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Preprint . 2026
License: CC BY
Data sources: Datacite
ZENODO
Preprint . 2026
License: CC BY
Data sources: Datacite
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The Zwegers shadow as $U(1)$-projected intrinsic torsion\\ on twelve-manifolds

Authors: Master, Dhiren Jashwant;

The Zwegers shadow as $U(1)$-projected intrinsic torsion\\ on twelve-manifolds

Abstract

On a closed almost-quaternionic $\text{Spin}^c$ orbifold of real dimension $4n \geq 12$, with non-trivial determinant line bundle $L$ and a compatible involution $\sigma$, two obstruction classes from independent traditions coexist: Swann's intrinsic torsion, which measures the failure of quaternion-Kahler holonomy, and the Bruinier--Funke shadow, which measures the failure of modularity of the associated partition function. We show that the $U(1)$-projection of the intrinsic torsion under the $Sp(1) \to U(1)$ reduction induced by the $\text{Spin}^c$ structure and the shadow of the equivariant elliptic genus are cohomologically equivalent classes in the $\sigma$-odd component of rational cohomology, normalised by $c_{1}(L)$; the proof uses Swann's absorption of almost-quaternionic torsion into hyperkahler holonomy, its orbifold extension, Leray injectivity, and the Bruinier--Funke characterisation of shadows. A functorial refinement --- a spectral push-forward into $S_{3/2}(\Gamma_{0}(36), \chi)$, together with a compatible map of short exact sequences --- holds at the level of sheaves unconditionally, and pointwise under one explicitly stated structural hypothesis. On the twelve-dimensional orbifold $K_8 = [(\mathbb{CP}^2 \times S^2) \times_{w} (T^2/\mathbb{Z}_2)]^{\text{Spin}^c}$ the determinant line is $\mathcal{O}(3)$ by the Euler sequence, and the integer $3$ coincides with the coefficient $3$ in the completion $E_2^* = E_2 - \frac{3}{\pi \tau_2}$, the two anchorings independent. The oddness of $c_{1}(L)$ forces the involution to act freely on the shifted momentum lattice; constant configurations are consequently a symmetry-protected critical stratum of the spectral-rigidity functional on $\sigma$-even conformal deformations of the pillowcase factor, the kernel decouples, and the critical structure assembles multiplicatively to $6 \times 2 = 12 = \chi(K_8)$. The lowest eigenvalue of the $\text{Spin}^c$ Dirac operator on the toroidal factor is exactly $\pi$, independently of the modulus.

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
0
Average
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Average
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