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Apr
28
comment What book about algebraic combinatorics is it?
These 4 books (and the same for the other one with the title "Combinatorial Mathematics") seem (just looking at the previous fragment and at the available table of contents) so terrific at the current version, that I would like to encourage Douglas West to make it now available in whatever format he decides (online current draft, publsihed book, etc). If anybody is in contact with him, please send the message.
Apr
28
comment What book about algebraic combinatorics is it?
Does anybody know a place where one can by this book (indeed the 4 volumes)? I am unable to find any information on the web (isbn, etc)
Mar
21
comment A supposedly “trivial” logic question
@user292595: You didn't get my point. The important part is that you only allow "conjunction" and "disjunction".
Mar
20
comment A supposedly “trivial” logic question
In general it is non-sense to say what you are forbidding (in this case negation), the important is what you are allowing. Since you have forgotten this part, I find your question not precise enough. For example, what happens if you allow "implicacion (binary)" and "falsum (constant)" as primitive and you don't allow "negation (unary)" as primitive?
Mar
8
answered Ideas for a history of math paper (with an emphasis on the mathematics), having to do with 19/20th century logic?
Mar
7
comment Can we simultaneously freely adjoin both limits and colimits to a category?
Do you know some link to access this paper by Joyal?
Mar
2
comment Is there a name for posets in which every nonempty finite subset with a lower bound has an infimum?
This is very close to the dual notion of a dcpo (except for only looking at finite subsets). Take a look at the notion of "filtered complete partial order" in en.wikipedia.org/wiki/Directed_complete_partial_order
Feb
29
comment What does “irreducible polynomial modulo $p$” mean?
I would say this answer is wrong. The right answer is "irreducible in the ring $\mathbb{Z}_p [x]$".
Feb
27
comment Is there a name for posets in which every nonempty finite subset with a lower bound has an infimum?
Let me point out that by "associativity" reasons such property is equivalent to requiring that every finite subset of cardinal 2 which is lower-bounded has an infimum. But I am not familiar with any name for such notion.
Feb
27
comment What congruences of abelian monoids can be extended to (ideal) congruences of polynomials?
@J. E. Pin: If $\theta$ is a congruence of $\langle K[x_1,...,x_n], +,\cdot\rangle$ then I am just thinking in considering the monoid congruence $\theta \cap (M \times M)$ where $M$ is the subset of monic monomials (i.e., what i called above $Mon(x_1,...,x_n)$). In the other words, if we have an ideal $I$ of the ring $\langle K[x_1,...,x_n], +,\cdot\rangle$, the congruence (among monic monomials) is the one that identifies two monic monomials when their diference is an element of the ideal $I$.
Feb
26
revised What congruences of abelian monoids can be extended to (ideal) congruences of polynomials?
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Feb
26
asked What congruences of abelian monoids can be extended to (ideal) congruences of polynomials?
Feb
2
comment Linear Algebra book for beginners
I suggest you the online version of a "A First Course in Linear Algebra" by Robert A. Beezer. It is avaiable from linear.ups.edu/download.html and what it is really great is the possibility to use the (free) software "sage" for the examples.
Jan
15
comment “Minimal upper bounds” in a categorical setting
@Eric: That was one of my attempts, but in this case it happens that corproducts do not satisfy this "minimality" (if I am not worng).
Jan
15
revised “Minimal upper bounds” in a categorical setting
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Jan
15
comment “Minimal upper bounds” in a categorical setting
@Eric: I am asking for a categorical notion of "a minimal upper bound" as oposed to "the minimum upper bound". In particular, the unicity (up to isomorphism) needs to be lost.
Jan
14
asked “Minimal upper bounds” in a categorical setting
Jan
6
revised Number of k-ary monotone maps from 1..n+1 to 1..n+1.
added 1 character in body
Jan
6
comment Number of k-ary monotone maps from 1..n+1 to 1..n+1.
@Random: Thanks. As you have pointed out, Dedekind numbers provide an answer for the case n=1.
Jan
6
revised Number of k-ary monotone maps from 1..n+1 to 1..n+1.
edited body