Harmonic non-constan function is surjective
39386
Harmonic non-surjective functions are constant
6186
An Integrable function which is not essentially bounded on any subinterval of $[0,1]$
45432
Showing that $f:(0,2\pi]\to S^1$ is not a homeomorphism
63453
A proof of the fact that the Fourier transform is not surjective from $\mathcal{L}^1(\mathbb{R})$ to $C_0( \mathbb{R})$
21843
Proving a function is not Riemann integrable
17223
Continuity of an inverse function.
93923
No surjective bounded linear map from $\ell^2(\mathbf{N})$ to $\ell^1(\mathbf{N})$
92493
If $G$ is non-abelian, then $Inn(G)$ is not a normal subgroup of the group of all bijective mappings $G \to G$
116750
On surjectivity of exponential map for Lie groups
134575
Show that the mapping $f → f~'$ from $C^1([0 , 1])$ to $C([0 , 1])$ is not continuous.
26353
Can any harmonic function on $\{z:0<|z|<1\}$ be extended to $z=0$?
132907
The inverse of a bijective holomorphic function is also holomorphic
20199
Find a surjective function $f:\mathbb{N}\to \mathbb{Q}$
110885
Does there exists a continuous surjection from $\mathbb{R}$ to $\mathbb{R}^2$?
75638
Let $u:\mathbb{C}\rightarrow\mathbb{R}$ be a harmonic function such that $0\leq f(z)$ for all $ z \in \mathbb{C}$. Prove that $u$ is constant.
117793
Finding a function $\mathbb{N} \to \mathbb{N}$ that is surjective but not injective.
54137
Find a non-negative function on [0,1] such that $t\cdot m(\{x:f(x) \geq t\}) \to 0$ that is not Lebesgue Integrable