Model space truncation in shell-model fits

We carry out an interacting shell-model study of binding energies and spectra in the $sd$-shell nuclei to examine the effect of truncation of the shell-model spaces. Starting with a Hamiltonian defined in a larger space and truncating to the $sd$ shell, the binding energies are strongly affected by the truncation, but the effect on the excitation energies is an order of magnitude smaller. We then refit the matrix elements of the two-particle interaction to compensate for the space truncation, and find that it is easy to capture 90% of the binding energy shifts by refitting a few parameters. With the full parameter space of the two-particle Hamiltonian, we find that both the binding energies and the excitation energy can be fitted with remaining residual error about 5% of the average error from the truncation. Numerically, the rms initial error associated with our Hamiltonian is 3.4 MeV and the remaining residual error is 0.16 MeV. This is comparable to the empirical error found in $sd$-shell interacting shell model fits to experimental data\cite{br06}.Comment: 10 pages, 3 figure

Density dependence of in-medium nucleon-nucleon cross sections

The lowest-order correction of the density dependence of in-medium nucleon-nucleon cross sections is obtained from geometrical considerations of Pauli-blocking effects. As a by-product, it is shown that the medium corrections imply an 1/E energy dependence of the density-dependent term.Comment: 7 pages, 1 figur

Analysing long-term interactions between demand response and different electricity markets using a stochastic market equilibrium model. ESRI WP585, February 2018

Power systems based on renewable energy sources (RES) are characterised by increasingly distributed, volatile and uncertain supply leading to growing requirements for flexibility. In this paper, we explore the role of demand response (DR) as a source of flexibility that is considered to become increasingly important in future. The majority of research in this context has focussed on the operation of power systems in energy only markets, mostly using deterministic optimisation models. In contrast, we explore the impact of DR on generator investments and profits from different markets, on costs for different consumers from different markets, and on CO2 emissions under consideration of the uncertainties associated with the RES generation. We also analyse the effect of the presence of a feed-in premium (FIP) for RES generation on these impacts. We therefore develop a novel stochastic mixed complementarity model in this paper that considers both operational and investment decisions, that considers interactions between an energy market, a capacity market and a feed-in premium and that takes into account the stochasticity of electricity generation by RES. We use a Benders decomposition algorithm to reduce the computational expenses of the model and apply the model to a case study based on the future Irish power system. We find that DR particularly increases renewable generator profits. While DR may reduce consumer costs from the energy market, these savings may be (over)compensated by increasing costs from the capacity market and the feed-in premium. This result highlights the importance of considering such interactions between different markets

Nuclear composition and energy spectra in the 12 April 1969 solar particle event

Nuclear composition for several multicharged nuclei and energy spectra for hydrogen, helium, and medium nuclei measured in solar particle even