# Questions tagged [reference-request]

Reference-request is used when the author needs to know about work related to the question.

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### The tree augmentation problem, but with hyperlinks

In the (Weighted) Tree Augmentation Problem, we are given a tree $T = (V,E)$ and a set of additional edges $L$ called links with non-negative costs. Each link $\ell = (u,v)$ covers the tree edges ...
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### Publications on left recursion and PCRE regex engine

Is there any paper (or at least technical report / preprint or even thesis) mentioning that regex engines cannot match expressions that contain "left recursion" (explained below)? I am ...
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### Are there logical devices similar to "existential variables" or "blank nodes" of Semantic Web?

In Semantic Web, alongside permanent names of things also "temporary names" named "existential variables" or "blank nodes" denoted as "_:label" are used. All ...
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### Name for set of vertices that are pairwise within distance two

A 2-stable set (or a distance-two independent set) of a graph $G$ is a set of vertices which are pairwise at a distance greater than 2 in $G$. Is there a name for a set of vertices which are pairwise ...
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### Nondeterministic communication complexity

Let $X$ and $Y$ be finite sets and $f : X \times Y \to \{0,1\}$. I am confused about the definition of the deterministic communication complexity of $f$, denoted $N^1(f)$, or rather about the ...
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### Are there any references for this theorem of Lercher?

Let $\Delta = \lambda x.(x)x$ and consider $\Omega = (\Delta)\Delta$. Then $\Omega$ is exactly the only $\lambda$-term of the form $(\lambda x.t)v$ such that $(\lambda x.t)v=t\{v\ /\ x\}$. Does ...
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### Complexity of detecting general position in the plane?

What is the complexity of detecting whether a given set of points in the plane is in general position? This surely must have been studied, but a quick search turns up nothing. For concreteness, let'...
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### Type theory and fixed points of datatypes

For the purposes of this question, say that a datatype is a type constructor with one type parameter (this is sometimes called a type operator). In Haskell, we can define a fixed point ...
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### A counter example for the set mean objective

Let $\mathcal{P} = \{P_1, \cdots,P_n\}$ be a family of finite point sets in $\mathbb{R}^d$, each having at most $m$ points. Consider the following objective function \begin{align} cost(\mathcal{P},c) =...
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### Complexity of optimal elimination for a planar tensor network

Edit Dec 15 it's not obvious this problem is tractable when further restricting to trees, see cs.SE question Suppose we need to sum out variables in a tensor network (a factor graph where each ...
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### Construction of arbitrary functions with exponential-size $MODp \circ MODq$ circuits

It is mentioned in multiple papers [1], [2] that $MODp \circ MODq$ circuits for two distinct primes $p, q$ can compute arbitrary functions in exponential size. However, [1] provides no citation for ...
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### Full names of C. K. Chow and C. N. Liu

Where can I find the full names of C. K. Chow and C. N. Liu, of the Chow-Liu tree fame? https://en.wikipedia.org/wiki/Chow%E2%80%93Liu_tree https://ieeexplore.ieee.org/document/1054142
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### Reference request for linear algebra over GF(2)

I have been looking for materials on the linear algebra over $GF(2)$ but so far I haven't found any substantial textbooks or notes on this subject. In fact in one of the notes I found the introduction ...
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### Expressiveness of pushdown automata whose stack height sequence is unambiguous

I consider pushdown automata on an alphabet $\Sigma$, which are intuitively finite automata with a stack. Formally, a pushdown automaton $A = (Q, q_0, F, \Gamma, \Delta)$ is a finite set $Q$ of states,...
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### Are the non-lazy / non-weak semantics of the $\lambda$-calculus related to weak evaluation?
Vague question The most common semantics of the call-by-name $\lambda$-calculus (Hyland/Wadsworth’s observational equivalence $\approx_\text{HNF}$ and Morris’s observational equivalence \$\approx_\text{...