39 research outputs found
Algebraic density property of Danilov-Gizatullin surfaces
A Danilov-Gizatullin surface is an affine surface which is the complement
of an ample section of a Hirzebruch surface. The remarkable theorem of
Danilov and Gizatullin states that the isomorphism class of depends only on
the self-intersection number . In this paper we apply their theorem to
present as the quotient of an affine threefold by a torus action, and to
prove that the Lie algebra generated by the complete algebraic vector fields on
coincides with the set of all algebraic vector fields.Comment: 12 page
A Schwarz Method for the Magnetotelluric Approximation of Maxwell's equations
The magnetotelluric approximation of the Maxwell's equations is used to model
the propagation of low frequency electro-magnetic waves in the Earth's
subsurface, with the purpose of reconstructing the presence of mineral or oil
deposits. We propose a classical Schwarz method for solving this
magnetotelluric approximation of the Maxwell equations, and prove its
convergence using maximum principle techniques. This is not trivial, since
solutions are complex valued, and we need a new result that the magnetotelluric
approximations satisfy a maximum modulus principle for our proof. We illustrate
our analysis with numerical experiments.Comment: 9 pages, 3 figure
Planck Intermediate Results. XXXVI. Optical identification and redshifts of Planck SZ sources with telescopes at the Canary Islands Observatories
We present the results of approximately three years of observations of Planck
Sunyaev-Zeldovich (SZ) sources with telescopes at the Canary Islands
observatories as part of the general optical follow-up programme undertaken by
the Planck collaboration. In total, 78 SZ sources are discussed. Deep-imaging
observations were obtained for most of these sources; spectroscopic
observations in either in long-slit or multi-object modes were obtained for
many. We effectively used 37.5 clear nights. We found optical counterparts for
73 of the 78 candidates. This sample includes 53 spectroscopic redshift
determinations, 20 of them obtained with a multi-object spectroscopic mode. The
sample contains new redshifts for 27 Planck clusters that were not included in
the first Planck SZ source catalogue (PSZ1).Comment: 15 pages, 14 figures, accepted for publication in A&
VizieR Online Data Catalog: 1Jy northern AGN sample (Planck+, 2016)
The complete sample presented in this paper consists of 104 northern and equatorial radio-loud AGN. It includes all AGN with declination >=-10° that have a measured average radio flux density at 37GHz exceeding 1Jy. Most of the sample sources have been monitored at Metsahovi Radio Observatory for many years, and the brightest sources have been observed for up to 30yr. (1 data file)
VizieR Online Data Catalog: Planck Catalogue of Galactic cold clumps (PGCC) (Planck+, 2016)
The Planck Catalogue of Galactic Cold Clumps (PGCC) is a list of 13188 Galactic sources and 54 sources located in the Small and Large Magellanic Clouds. The sources have been identified in Planck data as sources colder than their environment. It has been built using the 48 months Planck data at 857, 545, and 353GHz combined with the 3THz IRAS data. (1 data file)