Composite-degree extremal reciprocal polynomial conjecture

Let mr(d)\mathrm{mr}(d) be the minimum of the houses of reciprocal algebraic integers of degree dd that are not roots of unity, and let Rd(x)R_d(x) be the minimal polynomial of an extremal reciprocal algebraic integer. Let dd be composite, and let p1,,pkp_1,\ldots,p_k be odd prime divisors of dd or elements of {s,t}\{s,t\}, where s=9s=9 and

t=1;t=4 if 8d and 12d;t=6 if 12d.t=1;\qquad t=4\text{ if }8\mid d\text{ and }12\nmid d;\qquad t=6\text{ if }12\mid d.

Suppose

mr2p1(2p1)<mr2p2(2p2)<<mr2pk(2pk).\mathrm{mr}^{2p_1}(2p_1)<\mathrm{mr}^{2p_2}(2p_2)<\cdots<\mathrm{mr}^{2p_k}(2p_k).

Composite-degree extremal reciprocal polynomial conjecture. If R2pi(x)R_{2p_i}(x) is the minimal polynomial of the extremal reciprocal algebraic integer of degree 2pi2p_i, then

Rd(x)=R2p1(xd/(2p1))R_d(x)=R_{2p_1}(x^{d/(2p_1)})

and

mr(d)=R2p1(xd/(2p1)).\mathrm{mr}(d)=\lvert R_{2p_1}(x^{d/(2p_1)})\rvert.

The conjecture is motivated by the computed smallest houses of reciprocal polynomials and would reduce composite-degree reciprocal cases to selected lower-degree cases. No resolution status is given in the source.

Sources & referencesView supporting material

Primary source

Dragan Stankov, “The House of a Reciprocal Algebraic Integer”, arXiv:1806.06424 (2018).

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