منابع مشابه
A descent method for explicit computations on curves
It is shown that the knowledge of a surjective morphism $Xto Y$ of complex curves can be effectively used to make explicit calculations. The method is demonstrated by the calculation of $j(ntau)$ (for some small $n$) in terms of $j(tau)$ for the elliptic curve with period lattice $(1,tau)$, the period matrix for the Jacobian of a family of genus-$2$ curves complementing the classi...
متن کاملOn descent for coalgebras and type transformations
We find a criterion for a morphism of coalgebras over a Barr-exact category to be effective descent and determine (effective) descent morphisms for coalgebras over toposes in some cases. Also, we study some exactness properties of endofunctors of arbitrary categories in connection with natural transformations between them as well as those of functors that these transformations induce between co...
متن کاملPenalized Bregman Divergence Estimation via Coordinate Descent
Variable selection via penalized estimation is appealing for dimension reduction. For penalized linear regression, Efron, et al. (2004) introduced the LARS algorithm. Recently, the coordinate descent (CD) algorithm was developed by Friedman, et al. (2007) for penalized linear regression and penalized logistic regression and was shown to gain computational superiority. This paper explores...
متن کاملDescent of a split RNA.
tmRNA is found in the usual one-piece form in most cyanobacteria, but a small clade has an unusual two-piece form, resulting from processing of a circularly permuted precursor RNA. Here, the secondary structure of the cyanobacterial one-piece tmRNA is established by phylogenetic sequence comparison; it deviates from most tmRNAs in having an extra (fifth) pseudoknot and a branched structure at t...
متن کاملA Gentle Introduction to Descent
!! Ui // X The modules Mi are “restrictions“ or pullbacks of M along Ui → X, and are compatible in that if Mi,j is the pullback of Mi over Ui along Ui ×X Uj → Ui, then we have isomorphisms Mi,j ∼= Mj,i that satisfy a coherence condition known as the cocycle condition. We say that modules over affine schemes have the property of descent for a family {Ui → X} if any family of compatible modules M...
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ژورنال
عنوان ژورنال: The Iowa Review
سال: 1971
ISSN: 0021-065X,2330-0361
DOI: 10.17077/0021-065x.1176