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Equality of T"(X) and T'(X) beyond perfectly normal spaces

Determine whether there exists a topological space X that is not perfectly normal yet satisfies T"(X) = T'(X), where T"(X) is the ring of real-valued functions on X that are continuous on a dense cozero set and T'(X) is the ring of real-valued functions on X that are continuous on an open dense subset.

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Background

The paper proves that for perfectly normal spaces X, T"(X) equals T'(X). It also provides an example (the one-point compactification of a discrete real line) in which X is not perfectly normal and T"(X) is a proper subring of T'(X).

This motivates investigating whether equality T"(X) = T'(X) can occur for spaces outside the perfectly normal class.

References

Whether there exists a topological space outside the class of perfectly normal spaces for which T"(X) = T'(X) remains an unanswered question.

The ring of real-valued functions which are continuous on a dense cozero set (2502.15358 - Dey et al., 21 Feb 2025) in Remark 2.9, Section 2