Lecture 2

Subspace approximation: formulation with bases
Uα = span {b (α)
i
b (α)
ℓ
=
i=1 j=1
: 1 ≤ i ≤ rα}
rα rα
�1
�2
c (α,ℓ)
ij b (α1)
i ⊗ b (α2)
j
Coefficients c (α,ℓ)
form the matrices C (α,ℓ) .
ij
Final representation of v is
v =
r D� c (D)
i
b(D)
i , (usually with r D = 1).
(α1, α2 sons of α ∈ T D).