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Journal of the Ramanujan Mathematical Society

Volume 38, Issue 3, September 2023  pp. 225–236.

Finite Decomposition of Minimal surfaces, Maximal surfaces, Time-like Minimal surfaces and Born-Infeld solitons

Authors:  Rukmini Dey, Kohinoor Ghosh and Sidharth Soundararajan
Author institution: I.C.T.S.-T.I.F.R., Bangalore.

Summary:  This paper deals with decomposition of height functions of various zero-mean curvature surfaces into a finite sum of scaled and translated versions of themselves. There are various ways of accomplishing this. We show that the height function of Scherk's second surface decomposes into a finite sum of scaled and translated versions of itself, using an Euler Ramanujan identity. A similar result appears in R. Kamien's work on liquid crystals where he shows (using an Euler-Ramanujan identity) that the Scherk's first surface decomposes into a finite sum of scaled and translated versions of itself. We give another finite decomposition of the height function of the Scherk's first surface in terms of translated helicoids and scaled and translated Scherk's first surface. We give some more examples, for instance a (complex) maximal surface and a (complex) BI soliton. We then show, using the Weierstrass-Enneper representation of minimal (maximal) surfaces, that one can decompose the height function of a minimal (maximal) surface into finite sums of height functions of surfaces which, upon change of coordinates, turn out to be minimal (maximal) surfaces. We then exhibit a general property of minimal surfaces, maximal surfaces, timelike minimal surfaces and Born-Infeld soliton surfaces that their local height functions z = Z(x,y) split into finite sum of scaled and translated versions of functions of the same form. Upto scaling these new functions are height functions of the minimal surfaces, maximal surfaces, timelike minimal surfaces and Born-Infeld soliton surfaces respectively. Lastly, we exhibit a foliation of ℝ³ minus certain lines by shifted helicoids (which appear in one of the Euler-Ramanujan identities).


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