Questions tagged [cc.complexity-theory]

P versus NP and other resource-bounded computation.

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2 votes
0 answers
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Nondeterministic polynomial time languages with linearly bounded certificates

Define the class $X$ of languages by the condition that a language $L$ over alphabet $\Sigma$ is in $X$ iff there are a constant $c > 0$ and a polynomial-time checking relation $R$ such that for ...
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5 votes
0 answers
82 views

Complexity of approximating boolean functions with circuits

Let $f$ be a boolean function on $n$ variables - say we want to find the smallest circuit $C$ where $C(x)=f(x)$ for all but an $\epsilon$ fraction of inputs $x \in \{0,1\}^n$. What is known about the ...
0 votes
1 answer
70 views

Parameterized complexity of Hitting Set with slightly bigger parameter

The Hitting Set problem, when parameterized by the size $k$ of the hitting set, is W[2]-hard. Is it also W[2]-hard when parameterized by $k$ plus the number of subsets in the instance? I explain in a ...
0 votes
0 answers
78 views

Does NP-completeness in one graph class imply not NP-intermediate in another graph class?

I am trying to wrap my head around implications of CSP dichotomy theroem. CSP is short for Constraint Satisfaction Problem. The following seem to be known results (I shall focus on decision problems ...
2 votes
0 answers
65 views

Is k-ACYCLIC COLOURABLITY in CSP?

All graphs in this question are finite, simple and undirected. Let $k$ be a fixed positive integer. A $k$-colouring of a graph $G$ is a function $f\colon V(G)\to\{1,2,\dots,k\}$ such that $f(u)\neq f(...
2 votes
0 answers
59 views

Does advice reduce depth?

Specifically I'm thinking about NC$^1$/poly and NC$^1$/rpoly (randomized advice). Are there any statements like "If $\{C_n\}$ is a family of NC$^1$/(r)poly circuits with depth $C\log n$, then ...
0 votes
0 answers
47 views

Is Power Dominating Set in W[2]?

I'm interested in the Power Dominating Set problem: given a graph, find a power dominating set $D$ of size at most $k$. A power dominating set is a set of vertices such that it "observes" ...
3 votes
1 answer
90 views

$\mathrm{AC}^0$ upper bound for Hamming weight

Consider Theorem 11 of this paper (S. Aaronson, BQP and the Polynomial Hierarchy), which says: Any depth $d$ circuit that accepts all $n$ bit strings of Hamming weight $\frac{n}{2} + 1$ and rejects ...
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8 votes
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170 views

"Addition function" that works for both perm and det simultaneously?

For $f = (f_n)$ a family of polynomials where $f_n$ is a polynomial in $n^2$ variables (which we can think of as the entries of an $n \times n$ matrix), say a function $S(A,B)$ is an addition function ...
2 votes
0 answers
139 views

Which hypergraphs can be simplified by alternatively removing a hyperedge and an isolated vertex?

Let $H = (V, E)$ be a hypergraph, with $V$ the set of vertices and $E \subseteq 2^V$ the set of hyperedges. An elimination sequence on $H$ consists of alternatively removing hyperedges. Specifically, ...
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4 votes
1 answer
156 views

Treewidth relations between Boolean formulas and Tseitin encodings

Suppose you have a propositional formula $\varphi$ in CNF. You want to efficiently obtain an equisatisfiable CNF formula encoding $\neg \varphi$. You use the usual Tseitin encoding with auxiliary ...
3 votes
0 answers
235 views

Is the following equitable factoring problem $NP$-hard or in $P$?

Consider the following factoring problem: Given an integer $r$ and another integer $N$ along with all of its $n$ number of prime factors and their corresponding multiplicities $\{p_i,e_i\}_{i=1}^n$, ...
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6 votes
1 answer
158 views

Reductions weaker than polynomial-time for $\exists \mathbb{R}$

I am currently studying the complexity class $\exists \mathbb{R}$ which contains all problems that are reducible in polynomial time to the existential theory of the reals. In the literature ...
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2 votes
1 answer
118 views

Complexity of finding approximate solutions for systems of polynomial equations

Consider the following problem: Input: $(p_1,...,p_n, \epsilon)$ where each $p_i$ is a polynomial in $m$ variables with integer coefficients and $\epsilon>0$. Output: If there is $(r_1,...,r_m) \in ...
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1 vote
1 answer
148 views

Nontrivial Algorithms for Coloring (Parameterized by Pathwidth)

Let $k$ be a positive integer. In the $k$-coloring problem, we are given a graph $G$ on $n$ nodes, and want to determine if there is a way to assign a color to each vertex of $G$ such that no two ...
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2 votes
0 answers
78 views

Relationship b/w $QMA$ and $QCMA$

I was trying to read and understand about the complexity classes $QMA$ and $QCMA$: $QMA$ is defined as the class with the set of problem such that, given a quantum certificate for any problem, its ...
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1 vote
1 answer
92 views

Bounded non-emptiness intersection of deterministic context-free grammars

Let A and B be two determinstic context-free grammar, and let N be an integer: What's the complexity of deciding if the intersection of the languages accepted by A and B over all strings of length ...
0 votes
0 answers
113 views

How can I switch into computability theory when I am part way through my PhD in deep learning?

I am partway through my PhD studying deep learning. I chose it just because it's useful and would yield a lot of industry opportunities. However, I am really missing my previous coursework in ...
3 votes
0 answers
75 views

Complete problems for fast-growing hierarchy classes

I need examples of natural complete problems in classes $\textbf{F}_\alpha$, definition of $\textbf{F}_\alpha$ can be found here. Also in section 6 there are examples for $\omega$, $\omega^\omega$, $\...
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4 votes
0 answers
97 views

Simulating a $k$ tape Turing machine with a 2 tape Turing machine

Let $k$ be an (fixed, $3$ for instance) integer, what is the fastest simulation of a $k$ tape Turing machine by a two tape Turing machine? That is we're looking for the best 2 tape TM $U$, such that ...
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0 votes
1 answer
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Question about BPP complexity class [closed]

Good morning everyone, I just started studying the BPP complexity class and the amplification lemma. There is one exercise about BPP that I don't understand, I hope that you can help me. Let $L$ be a ...
7 votes
1 answer
170 views

Order notation quirk

Is it true that $$O(n) = \bigcap \{ O(g) \mid g \in \omega(n) \}?$$ This appears to be a straighforward question about sets of functions, but on closer examination leads to some murky waters. I would ...
3 votes
0 answers
179 views

$NP=QMA$'s impact on $BPP$ vs $BQP$ problem

$\mathit{BPP}$ vs $\mathit{NP}$ and $\mathit{BQP}$ vs $\mathit{QMA}$ are two problems that are (in spirit, for classical and quantum computers respectively) similar and both are open. Moreover, we don'...
2 votes
0 answers
172 views

Accessible entry for computational complexity theory through concrete problems

I am planning to start studying computational complexity theory. As the field is technical for a fresh undergrad alumni like me, I thought a good approach is to tackle it through areas I am more ...
-3 votes
1 answer
71 views

Interesting Variation on Subset Sum Problem

Does anyone have any ideas for this algorithms problem? Given an array $A$ with 40 integers ($-10^9 < A_i < 10^9$), how many ways are there to reach a target sum $X$. Normally, I would use ...
4 votes
0 answers
76 views

Reducing counting minimal vertex covers to counting minimum cardinality vertex covers

Consider two problems. Problem 1: Given a graph $G = (V, E)$, find the number of minimum cardinality vertex covers of $G$. Problem 2: Given a graph $G = (V, E)$, find the number of minimal vertex ...
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5 votes
1 answer
106 views

Finding planes from their points

Given some points $P=\{x_1,\dots,x_m\}$ in a vector space $(Z/2Z)^n$, if $P$ is a union of linear subspaces all of the same dimension $1<d<n$, can we efficiently find these subspaces? (Any ...
1 vote
0 answers
171 views

$\#NAE2SAT$ and $\oplus NAE2SAT$ complexity

Deciding $2SAT$ is in $NL$ and $\#2SAT$ is $\#P$ complete while $\oplus2SAT$ is $\oplus P$ complete. Deciding $SAT$-$2$-$NAE$ - every clause has exactly $2$ literals, is there an $NAE$ satisfying ...
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3 votes
1 answer
133 views

XORSAT to HornSAT reduction

I am trying to write a practical piece of code that solves a XORSAT by first reducing it to HornSAT and then solving the HornSAT (instead of doing Gaussian Elimination over F2). The reason for this ...
9 votes
0 answers
377 views

Examples of simulations in proof complexity that are not p-simulations

I am writing a paper on the complexity of some unorthodox proof systems, where I have two systems $P$ and $Q$ such that $P$ simulates $Q$ in the sense of it being possible to translate a $Q$-proof ...
12 votes
0 answers
362 views

Invisible electric fence even if P = NP?

Scott Aaronson has suggested that one argument in favor of $\mathsf{P} \ne \mathsf{NP}$ is that there seems to be an invisible electric fence separating $\mathsf{NP}$-complete problems from problems ...
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1 vote
0 answers
111 views

Is counting the union of power sets NP-complete?

Say we have $n$ sets $A_1,\dots,A_n$ with elements from a universal set $U$. We want to compute the cardinality of $\cup_{i=1}^n 2^{A_i}$ or at least decide on non-trivial bounds. Is this problem NP-...
3 votes
0 answers
49 views

Hardness of computing entropy of a function on uniform input distribution

Let $p \geq q \in \mathbb{N}_+$, and let $L_\mathsf{max-entropy} := \{(f,k) \in \{0,1\}^{\lambda^p} \times \{0,1\}^{\log\lambda} | \lambda \in \mathbb{N} \wedge \mathrm{H}(\underbrace{C_f(\mathcal{U}_{...
0 votes
0 answers
83 views

SAT to k-in-3-SAT reduction

Given a 3-SAT clause. Is there a way to convert 3-SAT to k-in-3-SAT such that: The number of new variables introduced are less than the number of clauses (without adding dummy clauses etc.)? The ...
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-1 votes
1 answer
126 views

Polynomially solvable 3-SAT problem instances [closed]

Given the 3-SAT problem with $v$ variables and $c$ clauses: Is there a clause to variable ratio for which the 3SAT problem is 'easy' i.e. solvable in polynomial time? We are assuming the 3-SAT ...
2 votes
2 answers
190 views

Separating 2-SAT from Clique

Since the P vs. NP problem is still an open problem, 2-SAT and Clique might both be in P if P = NP. Is there any known complexity measure whatsoever that is already mathematically proven to ...
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0 votes
0 answers
85 views

Computational complexity of Private Computation

In a recent work (Sun2017), Sun and Jafar defined the Private Computation (PC) problem where a user wants to compute a function of $K$ datasets, using $N$ distributed and non-colluding servers, ...
11 votes
2 answers
838 views

Randomized algorithms not based on Schwartz-Zippel

Are there any problems that are known to be in a randomized complexity class (e.g. RNC, ZPP, RP, BPP, or even PP), but not in any lower non-randomized class (e.g. NC, P, NP), and whose membership in ...
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0 votes
0 answers
39 views

Query in the proof of greedy manipulation theorem (of a voting scheme)

Paper being referred to: http://www.cs.cmu.edu/~arielpro/15896/docs/paper9.pdf (The Computational Difficulty of Manipulating an Election). I have a query in Theorem 1 of this paper; specifically, in ...
1 vote
0 answers
59 views

Natural problems believed to be in EQP but not BPP

Are there any “natural” problems in $\mathsf{EQP}$ that are believed to not be in $\mathsf{BPP}$? If so, what are some exapmles?
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5 votes
1 answer
227 views

Why are some classes (ALL, ELEMENTARY, R, etc) badly behaved as oracles?

Some classes, such as ALL, ELEMENTARY, and R, are very badly behaved when used as oracles. For instance, all three of these classes trivially collapse P and EXP, even though (by the Time Hierarchy ...
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4 votes
0 answers
143 views

Is it possible that the Aanderaa–Karp–Rosenberg conjecture is just a bit false?

The Aanderaa–Karp–Rosenberg conjecture is that any non-trivial monotone property on graphs is evasive. It has been proved for several special cases, but for a general graph on $n$ vertices, we only ...
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3 votes
0 answers
119 views

Detailed proof of Theorem 2.1 in Papadimitrou book (Multitape TM to SingleTape TM)

I want to know if anybody knows a detailed proof of Theorem 2.1 of Papadimitrou's book Computational Complexity. The theorem states "Given any $k$-string Turing machine $M$ operating within time $...
10 votes
0 answers
132 views

Fastest Known Algorithm to Count Acyclic Orientations in a Graph

Given an undirected graph $G$, an acyclic orientation of $G$ is choice of orientation for each edge of $G$ (turning each edge into an arc) such that the resulting directed graph has no directed cycles....
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0 answers
26 views

Can we pick a basis for synchronous circuits which coarsens towards the target partition at every layer?

Given a Boolean function $f : \{0, 1\}^n \rightarrow \{0, 1\}$ and a Boolean basis for circuit gates $B$ (for instance $B = \{AND, OR\}$), we can construct the set of size optimal synchronous (Harper ...
1 vote
0 answers
80 views

A reduction from the maximum $k$-closure problem to the clique problem

Fix a partially ordered set $(P, \le)$ with $N$ elements and real weights $w(p)$ for each $p \in P$. A subset $S \subset P$ is called closed if for any $x, y$ with $y \in S$ and $x \le y$ we also ...
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0 votes
0 answers
104 views

Query about P/poly and Polynomial Hierarchy Collapse to $\Sigma _{2}$

I am not conversant in the complexity class $P/poly$. While reading about the class on wiki I encountered two conditional statements about it, namely: If $NP ⊆ P/poly$ then $PH$ (the polynomial ...
4 votes
0 answers
165 views

Computational Complexity of 3SAT variant with additional restrictions on variables/clauses

Given a 3SAT problem with the additional constraints that: No clause or set of clauses is the 3SAT instance is 'redundant'. Thus, this 3SAT cannot eliminate any clauses. For any/every clause, the ...
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2 votes
1 answer
172 views

An easy computable injection with a hard inverse

I was reading Charles Bennett's Thermodynamics of Computer Science and a passage (p. 926) caught my eye The construction of a reversible machine from an irreversible machine implies that the open ...
4 votes
0 answers
136 views

Computational Complexity of MIN-EQ-3-CNF

Consider the decision problem: MIN-EQ-CNF= $\{\langle\phi, k\rangle |\exists \text{CNF formula } \psi \text{ of size }\leq k\text{ that is equivalent to the CNF formula }\phi\}$ CNF is a Boolean ...
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