Efficient solutions of fermionic systems using artificial neural networks

In this study, we explore the similarities and differences between variational Monte Carlo techniques that employ conventional and artificial neural network representations of the ground-state wave function for fermionic systems. Our primary focus is on shallow neural network architectures, specifically the restricted Boltzmann machine, and we examine unsupervised learning algorithms that are appropriate for modeling complex many-body correlations. We assess the advantages and drawbacks of conventional and neural network wave functions by applying them to a range of circular quantum dot systems. Our findings, which include results for systems containing up to 90 electrons, emphasize the efficient implementation of these methods on both homogeneous and heterogeneous high-performance computing facilities

Self consistent and covariant propagation of pions, nucleon and isobar resonances in cold nuclear matter

We evaluate the in-medium spectral functions for pions, nucleon and isobar resonances in a self consistent and covariant manner. The calculations are based on a recently developed formulation which leads to predictions in terms of the pion-nucleon scattering phase shifts and a set of Migdal parameters describing important short range correlation effects. We do not observe significant softening of pion modes if we insist on reasonable isobar resonance properties but predict a considerable broadening of the N(1440) and N(1520) resonances in nuclear matter. Contrasted results are obtained for the s-wave N(1535) and N(1650) resonances which are affected by a nuclear environment very little. The properties of slowly moving isobar's in nuclear matter are found to depend very sensitively on a soft form factor in the piNN vertex, which is not controlled by the piN scattering data.Comment: 20 pages, 7 figure, revised manuscrip

n-3 PUFA status in school children is associated with beneficial lipid profile, reduced physical activity and increased blood pressure in boys

Published by Cambridge University Press in the British Journal of Nutrition. Damsgaard, C. T., Stark, K. D., Hjorth, M. F., Biltoft-Jensen, A., Astrup, A., Michaelsen, K. F., & Lauritzen, L. (2013). n-3 PUFA status in school children is associated with beneficial lipid profile, reduced physical activity and increased blood pressure in boys. British Journal of Nutrition, 110(07), 1304–1312. https://doi.org/10.1017/S0007114513000585. This version is free to view and download for private research and study only. Not for re-distribution, re-sale or use in derivative works. © The AuthorsDietary n-3 long-chain PUFA (LC-PUFA) improve dyslipidaemia and hypertension and may affect insulin resistance and adiposity. Increasing numbers of children show signs of the metabolic syndrome (MetS), but few studies have investigated the association with n-3 LC-PUFA status. We examined the relationship between fasting whole-blood EPA or DHA (w/w% of the total fatty acids, FA%) and markers of the MetS (anthropometry, blood pressure, plasma lipids and glucose homeostasis) cross-sectionally in seventy-three 8-11-year-old Danish children from the OPUS School Meal Pilot Study (OPUS is an acronym of the project 'Optimal well-being, development and health for Danish children through a healthy New Nordic Diet' and is supported by a grant from the Nordea Foundation). Also, we explored the potential mediating effects of physical activity and energy intake. Girls had higher body fat percentage (BF%), diastolic blood pressure, heart rate, plasma TAG, insulin, homeostasis model assessment-insulin resistance and glycosylated Hb than boys. Sexes did not differ in fish or macronutrient intake or whole-blood fatty acids. After adjustment for sex, age and total whole-blood fatty acid concentration, BF% and HDL: TAG increased with whole-blood EPA (beta > 0.25, P < 0.05), and HDL increased 0.35 (SEM 0.13) mmol/l per FA% EPA increase (beta = 0.30, P = 0.008). Unexpectedly, DHA was positively associated with mean arterial pressure in boys (6.3 (SEM 1.7) mmHg/FA% DHA increase, beta = 0.62, P = 0.001) and reduced physical activity in both sexes (244 (SEM 19) counts/min per FA%, beta = 20.22, P = 0.024). The associations with blood pressure and HDL remained after adjustment for physical activity, BF% and energy intake. The present study confirmed the beneficial association between n-3 LC-PUFA status and lipid profile seen in adults, but showed unexpected relationships with physical activity, BF% and blood pressure. This is the third time we have observed such tendencies in Danish children

Coherent pion production in neutrino nucleus collision in the 1 GeV region

We calculate cross sections for coherent pion production in nuclei induced by neutrinos and antineutrinos of the electron and muon type. The analogies and differences between this process and the related ones of coherent pion production induced by photons, or the (p,n) and $(^3 He, t)$ reactions are discussed. The process is one of the several ones occurring for intermediate energy neutrinos, to be considered when detecting atmospheric neutrinos. For this purpose the results shown here can be easily extrapolated to other energies and other nuclei.Comment: 13 pages, LaTex, 8 post-script figures available at [email protected]