 1:46 AM
I'll just leave this here:
0  In QFT a scalar field can be expressed as $$\phi(x)=\int \dfrac{d^3k }{(2\pi)^3\sqrt{2\omega_k}}(a_k(t)+a_{-k}^\dagger(t))e^{i\mathbf{k}\cdot \mathbf{x}}$$ $$\pi(x)=\int \dfrac{d^3k}{(2\pi)^3 \sqrt{2\omega_k}}\left(-i\sqrt{\dfrac{\omega_k}{2}}\right)(a_k(t)-a_{-k}^\dagger(t))e^{i\mathbf{k}\cdot... Despite being literally a "what am I doing wrong" question (which we generally take to be off topic), I rather like the way the question is asked, and I would kind of like to see it be on topic. 2:13 AM @DavidZ I agree, but the asker of that question has deleted it. Or replaced it: 0  In QFT I've seem a free field being defined as$$\phi(x)=\int \dfrac{d^3k}{(2\pi)^3\sqrt{2\omega_k}}(a_p e^{-ip_\mu x^\mu}+a_p^\dagger e^{ip_\mu x^\mu})$$where a_p is time independent and the time dependence is contained in the exponential. On the other hand, this can be written as$$\phi(... Hm, well no harm done since there were no votes, comments, or answers on the earlier question - but we might want to mention to them that deleting and reposting is not preferred

20 hours later… 10:30 PM
@heather @Kenshin (Einstein?) Physics Problems Q and A website is currently not reachable. Fatal Error message coming up in browser since about 9 hours ago.