Recent content by sirapwm

Right. That's what this statement indicated: "For ##Q\ne 0##, the non-relativistic kinematics aren't consistent. We can see this if we try to show that the total momentum is conserved in the center of mass."

Never mind. That’s stupid. I see the refutation. The problem I’m having is with Galilean boosts. And they’re jus wrong when ##Q\ne 0##.

You’re right about lab frame momentum conservation making it unsurprising. But I claim it’s zero non-relativistically, which is still a bit surprising. But maybe it shouldn’t be. For ##Q\ne 0##, the non-relativistic kinematics aren't consistent. We can see this if we try to show that the...

I was surprised this morning when I got off on a tangent regarding the amount of energy available in the laboratory frame just at threshold. It reveals an interesting relativistic effect. Consider a reaction (I'm thinking in terms of nuclei and/or particles) ##1 + 2 \to 3 + 4 + \cdots## with...

This comment was not well constructed originally by me. The original question was about the equivalence of the terms "endothermic" and "threshold reaction" using the reaction ##^{10}B(n,2\alpha)^3H## as an example. And then I muddied the waters by using a different reaction...

I happened to stumble across this (old) question and, since the premise of the question is incorrect, I thought I should comment. The reaction ##^{10}B(n,\alpha)^7Li## has a positive ##Q##-value (of about 2.8 MeV). This means it is exoergic (or, as it's sometimes written, exothermic -- I think...

I'm aware of this paper. It agrees with my statement above, regarding tupos' comment, that the exact (not the asymptotic expression for ##\eta = r-z \to \infty##) wave function is finite at all finite ##r##. And yes, as you point out, the exact solution is a linear superposition of two linearly...

Many thanks. -S

The indefinite integral effected in this PF post (from 2010) is not the correct expression for the Rutherford differential cross section. Here is the correct expression in a slightly different notation (so I'll try to be careful to define all the symbols). The expression for the differential...

I'm a working theoretical physicist who has long read PF. I'd like to start contributing.