(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Zwiebach QC 5.2

Tau is the parametrization of a worldline. p is the relativistic momentum

Show that [tex] \frac{ dp_{\mu}}{d \tau'}} = 0 [/tex]implies that [tex] \frac{ dp_{\mu}}{d \tau'}} = 0 [/tex] holds for an arbitrary paramter [tex] \tau'(\tau)) [/tex]

What needs to be true about the derivative of tau' with respect to tau for tay' to be a good parameter when tau is a good one?

2. Relevant equations

3. The attempt at a solution

By the chain rule dp/dtau *dtau'/dtau = dp/dtau * dtau/dtau' but we only have tau' as a function of tau and I am not sure whether you can just flip the differentials in that derivative?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: String theory question

**Physics Forums | Science Articles, Homework Help, Discussion**