The asymptotic restriction problem for tensors is to decide, given $s$ and $t$, whether the nth tensor power of can be obtained from $(n+o(n))$th t by applying linear maps legs (this we call restriction), when $n$ goes infinity. In this context, Volker Strassen, striving understand complexity matrix multiplication, introduced in 1986 spectrum tensors. Essentially, a family $X$, closed under dir...