文摘
Categories of lax (T,V )(T,V\,)-algebras are shown to have pullback-stable coproducts if TT preserves inverse images. The general result not only gives a common proof of this property in many topological categories but also shows that important topological categories, like the category of uniform spaces, are not presentable as a category of lax (T,V )(T,V\,)-algebras, with TT preserving inverse images. Moreover, we show that any such category of (T,V )(T,V\,)-algebras has a concrete, coproduct preserving functor into the category of topological spaces.