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Apr
20
comment Opposite category functor
But sperners lemma's answer above gave an isomorphism $Dual : \mathcal{C} \to \mathcal{C}^{op}$, so $\mathcal{C}$ must be equivalent to $\mathcal{C}^{op}$.
Apr
18
accepted What does it mean for pullbacks to preserve monomorphisms?
Apr
16
asked What does it mean for pullbacks to preserve monomorphisms?
Mar
11
asked What is the least ordinal $\beta$ for which the function $f_\beta(n)$ in fast-growing hierarchy is incomputable?
Mar
8
comment The rationale behind the oracle machine notation with brackets $\{e\}^A$
@QuinnCulver Bob's reply was exactly the one in the quotes, whatever the origin may be (even if he knew), clearly he did not consider it worth the time explaining it.
Mar
8
accepted Errata for Rogers' Computability book
Mar
8
accepted What is an omega model?
Mar
8
comment The rationale behind the oracle machine notation with brackets $\{e\}^A$
@QuinnCulver I asked, confer the answer.
Mar
8
answered The rationale behind the oracle machine notation with brackets $\{e\}^A$
Mar
1
asked The rationale behind the oracle machine notation with brackets $\{e\}^A$
Feb
24
revised What is an omega model?
added 43 characters in body
Feb
24
answered What is an omega model?
Feb
24
revised Errata for Rogers' Computability book
added 1 character in body
Feb
23
answered Errata for Rogers' Computability book
Feb
21
asked Errata for Rogers' Computability book
Feb
19
accepted Is definable $\emptyset$-definable?
Feb
19
comment Is definable $\emptyset$-definable?
@tomasz Thank you for the correction on the misplacement of the existential quantifier. Edited.
Feb
19
revised Is definable $\emptyset$-definable?
added 12 characters in body
Feb
18
comment Is definable $\emptyset$-definable?
@AsafKaragila I hoped for an absolute answer. If nobody protests for a few days, I will accept yours.
Feb
18
asked Is definable $\emptyset$-definable?