Trying to understand the meaning of "Sum Rules"

[qnach]

TL;DR

sum rules

I have encountered the name "sum rules" in many places, such as EM, acoustics,... But I understand none. In what kind of situation will a sum rule occurs? What does it said exactly?

 

[PeroK]

Do you mean the principle of superposition?

 

[weirdoguy]

in many places

Which in particular? I've seen many places, but I don't necessarily know what you are talking about

 

[Baluncore]

In what kind of situation will a sum rule occurs?

"Sum rules" apply to situations where things are summed, added, or accumulated. The applicable rules will depend on the field and the particular application. You need to specify in which field you have encountered the sum rules, and what was being summed.

 

[mad mathematician]

I think you use there something like Poisson summation.
https://en.wikipedia.org/wiki/Poisson_summation_formula

 

[renormalize]

TL;DR Summary: sum rules

I have encountered the name "sum rules" in many places, such as EM, acoustics,... But I understand none. In what kind of situation will a sum rule occurs? What does it said exactly?

Sum rules are common in elementary particle physics. See https://en.wikipedia.org/wiki/Sum_rules_(quantum_field_theory) for over a dozen examples.

 

[sophiecentaur]

TL;DR Summary: sum rules

In what kind of situation will a sum rule occurs?

I hadn't come across this by name but it certainly makes sense and I got the 'right answers' for the example questions in this link.
It's along the same lines as combining probabilities which we did deal with a School.