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A self-consistent set of equations for the one-electron self-energy in the ladder approximation is derived for the attractive Hubbard model in the superconducting state. The equations provide an extension of a T-matrix formalism recently used to study the effect of electron correlations on normal-state properties. An approximation to the set of equations is solved numerically in the intermediate coupling regime, and the one-particle spectral functions are found to have four peaks. This feature is traced back to a peak in the self-energy, which is related to the formation of real-space bound states. For comparison we extend the moment approach to the superconducting state and discuss the crossover from the weak (BCS) to the intermediate coupling regime from the perspective of single-particle spectral densities.Comment: RevTeX format, 8 figures. Accepted for publication in Z.Phys.

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We have applied the Fast Fourier transform (FFT), which allows to compute efficiently convolution sums, to solve the set of self-consistent T-matrix equations to get the Green function of the two dimensional attractive-U Hubbard model below Tc, extending previous calculations of the same authors. Using a constant order parameter ∆(T ), we calculated Tc as a function of electron density and interaction strength U . These global results deviate from the BCS behavior remarkably.

Background: Clinician-assessed Expanded Disease Status Scale (EDSS) is gold standard in clinical investigations but normally unavailable in population-based, patient-centred MS-studies. Our objective was to develop a selfreported gait measure reflecting EDSS-categories. Methods: We developed the self-reported disability status scale (SRDSS) with three categories (≤3.5, 4-6.5, ≥7) based on three mobility-related questions. The SRDSS was determined for 173 persons with MS and validated against clinical EDSS to calculate sensitivity and specificity. Results: Accuracy was 88.4% (153 correctly classified) and weighted kappa 0.73 (0.62-0.84). Sensitivity/specificity-pairs were 94.5%/77.8%, 69.0%/94.7% and 100%/98.2% for SRDSS ≤3.5, 4-6.5 and ≥7, respectively. Conclusions: Self-reported SRDSS approximates EDSS-categories well and fosters comparability between clinical and population-based studies. questionnaire of the Swiss MS Registry (SMSR), only 11% knew their EDSS-score (unpublished data). This lack of knowledge amongst PwMS about the own EDSS poses substantial challenges for observational studies relying on patient self-reports such as the SMSR or the UK MS Registry, because this hinders interstudy comparability (Ford et al., 2012;Puhan et al., 2018;Steinemann et al., 2018).Although self-reported EDSS-proxy measures have been proposed, no instrument has emerged as a standard (Collins et al., 2016). Therefore, there is still a need for short, reliable, and robust instruments