of algorithms that allow for a completely de novo and fully automated design of syntheses leading to relatively complex targets, including those that have not been made before. Of course, there are still things to be improved, but computers are finally becoming relevant and helpful to the practice of organic-synthetic planning. Paraphrasing Churchill's famous words after the Allies' first major victory over the Axis forces in Africa, it is not the end, it is not even the beginning of the end, but it is the end of the beginning for the computer-assisted synthesis planning. The machine is here to stay.

Food thresholds and body size in cladocerans

Abstract: ACCORDING to the size–efficiency hypothesis1, body size is one of the most important determinants of the relative abundance of planktonic animals in nature. First, large-bodied species are more vulnerable to predation by visually feeding planktivorous fishes. Second, they are superior competitors for resources, being able to grow and reproduce at lower food concentrations. But whereas the first assumption has been confirmed by many field and experimental data (for review see refs 2–4), the second suggestion lacks experimental evidence and has been frequently questioned5-12. I now present experimental data from eight filter-feeding species (family Daphnidae) that strongly support the cornerstone assumption of the competitive aspect of the size-efficiency hypothesis. These data show that the threshold food concentration necessary to assure that assimilation equals respiration13, is lower for the large-bodied species than it is for the small-bodied species under steady-state and low-mortality conditions.

Nuclear Energy Density Optimization

Abstract: We carry out state-of-the-art optimization of a nuclear energy density of Skyrme type in the framework of the Hartree-Fock-Bogoliubov theory. The particle-hole and particle-particle channels are optimized simultaneously, and the experimental data set includes both spherical and deformed nuclei. The new model-based, derivative-free optimization algorithm used in this work has been found to be significantly better than standard optimization methods in terms of reliability, speed, accuracy, and precision. The resulting parameter set unedf0 results in good agreement with experimental masses, radii, and deformations and seems to be free of finite-size instabilities. An estimate of the reliability of the obtained parameterization is given, based on standard statistical methods. We discuss new physics insights offered by the advanced covariance analysis.