Recent content by The black vegetable

To answer my own question, I think it turns out to be the same as the scaler field loop but with the opposite sign ,Klein Gordon equation is just Dirac Equation squared, So just replace it with the square root Klein Gordon equation, then because it's log bring the exponent (1/2) in front and...

Following the method by Peskin and Shroesder 11.4 Trying to calculate the vacuum energy of a fermion. If my method is correct so far the next step is to find gamma function , the formula I have for gamma fuctions doesn't match this equation. Can anyone help with the next step? Starting with the...

Okay thanks for your help

Ok Thanks, very helpful I have some notes on Grassmann variables that I will revisit, but can I start as Peskin and Schroeder did with a new Lagrangian but this time containing a scaler field and a fermionic field expanding both ## \phi \rightarrow \phi _{cl}+\eta ## ##\Psi \rightarrow \Psi...

I am reading Peskin and Schroeder Section 11.4. They derive a formula for the effective action p.372 Equation 11.63 using a scalar field interaction, They use this formula to determine the effective potential. If I want to do the same for a Lagrangian with with a scalar field and fermion...

ok thanks , i tried to look up mode expansion of dirac field, couldn't find how it gives the vertex function,

I am looking at Srednicki ch 64 , how does equation 64.1 follow from 64.3 as stated. Explicitly in QED how does ## u_{s'}(p')V^{u}(p',p)u_{s}(p)=e\bar{u'}(F_{1}(q^{2})\gamma ^{u}-\frac{i}{m}F_{2}(q^{2})S^{uv}q_{v})u ## follow from the quantum action ## \Gamma =\int d^{4}x(eF_{1}\bar{\varphi...

That's great thanks for this :)

Hi When calculating the superficial degree of divergence do you only do it for diagrams with closed loops? Many thanks :)

Okay thanks, was thinking I could do it purely by matrices but will have to look more into it as I'm not familiar with some other terms you used :)

I have in my notes the charge conjugation operator converts the spinnor into its complex conjugate , ## C\begin{pmatrix} \varepsilon \\ \eta \end{pmatrix}=\begin{pmatrix} \varepsilon^{*}{} \\ \eta ^{*} \end{pmatrix}##when applied to gamma matrix from dirac equation does it do the same...

Hi In the last sentence I mean you do include constant terms like I have done when taking the product above?

Is this correct? If not any hints on how to find Many thanks

ah that's great thank you, I will look into binomial expansion, never met it before :)

Maybe I'm just being stupid, missing something simple ? How do you get from the top two equations to the second equation? Many thanks