Math 2.0

Dynamical systems and ergodic theory Definition

Holomorphic dynamics in several variables

Builds on Complex manifoldHolomorphic mapIterated functionDiscrete-time dynamical systemNormal family

Definition

Let XX be a complex manifold of dimension k≥2k \ge 2, and let f ⁣:X→Xf \colon X \to X be a holomorphic map. For m≥0m \ge 0, the iterate fmf^m is the mm-fold composition of ff, with f0=id⁡f^0 = \id. The orbit of x∈Xx \in X is the sequence x,f(x),f2(x),…x, f(x), f^2(x), \ldots. Holomorphic dynamics in several variables is the study of the orbits of such a discrete-time dynamical system (X,f)(X, f).

Let XX be compact. The Fatou set of ff is the set of points x∈Xx \in X with a neighbourhood UU on which the iterates (fm∣U)m≥0(f^m|_U)_{m \ge 0} form a normal family. This means that every sequence of these iterates has a subsequence converging uniformly on compact subsets of UU. The Julia set of ff is the complement of the Fatou set.

Remarks

The main cases are X=ℙkX = \mathbb{P}^k with ff a holomorphic endomorphism of algebraic degree d≥2d \ge 2, and X=ℂ2X = \C^2 with ff a polynomial automorphism.

Example: f[z0:⋯:zk]=[z0d:⋯:zkd]f[z_0 : \cdots : z_k] = [z_0^d : \cdots : z_k^d] with d≥2d \ge 2 is a holomorphic self-map of ℙk\mathbb{P}^k. It is well defined because the zjdz_j^d vanish together only when all zjz_j vanish. If one coordinate ziz_i has strictly larger modulus than all the others, then the ratios (zj/zi)dm(z_j/z_i)^{d^m} tend to 00 uniformly near [z][z]. So the orbit tends to the coordinate point with 11 in place ii, the iterates converge near [z][z], and [z][z] lies in the Fatou set.

Example: a Hénon map (x,y)↦(p(x)−ay,x)(x, y) \mapsto (p(x) - a y, x) with a≠0a \ne 0 and deg⁡p≥2\deg p \ge 2 is a holomorphic automorphism of ℂ2\C^2.

Non-example: the map (z,w)↦(zˉ2,w)(z, w) \mapsto (\bar z^2, w) of ℂ2\C^2 is smooth but not holomorphic, so its iteration is not part of holomorphic dynamics.

For k=1k = 1 the same definitions give one-variable complex dynamics.

Reading path

To understand this page from the ground up, read these 6 pages in order. The foundations come first.

Show the path as a graph
Each page uses the pages above it. The colour of the bar on a box shows how strong the evidence is, and the box also gives it as text. The list has the same pages.
  • no evidence level
  1. Complex manifold concept
  2. Discrete-time dynamical system concept
  3. Holomorphic map concept
  4. Iterated function concept
  5. Normal family concept
  6. Holomorphic dynamics in several variables definition

Further reading

  1. Web https://en.wikipedia.org/wiki/Complex_dynamics
About this page
TagKQ0ABB8N82
URIm2://KQ0ABB8N82
Kinddefinition
WritingW0 stub
MSC37F80, 32H50
DefinesHolomorphic dynamics in several variables
UsesComplex manifold, Holomorphic map, Iterated function, Discrete-time dynamical system, Normal family

Markdown · JSON · Edit on GitHub

What this page needs for W1

  • an inventory row: the row of the inventory that the node accounts for (0 of 1)
  • a source with a locator (0 of 1)

The writing levels say how complete the text of a page is. They do not measure its truth.

What links here

No page links to this page yet.