- #1
etotheipi
Short, probably stupid, question; what does this left-right arrow ##a \leftrightarrow b## at the bottom-right mean? [It's this paper for ref.]
Does it just mean the last term repeated, except this time with ##a## and ##b## indices exchanged? Thanks.
Does it just mean the last term repeated, except this time with ##a## and ##b## indices exchanged? Thanks.