- #1
Dixanadu
- 254
- 2
Hey guys,
This is really confusing me cos its allowing me to create factors of 2 from nowhere!
Basically, the first term in the Lagrangian for a real Klein-Gordon theory is
[itex]\frac{1}{2}(\partial_{\mu}\phi)(\partial^{\mu}\phi)[/itex].
Now let's say I wana differentiate this by applying the [itex]\partial_{\mu}[/itex] operator. Using the chain rule, I get:
[itex] \frac{1}{2} \left[ (\partial_{\mu}\partial_{\mu}\phi)(\partial^{\mu}\phi)+(\partial_{\mu}\phi)(\partial_{\mu}\partial^{\mu}\phi)\right][/itex]
Which must be wrong because this cancels the factor of [itex]\frac{1}{2}[/itex] outside the square brackets!
My conclusion is that one term must be 0, or I'm doing something horribly wrong (or both :( ) can someone please correct me?
thank you!
This is really confusing me cos its allowing me to create factors of 2 from nowhere!
Basically, the first term in the Lagrangian for a real Klein-Gordon theory is
[itex]\frac{1}{2}(\partial_{\mu}\phi)(\partial^{\mu}\phi)[/itex].
Now let's say I wana differentiate this by applying the [itex]\partial_{\mu}[/itex] operator. Using the chain rule, I get:
[itex] \frac{1}{2} \left[ (\partial_{\mu}\partial_{\mu}\phi)(\partial^{\mu}\phi)+(\partial_{\mu}\phi)(\partial_{\mu}\partial^{\mu}\phi)\right][/itex]
Which must be wrong because this cancels the factor of [itex]\frac{1}{2}[/itex] outside the square brackets!
My conclusion is that one term must be 0, or I'm doing something horribly wrong (or both :( ) can someone please correct me?
thank you!