--- res: bibo_abstract: - We study the extent to which the Hausdorff dimension of a compact subset of an infinite-dimensional Banach space is affected by a typical mapping into a finite-dimensional space. It is possible that the dimension drops under all such mappings, but the amount by which it typically drops is controlled by the ‘thickness exponent’ of the set, which was defined by Hunt and Kaloshin (Nonlinearity12 (1999), 1263–1275). More precisely, let $X$ be a compact subset of a Banach space $B$ with thickness exponent $\tau$ and Hausdorff dimension $d$. Let $M$ be any subspace of the (locally) Lipschitz functions from $B$ to $\mathbb{R}^{m}$ that contains the space of bounded linear functions. We prove that for almost every (in the sense of prevalence) function $f \in M$, the Hausdorff dimension of $f(X)$ is at least $\min\{ m, d / (1 + \tau) \}$. We also prove an analogous result for a certain part of the dimension spectra of Borel probability measures supported on $X$. The factor $1 / (1 + \tau)$ can be improved to $1 / (1 + \tau / 2)$ if $B$ is a Hilbert space. Since dimension cannot increase under a (locally) Lipschitz function, these theorems become dimension preservation results when $\tau = 0$. We conjecture that many of the attractors associated with the evolution equations of mathematical physics have thickness exponent zero. We also discuss the sharpness of our results in the case $\tau > 0$.@eng bibo_authorlist: - foaf_Person: foaf_givenName: WILLIAM foaf_name: OTT, WILLIAM foaf_surname: OTT - foaf_Person: foaf_givenName: BRIAN foaf_name: HUNT, BRIAN foaf_surname: HUNT - foaf_Person: foaf_givenName: Vadim foaf_name: Kaloshin, Vadim foaf_surname: Kaloshin foaf_workInfoHomepage: http://www.librecat.org/personId=FE553552-CDE8-11E9-B324-C0EBE5697425 orcid: 0000-0002-6051-2628 bibo_doi: 10.1017/s0143385705000714 bibo_issue: '3' bibo_volume: 26 dct_date: 2006^xs_gYear dct_isPartOf: - http://id.crossref.org/issn/0143-3857 - http://id.crossref.org/issn/1469-4417 dct_language: eng dct_publisher: Cambridge University Press@ dct_title: The effect of projections on fractal sets and measures in Banach spaces@ ...