Strictly balanced factors are as informative as unbalanced factors

Let Σ={a,b}\Sigma=\{\mathtt{a},\mathtt{b}\}, and let Σsbn\Sigma_{sb}^{n} denote the strictly balanced words of length nn. For a word ww, write ScatFactk(w)\operatorname{ScatFact}_k(w) for its set of length-kk scattered factors. Two words are reconstructed from their kk-spectra when equality of the relevant scattered-factor sets forces the words to be equal. Strictly balanced reconstruction conjecture. For strictly balanced words ww, the strictly balanced scattered factors are just as informative as the unbalanced scattered factors: for every kNk\in\mathbb{N}, if k=k+1k'=k+1 for odd kk and k=k+2k'=k+2 for even kk, and w,wΣsb2kw,w'\in\Sigma_{sb}^{2k} satisfy

ScatFactk(w)Σsbk=ScatFactk(w)Σsbk,\operatorname{ScatFact}_{k'}(w)\cap\Sigma_{sb}^{k'}=\operatorname{ScatFact}_{k'}(w')\cap\Sigma_{sb}^{k'},

then w=ww=w'. This conjecture concerns reconstruction of strictly balanced binary words from their strictly balanced scattered factors; the source states that it is unresolved, while proving it for words with at most two blocks of [?][?]-letters and, by symmetry, at most two blocks of the other letter.

Sources & referencesView supporting material

Primary source

Joel D. Day, Pamela Fleischmann, Florin Manea and Dirk Nowotka, “k-Spectra of weakly-c-Balanced Words”, arXiv:1904.09125 (2019).

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