restart; 

g := proc (i) 
if i = 1 then a else 0 fi
end proc:

h := sum(g(i), i = 1 .. f);

The result is h:=0 instead of h:=a. What's wrong?

I have several questions concerning manipulations with creation and annihilation operators. I would be grateful if  besides answering my questions you would give me some suggestions for improving the code.

Background of the physic problem
I have a crystal lattice with several sites per unit cell. Every site can holds one, two or none of electrons. Electron at every site can be at one of two states: spin up and spin down. Electrons are Fermi particles so anticommutative basis is used. Index 'i' ...

Maple_17_fault.mwA piece of code presented in attached file can be easily calculated with Maple 13 and ancient (Pentium M) laptop. While Maple 17 and modern PC with Core i7 3770K and 32GB RAM on board unable to do the same. What's wrong? Do I need to make some settings of Maple 17? Can I install Maple 13 and Maple 17 on the same PC? Will not any conflicts occur? Thank you.

I need to solve the following equation:

>restart;
>z := a+b*y*conjugate(y) = 0;

where y*conjugate(y) is unknown. How to solve it or how to eliminate y*conjugate(y) from the equation?

Thank you.

Please help me with transformation of the following expression:

> z:=abs(a)^2*b+abs(a)^2*c*conjugate(a);

where I want to derive

a*(conjugate(a)*b+conjugate(a)^2*c)

I try the following:

> z:=collect(z,a);

However it does't transformate z in any way.

 

In other words if I have
>z:=a*conjugate(a);

>z:=simplify(z);

I derive z=|a|^2. How to decompose z back into a*conjugate(a)?