Double-Real-Virtual and Double-Virtual-Real Corrections to the Three-Loop Thrust Soft Function

We compute the ${\cal O}(\alpha_s^3)$ double-real-virtual (RRV) and double-virtual-real (VVR) soft contributions to the thrust/zero-jettiness event shape. The result clears up one of the most stubborn obstacles toward the complete ${\cal O}(\alpha_s^3)$ thrust soft function. The results presented here serve as the key input to realize the next-to-next-to-next-to-leading logarithmic prime (N${}^3$LL') % and even the next-to-next-to-next-to-next-to-leading logarithmic (N${}^4$LL) resummation of the thrust event shape. The obtained results also constitute the important ingredients of the $N$-jettiness-subtraction scheme at next-to-next-to-next-to-leading order (N${}^3$LO).