Volume 115, Issue 2
May 2005, pages 117-240
pp 117-126
Irreducibility Results for Compositions of Polynomials in Several Variables
Anca Iuliana Bonciocat Alexandru Zaharescu
We obtain explicit upper bounds for the number of irreducible factors for a class of compositions of polynomials in several variables over a given field. In particular, some irreducibility criteria are given for this class of compositions of polynomials.
pp 127-146
On Harder–Narasimhan Reductions for Higgs Principal Bundles
The existence and uniqueness of 𝐻–𝑁 reduction for the Higgs principal bundles over nonsingular projective variety is shown. We also extend the notion of 𝐻–𝑁 reduction for (𝛤, 𝐺)-bundles and ramified 𝐺-bundles over a smooth curve.
pp 147-165
Twisted Vector Bundles on Pointed Nodal Curves
Motivated by the quest for a good compactification of the moduli space of 𝐺-bundles on a nodal curve we establish a striking relationship between Abramovich’s and Vistoli’s twisted bundles and Gieseker vector bundles.
pp 167-190
Some BMO Estimates for Vector-Valued Multilinear Singular Integral Operators
In this paper, we prove some BMO end-point estimates for some vector-valued multilinear operators related to certain singular integral operators.
pp 191-200
$L^p$-Continuity for Calderón–Zygmund Operator
Given a Calderón–Zygmund (𝐶-𝑍 for short) operator 𝑇, which satisfies Hörmander condition, we prove that: if 𝑇 maps all the characteristic atoms to $W L^1$, then 𝑇 is continuous from $L^p$ to $L^p(1 < p < ∞)$. So the study of strong continuity on arbitrary function in $L^p$ has been changed into the study of weak continuity on characteristic functions.
pp 201-207
A Note on Convex Renorming and Fragmentability
Using the game approach to fragmentability, we give new and simpler proofs of the following known results: (a) If the Banach space admits an equivalent Kadec norm, then its weak topology is fragmented by a metric which is stronger than the norm topology. (b) If the Banach space admits an equivalent rotund norm, then its weak topology is fragmented by a metric. (c) If the Banach space is weakly locally uniformly rotund, then its weak topology is fragmented by a metric which is stronger than the norm topology.
pp 209-216
Some Necessary and Sufficient Conditions for Hypercyclicity Criterion
We give necessary and sufficient conditions for an operator on a separable Hilbert space to satisfy the hypercyclicity criterion.
pp 217-226
New Criteria to Identify Spectrum
In this paper we give some new criteria for identifying the components of a probability measure, in its Lebesgue decomposition. This enables us to give new criteria to identify spectral types of self-adjoint operators on Hilbert spaces, especially those of interest.
pp 227-240
The Contact Angle in Inviscid Fluid Mechanics
We show that in general, the specification of a contact angle condition at the contact line in inviscid fluid motions is incompatible with the classical field equations and boundary conditions generally applicable to them. The limited conditions under which such a specification is permissible are derived;however, these include cases where the static meniscus is not flat. In view of this situation, the status of the many `solutions’ in the literature which prescribe a contact angle in potential flows comes into question. We suggest that these solutions which attempt to incorporate a phenomenological, but incompatible, condition are in some, imprecise sense `weak-type solutions’;they satisfy or are likely to satisfy, at least in the limit, the governing equations and boundary conditions everywhere except in the neighbourhood of the contact line. We discuss the implications of the result for the analysis of inviscid flows with free surfaces.
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