# Calculate current

1. Jan 4, 2014

### aaaa202

1. The problem statement, all variables and given/known data
In an exercise I am given the attached expression for the current. The functions f1 and f2 are fermi functions centered around the chemical potentials μ1 and μ2.
I am then asked to study this expression in the limit μ1-μ2 -> 0 and γ1->0,γ2->0.
Specifically I am supposed to show that the current is proportional to df/dE. I am unsure of how to do it though. I approximated the integral to be the integral of a delta function and then taylorexpanded f around the small parameter μ1-μ2 as attached. Do you think this is the way to do it, or what is meant by df/dE?

2. Relevant equations

3. The attempt at a solution
attached

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