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Crystallography and Riemann surfaces

Cornell Affiliated Author(s)

Author

V. Elser

Abstract

The level set of an elliptic function is a doubly periodic point set in ℂ. To obtain a wider spectrum of point sets, we consider, more generally, a Riemann surface S immersed in ℂ2 and its sections ("cuts") by ℂ. More specifically, we consider surfaces S defined in terms of a fundamental surface element obtained as a conformai map of triangular domains in ℂ. The discrete group of isometries of ℂ2 generated by reflections in the triangle edges leaves S invariant and generalizes double-periodicity. Our main result concerns the special case of maps of right triangles, with the right angle being a regular point of the map. For this class of maps we show that only seven Riemann surfaces, when cut, form point sets that are discrete in ℂ. Their isometry groups all have a rank 4 lattice subgroup, but only three of the corresponding point sets are doubly periodic in ℂ. The remaining surfaces form quasiperiodic point sets closely related to the vertex sets of quasiperiodic tilings. In fact, vertex sets of familiar tilings are recovered in all cases by applying the construction to a piecewise flat approximation of the corresponding Riemann surface. The geometry of point sets formed by cuts of Riemann surfaces is no less "rigid" than the geometry determined by a tiling, and has the distinct advantage in having a regular behavior with respect to the complex parameter which specifies the cut.

Date Published

Journal

Discrete and Computational Geometry

Volume

25

Issue

3

Number of Pages

445-476,

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035635415&doi=10.1007%2fs004540010091&partnerID=40&md5=311b0e0f3afe397b2eba0b1e1d8ccf44

DOI

10.1007/s004540010091

Group (Lab)

Veit Elser Group

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