The $σ_-$ Cohomology Analysis for Coxeter HS $B_2$ model
A. A. Tarusov, K. A. Ushakov
TL;DR
The paper develops a comprehensive $\sigma_-$-cohomology analysis for the $B_2$ Coxeter CHS model in $AdS_4$, focusing on one-forms in $(adj\otimes adj)$ and zero-forms in $(tw\otimes adj)$ and $(adj\otimes tw)$. It computes $H^0$, $H^1$, and $H^2$ for the $(adj\otimes adj)$ sector, establishing that the dynamics include symmetric massless and partially massless fields with a rich PM-depth structure, while unitary truncation yields standard Weyl tensors and on-shell Fronsdal dynamics; in the zero-form sectors, it reveals indecomposable $ ext{sl}(2) imes ext{sl}(2)$ structures and primary fields with diverse cocycles. The work also analyzes linear vertices gluing one- and zero-form sectors, finding many non-cohomological terms that impede a simple one-to-one gluing, and shows that suitable field redefinitions and unitary truncations can reorganize the theory so that dynamics are governed by 2-cocycles and on-shell Fronsdal-type equations. Appendices provide a detailed account of non-split extensions and momentum actions, supporting the understanding of indecomposable modules and their role in the CHS spectrum. Overall, the results confirm the presence of partially massless fields in $B_2$ CHS and clarify how the unfolded, cohomological framework encodes the spectrum and its (potential) unitary truncation.
Abstract
The dynamical content of equations resulting from rank-two covariant derivatives in $B_2$ Coxeter theory in $AdS_4$ are analyzed in terms of $σ_-$-complexes. Primary fields and gauge-invariant differential operators on primary fields are classified for $(adj \otimes adj)$ one-form fields $ω$ and $(tw\otimes adj)$ zero-form fields $C$. It is shown that one-forms $ω$ in the $(adj \otimes adj)$ sector encode symmetric massless fields and partially massless fields of all spins and depth of masslessness. Gluing of the one-form module to the zero-form modules at the linear vertices is studied.
