# Questions tagged [lo.logic]

Computational and mathematical logic.

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### The logic expressible in the Z notation: is it first-order logic?

Is the logic expressible in the Z notation (a) higher-order logic? (b) simple type theory, (c) a stylized version of first-order logic? If I'm going to use the Z notation (or some variation on it) in ...
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### Proof of $DLOGTIME-CC^0 = MOD[<,bit]$

Let $CC^0[m]$ be the class of constant-depth, polynomial-sized circuits consisting entirely of $MOD_m$ gates, which put out $1$ iff the sum of their inputs $\equiv 0~(\textrm{mod}~m)$. In the same way ...
99 views

### $\mathit{FO}[+,\times]$ seems more powerful than $\mathit{DLOGTIME}$-uniform $\mathit{AC}^0$?

I’ve been reading up on the connection between first order logic and small circuit complexity classes, and specifically Barrington, Immerman, and Straubing’s paper “On Uniformity Within $\mathit{NC}^1$...
100 views

### Functional abbreviation for Inst expression in Turing's 1936 paper

In Turing's 1936 paper "On Computable Numbers", For a Turing Machine $M$, $Inst(q_i S_j S_k L q_l )$ means that if $M$ scans symbol $S_j$ under $m-configuration$ $q_i$, then the symbol ...
48 views

### Is every countable, finite-branching LTS bisimilar to a tree?

Let $L$ be a finite set of labels, and let $\mathcal{C}$ be the set of finitely-branching transition systems labeled by $L$ and with a countable set of states. Let $\sim$ denote the bisimulation ...
138 views

### Is modal $\mu$-calculus “equivalent” to bisimulation?

I know that propositional modal $\mu$-calculus $L\mu$ is bisimulation-invariant. However, I'm curious to what degree it captures bisimulation. Q1: Given two labeled transition systems $T_1$, $T_2$ ...
154 views

### Alternative exponential definition of Kolmogorov complexity

In Kikuchi's paper Kolmogorov complexity and the second incompleteness theorem the Kolmogorov Complexity (KC) of $x$ is defined as $$K(x) = \mu e (\varphi_e(0) \simeq x) \, ,$$ the smallest $e$ such ...
82 views

### λProlog vs HiLog

λProlog is a well-known higher-order logic programming language. On the other hand, HiLog is described as a logic programming language with higher-order syntax, but first-order model theory. Do I ...
249 views

### Uncountability in intuitionistic logic

I've read snippets here and there that inside intuitionistic logic, uncountable can be a subset of the naturals ? What is the correct intuition to think about this? Andrej Bauer replied above, saying ...
141 views

### Order-invariant conjunctive queries are FO-definable without the order

I'm looking for a reference for Exercise 6.11 from Libkin's FMT book: Prove that an order-invariant conjunctive query is FO-definable without the order relation. All help is appreciated.
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### Is Scott's reduction sound for $\mathrm{FO}^2$ with equality?

As per this paper by Grädel, Kolaitis and Moshe Vardi, they discuss computational complexity of satisfiability problem in $\mathrm{FO^2}$, In order to do this they use Scott's reduction. Which is the ...
111 views

### Does focused proof search ever have to backtrack across the choice of focus formula?

There are a lot of different "focused" sequent calculi for lots of different logics, but my understanding is that many or most of them have the following flavor. First one divides the ...
122 views

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### When a type is a value?

In functional programming and in the theoretical setting of the $\lambda$-calculus it is standard to consider a lambda abstraction $\lambda x.M$ as a value. In my understanding, the intuitive reason ...
248 views

### Busy Beaver Equivalent for the Untyped Lambda Calculus

In the same way that the Busy Beaver function is defined for Turing Machines, we could define a similar function for the untyped lambda calculus: Over all terms in the ULC composed of ...
366 views

### Hereditary substitution with a universe hierarchy

I've read about hereditary substitution for the Simple Lambda Calculus and for The Logical Framework with distinct terms and types. I'm wondering, are there any examples of hereditary substitution in ...
116 views

### Results in denotational semantics from model theory?

Denotational semantics interpret the theories of various lambda calculi in various (set-theoretic, domain-theoretic, category-theoretic, game...) models. Let $T$ be the theory of one such lambda ...
250 views

### Understanding the Proof of Strong Normalization of the Calculus of Constructions

I have difficulties in understanding the proof of strong normalization for the calculus of constructions. I try to follow the proof in the paper of Herman Geuvers "A short and flexible proof of Strong ...
79 views

### Soft Truth Values in the PSL model

This might sound like a trivial question. But since am starting out with my research in an area that is entirely new to me, I would really appreciate it if someone could kindly elucidate what Soft ...
146 views

### Do Banach spaces and linear contraction maps form a model of ILL with an exponential?

Recently, I read on the nLab that the category of Banach spaces and linear contractions is small complete, small cocomplete, and monoidal closed. This means that Banach spaces and short linear maps ...
206 views

### What does the category of RDF models look like in Institution Theory?

The Question in short Here is the question in its pure form. Details of my reasoning can be found below. The RDF1.1 spec semantics defines a model to consist of a set IR of objects and IP of ...
I do not understand why one would ever need a transfinite loop variant. Why do natural-number-valued variants not suffice? My simple (but perhaps too naive) argument is: if a loop $L$ terminates ...
I am new to lambda calculus and definability theory, and I am trying to clarify my understanding of the relationship among the following concepts: An element $a$ in the domain of a type $A_\sigma$ is ...