# A Quick question, string theory introduction, lightcone gauge

1. Mar 25, 2017

### binbagsss

Lightcone gauge is $X^u=\tau=1/\sqrt{2}(X^0+X^{D-1})$ (1)

The mode expansions are:

My book says 'it is possible to solve for one of the oscillators in terms of all the others' with this relation.

What is a oscillator? Is this any of the $X^{D}$ coordinates, what exactly does $n$ represent, 'frequencies' of a given oscillator?

Does the notation $X^{D-1}$ refer to any spatial coordinate that is the preferred choice?

So basically the relation (1) reduces the number of equations to solve by one, is this what this statement means?

2. Mar 30, 2017

### PF_Help_Bot

Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.

3. Apr 3, 2017

### cosmik debris

I think X0 is the infinite momentum direction i.e. the direction in which the string is travelling. XD-1 are the dimensions perpendicular to X0, the -1 is to remove the time dimension. Each string comprises a number of mass points which are described as harmonic oscillators, n is the number of the oscillator in the string.