Questions tagged [abstract-algebra]

For questions about monoids, groups, rings, modules, fields, vector spaces, algebras over fields, various types of lattices, and other such algebraic objects. Associate with related tags like [group-theory], [ring-theory], [modules], etc. as necessary to clarify which topic of abstract algebra is most related to your question and help other users when searching.

Abstract algebra is the study of algebraic objects, i.e. sets endowed with one or more operations on the elements of those sets. In particular, the study of abstract algebra considers the algebraic structures and properties of which such operations induce. It can be considered as the generalization of the study of the algebraic structure of the integers and real numbers (arithmetic), or the study of matrices and vector spaces (linear algebra).

Some algebraic objects are monoids, groups, rings, fields, vector spaces, modules, algebras, and categories, among many other less prominent objects.

Examples

  1. The set of non-negative integers $\mathbb{N} = \{0,1,2,3,\dotsc\}$ is a monoid under the operation $+$.

  2. The integers $\mathbb{Z} = \{\dotsc,-1,0,1,\dotsc\}$ under the binary operation of $+$ form a group.

  3. Furthermore, $\mathbb{Z}$ has the structure of a ring when you consider it as being equipped with both addition and multiplication.

  4. The real numbers $\mathbb{R}$ with their usual addition and multiplication form a field.

  5. The set of $n\times n$ matrices with entries in $\mathbb{R}$ with matrix addition and multiplication form a ring.

  6. The set of $1\times n$ vectors over the real numbers, with vector addition, and multiplication by elements of the $n\times n$ real matrices on the right are an example of a module for the ring of matrices.

In addition to studying the objects themselves, abstract algebra considers homomorphisms between the objects and various constructions and tools, which are useful for studying the objects.

85022 questions
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Definition of the Tate group associated with $p$-divisible groups

Let $A$ be an abelian group, $p$ a prime number and $p_A:A \rightarrow A$ the multiplication by $p$. Let $A\left[p^n\right]$ be the kernel of $p_A$ composed $n$ times with itself. Then Lang, in his algebra p. 50, defines the Tate group $T_p(A)$…
Manos
  • 25,833
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Isomorphism of a quotient algebra in K[t]

Let $K$ be an algebraically closed field and consider the $K$-algebra $K[t]$ i.e the $K$-algebra of all polynomials in the indeterminate $t$ with coefficients in $K$. Now consider an ideal $I$ of $K[t]$ then since $K[t]$ is PID we have that $I=…
Learner
  • 227
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Confusing part of Grobner Basis section of Dummit and Foote

So, I was reading section 9.6 in Dummit and Foote, and I got a bit confused by the proof below, particularly the part where they claim $f_{i-1}'-f_i'=S(f_{i-1}, f_i)$. This is on page 323. For example, let $f_1=x^3y$ and let $f_2=x^2y^2$. Then…
Nishant
  • 9,155
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Is the quotient ring $\mathbb{Z}_4[x]/$ a vector space?

I know that if p is a prime number, then the quotient ring $$\frac {\mathbb{Z}_p[x]}{ \langle x^n-1 \rangle }$$ is a vector space over $\mathbb Z_p$. What if p is not a prime? Certainly, $\mathbb{Z}_m[x]$ is not a Euclidean domain while m is not…
faith
  • 1,006
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Factor Ring fundamental question

We have a factor ring R/I for a ring R and an ideal I. I understand R/I = {r + I , r e R} and that each element is a coset of I. I also understand that R/I is a ring under the defined operations +, x on R/I (which i wont write out here) Now, what I…
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$R$ is a ring. $\forall 0\ne a\in R \exists ! b\in R; aba=a$. Can I conclude that $R$ is a ring with identity? How?

$R$ is a ring, containing more than one element, such that $\forall 0\ne a\in R \exists ! b\in R; aba=a$. Here's what I did in the very first place: $(aba)a^{-1}=aa^-1 \text{ and } a^{-1}(aba)=a^{-1}a\Longrightarrow \left\{ \begin{array}{rl} ab=1…
Mill
  • 917
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prove that $f(x)=10x^4-18x^3+4x^2+7x+16 \in \mathbb{Z}[x]$ is irreducible in $\mathbb{Q}[x]$

I want to prove that $f(x)=10x^4-18x^3+4x^2+7x+16 \in \mathbb{Z}[x]$ is irreducible in $\mathbb{Q}[x]$. If $f(x)$ can be analyzed in a product of two non-constant polynomials with coefficients $\in \mathbb{Q}$,then $f(x)$ can be analyzed in a…
evinda
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Is $ G = \frac{\mathbb{Z}_{2} \times \mathbb{Z}_4 \times \mathbb{Z}_{8}}{<(1,2,4)>}$ isomorphic to..

Is $ G = \frac{\mathbb{Z}_{2} \times \mathbb{Z}_4 \times \mathbb{Z}_{8}}{<(1,2,4)>}$ isomorphic to $\mathbb{Z}_8 \times \mathbb{Z}_4$? I thought I might try reducing $\mathbb{Z}_{2} \times \mathbb{Z}_4 \times \mathbb{Z}_{8}$ into more decomposition…
Ozera
  • 2,050
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A problem from Isaacs's book

Suppose that F ⊆ E ⊆ L and suppose α ∈ L is algebraic over F . Let f := min E (α) (the minimal polynomial of α over E) I need to show all roots of f in any field extension of L are algebraic over F . Can anyone help with this one, thanks
DKding
  • 53
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Adjoining elements to a ring.

I have a question in Artin's Algebra, about adjoining elements on page 339. Proposition 11.5.5 says: Let $R$ be a ring, and let $f(x)$ be a monic polynomial of positive degree $n$ with coefficients in $R$. Let $R[\alpha]$ denote the ring $R[x]/(f)$…
Curran
  • 350
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are the functions also $1-1$ and surjective

Knowing that $f: X \to Y \text{ and } g:Y \to Z$ are $1-1$ and surjective,are then also $f^{-1}: Y \to X$ and $g \circ f:X \to Z$ $1-1$ and surjective or just $1-1$ ?
evinda
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Why is group of automorphism of $\mathbb{Q}[\sqrt[3]{2}]/\mathbb{Q}$ is of order 1

the question is as stated in the title. Why is this that $\mathbb{Q}(\sqrt{2})/\mathbb{Q}$ is Galois (as the Galois group has two elements), but the corresponding one for third root of two is not Galois because the Automorphism group in…
HoangDT
  • 23
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existence of a subgroup with fixed index

Let $G$ be a finite $p$-group and $K$ be a normal subgroup. I want to show that there exists a normal subgroup $N$ of $G$ such that $N \leq K$ and $[K:N]=p$. I tried in this way: from Sylow's theorem, there exists a normal series $G=G_0 \rhd G_1…
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$x^3+x+1$ irreducible over $\mathbb{F}_2$, $\theta$ root, compute powers of $\theta$

Problem statement: Show that $x^3+x+1$ is irreducible over $\mathbb{F}_2$ and let $\theta$ be a root. Compute the powers of $\theta$ in $\mathbb{F}_2$. I am having trouble computing the powers of $\theta$. $x^3+x+1$ is irreducible, since any cubic…
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$T :V\rightarrow\ V$ be a linear transformation with dimension of Range of $T = k$.

Let $V$ be a finite dimensional vector space over $\mathbb R$ and $T :V\rightarrow\ V$ be a linear transformation with dimension of Range of $T = k$.Then how to show that $T$ can have at most $k + 1$ distinct eigenvalues? somebody please help…
liesel
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