Cyrus Rashtchian (Theory Seminar)

"Reconstructing Trees from Traces"
Cyrus Rashtchian (UC San Diego)
Monday, October 28, 2019, 2:00 pm
EBU3B, Room 4258


We study the problem of learning a node-labeled tree given independent traces from an appropriately defined deletion channel. This problem, tree trace reconstruction, generalizes string trace reconstruction, which corresponds to the tree being a path. For many classes of trees, including complete trees and spiders, we provide algorithms that reconstruct the labels using only a polynomial number of traces. This exhibits a stark contrast to known results on string trace reconstruction, which require exponentially many traces, and where a central open problem is to determine whether a polynomial number of traces suffice. Our techniques combine novel combinatorial and complex analytic methods.

Joint work with Sami Davies (UW) and Miki Z. Racz (Princeton). Paper can be found at