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. 2020 Sep 12;22(9):1019. doi: 10.3390/e22091019
Complex matrices:
Number field F Real R or complex C
M(d,F) Space of square d×d matrices in F
Sym(d,R) Space of real symmetric matrices
0 matrix with all coefficients equal to zero (disk origin)
Fröbenius norm MF=i,j|Mi,j|2
Operator norm MO=σmax(M)=maxi{|λi(M)|}
Domains:
Cone of SPD matrices PD(d,R)={P0:PSym(d,R)}
Siegel–Poincaré upper plane SH(d)=Z=X+iY:XSym(d,R),YPD(d,R)
Siegel–Poincaré disk SD(d)=WSym(d,C):IW¯W0
Distances:
Siegel distance ρU(Z1,Z2)=i=1dlog21+ri1ri
ri=λiR(Z1,Z2)
R(Z1,Z2):=(Z1Z2)(Z1Z¯2)1(Z¯1Z¯2)(Z¯1Z¯2)1
Upper plane metric dsU(Z)=2trY1dZY1dZ¯
PD distance ρPD(P1,P2)=Log(P11P2)F=i=1dlog2λi(P11P2)
PD metric dsPD(P)=tr(P1dP)2
Kobayashi distance ρD(W1,W2)=log1+ΦW1(W2)O1ΦW1(W2)O
Translation in the disk ΦW1(W2)=(IW1W¯1)12(W2W1)(IW¯1W2)1(IW¯1W1)12
Disk distance to origin ρD(0,W)=log1+WO1WO
Siegel–Klein distance ρK(K1,K2)=12logα+(1α)α(α+1),K1K2,0K1=K2
(1α)K1+αK2O=1 (α<0), (1α+)K1+α+K2O=1 (α+>1)
Seigel-Klein distance to 0 ρK(0,K)=12log1+KO1KO
Symplectic maps and groups:
Symplectic map ϕS(Z)=(AZ+B)(CZ+D)1 with SSp(d,R) (upper plane)
ϕS(W) with SSp(d,C) (disk)
Symplectic group Sp(d,F)=ABCD,AB=BA,CD=DC,ADBC=I
A,B,C,DM(d,F)
group composition law matrix multiplication
group inverse law S(1)=:DBCA
Translation in H(d) of Z=A+iB to iI TU(Z)=(B12)0(AB12)(B12)
symplectic orthogonal matrices SpO(2d,R)=ABBA:AA+BB=I,ABSym(d,R)
(rotations in SH(d))
Translation to 0 in SD(d) ΦW1(W2)=(IW1W¯1)12(W2W1)(IW¯1W2)1(IW¯1W1)12
Isom+(S) Isometric orientation-preserving group of generic space S
Moeb(d) group of Möbius transformations