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This is a branch that includes: computational complexity theory; complexity classes, NP-completeness and other completeness concepts; oracle analogues of complexity classes; complexity-theoretic computational models; regular languages; context-free languages; Komolgorov Complexity and so on.

16 votes
Accepted

Non-constructive proofs vs. efficient algorithms

As others have noted there are several different meanings for constructive. I. Constructive proof in the sense of constructive mathematics This meaning views an object as existing if we have a descrip …
The Amplitwist's user avatar
7 votes

Solving NP problems in (usually) Polynomial time?

Your post seems to assume something like $\mathsf{P} \neq \mathsf{NP}$ and that an $\mathsf{NP\text{-}complete}$ problem is difficult to solve at least in theory. As you are probably aware, although w …
Community's user avatar
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2 votes

How to define the input of computable function or Turing machine over real numbers

A good book on the complexity of real constants and functions is Ker-I Ko's "Computational Complexity of Real Functions", 1991.
Kaveh's user avatar
  • 5,502
3 votes

A programming language that can only create algorithms with polynomial runtime?

Yet another perspective (and IMHO a more natural one) is descriptive complexity theory (check also this Wikipedia article). They study the question from a perspective different from the one mentione …
Community's user avatar
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5 votes
Accepted

$\mu$-recursive definitions for the complexity classes P, NP, etc

Yes, there is. See [Cob64]. The idea is to replace primitive recursion in the definition of primitive recursive functions with bounded recursion on notion. Another more delicate approach is taken i …
Kaveh's user avatar
  • 5,502
3 votes
0 answers
256 views

Oracle separating FIP for bounded-depth Frege from FIP for Frege (and hardness conditions on...

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 …
7 votes
0 answers
297 views

Feasible Type Theories

I am looking for references about efficient type theories, efficiency in the sense of computational complexity, and type theory in the sense of Martin-Lof's type theories. Has there been any studies …
7 votes
Accepted

Oracle Results: P^A = NP^A

There is an oracle $A$ s.t. $\mathsf{P}^A = \mathsf{NP}^A$. The oracle normally used for the theorem is the set TQBF which is a $\mathsf{PSpace\text{-}complete}$ set. $\mathsf{PSpace} \subseteq \math …
Kaveh's user avatar
  • 5,502
0 votes

How small can a language in NP\P be?

To have a set $A\subseteq \{2\Uparrow n \mid n\in \mathbb N \}$ s.t. $A\in \mathsf{NP} -\mathsf{P}$, it suffices to have a set $A' \in \mathsf{NTime}(2\Uparrow n) - \mathsf{DTime}(2\Uparrow n)$ and l …
Kaveh's user avatar
  • 5,502
3 votes

Ordinals and complexity classes

You may want to check "Dynamic Ordinal Analysis" by Arnold Beckmann which is an attempt to define a finer notion to classical ordinals that can be used ti distinguish between complexity classes.
Kaveh's user avatar
  • 5,502
1 vote

Has Oracles actually provided intuition for proving anything in Complexity Theory?

IIRC, the circuit complexity classes like $\mathsf{AC^0}$ were studied originally for proving relativization results. A classical example is Furst, Saxe, and Sipser, "Parity, Circuits, and the Polynom …
Kaveh's user avatar
  • 5,502
3 votes

Formal verification in complexity theory

Generally complexity theorist prefer to use as little formalism as possible. $\mathsf{IP}=\mathsf{PSpace}$ is on the list here but it doesn't seem that it has been verified with a proof assistant. I …
Kaveh's user avatar
  • 5,502
5 votes

Definition of relativization of complexity class

There isn't one correct definition of a relativization of a complexity class. Depending on the circumstances there are different definitions which are useful. So we don't have a single way of defining …
Kaveh's user avatar
  • 5,502
6 votes

Proof systems and their hierarchy

It is an open problem if there is an optimal propositional proof system. Therefore we don't know if ZFC as a propositional proof system is optimal either. ZFC as propositional proof system can p-simu …
Kaveh's user avatar
  • 5,502
13 votes
0 answers
2k views

How can an approach to $P$ vs $NP$ based on descriptive complexity avoid being a natural pro...

EDIT: This question has been modified to make it a stand-alone question. Feel free to retract your votes for the previous version. Here are Vinay Deolalikar's paper, and Richard Lipton's first post ab …

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