Anti-de sitter space, although it is infinite, has a "boundary, " located out at infinity.

反德西特空间虽然无穷大，却有个位于无穷远的“边界”。

youdao

This drift became known as the de Sitter effect.

FORBES: A Giant In Hubble's Shadow

After Hubble published his findings in 1929, he, Einstein, British astronomer Sir Arthur Stanley Eddington, and Dutch astronomer Willem de Sitter, all gathered at a special meeting of the Royal Astronomical Society and pondered how they could account for such developments based on static universe models that Einstein and de Sitter had derived with General Relativity.

FORBES: Why Hubble's Law ... Wasn't Really Hubble's