eigen value is not showing

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shiv gaur 2022-1-7

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1624235-eigen-value-is-not-showing

编辑： John D'Errico 2022-1-7

k0=2*pi/l;
nc=1.33;
ec=nc^2;
na=1.43;
ea=na^2;
nf=1.59;
ef=nf^2;
nm=0.064+1i*4;
em=nm^2;
ns=1.495;
es=ns^2;
df=0.5e-6;
dm=0.03e-6;
da=0.06e-6;
kc=sqrt(kx.^2-ec*k0^2);
ka=sqrt(ea*k0^2-kx.^2);
kf=sqrt(ef*k0^2-kx.^2);
km=sqrt(em*k0^2-kx.^2);
ks=sqrt(kx.^2-es*k0^2);
a11=exp(-ks*dm);
a12=-exp(-km*dm);
a13=exp(km*dm);
a14=0;a15=0;a16=0;a17=0;a18=0;
a21= ks.*exp(-ks*dm);
a22=1i*km.*exp(-1i*km*dm);
a23= -1i*km.*exp(1i*km*dm);
a24=0;
a25=0;a26=0;a27=0;a28=0;
a31=0;a32=1;a33=1;a34=-1;a35=-1;a36=0;a37=0;a38=0;
a42=1i*km;a41=0;a43=-1i*km;a44=-1i*kf;a45=1i*kf;a46=0;a47=0;a48=0;
a51=0;a52=0;a53=0;a54=exp(1i*kf*df); a55=exp(-1i*kf*df);a56=-exp(1i*ka*df);a57=-exp(-1i*ka*df);
a58=0;a61=0;a62=0;a63=0;a64=1i*kf.*exp(1i*kf*df);a65=-1i*kf.*exp(-1i*kf*df);
a66=-1i*ka.*exp(1i*ka*df);a67=1i*ka.*exp(-1i*ka*df);a68=0;
a71=0;a72=0;a73=0;a74=0;a75=0;a76=exp(1i*ka*(da+df));
a77=- exp(-1i*ka*(da+df));a78= exp(-1i*kc*(da+df));
a81=0;a82=0;a83=0;a84=0;a85=0;a86=1i*ka.* exp(1i*ka*(da+df));a87=-1i*ka.*exp(-1i*ka*(da+df));
a88=kc.*exp(1i*kc*(da+df));
Phi=[a11  a12  a13  a14  a15  a16   a17  a18; a21  a22  a23  a24  a25  a26   a27  a28; a31  a32  a33  a34  a35  a36   a37  a38; a41  a42  a43  a44  a45  a46   a47  a48; a51  a52  a53  a54  a55  a56   a57  a58; a61  a62  a63  a64  a65  a66   a67  a68; a71  a72  a73  a74  a75  a76   a77  a78; a81  a82  a83  a84  a85  a86   a87  a88];
eig(Phi)

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shiv gaur 2022-1-7

the l value is 0.6328*10^-10

John D'Errico 2022-1-7

编辑：John D'Errico 2022-1-7

在 MATLAB Online 中打开

It is a REALLY, REALLY, REALLY bad idea to define a variable named lower case L, so l. That is because l and the number 1 look almost indistinguishable in some fonts. O and 0 are another case that you really need to avoid.

Next, learn to use scientific notation.

l = 0.6328e-10

Next, when I try to execute your code, I see this error:

'kx' requires Datafeed Toolbox.

That is because you never defined the variable kx, but then you have these lines:

kc=sqrt(kx.^2-ec*k0^2);
ka=sqrt(ea*k0^2-kx.^2);
kf=sqrt(ef*k0^2-kx.^2);
km=sqrt(em*k0^2-kx.^2);
ks=sqrt(kx.^2-es*k0^2);

I still cannot get to the end of your code to know what is happening. As I read through all of your comments, it appears that you want kx to be an unknown?

If so, then eig CANNOT work, because the result will be a symbolic matrix with an unknown variable in it. And that must fail, because the matrix is of size 8. I you remember that the eigenvalues of a matrix can be considered as the roots of a characteristic polynomial of that matrix. Since the polynomial will be of degree at least 8, tthen eig will fail.

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