10,451 research outputs found
The Bousfield lattice of a triangulated category and stratification
For a tensor triangulated category which is well generated in the sense of
Neeman, it is shown that the collection of Bousfield classes forms a set. This
set has a natural structure of a complete lattice which is then studied, using
the notions of stratification and support.Comment: 25 pages; minor changes from earlier version; this will appear in the
Math.
Localising subcategories for cochains on the classifying space of a finite group
The localising subcategories of the derived category of the cochains on the
classifying space of a finite group are classified. They are in one to one
correspondence with the subsets of the set of homogeneous prime ideals of the
cohomology ring .Comment: 5 pages, minor changes, accepted for publication in C. R. Math. Acad.
Sci. Pari
Local cohomology and support for triangulated categories
We propose a new method for defining a notion of support for objects in any
compactly generated triangulated category admitting small coproducts. This
approach is based on a construction of local cohomology functors on
triangulated categories, with respect to a central ring of operators. Suitably
specialized one recovers, for example, the theory for commutative noetherian
rings due to Foxby and Neeman, the theory of Avramov and Buchweitz for complete
intersection local rings, and varieties for representations of finite groups
according to Benson, Carlson, and Rickard. We give explicit examples of objects
whose triangulated support and cohomological support differ. In the case of
group representations, this allows us to correct and establish a conjecture of
Benson.Comment: 40 pages. Relatively minor changes (clarifications, corrections, new
references, etc). This article will appear in the Ann. Sci. Ecole Norm. Su
Stratifying modular representations of finite groups
We classify localising subcategories of the stable module category of a
finite group that are closed under tensor product with simple (or, equivalently
all) modules. One application is a proof of the telescope conjecture in this
context. Others include new proofs of the tensor product theorem and of the
classification of thick subcategories of the finitely generated modules which
avoid the use of cyclic shifted subgroups. Along the way we establish similar
classifications for differential graded modules over graded polynomial rings,
and over graded exterior algebras.Comment: 37 pages; minor changes from the first version. This is slated to
appear in the January 2012 issue of Annals of Math., volume 175, no.
Colocalizing subcategories and cosupport
The Hom closed colocalizing subcategories of the stable module category of a
finite group are classified. Along the way, the colocalizing subcategories of
the homotopy category of injectives over an exterior algebra, and the derived
category of a formal commutative differential graded algebra, are classified.
To this end, and with an eye towards future applications, a notion of local
homology and cosupport for triangulated categories is developed, building on
earlier work of the authors on local cohomology and support.Comment: 38 pages; minor changes; to appear in J. Reine. Angew. Mat
Parallax measurements of cool brown dwarfs
Accurate parallax measurements allow us to determine physical properties of
brown dwarfs, and help us to constrain evolutionary and atmospheric models,
break the age-mass degeneracy and reveal unresolved binaries.
We measured absolute trigonometric parallaxes and proper motions of 6 cool
brown dwarfs using background galaxies to establish an absolute reference
frame. We derive the absolute J-mag. The six T brown dwarfs in our sample have
spectral types between T2.5 and T7.5 and magnitudes in J between 13.9 and 18.0,
with photometric distances below 25 pc.
The observations were taken in the J-band with the Omega-2000 camera on the
3.5 m telescope at Calar Alto, during a time period of 27 months, between March
2011 and June 2013. The number of epochs varied between 11 and 12 depending on
the object. The reduction of the astrometric measurements was carried out with
respect to the field stars. The relative parallax and proper motions were
transformed into absolute measurements using the background galaxies in our
fields.
We obtained absolute parallaxes for our six brown dwarfs with a precision
between 3 and 6 mas. We compared our results in a color-magnitude diagram with
other brown dwarfs with determined parallax and with the BT-Settl 2012
atmospheric models. For four of the six targets we found a good agreement in
luminosity with objects of similar spectral types. We obtained an improved
accuracy in the parallaxes and proper motions in comparison to previous works.
The object 2MASS J11061197+2754225 is more than 1 mag overluminous in all bands
pointing to binarity or high order multiplicity.Comment: 9 pages, 15 figures. Astronomy & Astrophysics, 201
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