[Colloquium] Theory Seminars at Computer Science

[Donna Brooms via Colloquium]

Department of Computer Science & Mathematics
Combinatorics & Theoretical Seminar

Karthik Chandrasekaran
(University of Illinois at Urbana-Champaign)
 
Tuesday, November 7, 2017
Ryerson 251 @ 3:30 pm

Title: Beating the 2-factor for Global Bicut

Abstract:

In the fixed-terminal bicut problem, the input is a directed graph with two specified nodes and the goal is to find a smallest subset of edges whose removal ensures that the two specified nodes cannot reach each other. In the global bicut problem, the input is a directed graph and the goal is to find a smallest subset of edges whose removal ensures that there exist two nodes that cannot reach each other. Fixed-terminal bicut and global bicut are natural extensions of {s,t}-min cut and global min-cut respectively, from undirected graphs to directed graphs. Fixed-terminal bicut is NP-hard and admits a simple 2-approximation, which is also the best possible approximation factor assuming the unique games conjecture. In contrast, we show that global bicut admits a (2-eps)-approximation for eps>0. In this talk, I will highlight the techniques behind the (2-eps)-approximation. I will also mention some related cut problems and open questions.
Based on joint work with Kristof Berczi, Tamas Kiraly, Euiwoong Lee and Chao Xu.

Host: Prof. Yury Makarychev
(Refreshments will be served prior to the talk in Ry. 255 @ 3pm)
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