# Questions tagged [set-theory]

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### Proving the Equivalence of REGEX r^n and r^{..n} when r Is Nullable

Im seeking clarification and a rigorous proof regarding the equivalence of r^n and r^{..n} in the context of formal languages, particularly when r is nullable. To clarify the terminology: r denotes ...
78 views

### Can lambda-calculus, or other formal systems / calculi, be represented using set theory?

Background: I'm a fresh grad student looking into interesting ideas I have. I do not have any theoretical computer science background beyond basic Theory of Computation stuff from undergrad. If I have ...
1 vote
96 views

### Do realizable systems always have some non-well-founded sets?

Suppose we are standing outside a realizable system which admits CZF or a similar constructive set theory. Then consider the following: LEM is not realized (e.g. this MSE answer) The traditional ...
86 views

### Existence of a family of size 2^Ω(n) of subsets of {1,...,n} each of cardinality n/4 where two subsets have at most n/8 elements in common

Let $\mathcal{G}$ be a family of $t=2^{\Omega(n)}$ subsets of $N=\{1,2,...,n\}$, each of cardinality $n / 4$ so that any two distinct members of $\mathcal{G}$ have at most $n / 8$ elements in common. ...
1 vote
52 views

### Better approximation of the subset in the membership oracle

A standard tool for estimating the size of a subset via membership oracle queries is given below. Lemma 2.8: . Consider two (finite) sets $B ⊆ U$, where $n = |U|$. Let $ε ∈ (0, 1)$ and $γ ∈ (0, 1/2)$ ...
105 views

1 vote
743 views

1 vote
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### What's the relation between the dominating set and vertex cover?

I wonder if the minimal dominating set is always a subset of the minimal vertex cover in any graph. If so, what's the proof?
143 views

### What's complexity of this set problem which looks like "Linear Programming"?

I came up with a problem below, which looks like a linear programming problem: Given $n$ sets $S_{1}, S_{2},..., S_{n}$, with constraints of :  \forall i=1, 2, 3,...,n\space\space \left | S_{i} ...
121 views

### partition to min the max number of intersections

Given $n$ items and $m$ customers, each of whom is interested in some subset of the items, partition the set of items among $k$ different stores so that the maximum number of customers visiting any ...
171 views

### Trying understand a move in Cohen's proof of the independence of the continuum hypothesis

I've read a few different presentations of Cohen's proof. All of them (that I've seen) eventually make a move where a Cartesian product (call it CP) between the (M-form of) $\aleph_2$ and $\aleph_0$ ...
469 views

### The state of art for sunflower system

I am interesting in the sunflower system and its applications in computer science. Given a Universe $U$ and a collection of $k$ sets $A_i$ is called a k-sunflower system if $A_i \cap A_j = Y$ for ...
783 views

### Forcing method used in Baker-Gill-Solovay Relativization paper and Cohen's Proof of Continuum Hypothesis Independence

I am generally interested in the forcing method used by Baker-Gill-Solovay and Cohen. I am looking for as many sources as I can get my hands on concerning either the technique itself or its use. Does ...
1 vote
94 views

### Is there a name for this property in set-valued analysis or combinatorics?

I asked this question a few days ago on MO, but I haven't received an answer. So I thought I would ask here. I have also added a relaxed version of the question here. Let $F$ be a set-valued, finite-...
1k views

### Formal Definition/counter part in mathematics for “Objects” of Object Oriented Models

This is a question I asked in mathematics SE forum, and I was referred here. So here is the question- I'm a newbie in both formal mathematics and theoretical computer science, so please bear with me ...
421 views

### Bloom filter for storage

I am reading about the Bloom filter, and I must say I am fascinated by the idea. I would like to know if it is possible to use it for storage. The problem with the Bloom filter is that, even if we ...
2k views

### Type system based on naive set theory

As I understand, in computer science data types are not based on set theory because of things like Russell's paradox, but as in real world programming languages we can't express such complex data ...
1 vote
811 views

### Proving that inclusion is antisymmetric in Coq

I'm a Coq newbie and I'd like to prove that the inclusion relation is antisymmetric, that is: $\forall x\forall y(x\subseteq y\land y\subseteq x\rightarrow x=y)$. I wrote the following thing: ...
Mathematicians sometimes worry about the Axiom of Choice (AC) and Axiom of Determinancy (AD). Axiom of Choice: Given any collection ${\cal C}$ of nonempty sets, there is a function $f$ that, given a ...