Questions tagged [cc.complexity-theory]

P versus NP and other resource-bounded computation.

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Low barrier to entry Computational Complexity problems

I could use some help navigating which areas of Computational Complexity (e.g. CCC, STOC topics) require the least amount of background knowledge to get involved in basic research. I am looking to ...
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Given a Boolean formula, does there exist a small circuit that computes a satisfying assignment?

The 3-SAT problem can be defined as follows: 3-SAT Input: A 3-CNF formula $\phi$ of size $m$ with $n$ variables. Question: Does there exist a variable assignment that satisfies $\phi$? ...
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Consequence of Decision Tree Complexity of $k$-SUM Problem

Ezra and Sharir showed the $O(n^2\log^2 n)$ linear decision tree complexity for $k$-SUM problem [1], which improves the $O(n^3\log^3 n)$ complexity result of Cardinal et al [2]. It is known that $k$-...
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What can we say about AM[log n]?

It is known that $\textbf{AM}[O(1)] = \textbf{AM}$. Since $\textbf{IP}=\textbf{PSPACE}$ we have $\textbf{AM}[poly(n)] = \textbf{PSPACE}$. Can we say something about $\textbf{AM}[ f(n)]$, where $f$ ...
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How hard is PromiseFlowFree?

Playing more Flow Free, I think I've realized why I'm so amazingly brilliant at this game: The objective is to connect all pairs while covering the entire board, but in every puzzle there is always ...
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SETH-like hypothesis for machine with oracle access to some level of PH

I am wondering if hypothesis such as Strong Exponential Time Hypothesis (SETH) have been studied for problems being in a higher level of the polynomial hierarchy when we give the machine access to an ...
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Recognition of a primitive root

Adleman and McCurley published a paper in 1994 called "Open problems in number theoretic complexity, II" (http://ww.cstheory.com/papers/open.ps.gz) Problem 18 of this list of open problems is about ...
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Why is it so difficult to study Sum of Squares (SoS) algorithms with degree $d>4$?

In many publications on the computational complexity of Sum of Squares (SoS) algorithms, it is typical to study the degree-$4$ relaxation; e.g. Rounding Sum-of-Squares Relaxations Sum-of-Squares ...
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443 views

Is there a program for theory of incompleteness in $NP$?

Motivated by Suresh's post, Techniques for showing that problem is in hardness limbo, it seems that there might be an underlying theory that explains why some of these problems can not be complete for ...
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350 views

Number of non-isomorphic induced subgraphs of a graph

Given a simple undirected grap, how many induced subgraphs does it have that are not isomorphic to each other? (or in a descision version, does it have fewer than k non-isomorphic induced subgraphs). ...
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Implications of the impossibility of efficient sampling from random non-Hamiltonian graphs

Nisan's answer to this question shows the Impossiblity of efficient sampling from random non-Hamiltonian graphs (unless $NP=coNP$). I am interested in the implications of this conjecture. Does the ...
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What relations are there between a problem hardness and the hardness of verifying a witness?

I had some hard times trying to formulate the question, so I'll start with some examples: Suppose you are given a Dominating Set instance, $<G,k>$. Now suppose I give you a set of vertices $D$ ...
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Information theoretic characterization and consequences of reductions between computational problems

For two computational problems $A$ and $B$ in complexity class C (let say $NP$), the existence of a reduction $A <_m^L B$ computable in class (say $L$) implies that $A$ is not computationally ...
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Does Dinur's proof of PCP Theorem imply a procedure for reconstructing a witness?

In Section 3.2 of On Syntactic versus Computational Views on Approximability by Khanna, et al., the authors state that an adaptation of the results from Proof Verification and Hardness of ...
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Size complexity of probabilistic two-way automata for a Boolean function

I'm interested in computing Boolean functions $f:\{0,1\}^n\rightarrow\{0,1\}$ with two-way finite automata and I will measure the complexity of a Boolean function by the number of states for the ...
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Universal tractable problem solver

Consider $X$ an $\mathsf{NP}$-complete language e.g. $3-SAT$. I'm looking for an algorithm $A$ for solving $X$ with the following property. Given $M \subset \lbrace 0, 1 \rbrace^*$ any set of words s....
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184 views

Communication complexity of random functions with limited independence

Let $X_0, \ldots, X_{2^n-1}$ be $k$-wise independent random $0/1$ variables over a sample space $\Omega$ and $Prob \left[ X_i = 1 \right] = p$ for every $i$ and some $0 < p < 1$. Let assume $n$ ...
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The power of randomized logspace with two-way access to the random tape

Let $\mathsf{ZPL}$/$\mathsf{RL}$/$\mathsf{BPL}$ denote the classes of the languages which are accepted (with zero/one-side/two-side error) by a logspace Turing machine with one-way access to the ...
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Hardness of Approximation results for Special Set Packing Problem Wanted

Is there any inapproximability result for the following NP-hard problem, which is a special case of the weighted Set Packing Problem? The general Set Packing Problem would be: Given A Collection of ...
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252 views

Complexity of reachability in Markov Chains

Is anything known about the complexity of the following problem beyond membership in PTIME: Given a finite Markov chain $M$, an initial state $q_0$ and a set $F$ of (absorbing) states, is the ...
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Computing the Fourier-Walsh coefficients of an arithmetic circuit

Given an $f$-fan in arithmetic circuit of depth $d$ over $GF(q)$ (for some prime $q$) and the set of variables $(x_1,\ldots,x_n)$, what is the state of the art upper bound for calculating the Fourier-...
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Complexity of Exactly $A$-SAT

Let define the "Exactly $A$-SAT" problem : Given a CNF formula $F$ and a set $A$ of positive integers, is it true that the number of models of $F$ is in $A$? What is the complexity of Exactly $A$-...
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Are the minimal quantum and classical span programs the same?

A span program is a linear-algebraic way of specifying a boolean function introduced here which has found recent application in quantum query complexity. A span program for a function $f: \{0,1\}^n \...
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Complexity class that captures linear or nearly-linear functions

A particular model I am working with can only compute a function $f: \{0,1\}^n \rightarrow \{0,1\}$ iff $f(x_1,...,x_n)$ is a linear combination (over $\text{GF}(2)$) of the $x_i$'s or has at most a ...
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Deterministic Parallel Algorithm for ILP with small number of variables and small coefficients

Given a set of $n$ linear inequalities in $d$ variables where the coefficients are integers of size bounded by $O(\log{n})$ is there a known deterministic parallel algorithm that runs in time $(d\log{...
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181 views

Oracle sparating FIP for bounded-depth Frege from FIP for Frege (and hardness conditions on DDH)

Is there an oracle such that in the relativized world, bd-Frege (bounded depth Frege propositional proof system) has FIP (feasible interpolation property) but Frege does not have FIP? Such an oracle ...
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552 views

Extracting randomness from Santha-Vazirani sources using a seed of constant length

This question is actually an exercise problem from Salil Vadhan's draft survey "Pseudorandomness" marked with a star (*) (see Chapter 6, Problem 6.6). I do not know other references. We say a random ...
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289 views

Hard-on-Average, Quasi-Polynomial-Time Problems

In a paper by Raphael Pass, he writes (page 162): ... most natural problems that we believe are hard on average for polynomial time are also believed hard for quasi-polynomial time. In another ...
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Nondeterminstic Linear Time vs Other Complexity Classes

Is it known whether or not nondeterministic linear time contains $P$ and/or smaller classes such as Uniform-$NC^1$?
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Efficient quantum algorithm for CLASSICAL FFT

Is there a known improvement on the current O(n*log(n)) algorithm for CLASSICAL FFT using quantum computation? 'n' is the number of samples. I need to find the amplitude and phase of the K dominating ...
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220 views

Fischer and Rabin's theorem (1974) for theories of “additive” structures

Fischer and Rabin's Super-Exponential Complexity of Presburger Arithmetic (1974) has the following theorem. (Theorem 12) Let $U$ be any class of additive structures, so if $A = (A, +) \in U$, ...
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286 views

Is there any algorithm outputing $e$ in real time?

The Hartmanis-Stearns Conjecture says that a number computed in real time by a Turing Machine is either rational or transcendental. We know that there is some transcendental (Liouville) number that ...
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Complexity Class Equalities on the Edge of Inconsistency

What are some of the most extreme potential equalities between computational complexity classes (especially if there is a barrier to refuting them)? These may give us an opportunity to prove better ...
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402 views

Worst-case computational complexity of solving Diophantine equation

Manders and Adleman proved that the following decision problem is NP-complete: Given integers $a,b,c>0$, does the quadratic equation $ax^2+by-c=0$ have a solution in integers $x,y>0$? The ...
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Is the class NSC closed under complement?

The class $\mathsf{NSC}$ is defined as $\bigcup_{k\in\mathbb{N}}\mathsf{NSC}^k$, where $\mathsf{NSC}^k = \mathsf{NTIMESPACE}[\mathsf{poly},\mathsf{log}^k]$. In a 1991 paper Mix Barrington and McKenzie ...
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130 views

Quantum complexity separation evading the algebrization barrier?

Question: Which results in complexity theory use quantum computing to evade the algebrization barrier? I am aware of the separation $NEXP\not\subset ACC$, which evades all barriers, but it does not ...
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What are problems in SC we don't know to be in NC?

NC and SC are, roughly, the class of problems decidable by shallow circuits of polynomial size and the class of problems decidable by narrow circuits of polynomial size, respectively. They are both ...
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Proving P-Isomorphism between two languges

The famous Isomorphism Conjecture states that all NP-complete problems are isomorphic via polynomial-time computable and invertible bijections (reductions). Padability is the only property that I know ...
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EXPTIME-complete propositional satisfiability problem

SAT is NP-complete, QBF is PSPACE-complete, DQBF is NEXPTIME-complete. Is there any extension of QBF or restriction of DQBF that is EXPTIME-complete? Added later: a definition of DQBF can be found ...
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Statistical Algorithms vs Convex Relaxations - Planted Clique

I am trying to understand exactly what the lower bounds for the query complexity of statistical algorithms imply for convex relaxations for the planted clique problem ? A recent paper by Feldman, ...
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Is this graph polynomial known? Can it be efficiently computed?

Consider a connected simple graph $G$ with $n$ vertices and $m$ edges. View each edge $\ell$ as a transposition $t_{\ell}$ acting on the set of vertices. [To be more explicit, given an edge $\ell$ ...
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NP-hardness of tasks graph assignment to two heterogenous servers

I have a problem with determinig if the following assignment problem is NP-hard. Any comments and suggestions would be appreciated. Problem definition Given is a directed acyclic graph $G=(V,E)$ ...
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Best algorithm for inversion of symmetric positive-definite matrices

As I know, the time complexity for usual inversion algorithm of general matrix is $O(n^3)$. In recent years, there is a improvement from $O(n^3)$ to $O(n^{2.8....})$. However, does there exists a ...
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271 views

Stronger reductions in parameterized complexity

An FPT-reduction between parameterized problems $P$ and $Q$ is a pair of functions $f$ and $p$, such that every instance $x$ of $P$ with parameter $k$ is mapped to an instance $f(x,k)$ of $Q$ with ...
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Unique factorization representation and complexity

Suppose that $N = p_1^{a_1} p_2^{a_2} ... p_k^{a_k}$ with $p_i$ prime and $a_i \geq 1$. Given a representation of the factorization of $N$ and an integer $m$ (using alphabet $\Sigma = \{0,1,,\}$): ...
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Why do we believe $\mathsf{fewP \ne NP}$?

$\mathsf{fewP}$ ($\mathsf{NP}$ with few witnesses, see the zoo) is one of the important ambiguity-bounded sub-classes of $\mathsf{NP}$. There are interesting natural problems in this class that are ...
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Generalized sequential machine synthesis subject to language equivalence/inclusion and reachability

A generalized sequential machine (GSM) is a generalization of a Mealy machine where on each transition one input symbol is read and 0 or more output symbols are written. As in a Mealy machine, we ...
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Physical Proof for P versus BPP

Lipton asks for a physical proof of $P\neq NP$. Can we even ask for a physical proof for understanding $P=BPP$ or $P\neq BPP$? Is there anything in physics that lets us avoid randomness? ...
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The size of output in circuit complexity

In circuit complexity we have one circuit for each input size. The size of the output is determined solely by the size of the input. So it seems to me that taken in its strict sense there are ...
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k-CNF ←→ k-DNF conversion to minimize errors

the following problem/question seems fundamental/hard. it appears in some circuit theory proofs, graph theory, and maybe elsewhere. looking for any nontrivial insight. will add various known/nearby ...