Abstract
Let \(\Lambda \) be the unit tangent bundle of the unit 3-sphere acted on transitively by the contact group of Lie sphere transformations. We study the Lie sphere geometry of generic curves in \(\Lambda \) which are everywhere transversal to the contact distribution of \(\Lambda \). By the method of moving frames, we prove that such curves can be parametrized by a Lie-invariant parameter, the Lie arclength, and that in this parametrization they are uniquely determined, up to Lie sphere transformation, by four local invariants, the Lie curvatures. We then consider the simplest Lie-invariant functional on generic transversal curves defined by integrating the differential of the Lie arclength. The corresponding Euler–Lagrange equations are computed and the critical curves are characterized in terms of their Lie curvatures. In our discussion, we adopt Griffiths’ exterior differential systems approach to the calculus of variations.
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References
Barut, A.O., Zeni, J.R., Laufer, A.: The exponential map for the conformal group \({\rm O}(2,4)\). J. Phys. A 27(15), 5239 (1994)
Blaschke, W.: Vorlesungen über Differentialgeometrie. III: Differentialgeometrie der Kreise und Kugeln, Grundlehren der mathematischen Wissenschaften, 29, Springer, Berlin, (1929)
Bryant, R.L.: On notions of equivalence of variational problems with one independent variable. Contemp. Math. 68, 65–76 (1987)
Bryant, R.L., Chern, S.S., Gardner, R.B., Goldschmidt, H.L., Griffiths, P.A.: Exterior differential systems. Springer-Verlag, New York (1991)
Bryant, R.L., Griffiths, P.A.: Reduction for constrained variational problems and \(\int {{\frac{k^2}{2}}}\). Amer. J. Math. 108, 525–570 (1986)
Bryant, R. L., Gardner, R. B.: Control structures. Geometry in nonlinear control and differential inclusions (Warsaw, 1993), 111–121. Banach Center Publ., 32, Polish Academy of Sciences, Institute of Mathematics, Warsaw, (1995)
Burstall, F., Hertrich-Jeromin, U.: Harmonic maps in unfashionable geometries. Manuscripta Math. 108, 171–189 (2002)
Burstall, F., Hertrich-Jeromin, U., Pember, M., Rossman, W.: Polynomial conserved quantities of lie applicable surfaces. Manuscripta Math. 158(3–4), 505–546 (2019)
Calini, A., Ivey, T.: Integrable geometric flows for curves in pseudoconformal \(S^3\), J. Geom. Phys. 166 (2021), Paper No. 104249, 17 pp
Cecil, T.E., Chern, S.S.: Tautness and Lie sphere geometry. Math. Ann. 278, 381–399 (1987)
Cecil, T.E., Chern, S.S.: Dupin submanifolds in Lie sphere geometry, Proceedings Tianjin 1986–87. Lecture Notes in Mathematics, vol. 1369. Springer, New York (1989)
Cecil, T.E.: Lie sphere geometry: with applications to submanifolds. Springer-Verlag, New York (1992)
Cecil, T.E., Jensen, G.R.: Dupin hypersurfaces with three principal curvatures. Invent. Math. 132, 121–178 (1998)
Cecil, T.E., Jensen, G.R.: Dupin hypersurfaces with four principal curvatures. Geometriae Ded. 79, 1–49 (2000)
Dzhalilov, A., Musso, E., Nicolodi, L.: Conformal geometry of timelike curves in the (1+2)-Einstein universe. Nonlinear Anal. 143, 224–255 (2016)
Eshkobilov, O., Musso, E., Nicolodi, L.: The geometry of conformal timelike geodesics in the Einstein universe J. Math. Anal. Appl. 495 (2021), no. 2, Paper No. 124730, 32 pp
Ferapontov, E.: Lie sphere geometry and integrable systems. Tohoku Math. J. (2) 52, 199–233 (2000)
Ferrández, A., Giménez, A., Lucas, P.: Geometrical particle models on 3d null curves. Phys. Lett. B 543, 311–317 (2002)
Grant, J.D., Musso, E.: Coisotropic variational problems. J. Geom. Phys. 50, 303–338 (2004)
Griffiths, P.A.: Exterior differential systems and the calculus of variations, Progress in Mathematics, 25. Birkhäuser, Boston (1982)
Hsu, L.: Calculus of variations via the Griffiths formalism. J. Differential Geom. 36, 551–589 (1992)
Ivey, T. A., Landsberg, J. M.: Cartan for beginners, Grad. Stud. Math., 175, American Mathematical Society, Providence, RI, (2016)
Jensen, G. R., Musso, E., Nicolodi, L.: The geometric Cauchy problem for the membrane shape equation, J. Phys. A 47 (2014), no. 49, 495201, 22 pp
Jensen, G.R., Musso, E., Nicolodi, L.: Surfaces in Classical Geometries. Universitext, Springer, Cham, A Treatment by Moving Frames (2016)
Lie, S.: Über Komplexe, insbesondere Linien-und Kugelkomplexe, mit Anwendung auf der Theorie der partieller Differentialgleichungen. Math. Ann. 5(145–208), 209–256 (1872)
Lie, S., Scheffers, G.: Geometrie der Berührungstransformationen. Teubner, Leipzig (1896)
Miyaoka, R.: Dupin hypersurfaces and a a Lie invariant. Kodai Math. J. 12(2), 228–256 (1989)
Miyaoka, R.: Lie contact structures and normal Cartan connections. Kodai Math. J. 14(1), 13–41 (1991)
Musso, E.: The conformal arclength functional. Math. Nachr. 165, 107–131 (1994)
Musso, E., Nicolodi, L.: On the Cauchy problem for the integrable system of Lie minimal surfaces. J. Math. Phys. 46(11), 3509–3523 (2005)
Musso, E., Nicolodi, L.: Deformation and applicability of surfaces in Lie sphere geometry. Tohoku Math. J. (2) 58(2), 161–187 (2006)
Musso, E., Nicolodi, L.: Closed trajectories of a particle model on null curves in anti-de Sitter 3-space. Classical Quantum Gravity 24(22), 5401–5411 (2007)
Musso, E., Nicolodi, L.: Reduction for constrained variational problems on 3-dimensional null curves. SIAM J. Control. Optim. 47(3), 1399–1414 (2008)
Musso, E., Nicolodi, L.: Quantization of the conformal arclength functional on space curves. Comm. Anal. Geom. 25(1), 209–242 (2017)
Musso, E., Nicolodi, L., Salis, F.: On the Cauchy-Riemann geometry of transversal curves in the 3-sphere. Zh. Mat. Fiz. Anal. Geom. 16(3), 312–363 (2020)
Musso, E., Nicolodi, L.: On the total CR twist of transversal curves in the 3-sphere, SIGMA Symmetry Integrability Geom. Methods Appl. 19 (2023), Paper No. 101, 36 pp
Musso, E., Salis, F.: The Cauchy-Riemann strain functional for Legendrian curves in the 3-sphere. Ann. Mat. Pura Appl. (4) 199, 2395–2434 (2020)
Pember, M.: Lie applicable surfaces. Comm. Anal. Geom. 28(6), 1407–1450 (2020)
Pinkall, U.: Dupin hypersurfaces. Math. Ann. 270, 427–440 (1985)
Sato, H., Yamaguchi, K.: Lie contact manifolds, in Geometry of Manifolds (edited by K. Shiohama), 191–238. Perspect. Math., 8, Academic Press, Inc., Boston, MA, (1989)
Sato, H., Yamaguchi, K.: Lie contact manifolds II. Math. Ann. 297(1), 33–57 (1993)
Ulrych, S.: Lie sphere geometry in nuclear scattering processes, J. Math. Anal. Appl. 491 (2020), no. 2, 124324, 11 pp
Acknowledgements
The author gratefully acknowledges valuable input by Emilio Musso. This work was partially supported by PRIN 2017 and 2022 “Real and Complex Manifolds: Topology, Geometry and Holomorphic Dynamics" (protocolli 2017JZ2SW5-004 and 2022AP8HZ9-003); and by GNSAGA of INdAM. The author would like to thank the referee for his comments and suggestions.
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In memory of Professor Lieven Vanhecke (1939-2023).
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Nicolodi, L. On a variational problem for curves in Lie sphere geometry. Ann Glob Anal Geom 68, 18 (2025). https://doi.org/10.1007/s10455-025-10021-4
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DOI: https://doi.org/10.1007/s10455-025-10021-4
Keywords
- Curves in Lie sphere geometry
- Lie sphere invariants
- Linear control systems
- Geometric variational problems
- Griffiths’ formalism
- Exterior differential systems