検索:学位「2光子偏光分光法によるCuCl励起子及び励起子分子系の研究」(東大物理)1985 で下記がヒットする 学位論文そのものは ヒットしないが 2光子偏光分光法によるCuCl励起子 ・励起子分子系の研究 桑田真 著 · 1982 より (桑田は、五神の旧姓) <参考文献> 1) M. Kuwata, T. Mita and N. Nagasawa : Polarization Rotation Effects associated with the Two-photon Transition of Ti-Excitonic Molecules in CuCl, Opt. Commun. 40 (1982) 208. 2) M. Kuwata, T. Mita and N. Nagasawa : Renormalization of Polaritons due to the Formation of Excitonic Molecules in CuCl ; An Experimental Aspect, SoHd State Commun. 40 (1982) 911. 3) M. Kuwata and N. Nagasawa : Self-Induced Polarization Rotation Effect of an Elliptically Polarized Beam in CuCl, J. Phys. Soc. Japan submitted. で、投稿論文3つあるから、ここらを読め
http://www.nature.com/articles/d41586-025-00938-y 75% of US scientists who answered Nature poll consider leaving More than 1,600 readers answered our poll; many said they were looking for jobs in Europe and Canada.
>>734 補足 >4 Horn, Roger A.; Johnson, Charles R. (2013). Matrix Analysis, second edition. Cambridge University Press. ISBN 9780521839402.
これの海賊版PDFが見つかった P62 Theorem 1.3.12. Let A, B ∈ Mn be diagonalizable. Then A and B commute if and only if they are simultaneously diagonalizable. Proof. Assume that A and B commute, perform a similarity transformation on both A and B that diagonalizes A (but not necessarily B) and groups together any repeated eigenvalues of A. Ifμ1,...,μd are the distinct eigenvalues of A and n1,...,nd are their respective multiplicities, then we may assume that 略す
P63 Observation 1.3.18. Suppose that n ≥ 2. A given A ∈ Mn is similar to a block triangular matrix of the form (1.3.17) if and only if some nontrivial subspace of Cn is A-invariant. Moreover, if W ⊆ Cn isanonzero A-invariantsubspace,thensomevector in W is an eigenvector of A. A given family F ⊆ Mn is reducible if and only if there is some k ∈{2,...,n −1} and a nonsingular S ∈ Mn such that S−1AS has the form (1.3.17) for every A ∈ F.
The following lemma is at the heart of many subsequent results.
Lemma1.3.19. Let F ⊂ Mn beacommutingfamily. Then some nonzero vector in Cn is an eigenvector of every A ∈ F. Proof. 略す
P64 Lemma 1.3.19 concerns commuting families of arbitrary nonzero cardinality. Our next result shows that Theorem 1.3.12 can be extended to arbitrary commuting families of diagonalizable matrices.
Definition 1.3.20. A family F ⊂ Mn is said to be simultaneously diagonalizable if there is a single nonsingular S ∈ Mn such that S−1AS is diagonal for every A ∈ F.
Theorem 1.3.21. Let F ⊂ Mn be a family of diagonalizable matrices. Then F is a commuting family if and only if it is a simultaneously diagonalizable family. Moreover, for any given A0 ∈ F and for any given ordering λ1,...,λn of the eigenvalues of A0, there is a nonsingular S ∈ Mn such that S−1A0S = diag(λ1,...,λn) and S−1BS is diagonal for every B ∈ F.
Proof. If F is simultaneously diagonalizable, then it is a commuting family by a previous exercise. We prove the converse by induction on n.Ifn = 1, there is nothing to prove since every family is both commuting and diagonal. Let us suppose that n ≥ 2 and that, for each k = 1,2,...,n − 1,anycommutingfamilyofk-by-k diagonalizable matrices is simultaneously diagonalizable. If every matrix in F is a scalar matrix, there is nothing to prove, so we may assume that A ∈ F is a given n-by-n diagonalizable matrix with distinct eigenvalues λ1,λ2,...,λk and k ≥ 2, that AB = BAfor every B ∈F, and that each B ∈ F is diagonalizable. Using the argument in (1.3.12), we reduce to the case in which A has the form (1.3.13). Since every B ∈ F commutes with A, (0.7.7) ensures that each B ∈ F has the form (1.3.14). Let B, ˆ B ∈ F, so B = B1⊕···⊕Bk and ˆ B = ˆ B1 ⊕···⊕ˆ Bk, in which each of Bi, ˆ Bi has the same size and that size is at most n − 1. Commutativity and diagonalizability of B and ˆ B imply commutativity and diagonalizability of Bi and ˆ Bi for each i = 1,...,d. By the induction hypothesis, there are k similarity matrices T1, T2,...,Tk of appropriate size,
each of which diagonalizes the corresponding block of every matrix in F. Then the direct sum (1.3.15) diagonalizes every matrix in F. Wehaveshownthat there is a nonsingular T ∈ Mn such that T−1BT is diagonal for every B ∈ F. Then T−1A0T = Pdiag(λ1,...,λn)PT for some permutation matrix P, PT(T−1A0T)P = (TP)−1A0(TP) = diag(λ1,...,λn) and (TP)−1B(TP) = PT(T−1BT)P is diagonal for every B ∈ F (0.9.5). □
Remarks: We defer two important issues until Chapter 3: (1) Given A, B ∈ Mn, how can we determine if A is similar to B? (2) How can we tell if a given matrix is diagonalizable without knowing its eigenvectors?
Although AB and BA need not be the same (and need not be the same size even when both products are defined), their eigenvalues are as much the same as possible. Indeed, if A and B arebothsquare,then ABand BAhaveexactlythesameeigenvalues. These important facts follow from a simple but very useful observation. (引用終り) 以上
対角化可能であるための必要十分条件 略 行列Aの固有ベクトルだけで n 次元ベクトル空間の基底が構成できるならば、それら縦ベクトルを横に並べた行列 P は正則行列となり、 P^{-1}AP=D が成り立ち、D の対角成分には A の固有値が並ぶ。 以上が行列が対角化できるための必要十分条件である。またこれは、実際に対角化を行うための手順にもなっている。
他にも同値な条件がいくつか知られている。
・(ここでは固有方程式が(重解を持つ場合も許容して)1次式の積に分解できることを前提とする。固有値・固有ベクトルが複素数でもよいのならこれはいつでも正しい(代数学の基本定理)が、実数だけで考えている場合は固有方程式の左辺が因数分解できないこともあり得る。) A の固有値を λ _{i},i=1,・・・ ,r, とするとき、A が対角化可能であるための必要十分条件は、次の等式が成り立つことである: Σ_{i=1}〜{r} dim ker (λ_{i} I_{n}-A)=n, ここで、In は n 次単位行列を表す。 ker(λ_{i}I_{n}-A)} は固有値 λi の固有空間であるから、この条件はベクトル空間の基底として A の固有ベクトルが取れることを意味している。 ・上の条件は、 Σ {i=1}〜{r} dim ker(λ _{i}I_{n}-A)} の各項が λ_{i}} の重複度と一致する、とも言い換えられる。一致しない場合はその固有空間の次元は λi を下回り、総計が n には成り得ないからである。詳しくは固有空間の次元を参照。 ・行列 A の最小多項式が重根をもたないことも対角化可能であるための必要十分条件である[2]。
A が実対称行列のとき、A は常に対角化可能であり、P として直交行列を取ることができる。 また A がユニタリー行列 U を用いて対角化できるためには、A が正規行列であることが必要十分である。 正規行列の中で応用上重要なクラスとして、対称行列とエルミート行列がある。