• asympt(hypergeometric...)

    From jfh@21:1/5 to All on Mon Aug 22 21:14:00 2016
    Maple V.4 gave the first few terms of the asymptotic expansion of a hypergeometric function correctly (albeit without the O(something) term):

    |\^/| Maple V Release 4 (Victoria University)
    ._|\| |/|_. Copyright (c) 1981-1996 by Waterloo Maple Inc. All rights
    \ MAPLE / reserved. Maple and Maple V are registered trademarks of
    <____ ____> Waterloo Maple Inc.
    | Type ? for help.
    readlib(hypergeom);
    proc() ... end

    asympt(hypergeom([1],[3/2],x),x);
    bytes used=1000064, alloc=851812, time=0.75
    1/2 1/2 1 1 15 1
    1/2 Pi (1/x) exp(x) - 1/2 1/x + 1/4 ---- - 3/8 ---- + --
    ----
    2 3 16 4
    x x x
    but now Maple 2015 can't to do it! Why is it worse than it was 19 years ago?

    |\^/| Maple 2015 (X86 64 LINUX)
    ._|\| |/|_. Copyright (c) Maplesoft, a division of Waterloo Maple Inc. 2015
    \ MAPLE / All rights reserved. Maple is a trademark of
    <____ ____> Waterloo Maple Inc.
    | Type ? for help.
    asympt(hypergeom([1],[3/2],x),x);
    Error, (in asympt) unable to compute series

    (Of course simplify will work around that problem, but more complicated cases like hypergeom([1], [3/2, 3/2], x) do not reduce to simpler functions, though the necessary mathematics to find their asymptotic series has been known since 1940 and involves
    just the sort of calculation that Maple ought to be good at.)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Axel Vogt@21:1/5 to jfh on Tue Aug 23 09:22:05 2016
    On 23.08.2016 06:14, jfh wrote:
    Maple V.4 gave the first few terms of the asymptotic expansion of a hypergeometric function correctly (albeit without the O(something) term):

    ...
    readlib(hypergeom);
    proc() ... end

    asympt(hypergeom([1],[3/2],x),x);
    bytes used=1000064, alloc=851812, time=0.75
    1/2 1/2 1 1 15 1
    1/2 Pi (1/x) exp(x) - 1/2 1/x + 1/4 ---- - 3/8 ---- + --
    ----
    2 3 16 4
    x x x
    but now Maple 2015 can't to do it! Why is it worse than it was 19 years ago?

    ...
    asympt(hypergeom([1],[3/2],x),x);
    Error, (in asympt) unable to compute series

    (Of course simplify will work around that problem, but more complicated cases like
    hypergeom([1], [3/2, 3/2], x) do not reduce to simpler functions, though the necessary
    mathematics to find their asymptotic series has been known since 1940 and involves just
    the sort of calculation that Maple ought to be good at.)


    Maple 2016 can do both, see below.

    I want to encourage you to ask at the active Maple forum, http://www.mapleprimes.com/recent/all


    hypergeom([1],[3/2],x);
    asympt(%,x);

    1/2*Pi^(1/2)*(1/x)^(1/2)*exp(x)-1/2/x+1/4/x^2-3/8/x^3+15/16/x^4-105/32/x^5+O(1/x^6)

    hypergeom([1], [3/2, 3/2], x);
    asympt(%,x);

    (1/8*Pi^(1/2)*(1/x)^(3/4)+1/128*Pi^(1/2)*(1/x)^(5/4)+9/4096*Pi^(1/2)*(1/x)^(7/4)+75/65536*
    Pi^(1/2)*(1/x)^(9/4)+3675/4194304*Pi^(1/2)*(1/x)^(11/4)+59535/67108864*Pi^(1/2)*(1/x)^(13/4)
    +O((1/x)^(15/4)))*exp(2/(1/x)^(1/2))

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)