- #1
karkas
- 132
- 1
Homework Statement
I'm having a bit of trouble evaluating the following commutator
$$ \left[T^{+},T^{-}\right] $$
where [itex]T^{+}=\int_{M}d^{3}x\:\bar{\nu}_{L}\gamma^{0}e_{L}=\int_{M}d^{3}x\:\nu_{L}^{\dagger}e_{L} [/itex]
and
[itex] T^{-}=\int_{M}d^{3}x\:\bar{e}_{L}\gamma^{0}\nu_{L}=\int_{M}d^{3}x\:e_{L}^{\dagger}\nu_{L}[/itex]
a step necessary to prove that the [itex]\text{SU}(2)_L[/itex] is a part of the GWS Electroweak gauge symmetry group. Discussing with my professor I've been confused as to how I should proceed with this. Initially, I wrote:
[itex]\left[T^{+},T^{-}\right]=\int_{M}d^{3}x\:d^{3}y\:\left[\nu_{L}^{\dagger}\left(x^{\mu}\right)e_{L}\left(x^{\mu}\right),e_{L}^{\dagger}\left(y^{\mu}\right)\nu_{L}\left(y^{\mu}\right)\right]\delta^{3}\left(x-y\right)[/itex]
according to Paschos (Electroweak Theory) where my something of an unfamiliarity with QFT leaves me wondering exactly how I inserted that Dirac delta, but I see it's necessary.
Homework Equations
The Attempt at a Solution
I thought of using the fermionic algebra, the anticommutator [itex]\left\{ a(y),a^{\dagger}(x)\right\} =1 \Rightarrow a(y)a^{\dagger}(x)=\left\{ a(y),a^{\dagger}(x)\right\} -a^{\dagger}(x)a(y)[/itex] along with the Dirac delta should let me reach [itex]\left[T^{+},T^{-}\right] = \frac{1}{2}\int_{M}d^{3}x\:\left(\nu_{L}^{\dagger}\nu_{L}-e_{L}^{\dagger}e_{L}\right)[/itex]
and therefore
$$\left[T^{+},T^{-}\right]=T^{3}$$
but my professor says that this is wrong. I also tried [itex]\left[T^{+},T^{-}\right]=\left[\bar{\chi}_{L}\gamma^{0}\tau^{+}\chi_{L},\bar{\chi}_{L}\gamma^{0}\tau^{-}\chi_{L}\right][/itex] but I got weirded out by the [itex]u\bar{u}[/itex] factors and lucked out.
Could someone construct the proof or guide me addressing some of these issues?