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Linear Algebra - Sebastian Pancratz

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C <br />

e1, . . . , en ψ <br />

⎛ ⎞<br />

d1 0<br />

⎜<br />

⎝<br />

⎟<br />

⎠ .<br />

0 dn<br />

d1, . . . , dr = 0 di = 0 i > r <br />

ej 1 √ ej 1 ≤ j ≤ r ψ <br />

dj<br />

<br />

Ir 0<br />

.<br />

0 0<br />

P T AP = <br />

Ir 0<br />

0 0 <br />

P rank A = r<br />

V V <br />

ψ : V × V → C <br />

u ∈ V v ↦→ ψ(u, v) <br />

u, v ∈ V ψ(u, v) =<br />

¯<br />

ψ(v, u)<br />

ψ <br />

ψ(u, v) =<br />

ψ(u, λ1v1 + λ2v2) = λ1ψ(u, v1) + λ2ψ(u, v2)<br />

ψ(λ1u1 + λ2u2, v) = ¯ λ1ψ(u1, v) + ¯ λ2ψ(u2, v)<br />

¯<br />

ψ(v, u)<br />

<br />

<br />

ψ V <br />

Q : V → C Q(v) = ψ(v, v) Q(v) ∈ R v ∈ V <br />

Q(λv) = |v| 2 Q(v) ψ <br />

ψ(u, v) = 1<br />

4 (Q(u + v) − Q(u − v) − iQ(u + iv) + iQ(u − iv))<br />

B = {v1, . . . , vn} V ψ B [ψ]B =<br />

(ψ(vi, vj)) = A ψ(u, v) = [ψ] T<br />

B [ψ]B[v]B A = ĀT <br />

¯ P T AP <br />

P <br />

ψ V <br />

B V ψ <br />

⎛<br />

Ip<br />

⎝ −Iq<br />

⎞<br />

0<br />

⎠<br />

0 0<br />

p q ψ B <br />

v1, . . . , vn <br />

n<br />

Q( ξivi) = |ξ1| 2 + · · · + |ξp| 2 − |ξp+1| 2 − · · · − |ξp+q| 2 .<br />

i=1

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