Conjecture that the stellated tetrahedron P11/20\mathcal{P}_{11/20} is not Rupert

Let Pa\mathcal{P}_a be the stellated tetrahedron with vertices

p0=(1,1,1),q0=(−a,−a,−a),p_0=(1,1,1),\quad q_0=(-a,-a,-a), p1=(1,−1,−1),q1=(−a,a,a),p_1=(1,-1,-1),\quad q_1=(-a,a,a), p2=(−1,1,−1),q2=(a,−a,a),p_2=(-1,1,-1),\quad q_2=(a,-a,a), p3=(−1,−1,1),q3=(a,a,−a),p_3=(-1,-1,1),\quad q_3=(a,a,-a),

where edges join all pi,pjp_i,p_j and pi,qjp_i,q_j for i≠ji\ne j, and a∈(0.5,0.57)a\in(0.5,0.57). A polyhedron is Rupert if it can pass through itself under the projection-and-translation containment condition. Stellated-tetrahedron conjecture. The stellated tetrahedron P11/20\mathcal{P}_{11/20} is not Rupert. Numerical searches have not found a Rupert passage for the relevant family, and the stated sufficient condition for being locally Rupert does not apply; whether this particular stellated tetrahedron is non-Rupert remains open.

References

Primary source

Tony Zeng, “A stellated tetrahedron that is probably not Rupert”, arXiv:2604.26531 (2026).

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