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New Results for 2D Tilings : Wiener Index & Statistical Mechanics of Graphs

New Results for 2D Tilings : Wiener Index & Statistical Mechanics of Graphs ArizMATYC & MAA Southwestern Section Scottsdale, AZ April 9-10, 2010. Forrest H Kaatz Maricopa Community Colleges, AZ University of Advancing Technology, Tempe, AZ Adhemar Bultheel

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New Results for 2D Tilings : Wiener Index & Statistical Mechanics of Graphs

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  1. New Results for 2D Tilings: Wiener Index & Statistical Mechanics of Graphs ArizMATYC & MAA Southwestern Section Scottsdale, AZ April 9-10, 2010

  2. Forrest H Kaatz Maricopa Community Colleges, AZ University of Advancing Technology, Tempe, AZ AdhemarBultheel Department of Computer Science K.U.Leuven, Celestijnenlaan 200A, 3001 Heverlee, Belgium Andrej Vodopivec Department of Mathematics IMFM, 1000 Ljubljana, Slovenia Ernesto Estrada Institute of Complexity Science Department of Physics and Department of Mathematics University of Strathclyde, Glasgow G1 1XH, United Kingdom

  3. Periodic and Non-periodic Tilings

  4. Archimedean Lattices - Tiling in the Plane

  5. Regular Tilings Triangles Squares Hexagons Random

  6. Methods Image SXM determines array coordinates Excel macros for distances (adjacency matrix) Maxima used for distance matrices, Wiener Index, and eigenvalues MATLAB used for graphing and statistical mechanics

  7. Adjacency Matrix Euclidean adjacency matrix:

  8. Adjacency Matrices

  9. Statistical Mechanics of Graphs The partition function is defined as: where the Hamiltonian H = -AandA is the adjacency matrix, G is a graph, and ß= 1 for an unweighted network

  10. Statistical Mechanics of Graphs, cont’d The probability that the system will occupy the jth microstate is given by: where is an eigenvalue of the adjacency matrix We can then define the thermodynamic functions as follows:

  11. Statistical Mechanics of Graphs, cont’d The (Shannon) entropy is : which can be rearranged as: The energy relationships are then:

  12. Statistical Mechanics of Graphs, cont’d The total energy can be written as: and the Helmholtz free energy is:

  13. Hexagonal Arrays 10 Coordinates 11 Links 1000 Coordinates 1446 Links

  14. Statistical Mechanics Results Partition Function and Enthalpy

  15. Results, cont’d Entropy and Free Energy

  16. Power Laws If a relationship has a power fit A log-log plot produces a straight line, slope k

  17. Summary Wiener Index used to model real 2D tilings, i.e. porous arrays Porous arrays are increasing (expanding) in size Distributions of normalized link length determined Statistical mechanics functions are fit with power regression Work to be Done Still need a model for the thermodynamic behavior of graphs

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