It’s common shorthand for 4 spatial dimensions, and 1 time-dimension, stressing that there is indeed a split, and that not all dimensions are equivalent. Perhaps, given the compactification of 1, it should be 3+1+1, but I’ve never seen that used.
Thanks, I wasn’t sure whether the +1 was the time or the compact dimension.
It’s common shorthand for 4 spatial dimensions, and 1 time-dimension, stressing that there is indeed a split, and that not all dimensions are equivalent. Perhaps, given the compactification of 1, it should be 3+1+1, but I’ve never seen that used.
Thanks, I wasn’t sure whether the +1 was the time or the compact dimension.