A Mixed Action Analysis of η\eta and η′\eta' Mesons

We study $\eta$ and $\eta'$ mesons and their mixing angle in a mixed action approach with so-called Osterwalder-Seiler valence quarks on a Wilson twisted mass sea. The gauge configurations have been generated by ETMC for $N_f=2+1+1$ dynamical quark flavours and for three values of the lattice spacing. The main results are that differences in between the mixed action and the unitary approach vanish towards the continuum limit with the expected rate of $\mathcal{O}(a^2)$. The individual size of the lattice artifacts depends, however, strongly on the observable used to match unitary and valence actions. Moreover, we show that for the $\eta$ mass valence and valence plus sea quark mass dependence differ significantly. Hence, in this case a re-tuning of the simulation parameters in the valence sector only is not sufficient to compensate for mismatches in the original quark masses.Comment: 30 pages, 8 figures, version accepted for publicatio

Barents Sea Shrimp - stock assessment report 2022/23

Since the 1980s, the Barents Sea has gone from a situation with high fishing pressure, cold conditions and low demersal fish stock levels, to the current situation with high levels of demersal fish stocks, reduced fishing pressure and warm conditions.Barents Sea Shrimp - stock assessment report 2022/23publishedVersio

Advice on fishing opportunities for Barents Sea shrimp in 2024

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Advice on fishing opportunities for Barents Sea shrimp in 2023

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Comparison of different lattice definitions of the topological charge

We present a comparison of different definitions of the topological charge on the lattice, using a small-volume ensemble with 2 flavours of dynamical twisted mass fermions. The investigated definitions are: index of the overlap Dirac operator, spectral projectors, spectral flow of the Hermitian Wilson-Dirac operator and field theoretic with different kinds of smoothing of gauge fields (HYP and APE smearings, gradient flow, cooling). We also show some results on the topological susceptibility.Comment: 7 pages, 2 figures, presented at the 32nd International Symposium on Lattice Field Theory (Lattice 2014), 23-28 June 2014, Columbia University, New York, NY, US