Notation for Propability Amplitudes

Question

I've recently stumbled upon a certain piece of notation that doesn't quite seem clear to me. When discussing the amplituhedron, my teacher mentioned the relation between the volume and the amplitude scattering, and then he wrote the following on the board: $$[1-,\,1+,\,3-,\,3+]$$ I assume these are probability amplitudes, but I don't quite what the integers and the signs mean.

This post imported from StackExchange Physics at 2014-03-07 16:34 (UCT), posted by SE-user Demian Licht

Comments

I know nothing about amplituhedra, so this may be entirely wrong: sometimes the notation 1+ is used to denote a real number that is indefinitely close to 1. as in lim (x-->O+) to mean the limit as x approaches zero from the right.

This post imported from StackExchange Physics at 2014-03-07 16:34 (UCT), posted by SE-user garyp

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I would hope the instructor didn't just write that down in vacuo - was there some additional context?

This post imported from StackExchange Physics at 2014-03-07 16:34 (UCT), posted by SE-user Chris White