Recent content by SteDolan

I'm just trying to get my head around calculus of variations so I gave myself a simple example to work with: Suppose I want to get between two points (a and b) through a mountain range with height described by the scalar field h(x,y) whilst staying as low as possible. I want to know what...

Thanks for the hint! I think I understand: The ee -> ee interaction has a scattering channel as well as the annihilation channel. By the Feynman rules these matrix elements should be subtracted leading to a reduced ee -> ee cross section.

Thanks for the reply. But as soon as you've got the free photon I don't understand why it would favor (or disfavor) an electron positron pair rather than a muon or tau pair. The argument would just be if the energy is much greater than twice the muon rest mass the muon and electron are the...

Homework Statement Why does the ratio: \frac{σ(e^- + e^+ \rightarrow μ^- + μ^+) }{σ(e^- + e^+ \rightarrow τ^- + τ^+)} tend to unity at high energies and would you expect the same for: \frac{σ(e^- + e^+ \rightarrow μ^- + μ^+) }{σ(e^- + e^+ \rightarrow e^- + e^+)} The attempt at...

Thanks a lot for such a detailed reply! That really helps my understanding of wave function symmetry, especially in the 3 particle case. Is there a reason the baryons are antisymmetric in color? Couldn't we have the wave function symmetric in color and antisymmetric in flavor and spin?

I've just been accepted for a PhD here in the UK (in high energy physics) so I know a little about the application system and what is considered important. I don't know anything about applying to the rest of Europe though! I applied for both experimental and theoretical PhDs and I know for sure...

Thanks! That makes sense, I didn't think about the wavefunction symmetry at all.

I'm a little confused about what is actually meant by the JP = 1/2 + octet. I'm pretty sure it means the particles must have spin 1/2 in the ground state (l=0) and an even parity but what I'm confused over is the absence of an sss, uuu or ddd state. I understand that this would give I3 = 3/2...

Thanks. I think I understand that. Am I right in thinking that if there was no CP violation the mass eigenstates would have the same mass and therefore there would be no kaon oscillations?

Thanks! That makes sense. So I guess the \Delta m refers to the difference in mass of the modified states coupling to the weak interaction (a superposition of K0 and K0-bar)?

Hey, I'm trying to get my head around neutral Kaon oscillations. As far as I understand it neutral Kaons can change between K^0 and \overline{K^0} as they propagate. Going through the quantum mechanics of this implies that this oscillation must be facilitated by a mass difference between the...

Thanks. It was an odd small part of an exam question when my module had only covered examples up to 3rd rank.

Hi, Can somebody give me an example of a rank 4 tensor in physics? Thanks.

Homework Statement A capacitor of capacitance C is connected in parallel with a resistor of R ohms impedance. Calculate the size of the peak to peak voltage of the ripple produced relative to the peak output voltage Vp. Homework Equations Q=CV dQ/dt = I V=IR Vc=Vpe-t/RC (am i allowed to use...