Monotonicity conjecture for the alternative discrete Painlevé I solutions

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Let bn(t)b_n(t) and an(t)a_n(t) denote the positive solutions and associated quantities introduced in the paper, with nn a nonnegative integer. For fixed t>0t>0, the expressions an(t)/na_n(t)/n are understood for n≥1n\geq 1. Monotonicity conjecture. If 0<t1<t20<t_1<t_2, then

bn(t1)<bn(t2),an(t1)>an(t2),b_n(t_1)<b_n(t_2),\qquad a_n(t_1)>a_n(t_2),

so bn(t)b_n(t) is monotonically increasing and an(t)a_n(t) is monotonically decreasing for t>0t>0. For fixed t>0t>0,

t<bn(t)<bn+1(t),12t>an(t)n>an+1(t)n+1>0.\sqrt{t}<b_n(t)<b_{n+1}(t),\qquad \frac{1}{2\sqrt{t}}>\frac{a_n(t)}{n}>\frac{a_{n+1}(t)}{n+1}>0.

The conjecture is suggested by numerical plots and corroborates the preceding conjecture and lemma; the monotonicity of bn(t)b_n(t) in tt is explicitly noted as analytically unproved, and no resolution is supplied here.

References

Primary source

Peter A. Clarkson, Ana F. Loureiro and Walter Van Assche, “Unique positive solution for an alternative discrete Painlevé I equation”, arXiv:1508.04916 (2015).

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