- #1
lasm2000
- 34
- 3
It is common lore to write lagrangians in field theories in the form
[tex]L(t)=\int d^{3}x\mathcal{L}(\phi_{a},\partial_{\mu}\phi_{a})[/tex].
Nonetheless, is there any particular reason for doing that? Why do we neglect higher order derivatives? Does it mess around with Lorentz invariance or something like that? I have heard that higher order lagrangians give origin to a spectra that is not bounded from below (then we can always have radiative transitions to a lower level).
Can someone confirm that or knows of a better reason?
[tex]L(t)=\int d^{3}x\mathcal{L}(\phi_{a},\partial_{\mu}\phi_{a})[/tex].
Nonetheless, is there any particular reason for doing that? Why do we neglect higher order derivatives? Does it mess around with Lorentz invariance or something like that? I have heard that higher order lagrangians give origin to a spectra that is not bounded from below (then we can always have radiative transitions to a lower level).
Can someone confirm that or knows of a better reason?