I am trying to solve the following optimization problem for the vector $ y $, where $ A_i $ are some given matrix (maybe low rank) and $ x_i $ are unconstrained $$ \min_{y, x_i} \sum_{i=1}^J || y - A_i x_i ||_2^2, \;\;\;\;\text{ subject to } ||y||_2 = 1, \;\; || A_i x_i ||_2 = 1 \;\; \forall i$$
I believe that solving the following problem, where I drop the constraints on the projections, would give the same solution for $ y $ but I am having a hard time proving it.
$$ \min_{y, x_i} \sum_{i=1}^J || y - A_i x_i ||_2^2, \;\;\;\;\text{ subject to } ||y||_2 = 1$$ To be clear, I only care about the value of $ y $ and not about the actual values of $ x_i $. I know that the values of $ x_i $ are going to be different in the two problem but is there a proof/disproof that the values of $ y $ are going to be the same ?