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**7**

votes

**2**answers

564 views

### Can you hide a letter without losing information?

Consider the following game between Alice and Bob.
$\Sigma$ is a finite nonempty alphabet, $\Delta \notin \Sigma$ denotes
a special symbol, and $k > 0$ is a positive integer constant representing
...

**3**

votes

**3**answers

457 views

### Finite variation and idempotent languages and automata.

Let $L$ be a regular language over alphabet $\Sigma$ and let $A:=(Q,\Sigma,\delta, q_0, F)$ be the minimal DFA recognizing $L$. For every $w\in \Sigma^*$ define the variation of $w$ w.r.t. $L$ by
$$\...

**-1**

votes

**1**answer

875 views

### Transition Graph per alphabet? [closed]

How do you determine how many different Transition Graphs are over a particular alphabet? For example How many TG's are over the alphabet {x, y}. I am taking a class with a similar question from ...

**6**

votes

**1**answer

381 views

### Growth zeta-functions of regular languages

Dear All,
my following question may be known and ought to be known, so in case it is folklore please could you give me the references.
To start, it is obvious that growth of rational languages are ...

**2**

votes

**1**answer

328 views

### Given a PDA M such that L(M) is in DCFL construct a DPDA N such that L(N) = L(M)

Is it possible to construct an algorithm which takes as input a pushdown automaton $M$ along with the information that the language accepted by this automaton $L(M)$ is a deterministic context-free ...

**12**

votes

**2**answers

629 views

### Complementation of $\omega$-regular languages in reverse mathematics

Does anyone know where Büchi's theorem that $\omega$-regular languages are closed under complementation fits into the reverse-mathematics classification scheme? That is, is it equivalent over $\...

**5**

votes

**2**answers

660 views

### A special class of regular languages: “circular” languages. Is it known?

We can define a subclass of the regular languages. Fix an alphabet $\Sigma$. Define the "circular" languages (actually, the name already exists to denote a different thing it seems, used in the field ...

**3**

votes

**3**answers

532 views

### 'Closure' of CFLs under complementation and intersection

Consider two context-free languages $L_1, L_2$. Of course, $L_1 - L_2, L_1\cap L_2, \bar{L}_1$, etc. are not necessarily context-free, but they are context-sensitive (the second is easy, the other two ...

**0**

votes

**1**answer

256 views

### A Nomenclature Issue : Imprimitive Semigroup?

The following question was asked by me on the forum sci.math.research,
“An imprimitive group is a transitive permutation group with a non-trivial
equivalence relation compatible with the action of ...

**7**

votes

**3**answers

1k views

### Wolfram's 2-state 3-symbol Turing machine

A few years ago it was announced that a 2-state symbol Turing machine was proven to be universal. However, Vaughn Pratt disputed the proof, and I gather he still disputes it. Wolfram's prize committee ...

**5**

votes

**0**answers

190 views

### “Question-answer” bisimulation

I often come across relations that would be defined as a bisimulation, except that the label match can be "inexact", that is, in the bisimulation game, a move labelled with "a" can be replied to with "...

**1**

vote

**1**answer

200 views

### Dumb question about Minimization in IATLC

I have probably a pretty dumb question about the classical Minimization algorithm for a DFA, as described in the Hopcroft book "Introduction to Automata Theory, Languages and Computation", pg. 155-164....

**3**

votes

**5**answers

1k views

### Theory mainly concerned with $\lambda$-calculus?

Automata theory is mainly concerned with Turing machines and all its relatives-in-spirit. $\lambda$-calculus is rather rarely mentioned in textbooks on automata theory.
What's the common name of the ...

**21**

votes

**1**answer

761 views

### Automatic groups - recent progress

Epstein's (et al.) "Word Processing in Groups" is a quite comprehensive monograph on automatic groups, finite automata in geometric group theory, specific examples like braid groups, fundamental ...

**7**

votes

**6**answers

2k views

### Regular languages and the pumping lemma

In certain dark corners of computer science and group theory, one often wants to prove that a language is not a regular language (ie a language accepted by a finite state automaton).
The only ...