6,094 research outputs found
Finiteness results for Abelian tree models
Equivariant tree models are statistical models used in the reconstruction of
phylogenetic trees from genetic data. Here equivariant refers to a symmetry
group imposed on the root distribution and on the transition matrices in the
model. We prove that if that symmetry group is Abelian, then the Zariski
closures of these models are defined by polynomial equations of bounded degree,
independent of the tree. Moreover, we show that there exists a polynomial-time
membership test for that Zariski closure. This generalises earlier results on
tensors of bounded rank, which correspond to the case where the group is
trivial, and implies a qualitative variant of a quantitative conjecture by
Sturmfels and Sullivant in the case where the group and the alphabet coincide.
Our proofs exploit the symmetries of an infinite-dimensional projective limit
of Abelian star models.Comment: 27 pages. arXiv admin note: substantial text overlap with
arXiv:1103.533
Regular maps of high density
A regular map is a surface together with an embedded graph, having properties
similar to those of the surface and graph of a platonic solid. We analyze
regular maps with reflection symmetry and a graph of density strictly exceeding
1/2, and we conclude that all regular maps of this type belong to a family of
maps naturally defined on the Fermat curves x^n+y^n+z^n=0, excepting the one
corresponding to the tetrahedron.Comment: 13 pages, 4 figure
Uniform error bounds for smoothing splines
Almost sure bounds are established on the uniform error of smoothing spline
estimators in nonparametric regression with random designs. Some results of
Einmahl and Mason (2005) are used to derive uniform error bounds for the
approximation of the spline smoother by an ``equivalent'' reproducing kernel
regression estimator, as well as for proving uniform error bounds on the
reproducing kernel regression estimator itself, uniformly in the smoothing
parameter over a wide range. This admits data-driven choices of the smoothing
parameter.Comment: Published at http://dx.doi.org/10.1214/074921706000000879 in the IMS
Lecture Notes Monograph Series
(http://www.imstat.org/publications/lecnotes.htm) by the Institute of
Mathematical Statistics (http://www.imstat.org
Topological noetherianity for cubic polynomials
Let be the space of complex cubic polynomials in
infinitely many variables. We show that this space is
-noetherian, meaning that any
-stable Zariski closed subset is cut out by finitely many
orbits of equations. Our method relies on a careful analysis of an invariant of
cubics introduced here called q-rank. This result is motivated by recent work
in representation stability, especially the theory of twisted commutative
algebras. It is also connected to certain stability problems in commutative
algebra, such as Stillman's conjecture.Comment: 13 page
Nictaba homologs from Arabidopsis thaliana are involved in plant stress responses
Plants are constantly exposed to a wide range of environmental stresses, but evolved complicated adaptive and defense mechanisms which allow them to survive in unfavorable conditions. These mechanisms protect and defend plants by using different immune receptors located either at the cell surface or in the cytoplasmic compartment. Lectins or carbohydrate-binding proteins are widespread in the plant kingdom and constitute an important part of these immune receptors. In the past years, lectin research has focused on the stress-inducible lectins. The Nicotiana tabacum agglutinin, abbreviated as Nictaba, served as a model for one family of stress-related lectins. Here we focus on three non-chimeric Nictaba homologs from Arabidopsis thaliana, referred to as AN3, AN4, and AN5. Confocal microscopy of ArathNictaba enhanced green fluorescent protein (EGFP) fusion constructs transiently expressed in N. benthamiana or stably expressed in A. thaliana yielded fluorescence for AN4 and AN5 in the nucleus and the cytoplasm of the plant cell, while fluorescence for AN3 was only detected in the cytoplasm. RT-qPCR analysis revealed low expression for all three ArathNictabas in different tissues throughout plant development. Stress application altered the expression levels, but all three ArathNictabas showed a different expression pattern. Pseudomonas syringae infection experiments with AN4 and AN5 overexpression lines demonstrated a significantly higher tolerance of several transgenic lines to P. syringae compared to wild type plants. Finally, AN4 was shown to interact with two enzymes involved in plant defense, namely TGG1 and BGLU23. Taken together, our data suggest that the ArathNictabas represent stress-regulated proteins with a possible role in plant stress responses. On the long term this research can contribute to the development of more stress-resistant plants
Polynomials and tensors of bounded strength
Notions of rank abound in the literature on tensor decomposition. We prove
that strength, recently introduced for homogeneous polynomials by
Ananyan-Hochster in their proof of Stillman's conjecture and generalised here
to other tensors, is universal among these ranks in the following sense: any
non-trivial Zariski-closed condition on tensors that is functorial in the
underlying vector space implies bounded strength. This generalises a theorem by
Derksen-Eggermont-Snowden on cubic polynomials, as well as a theorem by
Kazhdan-Ziegler which says that a polynomial all of whose directional
derivatives have bounded strength must itself have bounded strength.Comment: Improved the bounds on strength as a function of the dimension of the
space where one first sees nontrivial equations for the tensor property
Noetherianity for infinite-dimensional toric varieties
We consider a large class of monomial maps respecting an action of the
infinite symmetric group, and prove that the toric ideals arising as their
kernels are finitely generated up to symmetry. Our class includes many
important examples where Noetherianity was recently proved or conjectured. In
particular, our results imply Hillar-Sullivant's Independent Set Theorem and
settle several finiteness conjectures due to Aschenbrenner, Martin del Campo,
Hillar, and Sullivant.
We introduce a matching monoid and show that its monoid ring is Noetherian up
to symmetry. Our approach is then to factorize a more general equivariant
monomial map into two parts going through this monoid. The kernels of both
parts are finitely generated up to symmetry: recent work by
Yamaguchi-Ogawa-Takemura on the (generalized) Birkhoff model provides an
explicit degree bound for the kernel of the first part, while for the second
part the finiteness follows from the Noetherianity of the matching monoid ring.Comment: 20 page
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