In the book 'Lie Groups, Lie Algebras, and Representations' written by Brian C. Hall, a matrix Lie group G is 'simply connected' if it is path-connected and for every continuous path $A(t),0\le t\le 1$, lying in G and with $A(0)=A(1)$, there exists a continuous function $A(s,t),0\le s,t\le 1$, taking values in G and having the following properties: (1) $A(s,0)=A(s,1)$ for all s, (2) $A(0,t)=A(t)$, and (3) $A(1,t)=A(1,0)$ for all t.
But on topology textbooks, it needs to choose a fixed base point, and the loop converges to that base point. While in the previous book, the loop can converge to any point in the loop and a base point is not needed. Are these two definitions equivalent?
Yes, they are equivalent under the assumption that the space is path-connected. Of course, in general they are not equivalent.