FA 2017/7/25 Both sides of the answer sheet can be used.
1 Describe the Hahn-Banach theorem and explain how big the dual of a normed space is.
2 Describe the open mapping theorem on linear operators and show that all the complete norms on a vector space V are equivalent.
3 Define a linear operator T on the Hilbert space ℓ
2by (T ξ)
n=
1nξ
n(n ≥ 1).
(i) Show that T is a hermitian operator.
(ii) Calculate the operator norm ∥ T ∥ of T . (iii) Describe the spectrum of T with the reason.
Glossary:
dual space
双対空間normed space
ノルム空間open mapping
開写像complete norm
完備なノルムlinear operator
線型作用素operator norm
作用素ノルムhermitian operator
エルミート作用素spectrum
スペクトル(集合)1