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image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Aequationes Mathemat...arrow_drop_down
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
Aequationes Mathematicae
Article . 1974 . Peer-reviewed
License: Springer TDM
Data sources: Crossref
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
Aequationes Mathematicae
Article . 1972 . Peer-reviewed
License: Springer TDM
Data sources: Crossref
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
zbMATH Open
Article . 1974
Data sources: zbMATH Open
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Very slowly varying functions

Authors: Erdös, P.; Ash, J. Marshall; Rubel, L.A.;

Very slowly varying functions

Abstract

Let \(\varphi\) be a positive non-decreasing real valued function defined on \([0, \infty)\), and let \(f\) be any real valued function defined on \([0, \infty)\). We say that \(f\) is \(\varphi\)-slowly varying if \(\varphi (x)[f(x+ \alpha)-f(x)] \to 0\) as \(x \to \infty\) for each \(\alpha\). We say that \(f\) is uniformly \(\varphi\)-slowly varying if \(\sup \{\varphi (x) |f(x+ \alpha)-f(x)|: \alpha \in I \} \to 0\) as \(x \to \infty\) for every bounded interval \(I\). We state here five theorems that will be proved later in a longer communication. We also pose one question that seems to be difficult. Theorem 1. If \(f\) is \(\varphi\)-slowly varying and if \(\sum i/ \varphi (n)< \infty\), then \(f\) tends to a finite or infinite limit at \(\infty\). Theorem 2. If \(f\) is \(\varphi\)-slowly varying and measurable, then \(f\) is uniformly \(\varphi\)-slowly vayring. Theorem 3. Let \(f\) be \(\varphi\)-slowly varying and let \(\beta (x)= \sum ^\infty_{j=0} 1/ \varphi (x+j)\). If \(\varphi (x) \beta (x)\) is bounded, then \(f\) must be uniformly \(\varphi\)-slowly varying. Theorem 4. Suppose that \(\sum 1/ \varphi (n)< \infty\) and that \(\varphi (x+1)/ \varphi (x) \to 1\) as \(x \to \infty\). Then there exists a function \(f\) that is \(\varphi\)-slowly varying but not uniformly \(\varphi\)-slowly varying. Theorem 5. Let \(\beta (x)\) be the function of Theorem 4, and suppose that \(\varphi (x) \beta (x)\) is unbounded, but that \(\varphi (x) \beta (x)=o(x)\) as \(x \to \infty\). Then there exists a function \(f\) that is \(\varphi\)-slowly varying but not uniformly \(\varphi\)-slowly varying. Question. Does there exist a function \(f\) such that \(x[f(x+ \alpha)-f(x)] \to 0\) as \(x \to \infty\) for each \(\alpha\) but \(\sup \{|f(x+ \alpha)-f(x)|: \alpha \in [0,1] \} \nrightarrow 0\) as \(x \to \infty\)?

Country
Germany
Keywords

510.mathematics, Rate of growth of functions, orders of infinity, slowly varying functions, Article

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
13
Average
Top 10%
Average
Green