Register to reply

How can we expand product of two currents into series?

by ndung200790
Tags: currents, expand, product, series
Share this thread:
Feb28-12, 08:40 PM
P: 520
Please teach me this:
In QFT book of Peskin&Schroeder write:
I do not know how to expand the product into this series.
Thank you very much for your kind helping.
Phys.Org News Partner Physics news on
Scientists uncover clues to role of magnetism in iron-based superconductors
Researchers find first direct evidence of 'spin symmetry' in atoms
X-ray laser probes tiny quantum tornadoes in superfluid droplets
Feb28-12, 11:10 PM
P: 194
Oh dear... I would love to know the answer to this one.

The best answer I have been given to date is: think of all the operators that transforms in the same way as the product of two currents, and those will be the ones appearing in the expansion.

It would be so awesome if someone could give a constructive algorithm for generating the series expansion for the product of two currents (or for that matter, for the non-local product of any two local operators).
Feb29-12, 05:35 AM
P: 520
Given the series,they say that the coefficients in the series can be calculate by Feynman diagrams.Then I do not know how to give the Feynman diagrams for the coefficients.

Mar1-12, 12:02 AM
P: 520
How can we expand product of two currents into series?

Why is the coefficient of operator 1 being the sum of diagrams with no external legs other than the current insertions?
Mar1-12, 09:22 PM
P: 520
It seems that there is ''some arbitrary'' in OPE.We can ''adjust'' the coefficients in the series according with ''situation''.Is that correct?
Mar3-12, 12:57 AM
P: 520
It seem to me that we can expand product of operators by Wick theorem and Taylor series?

Register to reply

Related Discussions
Why is hadronic vacum polarization to be a matrix element of product of currents? Quantum Physics 1
How to expand f(x)=x^2, -pi<x<pi as fourier series Calculus & Beyond Homework 2
Expand the function f(x) = x^3 in a Fourier sine series Calculus & Beyond Homework 19
Why do fluids expand with heat? explaining covection currents General Physics 9
Should I expand as a power series and then integrate or is there an elegant method? Calculus & Beyond Homework 2