Uncertainty Quantification of Mass Models using Ensemble Bayesian Model Averaging

Developments in the description of the masses of atomic nuclei have led to various nuclear mass models that provide predictions for masses across the whole chart of nuclides. These mass models play an important role in understanding the synthesis of heavy elements in the rapid neutron capture ($r$-) process. However, it is still a challenging task to estimate the size of uncertainty associated with the predictions of each mass model. In this work, a method to quantify the mass uncertainty using \textit{ensemble Bayesian model averaging} (EBMA) is introduced. This Bayesian method provides a natural way to perform model averaging, selection, calibration, and uncertainty quantification, by combining the mass models as a mixture of normal distributions, whose parameters are optimized against the experimental data, employing the Markov chain Monte Carlo (MCMC) method using the No-U-Turn sampler (NUTS). The average size of our best uncertainty estimates of neutron separation energies based on the AME2003 data is 0.48 MeV and covers 95% of new data in the AME2020. The uncertainty estimates can also be used to detect outliers with respect to the trend of experimental data and theoretical predictions.Comment: 12 pages, 6 figure

Quantum simulation of the spin-boson model with a microwave circuit

We consider superconducting circuits for the purpose of simulating the spin-boson model. The spin-boson model consists of a single two-level system coupled to bosonic modes. In most cases, the model is considered in a limit where the bosonic modes are sufficiently dense to form a continuous spectral bath. A very well known case is the ohmic bath, where the density of states grows linearly with the frequency. In the limit of weak coupling or large temperature, this problem can be solved numerically. If the coupling is strong, the bosonic modes can become sufficiently excited to make a classical simulation impossible. Here, we discuss how a quantum simulation of this problem can be performed by coupling a superconducting qubit to a set of microwave resonators. We demonstrate a possible implementation of a continuous spectral bath with individual bath resonators coupling strongly to the qubit. Applying a microwave drive scheme potentially allows us to access the strong-coupling regime of the spin-boson model. We discuss how the resulting spin relaxation dynamics with different initialization conditions can be probed by standard qubit-readout techniques from circuit quantum electrodynamics.Comment: 23 pages, 10 figure

Einfluss einer platzierten N-Düngung und eines Nitrifikationshemmstoffs auf die N2O-Freisetzung im Gemüsebau

Es wurden ganzjährige Untersuchungen zum Einfluss eines Nitrifikationshemm-stoffs (NI, DMPP) bzw. einer N-Depot-düngung auf die N2O-Freisetzung aus einer gemüsebaulich genutzten Parabraun¬erde nahe Hohenheim durchgeführt. Als Kontrolle diente eine breitwürfige N-Düngung gleicher Düngerhöhe. In beiden Versuchsjahren konnte die annuelle N2O-Emission gegenüber der Kontrollvariante mittels NI um 40% reduziert werden. Dabei zeigte sich auch ein emissionsmindernder Effekt im Winterhalbjahr. Der Grund dafür ist bisher unklar. Im Gegensatz zum NI-Einsatz konnte die annuelle Emission mit platzierter N-Düngung nicht vermindert werden, obwohl eine Hemmung der Nitrifikation im Düngerdepot aufgrund der hohen NH4+-Konzentration nachgewiesen wurde