New posts in examples-counterexamples

Nasty examples for different classes of functions

Topologist's Sine Curve not a regular submanifold of $\mathbb{R^2}$?

Natural uses for the co-product of sets?

Is $2^{\aleph_0} = \aleph_1$?

An Example of a Nested Decreasing Sequence of Bounded Closed Sets with Empty Intersection

Does There exist a continuous bijection $\mathbb{Q}\to \mathbb{Q}\times \mathbb{Q}$?

Definition of the normalizer of a subgroup [duplicate]

Tensor product of injective ring homomorphisms

Continuous partials at a point without being defined throughout a neighborhood and not differentiable there?

Example of a rational function such that : $(f(x))^{3} + (g(x))^{3} + (h(x))^{3}=x$

Example of a Bounded Linear Operator with Unbounded Spectrum.

Ring and Subring with different Identities [duplicate]

The homotopy category of complexes

Multiplying convergent and divergent sequences

Subspaces of $\ell^{2}$ and $\ell^{\infty}$ which are not closed?

Basic Example of Yoneda Lemma?

Counterexample to second derivative test when f''(x) is not continuously differentiable

Lower Semicontinuity Concepts

Example: satisfying $E(X_{n+1}\mid X_n)=X_n$ but not a martingale

A comparison between the fundamental groupoid and the fundamental group