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|    sci.math.symbolic    |    Symbolic algebra discussion    |    10,432 messages    |
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|    Message 9,790 of 10,432    |
|    antispam@math.uni.wroc.pl to clicliclic@freenet.de    |
|    Re: More teething help    |
|    27 Jan 18 17:49:32    |
      clicliclic@freenet.de wrote:       >       > antispam@math.uni.wroc.pl schrieb:       > >       > > clicliclic@freenet.de wrote:       > > >       > > > Thanks to the (still unpublished?) Masser-Zanier counterexample       > > > Waldek informed us about, we know that there are infinitely many       > > > (though increasingly complicated algebraic) u^2 for which       > > >       > > > INT(x/((x^2 - u^2)*SQRT(x^3 - x)), x)       > > >       > > > has a solution (also of increasing complexity) in terms of       > > > elementary functions. Consequently, via the usual Moebius       > > > transformation of the integration variable, there are also       > > > infinitely many v = (u^2 - 1)/(u^2 + 1) for which       > > >       > > > INT((y^2 - 1)/((y^2 + 2*v*y + 1)*SQRT(y^4 - 1)), y)       > > >       > > > has such an elementary solution. I too expect these patterns to be       > > > exceptions rather than the rule, the rule being that the number of       > > > pseudo-elliptic cases is finite and small. But does this pair       > > > already exhaust the store of patterns involving simple square-root       > > > radicands and giving rise to infinitely many pseudo-elliptic       > > > integrals?       > >       > > Well, any torsion point leads to a pseudo-elliptic integral. Over       > > algebraically closed field there are infintely many torsion points       > > on any curve. So example with _single_ parameter may be exceptional,       > > put once you allow algebraic extentions there is see of strange       > > examples -- just two parameters family:       > >       > > integrate((1/(x - a) - b)/sqrt(P), x)       > >       > > has no elementary integral valid for continuous family of a and b       > > and infintely many integrable cases when P is a polynomial of       > > degree 3 without multiple factors.       > >       >       > Yes, my comment was about the dependence on a single parameter, with any       > additional parameters kept fixed.              To be clear: above P is fixed. And b is a function of a (there is       at most one b for which the integral is elementary). I think that       b can be given as a simple expression, but it would take extra       effort to find it. If you are really bothered by b you can pass       to Jacobi form, that is take P = (1 - x^2)*(1 - m*x^2). Then       b = 0.              --        Waldek Hebisch              --- SoupGate-Win32 v1.05        * Origin: you cannot sedate... all the things you hate (1:229/2)    |
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