The Hawaiian earring is the union of a countable family of circles tangent at one point, with their radii tending to zero, endowed with its planar subspace topology. Equivalently it is the one-point compactification of a countable disjoint union of real lines. Every neighbourhood of the common point contains all but finitely many whole circles. This compact topological space is not locally contractible there and has different singular homology from the infinite CW complex wedge of circles.
The first integral singular homology of the Hawaiian earring has a direct summand isomorphic to . This consequence of its structural homology theorem suffices, through the universal coefficient theorem for cohomology and nonzero Ext of the rationals with integer coefficients, to show that its integral is nonzero. The precise structural theorem is Theorem 3.1 of www.sas.rochester.edu/mth/sites/doug-ravenel/otherpapers/eda-kawamura2.pdf.
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Hawaiian earrings typically refer to earrings that are inspired by the traditional art and culture of Hawaii. These earrings often feature motifs and designs that are associated with Hawaiian imagery, such as flowers (like hibiscus), sea life, and other natural elements that reflect the beauty of the islands. Materials used in Hawaiian earrings can vary widely, including precious metals, shells, wood, and coral.