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Enriched categories, topoi, abelian categories, monoidal categories, homological algebra.
9
votes
What kind of algebra is the class of ordered pairs equipped with the binary operation which ...
The property (*) is actually equivalent to a set of quasi-identities:
$$(x,y)=(x',y')\rightarrow x=x'$$
$$(x,y)=(x',y')\rightarrow y=y'$$
The converse implication you had ($\leftarrow$) is logically v …
1
vote
Is there any meaningful extension of the notion of a vector space for multisets?
For any vector space $V$ and any function $m:V\to\mathbb N$ you could say you have a vector space $V$ whose underlying set is a multiset with multiplicities given by $m$. This doesn't mean that the ve …
11
votes
Accepted
Usual technical term for replacing a set by the set of singletons of its members?
$A'$ is the discrete partition of $A$.
That is, we think of it as a partition of $A$ induced by the finest equivalence relation, the identity relation.
10
votes
When the automorphism group of an object determines the object
Under the Generalized Continuum Hypothesis, $$2^{\aleph_\alpha}=\aleph_{\alpha+1}\quad(\forall\alpha),$$
sets with no structure (so automorphisms are just bijections) is an example.
Namely, by
Cardi …
8
votes
Accepted
Define Turing machine with algebraic concepts/structures
Yes, there is now Pavlovic's characterization of Turing computability in terms of the monoidal computer, based on monoidal categories. http://arxiv.org/abs/1208.5205
3
votes
Accepted
Can we avoid the modal collapse in a certain Intuitionistic modal logic by abandoning ¬◯⊥ bu...
Notice that by the inference rule
$$\frac{M\supset N}{\bigcirc M\supset\bigcirc N}\tag{@}$$
we have
$$\frac{\bot\supset N}{\bigcirc \bot\supset\bigcirc N}$$
But $\bot\supset N$ always holds. So either …