Abstract
In this paper, we introduce the theory of equivariant functions by studying their analytic, geometric and algebraic properties. We also determine the necessary and sufficient conditions under which an equivariant form arises from modular forms. This study was motivated by observing examples of functions for which the Schwarzian derivative is a modular form on a discrete group. We also investigate the Fourier expansions of normalized equivariant functions, and a strong emphasis is made on the connections to elliptic functions and their integrals.
Similar content being viewed by others
References
Abramowitz M., Stegun I.A.: Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. Dover, New York (1972)
Baker A.: On the Periods of the Weierstrass \({{\wp}}\) -Function Symposia Mathematica, vol. IV (INDAM, Rome, 1968/69), pp. 155–174. Academic Press, New York (1970)
Berndt B.C., Bialek P.R.: On the power series coefficients of certain quotients of Eisenstein series. Trans. Am. Math. Soc. 357, 4379–4412 (2005)
Borcherds R.E.: Automorphic forms on \({O_{s+2,2}(\mathbb {R})}\) and infinite products. Invent. Math. 120, 161–213 (1995)
Brady M.: Meromorphic solutions of a system of functional equations involving the modular group. Proc. Am. Math. Soc. 30, 271–277 (1971)
Buchstaber V.M., Leykin D.V.: Solution of the problem of differentiation of Abelian functions over parameters for families of (n, s)-curves. Funct. Anal. Appl. 42(4), 268–278 (2008)
Carleson L., Gamelin T.: Complex Dynamics. Springer, New York (1993)
Cartan E.: Leçons sur la théorie des espaces à connexion projective. Gauthier-Villars, Paris (1937)
Doyle P., McMullen C.: Solving the quintic by iteration. Acta. Math. 163, 151–180 (1989)
Duke W., Imamoglu Ö.: The zeros of the Weierstrass \({{\wp}}\) -function and hypergeometric series. Math. Ann. 340, 897–905 (2008)
Eichler M., Zagier D.: On the zeros of the Weierstrass \({{\wp}}\) -function. Math. Ann. 258, 399–407 (1981)
Elbasraoui A., Sebbar A.: The zeros of the Eisenstein series E 2. Proc. Am. Math. Soc. 138(7), 2289–2299 (2010)
Frobenius F.G., Stickelberger L.: Über die differentiation der ellipyischen functionen nach den perioden und invarianten. J. Reine Angew. Math. 92, 311–327 (1882)
Hardy G.H., Ramanujan S.: On the coefficients in the expansions of certain modular functions. Proc. R. Soc. A 95, 144–155 (1918)
Heins M.: On the pseudo-periods of the Weirstrass zeta-function. SIAM J. Numer. Anal. 3, 266–268 (1966)
Houghton, C.J., Manton, N.S., Sutcliffe, P.M.: Rational maps, monopoles and skyrmions. Nucl. Phys. B 510 [PM], 507–537 (1998)
Hurwitz A.: Sur le développement des fonctions satisfaisant à une équation différentielle algébrique. Ann. Sci. École Norm. Sup. 3(6), 327–332 (1889)
Kaneko M., Yoshida M.: The kappa function. Int. J. Math 14–9, 1003–1013 (2003)
Knopp M., Mason G.: Generalized modular forms. J. Number Theory. 99, 1–28 (2003)
Klein F.: Lectures on the Icosahedron and the Solution of Equations of the Fifth Degree. Dover, New York (1956)
Lie, S.: Vorlesungen über continuierliche Gruppen mit Geometrischen und anderen Anwendungen. Chelsea Publishing Co., Bronx, New York (1971)
Mahler K.: On algebraic differential equations satisfied by automorphic functions. J. Aust. Math. Soc. 10, 445–450 (1969)
Mahler K.: Lectures on transcendental numbers Lecture Notes in Math., vol. 546. Springer, Berlin (1976)
Maillet E.: Introduction à la théorie des nombres transcendants et des proprités arithmétiques des fonctions. Gauthier-Villars, Paris (1906)
McKay J., Sebbar A.: Fuchsian groups, automorphic functions and Schwarzians. Math. Ann. 318, 255–275 (2000)
Pólya G., Szegö G.: Problems and Theorems in Analysis, vol. I. Springer, Berlin (1976)
Ramanujan S.: On certain arithmetical functions. Trans. Camb. Philos. Soc. 22, 159–184 (1916)
Rankin R.A.: Modular Forms and Functions. Cambridge University Press, Cambridge (1977)
Resnikoff H.L.: On differential operators and automorphic forms. Trans. Am. Math. Soc. 124, 334–346 (1966)
Schappacher, N.: Some milestones of Lemniscatomy. Lecture Notes in Pure and Applied Mathematics Series 193. M. Dekker, New York, 257–290 (1997)
Schwarz H.A.: Gesammelte Mathematische Abhandlungen, vol. 2. Springer, Berlin (1880)
Sebbar, A. Sebbar, A.: Eisenstein series and modular differential equations. Can. Math. Bull. doi:10.4153/CMB-2011-091-3
Sibuya Y., Sperber S.: Arithmetic properties of power series solutions of algebraic differential equations. Ann. Math. (2) 113(1), 111–157 (1981)
Smart J.: On meromorphic functions commuting with elements of a function group. Proc. Am. Math. Soc. 33, 343–348 (1972)
Tannery J., Molk J.: Eléments de la théorie des fonctions elliptiques, pp. 1893–1902. Gauthier-Villars, Paris (1990)
Whittaker E.T., Watson G.N.: A Course in Modern Analysis, 4th edn. Cambridge University Press, Cambridge (1990)
Zagier D.: Elliptic Modular Forms and Their Applications in: The 1-2-3 of Modular Forms Universitext. Springer, Berlin (2008)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Sebbar, A., Sebbar, A. Equivariant functions and integrals of elliptic functions. Geom Dedicata 160, 373–414 (2012). https://doi.org/10.1007/s10711-011-9688-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10711-011-9688-7
Keywords
- Equivariant functions
- Schwarz derivative
- Cross-ratio
- Modular forms
- Platonic solids
- Integrals of elliptic functions