Title
The Chasm at Depth Four, and Tensor Rank : Old results, new insights.
Abstract
Agrawal and Vinay [AV08] showed how any polynomial size arithmetic circuit can be thought of as a depth four arithmetic circuit of subexponential size. The resulting circuit size in this simulation was more carefully analyzed by Korian [Koiran] and subsequently by Tavenas [Tav13]. We provide a simple proof of this chain of results. We then abstract the main ingredient to apply it to formulas and constant depth circuits, and show more structured depth reductions for them. In an apriori surprising result, Raz [Raz10] showed that for any $n$ and $d$, such that $ \omega(1) \leq d \leq O\left(\frac{\log n}{\log\log n}\right)$, constructing explicit tensors $T:[n]^d \rightarrow F$ of high enough rank would imply superpolynomial lower bounds for arithmetic formulas over the field $F$. Using the additional structure we obtain from our proof of the depth reduction for arithmetic formulas, we give a new and arguably simpler proof of this connection. We also extend this result for homogeneous formulas to show that, in fact, the connection holds for any $d$ such that $\omega(1) \leq d \leq n^{o(1)}$.
Year
Venue
DocType
2016
Electronic Colloquium on Computational Complexity (ECCC)
Journal
Volume
Citations 
PageRank 
abs/1606.04200
9
0.49
References 
Authors
20
4
Name
Order
Citations
PageRank
Suryajith Chillara1143.68
Mrinal Kumar2377.11
Ramprasad Saptharishi318413.72
V. Vinay4486.38