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Description: The norm of a continuous linear Hilbert space operator exists. Theorem 3.5(i) of Beran p. 99. (Contributed by NM, 5-Feb-2006) (Proof shortened by Mario Carneiro, 17-Nov-2013) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | nmcopex.1 | ⊢ 𝑇 ∈ LinOp | |
| nmcopex.2 | ⊢ 𝑇 ∈ ContOp | ||
| Assertion | nmcopexi | ⊢ ( normop ‘ 𝑇 ) ∈ ℝ |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | nmcopex.1 | ⊢ 𝑇 ∈ LinOp | |
| 2 | nmcopex.2 | ⊢ 𝑇 ∈ ContOp | |
| 3 | ax-hv0cl | ⊢ 0ℎ ∈ ℋ | |
| 4 | 1rp | ⊢ 1 ∈ ℝ+ | |
| 5 | cnopc | ⊢ ( ( 𝑇 ∈ ContOp ∧ 0ℎ ∈ ℋ ∧ 1 ∈ ℝ+ ) → ∃ 𝑦 ∈ ℝ+ ∀ 𝑧 ∈ ℋ ( ( normℎ ‘ ( 𝑧 −ℎ 0ℎ ) ) < 𝑦 → ( normℎ ‘ ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) ) < 1 ) ) | |
| 6 | 2 3 4 5 | mp3an | ⊢ ∃ 𝑦 ∈ ℝ+ ∀ 𝑧 ∈ ℋ ( ( normℎ ‘ ( 𝑧 −ℎ 0ℎ ) ) < 𝑦 → ( normℎ ‘ ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) ) < 1 ) |
| 7 | hvsub0 | ⊢ ( 𝑧 ∈ ℋ → ( 𝑧 −ℎ 0ℎ ) = 𝑧 ) | |
| 8 | 7 | fveq2d | ⊢ ( 𝑧 ∈ ℋ → ( normℎ ‘ ( 𝑧 −ℎ 0ℎ ) ) = ( normℎ ‘ 𝑧 ) ) |
| 9 | 8 | breq1d | ⊢ ( 𝑧 ∈ ℋ → ( ( normℎ ‘ ( 𝑧 −ℎ 0ℎ ) ) < 𝑦 ↔ ( normℎ ‘ 𝑧 ) < 𝑦 ) ) |
| 10 | 1 | lnop0i | ⊢ ( 𝑇 ‘ 0ℎ ) = 0ℎ |
| 11 | 10 | oveq2i | ⊢ ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) = ( ( 𝑇 ‘ 𝑧 ) −ℎ 0ℎ ) |
| 12 | 1 | lnopfi | ⊢ 𝑇 : ℋ ⟶ ℋ |
| 13 | 12 | ffvelcdmi | ⊢ ( 𝑧 ∈ ℋ → ( 𝑇 ‘ 𝑧 ) ∈ ℋ ) |
| 14 | hvsub0 | ⊢ ( ( 𝑇 ‘ 𝑧 ) ∈ ℋ → ( ( 𝑇 ‘ 𝑧 ) −ℎ 0ℎ ) = ( 𝑇 ‘ 𝑧 ) ) | |
| 15 | 13 14 | syl | ⊢ ( 𝑧 ∈ ℋ → ( ( 𝑇 ‘ 𝑧 ) −ℎ 0ℎ ) = ( 𝑇 ‘ 𝑧 ) ) |
| 16 | 11 15 | eqtrid | ⊢ ( 𝑧 ∈ ℋ → ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) = ( 𝑇 ‘ 𝑧 ) ) |
| 17 | 16 | fveq2d | ⊢ ( 𝑧 ∈ ℋ → ( normℎ ‘ ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) ) = ( normℎ ‘ ( 𝑇 ‘ 𝑧 ) ) ) |
| 18 | 17 | breq1d | ⊢ ( 𝑧 ∈ ℋ → ( ( normℎ ‘ ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) ) < 1 ↔ ( normℎ ‘ ( 𝑇 ‘ 𝑧 ) ) < 1 ) ) |
| 19 | 9 18 | imbi12d | ⊢ ( 𝑧 ∈ ℋ → ( ( ( normℎ ‘ ( 𝑧 −ℎ 0ℎ ) ) < 𝑦 → ( normℎ ‘ ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) ) < 1 ) ↔ ( ( normℎ ‘ 𝑧 ) < 𝑦 → ( normℎ ‘ ( 𝑇 ‘ 𝑧 ) ) < 1 ) ) ) |
| 20 | 19 | ralbiia | ⊢ ( ∀ 𝑧 ∈ ℋ ( ( normℎ ‘ ( 𝑧 −ℎ 0ℎ ) ) < 𝑦 → ( normℎ ‘ ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) ) < 1 ) ↔ ∀ 𝑧 ∈ ℋ ( ( normℎ ‘ 𝑧 ) < 𝑦 → ( normℎ ‘ ( 𝑇 ‘ 𝑧 ) ) < 1 ) ) |
| 21 | 20 | rexbii | ⊢ ( ∃ 𝑦 ∈ ℝ+ ∀ 𝑧 ∈ ℋ ( ( normℎ ‘ ( 𝑧 −ℎ 0ℎ ) ) < 𝑦 → ( normℎ ‘ ( ( 𝑇 ‘ 𝑧 ) −ℎ ( 𝑇 ‘ 0ℎ ) ) ) < 1 ) ↔ ∃ 𝑦 ∈ ℝ+ ∀ 𝑧 ∈ ℋ ( ( normℎ ‘ 𝑧 ) < 𝑦 → ( normℎ ‘ ( 𝑇 ‘ 𝑧 ) ) < 1 ) ) |
| 22 | 6 21 | mpbi | ⊢ ∃ 𝑦 ∈ ℝ+ ∀ 𝑧 ∈ ℋ ( ( normℎ ‘ 𝑧 ) < 𝑦 → ( normℎ ‘ ( 𝑇 ‘ 𝑧 ) ) < 1 ) |
| 23 | nmopval | ⊢ ( 𝑇 : ℋ ⟶ ℋ → ( normop ‘ 𝑇 ) = sup ( { 𝑚 ∣ ∃ 𝑥 ∈ ℋ ( ( normℎ ‘ 𝑥 ) ≤ 1 ∧ 𝑚 = ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ) } , ℝ* , < ) ) | |
| 24 | 12 23 | ax-mp | ⊢ ( normop ‘ 𝑇 ) = sup ( { 𝑚 ∣ ∃ 𝑥 ∈ ℋ ( ( normℎ ‘ 𝑥 ) ≤ 1 ∧ 𝑚 = ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ) } , ℝ* , < ) |
| 25 | 12 | ffvelcdmi | ⊢ ( 𝑥 ∈ ℋ → ( 𝑇 ‘ 𝑥 ) ∈ ℋ ) |
| 26 | normcl | ⊢ ( ( 𝑇 ‘ 𝑥 ) ∈ ℋ → ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ∈ ℝ ) | |
| 27 | 25 26 | syl | ⊢ ( 𝑥 ∈ ℋ → ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ∈ ℝ ) |
| 28 | 10 | fveq2i | ⊢ ( normℎ ‘ ( 𝑇 ‘ 0ℎ ) ) = ( normℎ ‘ 0ℎ ) |
| 29 | norm0 | ⊢ ( normℎ ‘ 0ℎ ) = 0 | |
| 30 | 28 29 | eqtri | ⊢ ( normℎ ‘ ( 𝑇 ‘ 0ℎ ) ) = 0 |
| 31 | rpcn | ⊢ ( ( 𝑦 / 2 ) ∈ ℝ+ → ( 𝑦 / 2 ) ∈ ℂ ) | |
| 32 | 1 | lnopmuli | ⊢ ( ( ( 𝑦 / 2 ) ∈ ℂ ∧ 𝑥 ∈ ℋ ) → ( 𝑇 ‘ ( ( 𝑦 / 2 ) ·ℎ 𝑥 ) ) = ( ( 𝑦 / 2 ) ·ℎ ( 𝑇 ‘ 𝑥 ) ) ) |
| 33 | 31 32 | sylan | ⊢ ( ( ( 𝑦 / 2 ) ∈ ℝ+ ∧ 𝑥 ∈ ℋ ) → ( 𝑇 ‘ ( ( 𝑦 / 2 ) ·ℎ 𝑥 ) ) = ( ( 𝑦 / 2 ) ·ℎ ( 𝑇 ‘ 𝑥 ) ) ) |
| 34 | 33 | fveq2d | ⊢ ( ( ( 𝑦 / 2 ) ∈ ℝ+ ∧ 𝑥 ∈ ℋ ) → ( normℎ ‘ ( 𝑇 ‘ ( ( 𝑦 / 2 ) ·ℎ 𝑥 ) ) ) = ( normℎ ‘ ( ( 𝑦 / 2 ) ·ℎ ( 𝑇 ‘ 𝑥 ) ) ) ) |
| 35 | norm-iii | ⊢ ( ( ( 𝑦 / 2 ) ∈ ℂ ∧ ( 𝑇 ‘ 𝑥 ) ∈ ℋ ) → ( normℎ ‘ ( ( 𝑦 / 2 ) ·ℎ ( 𝑇 ‘ 𝑥 ) ) ) = ( ( abs ‘ ( 𝑦 / 2 ) ) · ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ) ) | |
| 36 | 31 25 35 | syl2an | ⊢ ( ( ( 𝑦 / 2 ) ∈ ℝ+ ∧ 𝑥 ∈ ℋ ) → ( normℎ ‘ ( ( 𝑦 / 2 ) ·ℎ ( 𝑇 ‘ 𝑥 ) ) ) = ( ( abs ‘ ( 𝑦 / 2 ) ) · ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ) ) |
| 37 | rpre | ⊢ ( ( 𝑦 / 2 ) ∈ ℝ+ → ( 𝑦 / 2 ) ∈ ℝ ) | |
| 38 | rpge0 | ⊢ ( ( 𝑦 / 2 ) ∈ ℝ+ → 0 ≤ ( 𝑦 / 2 ) ) | |
| 39 | 37 38 | absidd | ⊢ ( ( 𝑦 / 2 ) ∈ ℝ+ → ( abs ‘ ( 𝑦 / 2 ) ) = ( 𝑦 / 2 ) ) |
| 40 | 39 | adantr | ⊢ ( ( ( 𝑦 / 2 ) ∈ ℝ+ ∧ 𝑥 ∈ ℋ ) → ( abs ‘ ( 𝑦 / 2 ) ) = ( 𝑦 / 2 ) ) |
| 41 | 40 | oveq1d | ⊢ ( ( ( 𝑦 / 2 ) ∈ ℝ+ ∧ 𝑥 ∈ ℋ ) → ( ( abs ‘ ( 𝑦 / 2 ) ) · ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ) = ( ( 𝑦 / 2 ) · ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ) ) |
| 42 | 34 36 41 | 3eqtrrd | ⊢ ( ( ( 𝑦 / 2 ) ∈ ℝ+ ∧ 𝑥 ∈ ℋ ) → ( ( 𝑦 / 2 ) · ( normℎ ‘ ( 𝑇 ‘ 𝑥 ) ) ) = ( normℎ ‘ ( 𝑇 ‘ ( ( 𝑦 / 2 ) ·ℎ 𝑥 ) ) ) ) |
| 43 | 22 24 27 30 42 | nmcexi | ⊢ ( normop ‘ 𝑇 ) ∈ ℝ |