## 258 Reputation

18 years, 287 days

## use of ~ in an input name....

Maple 2016

In feature "Procedures for two animations" posted by Kitonium appears this line, within a procedure.

T1:=(O2*~y+O1*~u)/~(y+u): T2:=(O3*~u+O2*~v)/~(u+v): T3:=(O4*~v+O3*~z)/~(v+z):

What is the meaning of "~y", for instance, and how does it differ from "y"?

I understand the conventional usage of ~ with a name in output to imply that that name is subject to an assumption.

I have been able to find nothing pertinent in the Maple Help information.  Please enlighten me.

## Plotting Heun functions...

Maple 2016

One new feature of Maple 2016 is claimed to be

but when I try HeunD or HeunG there is no output -- no error message, nothing.  Is this behaviour what a user should expect of this command?

## Heun and Lame functions...

Heun functions arise in the solutions of various differential equations, for instance for the Schroedinger equation for the hydrogen atom in physics, which is also of chemical interest.  Although they have been nominally included in Maple for several years, they are still in a primitive state; despite their obscurity and intractable nature, there seems not to exist much possibility, within Maple, to convert these functions into better known and characterised functions.  A similar condition holds for Lame and spheroidal functions that are invaluable in the solution of differential equations in physics but are not even mentioned in Maple.

The compilation of mathematical functions by Abramowitz and Stegun was published half a century ago, but there are still important functions explained therein that are lacking from Maple, not to mention the successor in the NIST Digital Library of Mathematical Functions.

Integral equations are another weak component of Maple; the present content relies on a basis of work of ProfessorCorless and his student submitted to the 'Maple Share Library' -- decades ago.  Forty years ago, David Stoutemyer generated some procedures to solve non-linear integral equations in Reduce, but forty years later Maple has no benefit from that knowledge.

We can only hope that Maple 19 will remedy some of these gross deficiencies.  The teaching, learning and practice of physics will benefit from their implementation.

## Heun functions in Maple...

Maple

At the internet site of The Heun Project, a strong declaration is made that only Maple incorporates Heun functions, which arise in the solution of differential equations that are extremely important in physics, such as the solution of Schroedinger's equation for the hydrogen atom.  Indeed solutions appear in Heun functions, which are highly obscure and complicated to use because of their five or six arguments, but when one tries to convert them to another function, nothing seems to work.  For instance, if one inquires of FunctionAdvisor(display, HeunG), the resulting list contains

"The location of the "branch cuts" for HeunG are [sic, is] unknown ..." followed by several other "unknown" and an "unable". Such a solution of a differential equation is hollow.

Incidentally, Maple's treatment of integral equations is very weak -- only linear equations with simple solutions, although procedures by David Stoutemyer from 40 years ago are available to enhance this capability.

When can we expect these aspects of Maple to work properly, for applications in physics?

## solution of differential equations...

Maple 18

The ability of Maple to solve differential equations is unsurpassed, but when the solutions appear in terms of Heun functions that result is disappointing because it is either difficult or impossible to convert those functions to other functions more commonly used and for which plots are readily generated.

Specifically, does any reader have a suggestion what to do with Heun C and Heun G functions?  In principle, they seem to be related to 1F1 and 2F1 hypergeometric functions, but the conversion seems not to succeed, and it is not obvious how to make it succeed.  In both cases of interest, the literature contains hints of solutions in other functions.

It seems that a solution of a differential equation in terms of Heun functions is not a solution at all.

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