- #1
Azrael84
- 34
- 0
Hey,
Starting with the conversation law for the stress-energy tensor; [tex] T^{\alpha \beta}{}_{,\beta}=0 [/tex]. Does anyone know how I can prove:
[tex] \frac{\partial}{\partial t} \int {T^{0\alpha} d^3x} =0 [/tex]
for a bounded system (i.e. one for which [tex] T^{\alpha \beta}=0 [/tex] outside a bounded region of space).
Seems really obvious intuivitvely that this is conservation of energy-momentum, but I just can't seem to get there mathematically.
My thoughts are maybe this involves the generalised Gauss's law so convert the divergence into integral form:
[tex] \int {T^{\alpha \beta}{}_{,\beta} d^4x} =\int{ T^{\alpha \beta}n_{\beta} d^3x[/tex]
So given [tex] T^{\alpha \beta}{}_{,\beta}=0 [/tex] we can say:
[tex]\int{ T^{\alpha \beta}n_{\beta} d^3x=0[/tex]
Not sure where to go from there, if indeed this is the correct direction?
Starting with the conversation law for the stress-energy tensor; [tex] T^{\alpha \beta}{}_{,\beta}=0 [/tex]. Does anyone know how I can prove:
[tex] \frac{\partial}{\partial t} \int {T^{0\alpha} d^3x} =0 [/tex]
for a bounded system (i.e. one for which [tex] T^{\alpha \beta}=0 [/tex] outside a bounded region of space).
Seems really obvious intuivitvely that this is conservation of energy-momentum, but I just can't seem to get there mathematically.
My thoughts are maybe this involves the generalised Gauss's law so convert the divergence into integral form:
[tex] \int {T^{\alpha \beta}{}_{,\beta} d^4x} =\int{ T^{\alpha \beta}n_{\beta} d^3x[/tex]
So given [tex] T^{\alpha \beta}{}_{,\beta}=0 [/tex] we can say:
[tex]\int{ T^{\alpha \beta}n_{\beta} d^3x=0[/tex]
Not sure where to go from there, if indeed this is the correct direction?