Questions tagged [kolmogorov-complexity]

The Kolmogorov complexity of a string s is equal to the length of the shortest program computing s and halting. Measures the lack of structure in a string.

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Efficiently computable variants of Kolmogorov complexity

Kolmogorov prefix complexity (i.e. $K(x)$ is the size of minimal self-delimiting program that outputs $x$) has several nice features: It corresponds to an intuition of giving strings with patters or ...
28
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2answers
1k views

Can we not output the Kolmogorov complexity?

Let us fix a prefix-free encoding of Turing-machines and a universal Turing-machine $U$ that on input $(T,x)$ (encoded as the prefix-free code of $T$ followed by $x$) outputs whatever $T$ outputs on ...
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2answers
820 views

Circuit lower bounds and kolmogorov complexity

Consider the following reasoning: Let $K(x)$ denote the Kolmogorov complexity of the string $x$. Chaitin's incompleteness theorem says that for any consistent and sufficiently strong formal ...
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3answers
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Using Kolmogorov complexity as input “size”

Say we have a computational problem, e.g. 3-SAT, that has a set of problem instances (possible inputs) $S$. Normally in the analysis of algorithms or computational complexity theory, we have some ...
17
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1answer
681 views

Does the uncomputability of Kolmogorov complexity follow from Lawvere's Fixed Point Theorem?

Many theorems and "paradoxes" - Cantor's diagonalization, undecidability of hatling, undeciability of Kolmogorov complexity, Gödel Incompleteness, Chaitin Incompleteness, Russell's paradox, etc. -...
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3answers
764 views

Do there exist x such that K(xx)<K(x), where K is Kolmogorov complextity.

Let $K(x)$ denote the Kolmogorov complexity of a string $x$. Do there exist a string such that $K(xx)<K(x)$. (Here $xx$ is the concatenation of $x$ with itself). A similar but different question ...
14
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1answer
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Comparing the Kolmogorov complexity of theories

Chaitin's incompleteness theorem says no sufficiently strong theory of arithmetic can prove $K(s) > L$ where $K(s)$ is the Kolmogorov complexity of string $s$ and $L$ is a sufficiently large ...
12
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2answers
353 views

Channel coding results using Kolmogorov complexity

Usually Shannon entropy is used to prove channel coding results. Even for source-channel separation results shannon entropy is used. Given the equivalence between Shannon (global) vs Kolmogorov (local)...
12
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2answers
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Kolmogorov complexity with weak description languages

We can think of Kolmogorov complexity of a string $x$ as the length of the shortest program $P$ and input $y$ such that $x = P(y)$. Usually these programs are drawn from some Turing-complete set (like ...
11
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1answer
595 views

Using Kolmogorov complexity to establish proof complexity lower bounds?

The motivation for this question is the fact that most n-bit strings are incompressible. Intuitively, we can propose by analogy that most proofs for Tautologies are incompressible to polynomial size. ...
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3answers
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Is there a theory to answer “the simplest program to solve a problem”?

To answer "what problems can be solved by computing", we developed the theory of computability. For the problems that are computable, is there a theory to answer the question "is the program I get the ...
10
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1answer
231 views

Worlds Relative to Which “Invulnerable Generators” Do Not Exist

Invulnerable generators are defined as follows: Let $R$ be an NP relation, and $M$ be a machine which accepts $L(R)$. Informally, a program is an invulnerable generator if, on input $1^n$, it ...
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Proof for Kolmogorov complexity is uncomputable using reductions

I am looking for a proof that Kolmogorov complexity is uncomputable using a reduction from another uncomputable problem. The common proof is a formalization of Berry's paradox rather than a reduction, ...
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2answers
596 views

Expected values of Kolmogorov complexity in a random sample

Kolmogorov complexity of a string is not computable. However, in a random subset of size $M$ of binary strings of length $n$, how many are expected to have complexity less than some integer $n_{0}$ ...
9
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1answer
338 views

Is Kolmogorov complexity a surjective function?

Let us fix an encoding of Turing-machines and a universal Turing-machine, U, that on input (T,x) outputs whatever T outputs on input x (possibly both running forever). Define the Kolmogorov complexity ...
8
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1answer
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Is Kolmogorov complexity quasi-surjective?

For Kolmogorov complexities $\hspace{.02 in}K$ induced by essentially-optimal description languages, does there exist an integer $c$ such that for all positive integers $n$, there exists a string $x$...
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3answers
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Kolmogorov Complexity applications in Number Theory

What are the applications of Kolmogorov Complexity in Number Theory and on proofs related fields? (The monograph by Li & Vitanyi doesn't have many applications related to Number Theory.) One of ...
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1answer
275 views

Conditional Kolmogorov Complexity: $K(y|x^*)$ vs $K(y|x)$

In "The Similarity Metric" Li, et al give the first definition of the normalized information distance as $\displaystyle d(x,y) = \frac{\max \left \{ K(x|y^*), K(y|x^*) \right \}}{\max \left \{ K(x), ...
7
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1answer
358 views

Difference between time-bounded and memory-bounded Kolmogorov complexity

Let $x$ be a finite string of length $n$. Denote by $C^t(x)$ the Kolmogorov complexity of $x$ bounded by time $t$ (i.e. the length of a minimal program that outputs $x$ and running at most $t$ steps)....
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Number of circuits computing a given function

Let's say we have some function that can be computed by a minimal circuit of size $m$ (using some metric, say, the number of gates). Other than this minimal circuit, there will be many other circuits ...
6
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1answer
330 views

Average-case analysis of algorithms using the incompressibility method

I recently became very interested in Kolmogorov complexity and the incompressibility method especially in the context of average-case analysis. The "standard" book by Li & Vitanyi showcases many ...
6
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1answer
282 views

Is a binary sequence computable iff the Kolmogorov complexity of its initial segments is bounded?

Disclaimer: I am mostly unfamiliar with theoretical computer science, making it hard for me to navigate literature in the field. I ask the following out of curiosity. Background/Motivation: Coming ...
6
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1answer
258 views

Expected Kolmogorov complexity under Kolmogorov complexity distribution

If $K(w)$ is the Kolmogorov complexity of a string $w$, where programs are prefix-encoded so $\sum_{w} 2^{-K(w)} \leq 1$, what is $$\lim_{n\to\infty} \frac{\sum_{|w|=n}2^{-K(w)} K(w)}{\sum_{|w|=n} 2^{...
6
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1answer
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Where does the “intuitive” understanding of Kolmogorov complexity fails

Often, the Kolmogorov complexity of some string $x$ is defined as the length of the shortest program producing $x$, for example on wikipedia. So to give this more formal meaning, define $$ K'(x) := ...
6
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1answer
352 views

Do we know a specific $L_{ZFC}$ such that $K(s) \ge L_{ZFC}$ is unprovable in ZFC for all strings $s$?

Chaitin's incompleteness theorem states for any formal system $F$ (which satisfies various criteria), there is a $L$ such that for any $s$ the statement $$K(s) \ge L_F$$ is unprovable in that formal ...
6
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1answer
267 views

Kolmogorov Complexity of an arbitrary string

For an arbitrary string sampled from $\{0,1\}^n$, what would be the probability that the string has a Kolmogorov Complexity $\geq$ length of the string, $n$. In other words, how many strings are ...
6
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1answer
236 views

Algorithmic mutual information between random string and minimal Kolmogorov sufficient statistic

Regarding notation in the following, the function $\ell(B)$ returns the length of bitstring $B$, and the cardinality of set $S$ is denoted by $|S|$. A bitstring $B$ is generated by drawing 0s and 1s ...
6
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1answer
339 views

Time-bounded Kolmogorov complexity and non-random strings

If $t$ is a time constructible function then we can define the time-bounded Kolmogorov complexity of a string $x$ as: $C^t(x)$ = the size of the smallest program p that generates $x$ in $t(|x|)$ ...
6
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1answer
607 views

Definition of a monotone machine.

There is a definition of a 'monotone machine' in Li & Vitany's Book, and another one which is for example stated in this paper via c.e. (computably enumerable) sets. I can't see why these ...
6
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1answer
147 views

Lower Bound on the difference between uniform and prefix-free complexity

The uniform Kolmogorov complexity (also known as decision complexity) of a string $\sigma$ is defined as follows: let $\phi: 2^{<\omega} \times \mathbb{N} \rightarrow {0,1}$ be a partial computable ...
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4answers
548 views

Are there incompressible strings $S$ such that $K(SS) \lt K(S)$?

This question was inspired by Sune Jakobsen's question and Tsuyoshi's answer. In Kolmogorov-complexity, a string is incompressible if $K(S) \ge |S|$. Is there incompressible string $S$ such that $K(...
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0answers
153 views

What is the Kolmogorov complexity of arithmetic?

Chaitin's incompleteness theorem says no sufficiently strong theory of arithmetic can prove $K(n) > L$ where $K(n)$ is the Kolmogorov complexity of the number $n$ and $L$ is a sufficiently large ...
6
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0answers
141 views

Comparing the Kolmogorov complexity of theories - Part 2

Chaitin's incompleteness theorem says no sufficiently strong theory of arithmetic can prove $K(x) > L$ where $K(x)$ is the Kolmogorov complexity of natural number $x$ and $L$ is a sufficiently ...
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0answers
34 views

Different definitions of optimal decompressors

Let $B^{<\omega}$ be the set of finite binary strings. I will only consider functions from $B^{<\omega}$ to $B^{<\omega}$. I recall the definition of the algorithmic complexity of a string ...
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Complexity of Roman numeral evaluation

I came up with a result the other day that arbitrary length Roman numeral evaluation can be modeled as a monoid: https://gist.github.com/4542999 1) Is this a known result? 2) If not, any ...
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3answers
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How to measure programming language succinctness?

I want to explore the notion of quantifying the amount of succinctness a programming language provides. That is, the amount a high-level language reduces the complex. This idea of "simplification" ...
5
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2answers
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Definition of a prefix-free Turing machine

A prefix-free function is one whose domain is prefix-free. Similarly, a prefix-free (Turing) machine is one whose domain is prefix-free. It is usual to consider such a machine as being self-...
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Resource-bounded variant of Kolmogorov complexity

Consider the variant of Kolmogorov complexity, where the program is only allowed to use a bounded amount of resources. This more closely resembles the practical situation, where decompression needs ...
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0answers
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Computational depth and p-time hard instances

After reading the nice results of the paper: "Worst-Case Running Times for Average-Case Algorithms" by Antunes and Fortnow, I was wondering about the existence of further results linking basic ...
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Worst-Case and Average-Case running-time equal with universal p-distribution with kolmogorov-complexity any applications of this theory?

at the moment I'm reading "Gems of Theoretical Computer Science" from Schöning and Pruim. In Chapter 8 the book defines a "universal probability distribution" in a way that the Average-Case running-...
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Why primitive rotation is $53.13^\circ$ in the quantum Turing machine used by Vitanyi for Quantum Kolmogrov Complexity?

Right now I am going through Quantum Kolmogorov Complexity Based on Classical Descriptions by Vitanyi. In the introduction, the author assumed the primitive rotation $\theta = 53.13^\circ$ to have ...
4
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1answer
215 views

Is “normalized distance” (as per Li & Vitanyi, Kolmogorov Complexity) a reasonable thing?

In "The Similarity Metric" (Li, Vitanyi, et. al) they define a normalized distance (or similarity distance) as a function $\Omega \times \Omega \to [0,1]$ which is both symmetric and satisfies the ...
3
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1answer
317 views

More complex integers

In connection to this question: Expected values of Kolmogorov complexity in a random sample Let $n$ be number of bits. Let $A = \{0,1,2,\dots,2^{n}-1\}$ be indexed by the $n$-bits. Let $ \delta > ...
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1answer
248 views

Kolmogorov complexity of D and D+d

I'm looking into using of the shelf compression algorithm to approximate the Kolmogorov complexity of a document corpus D and the complexity of D+d, where d is an extra document. I've got a strange ...
3
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1answer
186 views

Is joint Kolmogorov Complexity order invariant?

Due to the symmetry of information, it follows up to an additive constant that K(X,Y) = K(Y,X) Does this hold for more than two data objects as well?
3
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1answer
219 views

Compression algorithms for low-complexity strings?

Let $s$ denote a string over a finite alphabet, $n_s = |s|$ be the length of $s$, and $n_s^{*}$ denote the minimum description size of $s$ under a given computational model (TM, CFG, etc.). Are there ...
3
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1answer
87 views

Commonality of minimal Kolmogorov structure functions

A typical $B$ is difficult to define precisely. Intuitively, it is the sort of bitstring that will be generated most of the time by randomly drawing 0s and 1s. However, the concept can be clarified ...
3
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1answer
104 views

Relation between different “complexity theories” and complex systems theory

I know of at least 4 fundamentally different uses of the term "complexity theory": the study of how hard a problem is to solve using some sort of computing machine (I am ignoring divisions within ...
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0answers
253 views

A sequence wherein the Kolmogorov complexity of the terms does not increase

I am looking for an algorithm $A$ - which for any non-null input string $s_1$ produces a sequence $s_1, s_2...$ such that : It can be proved in some axiomtic system $S$ that: $\...
3
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0answers
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What is the shortest description of a universal computational structure that includes a meta-circular evaluator?

I am wondering whether there is a minimal (or the shortest known) way of specifying a universal computational structure that includes a specification of a meta-circular evaluator within that structure....