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New posts in examples-counterexamples
Spaces in which "$A \cap K$ is closed for all compact $K$" implies "$A$ is closed."
general-topology
metric-spaces
compactness
examples-counterexamples
Example of a non-Lipschitz $f \in \mathrm{C}^1(U)$ where $U \subseteq \mathbb{R}^n$ is a non-convex compact connected set
multivariable-calculus
examples-counterexamples
lipschitz-functions
Why does the Continuum Hypothesis make an ideal measure on $\mathbb R$ impossible?
real-analysis
measure-theory
examples-counterexamples
Primality test for numbers of the form $(11^p-1)/10$
elementary-number-theory
prime-numbers
examples-counterexamples
primality-test
lucas-lehmer-test
A reference for ring examples
abstract-algebra
reference-request
ring-theory
examples-counterexamples
When is a bornology on a uniformizable space induced by a uniformity?
general-topology
metric-spaces
examples-counterexamples
uniform-spaces
Counterexample: Continuous, but not uniformly continuous functions do not preserve Cauchy Sequences
real-analysis
examples-counterexamples
uniform-continuity
cauchy-sequences
Why is $T_1$ required for a topological space to be $T_4$?
general-topology
examples-counterexamples
separation-axioms
Mixing and Distributing Qualifiers ($\forall x$, $\exists x$)
logic
examples-counterexamples
predicate-logic
quantifiers
What's a good motivating example for the concept of a slice category?
category-theory
intuition
examples-counterexamples
big-list
motivation
is $\mathbb{R}^2\setminus \{(0,0)\}$ homeomorphic to $S^1$?
general-topology
examples-counterexamples
Non-isomorphic structures of the same cardinality which are elementary equivalent
logic
examples-counterexamples
cardinals
model-theory
How do you prove the $p$-norm is not a norm in $\mathbb R^n$ when $0<p<1$?
real-analysis
normed-spaces
examples-counterexamples
lp-spaces
Can we get un-obvious results by defining sophisticated topologies?
general-topology
soft-question
examples-counterexamples
big-list
"Numbers" bigger than every natural number
analysis
examples-counterexamples
extension-field
Other guises for the vector space $\mathbb{R}^n$?
linear-algebra
vector-spaces
examples-counterexamples
vector-space-isomorphism
Just How Strong is Associativity?
soft-question
examples-counterexamples
semigroups
magma
associativity
Advice on finding counterexamples
abstract-algebra
examples-counterexamples
Can a solved Sudoku game have an invalid region if all rows and columns are valid? [closed]
examples-counterexamples
puzzle
latin-square
sudoku
A counter example of best approximation
functional-analysis
approximation
examples-counterexamples
normed-spaces
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