Why Does the Free-Field Dirac Hamiltonian Calculation Seem Incorrect?

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SUMMARY

The discussion centers on the calculation of the matrix element involving the free-field Dirac Hamiltonian, represented as H = ∫(d³k/(2π)³)Σs(âc+s(k)âc s(k)+ (âd+s(k)âd s(k)). The user, Jonathan, initially encounters nonsensical results when evaluating the expression <-,p',v';+,q',r'|H|-,p,v;+,q,r>. He identifies errors in calculating the operator pieces, particularly in the terms involving the creation and annihilation operators. Ultimately, he resolves his confusion by referencing a similar problem, leading to a clearer understanding of the calculation process.

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jonbones
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Homework Statement



This is a simple problem I thought of and I'm get a nonsensical answer.
I'm not sure where I'm going wrong in the calculation.

Find the value of <-,p',v';+,q',r'|H|-,p,v;+,q,r>
where H is the free-field Dirac Hamiltonian

H = [itex]\int[/itex](d3k/(2\pi)3)[itex]\sum[/itex]s([itex]\widehat{c}[/itex]+s(k)[itex]\widehat{c}[/itex]s(k)+([itex]\widehat{d}[/itex]+s(k)[itex]\widehat{d}[/itex]s(k))

Homework Equations



<p|q> = 2Ep(2\pi)3[itex]\delta[/itex](3)(p-q)

|+,q,r> = (2Eq)1/2[itex]\widehat{d}[/itex]+r(q)|0>

|-,p,v> = (2Ep)1/2[itex]\widehat{c}[/itex]+v(p)|0>

The Attempt at a Solution



<-,p',v';+,q',r'|H|-,p,v;+,q,r> = <-,p',v';+,q',r'|Hc|-,p,v;+q,r>+<-,p',v';+q',r'|Hd|-,p,v;+,q,r>

<-,p',v';+q',r'|Hc|-,p,v;+,q,r> = [itex]\int[/itex](d3k/{(2\pi)3)[itex]\sum[/itex]s<-,p',v';+,q',r'|[itex]\widehat{c}[/itex]+s(k)[itex]\widehat{c}[/itex]s(k)|-,p,v;+q,r>
= [itex]\int[/itex](d3k/{(2\pi)3)[itex]\sum[/itex]s<-,p',v'|[itex]\widehat{c}[/itex]+s(k)[itex]\widehat{c}[/itex]s(k)|-,p,v><+,q',r'|+q,r>
= 1/(2\pi)3(2Ev)-1<-,p',v'|-,p,v><+q',r'|+q,r>
= (2\pi)32Eq[itex]\delta[/itex](3)(v-v')[itex]\delta[/itex](3)(q-q')

Similarly, <-,p',v';+q',r'|Hd|-,p,v;+,q,r> = (2\pi)32Ev[itex]\delta[/itex](3)(v-v')[itex]\delta[/itex](3)(q-q')

I know these are wrong since <-,p',v';+q',r'|Hc|-,p,v;+,q,r> [itex]\propto[/itex]Ep and <-,p',v';+q',r'|Hd|-,p,v;+,q,r> [itex]\propto[/itex]Eq.

I'm pretty sure I'm calculating the operator pieces like <-,p',v';+,q',r'|[itex]\widehat{c}[/itex]+s(k)[itex]\widehat{c}[/itex]s(k)|-,p,v;+q,r> incorrectly but I'm not sure where I'm going wrong.

-- Jonathan
 
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Nevermind, I found a solution to a similar problem and now I know what I did wrong.
 

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