[math-fun] Continued fractions of Gaussian integers for complex numbers
Let z be any complex number whose real and imaginary parts are not both rational. Set z_0 = floor(Re(z)) + i*floor(Im(z)) (the lower left corner of the integer grid square that z lies in). Thereafter set z_(n+1) = floor(Re(1/z_n)) + i*floor(Im(1/z_n)) Then z_0, z_1, ..., z_n, ... in Z[i] form a series of Gaussian integers representing z, generalizing continued fraction expansions of irrational real numbers. * Have such things been studied? * For almost all real numbers x, the geometric mean of all the "digits"* gm(x) = lim (K_0 K_1 ... K_n)^(1/n) n —> oo of the cfe of x is equal to the same number. What about the corresponding geometric mean of the Gaussian integers gm(z) = (z_0 z_1 ... z_n)^(1/n) ??? —Dan ————— * Should we call them "tigids"?
See the final sections of the beautiful paper by L. R. Ford, recently mentioned elsewhere on math-fun --- https://www.maths.ed.ac.uk/~v1ranick/papers/ford.pdf WFL On 3/22/19, Dan Asimov <dasimov@earthlink.net> wrote:
Let z be any complex number whose real and imaginary parts are not both rational.
Set
z_0 = floor(Re(z)) + i*floor(Im(z))
(the lower left corner of the integer grid square that z lies in). Thereafter set
z_(n+1) = floor(Re(1/z_n)) + i*floor(Im(1/z_n))
Then z_0, z_1, ..., z_n, ... in Z[i] form a series of Gaussian integers representing z, generalizing continued fraction expansions of irrational real numbers.
* Have such things been studied?
* For almost all real numbers x, the geometric mean of all the "digits"*
gm(x) = lim (K_0 K_1 ... K_n)^(1/n) n —> oo
of the cfe of x is equal to the same number. What about the corresponding geometric mean of the Gaussian integers
gm(z) = (z_0 z_1 ... z_n)^(1/n) ???
—Dan ————— * Should we call them "tigids"?
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There are many papers on this subject. I wrote about it in my undergraduate thesis (available at https://cs.uwaterloo.ca/~shallit/papers.html, under "1979"). My thesis contains references to other papers. It turns out that your particular suggestion of how to do complex floor is not a good one, but other choices work. On 3/21/19 9:01 PM, Dan Asimov wrote:
Let z be any complex number whose real and imaginary parts are not both rational.
Set
z_0 = floor(Re(z)) + i*floor(Im(z))
(the lower left corner of the integer grid square that z lies in). Thereafter set
z_(n+1) = floor(Re(1/z_n)) + i*floor(Im(1/z_n))
Then z_0, z_1, ..., z_n, ... in Z[i] form a series of Gaussian integers representing z, generalizing continued fraction expansions of irrational real numbers.
* Have such things been studied?
* For almost all real numbers x, the geometric mean of all the "digits"*
gm(x) = lim (K_0 K_1 ... K_n)^(1/n) n —> oo
of the cfe of x is equal to the same number. What about the corresponding geometric mean of the Gaussian integers
gm(z) = (z_0 z_1 ... z_n)^(1/n) ???
—Dan ————— * Should we call them "tigids"?
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participants (3)
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Dan Asimov -
Fred Lunnon -
Jeffrey Shallit