Barja–González–Naranjo modified Xiao conjecture for the relative irregularity

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Let f ⁣:S→Bf\colon S\to B be a non-isotrivial fibred surface of genus g≥2g\geq 2, and let qfq_f denote its relative irregularity. The integer-valued upper bound is

⌈g+12⌉.\left\lceil \frac{g+1}{2}\right\rceil.

Barja–González–Naranjo's modified conjecture. For every non-isotrivial fibred surface f ⁣:S→Bf\colon S\to B of genus g≥2g\geq 2,

qf≤⌈g+12⌉.q_f\leq \left\lceil \frac{g+1}{2}\right\rceil.

This modification is proposed after counterexamples to Xiao's original conjecture; the supplied text does not establish whether the modified conjecture has been resolved.

References

Primary source

Lidia Stoppino, “Fibred surfaces and their unitary rank”, arXiv:2406.15909 (2025).

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