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Electronic Colloquium on Computational Complexity

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TR09-069 | 2nd September 2009
Parikshit Gopalan

A note on Efremenko's Locally Decodable Codes

Revisions: 1

Building on work of Yekhanin and Raghavendra, Efremenko recently gave an elegant construction of 3-query LDCs which achieve sub-exponential length unconditionally.In this note, we observe that this construction can be viewed in the framework of Reed-Muller codes.

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TR09-068 | 1st September 2009
Dave Buchfuhrer, Chris Umans

Limits on the Social Welfare of Maximal-In-Range Auction Mechanisms

Many commonly-used auction mechanisms are ``maximal-in-range''. We show that any maximal-in-range mechanism for $n$ bidders and $m$ items cannot both approximate the social welfare with a ratio better than $\min(n, m^\eta)$ for any constant $\eta < 1/2$ and run in polynomial time, unless $NP \subseteq P/poly$. This significantly improves upon ... more >>>


TR09-067 | 18th August 2009
Hanna Mazzawi, Nader Bshouty

On Parity Check $(0,1)$-Matrix over $Z_p$

Revisions: 1

We prove that for every prime $p$ there exists a $(0,1)$-matrix
$M$ of size $t_p(n,m)\times n$ where
$$t_p(n,m)=O\left(m+\frac{m\log \frac{n}{m}}{\log \min({m,p})}\right)$$ such that every
$m$ columns of $M$ are linearly independent over $\Z_p$, the field
of integers modulo $p$ (and therefore over any field of
characteristic $p$ and over the real ... more >>>



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