Expansion in Lifts of Graphs.

The central goal of this thesis is to better understand, and explicitly construct, expanding towers G_1,G_2,..., which are expander families with the additional constraint that G_{n+1} is a lift of G_n. A lift G of H is a graph that locally looks like H, but globally may be different; lifts have bee...

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Pengarang Utama: Makelov, Aleksandar A., (Author)
Pengarang Korporat: Harvard School of Engineering and Applied Sciences.
Format: Buku
Bahasa:English
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245 1 0 |a Expansion in Lifts of Graphs. 
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502 |b AB  |c Harvard University  |d 2015. 
502 |a Thesis (AB)--Computer Science, Harvard College, May 2015. 
520 3 |a The central goal of this thesis is to better understand, and explicitly construct, expanding towers G_1,G_2,..., which are expander families with the additional constraint that G_{n+1} is a lift of G_n. A lift G of H is a graph that locally looks like H, but globally may be different; lifts have been proposed as a more structured setting for elementary explicit constructions of expanders, and there have recently been promising results in this direction by Marcus, Spielman and Srivastava [MSS13], Bilu and Linial [BL06], and Rozenman, Shalev and Wigderson [RSW06]; besides that, expansion in lifts is related to the Unique Games Conjecture (e.g., Arora et al [AKK+08]). 
520 8 |a We develop the basic theory of spectral expanders and lifts in the generality of directed multigraphs, and give some examples of their applications. We then derive some group-theoretic structural properties of towers, and show that a large class of commonly used graph operations "respect" lifts. These two insights allow us to give a different perspective on an existing construction [RSW06], show that standard iterative constructions of expanders can be adjusted to give expander towers almost "for free", and give a new elementary construction, along the lines of Ben-Aroya and Ta-Shma [BATS11], of a fully-explicit expanding tower of almost optimal spectral expanders. 
653 0 0 |a Mathematics. 
653 0 0 |a Computer Science. 
655 7 |a Theses.  |2 aat 
710 2 |a Harvard School of Engineering and Applied Sciences.  |t Senior honors thesis. 
710 2 |a Harvard University,  |e degree granting institution. 
988 |a 20150410 
906 |0 MH