This setup can output the trivial solution of u_i being all 0s.
in practice the right side is not always 0, so we may have a solution?
This setup may not consider boundary conditions explicitly.
Rank deficient because each column is a linear combination of others.
Not full rank
all 0s is always a solution
You can have all 0's, as well as you can offset the solutions by any constant.
all 0 is a unsatisfying solution
All 0s is a solution
It is possible that there is an all zero's solution
all 0s
may not have a nontrivial solution
all 0
This setup can output the trivial solution of u_i being all 0s.
in practice the right side is not always 0, so we may have a solution?
This setup may not consider boundary conditions explicitly.
Rank deficient because each column is a linear combination of others.
Not full rank
all 0s is always a solution
You can have all 0's, as well as you can offset the solutions by any constant.
all 0 is a unsatisfying solution
All 0s is a solution
It is possible that there is an all zero's solution
all 0s
may not have a nontrivial solution
all 0