Maximal Points of Stable and Related Polynomials

We prove that any polynomial having all its roots in a closed half-plane, whose boundary contains the origin, has either one or two maximal points, and only one if it has at least one root in the open half-plane. This result concerns stable polynomials as well as polynomials having only real roots, including real orthogonal polynomials.     

Real Zeros of Algebraic Polynomials with Dependent Random Coefficients

The expected number of real zeros of polynomials a ₀ + a ₁ x + a ₂ x ² +…+a _n?1 x ^n?1 with random coefficients is well studied. For n large and for the normal zero mean independent coefficients, irrespective of the distribution of coefficients, this expected number is known to be asymptotic to (2/π)log n. For the dependent cases studied so far it is shown that this asymptotic value remains O(log n). In this article, we show that when cov(a _i , a _j ) = 1 ? |i ? j|/n, for i = 0,…, n ? 1 and j = 0,…, n ? 1, the above expected number of real zeros reduces significantly to O(log n)^1/2.     

Algebraic Polynomials with Non-identical Random Coefficients

The asymptotic estimate for the expected number of real zeros of a random algebraic polynomial is known. The identical random coefficients a_j(ω) are normally distributed defined on a probability space , ω ∈Ω. The estimate for the expected number of zeros of the derivative of the above polynomial with respect to x is also known, which gives the expected number of maxima and minima of Q_n(x, ω). In this paper we provide the asymptotic value for the expected number of zeros of the integration of Q_n(x,ω) with respect to x. We give the geometric interpretation of our results and discuss the difficulties which arise when we consider a similar problem for the case of .     

Real perturbations of complex polynomials

In this article the dynamics of generic C^r (r ≥ 3) perturbations of complex polynomials are considered. The attention is focused on the determination of the existence of large or invariant components of the complement of the basin of ∞, where the interesting dynamics occur.     

Exceedence Measure of Classes of Algebraic Polynomials

There is both mathematical and physical interest in the behaviour of the polynomial of the form . The coefficients a _j , j = 0,...,n are assumed to be independent normally distributed random variables with mean zero and variance ². In this paper by using the motion of exceedence measure for stochastic processes, for n large, we derive an asymptotic estimate for the expected area of the curve representing the above polynomial cut off by the x-axis. We show that our method can be used to obtain results for similar random polynomials.     

Cone-Decompositions and Degenerate Critical Points

Let M be a compact, smooth, 2-connected, 2m-dimensional manifoldwith M simply connected. If M has the homotopytype of an m-dimensionalCW-complex, then it supports a smooth, self-indexed function,maximal, constant and regular on M with at most cat(M) + 2 criticalpoints, all of which are of a certain ‘reasonable’type. To such a critical point there corresponds, homotopically,the attachment of a cone. Conversely, to a cone attachment wemay associate, under certain dimensionality and connectivityconditions, a ‘reasonable’ critical point. 1991Mathematics Subject Classification: primary 55M30, 57R70; secondary58E05, 55P50, 55P62.     

Rational and Homological Equivalence of Real Algebraic Cycles

In this paper we study algebraic cycles on smooth quasiprojective real algebraic varieties. We are interested under what conditions an algebraic cycle homologous to zero is rationally equivalent to a cycle supporting no real points.     

On Critical Values of Polynomials with Real Critical Points

Let f be a polynomial of degree at least 2 with f(0)=0 and f′(0)=1. Suppose that all the zeros of f′ are real. We show that there is a zero ζ of f′ such that |f(ζ)/ζ|≤2/3, and that this inequality can be taken to be strict unless f is of the form f(z)=z+cz ³.     

Algebraic cycles and topology of real Enriques surfaces

For a real Enriques surface Y we prove that every homology class in H₁(Y (R), Z/2) can be represented by a real algebraic curve if and only if all connected components of Y(R) are orientable. Furthermore, we give a characterization of real Enriques surfaces which are Galois-Maximal and/or Z-Galois-Maximal and we determine the Brauer group of any real Enriques surface Y.     

Voronoi Diagrams of Real Algebraic Sets

A collection of n (possibly singular) semi-algebraic sets in ^d of dimension d–1, each defined by polynomials of maximal degree , has ((n) ^d ) first-order Voronoi cells (for any fixed d). In the nonhypersurface case, where the maximal dimension of the semi-algebraic sets is m d–2, the number of first-order Voronoi cells is bounded above by O(n ^{m+1 d} ) (for nonsingular semi-algebraic sets) or by O((n) ^d ) (in general). The complexity of the entire kth-order Voronoi diagram of a generic collection of n non-singular real algebraic sets in R ^d of maximal dimension m<d and maximal degree is O(n ^{min(d+k,2d)2(m+1)d} ).     

On Homotopy Groups of Real Algebraic Varieties and their Complexifications

Let X ₀ be a topological component of a nonsingular real algebraic variety and i:X → X _C is a nonsingular projective complexification of X. In this paper, we will study the homomorphism on homotopy groups induced by the inclusion map i:X ₀ → X _C and obtain several results using rational homotopy theory and other standard tools of homotopy theory.     

Real Quotient Singularities and Nonsingular Real Algebraic Curves in the Boundary of the Moduli Space

The quotient of a real analytic manifold by a properly discontinuous group action is, in general, only a semianalytic variety. We study the boundary of such a quotient, i.e., the set of points at which the quotient is not analytic. We apply the results to the moduli space M_g/ of nonsingular real algebraic curves of genus g (g2). This moduli space has a natural structure of a semianalytic variety. We determine the dimension of the boundary of any connected component of M_g/. It turns out that every connected component has a nonempty boundary. In particular, no connected component of M_g/ is real analytic. We conclude that M_g/ is not a real analytic variety.     

Algebraic polynomials with non-identical random coefficients

There are many known asymptotic estimates for the expected number of real zeros of a random algebraic polynomial The coefficients are mostly assumed to be independent identical normal random variables with mean zero and variance unity. In this case, for all sufficiently large, the above expected value is shown to be . Also, it is known that if the have non-identical variance , then the expected number of real zeros increases to . It is, therefore, natural to assume that for other classes of distributions of the coefficients in which the variance of the coefficients is picked at the middle term, we would also expect a greater number of zeros than . In this work for two different choices of variance for the coefficients we show that this is not the case. Although we show asymptotically that there is some increase in the number of real zeros, they still remain . In fact, so far the case of is the only case that can significantly increase the expected number of real zeros.

     

Polynomials with Critical Values on Intervals

For polynomials P(z) with real coefficients having a fixed leading coefficient and satisfying the conditions P(z) ∈ [?1, 1] for z ∈ [?1, 1] and P(z) ∈ [?1, 1] if P′(z) = 0, we obtain new covering theorems, a Bernshtein-type inequality, and inequalities for the coefficients. The proofs are based on the use of univalent conformal mappings.     

Algebraic Equivalence and Homology Classes of Real Algebraic Cycles

In this note we study the spectral properties of a multiplication operator in the space L_p(X)^m which is given by an m by m matrix of measurable functions. Our particular interest is directed to the eigenvalues and the isolated spectral points which turn out to be eigenvalues. We apply these results in order to investigate the spectrum of an ordinary differential operator with so called “floating singularities”.     

Betti Numbers of Toric Varieties and Eulerian Polynomials

It is well known that the Eulerian polynomials, which count permutations in S _n by their number of descents, give the h-polynomial/h-vector of the simple polytopes known as permutohedra, the convex hull of the S _n -orbit for a generic weight in the weight lattice of S _n . Therefore, the Eulerian polynomials give the Betti numbers for certain smooth toric varieties associated with the permutohedra.

In this article we derive recurrences for the h-vectors of a family of polytopes generalizing this. The simple polytopes we consider arise as the orbit of a nongeneric weight, namely, a weight fixed by only the simple reflections J = {s _n , s _n?1, s _n?2,…, s _n?k+2, s _n?k+1} for some k with respect to the A _n root lattice. Furthermore, they give rise to certain rationally smooth toric varieties X(J) that come naturally from the theory of algebraic monoids. Using effectively the theory of reductive algebraic monoids and the combinatorics of simple polytopes, we obtain a recurrence formula for the Poincaré polynomial of X(J) in terms of the Eulerian polynomials.     

Lipschitz泛函的本质临界点

本文指出Ｂａｎａｃｈ空间中Ｃ^1－0（即局部Ｌｉｐｓｃｈｉｔｚ）泛函的Ｃｌａｒｋｅ－临界点一般不具有在Ｃ^1－0局部坐标变换下的不变性。据此提出了Ｃ^1－0泛函的本质临界点的概念，它能适应研究Ｃ^1－0流形上的Ｃ^1－0泛函的临界点的需要．还给出了有关本质临界点的几个结果。     

Type Numbers of Critical Points for Nonsmooth Functionals

Type numbers of critical points for Lipschitz functionals are studied. Versions of the Morse inequalities are established; it is shown that the topological index of an isolated critical point is equal to the alternated sum of its type numbers. Formulas for calculating the type numbers of the zero critical point of one functional are given.