From curves to currents

Many natural real-valued functions of closed curves are known to extend continuously to the larger space of geodesic currents. For instance, the extension of length with respect to a fixed hyperbolic metric was a motivating example for the development of geodesic currents. We give a simple criterion...

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Main Authors: Dídac Martínez-Granado, Dylan P. Thurston
Format: Article
Language:English
Published: Cambridge University Press 2021-01-01
Series:Forum of Mathematics, Sigma
Subjects:
Online Access:https://www.cambridge.org/core/product/identifier/S2050509421000682/type/journal_article
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author Dídac Martínez-Granado
Dylan P. Thurston
author_facet Dídac Martínez-Granado
Dylan P. Thurston
author_sort Dídac Martínez-Granado
collection DOAJ
description Many natural real-valued functions of closed curves are known to extend continuously to the larger space of geodesic currents. For instance, the extension of length with respect to a fixed hyperbolic metric was a motivating example for the development of geodesic currents. We give a simple criterion on a curve function that guarantees a continuous extension to geodesic currents. The main condition of our criterion is the smoothing property, which has played a role in the study of systoles of translation lengths for Anosov representations. It is easy to see that our criterion is satisfied for almost all known examples of continuous functions on geodesic currents, such as nonpositively curved lengths or stable lengths for surface groups, while also applying to new examples like extremal length. We use this extension to obtain a new curve counting result for extremal length.
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spelling doaj.art-db814d14d3694cc98a5a6142342d21922023-03-09T12:34:52ZengCambridge University PressForum of Mathematics, Sigma2050-50942021-01-01910.1017/fms.2021.68From curves to currentsDídac Martínez-Granado0https://orcid.org/0000-0002-1692-2144Dylan P. Thurston1https://orcid.org/0000-0003-4610-9792Department of Mathematics, University of California, Davis, One Shields Ave, Davis, 95616, USA; E-mail:Department of Mathematics, Indiana University, 831 East 3rd St., Bloomington, 47405, USA; E-mail:Many natural real-valued functions of closed curves are known to extend continuously to the larger space of geodesic currents. For instance, the extension of length with respect to a fixed hyperbolic metric was a motivating example for the development of geodesic currents. We give a simple criterion on a curve function that guarantees a continuous extension to geodesic currents. The main condition of our criterion is the smoothing property, which has played a role in the study of systoles of translation lengths for Anosov representations. It is easy to see that our criterion is satisfied for almost all known examples of continuous functions on geodesic currents, such as nonpositively curved lengths or stable lengths for surface groups, while also applying to new examples like extremal length. We use this extension to obtain a new curve counting result for extremal length.https://www.cambridge.org/core/product/identifier/S2050509421000682/type/journal_articlegeodesic currentsextremal lengthcurve counting57M5037E30
spellingShingle Dídac Martínez-Granado
Dylan P. Thurston
From curves to currents
Forum of Mathematics, Sigma
geodesic currents
extremal length
curve counting
57M50
37E30
title From curves to currents
title_full From curves to currents
title_fullStr From curves to currents
title_full_unstemmed From curves to currents
title_short From curves to currents
title_sort from curves to currents
topic geodesic currents
extremal length
curve counting
57M50
37E30
url https://www.cambridge.org/core/product/identifier/S2050509421000682/type/journal_article
work_keys_str_mv AT didacmartinezgranado fromcurvestocurrents
AT dylanpthurston fromcurvestocurrents