A note on generalized invertibility and invariants of infinite matrices

The classes of band-dominated operators and the subclass of operators in the Wiener algebra $${\mathcal {W}}$$ W are known to be inverse closed. This paper studies and extends partially known results of that type for one-sided and generalized invertibility. Furthermore, for the operators in the Wiener algebra $${\mathcal {W}}$$ W invertibility, the Fredholm property and the Fredholm index are known to be independent of the underlying space $$l^p$$ l p , $$1\le p\le \infty $$ 1 ≤ p ≤ ∞ . Here this is completed by the observation that even the kernel and a suitable direct complement of the range as well as generalized inverses of operators in $${\mathcal {W}}$$ W are invariant w.r.t. p.

Special Periodic Even Functions

In this paper the periodic even functions for which all the regular Riemann sums vanishe are called special periodic even functions. A construction of some of them is put forward, this one rest on the Fourier serie and H. Davenport’s estimations concerning the Moebius function. The special periodic even functions seem linked to the number theory, as this can be seen on the Fourier serie result, on the proposed constructions and on the proof that such functions cannot belong to the Wiener algebra.