# Questions tagged [group-theory]

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### Is Group Theory useful in Computer Science in areas other than cryptography?

I have heard many times that Group Theory is highly important in Computer Science, but does it have any use other than cryptography? I tend to believe that it does have many other usages, but cannot ...
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### Permutation with stable partitions

I am searching a fast pseudo-random permutation function with the following requirements. Given a predefined set of values $V$ and an integer $k$. Split $V$ to $k$ subset, and iterate over any subset ...
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### Efficient calculation or estimation of “minimized combined Manhattan distance” between two sets of points

I’m attempting to write a heuristic for an implementation of A* search. The problem involves rearranging cells in a 3D grid until they match a particular solved state. I’m looking for options for a ...
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### Could someone break down this grouping problem for me?

I am trying to work through this programming problem but I can't progress because I genuinely don't understand what it is that its asking me. New Students are arriving at college. Initially the ...
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### Subset sum problem for permutations

Given permutations $g_1,\,\ldots, g_m \in S_n$ of size $n$ and target permutation $g \in S_n$, decide if there exists a subset of $\{g_1,\, \ldots, g_m\}$, which composition in some order (or, ...
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### Is it possible to interpret some Martin-Löf types as abelian monoids in such a way that any abelian monoid can be represented as a type?

For instance, I can interpret the unit type as the trivial monoid with one element. Non-dependent pairs $A \times B$ can be interpreted as the direct sum $A ⊕ B$ when $A$ and $B$ can both be ...
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### Is there any pseudocode of generating special orthogonal group which I can used for reference?

So, I want to include pseudocode of generating special orthogonal group for my thesis and I need something like a paper which I can refer to. I use this Scipy function to generate SO(n) and there is a ...
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### Algorithm to find the size of a quotient of a free group

Are there any algorithms to find the size of an algebraic quotient of a free group? It would take the generators as input and output the size. For example, an input could be something like {a,b: a^8=...
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### Detecting rotational symmetries of spatial structures

I have a spatial graph-like structure. The structure consists of vertices in the 3D space and connecting edges. Are there any algorithms available that would identify the rotational symmetries of ...
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### Algorithm for factoring elements of permutation groups?

You can solve a Rubik's cube by factoring its permutation into a sequence of "elementary" permutations (a subset of permutations that is sufficient to construct every other permutation in the group). ...
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### Transforming a byte with a subset of a small, fixed set of values and xor into any other value

If I have some collection of bits, -- a byte, say -- of arbitrary value then I can transform it into some other value by means of exclusive-oring it with a subset of (in this case) eight fixed values, ...
466 views

### How to calculate the minimum number of groups, by grouping groups with capacity together?

I need to group cars (and their passengers) with other cars, and I don't know how to approach this problem. If I have, for example, 3 cars. Car A with 7 seats and 2 passengers (3/7 because of the ...
738 views

### Group isomorphism to graph ismorphism

In reading some blogs about computational complexity (for example here)I assimilated the notion that deciding if two groups are isomorphic is easier than testing two graphs for isomorphism. For ...
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### How to compute quotient subgroup efficiently?

Let $G$ be a finite group given by the table representation and a normal subgroup $H$ of $G$ is given. I want to compute $G/H$ that is quotient group. Model of computation is RAM For all pair of $a$...
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### Is finite abelian group isomorphism in Log Space?

Definition : An abelian group is a group in which the result of applying the group operation to two group elements does not depend on the order in which they are written Input : Two finite abelian ...
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### Representing Integral domains in computer memory?

Earlier I wrote this question about an algorithm computed on an integral domain. However as commented I didn't suggest any particular ways of storing an integral domain in computer memory. I set out ...
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### Is there an algorithm for determining whether a element is Prime?

Is there an algorithm that can take an element on an arbitrary integral domain, and determine whether or not it is prime on that ring? It is pretty trivial to do so on a finite integral domain, ...
136 views

### Generating all directed multigraphs

I am trying to find an algorithm that generates all directed multigraphs with a given number of vertices and arcs up to isomorphism (no two generated graphs should be isomorphic). I also want to allow ...
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### Applications of Graph Automorphisms

I've seen the topic of the automorphism group appear in several introductory graph theory books I've looked at. It always feel oddly disjointed and poorly motivated to me. Is there any practical (or ...
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### Bridge theorems for group theory and formal languages

Is there some natural or notable way to relate or link math groups and CS formal languages or some other core CS concept e.g. Turing machines? I am looking for references/applications. However note ...
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### How to find the symmetry group of a polynomial

Say I have a polynomial in $n$ variables of maximum degree $m$. I define its symmetry group to be the subgroup of the permutation group which fixes the polynomial when it acts on the variables. ...
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### What is the name of the word problem for free groups under straight line program encoding?

I believe that the word problem is the problem to decide whether two different expressions denote the same element of a suitably defined algebraic structure. For simplicity, let us focus on free ...
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### Sifting algorithm for group generated by a set

On page 38 of "Lecture Notes in Computer Science" by Christoph M. Hoffmann, there is an algorithm (ALGORITHM 2). I have some confusions. Why it is written that an entry $M_{i,j}, j < i$, cannot ...
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### Can you form a group with assembly instructions under the MIPS-32 architecture?

Would it be possible to form such a group using the ADD instruction and the NOT instruction?
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### What use are groups, monoids, and rings in database computations?

Why would a company like Twitter be interested in algebraic concepts like groups, monoids and rings? See their repository at github:twitter/algebird. All I could find is: Implementations of ...
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### What can be said in general about a homomorphism between two regular languages?

In other words: is a homomorphism always guaranteed to exist between two arbitrary regular languages? If not (which I suspect), are there only a finite number of classes of languages, for which we can ...
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### Algorithm: Cracking the Safe

A safe is protected by a four-digit $(0-9)$ combination. The safe only considers the last four digits entered when deciding whether an input matches the passcode. For instance, if I enter the stream \$...
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### algoritm to convert a monoid into an automaton [closed]

In literature, is there an algoritm to convert a monoid into an atomaton? I am looking for references/applications.