bicontinuální

Bicontinuální refers to a property of certain mathematical objects, particularly in the context of topology and analysis. A function or a set is described as bicontinuální if it exhibits continuity in two distinct, related ways. In the realm of functions, a bicontinuální mapping $f$ between two topological spaces, say $X$ and $Y$, means that both $f$ and its inverse $f^{-1}$ are continuous. This implies that the function preserves the topological structure of both spaces in a symmetric manner. If $f$ is bicontinuální, it establishes a topological equivalence or homeomorphism between $X$ and $Y$.

The concept can also be extended to sequences or nets. A sequence $(x_n)$ in a topological space is said to be bicontinuální if it converges to a limit point and the sequence of its images under a continuous function $f$, i.e., $(f(x_n))$, also converges. More generally, for a function $f: X \to Y$, a subset $A \subseteq X$ is bicontinuously related to a subset $B \subseteq Y$ if $f(A) = B$ and $f^{-1}(B) = A$, and both $f$ restricted to $A$ and $f^{-1}$ restricted to $B$ are continuous. This implies that the mapping establishes a continuous bijection between these subsets. The term emphasizes a mutual continuity, where the forward and backward transformations both respect the topological properties of the spaces involved.