The idea of a perturbation series in powers of a coupling α≪1 (for example, the fine structure constant in QED) make sense if the contribution of (n+1)th term in the series is smaller than the contribution of nth term. Now, the tree-level amplitude for a QED process is finite. However, at O(α2), the contribution from the S-matrix to the amplitude is divergent (all diagrams with loops are divergent because loop momentum can be arbitrarily high). How does perturbation theory make sense in QED (or in any quantum field theory)?
Subscribe to:
Post Comments (Atom)
-
I have an hydrogenic atom, knowing that its ground-state wavefunction has the standard form ψ=Ae−βrwith $A = \frac{\bet...
-
At room temperature, play-dough is solid(ish). But if you make a thin strip it cannot just stand up on it's own, so is it still solid? O...
-
Sometimes I am born in silence, Other times, no. I am unseen, But I make my presence known. In time, I fade without a trace. I harm no one, ...
-
I want to know what happens to the space a black hole crosses over as our galaxy travels through space.
-
I'm sitting in a room next to some totally unopened cans of carbonated soft drinks (if it matters — the two affected cans are Coke Zero...
-
Small vessels generally lean into a turn, whereas big vessels lean out. Why do ships lean to the outside, but boats lean to the inside of a ...
-
What exactly are the spikes, or peaks and valleys, caused by in pictures such as these Wikipedia states that "From the point of view of...
No comments:
Post a Comment