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Course Notes
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Math 846: Algebraic Graph Theory. Spring 2021/2022.
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Math 846 Syllabus Syllabus
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Abbreviations List of Abbreviations
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Lecture 1 W 1/26 Graphs and their spectra; regular graphs; walks and paths
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Lecture 2 F 1/28 Bipartite graphs; the adjacency algebra and dual adjacency algebra; the subconstituent algebra T
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Lecture 3 M 1/31 Irreducible T-modules; T-module isomorphisms; some parameters attached to an irreducible T-module
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Lecture 4 W 2/2 The hypercube and its spectrum
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Lecture 5 F 2/4 The concept of a tridiagonal pair; using a hypercube to construct tridiagonal pairs that are bipartite and dual-bipartite
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Lecture 6 M 2/7 Hermitean and Euclidean spaces; inner product matrices; positive semidefinite matrices; bipartite and reducible matrices
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Lecture 7 W 2/9 The Perron-Frobenius theorem and applications to graphs
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Lecture 8 F 2/11 An eigenvalue bound; distance-regular graphs; the intersection numbers; examples of distance-regular graphs
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Lecture 9 M 2/14 Automorphisms of graphs; distance-transitivity implies distance-regularity; some polynomials attached to a distance-regular graph
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Lecture 10 W 2/16 The intersection matrix; the Norman Biggs multiplicity formula
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Lecture 11 F 2/18 More intersection numbers; some orthogonality relations for polynomials
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Lecture 12 M 2/21 The intersection numbers are determined by the spectrum; the geometry of the eigenspaces; the cosine sequence
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Lecture 13 W 2/23 The representations of a distance-regular graph; the Krawtchouk polynomials
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Lecture 14 F 2/25 The Krein parameters; the dual distance matrices
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Lecture 15 M 2/28 The Krein condition and an application.
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Lecture 16 W 3/2 A geometric interpretation of the Krein parameters; Norton algebras
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Lecture 17 F 3/4 The Q-polynomial property and the dual adjacency matrix; some polynomials attached to the dual adjacency matrix; Askey-Wilson duality
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Lecture 18 M 3/7 A geometric interpretation of the Q-polynomial property
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Lecture 19 W 3/9 The tridiagonal relations
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Lecture 20 F 3/11 Proof of the tridiagonal relations
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Lecture 21 M 3/21 Proof of the tridiagonal relations, cont.
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Lecture 22 W 3/23 The eigenvalues and dual eigenvalues in closed form; the bipartite/dual-bipartite case
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Lecture 23 F 3/25 The bipartite/dual-bipartite case; formulas for the intersection numbers
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Lecture 24 M 3/28 The bipartite/dual bipartite case; the tridiagonal relations in Z3-symmetric form
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Lecture 25 W 3/30 The bipartite/dual bipartite case; type II matrices and spin models
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Lecture 26 F 4/1 The bipartite/dual-bipartite case; the Nomura classification
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Lecture 27 M 4/4 The bipartite/dual-bipartite case; Hadamard matrices and graphs
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Lecture 28 W 4/6 The bipartite/dual-bipartite case; the double cover of the Higman-Sims graph
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Lecture 29 F 4/8 Tridiagonal pairs from a Q-polynomial distance-regular graph; nonisomorphic irreducible T-modules are orthogonal; the primary T-module
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Lecture 30 M 4/11 The primary T-module; reduction rules and bases
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Lecture 31 W 4/13 The concept of a Leonard pair; a Leonard pair on the primary T-module; the Askey-Wilson relations
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Lecture 32 F 4/15 The Askey-Wilson relations attached to the primary T-module
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Lecture 33 M 4/18 Pascasio characterization of the Q-polynomial property
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Lecture 34 W 4/20 Distance-regular graphs with classical parameters
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Lecture 35 F 4/22 Balanced set characterization of the Q-polynomial property
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Lecture 36 M 4/25 The triple intersection numbers
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Lecture 37 W 4/27 Some relations involving the raising, lowering, and flat maps that are implied by the Q-polynomial property; the split decomposition
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Lecture 38 F 4/29 More on the split decomposition; bounds on the endpont and dual endpoint of an irreducible T-module
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Lecture 39 M 5/2 Tridiagonal pairs and tridiagonal systems, the split decomposition of a tridiagonal system
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Lecture 40 W 5/4 The raising and lowering maps with respect to the split decomposition, the tetrahedron diagram, four mutually opposite flags
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Lecture 41 F 5/6 A q-geometric tridiagonal pair gives an
irreducible module for the q-tetrahedron algebra
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Lecture 42 Appendix How the q-tetrahedron algebra is related to Uqsl2hat
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Summary slides Tridiagonal pairs and Uqsl2hat
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Amin Idelhaj Lecture Ramanujan graphs
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Charles Wang Lecture The diameter of bipartite distance-regular graphs
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Yanli Liu Lecture 2-Homogeneous bipartite DRGs Section 3
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Kenneth Ma Lecture 2-Homogeneous bipartite DRGs Section 4
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Karthik Ravishankar Lecture 2-Homogeneous bipartite DRGs Section 5
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Daniel Szabo Lecture 2-Homogeneous bipartite DRGs Section 6
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Jiaming Xu Lecture 2-Homogeneous bipartite DRGs Section 7
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Benjamin Young Lecture 2-Homogeneous bipartite DRGs Section 8
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Yufei Zhan Lecture 2-Homogeneous bipartite DRGs Section 9
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Math 542: Modern Algebra, Spring 2016
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Math 542 Syllabus Syllabus
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Math 542 Homework Homework
(To be updated as we go along)
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Lecture 1, W 1/20
Rings of fractions
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Lecture 2, F 1/22
The field of fractions
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Lecture 3, M 1/25
The Chinese remainder theorem; example
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Lecture 4, W 1/27
The Chinese remainder theorem
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Lecture 5, F 1/29
Euclidean domains
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Lecture 6, M 2/1
Euclidean domains and universal side divisors
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Lecture 7, W 2/3
Principal ideal domains
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Lecture 8, F 2/5
Unique factorization domains
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Lecture 9, M 2/8
A PID is a UFD
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Lecture 10, W 2/10
Primes in the Gaussian integers
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Lecture 11, F 2/12
Expressing an integer as the sum of two squares
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Lecture 12, M 2/15
Polynomial rings
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Lecture 13, W 2/17
The Gauss lemma
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Lecture 14, F 2/19
Irreducibility criteria
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Lecture 15, M 2/22
The Eisenstein irreducibility condition
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Lecture 16, W 2/24
For a finite field the group of units is cyclic
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Lecture 17, F 2/26
The group of units for Z mod N
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Lecture 18, M 2/29
Modules for rings
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Lecture 19, W 3/2
Homomorphisms of R-modules
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Lecture 20, F 3/4
Quotients of R-modules
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Lecture 21, M 3/7
Direct products of R-modules
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Lecture 22, W 3/9
Free R-modules
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Lecture 23, F 3/11
Vector spaces
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Lecture 24, M 3/14
Vector spaces and linear transformations
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Midterm W 3/16
Midterm exam questions
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Midterm Solutions W 3/16
Midterm exam solutions
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Lecture 25, F 3/18
Transition matrices
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Lecture 26, M 3/28
The tensor product of vector spaces
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Lecture 27, W 3/30
The dual of a vector space
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Lecture 28, F 4/1
The transpose of a linear transformation
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Lecture 29, M 4/4
Determinants
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Lecture 30, W 4/6
Properties of the determinant
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Lecture 31, F 4/8
The inverse of a matrix
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Lecture 32, M 4/11
Modules over a PID
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Lecture 33, W 4/13
Torsion modules
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Lecture 34, F 4/15
Rank and torsion
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Lecture 35, M 4/18
Submodules of free modules over a PID
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Lecture 36, W 4/20
Submodules of free modules over a PID, cont.
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Lecture 37, F 4/22
Finitely generated modules over a PID
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Lecture 38, M 4/25
Elementary divisors and invariant factors
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Lecture 39, W 4/27
The rational canonical form
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Lecture 40, F 4/29
The Smith normal form
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Lecture 41, M 5/2
The Jordan canonical form
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Lecture 42, W 5/4
Examples involving the Jordan canonical form
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Lecture 43, F 5/6
Finding the eigenvalues of some tridiagonal matrices using hidden symmetry
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Final Exam, S 5/8
Final exam questions
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Final Exam Solutions, S 5/8
Final exam solutions
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Math 320: Linear Algebra and Differential Equations, Spring 2014.
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Math 320 Syllabus Syllabus
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Lecture 1, W 1/22 Section 1.1
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Lecture 2, F 1/24 Section 1.2
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Lecture 3, M 1/27 Section 1.3
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Lecture 4, W 1/29 Section 1.4
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Lecture 5, F 1/31 Section 1.5
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Lecture 6, M 2/3 Section 2.1
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Lecture 7, W 2/5 Section 2.2
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Lecture 8, F 2/7 Section 2.4
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Lecture 9, M 2/10 Section 3.1
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Lecture 10, W 2/12 Section 3.2
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Lecture 11, F 2/14 Section 3.3
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Lecture 12, M 2/17 Section 3.4
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Lecture 13, W 2/19 Section 3.5
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Lecture 14, F 2/21 Sections 3.5,3.6
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Lecture 15, M 2/24 Section 3.6
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Lecture 16, W 2/26 Section 3.6 (loose ends)
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Lecture 17, M 3/3 Section 4.1
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Lecture 18, W 3/5 Section 4.2
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Lecture 19, F 3/7 Section 4.3
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Lecture 20, M 3/10 Section 4.4
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Lecture 21, W 3/12 Section 4.5
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Lecture 22, F 3/14 Section 4.6
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Lecture 23, M 3/24 Section 4.7
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Lecture 24, W 3/26 Section 5.1
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Lecture 25, F 3/28 Section 5.2
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Lecture 26, M 3/31 Section 5.3
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Lecture 27, W 4/2 Section 5.5
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Lecture 28, F 4/4 Section 6.1
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Lecture 29, M 4/7 Section 6.2
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Lecture 30, W 4/9 Section 6.3
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Lecture 31, F 4/11 Section 6.3 (loose ends)
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Lecture 32, W 4/16 Section 7.1
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Lecture 33, F 4/18 Section 7.2
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Lecture 34, M 4/21 Section 7.3
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Lecture 35, W 4/23 Section 7.5
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Lecture 36, F 4/25 Section 7.5 (continued)
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Lecture 37, M 4/28 Section 8.1
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Lecture 38, W 4/30 Section 8.1 (continued)
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Lecture 39, F 5/2 Section 8.2
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Lecture 40, M 5/5 Section 8.2 (continued)
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Lecture 41, W 5/7 Section 8.3
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Lecture 42, F 5/9 Section 8.3 (continued)
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Math 210: What follows is a list of Math 210 Homework solutions.
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Math 210 syllabus for Fall 2012
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Typos contains a list of typos in
the text "Finite Mathematics" 5th Edition, by Maki and Thompson.
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Section 1.1 HW solutions
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Section 1.2 HW solutions
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Section 1.3 HW solutions
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Section 1.4 HW solutions
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Section 1.R HW solutions
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Section 2.1 HW solutions
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Section 2.2 HW solutions
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Section 2.3 HW solutions
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Section 2.4 HW solutions
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Section 2.R HW solutions
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Section 3.1 HW solutions
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Section 3.2 HW solutions
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Section 3.3 HW solutions
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Section 3.4 HW solutions
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Section 3.5 HW solutions
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Section 3.R HW solutions
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Section 4.1 HW solutions
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Section 4.2 HW solutions
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Section 4.R HW solutions
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Section 5.1 HW solutions
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Section 5.2 HW solutions
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Section 5.3 HW solutions
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Section 5.R HW solutions
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Section 6.1 HW solutions
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Section 6.2 HW solutions
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Section 6.R HW solutions
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Section 7.1 HW solutions
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Section 7.2 HW solutions
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Section 7.3 HW solutions
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Section 7.R HW solutions
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Section 8.1 HW solutions
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Section 8.2 HW solutions
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Section 8.3 HW solutions
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Section 8.R HW solutions
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Section 9.1 HW solutions
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Section 9.2 HW solutions
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Section 9.3 HW solutions
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Some of my recent talks are given below.
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ndpt.pdf
The nucleus of a Q-polynomial distance-regular graph
(50 minutes)
terwilliCMS2024.pdf
The S3-symmetric tridiagonal algebra
(20 minutes)
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terwilMilw2024.pdf
The Norton-balanced condition for Q-polynomial distance-regular graphs
(20 minutes)
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tatt.pdf
Generalizing the Q-polynomial property to graphs that are not distance-regular
(50 minutes)
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spt.pdf
Spin models and distance-regular graphs of q-Racah type
(50 minutes)
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terwillBled2023.pdf
The Z3-symmetric down-up algebra
(20 minutes)
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talkMilw2023.pdf
The q-Shuffle algebra, the alternating elements, and the positive part of quantum affine sl2
(45 minutes)
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slcTerwilliger.pdf
A Q-polynomial structure associated with the projective geometry LN(q) (25 minutes)
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terAltTDDRG.pdf
Tridiagonal pairs, alternating elements, and distance-regular graphs (50 minutes)
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noncom.pdf
Tridiagonal pairs and the quantum affine sl2 algebra (50 minutes)
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cclp.pdf
Compatibility and companions for Leonard pairs (50 minutes)
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ta.pdf
The alternating central extension of the q-Onsager algebra (50 minutes)
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talkField2021.pdf
Q-polynomial distance-regular graphs and the positive part of the quantum affine sl2 algebra (45 minutes)
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sl.pdf
Leonard pairs, spin models, and distance-regular graphs (60 minutes)
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acext.pdf
The alternating central extension for the positive part of
the quantum affine sl2 algebra
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spinBled2019.pdf
Leonard pairs, spin models, and distance-regular graphs (20 minutes)
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terwilli2019.pdf
The alternating PBW basis for the positive part of the quantum affine sl2
algebra
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catalan2018.pdf
Catalan words and q-shuffle algebras
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infdim.pdf
An infinite-dimensional Square_q module obtained from the q-shuffle algebra
for affine sl2
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lusztigAutTalk2018.pdf
The Lusztig automorphisms of the q-Onsager algebra
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tdpairs2018.pdf
Tridiagonal pairs and applications
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tbtdpair.pdf
Totally bipartite tridiagonal pairs
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eltalk.pdf
Tridiagonal pairs of q-Racah type, the Bockting operator, and L-operators
for Uq(L(sl2))
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www2016.pdf
Leonard triples of q-Racah type; Combinatorics seminar talk Fall 2016
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lrtriple60min.pdf
Lowering-Raising triples and Uq(sl2); Colloquium talk at DePaul U. 2016
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skeinUAW2015.pdf
Topological aspects of the Z3-symmetric Askey-Wilson relations
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lrtTalk2014.pdf
Lowering-Raising triples and Uq(sl2)
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billiard.pdf
Billiard Arrays and finite-dimensional irreducible Uqsl2-modules
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tdpInAlgGrTh.pdf
Tridiagonal pairs in Algebraic Graph Theory
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lpAndQtet.pdf
Leonard pairs and the q-tetrahedron algebra
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univAWalgebra.pdf
The universal Askey-Wilson algebra
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classTDpair.pdf
A classification of sharp tridiagonal pairs
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rahmanSl3.pdf
The Rahman polynomials and the Lie algebra sl3
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The pdf file for the following paper is given below.
P. Terwilliger. The incidence algebra of a uniform poset.
Coding theory and design theory Part I. 193--212 IMA Vol. Math.
Appl. 20 Springer New York, 1990.
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uniformposet.pdf
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The pdf file for the following paper is given below.
P. Terwilliger. Leonard pairs and dual polynomial sequences.
The paper was submitted to LAA on May 15, 1987, but never published.
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leonardpair.pdf
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The pdf file for the following paper is given below.
Counting 4-vertex configurations in P and Q polynomial association schemes.
Algebras, Groups, and Geometries 2 (1985) 541--554.
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counting4vertex.pdf
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The following contains the course notes from Math 846 Algebraic Graph Theory,
Spring term 2009.
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Part 1 846 notes
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Part 2 846 notes
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Part 3 846 notes
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Part 4 846 notes
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Part 5 846 notes
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Part 6 846 notes