Reputation
7,456
Top tag
Next privilege 10,000 Rep.
Access moderator tools
Badges
1 10 32
Newest
 Informed
Impact
~86k people reached

Feb
28
comment Monomorphisms and Epimorphisms in the category of small categories
I'd voluntarily left some of the details. Hope you don't mind.
Feb
28
answered Monomorphisms and Epimorphisms in the category of small categories
Feb
28
comment Gödel's Completeness Theorem and satisfiability of a formula in first-order logic
@MauroALLEGRANZA are you looking for a witness of indecidibility of first order logic?
Feb
26
reviewed Approve Why must this be a closed curve?
Feb
25
answered What to read alongside with Hatcher Algebraic Topology
Feb
22
reviewed Approve independent/dependent values at different frequencies and phases
Feb
22
reviewed Approve Calculus: tangents and limits
Feb
19
comment How do I prove that the function symbol $\circ$ is not a term by induction in the calculus?
then from the rule T2, since as you say $\circ \in S$, we have that $\circ$ is term. Otherwise you have to restrict rule T2 so that it can be applied just to term with $0$-ariety.
Feb
19
comment How do I prove that the function symbol $\circ$ is not a term by induction in the calculus?
What do you mean by $\circ$, is a defined term or is part of the alphabeth (which I suppose is $S$)? In the second case from you rules it should follow that $\circ$ is a term since for every $f \in S$ it follows that $f$ is term (T2), since in this rule there's no restriction on the applicability. Hope this helps.
Feb
15
comment What are morphisms in the category of sets $\mathbf{Set}$?
@Alexey you're welcome.
Feb
15
comment What are morphisms in the category of sets $\mathbf{Set}$?
@Alexey I do: "Category theory starts... ... Each arrow $f \colon X \to Y$ represent a function; that is, a set $X$, a set $Y$, and a rule $x \mapsto fx$ which ..." at page 1.
Feb
15
comment What are morphisms in the category of sets $\mathbf{Set}$?
For the function is said in the introduction of "Category theory for Working mathematician".
Feb
15
answered What are morphisms in the category of sets $\mathbf{Set}$?
Feb
12
comment If $N$ is an $R/I$-submodule of $M$ can we view $N$ as an $R$-submodule of $M$?
@Edgar $N$ is a $R/I$-submodule of the $R/I$-module...?
Feb
8
reviewed Approve Suggestions on how to verify this partial differential equation solution
Feb
7
reviewed Approve $f(f(\sqrt{2}))=\sqrt{2}$ then f has a fixed point
Feb
7
comment On which structures does the free group 'naturally' act?
Of course a free group naturally act on the set of strings on the generators: which is the Cayley actions, nonetheless I suppose you weren't interested in such trivial action.
Feb
3
comment There are two types of functors; covariant and contravariant. Is it right?
@user112018 I guess so :)
Feb
3
comment There are two types of functors; covariant and contravariant. Is it right?
@user112018 I've added an Edit, let me know if that solves your doubts.
Feb
3
revised There are two types of functors; covariant and contravariant. Is it right?
added 977 characters in body