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Deformation invariance of numeric orthosymplectic DT invariants on Calabi–Yau threefolds

Prove that the numeric self-dual Donaldson–Thomas invariants $\mathrm{DT}^{\mathrm{sd}}_{\theta}(\tau)$ for Calabi–Yau threefolds are invariant under deformations of the complex structure of the threefold, analogously to the deformation-invariance result for Joyce–Song DT invariants in the linear setting.

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Background

The authors introduce orthosymplectic (self-dual) DT invariants for Calabi–Yau threefolds, generalizing classical DT theory beyond the linear case. In the linear case, numerical DT invariants are known to be deformation invariant.

They conjecture an analogous property for the self-dual invariants but explicitly state that they are currently unable to prove it, noting obstacles in adapting existing techniques (e.g., Joyce–Song pairs) to the self-dual setting.

References

We expect that the numeric version of the orthosymplectic DT invariants, $\mathrm{DT}_\theta\mathrm{sd} (\tau)$, should satisfy deformation invariance, analogously to \textcite[Corollary~5.28]{joyce-song-2012} in the linear case, that is, they should stay constant under deformations of the complex structure of the threefold~$Y$. However, we have not yet been able to prove this, as it does not seem straightforward to adapt the strategy of using Joyce--Song pairs to our case, and further work is needed.

Orthosymplectic Donaldson-Thomas theory (2503.20667 - Bu, 26 Mar 2025) in Subsection ‘DT invariants for threefolds’, Para ‘Expectations on deformation invariance’