Lattices of partially local fitting classes

This article deals only with finite groups. We prove the surjectivity of the mapping from the lattice of all normal Fitting classes into the lattice of the Lockett section generated by the Fitting classes that are not Lockett classes. Moreover, we find a sufficient surjectivity condition for the mapping of the lattice of the Lockett section generated by arbitrary Fitting classes into the lattice of the Lockett section generated by ω-local Fitting classes. This confirms Lockett’s conjecture for the ω-local Fitting classes of a given characteristic.     

Equivalence classes of Niho bent functions

Equivalence classes of Niho bent functions are in one-to-one correspondence with equivalence classes of ovals in a projective plane. Since a hyperoval can produce several ovals, each hyperoval is associated with several inequivalent Niho bent functions. For all known types of hyperovals we described the equivalence classes of the corresponding Niho bent functions. For some types of hyperovals the number of equivalence classes of the associated Niho bent functions are at most 4. In general, the number of equivalence classes of associated Niho bent functions increases exponentially as the dimension of the underlying vector space grows. In small dimensions the equivalence classes were considered in detail.

     

Construction de classes de Chern éguivariantes pour un fibré vectoriel Réel

On définit des classes de Chern pour un fibré vectoriel “réel” au sens d'Atiyah [1], à valeurs dans la cohomologie équivariante paire de la base à coefficients entiers tordus. Dans le cas d'un fibré réel au sens usuel, ces classes redonnent les classes de Pontrjagin et les classes de Stiefel-Whitney.     

The nullcone of the Lie algebra of G2

This paper investigates the nilpotent conjugacy classes of the Lie algebra of the simple algebraic group of type $G_2$. These classes are determined by first finding the stratification, and then finding the classes within the strata. Except for characteristic 3, the classes coincide with the strata. In characteristic 3, one stratum splits into two orbits. If the characteristic differs from 2 and 3, the classes are determined by the singularities of the nilpotent variety. In characteristic 3, the matter is undecided yet. In characteristic 2, different classes have the same singularities.     

Using Mathematica to compute conjugacy classes

The conjugacy classes of finite groups play an important role in the representation theory of those groups, and it is useful to be able to compute the conjugacy classes quickly. A procedure is developed and then implemented with Mathematica to discover these conjugacy classes. The computations make use of the Cayley table in its regular form for the group. The conjugacy classes for C_4v, the point symmetry group of the square, are displayed.     

Ohkawa's theorem: There is a set of Bousfield classes

We give a simple proof of Ohkawa's theorem, that there is a set of Bousfield classes. The proof leads us to consider the partially ordered set of Ohkawa classes, especially as it compares to the partially ordered set of Bousfield classes.

     

Between clique-width and linear clique-width of bipartite graphs

We consider hereditary classes of bipartite graphs where clique-width is bounded, but linear clique-width is not. Our goal is identifying classes that are critical with respect to linear clique-width. We discover four such classes and conjecture that this list is complete, i.e. a hereditary class of bipartite graphs of bounded clique-width that excludes a graph from each of the four critical classes has bounded linear clique-width.     

Exotic characteristic classes of quaternionic bundles

For aC ^∞ quaternionic vector bundle, the odd-dimensional real Chern classes vanish, and this allows for a construction of secondary (exotic) characteristic classes associated with a pair of quaternionic structures of a given complex vector bundle. This construction is then applied to obtain exotic characteristic classes associated with an automorphismβ of the holomorphic tangent bundle of a Kähler manifold. These results are the complex analoga of those given for the higher order Maslov classes in [V2].     

A field guide to the matrix classes found in the literature of the linear complementarity problem

There are more than 50 matrix classes discussed in the literature of the Linear Complementarity Problem. This guide is offered as a compendium of notations, definitions, names, source information, and commentary on these many matrix classes. Also included are discussions of certain properties possessed by some (but not all) of the matrix classes considered in this guide. These properties—fullness, completeness, reflectiveness, and sign-change invariance—are the subject of another table featuring matrix classes that have one or more of them. Still another feature of this work is a matrix class inclusion map depicting relationships among the matrix classes listed herein.     

Fraternal Augmentations of graphs,Coloration and Minors

We introduce classes of graphs with bounded expansion as a generalization of both proper minor closed classes and degree bounded classes. Such classes are based on a new invariant, the greatest reduced average density (grad) of G with rank r, ${\mathrm{\nabla }}_r(G)$. We generalize to these classes some results proved for proper minor closed classes and bounded degree graphs, such as the existence of low tree-width colorings, a linear time algorithm to check subgraph isomorphism for a fixed pattern and homomorphism dualities.     

Toeplitz Operators and Division Theorems in Anisotropic Spaces of Holomorphic Functions in the Polydisc

This work is an introduction to anisotropic spaces, which have an ω-weight of analytic functions and are generalizations of Lipshitz classes in the polydisc. We prove that these classes form an algebra and are invariant with respect to monomial multiplication. These classes are described in terms of derivatives. It is established that Toeplitz operators are bounded in these (Lipschitz and Djrbashian) spaces. As an application, a theorem about the division by good-inner functions in the mentioned classes is proved.     

The classes Bm,1 and Hölder continuity for doubly degenerate parabolic equations

Inner and boundary Hölder estimates for nonnegative weak solutions of quasilinear doubly degenerate parabolic equations are established. The proof of these results is based on studing some classes B_m,1 that can be considered as extensions of the classes B₂ introduced by Ladyzhenskaya and Uraltseva and the classes B_m introduced by DiBenedetto. The embedding of the classes B_m,1 in appropriate Hölder spaces is proved. Bibliography: 20 titles.     

Tautological Ring of the Moduli Space of Generalised Parabolic Line Bundles on a Curve

In this article, we consider the tautological ring containing the extended Brill–Noether algebraic classes on the normalization of the compactified Jacobian of a complex nodal projective curve (with one node). This smallest ?-subalgebra of algebraic classes under algebraic equivalence, stable under extensions of the maps induced by multiplication maps, Pontrayagin product and Fourier transform, is shown to be generated by pullback of the Brill–Noether classes of the Jacobian of the normalized curve and some natural classes.     

On hull classes of <Emphasis Type="Italic">ℓ</Emphasis>-groups and covering classes of spaces

W denotes the category of archimedean ℓ-groups with designated weak unit and ℓ-homomorphisms that preserve the weak unit. Comp denotes the category of compact Hausdorff spaces with continuous maps. The Yosida functor is used to investigate the relationship between hull classes in W and covering classes in Comp. The central idea is that of a hull class whose hull operator preserves boundedness. We demonstrate how the Yosida functor may be used to identify hull classes in W and covering classes in Comp. In addition, we exhibit an array of order preserving bijections between certain families of hull classes and all covering classes, one of which was recently produced by Martínez. Lastly, we apply our results to answer a question of Knox and McGovern about the class of all feebly projectable ℓ-groups.     

Countability of the set of closed overclasses of some minimal classes in the partly ordered set ℒ<Subscript>2</Subscript><Superscript>3</Superscript> of all closed classes of three-valued logic that can be mapped homomorphically onto two-valued logic

The following theorem is proved: the set of closed classes containing some minimal classes in the partly ordered set ?₂ ³ of closed classes in the three-valued logic that may be mapped homomorphically onto the two-valued logic is countable.     

On the Cegrell classes

The Cegrell classes with zero boundary data are defined by certain decreasing approximating sequences of functions with different properties depending on the class in question. It is different for Cegrell classes which are given by a continuous function f, these classes are defined by an inequality. It is proved in this article that it is possible to define the Cegrell classes which are given by f in a similar manner as those classes with zero boundary data. An existence result for the Dirichlet problem for certain singular measures is proved. The article ends with three applications. Results connected to convergence in capacity, subextension of plurisubharmonic functions and integrability are proved.     

Grassmann bundles

Summary In the classical theory of the Grassmann Variety there are three principal results. The Basis Theorem asserts that the Chow ring has a selfdual linear basis of classes. Determinantal Formulawhich expresses any basic class as a determinant in the special classes. Finally the ring structure is elucidated by Pieri's Formulawhich expresses the intersection of a basic class and a special class in terms of the basic classes. Here we show how all these results can be established also for the Chow ring of a Grassmann bundle. There are however some differences. In the classical case the basic classes are Schubert classes: this is impossible in the general case as there need not be enough Schubert classes to provide a basis and in the general case there is a pair of dual bases which both reduce to the Schubert basis in the classical case. In addition to these generalizations of the classical results we also enlarge on the theory of Schubert classes developed in the important paper of Kempf and Laksov [4].Following them we shall henceforth use the phrase « determinantal formula » to mean their formula for Schubert classes and our generalization of it to « improper » Schubert classes.     

Lê cycles and Milnor classes

The purpose of this work is to establish a link between the theory of Chern classes for singular varieties and the geometry of the varieties in question. Namely, we show that if Z is a hypersurface in a compact complex manifold, defined by the complex analytic space of zeroes of a reduced non-zero holomorphic section of a very ample line bundle, then its Milnor classes, regarded as elements in the Chow group of Z, determine the global Lê cycles of Z; and vice versa: The Lê cycles determine the Milnor classes. Morally this implies, among other things, that the Milnor classes determine the topology of the local Milnor fibres at each point of Z, and the geometry of the local Milnor fibres determines the corresponding Milnor classes.     

Tautological Classes of the Stack of Rational Nodal Curves

This is the second in a series of three papers in which we investigate the rational Chow ring of the stack 𝔐₀ consisting of nodal curves of genus 0. Here we define the basic classes: the classes of strata and the Mumford classes.