I find it to be fairly standard, but maybe this is because this is how I learned it all those decades ago.
But, what do these symbols mean, and from where does the relation come?
Think of it like this:
$$\{\sigma^{\mu},\sigma^{\nu} \} = 2 \eta^{\mu \nu} I,$$
where ##I## is the ##2 \times 2## identity matrix, and the ##\eta^{\mu \nu}## are the components of the ##3 \times 3## matrix ##\eta = \mathrm{diag}(-1,1,1)##.
I do not have time to read this long paper, but the abstract is fascinating.
Doesn't this say that nature could possibly favour one Pin group over the other?
Also, note that one of the authors is Cecile Dewitt-Morette.
I wrote my first programs (which used Fortran) without typing. I posted the following in a restrict forum, so I'll share it more widely here.
My "back in the day" story.
Fortran was my first progamming language, which I leaned in two high school computer science courses from '76 to '78. My...
My wife being one of them.
My wife has four degrees, each from a different Canadian university,
She does not have a Ph.D., and she has four degrees only because of changing career goals, physics -> engineering-> teaching. She has a B.Sc. in Physics (York), an M.Sc. in Physics (Windsor), and...
Phys. Rev. D 2014
https://arxiv.org/abs/1403.4591
Phys. Rev. D 2018
https://arxiv.org/abs/1712.05364
Phys. Rev. D 2020
https://arxiv.org/abs/1911.07082
Phys. Rev. D is a high-impact, high-quality research journal.
One way to avoid this is to note (by, e.g., looking at the graph) that the integrand is even about ##\pi##. It is easily shown algebraically that the integrand evaluated at ##\pi - x## is the same as the integrand evaluated at ##\pi + x##. Consequently, ##\int_0^{2\pi} = 2 \int_0^{\pi}##.
I know how to do this! Find a set of apples and oranges. Take the free vector space on this set of apples and oranges. Now apples and oranges can be mixed, i..e, it is possible to take linear combinations of apples and oranges.
At about the level of Griffiths, there is "QUANTUM MECHANICS A Paradigms Approach" by David McIntyre. This book has more emphasis on Dirac notation than does Griffiths, which I like.