Surfaces that are covered by two pencils of circles

Niels Lubbes

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


We list up to Möbius equivalence all possible degrees and embedding dimensions of real surfaces that are covered by at least two pencils of circles, together with the number of such pencils. In addition, we classify incidences between the contained circles, complex lines and isolated singularities. Such geometric characteristics are encoded in the Néron–Severi lattices of such surfaces and is of potential interest to geometric modelers and architects. As an application we confirm Blum’s conjecture in higher dimensional space and we address the Blaschke–Bol problem by classifying surfaces that are covered by hexagonal webs of circles. In particular, we find new examples of such webs that cannot be embedded in 3-dimensional space.
Original languageEnglish (US)
Pages (from-to)1445-1472
Number of pages28
JournalMathematische Zeitschrift
Issue number3-4
StatePublished - Mar 22 2021
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-06-07
Acknowledgements: I would like to thank R. Krasauskas, H. Pottmann, J. Schicho, M. Skopenkov and S. Zub.e for the inspiring discussions, which have have been invaluable for this paper. In particular, the detailed comments of M. Skopenkov were extremely helpful. I thank J. Kollar for interesting historical remarks. The computations were done using [37, Sage] and [7, Magma]. The images were made using [29, Povray]. This research was supported by base funding of the King Abdullah University of Science and Technology (KAUST) and by the Austrian Science Fund (FWF) project P33003.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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