Search results for "Variety"
showing 10 items of 569 documents
Rings with algebraic n-engel elements
1994
(1994). Rings with algebraic n-engel elements. Communications in Algebra: Vol. 22, No. 5, pp. 1685-1701.
An uncountable family of almost nilpotent varieties of polynomial growth
2017
A non-nilpotent variety of algebras is almost nilpotent if any proper subvariety is nilpotent. Let the base field be of characteristic zero. It has been shown that for associative or Lie algebras only one such variety exists. Here we present infinite families of such varieties. More precisely we shall prove the existence of 1) a countable family of almost nilpotent varieties of at most linear growth and 2) an uncountable family of almost nilpotent varieties of at most quadratic growth.
Hurwitz spaces of quadruple coverings of elliptic curves and the moduli space of abelian threefolds A_3(1,1,4)
2005
We prove that the moduli space A_3(1,1,4) of polarized abelian threefolds with polarization of type (1,1,4) is unirational. By a result of Birkenhake and Lange this implies the unirationality of the isomorphic moduli space A_3(1,4,4). The result is based on the study the Hurwitz space H_{4,n}(Y) of quadruple coverings of an elliptic curve Y simply branched in n points. We prove the unirationality of its codimension one subvariety H^{0}_{4,A}(Y) which parametrizes quadruple coverings ��:X --> Y with Tschirnhausen modules isomorphic to A^{-1}, where A\in Pic^{n/2}Y, and for which ��^*:J(Y)--> J(X) is injective. This is an analog of the result of Arbarello and Cornalba that the Hurwitz s…
Stabilization of the cohomology of thickenings
2016
For a local complete intersection subvariety $X=V({\mathcal I})$ in ${\mathbb P}^n$ over a field of characteristic zero, we show that, in cohomological degrees smaller than the codimension of the singular locus of $X$, the cohomology of vector bundles on the formal completion of ${\mathbb P}^n$ along $X$ can be effectively computed as the cohomology on any sufficiently high thickening $X_t=V({\mathcal I^t})$; the main ingredient here is a positivity result for the normal bundle of $X$. Furthermore, we show that the Kodaira vanishing theorem holds for all thickenings $X_t$ in the same range of cohomological degrees; this extends the known version of Kodaira vanishing on $X$, and the main new…
Traces of weighted function spaces: dyadic norms and Whitney extensions
2017
The trace spaces of Sobolev spaces and related fractional smoothness spaces have been an active area of research since the work of Nikolskii, Aronszajn, Slobodetskii, Babich and Gagliardo among others in the 1950's. In this paper we review the literature concerning such results for a variety of weighted smoothness spaces. For this purpose, we present a characterization of the trace spaces (of fractional order of smoothness), based on integral averages on dyadic cubes, which is well adapted to extending functions using the Whitney extension operator.
Affine Algebraic Varieties
2000
Algebraic geometers study zero loci of polynomials. More accurately, they study geometric objects, called algebraic varieties, that can be described locally as zero loci of polynomials. For example, every high school mathematics student has studied a bit of algebraic geometry, in learning the basic properties of conic sections such as parabolas and hyperbolas.
Motives of quadric bundles and relative intermediate jacobians of K3-Fano pairs
2015
This thesis consists of two parts. In the first part we study the Chow motive of a quadric bundle of odd relative dimension over a surface. We show that this motive admits a decomposition which involves the Prym motive of the double covering of the discriminant curve.In the second part, we consider Lagrangian fibrations, obtained as relative intermediate Jacobians of families of Fano threefolds containing a fixed K3 surface, and the existence of a symplectic compactification. In a particular case, we study a partial compactification using calculations with the software system Macaulay2.
Passive UHF RFID antennas for sensing applications: Principles, methods, and classifcations
2013
UHF passive radio-frequency identification technology is rapidly evolving from simple labeling of things to wireless pervasive sensing. A remarkable number of scientific papers demonstrate that objects in principle can have their physical properties be remotely tracked and monitored all along their life cycle. The key background is a new paradigm of antenna design that merges together the conventional communication issues with more-specific requirements about sensitivity to time-varying boundary conditions. This paper presents a unified review of the state of the art of the tag-as-sensor problem. Particular care is taken to formalize the measurement indicators and the communication and sens…
Regulation of Endurance Performance: New Frontiers
2017
Successful endurance performance requires the integration of multiple physiological and psychological systems, working together to regulate exercise intensity in a way that will reduce time taken or increase work done. The systems that ultimately limit performance of the task are hotly contested, and may depend on a variety of factors including the type of task, the environment, external influences, training status of the individual and a host of psychological constructs. These factors can be studied in isolation, or inclusively as a whole-body or integrative system. A reductionist approach has traditionally been favoured, leading to a greater understanding and emphasis on muscle and cardio…
Is there a formula for formulaic language?
2015
AbstractThis paper focuses on detecting and measuring traces of "formulaic language". For this purpose, we test a number of computational formulae that quantify the degree to which a text type incorporates inflexible sequences of words. We assess these candidate indices using a number of reference corpora representing a wide variety of text types, both routine and creative. We adopt the concept of "phrase-frame" proposed by Fletcher (2002–2007) as a means of exploring phraseological pattern variability. To date, there have been few studies explicitly addressing this issue, with the exception of Roemer (2010). We examine ten productivity indices, including Roemer's VPR, the Herfindahl-Hirsch…