O. K. Fröhlich 1885–1964

Optical conductivity of the Fröhlich polaron.

We present accurate results for optical conductivity of the three dimensional Fröhlich polaron in all coupling regimes. The systematic-error free diagrammatic quantum Monte Carlo method is employed where the Feynman graphs for the momentum-momentum correlation function in imaginary time are summed up. The real-frequency optical conductivity is obtained by the analytic continuation with stochast...

Fröhlich mass in GaAs-based structures.

The Fröhlich interaction is one of the main electron-phonon intrinsic interactions in polar materials originating from the coupling of one itinerant electron with the macroscopic electric field generated by any longitudinal optical (LO) phonon. Infrared magnetoabsorption measurements of doped GaAs quantum well structures have been carried out in order to test the concept of Fröhlich interaction...

Balfe , M . , O ' Brien , K . , Timmons , A . , Butow , P . , O

An almost O(log k)-approximation for k-connected subgraphs

We consider two cases of the Survivable Network Design (SND) problem: given a complete graph Gn = (V,En) with costs on the edges and connectivity requirements {r(u, v) : u, v ∈ V }, find a minimum cost subgraph G of Gn that contains r(u, v) internally disjoint uv-paths for all u, v ∈ V . Our main result is an O (

Finding paths of length k in O*(2^k) time

The k-path problem is to determine if a given graph contains a simple path of length at least k, and if so, produce such a path. When k is given as a part of the input, the problem is wellknown to be NP-complete. The general problem has many practical applications (cf. [3, 15]). The trivial algorithm enumerating all possible k-paths in an n-node graph uses Θ(nk) time, so it is only polynomial f...