Why is $\operatorname{spec}(K[x,y])-\{(x,y)\}$ not isomorphic to $\operatorname{spec} K[x,y]$
88474
$\mathbb{A}^{2}$ not isomorphic to affine space minus the origin
9140
Show $\operatorname{Aut}(C_2 \times C_2)$ is isomorphic to $S_3=D_6$
42652
Must $k$-subalgebra of $k[x]$ be finitely generated?
147888
Show that $M=\bigcap_{\mathfrak{p}\in\operatorname{Spec}(R)}M_\mathfrak{p}=\bigcap_{\mathfrak{m}\in\text{Max}(R)}M_\mathfrak{m}$ for certain $M$.
74537
Maximal Ideals in $K[y]$
60925
Why these are isomorphic each other for given these rings?
101095
Constructing an example s.t. $\operatorname{Hom}_R(M,N)$ is not finitely generated
102879
$\operatorname{Ext}$ and injectives, respectively projectives
117131
Canonical Isomorphism Between $\mathbf{V}$ and $(\mathbf{V}^*)^*$
108955
Showing $(\mathbb{Q},+)$ is not isomorphic to $(\mathbb{R},+)$
85987
Prove that $k[x,y,z,w]/(xy-zw)$, the coordinate ring of $V(xy-zw) \subset \mathbb{A}^4$, is not a unique factorization domain
92703
Proving that $\mathbb{Z}[x]$ and $\mathbb{Q}[x]$ are not isomorphic.
145462
On the canonical isomorphism between $V$ and $V^{**}$
66708
Elementary isomorphism between $\operatorname{PSL}(2,5)$ and $A_5$
24708
Why is $\operatorname{Int}(A) \cup \operatorname{Int}(B) \neq \operatorname{Int}(A \cup B)$?
91222
Isomorphism between $\mathfrak o(4,\mathbb R)$ and $\mathfrak o (3,\mathbb R) \oplus\mathfrak o (3,\mathbb R) $
158232
Tensor product of a module with an ideal is isomorphic to their standard product