12,314 research outputs found
On abelian families and holomorphic normal projective connections
We prove Chern class equalities for abelian families with a holomorphic
normal projective connection.Comment: 7 pages, LaTeX2
Terminal Fano threefolds and their smoothings
We study smoothings of Fano threefolds. We prove that the Picard number
remains constant in the case of terminal Gorenstein singularities.Comment: 6 pages, LaTeX2
Splitting jet sequences
The consequences of the splitting of higher jet sequences of vector bundles
on a compact complex (Kaehler) manifold are studied, proving an infinitesimal
convers to a result of I.Biswas.Comment: 11 pages, LaTeX2
On manifolds with holomorphic normal projective connections
The authors give a complete classification of projective threefolds admitting
a holomorphic normal projective connection. Moreover, they prove a general
structure theorem on complex projective manifolds admitting a holomorphic
normal projective connection, saying in particular, that any such manifold is
either the projective space or minimal in the sense of Mori.Comment: 19 pages, LaTeX2
Projective uniformization, extremal Chern classes and quaternionic Shimura curves
Projective structures on compact real manifolds are classical objects in real
differential geometry. Complex manifolds with a holomorphic projective
structure on the other hand form a special class as soon as the dimension is
greater than one. In the K\"ahler Einstein case, projective space, tori and
ball quotients are essentially the only examples. They can be described purely
in terms of Chern class conditions. We give a complete classification of all
projective manifolds carrying a projective structure. The only additional
examples are modular abelian families over quaternionic Shimura curves. They
can also be described purely in terms of Chern class conditions.Comment: 19 pages. arXiv admin note: text overlap with arXiv:0903.457
Holomorphic normal projective connections on projective manifolds
We study projective manifolds M admitting a (flat) holomorphic normal
projective connection and show that the Iitaka fibration (up to etale
coverings) defines a smooth abelian group scheme structure on M.Comment: 18 pages, LaTeX2
Semistability of restricted tangent bundles and a question of I. Biswas
Let M be a complex projective manifold with the property that for any compact
Riemann surface C and holomorphic map f: C -> M the pullback of the tangent
bundle of M is semistable. We prove that in this case M is a curve or a finite
etale quotient of an abelian variety answering a conjecture of I. Biswas.Comment: 13 page
Locally -optimal Designs for a Wider Class of Non-linear Models on the -dimensional Ball with applications to logit and probit models
In this paper we extend the results of Radloff and Schwabe (2018), which
could be applied for example to Poisson regression, negative binomial
regression and proportional hazard models with censoring, to a wider class of
non-linear multiple regression models. This includes the binary response models
with logit and probit link besides other. For this class of models we derive
(locally) -optimal designs when the design region is a -dimensional ball.
For the corresponding construction we make use of the concept of invariance and
equivariance in the context of optimal designs as in our previous paper. In
contrast to the former results the designs will not necessarily be exact
designs in all cases. Instead approximate designs can appear. These results can
be generalized to arbitrary ellipsoidal design regions.Comment: 11 pages, 7 figures. arXiv admin note: text overlap with
arXiv:1806.0027
Gorenstein Fano threefolds with base points in the anticanonical system
We classify all Gorenstein Fano threefolds with at worst canonical
singularities for which the anticanonical system has a nonempty base locus.Comment: 14 pages, LaTeX2e; final version, to appear in Comp. Mat
Projective Threefolds with Holomorphic Conformal Structure
The authors give a complete classification of projective threefolds admitting
a holomorphic conformal structure. A Corollary is the complete list of
projective threefolds, whose tangent bundle is a symmetric square.Comment: 10 pages, LaTeX2
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