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Questions tagged [relativization]

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Does $A^B = A^C$ imply $B = C$?

I am familiar with the Baker, Solovay, Gill result of non-relativization of P vs NP problem. They showed that $\exists A \text{ s.t }P^A \neq NP^A$. But since we are referring to $P, NP$ as models of ...
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Baker, Gill, and Solovay has shown in their famous paper, that there are oracles $A$ and $B$ with $P^A = NP^A$ and $P^B \not= NP^B$. So, one can't solve the $P$ vs. $NP$ Problem with methods like ...
1 vote
33 views

Why results based on padding generally fail to relativize?

I have read in the Algebrization paper that, if we only allow polynomially-long queries to oracles, then, results based on padding will not relativize. For instance: assuming that $A$ is a PSPACE-...
• 437
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Understanding a black-box vs white-box simulation and relativization

I am trying to understand the relativization barrier from Baker Gill Solovay (BGS). About this barrier, I have heard that it only applies when using a black-box simulation. Hence, my question is, what ...
• 437
155 views

Show that $P^A \neq EXP^A$ for all oracles A

I knew that $P \neq EXP$ by Time Hierarchy Theorem. But, I'd like to show that $P^A \neq EXP^A$ for all oracles A. How can I do it? I knew that If I make A=EXP, PSPACE, NP, and many others, then this ...
• 729
1 vote
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How do we know that this Karp-Lipton theorem is derived from relativizing arguments?

Luca Trevisan wrote, " The oracle $C$ tells us that we cannot have a relativizing proof that derives the $𝑁𝑃 ⊈ 𝑃/𝑝𝑜𝑙𝑦$ conclusion from the $𝑃 ≠𝑁𝑃$ assumption, so a theorem such as Karp-...
• 729
243 views

How to tell if a proof relativizes?

If I have a proof for a separation between two complexity classes (using no oracles) and I want to see if it relativizes, how do I go about doing so? Especially in the case where there already exist ...
• 355
165 views

Why is $NP \subseteq P \implies NP^A \subseteq P^A$ false?

My question is about why does the result of Baker-Gill-Solovay not prove that $P \neq NP$. There have been several questions on this forum about this topic perhaps but I couldn't find my specific ...
• 141
1 vote
55 views

Which is harder, an NP-complete problem or the Raz-Tal oracle problem?

This is a (hopefully) sharper version of a question that I asked previously. Which of these algorithms is believed to have a longer asymptotic runtime? The optimal algorithm guaranteed to solve some ...
• 1,096
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Do relativized relations between complexity classes tell us anything about the nonrelativized relation?

The existence of relativized relations between complexity classes seems to often be treated as "circumstantial" evidence about the "true" or "real-world" (i.e. nonrelativized) relation between the ...
• 1,096
55 views

Finding a language that is $NP^L$-complete

I'm trying to prove a theorem and as a lemma I would like to identify an $NP^L$-complete language. I was thinking something like a machine that can decide $SAT$ equipped with an oracle for $L$ can ...
• 205
89 views

The power of relativised proofs

I've been trying to understand why, for instance, even though there are oracles $A$ for which $P^A \neq NP^A$, we still don't know if $P=NP$. As I understand it, it's because it's easy to construct ...
• 53
1 vote
22 views

Any barrier result for this kind of (non-relativising) technique?

We think that non-deterministic machines are more powerful than deterministic machines, by giving an oracle access to $P\subseteq L\subseteq NP$, it seems reasonable to expect there's some $L$ that is ...
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Complete problems and relativization barriers for nonuniform complexity classes

Do nonuniform complexity classes like NP/poly have complete problems? Are there relativization barriers for separations of nonuniform complexity classes? One way to interpret the second question is ...
• 5,390
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How can I show that the Cook-Levin theorem does not relativize?

The following is an exercise which I am stuck at ( source: Sanjeev Arora and Boaz Barak; its not homework ) : Show that there is an oracle $A$ and a language $L \in NP^A$ such that $L$ is not ...
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Is $BQP$ in $P^{NP}$?

I read in the introduction of this paper http://www.scottaaronson.com/papers/uncompute.pdf that there is a problem $B$ such that $BQP^B \not\subset P^{NP^B}$, and that $B$ is in $BPP$. But, using ...
• 143
229 views

Relativization of NP-completeness [duplicate]

This is actually exercise 3.7 from "Computational Complexity: A Modern Approach". I need to prove that the NP-Completeness of 3-sat does not relativize, i.e. I need to show that that exists some ...
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The meaning of relativization

I don't understand the notion of relativization. I expose with an example. Consider a class $A$ that contains $P$, e.g. $NP$. Why $P^A$ is not necessarily equal to $A$? I can naively think that if one ...
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Is it axiomatic that the Time Hierarchy Theorem holds true in all relativized worlds?

I learned from this post that ${\sf DTIME}^{\text{EXP}}(n^k) \neq \text{EXP}$ for a fixed $k$ for otherwise the Time Hierarchy Theorem would fail in that relativized world. However, is it possible to ...
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183 views

Why does the principle of locality of computation not relativize?

Although I have trouble understanding oracle TMs, I appreciate that non-relativizing techniques will be needed to resolve P vs. NP (as well as most other open problems in TCS). However, one of the ...
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Why are non-relativizing proofs preferred to relativizing ones?

I apologize, but even after these two other posts: here and here I'm still having trouble understanding oracle TMs and relativization. This question comes at the issue from a different angle: Why ...
• 1,631
813 views

Confusion about the Time Hierarchy Theorem and relativization

I know that $\mathsf{P}^A = \mathsf{EXP}$ for any $\mathsf{EXPTIME}$-complete language $A$. Is it true that $\mathsf{DTIME}^A(n^k) = \mathsf{EXP}$ for any fixed $k$ and any $\mathsf{EXPTIME}$-...
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288 views

For complexity classes A and B, what does $A^B$ mean?

What does $A^B$ mean where A and B are complexity classes? The "Polynomial Hierarchy" page says: $A^B$ is the set of decision problems solvable by a Turing machine in class A augmented by an oracle ...
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Intuition behind Relativization

I take course on Computational Complexity. My problem is I don't understand Relativization method. I tried to find a bit of intuition in many textbooks, unfortunately, so far with no success. I will ...
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4k views

An oracle to separate NP from coNP

How to prove that $\mathsf{NP}^A \neq \mathsf{coNP}^A$ ? I am just looking for a such oracle TM $M$ and a recursive language $L(M) = L$ for which this holds. I know the proof where you show that ...
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When I was explaining the Baker-Gill-Solovay proof that there exists an oracle with which we can have, $\mathsf{P} = \mathsf{NP}$, and an oracle with which we can have $\mathsf{P} \neq \mathsf{NP}$ to ...