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7
votes
1
answer
463
views
Are countable FC-groups maximally almost periodic?
A group G is said to be maximally almost periodic if there is an injective homomorphism from G into a compact Hausdorff group. … My question is whether every discrete countable FC-group G is maximally almost periodic. …
1
vote
0
answers
41
views
Do maximally almost periodic groups embed homeomorphically into their Bohr compactifications? [duplicate]
If $G$ is a Hausdorff topological group and $bG$ is its Bohr compactification, Wikipedia says that $G$ is called maximally almost periodic (MAP) if and only if the natural map $i : G \to bG$ is injective …
3
votes
1
answer
223
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Almost periodic functions and the property A
.$$
Now consider an almost periodic function $f$. … It is easy to see that hypothesis 1 is true for the periodic case. But I even don't know what to do with special almost periodic case.
For the general case, i.e. …
1
vote
A certain class of representations
The buzzword to look for is "maximally almost periodic". This is part of the theory of Bohr Compactifications. Start with a (locally compact) group $G$. … By definition, this means that $G$ is "maximally almost periodic" (MAP). …
3
votes
1
answer
211
views
About understanding manifold structure on WAP compactification of $\Bbb{C} \rtimes \Bbb{T}$
A continuous bounded function $f$ on $G$ is called (weakly) almost periodic if the set $L_Gf$ of left translates is relatively compact in the (weak) norm topology. … Then $f$ is uniformly continuous with respect to the left and right uniform structures on $G$ and all (weakly) almost periodic functions forms an abelian $C^*$-algebra with the norm of uniform convergence …
2
votes
Accepted
Does each discrete solvable group admit an injective homomorphism to a compact topological g...
According to Proposition 3.3 from Dikranjan and Toller [Topology and its Applications 159 (2012) 2951-2972], the Heisenberg group H_K over an infinite field K of characteritic 0 is not maximally almost … periodic. …
6
votes
0
answers
120
views
Aperiodic packings of the plane with disks of multiple radii
Does there exist a finite set of radii such that some aperiodic packing of the plane by disks of those radii is believed to achieve the maximal packing density (not achieved by any periodic packing)? … [Note to administrators: I wanted to add “aperiodic” or “quasicrystal” or something like that as a tag; I settled for “almost-periodic-function”, but please re-tag as appropriate.] …
19
votes
Countable subgroups of compact groups
As a complement to Reid's answer: a finitely generated group is maximally almost periodic if and only if it is residually finite. …
17
votes
Accepted
Countable subgroups of compact groups
Such groups are called "maximally almost periodic". Take a look at this paper for a more in-depth treatment. …
10
votes
0
answers
508
views
flexibility of almost contact ``Reeb'' vector fields
Can I deform the pair $(\alpha, \omega)$ so that the only minimal invariant sets of the resulting vector field are non-degenerate periodic orbits? … I am now allowing a larger family of deformations (since the 2-form is allowed to vary among maximally non-degenerate 2-forms, dropping the condition of being closed.) …
5
votes
Bohr compactification as a topological compactification
Note: I have restricted my answer to abelian $G$; $\iota$ can be defined for any topological group, but your question only makes sense when $\iota$ is injective, i.e. for “maximally almost-periodic” $G …
-2
votes
1
answer
116
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Mismatch between equivalent definitions of the Bohr compactification of the reals
The maximal ideal space of the set $AP(\mathbb R)$ of almost periodic functions. i.e the set of multiplicative linear functionals under the pointwise topology. …
4
votes
1
answer
172
views
Compactness modulo symmetries of critical NLS solution
A function $u\in C_{t,loc}^{0}L_{x}^{2}(I\times\mathbb{R}^{N})$ is almost periodic modulo $G$ if the quotiented orbit $\{Gu(t) : t\in I\}$ is a precompact subset of $G\backslash L_{x}^{2}(\mathbb{R}^{N … Equivalently, $u$ is almost periodic modulo $G$ if there exists a compact subset $K\subset L_{x}^{2}(\mathbb{R}^{N})$ such that $u(t)\in GK$, $t\in I$. …
4
votes
1
answer
208
views
When entropy SRB measure is zero
The maximal open set $U$ with this property is called the basin of $f$.
It is well known that every transitive Anosov diffeomorphism carries a unique SRB measure. … My solution : Let $p \in M$ be a periodic point associated to $\delta, S$ and $\{x, f(x),..., f^{n-1}(x)\}$ in the periodic exponential specification property. …
5
votes
Accepted
Bohr compactification as a topological compactification
unfortunate, as $u$ is not a compactification in the sense usually used in topology, unless $G$ was compact to begin with
(in fact, $u$ is rarely injective - groups for which $u$ is injective are called "maximally … almost periodic"). …