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The following is taken from Bjorken and Drell, Relativistic Quantum Mechanics (1964), pp. 5-6: So the problem with the Klein-Gordon...

If doesn't work in relativistic context. For example, if you apply it to Klein-Gordon equation then probability is not conserved.

The main problem is how to define probability density for particle positions. QFT avoids that problem by saying that the theory at the...

I know people who still use Windows XP, without any problems. Hence I do not expect problems with my Windows 10. I will switch to...

https://en.wikipedia.org/wiki/Yang_Chen-Ning ( photo from http://insti.physics.sunysb.edu/~yang/ )...

If the fields of the Standard Model are not fundamental, then what is? We don't know. It could be some other fields, or it could be...

I disagree https://www.physicsforums.com/threads/simulating-physics-the-current-status-of-lattice-field-theories.1014629/#post-6626056

There are two kinds on infinities in QFT, UV infinities and IR infinities. UV infinities are due to using a continuum (in both space and...

Yes, this is the meaning of that product symbol with two subscripts.

Of course. All have erratas.

Speaking of Folland's books, they are notorious for typos. Here's the errata for his 1st edition of the QFT book.

So I found out that this theory applies to the other sex in a similar way as well:

Equation (4) is correct in Coulomb gauge, where equation (3) holds everywhere, not only on the equatorial plane.