Probabilistically checkable proofs

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1answer
156 views

A purely graph-theoretic explanation of the reduction from Unique Label Cover to Max-Cut

I am studying the Unique Games Conjecture and the famous reduction to Max-Cut of Khot et al. From their paper and elsewhere on the internet, most authors use (what to me is) an implicit equivalence ...
5
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3answers
356 views

If SAT is in PCP, for some constant q, then P = NP

I have seen this statement before, but I haven't really seen a proof of it: If $SAT\in PCP_{1,2^{−q}}[\log(n),q]$, for some constant $q$, then $P = NP$. Now, if $SAT\in PCP_{1,2^{−q}}[\log(n),q]$, ...
6
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1answer
113 views

Can NP-hard statements be proved by PCPs that only involve reading 2 bits?

For non-negative integers q, let PCP(q) denote the set of promise problems that have polynomial-length probabalistically checkable proofs over the binary alphabet in which the verifier only reads q ...
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0answers
343 views

From CHSH inequality to CHSH game

I have been going through Certifiable quantum dice: or, true random number generation secure against quantum adversaries by Umesh Vazirani and Thomas Vidick. They have used entangled particles as ...
2
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2answers
107 views

How are PCPs and ZKPs related?

I only have a (very) introductory knowledge about the Hardness of Approximation and PCP theorem, and I am wondering if it has any specific implications (or can somehow be studied) with Zero Knowledge ...
2
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0answers
63 views

Bivariate low-degree polynomial testing of Polishchuk-Spielman

In the seminal paper of Polishchuk and Spielman where they give a construction of nearly linear sized $PCP$ for an $NP$ problem, one of the key ingredients is a low-degree test for bivariate ...
5
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2answers
137 views

Is a software implementation of a PCP encoder available?

We all know the PCP Theorem. Is there any software package availalbe taking a CNF in e.g. DIMACS format as input, and producing a PCP encoding in the same format as output? It might be interesting to ...
2
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2answers
259 views

Multi prover, verifier games and PCP theorem

This question came up while I was going through Siu On Chan's paper on Approximation Resistance. My question is not really related to the paper though. I also guess that this is more of a reference ...
1
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1answer
102 views

number of PCP queries

we know from the PCP theorem that $PCP[O(log(n)),O(1)]=NP$,what if we choose specific number of queries will the theorem hold ?
6
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4answers
655 views

How to start studying topics Hardness of approximation and PCP's

Recently I have done an introductory course on complexity theory ( which covered 90% of sipser text book). Now I would like to study the topics Hardness of approximation and PCP's. Can you please ...
7
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0answers
194 views

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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0answers
82 views

What is the query and randomness complexity for very efficient PCPs?

In the 2012 paper On the Concrete-Efficiency Threshold of Probabilistically-Checkable Proofs, the authors state the following (paraphrased from page 11). Theorem 1 (informal). There is a PCP ...
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4answers
3k views

Hardness of approximation without the PCP theorem

An important application of the PCP theorem is that it yields "hardness of approximation" type results. In some relatively simpler cases one can prove such hardness without PCP. Is there, however, any ...
15
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3answers
387 views

$\mathcal{MA}$ in terms of $\mathcal{PCP}$

The probabilistic proof system $\mathcal{PCP}[f(n),g(n)]$ is commonly referred to as a restriction of $\mathcal{MA}$, where Arthur can only use $f(n)$ random bits and can only examine $g(n)$ bits of ...
10
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1answer
320 views

One-sided errors in probablistic proof systems

In most probabilistic proof systems ( PCP theorem, for instance), the error-probabilities are usually defined on the side of the false-positives, i.e., a typical definition could look like : if $x ...
9
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1answer
284 views

Connection between PCP and L=SL

The book by Arora and Barak contains in chapter notes on PCP We note that Dinur's general strategy is somewhat reminiscent of the zig-zag construction of expander graphs and Reingold's ...
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0answers
296 views

Interesting PCP characterization of classes smaller than P?

The PCP theorem, $\mathsf{NP} = \mathsf{PCP}(\mathsf{log}\, n, 1)$, involves probabilistically checkable proofs with polynomial time verifiers, so the smallest class that can be characterized in this ...
3
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1answer
343 views

Consequences of Unique Games being a NPI problem

Assume that UG is $\mathsf{NPI}$, i.e. not solvable in $\mathsf{P}$ nor in $\mathsf{NP\text{-}complete}$ (so UGC is false). Is it still NP-hard to give a $(2-\epsilon)$ polytime approximation ...
0
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1answer
284 views

Non adaptive PCP

So this is a question from Arora, Barak textbook which was on our homework. I submitted it so no worries. :) The question asks us to simulate an adaptive PCP with a non-adaptive one. It says this can ...
12
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1answer
182 views

Is there a continuous version of parallel repetition theorem

Raz's Parallel pretition theorem is an important result in PCP, inapproximation, etc. The theorem is fomalized as follows. A game $G=(\mathcal{S},\mathcal{T},\mathcal{A},\mathcal{B},\pi, V)$, where ...
3
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0answers
608 views

More legent proof of MIP=NEXP using the PCP theorem

Can we prove $\mathsf{MIP}=\mathsf{NEXP}$ using the PCP theorem $\mathsf{NP}=\mathsf{PCP(log(n),O(1))}$ as a shortcut? $\mathsf{MIP}$ is the class of languages with multi-prover interactive proof ...
8
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2answers
361 views

Do good PCPs for NP give us good PCPs for the entire polynomial hierarchy?

The PCP Theorem states that every decision problem in NP has probabilistically checkable proofs (or equivalently, that there exists a complete and quasi-sound proof system for theorems in NP using ...
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2answers
760 views

Super-polynomial time approximation algorithms for MAX 3SAT

The PCP theorem states that there is no polynomial time algorithm for MAX 3SAT to find an assignment satisfying $7/8+ \epsilon$ clauses of a satisfiable 3SAT formula unless $P = NP$. There is a ...
2
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1answer
281 views

On the need for a self-correcting function in the PCP theorem

Original proof of the PCP theorem, uses self-correction property of linear functions. Assume we have $f: \{0,1\}^n \rightarrow \{0,1\}$, a function or table of values, that is $(1-\delta)$-close to ...
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0answers
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Is there a gap amplification type of result for the Graph Isomorphism Problem?

Suppose $G_1$ and $G_2$ are two undirected graphs on vertex set $\{1, \dotsc, n\}$. The graphs are isomorphic if and only if there is a permutation $\Pi$ such that $G_1 = \Pi(G_2)$, or more formally, ...
4
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1answer
182 views

Effect of serial repetition on soundness of a PCP, and what is special with 1/2?

As far as I know, following operations convert a $PCP_{1,s}[O(\log n),O(1)]$ , to a $PCP_{1,s’}[O(\log n),O(1)]$, with following $s’$ : By constant number of applications of serial repetition: can ...
2
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1answer
139 views

hardness of approximation result for a Min-CSP, by reduction from PCPs

Reduction from PCPs allow us to prove hardness of approximation results for a number of constraint satisfaction problems. I've seen such a reductions only for Max-CSPs. Is this possible only for ...
6
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1answer
251 views

Approximating Random MAX-k-SAT

It is known [de la Vega & Karpinski 2002] that random instances of MAX-3-SAT on $n$ variables can be approximated up to fraction at least 8/9 w.h.p. tending to 1 as $n$ tends to infinity. Should ...
8
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1answer
313 views

Degree reduction step in Dinur's proof of the PCP theorem

In the degree reduction step of Dinur's proof, the input graph $G$ is transformed into a graph $G'$ by replacing each vertex $v \in V(G)$ by a set of vertices, $cloud(v)$, such that $|cloud(v)| = ...
16
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2answers
603 views

Is there a simple argument that shows that the unique games conjecture implies the PCP theorem

how can one show that what is relation between "Unique games conjecture" and "PCP theorem"? how does one explain "Unique games conjecture" is stronger form of "PCP theorem"?
6
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1answer
290 views

Alphabet Reduction Step in PCP Proof

I understand that the purpose of the alphabet reduction step in Dinur's proof of the PCP theorem is to reduce the alphabet after the graph powering stage. However, I don't see why the alphabet needs ...
11
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1answer
391 views

PCP Theorem - Alphabet Reduction Step

What follows might seem stupid (and that probably reflects my poor understanding - so please bear with me) I had a query on PCP theorem. We know that after the first three steps viz. Degree ...
6
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2answers
291 views

PCPs with imperfect completeness

The traditional definition of PCPs have perfect completeness -- If $x\in L$, then the prover can give a proof on which the verifier (on reading constantly many bits) always accepts. Suppose we modify ...
8
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2answers
501 views

Quantum PCP and hardness of simulating of Hamiltonians

I have a few questions about Quantum PCP conjecture: What is the statement of the quantum PCP conjecture? What implications would Quantum PCP theorem have for simulating of Hamiltonians? Is it ...
9
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3answers
402 views

Hard gaps in maximum constraint satisfaction problems?

An equivalent formulation of PCP theorem is: For Max 3-SAT it is $NP$-hard to distinguish between satisfiable formulas and formulas where at most $r$-fraction of the clauses are satisfiable (for some ...
7
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2answers
709 views

PCP theorem and proof complexity?

It is known that if $P=NP$ then $CoNP= PCP[O(log(n)),O(1)]$. Also, it is known that $NEXP=PCP[poly(n),poly(n)]$. It appears that PCP can't tell us which natural problems are not in $NP$. I wonder if ...
0
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3answers
713 views

PCP characterization of NP

The PCP theorem (NP= PCP(log n, O(1)) )is a major result in complexity theory with many applications such as proving hardness of approximate results. However, it seems to me that it does not offer any ...
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11answers
2k views

What are good references to understanding the proof of the PCP theorem?

I'm familiar with a lot of results that use the PCP theorem (mainly in approximating algorithms), but I've never come across a clear explanation of the PCP theorem (ie, that NP = PCP(O(log(n)),O(1))). ...