Questions tagged [cc.complexity-theory]

P versus NP and other resource-bounded computation.

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What is the simplest one-way function (in terms of boolean circuit complexity)?

What is the simplest known one-way function? By simplest, I mean, when implemented as boolean logic, the number of AND/OR/NOT gates needed is minimal (smallest circuit complexity). (I'm trying to find ...
6 votes
1 answer
148 views

Is it $NP$-hard to check whether a given algebraic circuit computes permanent?

Given are a natural number $n\in\mathbb{N}$ and a polynomial $P$ in the form of an arithmetic circuit $C$ over $\mathbb{Z}$ (a circuit which only uses $+$ and $\times$ gates and integer constants as ...
5 votes
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Complexity of the unique homomorphism problem up to automorphisms

I am interested in the following problem: given two relational structures $\mathbf{A},\mathbf{B}$, is there a unique homomorphism from $\mathbf{A}$ to $\mathbf{B}$ up to automorphisms of $\mathbf{B}$, ...
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Complexity of feasibility of a system of linear and restricted non-linear inequalities

I have a system of constraints on $\mathbb{N}^n$ of the form $Ax \le b \land x_1 \le x_2x_3 \land x_1 \le x_4x_5$ where $A,b$ are a matrix and a vector with integer coefficients. If there was a single ...
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Claimed proof of PSPACE ⊆ BQP on arXiv

A new paper appeared on arxiv: PSPACE ⊆ BQP by Shibdas Roy: https://arxiv.org/abs/2301.10557 From the abstract: The complexity class PSPACE includes all computational problems that can be solved by a ...
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$\mathsf{NL}$ vs. $\mathsf{AC}^1$

It is known that $\mathsf{NL} \subseteq \mathsf{AC}^1$ (because $\mathsf{NL}$-complete problem PATH belongs to $\mathsf{AC}^1$). Are there problems in $\mathsf{AC}^1$ that are unknown to be in $\...
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Relation between $NC^i$ and $L^i$

Is it true $NC^i\subseteq L^i\subseteq NC^{i+1}$ at every $i>0$?
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2 votes
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hardness of partition of permutation into a minimum number of monotone subsequences

Given a permutation P, a monotone subsequence is a subsequence (i.e. the elements do not have to be consecutive in P) that increases or decreases. This leads naturally to the following optimization ...
2 votes
1 answer
391 views

Are regular expressions inherently more difficult to construct than DFAs for humans?

When I am asked to construct a regular expression and DFA that would accept a language $L$, I usually find it much easier to construct the DFA (almost coming mechanically for me) than it is to ...
3 votes
2 answers
87 views

Encoding of finite automata in Intersection Non-Emptiness problem

The intersection non-emptiness problem is defined as follows: Given a list of deterministic finite automata as input, the goal is to determine whether or not their associated regular languages have a ...
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Is modular square roots in NC?

Assume factorization of modulus is known. Is modular square roots then in $NC$? How about the case of prime modulus?
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Require Hamming weight in CNF

I have a SAT problem in conjunctive normal form that I’d like to solve, but I need to add one more condition: for the existing variables $x_1,\ldots,x_n$ the Hamming weight is $k$. (It would be ok to ...
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Restrictions on set of infinitely many n's for which an algorithm breaks distributional hardness

Say we want to capture the notion that an efficiently samplable distribution $D(1^n)$ is hard with respect to some boolean function $f$ for a decision problem or some efficient relation $R$ for a ...
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Is complexity class containment preserved relative to any oracle?

That is, suppose $A\subseteq B$ for two complexity classes $A$ and $B$. Is it the case that for any oracle $C$, and any definitions $A^*$ and $B^*$ of $A$ and $B$, we have ${A^*}^C\subseteq {B^*}^C$? (...
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How to prove that a given class of convex programs cannot be solved by linear programming?

Given the following program, where $f, g$ are convex functions: $$ \text{minimize}~~ f(x) \\ \text{subject to}~~ g(x)\leq 0 $$ the problem can be solved by convex programming algorithms, but it would ...
2 votes
1 answer
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Counting argument for LTF circuits

In Boolean circuit complexity, Shanon's counting argument shows that a random Boolean function on $n$-input bits requires a circuit of size $\Omega(2^n/n)$ to be computed by a circuit made of AND, OR ...
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Does Bellantoni-Cook safe recursion (or any other implicit characterization of P) admit Kleene's second recursion theorem?

Abstractly, by a programming language that operates on binary strings I mean a set $P$ of programs along with a semantics relation $[p](x) = y$, ``the program $p$ on string $x$ halts with output $y$.&...
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Savitch's theorem for time complexity

Is it known that an analog of Savitch's theorem for time complexity is impossible, or is this an open question? More formally, is $\exists d\ \forall c : \mathsf{NTIME}(n^c) \subseteq \mathsf{DTIME}(n^...
7 votes
1 answer
231 views

Is $PSPACE$ believed to be different than $PP$?

From Googling, I couldn't find any discussion about whether $PP=PSPACE$ is more or less likely than $PP\subsetneq PSPACE$. Is it currently believed that $PP\neq PSPACE$? What would be the ...
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6 votes
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Concrete family of propositional formulas

Let $k,n \in \mathbb{N}$, where $k$ can be thought of as being fixed constant. For each $1 \leq \ell \leq k$ and $1 \leq i \leq n$ we have a proposition symbol $p_{(\ell,i)}$ (so in total we have $nk$-...
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Non-uniformity assumptions in circuit complexity

I recently came accross the following standard inclusion of complexity classes: $$\textbf{NC}^0 \subseteq \textbf{AC}^0 \subseteq \textbf{NC}^1 \subseteq \textbf{L} \subseteq \textbf{NL} \subseteq \...
7 votes
1 answer
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How do separations in of query complexities imply complexity class separations relative to oracles?

Simon's problem is the following: Given oracle access to a Boolean function $f: \{0,1\}^n\rightarrow \{0,1\}^n$, and promised that precisely one of the following two cases is true, decide which of ...
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Non-uniform consequences of uniform derandomization

Adleman showed that $\mathsf{BPP/poly} \subseteq \mathsf{P/poly}$. Does $\mathsf{P} = \mathsf{BPP}$ have any implications for $\mathsf{BPP}/a(n) \subseteq \mathsf{P}/a(n)$ $\mathsf{BPTIME}(t(n))/a(n) ...
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One way analogues of Logspace

When we say a function is one-way we typically mean a function is encodable in $P$ but its decryption is not in $P$ but in $UP$. Likewise we say a function is logspace one-way if the function is ...
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2 votes
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Problems in $P^{PP}$

I just discovered that a problem that I was studying could belong to $P^{PP}$, I would like to prove that this problem is $P^{PP}$-complete (if that is even a thing). The issue is that I'm unable to ...
11 votes
1 answer
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Is the 3-coloring problem NP-hard on graphs of maximal degree 3?

Consider the 3-coloring problem: given an undirected graph $G = (V, E)$, decide if there is a 3-coloring of $G$, i.e., a function $f$ from $G$ to $\{1, 2, 3\}$ such that there is no edge $\{u, v\}$ in ...
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2 votes
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Computing real numbers with Turing Machines

Consider the following decision problem: Given a two integers $n$ and $k$, decide whether $k=\lfloor n\pi\rfloor$ Question: Is this problem known to be in $P$? Although this may look like a stupid ...
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On the Reductions of Functional complexity Classes

In Chapter 10 of Computational Complexity by Christos Papadimitriou, it is noted that reduction between problems of functional complexity classes are defined as follows: Function problem A reduces to ...
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Complexity of a problem related to Friedman's TREE(k) function?

Background Given two rooted, vertex-colored trees $T_1, T_2$, $T_1$ is color-preserving inf-embeddle in $T_2$, which we'll denote $T_1 \leq T_2$, if there is an injective $f \colon V(T_1) \to V(T_2)$ ...
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Random Self-Reducibility of the Discrete Logarithm

Section 10.1.2 of Sanjeev Arora and Boaz Barak's Computational Complexity: A Modern Approach defines random self-reducibility and proves hardness of the discrete logarithm by reducing a worst case ...
5 votes
2 answers
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Complexity of convertibility in simply typed λ-calculus with sums

For the simply typed λ-calculus with only the function type →, the complexity of deciding βη-equivalence is well-understood: it's TOWER-complete (as mentioned here). I expect the same should be true ...
1 vote
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On the borderline between natural and artificial problems

While there is no formal definition of what constitutes a natural algorithmic problem, in most cases there is pretty good consensus whether a specific problem is natural or artificial. Natural usually ...
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PAC learning over continuous functions

I'm wondering if it's possible to use PAC learning to learn a continuous function. For example, if we wanted to learn a probability distribution or a CDF, is it valid to train on some set of m ...
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Universality problem over unary alphabet is NP-complete

The universality problem over a unary alphabet: Decide if a unary NFA rejects a string. I believe that this is NP complete, but I am unsure of how to prove it. One possible idea I have is to split it ...
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How does laziness help functional data structure?

Functional data structures, or immutable data structures, are often achieved by copying old data to new data upon operation. Naively, it looks much less efficient than their imperical counterpart. ...
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Statements equivalent to strongly polynomial time linear programming

Say a problem is SPT iff it admits an SPT algorithm. What statements of interest are known to be equivalent to "LP is SPT"? Examples: "linear feasibility solving is SPT" (due to ...
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3 votes
3 answers
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Intersection non-emptiness problem over regular expressions and NFA

The intersection non-emptiness problem is defined as follows: Given a list of deterministic finite automata as input, the goal is to determine whether or not their associated regular languages have a ...
2 votes
1 answer
55 views

Complexity of reachability in fractal mazes with traps

Is reachability in fractal mazes with traps EXPTIME complete? A fractal maze includes one or more copies of itself. For example, see the question Decidability of Fractal Maze or Puzzling ...
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Uniformly redistributing items across bins. What problem is this?

I'm trying to find reading material on a particular problem I'm interested in, but I don't know the terms to search. Problem assumptions/definitions: We have finite number of items I with weights [0, ...
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MIP with bounded communication between provers

Are there any known results on the complexity class that is MIP except with independence of provers loosened to allow "limited classical communication" between provers: where total message ...
2 votes
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Question about #P-completeness and NP-completeness

In the book Nature of Computation by Moore & Mertens there is an exercise saying "show that if a counting problem #A is #P-complete with respect to parsimonious reductions, that is if every ...
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Coloring the $k$-deletion graph “constructively”

For $n,k\ge 1$, we define the graph $D_{n,k}$ to have vertex set $\{0,1\}^n$, with distinct $x,y$ being adjacent if $LCS(x,y)\ge n-k$. My question is: fixing $k>1$, does there exist some $C=C_k$ ...
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3SAT instances where no assignment fails to satisfy more than one clause: do they eixst, and what complexity class do they belong in?

Title says it all. I am curious of the 3SAT problem but limited to instances where only one clause is left unsatisfied by any literal assignment. Do such problems exist, and if they do, what is it ...
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Complexity of Computing Shannon Entropy

It is my understanding that the necessity of numerical precision can be an obstacle when trying to show a decision problem's membership in a particular complexity class. For example, I believe it is ...
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Parallel complexity of fixed dimension fixed constraints integer programming

Papadimitriou in https://lara.epfl.ch/w/_media/papadimitriou81complexityintegerprogramming.pdf shows ILP is fixed parameter tractable in number of constraints and Lenstra in https://people.csail.mit....
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-1 votes
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Does the set $P$ contain only decision problems or also optimization problems? [closed]

Looking at many posts on Stack Overflow, it seems the set $P$ has only decision problems. See for instance the accepted answer here. But, this seems to be in contradiction to the book Introduction to ...
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Boolean vs algebraic circuits difference

Valiant, Skyum, Berkowitz and Rackoff in https://epubs.siam.org/doi/10.1137/0212043 showed that $VP=VNC^2$, namely, that arithmetic circuits can be parallelized. What is the central reason such a ...
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6 votes
1 answer
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Unclear proof step in Feder and Greene's 1988 paper showing NP-Hardness of approximating k-center problem within a factor of 1.82

I was reading the paper "Optimal Algorithms for Approximate Clustering", Feder and Greene [1988] (https://dl.acm.org/doi/10.1145/62212.62255). Specifically, I was trying to look at the $1.82$...
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On the proof of $PP = P \iff \#P = FP$ in Arora & Barak (Lemma 17.7)

Introduction I am currently studying chapter 17 (of the famous textbook by Arora & Barak [1]) on the complexity of counting and got stuck on the proof of Lemma 17.7, which states $\mathrm{PP} = \...
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Polynomial GCD exact complexity in terms of degree and number of variables

https://en.wikipedia.org/wiki/Polynomial_greatest_common_divisor#Proof_that_GCD_exists_for_multivariate_polynomials states multivariate polynomial GCDs may be defined over $\mathbb F_p[x_1,x_2,\dots,...
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