Questions tagged [computational-algebra]
Computational algebra is an area of algebra that seeks efficient algorithms to answer fundamental problems concerning basic algebraic objects (groups, rings, fields, etc.). For questions about generic computer algebra systems, use [tag:computer-algebra-systems].
322 questions
2 votes
1 answer
65 views
Birth definition in persistent homology theory
I have some confusion about the definition of birth time, and I hope someone can clarify a few things. I am reading "Computational Topology: An Introduction" by Edelsbrunner and Harer. They ...
2 votes
0 answers
117 views
How to algorithmically tell if two matrices are equivalent up to an invertible matrix on the left and a permutation matrix on the right?
Let’s fix some natural $0 < m < n$ and consider matrices $m \times n$ with rational coefficients. Let’s call such matrices $A$ and $B$ equivalent iff there are an invertible $m \times m$ matrix $...
0 votes
0 answers
33 views
Statements about dimension of singularity loci in families of polynomials
I am working with some homogeneous polynomials $f\in \mathbb C[x_1, \ldots, x_n]$ belonging to families $\mathcal F$ over $\mathbb C^k$, i.e. I am considering $$f=\sum a_Ix^I, \qquad\qquad a_I\in \...
6 votes
0 answers
135 views
Extending proofs via computational algebra from $\mathbb Q$ to $\mathbb C$
Let $R=\mathbb Q[x_1, \ldots, x_n]<R'=\mathbb C[x_1, \ldots, x_n]$. I often can prove results for $R$ using computational algebra packages (e.g. Macaulay2) but I am never too sure if they extend to ...
4 votes
2 answers
329 views
Is there any algorithm which can find a common divisor of two polynomials modulo $p^k$?
Let us consider two monic polynomials $f(X), g(X) \in \dfrac{\mathbb{Z}}{p^k\mathbb{Z}}[X]$. Now, we call $h(X)$ is a divisor of $f(X)$, if there exists a $l(X) \in \dfrac{\mathbb{Z}}{p^k\mathbb{Z}}[X]...
1 vote
0 answers
150 views
If resultant $T(y) = \mathrm{Res}_{x}(f(x), y - g(x))$ have a nontrivial factors then can $f(x)$ also have a nontrivial factors?
This is a follow-up question to this question. In that question, we learned that if, $T(y) = \mathrm{Res}_{x}(f(x), y - g(x))$ , then $T(g(z))$ is divisible by $f(z)$. Now, my question is: If $T(y) = ...
0 votes
2 answers
64 views
Problems with monomial orders and monomial divisibility
I have a doubt concerning monomial orderings. I'm reading Cox, Little, O'Shea book Ideals, Varieties and Algorithms. Well, they say that a monomial $x^\alpha$ divides a monomial $x^\beta$ if there ...
3 votes
1 answer
101 views
Toric arrangements and system of polynomial equations
I am working on some problem on toric arrangements at the crossroad between topology, combinatorics and algebraic geometry. $\textbf{Setting}$ Let $m,n\geq1$ and let \begin{equation*}\mathcal{S}=\left\...
2 votes
0 answers
68 views
What is the order of the torsion subgroup of $𝐻_1(\Gamma_1(193),\Bbb{Z})$?
I'm trying to compute the torsion subgroup of the first integral homology group $𝐻_1(\Gamma_1(193),\Bbb{Z})$ This group arises from modular symbols associated to the congruence subgroup $\Gamma_1(193)...
6 votes
1 answer
137 views
Finding a presentation of the group generated by a translation and a rotation
In the group of isometries of the plane, let $r$ be a rotation by $\frac{2\pi}5$ radians and let $s$ be a translation. I'd like to find a finite presentation of the subgroup $G=\langle r,s\rangle$. ...
0 votes
0 answers
65 views
A-invariant subspaces of cyclic generalised linear eigenspaces
I wrote a proof for the following statement: Let $\mathbb{F}$ be a finite field and $V = \mathbb{F}^n$ for $n \in \mathbb{N}$. Furthermore let $A \in \mathrm{GL}(n,\mathbb{F})$ with $\mu_A = \chi_A = ...
1 vote
0 answers
57 views
What can be computed algorithmically on cohomology of higher-dimensional varieties?
There are algorithms for computing explicitly a basis of holomorphic differentials for algebraic curves given as the vanishing locus of a polynomial $f(x, y)$. Take for example a smooth hyperelliptic ...
1 vote
1 answer
143 views
Cone of rank three between two cones of rank four?
Let $P$ be the nonnegative orthant in ${\mathbb R}^4$, $P={{\mathbb R}_+}^4$. For a finite set of vectors $S \subseteq P$, the cone $Cone(S)$ generated by $S$ is the set of all linear combinations of ...
0 votes
0 answers
47 views
Gröbner bases computation for not fully specified polynomials
Gröbner bases computation works on several computer systems. I have this question. Is it possible to compute (in any of the systems, eventually in which?) Gröbner basis for integer polynomials, in ...
2 votes
1 answer
123 views
How fast is taking the quotient of a group by a subset?
Let $G$ be a finite group, and assume you have some computational representation of $G$ that allows efficient iteration through its elements, constant-time checks for equality between elements, and ...