173,460 research outputs found
The Discovery of Sgr A*
The compact radio source Sgr A* is associated with a 3.6 million black hole
at the center of the Milky Way. The radio source was discovered in February
1974 by Bruce Balick and Robert L.Brown. The National Radio Astronomy
Observatory's Green Bank 35 km radio link interferometer was used. We discuss
other observations in the years 1965-1985 as well as early VLBI observations.
The name Sgr A* was used for the first time in 1982 by Robert L.Brown and has
become the accepted name in the intervening years.Comment: 8 pages,2 figures. Conference proceedings: "The central 300 parsecs
of the Milky Way", editors A.Cotera, H.Falcke, T.R.Geballe, S.Markof
Afterthoughts | Complexities of Potency
Afterthoughts to themed perspectives on Complexities of Potency
Moduli of PT-semistable objects II
We generalise the techniques of semistable reduction for flat families of
sheaves to the setting of the derived category of coherent sheaves on
a smooth projective three-fold . Then we construct the moduli of
PT-semistable objects in as an Artin stack of finite type that is
universally closed. In the absence of strictly semistable objects, we construct
the moduli as a proper algebraic space of finite type.Comment: 34 pages. Exposition improved based on referee's comments, especially
the proofs of Prop 2.6 and 2.17 (of this version). References added; typos
corrected. Openness and separatedness now in a separate section. Sections 4
and 5 of previous version removed. Accepted for publication by the
Transactions of the American Mathematical Society. This is the sequel to
http://arxiv.org/abs/1011.568
A relation between higher-rank PT stable objects and quotients of coherent sheaves
On a smooth projective threefold, we construct an essentially surjective
functor from a category of two-term complexes to a category of
quotients of coherent sheaves, and describe the fibers of this functor. Under a
coprime assumption on rank and degree, the domain of coincides
with the category of higher-rank PT stable objects, which appear on one side of
Toda's higher-rank DT/PT correspondence formula. The codomain of
is the category of objects that appear on one side of another correspondence
formula by Gholampour-Kool, between the generating series of topological Euler
characteristics of two types of quot schemes.Comment: 19 page
- …