# Fractals/Iterations in the complex plane/julia

Various types of dynamics needs various algorithms

# Types

Classification of Julia sets according to :

• topology of filled Julia set's interior
• local dynamics near periodic points
• connectedness

Filled Julia set can have :

• an non-empty interior ( Julia set is connected )
• parabolic: filled Julia set have parabolic cycle ( c is on boundary of hyperbolic componnent )
• Siegel : filled Julia sets containing Siegel disc. Julia set can be locally connected or not. That depends on the rotation number. ( c is on boundary of hyperbolic component )
• attracting : filled Julia set have attracting cycle ( c is inside hyperbolic component )
• superattracting : filled Julia set have superattracting cycle( c is in the center of hyperbolic component ). Examples : Airplane Julia set, Douady's Rabbit, Basillica.
• empty interior
• disconnected ( c is outside of Mandelbrot set )[1]
• connected
• Cremer Julia sets ( c is on boundary of hyperbolic component , Julia set is connected but not locally connected)
• dendrits ( Julia set is connected and locally connected ). Examples :
• Misiurewicz Julia sets (c is a Misiurewicz point )
• Feigenbaum Julia sets ( )
• others which have no description

# Models of Julia set

Lamination of rabbit Julia set

# Algorithms

"... a single algorithm for computing all quadratic Julia sets does not exist." [6]

Types

• Escape time ( attraction time to infinity ( attractor for all polynomials )
• attraction time to finite attractor inside filled Julia set )
• estimation of distance to Julia set ( DEM/J )
• Inverse Iteration Method = IIM/J
• Testing equicontinouty by Michael Becker [7]

## equicontinouty

"The Julia set of f then is the set of all points of G, at which this sequence of iterated functions is not equicontinous. The Fatou set is its complement. Laxly said the action of the iterated functions on near points is examined. Places, where points, which are near enough, remain near during iterations, belong to the Fatou set. Places, where points, as near they may be, are teared apart, belong to the Julia set. In the following I only consider functions, which map the Riemann sphere, i.e. the complex plane with an ideal point "infinity" added, to itself. The Julia sets are white, the Fatou sets black." Michael Becker