Title
On Fortification of Projection Games
Abstract
A recent result of Moshkovitz \cite{Moshkovitz14} presented an ingenious method to provide a completely elementary proof of the Parallel Repetition Theorem for certain projection games via a construction called fortification. However, the construction used in \cite{Moshkovitz14} to fortify arbitrary label cover instances using an arbitrary extractor is insufficient to prove parallel repetition. In this paper, we provide a fix by using a stronger graph that we call fortifiers. Fortifiers are graphs that have both $\ell_1$ and $\ell_2$ guarantees on induced distributions from large subsets. We then show that an expander with sufficient spectral gap, or a bi-regular extractor with stronger parameters (the latter is also the construction used in an independent update \cite{Moshkovitz15} of \cite{Moshkovitz14} with an alternate argument), is a good fortifier. We also show that using a fortifier (in particular $\ell_2$ guarantees) is necessary for obtaining the robustness required for fortification.
Year
Venue
Field
2015
APPROX-RANDOM
Graph,Elementary proof,Algorithm,Robustness (computer science),Extractor,Spectral gap,Mathematics
DocType
Citations 
PageRank 
Conference
3
0.40
References 
Authors
10
4
Name
Order
Citations
PageRank
Amey Bhangale1106.71
Ramprasad Saptharishi218413.72
Girish Varma352.13
rakesh venkat432.77