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The Mumford conjecture

Geoffrey Powell (2004/2005)

Séminaire Bourbaki

The Mumford Conjecture asserts that the rational cohomology of the stable moduli space of Riemann surfaces is a polynomial algebra on the Mumford-Morita-Miller characteristic classes; this can be reformulated in terms of the classifying space B Γ derived from the mapping class groups. The conjecture admits a topological generalization, inspired by Tillmann’s theorem that B Γ admits an infinite loop space structure after applying Quillen’s plus construction. The text presents the proof by Madsen and...

The p -rank stratification of Artin-Schreier curves

Rachel Pries, Hui June Zhu (2012)

Annales de l’institut Fourier

We study a moduli space 𝒜𝒮 g for Artin-Schreier curves of genus g over an algebraically closed field k of characteristic p . We study the stratification of 𝒜𝒮 g by p -rank into strata 𝒜𝒮 g . s of Artin-Schreier curves of genus g with p -rank exactly s . We enumerate the irreducible components of 𝒜𝒮 g , s and find their dimensions. As an application, when p = 2 , we prove that every irreducible component of the moduli space of hyperelliptic k -curves with genus g and 2 -rank s has dimension g - 1 + s . We also determine all pairs ( p , g ) for...

The structure of a local embedding and Chern classes of weighted blow-ups

Anca M. Mustaţǎ, Andrei Mustaţǎ (2012)

Journal of the European Mathematical Society

For a proper local embedding between two Deligne-Mumford stacks Y and X , we find, under certain mild conditions, a new (possibly non-separated) Deligne-Mumford stack X ' , with an etale, surjective and universally closed map to the target X , and whose fiber product with the image of the local embedding is a finite union of stacks with corresponding etale, surjective and universally closed maps to Y . Moreover, a natural set of weights on the substacks of X ' allows the construction of a universally closed...

The tautological ring of M 1 , n c t

Mehdi Tavakol (2011)

Annales de l’institut Fourier

We describe the tautological ring of the moduli space of stable n -pointed curves of genus one of compact type. It is proven that it is a Gorenstein algebra.

Toward Clemens' Conjecture in Degrees between 10 and 24

Johnsen, Trygve, Kleiman, Steven (1997)

Serdica Mathematical Journal

1 Supported in part by the Norwegian Research Council for Science and the Humanities. It is a pleasure for this author to thank the Department of Mathematics of the University of Sofia for organizing the remarkable conference in Zlatograd during the period August 28-September 2, 1995. It is also a pleasure to thank the M.I.T. Department of Mathematics for its hospitality from January 1 to July 31, 1993, when this work was started. 2Supported in part by NSF grant 9400918-DMS.We introduce and study...

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