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randomness in TCS


Theoretical Comp. Sci.

Sums of independent random variables with unbounded variance ★★

Author(s): Feige

Conjecture   If $ X_1, \dotsc, X_n \geq 0 $ are independent random variables with $ \mathbb{E}[X_i] \leq \mu $, then $$\mathrm{Pr} \left( \sum X_i - \mathbb{E} \left[ \sum X_i \right ] < \delta \mu \right) \geq \min \left ( (1 + \delta)^{-1} \delta, e^{-1} \right).$$

Keywords: Inequality; Probability Theory; randomness in TCS

Posted by cwenner
updated April 2nd, 2009
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Theoretical Comp. Sci. » Complexity » Hardness of Approximation

Refuting random 3SAT-instances on $O(n)$ clauses (weak form) ★★★

Author(s): Feige

Conjecture   For every rational $ \epsilon > 0 $ and every rational $ \Delta $, there is no polynomial-time algorithm for the following problem.

Given is a 3SAT (3CNF) formula $ I $ on $ n $ variables, for some $ n $, and $ m = \floor{\Delta n} $ clauses drawn uniformly at random from the set of formulas on $ n $ variables. Return with probability at least 0.5 (over the instances) that $ I $ is typical without returning typical for any instance with at least $ (1 - \epsilon)m $ simultaneously satisfiable clauses.

Keywords: NP; randomness in TCS; satisfiability

Posted by cwenner
updated February 27th, 2009
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