Integral polynomials on Banach spaces not containing ℓ<Subscript>1</Subscript>

We give new characterizations of Banach spaces not containing ℓ₁ in terms of integral and p-dominated polynomials, extending to the polynomial setting a result of Cardassi and more recent results of Rosenthal.     

Multilinear variants of Maurey and Pietsch theorems and applications

We prove composition results for multilinear operators and multilinear variants of Maurey and Pietsch theorems both for multiple p-summing, p-dominated and p-summing multilinear operators.     

On the Cohen strongly p-summing multilinear operators

In this paper, we introduce and study a new concept of summability in the category of multilinear operators, which is the Cohen strongly p-summing multilinear operators. We prove a natural analog of the Pietsch domination theorem and we compare the notion of p-dominated multilinear operators with this class by generalizing a theorem of Bu-Cohen.     

Periods of polynomials over a Galois ring

The period of a monic polynomial over an arbitrary Galois ring GR(pe,d) is theoretically determined by using its classical factorization and Galois extensions of rings. For a polynomial f(x) the modulo p remainder of which is a power of an irreducible polynomial over the residue field of the Galois ring, the period of f(x) is characterized by the periods of the irreducible polynomial and an associated polynomial of the form (x-1)m+pg(x). Further results on the periods of such associated polynomials are obtained, in particular, their periods are proved to achieve an upper bound value in most cases. As a consequence, the period of a monic polynomial over GR(pe,d) is equal to pe-1 times the period of its modulo p remainder polynomial with a probability close to 1, and an expression of this probability is given.     

Extensions of some polynomial inequalities to the polar derivative

Let p(z) be a polynomial of degree n and for any real or complex number α, let Dαp(z)=np(z)+(α−z)p^′(z) denote the polar derivative of the polynomial p(z) with respect to α. In this paper, we obtain inequalities for the polar derivative of a polynomial having all its zeros inside or outside a circle. Our results shall generalize and sharpen some well-known polynomial inequalities.     

Some Inequalities for the Polar Derivative of Polynomials in Complex Domain

Let p(z) be a polynomial of degree n. In this paper we prove results concerning maximum modulus of the polar derivative of p(z) with restricted zeros. Our results refine and generalize certain well-known polynomial inequalities.     

Product inequalities for norms of linear factors

We give an inequality which bounds the product of the Lp norms of the linear factors of a polynomial by a multiple of the Lp norm of that polynomial. This result generalizes two inequalities of Króo and Pritsker.     

Asplund Operators and p-Integral Polynomials

We introduce the Banach ideals of p-integral and of p-nuclear polynomials for 1 ≤ p ≤ + ∞, extending to the polynomial setting the well known notions of p-integral and p-nuclear operators. For p = 1, we recover the Pietsch integral and nuclear polynomials, respectively. Given a Banach space E, let K be a compact Hausdorff space such that there is an embedding h : E → C(K). Let R _h be the polynomial from E into C(K) given by R _h (x) : = h(x) ^m for all ${x \epsilon E}$ . We prove that a polynomial is p-integral (1 ≤ p ≤ + ∞) if and only if it factors through a polynomial of the form R _h followed by the canonical inclusion of C(K) into L _p (K, μ) for some finite measure μ. We also prove that a polynomial P is p-integral if and only if we may write ${P = T \circ R_{h}}$ where T is a p-integral operator on a C(K) space. We show that P is ∞-integral if and only if it factors in the form ${P = T \circ R_{h}}$ where T is a weakly compact operator on a C(K) space. Analogous results are true if we replace C(K) by L _∞ (Ω, μ) for some finite measure space (Ω, Σ, μ). It is proved that a polynomial ${P \epsilon \mathcal{P}(^{m}E, F)}$ is p-integral if and only if its linearization is well defined and p-integral on ${\bigotimes ^{m}_{{\epsilon}_{s}}, s^{E}}$ . It is also shown that a p-integral polynomial may be extended to a p-integral polynomial on every larger space, and the extension has the same p-integral norm. We give a factorization theorem for p-nuclear polynomials. Finally, we prove that a polynomial P is p-nuclear if and only if it may be written in the form ${P = Q \circ A}$ where A is a compact operator and Q is a p-integral polynomial, if and only ${P = Q^{\prime} \circ H}$ with H an Asplund operator and Q′ a p-integral polynomial. This extends a result obtained by C. Cardassi in the linear case.     

Computational Complexity over thep-adic Numbers

A model of computation over thep-adic numbers, for odd primesp, is defined following the approach of Blum, Shub, and Smale. This model employs branching on the property of being a square inQ_pand unit height. The feasibility of systems of quadratic polynomials is shown to be NP-complete in this model. A polynomial time algorithm is given for feasibility of a single quadratic polynomial overQ_p.     

Very degenerate polynomial submersions and counterexamples to the real Jacobian conjecture

Until recently, the only known examples of non-injective polynomial local diffeomorphisms of the plane were the Pinchuk maps discovered in 1994. These maps have the form $(p,q)$, where p is a fixed polynomial of degree 10, and q satisfies certain relation. The lowest possible degree of q in a Pinchuk map is 25. In 2021, with the same p of a Pinchuk map, another example was given with q of degree 15. Aiming to find different examples, with the first components having lower degrees, we look for polynomials of degree less than or equal to 9 sharing some properties with the polynomial p of a Pinchuk map. We find precisely one polynomial of degree 7 and some ones of degree 9. By using one of the polynomials of degree 9 in the first component we construct a non-injective polynomial local diffeomorphism of the plane, with degree 15.     

Galois ring extensions and localized modular rings of invariants of p-groups

We apply recent results on Galois-ring extensions and trace surjective algebras to analyze dehomogenized modular invariant rings of finite p-groups, as well as related localizations. We describe criteria for the dehomogenized invariant ring to be polynomial or at least regular and we show that for regular affine algebras with possibly non-linear action by a p-group, the singular locus of the invariant ring is contained in the variety of the transfer ideal. If V is the regular module of an arbitrary finite p-group, or V is any faithful representation of a cyclic p-group, we show that there is a suitable invariant linear form, inverting which renders the ring of invariants into a “localized polynomial ring” with dehomogenization being a polynomial ring. This is in surprising contrast to the fact that for a faithful representation of a cyclic group of order larger than p, the ring of invariants itself cannot be a polynomial ring by a result of Serre. Our results here generalize observations made by Richman [R] and by Campbell and Chuai [CCH].     

A convex polynomial that is not sos-convex

A multivariate polynomial p(x)?=?p(x ₁, . . . , x _n ) is sos-convex if its Hessian H(x) can be factored as H(x)?= M ^T (x) M(x) with a possibly nonsquare polynomial matrix M(x). It is easy to see that sos-convexity is a sufficient condition for convexity of p(x). Moreover, the problem of deciding sos-convexity of a polynomial can be cast as the feasibility of a semidefinite program, which can be solved efficiently. Motivated by this computational tractability, it is natural to study whether sos-convexity is also a necessary condition for convexity of polynomials. In this paper, we give a negative answer to this question by presenting an explicit example of a trivariate homogeneous polynomial of degree eight that is convex but not sos-convex.     

Improvement to Moreno–Morenoʼs theorems

In this work, we introduce the p-weight degree of a polynomial over a finite field with respect to a subset of the variables. Using this p-weight, we improve the results of Moreno and Moreno for polynomial equations and for exponential sums over finite fields. We prove that our results cannot be improved in general because a family of polynomials where our bounds are attained is provided. Combining our result with a result of Cao and Sun, we give a p-adic improvement to the p-divisibility of general diagonal equations.     

The average errors for Hermite-Fejr interpolation on the Wiener space

For 1≤ p ∞, firstly we prove that for an arbitrary set of distinct nodes in [-1, 1], it is impossible that the errors of the Hermite-Fejr interpolation approximation in L p -norm are weakly equivalent to the corresponding errors of the best polynomial approximation for all continuous functions on [-1, 1]. Secondly, on the ground of probability theory, we discuss the p-average errors of Hermite-Fejr interpolation sequence based on the extended Chebyshev nodes of the second kind on the Wiener space. By our results we know that for 1≤ p ∞ and 2≤ q ∞, the p-average errors of Hermite-Fejr interpolation approximation sequence based on the extended Chebyshev nodes of the second kind are weakly equivalent to the p-average errors of the corresponding best polynomial approximation sequence for L q -norm approximation. In comparison with these results, we discuss the p-average errors of Hermite-Fejr interpolation approximation sequence based on the Chebyshev nodes of the second kind and the p-average errors of the well-known Bernstein polynomial approximation sequence on the Wiener space.     

On the Littlewood cyclotomic polynomials

In this article, we study the cyclotomic polynomials of degree N−1 with coefficients restricted to the set {+1,−1}. By a cyclotomic polynomial we mean any monic polynomial with integer coefficients and all roots of modulus 1. By a careful analysis of the effect of Graeffe's root squaring algorithm on cyclotomic polynomials, P. Borwein and K.K. Choi gave a complete characterization of all cyclotomic polynomials with odd coefficients. They also proved that a polynomial p(x) with coefficients ±1 of even degree N−1 is cyclotomic if and only if p(x)=±Φp₁(±x)Φp₂(±xp₁)?Φpr(±xp₁p₂?pr−1), where N=p₁p₂?pr and the pi are primes, not necessarily distinct. Here is the pth cyclotomic polynomial. Based on substantial computation, they also conjectured that this characterization also holds for polynomials of odd degree with ±1 coefficients. We consider the conjecture for odd degree here. Using Ramanujan's sums, we solve the problem for some special cases. We prove that the conjecture is true for polynomials of degree α²pβ−1 with odd prime p or separable polynomials of any odd degree.     

Semilocal Smoothing Splines

The paper is aimed at periodic and nonperiodic semilocal smoothing splines, or S-splines of class C p, formed by polynomials of degree n. The first p?+?1 coefficients of each polynomial are determined by the values of the preceding polynomial and its first p derivatives at the glue-points, while the remaining n???p coefficients of the higher derivatives of the polynomial are found by the method of least squares. These conditions are supplemented with the initial conditions (nonperiodic case) or the periodicity condition on the spline-function on the segment where it is defined. A linear system of equations is obtained for the coefficients of the polynomials constituting the spline. Its matrix has a block structure. Existence and uniqueness theorems are proved and it is shown that that the convergence of the splines to the original function depends on the eigenvalues of the stability matrix. Examples of stable S-splines are given.     

Bezoutians and projections

With each polynomial p of degree n whose roots lie inside the unit disc we may associate the n-dimensional space of all solutions of the recurrence relation whose coefficients are those of p (considered as a subspace of 1²). The main result consists in establishing a close relation between the Bezoutian of two such polynomials (of the same degree) and the projection operator onto one of the corresponding spaces along the complement of the other. The note forms a loose continuation of the author's investigations of the infinite companion matrix—the generating function of the infinite companion matrix of a polynomial p appears thus as a particular case; the corresponding Bezoutian is that of the pair p and zⁿ.     

Non-Commutative Polynomial Solutions to Partial Differential Equations

This paper extends the notion of a differential equation to the space of polynomials p in non-commutative variables x = (x ₁, . . . , x _g ). The directional derivative D[p, x _i , h] of p in x _i is a polynomial in x and a non-commuting variable h. When all variables commute, D[p, x _i , h] is equal to h?p/?x _i . This paper classifies all non-commutative polynomial solutions to a special class of partial differential equations, including the non-commutative extension of Laplace??s equation. Of interest also are non-commutative subharmonic polynomials. A non-commutative polynomial is subharmonic if its non-commutative Laplacian takes positive-semidefinite matrix values whenever matrices X ₁, . . . , X _g , H are substituted for the variables x ₁, . . . , x _g , h. This paper shows that a homogeneous subharmonic polynomial which is bounded below is a harmonic polynomial??that is, a non-commutative solution to Laplace??s equation??plus a sum of squares of harmonic polynomials.     

Explicit determination of generalized symmetric and alternating Galois groups

This paper shows a probabilistic algorithm to decide whether the Galois group of a given irreducible polynomial with rational coefficients is the generalized symmetric group C_p?S_m or the generalized alternating group C_p?A_m. In the affirmative case, we give generators of the group with their action on the set of roots of the polynomial.