We prove a sharp Hölder estimate for solutions of linear two-dimensional, divergence form elliptic equations with measurable coefficients, such that the matrix of the coefficients is symmetric and has unit determinant. Our result extends some previous work by Piccinini and Spagnolo [7]. The proof relies on a sharp Wirtinger type inequality.

We show that the Wirtinger presentation of a prime alternating link group satisfies a generalized small cancellation condition. This gives a simplification of Weinbaum’s solution to the word and conjugacy problems for these groups, which extends to finite sums of alternating links.

Abstract—In this paper, reliable consensus of multi-agent systems with sampled-data is investigated. By using a suitable Lyapunov-Krasovskii functional and some techniques such as Wirtinger Inequality, Schur Complement and Kronecker Product, the results of such system are obtained by solving a set of Linear Matrix Inequalities (LMIs). One numerical example is included to show the effectiveness ...

A classical link in 3-space can be represented by a Gauss paragraph encoding a link diagram in a combinatorial way. A Gauss paragraph may code not a classical link diagram, but a diagram with virtual crossings. We present a criterion and a linear algorithm detecting whether a Gauss paragraph encodes a classical link. We describe Wirtinger presentations realizable by virtual link groups.

A sharp version of a recent inequality Kovalev and Yang on the ratio $(H^1)^\ast$ $H^4$ norms for certain polynomials is obtained. The applied to establish tractable sufficient condition Wirtinger derivatives at origin harmonic self-maps unit disc which fix origin.