Forever_a_Newcomer
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 Aug 24 comment Filming light in motion? Good point, not a native English speaker, and automatic orthography correction didn't help me there :D It would be nice to have laser beans though... Aug 24 answered Filming light in motion? Aug 24 accepted When do one-point functions vanish? Aug 23 asked When do one-point functions vanish? Jul 30 accepted Surface terms for field path integrals? Jul 30 comment Surface terms for field path integrals? So the point here is that the "surface terms" vanish when I integrate with ${\cal L} \rightarrow (1+i \epsilon){\cal L}$, right? Jul 30 revised Surface terms for field path integrals? Edited to include formulas according to suggestions in comment by @user1504 Jul 27 asked Surface terms for field path integrals? Jul 19 accepted Why is the (free) neutron lifetime so long? Jul 19 comment Why is the (free) neutron lifetime so long? @Terry - maybe you did (forget me) but I didn´t forget the question ;) Great answer by the way! My thanks to everyone involved Jul 10 awarded Nice Question Jul 9 awarded Yearling Jul 8 comment Why is the (free) neutron lifetime so long? I not completely satisfied with the answer. It seems to me that dr-bdo-adams and @terry-bollinger are explaining this based on the off-shellness of the W. But still the diference is too big, the neutron lifetime is $10^9$ times bigger than that of the Muon, but the "liberated energy" is only $10^2$ smaller. Is this going like $\left(\frac{E_L}{M_W}\right)^4$? ($E_L$ is the liberated energy). Can someone give me pointers of why we have such a high power in the dependence? Jul 7 asked Why is the (free) neutron lifetime so long? Jun 22 comment How to detect ice in thermostat Nice idea, but he would have to figure out a way to avoid ice formation in the tube itself, which could be hard depending on the setup. Jun 22 comment Energy efficiency of antimatter producion Also, even if you could get antimatter stored in considerable quantities, with efficiency close to 1 (not bigger). What would you do with it? Eletron-positron pairs anihilate into 500 keV gamma rays, which is very bad for propulsion. Photons this hard can´t just be reflected for push. You would have to find materials that would absorb and thermalize them, and then eject these. I don't think this is much better than what we already do, at much higher costs. Jun 22 accepted Imaginary pertubation to a Hamiltonian: how is it the same as rotation to imaginary time? Jun 21 comment Imaginary pertubation to a Hamiltonian: how is it the same as rotation to imaginary time? (...) he uses exactly this substitution to get $Z[J]$. Of course, the potential for a free scalar field is proportional to $q^2$, but wouldn't adding the whole $i\epsilon H$ mess up the momentum integral you need to get from the hamiltonian to the lagrangean? The bothering point here is that this $i \epsilon$ factor will be the one (on page 185) dictating the path of integration to get the propagator. Jun 21 comment Imaginary pertubation to a Hamiltonian: how is it the same as rotation to imaginary time? Yes, I noticed it would be far simpler to add $i \epsilon H$ but, when the author goes on to quantizing a scalar field (page 182) Jun 21 awarded Critic