A note about Khoshnevisan--Xiao conjecture

Khoshnevisan and Xiao showed in [Ann. Probab. 33 (2005) 841--878] that the statement about almost surely vanishing Bessel--Riesz capacity of the image of a Borel set $G\subset\mathbb{R}_+$ under a symmetric L\'{e}vy process $X$ in $\mathbb{R}^d$ is equivalent to the vanishing of a deterministic $f$-capacity for a particular function $f$ defined in terms of the characteristic exponent of $X$. The authors conjectured that a similar statement is true for all L\'{e}vy processes in $\mathbb{R}^d$. We show that the conjecture is true provided we extend the definition of $f$ and require certain integrability conditions which cannot be avoided in general.Comment: Published at http://dx.doi.org/10.1214/009117906000000197 in the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org

H\"older-differentiability of Gibbs distribution functions

In this paper we give non-trivial applications of the thermodynamic formalism to the theory of distribution functions of Gibbs measures (devil's staircases) supported on limit sets of finitely generated conformal iterated function systems in $\R$. For a large class of these Gibbs states we determine the Hausdorff dimension of the set of points at which the distribution function of these measures is not $\alpha$-H\"older-differentiable. The obtained results give significant extensions of recent work by Darst, Dekking, Falconer, Li, Morris, and Xiao. In particular, our results clearly show that the results of these authors have their natural home within thermodynamic formalism.Comment: 13 pages, 2 figure

Fractal properties of the random string processes

Let $\{u_t(x),t\ge 0, x\in {\mathbb{R}}\}$ be a random string taking values in ${\mathbb{R}}^d$, specified by the following stochastic partial differential equation [Funaki (1983)]: $$\frac{\partial u_t(x)}{\partial t}=\frac{{\partial}^2u_t(x)}{\partial x^2}+\dot{W},$$ where $\dot{W}(x,t)$ is an ${\mathbb{R}}^d$-valued space-time white noise. Mueller and Tribe (2002) have proved necessary and sufficient conditions for the ${\mathbb{R}}^d$-valued process $\{u_t(x):t\ge 0, x\in {\mathbb{R}}\}$ to hit points and to have double points. In this paper, we continue their research by determining the Hausdorff and packing dimensions of the level sets and the sets of double times of the random string process $\{u_t(x):t\ge 0, x\in {\mathbb{R}}\}$. We also consider the Hausdorff and packing dimensions of the range and graph of the string.Comment: Published at http://dx.doi.org/10.1214/074921706000000806 in the IMS Lecture Notes Monograph Series (http://www.imstat.org/publications/lecnotes.htm) by the Institute of Mathematical Statistics (http://www.imstat.org

Comment on 'Note on the dog-and-rabbit chase problem in introductory kinematics'

We comment on the recent paper by Yuan Qing-Xin and Du Yin-Xiao (Eur. J. Phys. 29 (2008) N43-N45).Comment: 2 pages, no figure

Touching artefacts in an ancient world on a browser-based platform

Title: Touching artefacts in an ancient world on a browser-based platform Article & version: Published version Original citation & hyperlink: Arnab, S., Petridis, P., Dunwell, I. and de Freitas, S. (2010). Touching artefacts in an ancient world on a browser-based platform. In Y. Xiao, T. Amon & R. Muffolett