Exotic $\mathbb{G}_a$-quotients of $SL_2 \times \mathbb{A}^1$
Résumé
Every deformed Koras–Russell threefold of the first kind Y={xnz=ym−tr+xh(x,y,t)} in A4 is the algebraic quotient of proper Zariski locally trivial Ga-action on SL2×A1.