Abstract
Let p be a prime number. We prove that the \(P=W\) conjecture for \(\mathrm {SL}_p\) is equivalent to the \(P=W\) conjecture for \(\mathrm {GL}_p\). As a consequence, we verify the \(P=W\) conjecture for genus 2 and \(\mathrm {SL}_p\). For the proof, we compute the perverse filtration and the weight filtration for the variant cohomology associated with the \(\mathrm {SL}_p\)-Hitchin moduli space and the \(\mathrm {SL}_p\)-twisted character variety, relying on Gröchenig–Wyss–Ziegler’s recent proof of the topological mirror conjecture by Hausel–Thaddeus. Finally we discuss obstructions of studying the cohomology of the \(\mathrm {SL}_n\)-Hitchin moduli space via compact hyper-Kähler manifolds.
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Notes
We call M an irreducible hyper-Kähler manifold if M is simply connected satisfying that \(H^0(M, \Omega _M)\) is generated by a non-where degenerate holomorphic 2-form. We say that a hyper-Kähler manifold is of Kummer type if it deforms to a generalized Kummer variety.
Since this construction is not essentially used in the present paper, we omit further details.
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Acknowledgements
We are grateful to Chen Wan and Zhiwei Yun for helpful discussions. We also thank the anonymous referee for careful reading of the paper. The first-named author is partially supported by NSF DMS Grant 1901975. The third-named author is partially supported by NSF DMS Grant 2134315.
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