A recent refinement of Kerékjártó's Theorem has shown that in $ \mathbb R $ and $ \mathbb R^2 $ all $ \mathcal C^l $–solutions of the functional equation $ f^n = \text{Id} $ are $ \mathcal C^l $–linearizable, where $ l\in \{0,1,\dots \infty\} $. When $ l\geq 1 $, in the real line we prove that the same result holds for solutions of $ f^n = f $, while we can only get a local version of it in the plane. Through examples, we show that these results are no longer true when $ l = 0 $ or when considering the functional equation $ f^n = f^k $ with $ n>k\geq 2 $.
Citation: |
[1] |
C. Babbage, An essay towards the calculus of functions, Philos. Trans. Royal Soc., 105 (1815), 389-423.
![]() |
[2] |
N. Bacaër, A Short History of Mathematical Population Dynamics, Springer-Verlag London Ltd., London, 2011.
doi: 10.1007/978-0-85729-115-8.![]() ![]() ![]() |
[3] |
K. Baron and W. Jarczyk, Recent results on functional equations in a single variable, perspectives and open problems, Aequ. Math., 61 (2001), 1-48.
doi: 10.1007/s000100050159.![]() ![]() ![]() |
[4] |
R. H. Bing, Inequivalent families of periodic homeomorphisms of $E^3$, Ann. of Math., 80 (1964), 78-93.
doi: 10.2307/1970492.![]() ![]() ![]() |
[5] |
A. Cima, A. Gasull, F. Mañosas and R. Ortega, Linearization of planar involutions in $\mathcal C^1$, Ann. Mat. Pura Appl., 194 (2015), 1349-1357.
doi: 10.1007/s10231-014-0423-5.![]() ![]() ![]() |
[6] |
A. Cima, A. Gasull, F. Mañosas and R. Ortega, Smooth linearisation of planar periodic maps, Math. Proc. Camb. Philos. Soc., 167 (2019), 295-320.
doi: 10.1017/S0305004118000336.![]() ![]() ![]() |
[7] |
A. Constantin and B. Kolev, The theorem of Kerérekjártó on periodic homeomorphisms of the disc and the sphere, Enseign. Math., 40 (1994), 193-204.
![]() ![]() |
[8] |
G. M. Ewing and W. R. Utz, Continuous solutions of the functional equation $f^n(x) = f(x)$, Canadian J. Math., 5 (1953), 101-103.
doi: 10.4153/CJM-1953-012-8.![]() ![]() ![]() |
[9] |
A. Haefliger, Plongements différentiables de variétés dans variétés, Comment. Math. Helv., 36 (1962), 47-82.
![]() ![]() |
[10] |
R. Haynes, S. Kwasik, J. Mast and R. Schultz, Periodic maps on $R^7$ without fixed points, Math. Proc. Camb. Philos. Soc., 132 (2002), 131-136.
doi: 10.1017/S0305004101005345.![]() ![]() ![]() |
[11] |
M. Hirsch, Differential Topology, Springer-Verlag, 1976.
![]() ![]() |
[12] |
M. Holz, K. Steffens and E. Weitz, Introduction to Cardinal Arithmetic, Birkhäuser Verlag, 2010.
doi: 10.1007/978-3-0346-0330-0.![]() ![]() ![]() |
[13] |
G. Ishikawa and T. Nishimura, Smooth retracts of Euclidean space, Kodai Math. J., 18 (1995), 260-265.
![]() ![]() |
[14] |
W. Jarczyk, Babbage equation on the circle, Publ. Math., 63 (2003), 389-400.
![]() ![]() |
[15] |
N. McShane, On the periodicity of homeomorphisms of the real line, Amer. Math. Monthly, 68 (1961), 562-563.
doi: 10.2307/2311152.![]() ![]() ![]() |
[16] |
J. Milnor, Topology from the Differentiable Viewpoint, University of Virginia Press, 1965.
![]() ![]() |
[17] |
J. Munkres, Topology, 2$^{nd}$ edition, Prentice Hall, Inc., Upper Saddle River, NJ, 2000.
![]() ![]() |
[18] |
I. Richards, On the classification of non-compact surfaces, Trans. Am. Math. Soc., 106 (1963), 259-269.
doi: 10.1090/S0002-9947-1963-0143186-0.![]() ![]() ![]() |
[19] |
M. Spivak, A Comprehensive Introduction to Differential Geometry, vol. 1, 3$^rd$ edition, Publish or Perish, 1970.
![]() ![]() |
[20] |
E. Stein, Complex Analysis, Princeton University Press, Princeton, N.J., 2003.
![]() ![]() |
[21] |
T. W. Tucker, On the Fox-Artin sphere and surfaces in noncompact 3-manifolds, Q. J. Math., 28 (1977), 243-253.
doi: 10.1093/qmath/28.2.243.![]() ![]() ![]() |
[22] |
B. von Kérékjartó, Über die periodischen transformationen der kreisscheibe und der kugelfläche, Math. Ann., 80 (1919), 36-38.
doi: 10.1007/BF01463232.![]() ![]() ![]() |
[23] |
V. B. Yap, Re-imagining the Hardy-Weinberg law, 2013, arXiv: 1307.4417v1.
![]() |
Graph of a generic idempotent continuous function in
Graph of the function
Graph of the function
Concatenation of two overhand knots, one figure eight knot and one overhand knot