Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar (in cooperation with M. Ghaffari, A. Steger and B. Sudakov)

Mittagsseminar Talk Information

Date and Time: Tuesday, February 17, 2004, 12:15 pm

Duration: This information is not available in the database

Location: This information is not available in the database

Speaker: Alexander Hall

Flows over Time

Flow variation over time is an important feature in network flow problems arising in various applications such as road or air traffic control, production systems, communication networks (e.g., the Internet), and financial flows. The common characteristic are networks with capacities and transit times on the edges which specify the amount of time it takes for flow to travel through a particular edge. Moreover, in contrast to static flow problems, flow values on edges may change with time in these networks.
I will give a short introduction to the flows over time problem and mention new complexity and inapproximability results for the case where the transit times are assumed to be constant.
In many real-world applications transit times are not constant but depend on the current flow situation in the network. For the model where the transit time of an edge is given as a nondecreasing function of the rate of inflow into the edge I will present the ideas underlying an FPTAS for the `quickest multicommodity flow problem with bounded cost'. It can be shown that this problem is NP-hard even in the single commodity case.

This is joint work with Steffen Hippler, Katharina Langkau, and Martin Skutella.


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