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Algebra
  • Member for 6 years, 8 months
  • Last seen more than 4 years ago
8 votes
3 answers
773 views

$AB-BA=A^k$, then $A$ is not invertible

7 votes
2 answers
75 views

Properties of $\{x\in X\mid f(x)=||f||\}$

6 votes
2 answers
419 views

Direct sums in projective modules

5 votes
1 answer
106 views

Prove that if $f$ differentiable in $x^*$ and $f(x^*)=0$, then $\liminf_{x\to x^*}\frac{|f(x)|}{||x-x^*||}=0$ if $n>1$

4 votes
1 answer
884 views

Non cyclic group of order $8$ having exactly one element of order $2$

4 votes
1 answer
126 views

Product of algebraic numbers

4 votes
1 answer
113 views

Evaluate $\int_0^1\ln(\frac{1+x}{1-x})dx$ using power series

4 votes
3 answers
164 views

Convergence of $\sum_{n=1}^\infty \frac{1}{n^{a_n}}$

3 votes
1 answer
92 views

Boundedness of a subset using boundedness of linear functionals

3 votes
1 answer
620 views

Analytic and bounded implies uniform continuity

3 votes
1 answer
617 views

Maximal ideals are prime ideals in the non-commutative case

3 votes
3 answers
140 views

Integral of an increasing function over subset of unit interval

3 votes
2 answers
717 views

Quotient of $[-1,1]$ homeomorphic to unit circle

3 votes
1 answer
925 views

Use contour integral to show $\int_0^{2\pi}\frac{\mathrm dt}{(1+\cos(u)\cos(t))^2}=\frac{2\pi}{\sin^3(u)}$ for $u\in(0,\frac{\pi}{2})$

3 votes
0 answers
590 views

Sum of two sequences converges and one of them is bounded implies they both converge

3 votes
1 answer
471 views

Sequence of polynomials converging to $\frac{1}{z}$ [duplicate]

3 votes
3 answers
73 views

Group of matrices which share a fixed eigenvector is noncommutative

3 votes
3 answers
76 views

Constructing a new basis

3 votes
1 answer
55 views

What kind of radical makes sense?

2 votes
1 answer
110 views

Find non convergent Cauchy sequence

2 votes
2 answers
331 views

Injective module

2 votes
1 answer
1k views

Nilpotent Jacobson radical

2 votes
1 answer
53 views

Left divisors are right divisors in an algebra where every element is algebraic

2 votes
0 answers
535 views

Reference request fundamental group of surface of genus $g$ and $n$ boundary components

2 votes
1 answer
330 views

Semisimple iff every maximal right ideal is a direct summand

2 votes
4 answers
188 views

How to show that $x^{\tfrac{1}{p}}\leq \frac{1}{p}x+\frac{1}{q}$ [closed]

2 votes
3 answers
78 views

Find a subset with a specific Lebesgue measure

2 votes
1 answer
106 views

Unique 2-dimensional irreducible representation

1 vote
1 answer
82 views

Lebesgue integrability of $\frac{f(x)}{x}$

1 vote
1 answer
64 views

$\lim_{r\to\infty}\int_{c-ir}^{c+ir}z^{-\lambda}(\log(z))^{-1}dz$