Static Gauges in String Theory - Zwiebach Ch. 6

[ehrenfest]

Homework Statement

I am learning about static gauges in string theory from Zwiebach chapter 6.

Is it true that a static gauge is simply a parametrization where time is the parameter? That seems much too simple.

Homework Equations

The Attempt at a Solution

 

[StatusX]

The string worldsheet is a two dimensional surface, so it takes two coordinates to parametrize it. If you pick an inertial observer, you can take one of these coordinates to be his time. Then the lines where this coordinate is constant are the instaneous configurations of the string according to this observer, with each string parametrized in some way by the other coordinate. This is the static gauge. This is pretty obvious, but it turns out to make the equations of motion much nicer than for general coordinates (although there may be other gauges that make other calculations easier). Choosing the second coordinate so that the energy density with respect to this coordinate along the string is constant makes things even nicer.

 

[ehrenfest]

OK, so that static gauge is just a parameter set equal to the time in some IRF.

 

[StatusX]

Again, there are two parameters. In the static gauge, one of them is time, and the other is something else. There is not a unique static gauge, even for a single inertial frame.

 

[ehrenfest]

I see. Thanks.

 

[ehrenfest]

Zwiebach refers to other possible gauges for the string worldsheet later in the book (e.g. the light-cone gauge). What is the difference between a gauge (in the sense Zwiebach uses it) and a parametrization?