Abstract The ionospheric path delay impacts single-band, very long baseline interferometry (VLBI) group delays, which limits their applicability for absolute astrometry. I consider two important cases: when observations are made simultaneously in bands, but delays only one band available a subset of observations; and one-band design. developed optimal procedures data analysis both cases using G...

This is a survey paper on cohomology theories for A∞ and E∞ ring spectra. Different constructions and main properties of topological André-Quillen cohomology and of topological derivations are described. We give sample calculations of these cohomology theories and outline applications to the existence of A∞ and E∞ structures on various spectra. We also explain the relationship between topologic...

We uncover a somewhat surprising connection between spaces of multiplicative maps between A∞-ring spectra and topological Hochschild cohomology. As a consequence we show that such spaces become infinite loop spaces after looping only once. We also prove that any multiplicative cohomology operation in complex cobordisms theory MU canonically lifts to an A∞-map MU → MU . This implies, in particul...

We present an analysis of one-dimensional models of dynamical systems that possess “coherent structures”; global structures that disperse more slowly than local trajectory separation. We study cocycles generated by expanding interval maps and the rates of decay for functions of bounded variation under the action of the associated Perron–Frobenius cocycles. We prove that when the generators are ...