477,524 research outputs found
Global time estimates for solutions to equations of dissipative type
Global time estimates of Lp-Lq norms of solutions to general strictly
hyperbolic partial differential equations are considered. The case of special
interest in this paper are equations exhibiting the dissipative behaviour.
Results are applied to discuss time decay estimates for Fokker-Planck equations
and for wave type equations with negative mass.Comment: Journees "Equations aux Derivees Partielles
Degenerate neckpinches in Ricci flow
In earlier work, we derived formal matched asymptotic profiles for families
of Ricci flow solutions developing Type-II degenerate neckpinches. In the
present work, we prove that there do exist Ricci flow solutions that develop
singularities modeled on each such profile. In particular, we show that for
each positive integer , there exist compact solutions in all dimensions
that become singular at the rate (T-t)^{-2+2/k}$
Structural Induction Principles for Functional Programmers
User defined recursive types are a fundamental feature of modern functional
programming languages like Haskell, Clean, and the ML family of languages.
Properties of programs defined by recursion on the structure of recursive types
are generally proved by structural induction on the type. It is well known in
the theorem proving community how to generate structural induction principles
from data type declarations. These methods deserve to be better know in the
functional programming community. Existing functional programming textbooks
gloss over this material. And yet, if functional programmers do not know how to
write down the structural induction principle for a new type - how are they
supposed to reason about it? In this paper we describe an algorithm to generate
structural induction principles from data type declarations. We also discuss
how these methods are taught in the functional programming course at the
University of Wyoming. A Haskell implementation of the algorithm is included in
an appendix.Comment: In Proceedings TFPIE 2013, arXiv:1312.221
Fourier restriction to polynomial curves I: a geometric inequality
We prove a Fourier restriction result for general polynomial curves in Rd. Measuring the Fourier restriction with respect to the affine arclength measure of the curve, we obtain a universal estimate for the class of all polynomial curves of bounded degree. Our method relies on establishing a geometric inequality for general polynomial curves which is of interest in its own right. Applications of this geometric inequality to other problems in euclidean harmonic analysis have recently been established
improving bounds for averages along curves
We establish local mapping properties for averages on curves. The
exponents are sharp except for endpoints.Comment: 37 pages, simplified argument (no further need for algebraic
complexity theory!), to appear, JAM
Discrete Approximations of Metric Measure Spaces of Controlled Geometry
We find a necessary and sufficient condition for a doubling metric space to
carry a (1,p)-Poincare inequality. The condition involves discretizations of
the metric space and Poincare inequalities on graphs.Comment: 23 Page
- …