Amplitudes for left-handed strings

Understand

We consider a class of string-like models introduced previously where all modes are left-handed, all states are massless, T-duality is manifest, and only a finite number of orders in the string tension can appear.

• These theories arise from standard string theories by a singular gauge limit and associated change in worldsheet boundary conditions.
• In this paper we show how to calculate amplitudes by using the gauge parameter as an infrared regulator.
• The amplitudes produce the Cachazo-He-Yuan delta-functions after some modular integration; the Mason-Skinner string-like action and amplitudes arise from the zero-tension (infinite-slope) limit.