Squared length of 4-momentum g(p,p)?

[berlinspeed]

Homework Statement

Can someone explain why the squared length of p^2 = p dot p = -m^2 and not -m^2*c^2?

Relevant Equations

p^2 = p dot p = -m^2

Explained in statement.

 

[Gaussian97]

That depends on two things:
1. What is the metric you use

2. What are the units you are using.

 

[PeroK]

Problem Statement: Can someone explain why the squared length of p^2 = p dot p = -m^2 and not -m^2*c^2?
Relevant Equations: p^2 = p dot p = -m^2

Explained in statement.

In "natural" units we have $c=1$. See, for example:

http://www.phys.ufl.edu/~avery/course/4390/f2015/lectures/natural_units.pdf