Zeros of Random Kac Polynomials

set distribution

normal N(0, 1)

cosine of uniform U(0, 2π)

show unit circle

number of coefficients

50

This Demonstration shows that the zeros of random Kac polynomials

P(z)=

n

∑

i=0

a

i

z

=

n

∏

i=1

(z-

z

i

)

with independent and identically distributed (i.i.d.) coefficients

a

i

cluster along the complex unit circle as the polynomial degree increases.

Setting the control "set distribution" to "normal

N(0,1)

", the polynomial coefficients

a

i

are distributed according to the standard normal distribution with zero mean and unit standard deviation

a

i

~N(0,1)

[1].

Setting the control "set distribution" to "cosine of uniform

U(0,2π)

", the coefficients

a

i

are the cosines of the values sampled from a uniform distribution

U(0,2π)

.

You can increase the number of coefficients

a

i

computed from the selected probability distribution to get a larger set of complex roots. For more than 100 or so coefficients, you can see that the zeros cluster around the unit circle in the complex plane.