Recent content by SteDolan

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    Using E-L equations to get through a mountain range

    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...
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    High energy electron positron branching ratios.

    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.
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    High energy electron positron branching ratios.

    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...
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    High energy electron positron branching ratios.

    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...
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    Quark Model Spectroscopic Notation

    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?
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    Admissions Ph.D. admission in Europe with average grades, no recommendations

    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...
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    Quark Model Spectroscopic Notation

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

    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...
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    How to maintain CPT invariance in Kaon oscillations

    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?
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    How to maintain CPT invariance in 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)?
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    How to maintain CPT invariance in Kaon oscillations

    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...
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    Understanding Physics with a Rank 4 Tensor Example

    Thanks. It was an odd small part of an exam question when my module had only covered examples up to 3rd rank.
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    Understanding Physics with a Rank 4 Tensor Example

    Hi, Can somebody give me an example of a rank 4 tensor in physics? Thanks.
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    Half wave rectifier Ripple Voltage

    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...
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