Zobrazeno 1 - 10
of 50
pro vyhledávání: '"Stefan Schröer"'
Autor:
Cesar Hilario, Stefan Schröer
Publikováno v:
Épijournal de Géométrie Algébrique, Vol Volume 7 (2024)
We generalize the notion of quasielliptic curves, which have infinitesimal symmetries and exist only in characteristic two and three, to a remarkable hierarchy of regular curves having infinitesimal symmetries, defined in all characteristics and havi
Externí odkaz:
https://doaj.org/article/8f329753e44e4fc7af888bd3f103d6f4
Autor:
Andrea Fanelli, Stefan Schröer
Publikováno v:
Épijournal de Géométrie Algébrique, Vol Volume 4 (2020)
We introduce and study the maximal unipotent finite quotient for algebraic group schemes in positive characteristics. Applied to Picard schemes, this quotient encodes unusual torsion. We construct integral Fano threefolds where such unusual torsion a
Externí odkaz:
https://doaj.org/article/43f3e4b0cd984ba9aa3795d0644d9997
Autor:
Stefan Schröer
Publikováno v:
European Journal of Mathematics. 7:489-525
Building on the results of Deligne and Illusie on liftings to truncated Witt vectors, we give a criterion for non-liftability that involves only the dimension of certain cohomology groups of vector bundles arising from the Frobenius pushforward of th
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_________::69ae76bab5ae03904ad5c1d10d226e19
https://doi.org/10.1007/s40879-021-00451-2
https://doi.org/10.1007/s40879-021-00451-2
Autor:
Stefan Schröer, Shigeyuki Kondō
Publikováno v:
manuscripta mathematica. 166:323-342
We introduce Kummer surfaces X=Km(CxC) with the group scheme G=mu_2 acting on the self-product of the rational cuspidal curve in characteristic two. The resulting quotients are normal surfaces having a configuration of sixteen rational double points
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::76c72e92a32c3ef6e73bcb56c5838306
https://doi.org/10.1007/s00229-020-01257-4
https://doi.org/10.1007/s00229-020-01257-4
Autor:
Dino Lorenzini, Stefan Schröer
Let p be prime. We describe explicitly the resolution of singularities of several families of wild Z/pZ-quotient singularities in dimension two, including families that generalize the quotient singularities of type E_6, E_7, and E_8 from p=2 to arbit
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::30cae1a055a69e1304cbb53506bb6f63
Autor:
Stefan Schröer, Andrea Fanelli
Publikováno v:
Épijournal de Géométrie Algébrique
Épijournal de Géométrie Algébrique, EPIGA, 2020
Épijournal de Géométrie Algébrique, EPIGA, 2020
We introduce and study the maximal unipotent finite quotient for algebraic group schemes in positive characteristics. Applied to Picard schemes, this quotient encodes unusual torsion. We construct integral Fano threefolds where such unusual torsion a
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::5ccb20cf470b16d62beb2e1e50393105
https://epiga.episciences.org/6151
https://epiga.episciences.org/6151
Autor:
Stefan Schröer
We give a geometric interpretation of sheaf cohomology for higher degrees n in terms of torsors on the member of degree d=n-1 in hypercoverings of type r=n-2, endowed with an additional data, the so-called rigidification. This generalizes the fact th
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::ec5b9606bd447133a59e0a40cf6bb782
http://arxiv.org/abs/2005.12539
http://arxiv.org/abs/2005.12539
Autor:
Stefan Schröer
We classify elliptic curves over the rationals whose N\'eron model over the integers is semi-abelian, with good reduction at p=2, and whose Mordell--Weil group contains an element of order two that stays non-trivial at p=2. Furthermore, we describe t
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::39f9b100587c6d8f01647185fbe54b9c
http://arxiv.org/abs/2005.10025
http://arxiv.org/abs/2005.10025
Autor:
Stefan Schröer
We show that there is no family of Enriques surfaces over the ring of integers. This extends non-existence results of Minkowski for families of finite \'etale schemes, of Tate and Ogg for families of elliptic curves, and of Fontaine and Abrashkin for
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::ac816b40a70cb3c93f1b3f494e5de97d
Autor:
Stefan Schröer, Keiji Oguiso
Building on work of Segre and Koll'ar on cubic hypersurfaces, we construct over imperfect fields of characteristic p\geq 3 particular hypersurfaces of degree p, which show that geometrically rational schemes that are regular and whose rational points
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::6036d0163088d3ef0e7d0e973899e385