Packing in Discrete Domains - Geometry and Analysis
The packing problem associated with a family of sets F seeks a large subfamily of pairwise disjoint members of F. When F comprises the unit balls in d-space, this is the sphere packing problem, which for d = 3 was solved by Hales-...
The packing problem associated with a family of sets F seeks a large subfamily of pairwise disjoint members of F. When F comprises the unit balls in d-space, this is the sphere packing problem, which for d = 3 was solved by Hales-Ferguson (Kepler’s conjecture). The cases d = 8, 24 have won Viazovska her Fields Medal. Much of discrete mathematics deals with dense packing problems. The asymptotic rate vs. distance problem, may be the most fundamental open problem about error correcting codes. It seeks the densest Hamming-sphere packing in discrete cubes. A linear code is a linear subspace of F_2n. Such codes are important both in theory and in practice. Here, we seek to maximize dim(C), when every nonzero vector in C has Hamming weight ≥ δn. Despite its mathematical significance and practical importance, the answer remains unknown for all 1/2 > δ > 0, and our best upper bounds on the rate date from the 70’s. Neither do we know if linear codes can be asymptotically as good as general codes. We have made some progress on these key questions of our proposal. The infinite d-regular tree Td is another important metric space where we seek dense sphere packing. It is easy to perfectly pack balls in Td, but not in a periodic manner. Periodic perfect sphere packings in Td coincide with Moore graphs - finite regular graphs of least diameter and largest possible girth (i.e., with no short cycles). Moore graphs were fully characterized in the 70’s, yet we still cannot show that for fixed d ≥ 3 and large r, any periodic packing of r-spheres in Td must have vanishing density. Many important mathematicians, including Erdös, Margulis, and Lubotzky-Phillips-Sarnak sought the largest possible girth of a d-regular n-vertex graph (d fixed, n → ∞). We show how better upper bounds on linear codes yield progress here, whereas bounds on general codes would not do.We use computers as exploratory tools, e.g., to test our new bounds on codes, yet we publish only humanly verifiable proofs.ver más
Seleccionando "Aceptar todas las cookies" acepta el uso de cookies para ayudarnos a brindarle una mejor experiencia de usuario y para analizar el uso del sitio web. Al hacer clic en "Ajustar tus preferencias" puede elegir qué cookies permitir. Solo las cookies esenciales son necesarias para el correcto funcionamiento de nuestro sitio web y no se pueden rechazar.
Cookie settings
Nuestro sitio web almacena cuatro tipos de cookies. En cualquier momento puede elegir qué cookies acepta y cuáles rechaza. Puede obtener más información sobre qué son las cookies y qué tipos de cookies almacenamos en nuestra Política de cookies.
Son necesarias por razones técnicas. Sin ellas, este sitio web podría no funcionar correctamente.
Son necesarias para una funcionalidad específica en el sitio web. Sin ellos, algunas características pueden estar deshabilitadas.
Nos permite analizar el uso del sitio web y mejorar la experiencia del visitante.
Nos permite personalizar su experiencia y enviarle contenido y ofertas relevantes, en este sitio web y en otros sitios web.