Problem in Eigen values plot

Question

AVM 2020-6-25

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/554575-problem-in-eigen-values-plot

评论： AVM 2020-6-28

I would like to plot the First five minimum eigenvalues in assending order w.r.t. ''g '' of the following Matrix using for loop. But am really confuse to sort the minimum eigevlaues. Can anybody help me to solve that?

clc;
syms   g
omega=1.0;
D = 1.0;
n=15;
I1=eye(n);
I2=eye(2);
matdimension= n-1;
tempvector = 0:1:matdimension;
tempvector = sqrt(tempvector);
tempmatrix = diag(tempvector);
anni= circshift(tempmatrix,-1);
crea = anni';
sc=(crea)^2;
sanni=(anni)^2;
num=crea*anni;
c=crea+anni;
d=sc+sanni;
sigx=[0,1;1,0];
sigy=[0,-1i;1i,0];
sigz=[1,0; 0,-1];
sigp=(1/2)*(sigx+1i.*sigy);
sigm=(1/2)*(sigx -1i.*sigy);
g=0:0.01:2.0;
for i = 1:length(g)
    
       A= omega.*kron(I2,num) + (D./2).* kron(sigz,I1) + g(i).*kron(sigx,c); 
      
      [~,v]=eig(A);
      
    
   
end
%plot(g,p1,'r',g,p2,'r',g,p3,'r',g,p4,'r',g,p5,'r')
%ax = gca;
%set(gca,'XMinorTick','on','YMinorTick','on')

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Answer 1

Takumi 2020-6-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/554575-problem-in-eigen-values-plot#answer_457528

在 MATLAB Online 中打开

Using sort function, you can sort the elements of matrix in ascending order.

clc;
close all
clear
syms   g
omega=1.0;
D = 1.0;
n=15;
I1=eye(n);
I2=eye(2);
matdimension= n-1;
tempvector = 0:1:matdimension;
tempvector = sqrt(tempvector);
tempmatrix = diag(tempvector);
anni= circshift(tempmatrix,-1);
crea = anni';
sc=(crea)^2;
sanni=(anni)^2;
num=crea*anni;
c=crea+anni;
d=sc+sanni;
sigx=[0,1;1,0];
sigy=[0,-1i;1i,0];
sigz=[1,0; 0,-1];
sigp=(1/2)*(sigx+1i.*sigy);
sigm=(1/2)*(sigx -1i.*sigy);
g=0:0.01:2.0;
for i = 1:length(g)
    
       A= omega.*kron(I2,num) + (D./2).* kron(sigz,I1) + g(i).*kron(sigx,c); 
      
      [~,v]=eig(A);
      V=diag(v);
      Vsort = sort(V);
      Vsort(1)   % minimum eigenvalue
      Vsort(1:5)   % First five minimum eigenvalues
end