The radial index of a 1-form on a singular set is a generalization of the classical Poincaré-Hopf index. We consider different classes of closed singular semi-analytic sets in R that contain 0 in their singular locus and we relate the radial index of a 1-form at 0 on these sets to Poincaré-Hopf indices at 0 of vector fields defined on R.

We construct functions in the Eremenko-Lyubich class (transcendental entire functions with bounded singular set) whose level-sets have prescribed geometry. We also give a related result for the Speiser class (finite singular set) and discuss some differences between these two classes. The construction may be considered as an approximation result using functions in class B that complements recen...

We develop a geometric approach to the study of plane sextics with a triple singular point. As an application, we give an explicit geometric description of all irreducible maximal sextics with a type E7 singular point and compute their fundamental groups. All groups found are finite; one of them is nonabelian.

We study the interplay between the properties of the germ of a singular variety N ⊂ Rn given in the title and the algebra of vector fields tangent to N . The Poincare lemma property means that any closed differential (p+1)-form vanishing at any point ofN is a differential of a p-form which also vanishes at any point of N . In particular, we show that the classical quasi-homogeneity is not a nec...

We show that the theory ZFC-, consisting of the usual axioms of ZFC but with the power set axiom removed—specifically axiomatized by extensionality, foundation, pairing, union, infinity, separation, replacement and the assertion that every set can be well-ordered—is weaker than commonly supposed and is inadequate to establish several basic facts often desired in its context. For example, there ...

In this paper the authors investigate infinite-dimensional representations L in blocks of the relative (parabolic) category OS for a complex simple Lie algebra, having the property that the cohomology of the nilradical with coefficients in L “looks like” the cohomology with coefficients in a finite-dimensional module, as in Kostant’s theorem. A complete classification of these “Kostant modules”...

In statistical problems, a set of parameterized probability distributions is used to estimate the true probability distribution. If Fisher information matrix at the true distribution is singular, then it has been left unknown what we can estimate about the true distribution from random samples. In this paper, we study a singular regression problem and prove a limit theorem which shows the relat...

where án, denotes differentiation in the direction of tlie normal to 8B . As is well known, there are explicit formulas for the solutions of the aboye problems, and one can then give a very careful analysis of the solutions when, say f E LP(áB, do), 1 < p < oo . In both cases, the boundary values are taken in the sense of non-tangential convergence, Le ., if Q E aB, and F(Q) _ F. (Q) _ {X E B1 ...

We show that a cocycle has a dominated splitting if and only if there is a uniform exponential gap between singular values of its iterates. Then we consider sets Σ in GL(d, R) with the property that any cocycle with values in Σ has a dominated splitting. We characterize these sets in terms of existence of invariant multicones, thus extending a 2-dimensional result by Avila, Bochi, and Yoccoz. W...

The paper deals with the propagation of singularities of semi-convex functions. We obtain lower bounds on the degree of the singularities and on the size of the singular set in a neighborhood of a singular point. These results apply to viscosity solutions of HamiltonJacobi-Bellman equations. In particular, they provide sufficient conditions for the propagation of singularities, depending only o...