1,301 research outputs found
Coalescence of Two Impurities in a Trapped One-dimensional Bose Gas
We study the ground state of a one-dimensional (1D) trapped Bose gas with two
mobile impurity particles. To investigate this set-up, we develop a variational
procedure in which the coordinates of the impurity particles are slow-like
variables. We validate our method using the exact results obtained for small
systems. Then, we discuss energies and pair densities for systems that contain
of the order of one hundred atoms. We show that bosonic non-interacting
impurities cluster. To explain this clustering, we calculate and discuss
induced impurity-impurity potentials in a harmonic trap. Further, we compute
the force between static impurities in a ring ({\it {\`a} la} the Casimir
force), and contrast the two effective potentials: the one obtained from the
mean-field approximation, and the one due to the one-phonon exchange. Our
formalism and findings are important for understanding (beyond the polaron
model) the physics of modern 1D cold-atom systems with more than one impurity.Comment: 10 pages, 6 figures, published versio
Consistent SDNs through Network State Fuzzing
The conventional wisdom is that a software-defined network (SDN) operates under the premise that the logically centralized control plane has an accurate representation of the actual data plane state. Nevertheless, bugs, misconfigurations, faults or attacks can introduce inconsistencies that undermine correct operation. Previous work in this area, however, lacks a holistic methodology to tackle this problem and thus, addresses only certain parts of the problem. Yet, the consistency of the overall system is only as good as its least consistent part. Motivated by an analogy of network consistency checking with program testing, we propose to add active probe-based network state fuzzing to our consistency check repertoire. Hereby, our system, PAZZ, combines production traffic with active probes to continuously test if the actual forwarding path and decision elements (on the data plane) correspond to the expected ones (on the control plane). Our insight is that active traffic covers the inconsistency cases beyond the ones identified by passive traffic. PAZZ prototype was built and evaluated on topologies of varying scale and complexity. Our results show that PAZZ requires minimal network resources to detect persistent data plane faults through fuzzing and localize them quickly
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