14 citations · 51 across the 17 of their papers we have counts for
18 papers
Nodal Enriques surfaces are Reye congruences
Gebhard Martin, Giacomo Mezzedimi, Davide Cesare Veniani
We show that every classical Enriques surface containing a smooth rational curve is a Reye congruence.
Bounding geometrically integral del Pezzo surfaces
Fabio Bernasconi, Gebhard Martin
We prove several boundedness statements for geometrically integral normal del Pezzo surfaces over arbitrary fields. We give an explicit sharp bound on the irregularity if i…
Automorphisms of del Pezzo surfaces in odd characteristic
Igor Dolgachev, Gebhard Martin
We complete the classification of automorphism groups of del Pezzo surfaces over algebraically closed fields of odd positive characteristic.
Automorphisms of del Pezzo surfaces in characteristic 2
Igor Dolgachev, Gebhard Martin
We classify the automorphism groups of del Pezzo surfaces of degrees one and two over an algebraically closed field of characteristic two. This finishes the classification of autom…
The -arithmetic hyperbolic lattices, , in three dimensions
G. J. Martin, K. Salehi, Y. Yamashita
We identify the finitely many arithmetic lattices in the orientation preserving isometry group of hyperbolic -space generated by an element of order and a…
RDP del Pezzo surfaces with global vector fields in odd characteristic
Gebhard Martin, Claudia Stadlmayr
We classify RDP del Pezzo surfaces with global vector fields over arbitrary algebraically closed fields of characteristic . In characteristic , every RDP del Pezzo sur…
Enriques surfaces of non-degeneracy 3
Gebhard Martin, Giacomo Mezzedimi, Davide Cesare Veniani
We classify all non-extendable 3-sequences of half-fibers on Enriques surfaces. If the characteristic is different from 2, we prove in particular that every Enriques surface admits…
On extra-special Enriques surfaces
Gebhard Martin, Giacomo Mezzedimi, Davide Cesare Veniani
We refine Cossec and Dolgachev's classification of extra-special Enriques surfaces, providing a complete and concise proof.
Torsors over the Rational Double Points in Characteristic
Christian Liedtke, Gebhard Martin, Yuya Matsumoto
We study torsors under finite group schemes over the punctured spectrum of a singularity in positive characteristic. We show that the Dieudonné module of the (loc,loc)-par…
Linearly Reductive Quotient Singularities
Christian Liedtke, Gebhard Martin, Yuya Matsumoto
We study isolated quotient singularities by finite and linearly reductive group schemes (lrq singularities for short) and show that they satisfy many, but not all, of the known pro…
Automorphism groups of rational elliptic and quasi-elliptic surfaces in all characteristics
Igor Dolgachev, Gebhard Martin
We study the groups of automorphisms of rational algebraic surfaces that admit a relatively minimal pencil of curves of arithmetic genus one over an algebraically closed field of a…
Automorphism group schemes of bielliptic and quasi-bielliptic surfaces
Gebhard Martin
Bielliptic and quasi-bielliptic surfaces form one of the four classes of minimal smooth projective surfaces of Kodaira dimension . In this article, we determine the automorphism…
Weak del Pezzo surfaces with global vector fields
Gebhard Martin, Claudia Stadlmayr
We classify smooth weak del Pezzo surfaces with global vector fields over an arbitrary algebraically closed field of arbitrary characteristic . We give a complete des…
Infinitesimal automorphisms of algebraic varieties and vector fields on elliptic surfaces
Gebhard Martin
We give several results concerning the connected component of the automorphism scheme of a proper variety over a field, such as its behaviour with respect to bi…
Automorphisms of unnodal Enriques surfaces
Gebhard Martin
It follows from an observation of A. Coble in 1919 that the automorphism group of an unnodal Enriques surface contains the -congruence subgroup of the Weyl group of the …
Numerically trivial automorphisms of Enriques surfaces in characteristic
Igor Dolgachev, Gebhard Martin
An automorphism of an algebraic surface is called cohomologically (numerically) trivial if it acts identically on the second -adic cohomology group (this group modulo torsio…
Enriques surfaces with finite automorphism group in positive characteristic
Gebhard Martin
We classify Enriques surfaces with smooth K3 cover and finite automorphism group in arbitrary positive characteristic. The classification is the same as over the complex numbers ex…
Classification of Enriques surfaces with finite automorphism group in characteristic 2
Toshiyuki Katsura, Shigeyuki Kondo, Gebhard Martin
We classify supersingular and classical Enriques surfaces with finite automorphism group in characteristic 2 into 8 types according to their dual graphs of all -curves (nonsi…