Lipschitz extensions of definable p-adic functions

In this paper, we prove a definable version of Kirszbraun's theorem in a non-Archimedean setting for definable families of functions in one variable. More precisely, we prove that every definable function $f : X \times Y \to \mathbb{Q}_p^s$, where $X\subset \mathbb{Q}_p$ and $Y \subset \mathbb{Q}_p^r$, that is $\lambda$-Lipschitz in the first variable, extends to a definable function $\tilde{f}:\mathbb{Q}_p\times Y \to \mathbb{Q}_p^s$ that is $\lambda$-Lipschitz in the first variable.Comment: 11 page

Micromachined Capacitive Long-Range Displacement Sensor for Nano-Positioning of Microactuator systems

This thesis is about a “Micromachined capacitive long-range displacement sensor for nano-positioning of microactuator systems”. Possible applications of such microsystems are found in future probe-based datastorage, scanning probe microscopy, microbiology, optical lens manipulation, microgrippers and microrobots, etc. These applications require positioning with nanometer precision over a long range (ten’s of micrometers) and benefit from further miniaturization and the application of sub-mm sized Micro Electro Mechanical Systems (MEMS). In many cases open-loop operation is not sufficient and a form of system control is required to combine nanometer accuracy with a large dynamic range and to obtain better system performance. In order to make such systems both economically viable as well as compact, on-chip position sensing appears to be a requirement. The aim is therefore, to obtain optimal performance through an integration of sensor and actuator with micromachining fabrication technology without additional micro assembly

Some fragments of second-order logic over the reals for which satisfiability and equivalence are (un)decidable

We consider the Σ1 0-fragment of second-order logic over the vocabulary h+, ×, 0, 1, <, S1, ..., Ski, interpreted over the reals, where the predicate symbols Si are interpreted as semi-algebraic sets. We show that, in this context, satisfiability of formulas is decidable for the first-order ∃ ∗ - quantifier fragment and undecidable for the ∃ ∗∀- and ∀ ∗ -fragments. We also show that for these three fragments the same (un)decidability results hold for containment and equivalence of formulas.Fil: Grimson, Rafael. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kuijpers, Bart. Hasselt University; Bélgic

Evaluating geometric queries using few arithmetic operations

Let \cp:=(P_1,...,P_s) be a given family of $n$-variate polynomials with integer coefficients and suppose that the degrees and logarithmic heights of these polynomials are bounded by $d$ and $h$, respectively. Suppose furthermore that for each $1\leq i\leq s$ the polynomial $P_i$ can be evaluated using $L$ arithmetic operations (additions, subtractions, multiplications and the constants 0 and 1). Assume that the family \cp is in a suitable sense \emph{generic}. We construct a database $\cal D$, supported by an algebraic computation tree, such that for each $x\in [0,1]^n$ the query for the signs of $P_1(x),...,P_s(x)$ can be answered using h d^{\cO(n^2)} comparisons and $nL$ arithmetic operations between real numbers. The arithmetic-geometric tools developed for the construction of $\cal D$ are then employed to exhibit example classes of systems of $n$ polynomial equations in $n$ unknowns whose consistency may be checked using only few arithmetic operations, admitting however an exponential number of comparisons