Abstract
We propose an answer to a question raised by F. Burstall: Is there any interesting theory of isothermic submanifolds of ℝn of dimension greater than two? We call an n-immersion f(x) in ℝm isothermic k if the normal bundle of f is flat and x is a line of curvature coordinate system such that its induced metric is of the form \(\sum_{i=1}^{n} g_{ii}\,\mathrm{d} x_{i}^{2}\) with \(\sum_{i=1}^{n} \epsilon_{i} g_{ii}=0\), where ε i =1 for 1≤i≤n−k and ε i =−1 for n−k<i≤n. A smooth map (f 1,…,f n ) from an open subset \({\mathcal{O}}\) of ℝn to the space of m×n matrices is called an n-tuple of isothermic k n-submanifolds in ℝm if each f i is an isothermic k immersion, \((f_{i})_{x_{j}}\) is parallel to \((f_{1})_{x_{j}}\) for all 1≤i,j≤n, and there exists an orthonormal frame (e 1,…,e n ) and a GL(n)-valued map (a ij ) such that \(\mathrm{d}f_{i}= \sum_{j=1}^{n} a_{ij} e_{j}\,\mathrm {d} x_{j}\) for 1≤i≤n. Isothermic1 surfaces in ℝ3 are the classical isothermic surfaces in ℝ3. Isothermic k submanifolds in ℝm are invariant under conformal transformations. We show that the equation for n-tuples of isothermic k n-submanifolds in ℝm is the \(\frac{O(m+n-k,k)}{O(m)\times O(n-k,k)}\)-system, which is an integrable system. Methods from soliton theory can therefore be used to construct Christoffel, Ribaucour, and Lie transforms, and to describe the moduli spaces of these geometric objects and their loop group symmetries.
Similar content being viewed by others
References
Brück, M., Du, X., Park, J., Terng, C.L.: The submanifold geometries associated to Grassmannian systems. Mem. Am. Math. Soc. 155, 735 (2002)
Burstall, F.E.: Isothermic surfaces, conformal geometry, Clifford algebras and integrable systems. In: Integrable Systems, Geometry, and Topology. AMS/IP Stud. Adv. Math., vol. 36, pp. 1–82. (2006)
Cieśliński, J.: The Darboux-Bianchi transformation for isothermic surfaces. Differ. Geom. Appl. 7, 1–28 (1997)
Cieśliński, J., Goldstein, P., Sym, A.: Isothermic surfaces in E 3 as soliton surfaces. Phys. Lett. A 205, 37–43 (1995)
Dajczer, M., Tojeiro, R.: An extension of the classical Ribaucour transformation. Proc. Lond. Math. Soc. 85, 211–232 (2002)
Hertrich-Jeromin, U., Pedit, F.: Remarks on the Darboux transform of isothermic surfaces. Doc. Math. 2, 313–333 (1997)
Schief, W.K., Konopelchenko, B.G.: On the unification of classical and novel integrable surfaces. I. Differential geometry. Proc. R. Soc., Math. Phys. Eng. Sci. 459, 67–84 (2003)
Terng, C.L.: Soliton equations and differential geometry. J. Differ. Geom. 45, 407–445 (1997)
Terng, C.L., Uhlenbeck, K.: Bäcklund transformations and loop group actions. Commun. Pure Appl. Math. 53, 1–75 (2000)
Terng, C.L., Wang, E.: Curved flats, exterior differential systems, and conservation laws. In: Complex, Contact and Symmetric Manifolds. Progr. Math., vol. 234, pp. 235–254 (2005)
Tojeiro, R.: Isothermic submanifolds of Euclidean space. J. Reine Angew. Math. 598, 1–24 (2006)
Author information
Authors and Affiliations
Corresponding author
Additional information
Research of N. Donaldson was supported in part by NSF Advance Grant to UCI.
Research of C.-L. Terng was supported in part by NSF Grant DMS-0707132.
Rights and permissions
About this article
Cite this article
Donaldson, N., Terng, CL. Isothermic Submanifolds. J Geom Anal 22, 827–844 (2012). https://doi.org/10.1007/s12220-011-9216-x
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12220-011-9216-x