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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.

3 votes
2 answers
856 views

Formal verification in complexity theory

Reading books and papers on complexity theory, I am struck by the extreme degree to which proofs are stated in an intuitive, hand-wavy way. The alternative is to give a lot of details about the coding …
David Harris's user avatar
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14 votes
3 answers
3k views

Definition of relativization of complexity class

Is there any general definition, for a class $C$ of languages, what is the relativized class $C^A$ for an oracle $A$? Usually, these classes and their relativizations seem to be defined in an ad-hoc …
David Harris's user avatar
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1 vote
0 answers
228 views

Inherent complexity of a language --- when does it exist?

For a language $L$, you can talk about the complexity of a Turing machine $M$ which decides $L$. Can you talk about the time complexity of the language $L$ itself, i.e. say $L$ has complexity $f(n)$ i …
David Harris's user avatar
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3 votes
0 answers
364 views

Amortized analysis of data structure via potential function

One common method for proving that a data structure supports an operation in $O(f(n))$ amortized time is to construct a potential function $\Phi: \mathcal S \rightarrow \mathbf R^{+}$, which associate …
David Harris's user avatar
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1 vote
Accepted

Proof that any NP problem can be reduced (in P time) to any problem in NPC?

This is Cook-Levin theorem, look it up on Wikipedia.
David Harris's user avatar
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3 votes

We know that a permutation of N bits {0, 1}^N --> {0,1}^N can be computed by circuits of siz...

Any function $f:V^n \rightarrow V^n$ can be computed with $O(n 2^n)$ gates as follows. For each input $\langle v_1, \dots, v_n \rangle$, compute $t_v = x_1^{v_1} \wedge \dots \wedge x_n^{v_n}$ (where …
David Harris's user avatar
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5 votes

Abstract notion for energy complexity of computational problems?

The answer is no, energy cannot be considered a cost of computation. Classical computations can be transformed, with only polynomial size blow-up, to reversible computations (computations which do no …
David Harris's user avatar
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6 votes

Is P=NP relevant to finding proofs of everyday mathematical propositions?

The point is that, if P=NP, there would exist a universal algorithm (applicable not just to specific theorems) that would find proofs in time polynomial in length of the proof. Most important results …
David Harris's user avatar
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