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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

1309.0. "Mandelbrot problem of the week:" by CHOVAX::YOUNG (TP: A giant in my own mind.) Tue Oct 16 1990 17:37

    Can a closed (and connected) curve consisting entirely of points in the
    Mandelbrot set ever circumscribe a point *not* in the Mandelbrot set?
    
    --  Barry
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1309.1CSC32::J_MARSHSvelte & Petite-nosedTue Oct 16 1990 19:242
    Isn't that equivalent to "is the Mandelbrot set simply connected?"
    I believe the answer is yes.
1309.2GUESS::DERAMODan D'EramoTue Oct 16 1990 20:165
>>    Isn't that equivalent to "is the Mandelbrot set simply connected?"

	More likely to its opposite.

	Dan
1309.3my vote is: no to .0, yes to .1SONG::WARMACKI dictate what I moderateTue Oct 16 1990 21:0816
    RE: .2
    
    That's exactly what I was thinking of saying.  However, I chickened
    out, due to the realization I couldn't personally back it up
    mathematically.  Another thing that made me balk was:  even if it is
    connected, what's to stop it from having an "island" not belonging to
    the set?  From the images that have been generated, it is easy to say
    that no such "island" exists inside of the set, but how can we REALLY
    know, unless it can be proven mathematically?  I think it might be
    possible to prove it, but don't ask me--I don't have a doctorate in
    math.
    
    I wonder if that is the point of the question in .0?  Sounds like a
    great challenge!!
    
    Andy
1309.4ALLVAX::JROTHIt's a bush recording...Tue Oct 16 1990 21:3122
    Hubbard and Douady proved that the boundary of the Mandelbrot set
    is a deformed circle which never "crosses" itself.  While there
    appear to be disconnected islands, these are attached to the main
    set by the boundary curve.  The curve becomes tangent to itself
    at points, but never meets itself transversally.

    This proof involves a potential theoretic limiting argument - one
    neat result is that the contours one sees in pictures are equipotentials
    that would result if the set were a charged conductor.

    The proof is in the paper

	A. Douady, J. Hubbard, "Iteration des polynomes quadratiques
	complexes", Comptes Rendus Paris Acad. Sci. 294, (1982) pp 123-126.

    They also explained some other neat stuff about the order of branching
    along the boundaries of the various parts of the set.

    They acknowledged that computer pictures were "decisive" in
    formulating their proofs.

    - Jim