On the mod-2 cohomology of the product of the infinite lens space and the space of invariants in a generic degree

Let S∞/Z2 be the infinite lens space. Denote the Steenrod algebra over the prime field F2 by A . The (mod-2) cohomology H∗ ((S∞/Z2) ⊕s ; F2) is known to be isomorphic to the graded polynomial ring Ps := F2[x1, . . . , xs] on s generators of degree 1, viewed as an unstable A -module. The Kameko squaring operation (Sqg0 ∗ )(s;N) : (F2 ⊗A Ps)2N+s −→ (F2 ⊗A Ps)N is rather useful in studying an open problem of determining the dimension of the indecomposables (F2 ⊗A Ps)N . It has been demonstrated that this (Sqg0 ∗ )(s;N) is onto. As a continuation of our recent works, this paper deals with the kernel of the Kameko (Sqg0 ∗ )(s;Nd) for the case where s = 5 and the "generic" degree Nd is of the form Nd = 5(2d − 1) + 11.2 d+1 for arbitrary d > 0. We then rectify almost all of the main results that were inaccurate in an earlier publication [Rev. Real Acad. Cienc. Exactas Fis. Nat. Ser. A-Mat. 116:81 (2022)] by Nguyen Khac Tin. We have also constructed several advanced algorithms in SageMath to validate our results. These new algorithms make an important contribution to tackling the intricate task of explicitly determining both the dimension and the basis for the indecomposables F2 ⊗A Ps at positive degrees, a problem concerning algorithmic approaches that had not previously been addressed by any author. Also, the present study encompasses an investigation of the behavior of the cohomological transfer in bidegrees (5, 5+Nd), with the internal degree Nd mentioned above.