Threshold classification conjecture for the normalized time-delay system

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Consider the normalized delay differential equation referred to as, with solution u(t;β,w0)u(t;\beta,w_0) for parameter β\beta and initial velocity w0w_0. Let the comparison properties be those denoted by and. Threshold classification conjecture. For β≥1\beta\geq 1, there exists a unique value g(β)∈(0,1)g(\beta)\in(0,1) such that the solution u(t;β,w0)u(t;\beta,w_0) has the following behavior: if w0∈(g(β),1)w_0\in(g(\beta),1), there is a constant T∗=T∗(β,w0)>0T_*=T_*(\beta,w_0)>0 satisfying

u(t;β,w0)<1(0≤t<T∗),u(T∗;β,w0)=1,u(t;β,w0)>1(t>T∗);u(t;\beta,w_0)<1\quad(0\leq t<T_*),\qquad u(T_*;\beta,w_0)=1,\qquad u(t;\beta,w_0)>1\quad(t>T_*);

if w0∈(0,g(β)]w_0\in(0,g(\beta)], then

u(t;β,w0)<1(t≥0),u(t;β,w0)→1as t→∞;u(t;\beta,w_0)<1\quad(t\geq0),\qquad u(t;\beta,w_0)\to1\quad\text{as }t\to\infty;

and the comparison properties and hold. The numerical experiments motivate this threshold description of the dynamics, but the existence and uniqueness of g(β)g(\beta) and the stated comparison properties are conjectural.

References

Primary source

Masato Kimura, Hirotaka Kuma, Yikan Liu, Kazunori Matsui, Masahiro Yamamoto and Zhenxing Yang, “Threshold dynamics in time-delay systems: polynomial β-control in a pressing process and connections to blow-up”, arXiv:2508.07268 (2025).

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