We consider the universal central extension of the Lie algebra $Vect (S^1)${math s}$ C^{infty}(S^1)$. The coadjoint representation of this Lie algebra has a...

We construct cocycles on the Lie algebra of pseudo- and q-pseudodifferential symbols of one variable and on their close relatives: the sine-algebra and the...

We classify non-trivial (non-central) extensions of the group $Diff^+(S^1)$ of all diffeomorphisms of the circle preserving its orientation and of the Lie...

Finding distances in astronomy is notoriously difficult. With accurate optical spectroscopy, both the distance to and extinction (reddening) of normal stars can...

Calculations of atmospheric transmission through the M (5 microns) atmospheric window, at a resolution of 10 to the 3rd power are presented for sites at the...

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We present a study of the atmospheric extinction over the observatories of the Canary Islands, based mainly on photometric measurements of the V-band extinction...

Evolution of surface magnetic features in the star, such as stellar spots or faculae, can leave a signature in the lightcurves. These features allow us to study...

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