Analytic formulas for the rapid evaluation of the orbit response matrix and chromatic functions from lattice parameters in circular accelerators

Measurements and analysis of orbit response matrix have been providing for decades a formidable tool in the detection of linear lattice imperfections and their correction. Basically all storage- ring-based synchrotron light sources across the world make routinely use of this technique in their daily operation, reaching in some cases a correction of linear optics down to 1% beta beating and 0.1% coupling. During the design phase of a new storage ring it is also applied in simulations for the evaluation of magnetic and mechanical tolerances. However, this technique is known for its intrinsic slowness compared to other methods based on turn-by-turn beam position data, both in the measurement and in the data analysis. In this paper analytic formulas are derived and discussed that shall greatly speed up this second part. The mathematical formalism based on the Lie algebra and the resonance driving terms is extended to the off-momentum regime and explicit analytic formulas for the evaluation of chromatic functions from lattice parameters are also derived. The robustness of these formulas, which are linear in the magnet strengths, is tested with different lattice configurations

A candidate supermassive binary black hole system in the brightest cluster galaxy of RBS 797

The radio source at the center of the cool core galaxy cluster RBS 797 (z=0.35) is known to exhibit a misalignment of its radio jets and lobes observed at different VLA-scale, with the innermost kpc-scale jets being almost orthogonal to the radio emission which extends for tens of kpc filling the X-ray cavities. Gitti et al. suggested that this peculiar radio morphology may indicate a recurrent activity of the central radio source, where the jet orientation is changing between the different outbursts due to the effects of supermassive binary black holes (SMBBHs). We aim at unveiling the nuclear radio properties of the brightest cluster galaxy (BCG) in RBS 797 and at investigating the presence of a SMBBH system in its center. We have performed new high-resolution observations at 5 GHz with the European VLBI Network (EVN), reaching an angular resolution of 9x5 mas^2 and a sensitivity of 36 microJy/beam. We report the EVN detection of two compact components in the BCG of RBS 797, with a projected separation of ~77 pc. We can envisage two possible scenarios: the two components are two different nuclei in a close binary system, or they are the core and a knot of its jet. Both interpretations are consistent with the presence of SMBBHs. Our re-analysis of VLA archival data seems to favor the first scenario, as we detect two pairs of radio jets misaligned by ~90 degrees on the same kpc scale emanating from the central radio core. If the two outbursts are almost contemporaneous, this is clear evidence of the presence of two active SMBHs, whose radio nuclei are unresolved at VLA resolution. The nature of the double source detected by our EVN observations in the BCG of RBS 797 can be established only by future sensitive, multi-frequency VLBI observations. If confirmed, RBS 797 would be the first SMBBH system observed at medium-high redshift at VLBI resolution. (abridged)Comment: 4 pages, 2 figures, A&A Letter in pres

La idea del poder en la Península Ibérica en la edad media: perspectivas universales y particulares en la General Estoria y en la Estoria de España

This article explores the meanings and interpretations of power and authority in the historical collections supervised by Alfonso X of Castile (1252-1284); namely in the ambitious project of a universal history of the General Estoria and in the events concerning the Iberian Peninsula from the origins to the reign of Ferdinand III recounted in the Estoria de España. Whilst relying significantly on the sources, these two compendia also represented an instrument of political and religious propaganda, based on an innovative legislative perspective, as well as on a more traditional theocratic framework which contributed to legitimize it. Shifting between law, religion and common practice, Alfonso X proposed a model of power where tradition merged with the pragmatic exigencies of his own era; a successful paradigm which would survive in the future