# Left spinors in GUT theories

Why in every single text about GUT theories only the left spinors are used? Why use the conjugate of the spinor instead of the spinor itself? Is it just a another historic definition?

Thanks

Why in every single text about GUT theories only the left spinors are used? Why use the conjugate of the spinor instead of the spinor itself? Is it just a another historic definition?

I do not know much about GUT theories, but it might be related to the fact we often have majorana particles and it is easier the formulate the them with left spinor, anti-particles and conjugate than with left and right spinors ?