Is there a sign for harmony or harmonic as there is for infinity? If so where can I find it or what is it?

Answer 1

I think physists would agree that when they see the equation:
y(t)=Asin(wt + *) ,
where A is amplitude, t is time and * is the phase shift(typically gamma),

that they automatically think of simple harmonic motion.

So i would consider that equivalent to the symbol for infinity

Answer 2

No.