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 > Putnam Math Competition
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Carolyn Nguyen and Anna Oliva

University of Houston and Carnegie Vanguard HS



Evasion Paths in Hyperbolic Sensor Networks
and
Symmetry, Fixed Points, and Quantum Billiards: A Confluence of Ideas



April 18, 2024
4:00pm    PGH 646



Abstract
 

Carolyn Nguyen: In this talk we focus on how to effectively monitor a domain with a network of mobile sensors in a coordinate free way. We equip these mobile sensors with minimal sensing ability; they do not track their absolute positions in space (i.e. no GPS data), but do know the identities and cyclic ordering of nearby sensors and can sense evaders within a relatively small ball of given radius. Minimal mobile sensing problems have received considerable attention over the past 15 years. This field is part of applied topology, an emerging research area that links theoretical concepts in topology to applied problems in data analysis. Potential applications of our work include scanning a region to detect forest fires, radiological or biological hazards, hidden mines, or a specific individual in a crowd. Our talk will evaluate the effectiveness of mobile sensor networks by studying how long an evader can remain undetected. In particular, we are interested in how the hyperbolicity of the collective sensor motion affects this detection time. We will present results in which we introduce hyperbolicity through the boundary geometry using the Bunimovich stadium.

Anna Oliva: A mathematical billiard system is one composed of a planar or multidimensional surface and a moving object whose trajectory is defined by its initial position and speed vector, along with some reflection law. The study of these systems has yielded applications in quantum computing and physical modeling. The purpose of this research was to study a novel reflection law for billiard systems of regular n-gons in which an object starting on one of the sides and moving with any given slope reflects from a limited reflection towards the interior with a prescribed constant angle. We constructed the map for the position of such an object as a function of the starting point and the slope in the case of a regular triangle and square. For the case of the square we proved that the object’s path converges to a stable inner rectangle for all initial conditions and all slopes. We showed that the same results is true for a triangular billiard if the starting slope is less than 60 degrees. Otherwise, we showed that for starting slopes between 60 and 90 there exists only a countable set of starting points which lead to convergent trajectory. We have also constructed a numerical model for the object’s trajectory and determined equations yielding the speed of the object’s convergence to a stable path. We have performed relevant simulations and discussed the resulting data in the context of the proposed model. The analysis of these systems can be used to develop independent control mechanisms for ground robots in delivery missions working within contested environments or simpler and smaller microchips in the form of quantum billiards with correlated electrons without the necessity of perfectly elastic collisions, offering an innovative way to encode information.

Pizza will be served.

Colloquium sponsored by the NSM Dean's office DUSEM grant

[click for poster]






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