Fiber-Connectivity of Almost-Toric Systems in Four-Dimension
In this paper, we study the fiber connectivity of proper almost-toric systems $Φ$ on connected four-dimensional symplectic manifolds. Using Morse--Kirwan theory, we establish three sufficient conditions for fiber connectivity. These results generalize and extend the fiber connectivity results of Pelayo, Ratiu, and Vu Ngoc (2015) by relaxing some of their hypotheses.