19,207 research outputs found
Quasi-Periodic Formaldehyde Maser Flares in the Massive Protostellar Object IRAS18566+0408
We report results of an extensive observational campaign of the 6 cm
formaldehyde maser in the young massive stellar object IRAS18566+0408
(G37.55+0.20) conducted from 2002 to 2009. Using Arecibo, VLA, and GBT, we
discovered quasi-periodic formaldehyde flares (P ~ 237 days). Based on Arecibo
observations, we also discovered correlated variability between formaldehyde
(H2CO) and methanol (CH3OH) masers. The H2CO and CH3OH masers are not spatially
coincident, as demonstrated by different line velocities and high angular
resolution MERLIN observations. The flares could be caused by variations in the
infrared radiation field, possibly modulated by periodic accretion onto a young
binary system.Comment: 16 pages, 3 figures, accepted for publication in the Astrophysical
Journal Letter
Exceptional Sequences over Graded Cohen-Macaulay Rings
The concept of exceptional sequences was developed by Gorodentsev and Rudakov in [3] and generalized by Bondal in [1]. It is a crucial tool to classify exceptional modules over hereditary algebras and exceptiona
A Homological dimension related to AB rings
There are many homological dimensions which are closely related to ring
theoretic properties. The notion of a AB ring has been introduced by Huneke and
Jorgensen. It has nice homological properties. In this paper, we shall define a
homological dimension which is closely related to a AB ring, and investigate
its properties.Comment: 7page
An adaptive stabilized finite element method for the generalized Stokes problem
In this work we present an adaptive strategy (based on an a posteriori error estimator) for a stabilized finite element method for the Stokes problem, with and without a reaction term. The hierarchical type estimator is based on the solution of local problems posed on appropriate finite dimensional spaces of bubble-like functions. An equivalence result between the norm of the finite element error and the estimator is given, where the dependence of the constants on the physics of the problem is explicited. Several numerical results confirming both the theoretical results and the good performance of the estimator are given
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