Multilateral inversion of A_r, C_r and D_r basic hypergeometric series

In [Electron. J. Combin. 10 (2003), #R10], the author presented a new basic hypergeometric matrix inverse with applications to bilateral basic hypergeometric series. This matrix inversion result was directly extracted from an instance of Bailey's very-well-poised 6-psi-6 summation theorem, and involves two infinite matrices which are not lower-triangular. The present paper features three different multivariable generalizations of the above result. These are extracted from Gustafson's A_r and C_r extensions and of the author's recent A_r extension of Bailey's 6-psi-6 summation formula. By combining these new multidimensional matrix inverses with A_r and D_r extensions of Jackson's 8-phi-7 summation theorem three balanced very-well-poised 8-psi-8 summation theorems associated with the root systems A_r and C_r are derived.Comment: 24 page

A new multivariable 6-psi-6 summation formula

By multidimensional matrix inversion, combined with an A_r extension of Jackson's 8-phi-7 summation formula by Milne, a new multivariable 8-phi-7 summation is derived. By a polynomial argument this 8-phi-7 summation is transformed to another multivariable 8-phi-7 summation which, by taking a suitable limit, is reduced to a new multivariable extension of the nonterminating 6-phi-5 summation. The latter is then extended, by analytic continuation, to a new multivariable extension of Bailey's very-well-poised 6-psi-6 summation formula.Comment: 16 page

Normal-state conductivity in underdoped La_{2-x}Sr_xCuO_4 thin films: Search for nonlinear effects related to collective stripe motion

We report a detailed study of the electric-field dependence of the normal-state conductivity in La_{2-x}Sr_xCuO_4 thin films for two concentrations of doped holes, x=0.01 and 0.06, where formation of diagonal and vertical charged stripes was recently suggested. In order to elucidate whether high electric fields are capable of depinning the charged stripes and inducing their collective motion, we have measured current-voltage characteristics for various orientations of the electric field with respect to the crystallographic axes. However, even for the highest possible fields (~1000 V/cm for x=0.01 and \~300 V/cm for x=0.06) we observed no non-linear-conductivity features except for those related to the conventional Joule heating of the films. Our analysis indicates that Joule heating, rather than collective electron motion, may also be responsible for the non-linear conductivity observed in some other 2D transition-metal oxides as well. We discuss that a possible reason why moderate electric fields fail to induce a collective stripe motion in layered oxides is that fairly flexible and compressible charged stripes can adjust themselves to the crystal lattice and individual impurities, which makes their pinning much stronger than in the case of conventional rigid charge-density waves.Comment: 10 pages, 10 figures, accepted for publication in Phys. Rev.

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

The origin of the mass scales for maximal star formation efficiency and quenching: the critical role of supernovae

We use the Henriques et al. version of the Munich galaxy formation model (L-GALAXIES) to investigate why the halo and stellar mass scales above which galaxies are quenched are constant with redshift and coincide with the scale, where baryons are most efficiently converted into stars. This model assumes that central galaxies are quenched by active galactic nucleus (AGN) feedback when hot halo gas accretes on to a supermassive black hole. Nevertheless, we find that supernova (SN) feedback sets both mass scales. As haloes grow above a threshold mass, SNe can no longer eject material so their hot gas content increases, enhancing the cooling rate on to the central galaxy, its cold gas content, its star formation rate, and the growth rate of its central black hole. Strong AGN feedback terminates this short-lived phase by suppressing the fuel supply for star formation. Despite strong evolution of the halo mass – temperature relation, quenching occurs at a redshift-independent halo and stellar mass that coincides with the mass where baryons have been converted into stars with maximal efficiency. These regularities and coincidences are a result of the specific parameters selected by Monte Carlo Markov Chain (MCMC) tuning of the model to fit the observed abundance and passive fraction of galaxies over the redshift range 0 ≤ z ≤ 3. Thus they are required by the observed evolution of the galaxy population, at least in the context of models of this type.ISSN:0035-8711ISSN:1365-296

Prognosis of extrahepatic biliary atresia.

We carried out a retrospective investigation of the 89 patients with extrahepatic biliary atresia born in The Netherlands during a 10 year period. Of these 89 patients 10 had a diagnostic laparotomy only. Eight patients had an anastomosis between the proximal bile duct and the intestine, and the remaining 71 had hepatic portoenterostomies. Bile drainage was re-established in 46 (65%). After successful hepatic portoenterostomy the development of cholangitis was the most important determinant of long term survival; five year survival was 54% in the 19 patients who had cholangitis and 91% in the 27 who did not. In the whole group of 71 patients the five year survival was 47%. Seventeen patients were at least 5 years of age at the time of writing, three of whom had had liver transplantation. Three patients have cirrhosis and hyperbilirubinaemia, and the other 11 have normal bilirubin concentrations and normal or slightly raised transaminase activities. To improve these results early surgical intervention in all children with extrahepatic biliary atresia is necessary, as are better methods of prophylaxis and treatment of cholangitis