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2
votes
scott continuity, sub additivity
The two notions are equivalent if you take continuity with respect to the Scott topology (and not the one you define with the closure operators).
Let $(X,\leq_X)$ and $(Y,\leq_Y)$ be dcpos. We say th …
1
vote
1
answer
81
views
Cycling through $\{0,1\}^n$ by shifting and applying a $n$-ary function
This question is motivated by Linear Feedback Shift Registers, which cycle through $\{0,1\}^n \setminus \{(0,\ldots,0)\}$ by shifting and applying a small set of XOR operations.
Let $n>1$ be an intege …
2
votes
Accepted
If $f : [-a,a] \rightarrow \mathbb{IR}$ is Scott continuous, why are $f^-$ and $f^+$ measura...
First, we note that $\mathbb{IR}$ is ordered by $[a,b] \sqsubseteq [c,d]$ iff $[c,d] \subseteq [a,b]$, which makes $\mathbb{IR}$ into a domain. Now suppose $f: [-a,a]\to \mathbb{IR}$ is Scott-continuo …
1
vote
If $f : [-a,a] \rightarrow \mathbb{IR}$ is Scott continuous, why are $f^-$ and $f^+$ measura...
This answers @user3078439's question in his comment to my original answer.
First, a short argument to show that if $P,Q$ are domains and $f:P\to Q$ is Scott-continuous, then $f$ is order preserving.
…
3
votes
1
answer
179
views
Non-trivial parity maps in graphs
(This question actually arose in real life when dealing with status bits with mutual influence.)
Let $G=(V,E)$ be a connected, simple, undirected graph with $|V| \geq 2$. For $v\in V$, let $N_G(v) = …
2
votes
1
answer
162
views
Is this cycling problem computable?
We have a group of $n$ people who must make a journey of length $d$. They are to start together, and their goal is to arrive at the destination at same time. They have a single bicycle, which they rid …
4
votes
2
answers
203
views
Hamilton cycles in $\{0,1\}^n$ with fixed Hamming distance
Let $n>1$ be an integer. For $a,b\in \{0,1\}^n$ let $d_h(a, b)$ denote the Hamming distance of $a$ and $b$. For $k\in \{1,\ldots,n-1\}$ let $H(n,k)$ be the graph on $\{0,1\}^n$ given by the edge set $ …
3
votes
0
answers
105
views
Hamiltonian path in $\{0,1\}^n$ with rotations and bit-flip in position 0
We consider any non-negative integer as an ordinal, that is $0=\emptyset$ and $n=\{0,\ldots,n-1\}$ for every positive integer. Let $\{0,1\}^n$ denote the set of $\{0,1\}$-vectors of length $n$.
Define …
2
votes
0
answers
149
views
Binary operation approximating "addition" on $2^\omega$
Motivation. In computer science, addition of integers $a+b$ can be approximated by a very fast operation: $(a,b)\mapsto (a\oplus b) \oplus ((a\land b) \ll 1)$, where $\oplus$ denotes bitwise XOR, $\la …
5
votes
1
answer
226
views
Cycling through $\{0,1\}^{(2^n)}$ such that all Hamming distance appear equally frequently
Let $n\in\mathbb{N}$ be a positive integer. Let $\{0,1\}^{(2^n)}$ be the set of $0,1$-sequences of length $2^n$. For $a,b\in \{0,1\}^{(2^n)}$ let $d_h(a,b)$ be the Hamming distance between $a$ and $b$ …
2
votes
1
answer
57
views
Left-shift cycle generating maps $f:\{0,1\}^{c_0}\to\{0,1\}$ for fixed length $c_0$
This is a strengthening of an older question.
Is there a positive integer $c_0$ with the following property?
For every integer $n\geq c_0$ there is a function $f:\{0,1\}^{c_0}\to\{0,1\}$ such that th …
5
votes
1
answer
423
views
Is the set of generalized Fermat triples computable?
Is $\;\big\{(a,b,c)\in\mathbb{N}^3: \big(\exists m,n,\ell \in (\mathbb{N}\setminus\{0,1,2\})\big): a^m + b^n= c^\ell\big\}\;$ computable?
6
votes
1
answer
359
views
Large subgroups of Knuth's non-associative "group" on ${\cal P}(\mathbb{N})$
Donald Knuth introduced a fast, bit-wise approximation to integer addition by $$(a,b) \mapsto a \, ^{\land} \, b \, ^{\land} \, ((a \text{ & } b) \ll 1)$$
where $a,b$ are given in binary and $\,^{\lan …
13
votes
0
answers
255
views
Is the set of power matrices decidable?
Let $\text{Mat}(n\times n,\mathbb{Z})$ denote the collection of integer $n\times n$ matrices. We say $M\in \text{Mat}(n\times n,\mathbb{Z})$ is a power matrix if there is an integer $k>1$ and a matrix …
4
votes
1
answer
160
views
Is sum-balanceability computable?
Let $\mathbb{N}$ denote the set of positive integers, and let $G=(V,E)$ be a finite simple, undirected graph. Given $f:V\to \mathbb{Z}$ we define the neighborhood
sum function $\mathrm{nsum}_f:V\to\ma …