0
votes
0answers
164 views
12 and 13-bit balanced Gray codes
I am trying to find a transition sequence for both 12 and 13 bit balanced Gray codes. I know there are some excellent papers on the topic of deriving these sequences available on t …
5
votes
1answer
213 views
Asymptotics for forbidden subwords
Fix an alphabet $A$ and consider words of length $n$ over $A$. Fix a set $B$ of $k$ forbidden subwords (subword is not necessarily connected, i.e. $abb$ is a subword of $abcb$). Ca …
2
votes
0answers
275 views
elementary Abel function of a polynomial
Is there an elementary real function $F$ such that
$F(1+F^{-1}(x))$ is a polynomial of degree at least 2 without real fixpoints.
3
votes
0answers
204 views
About Michael Barr immersion theorem for regular categories, and pretopos
In the article of M. Barr
"Representation of Categories" J. Pure Appl. Algebra, 41 (1986), 113–137
link: ftp://ftp.math.mcgill.ca/pub/barr/pdffiles/represen.pdf
M. Barr shows a c …
5
votes
1answer
461 views
subgroups of graph groups
Let $G$ be a graph group and let $S$ be a finitely generated subgroup of $S$.
What torsion can $H_1(S)$ have?
Let me put this in context: Let $Y$ be a graph, then the correspondin …
4
votes
2answers
500 views
Proper definition of a moduli problem
This question arose after I thought about Ben Webster's comments to this question.
There he asked me what was my definition of a moduli problem. When I came to think of it, I neve …
6
votes
1answer
443 views
Surgery and homology: a reference request
I need a reference (or a short proof) for the following statement:
Suppose a closed manifold $N$ is the result of a surgery (along an embedded sphere) on a closed manifold $M$. Th …
7
votes
2answers
479 views
elementary equivalence of infinitary symmetric groups
Two questions:
Suppose a and b are two uncountable cardinals. Consider the symmetric groups on sets of sizes a and b respectively (the symmetric group on a set is the group of al …
2
votes
5answers
584 views
Tetrad postulate: Implies or results from the metricity of the connection?
Hi,
I see that the tetrad postulate:
$\nabla_{\mu}e_{\nu}^{I}=\partial_{\mu}e_{\nu}^{I}-\Gamma_{\mu\nu}^{\rho}e_{\rho}^{I}+\omega_{\mu J}^{I}e_{\nu}^{J}=0$
Can be merely derived …
3
votes
1answer
178 views
extension of a vector bundle over punctured relative curve
Let $C$ be a curve (smooth projective over a field $k$ of positive char) and $p$ a rational point on $C$. Put $\dot{C}=C-{p}$ and $T=Spec R$, where $R$ is a noetherian $k$-algebra. …
3
votes
2answers
741 views
computation, algebra, logic
So a really simple way of describing a digital computer is to say that it is a device for performing boolean operations. You feed it a bunch of bit strings, which is a description …
4
votes
1answer
303 views
Automorphisms of $\pi_1$ induced by pseudo-Anosov maps
Suppose $X$ is an orientable surface with non-empty boundary and $f:X\to X$ is a pseudo-Anosov automorphism that acts identically on $H_1(X,\mathbf{Z})$. Let $x$ be a fixed point o …
0
votes
0answers
235 views
solving polynomials [closed]
Hello. While trying to find out how to find all the roots of any polynomial equation someone said this,"At least for real roots it can be completely solved by bracketing zeroes wit …
7
votes
2answers
369 views
Applications of classifying thick subcategories
So, relatively recently, Balmer introduced this notion of a spectrum for a tensor triangulated category and used it to prove a generalization of a classification theorem done in se …
0
votes
2answers
444 views
Why does twisting quasi-Hopf algebras work (as in majid’s article)
I can't understand this sentence i the article of Majid "Tannaka-Krein theorem for quasi-Hopf algebras and other results" about the reconstruction of a quasi-algebra (in fact its d …
