18,079 research outputs found
Competitive Online Searching for a Ray in the Plane
We consider the problem of a searcher that looks, for example, for a lost flashlight in a dusty environment. The searcher finds the flashlight as soon as it crosses the ray emanating from the flashlight. In order to pick it up, the searcher moves to the origin of the light beam. We compare the length of the path of the searcher to the shortest path to the goal.
First, we give a search strategy for a special case of the ray search---the window shopper problem---,
where the ray we are looking for is perpendicular to a known ray. Our strategy achieves a competitive factor of , which is optimal. Then, we consider rays in arbitrary position in the plane. We present an online strategy that achieves a factor of , and give a lower bound of
Lower Bounds for Shoreline Searching With 2 or More Robots
Searching for a line on the plane with unit speed robots is a classic
online problem that dates back to the 50's, and for which competitive ratio
upper bounds are known for every . In this work we improve the best
lower bound known for robots from 1.5993 to 3. Moreover we prove that the
competitive ratio is at least for robots, and at least
for robots. Our lower bounds match the best upper
bounds known for , hence resolving these cases. To the best of our
knowledge, these are the first lower bounds proven for the cases of
this several decades old problem.Comment: This is an updated version of the paper with the same title which
will appear in the proceedings of the 23rd International Conference on
Principles of Distributed Systems (OPODIS 2019) Neuchatel, Switzerland, July
17-19, 201
Recent results from the ANTARES deep sea neutrino telescope
The ANTARES deep sea neutrino telescope has acquired over four years of high
quality data. This data has been used to measure the oscillation parameters of
atmospheric neutrinos and also to search for neutrinos of a non-terrestrial
origin. Competitive upper limits on the fluxes of neutrinos from dark matter
annihilation in the Sun, a variety of Galactic and extra-galactic sources, both
steady and transient, are presented
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