VisualMath

Mathematics, with pictures and fewer secret handshakes

VisualMath is my YouTube channel for lectures, public explanations, mini-courses and mathematical side quests.

The channel ranges from Lie theory, quantum topology and representation theory to machine learning, favorite theorems, computer algebra and public-facing mathematical explanations.

For laypersons. Many mathematical ideas become less intimidating once one sees the right picture. The videos are meant to provide that first picture, not to replace the proof.

Lecture series

Long-form playlists such as Lie theory, quantum topology and machine learning in mathematics.

Public explanations

Shorter videos on favorite fields, favorite theorems and mathematical ideas with pictures.

Slides included

Most videos link to slides, so the page doubles as a searchable archive.

Channel URL

Click here: VisualMath

Disclaimer

Nobody is perfect, and I might have said something silly. If there is any doubt, then please check the references or other sources. Moreover, after upload I am not able to change the YouTube videos anymore, so take everything with a pinch of salt. I can change the slides, so let me know if you have spotted any typos. In any case, here is a list all my YouTube videos, including slides. The order below is by playlist, newest first:

  • Lie theory
  • AI for the working mathematician
  • What is...quantum topology?
  • What is...machine learning in mathematics?
  • What are...my favorite subfields (of mathematics)?
  • What are...my favorite theorems?
  • What is...tropical geometry?
  • What is...algebraic geometry?
  • Magma in a nutshell
  • What is...algebraic graph theory?
  • What is...geometric topology?
  • What is...representation theory?
  • What is...category theory?
  • What is...algebraic topology?
  • What is...algebra?
  • What is...linear algebra?
  • For my talks see here, for quantum topology see here, for Soergel bimodules see here
If there is something missing you would like to see (e.g. I forgot to upload slides, or you are missing a topic covered in a video, or there is a dead link, or...) then reach out: daniel.tubbenhauer@sydney.edu.au

TeX files

The TeX files for the presentations are freely available at: https://github.com/dtubbenhauer/My-TeX-files.git

A list of my videos

  • Playlist Lie theory
    1. Topic: Lie theory, part 20? - Characters as fingerprints. Slides
    2. Topic: Lie theory, part 19? - Peter–Weyl in 10 minutes. Slides
    3. Topic: Lie theory, part 18? - Compact groups and complete reducibility. Slides
    4. Topic: Lie theory, part 17? - Simple vs reducible. Slides
    5. Topic: Lie theory, part 16? - Representations of Lie algebras. Slides
    6. Topic: Lie theory, part 15? - Representations of Lie groups: first principles. Slides
    7. Topic: Lie theory, part 14? - Adjoint action: Ad and ad. Slides
    8. Topic: Lie theory, part 13? - Classification of simple Lie algebras in a nutshell. Slides
    9. Topic: Lie theory, part 12? - The center, derived algebra, and simple vs solvable. Slides
    10. Topic: Lie theory, part 11? - Baker–Campbell–Hausdorff. Slides
    11. Topic: Lie theory, part 10? - The exponential map in more details. Slides
    12. Topic: Lie theory, part 9? - Ideals and quotient Lie algebras. Slides
    13. Topic: Lie theory, part 8? - Homomorphisms and subalgebras. Slides
    14. Topic: Lie theory, part 7? - Lie brackets. Slides
    15. Topic: Lie theory, part 6? - Lie algebras. Slides
    16. Topic: Lie theory, part 5? - One-parameter subgroups and flows. Slides
    17. Topic: Lie theory, part 4? - Topology + smoothness. Slides
    18. Topic: Lie theory, part 3? - Matrix groups. Slides
    19. Topic: Lie theory, part 2? - Where do Lie groups come from? Slides
    20. Topic: Lie theory, part 1? - Introduction. Slides
  • Playlist AI for the working mathematician
    1. Topic: AI for the working mathematician, part 6? - What is...reproducibility with AI? Slides
    2. Topic: AI for the working mathematician, part 5? - What is...writing with AI? Slides
    3. Topic: AI for the working mathematician, part 4? - What is...reading with AI? Slides
    4. Topic: AI for the working mathematician, part 3? - What is...coding with AI? Slides
    5. Topic: AI for the working mathematician, part 2? - What is...proving with AI? Slides
    6. Topic: AI for the working mathematician, part 1? - Introduction. Slides
  • Playlist What is...quantum topology?
    1. Topic: What is...quantum topology - part 29? - Additive categories 2 from Chapter 6. Slides
    2. Topic: What is...quantum topology - part 28? - Additive categories 1 from Chapter 6. Slides
    3. Topic: What is...quantum topology - part 27? - Braided categories 6 from Chapter 5. Slides
    4. Topic: What is...quantum topology - part 26? - Braided categories 5 from Chapter 5. Slides
    5. Topic: What is...quantum topology - part 25? - Braided categories 4 from Chapter 5. Slides
    6. Topic: What is...quantum topology - part 24? - Braided categories 3 from Chapter 5. Slides
    7. Topic: What is...quantum topology - part 23? - Braided categories 2 from Chapter 5. Slides
    8. Topic: What is...quantum topology - part 22? - Braided categories 1 from Chapter 5. Slides
    9. Topic: What is...quantum topology - part 21? - Pivotal categories 3 from Chapter 4. Slides
    10. Topic: What is...quantum topology - part 20? - Pivotal categories 2 from Chapter 4. Slides
    11. Topic: What is...quantum topology - part 19? - Pivotal categories 1 from Chapter 4. Slides
    12. Topic: What is...quantum topology - part 18? - Monoidal categories 6 from Chapter 3. Slides
    13. Topic: What is...quantum topology - part 17? - Monoidal categories 5 from Chapter 3. Slides
    14. Topic: What is...quantum topology - part 16? - Monoidal categories 4 from Chapter 2. Slides
    15. Topic: What is...quantum topology - part 15? - Monoidal categories 3 from Chapter 2. Slides
    16. Topic: What is...quantum topology - part 14? - Monoidal categories 2 from Chapter 2. Slides
    17. Topic: What is...quantum topology - part 13? - Monoidal categories 1 from Chapter 2. Slides
    18. Topic: What is...quantum topology - part 12? - Categories 10 from Chapter 1. Slides
    19. Topic: What is...quantum topology - part 11? - Categories 9 from Chapter 1. Slides
    20. Topic: What is...quantum topology - part 10? - Categories 8 from Chapter 1. Slides
    21. Topic: What is...quantum topology - part 9? - Categories 7 from Chapter 1. Slides
    22. Topic: What is...quantum topology - part 8? - Categories 6 from Chapter 1. Slides
    23. Topic: What is...quantum topology - part 7? - Categories 5 from Chapter 1. Slides
    24. Topic: What is...quantum topology - part 6? - Categories 4 from Chapter 1. Slides
    25. Topic: What is...quantum topology - part 5? - Categories 3 from Chapter 1. Slides
    26. Topic: What is...quantum topology - part 4? - Categories 2 from Chapter 1. Slides
    27. Topic: What is...quantum topology - part 3? - Categories 1 from Chapter 1. Slides
    28. Topic: What is...quantum topology - part 2? - The Jones polynomial. Slides
    29. Topic: What is...quantum topology - part 1? - Introduction. Slides
  • Playlist What is...machine learning in mathematics?
    1. Topic: What is...machine learning in mathematics - part 13? - Grading math with AI!? Slides
    2. Topic: What is...machine learning in mathematics - part 12? - AI and symbolic mathematics. Slides
    3. Topic: What is...machine learning in mathematics - part 11? - How to ask good questions!? Slides
    4. Topic: What is...machine learning in mathematics - part 10? - Pattern detection. Slides
    5. Topic: What is...machine learning in mathematics - part 9? - Example creation. Slides
    6. Topic: What is...machine learning in mathematics - part 8? - Property predictions. Slides
    7. Topic: What is...machine learning in mathematics - part 7? - Anti-conjecturing. Slides
    8. Topic: What is...machine learning in mathematics - part 6? - Approximating hard problems. Slides
    9. Topic: What is...machine learning in mathematics - part 5? - Formula guessing. Slides
    10. Topic: What is...machine learning in mathematics - part 4? - AI and automated proofs. Slides
    11. Topic: What is...machine learning in mathematics - part 3? - Translate, please. Slides
    12. Topic: What is...machine learning in mathematics - part 2? - AI and matrix multiplication. Slides
    13. Topic: What is...machine learning in mathematics - part 1? - Introduction. Slides
  • Playlist What are...my favorite subfields?
    1. Topic: What is...computational science? - Subfields of mathematics 35. Slides
    2. Topic: What is...the theory of algorithms? - Subfields of mathematics 34. Slides
    3. Topic: What is...iterative mathematics? - Subfields of mathematics 33. Slides
    4. Topic: What is...numerical dynamics? - Subfields of mathematics 32. Slides
    5. Topic: What is...discrete analysis? - Subfields of mathematics 31. Slides
    6. Topic: What is...algorithmic number theory? - Subfields of mathematics 30. Slides
    7. Topic: What is...randomized mathematics? - Subfields of mathematics 29. Slides
    8. Topic: What is...linear programming? - Subfields of mathematics 28. Slides
    9. Topic: What is...numerical linear algebra? - Subfields of mathematics 27. Slides
    10. Topic: What is...Lie theory? - Subfields of mathematics 26. Slides
    11. Topic: What is...group-based cryptography? - Subfields of mathematics 25. Slides
    12. Topic: What is...automated mathematics? - Subfields of mathematics 24. Slides
    13. Topic: What is...matroid theory? - Subfields of mathematics 23. Slides
    14. Topic: What is...discrete geometry? - Subfields of mathematics 22. Slides
    15. Topic: What is...quantum algebra? - Subfields of mathematics 21. Slides
    16. Topic: What is...game theory? - Subfields of mathematics 20. Slides
    17. Topic: What is...complexity theory? - Subfields of mathematics 19. Slides
    18. Topic: What is...invariant theory? - Subfields of mathematics 18. Slides
    19. Topic: What is...diagrammatic algebra? - Subfields of mathematics 17. Slides
    20. Topic: What is...quantum topology? - Subfields of mathematics 16. Slides
    21. Topic: What is...computer algebra? - Subfields of mathematics 15. Slides
    22. Topic: What is...mathematical biology? - Subfields of mathematics 14. Slides
    23. Topic: What is...order theory? - Subfields of mathematics 13. Slides
    24. Topic: What is...geometric group theory? - Subfields of mathematics 12. Slides
    25. Topic: What is...tropical geometry? - Subfields of mathematics 11. Slides
    26. Topic: What is...computer aided mathematics? - Subfields of mathematics 10. Slides
    27. Topic: What is...symbolic dynamics? - Subfields of mathematics 9. Slides
    28. Topic: What is...experimental mathematics? - Subfields of mathematics 8. Slides
    29. Topic: What is...analytic combinatorics? - Subfields of mathematics 7. Slides
    30. Topic: What is...computational topology? - Subfields of mathematics 6. Slides
    31. Topic: What is...random graph theory? - Subfields of mathematics 5. Slides
    32. Topic: What is...analytic number theory? - Subfields of mathematics 4. Slides
    33. Topic: What is...topological data analysis? - Subfields of mathematics 3. Slides
    34. Topic: What is...additive combinatorics? - Subfields of mathematics 2. Slides
    35. Topic: What is...extremal graph theory? - Subfields of mathematics 1. Slides
  • Playlist What are...my favorite theorems?
    1. Topic: What is...the Cantor sequence? - 101000101... Slides
    2. Topic: What are...intrinsically linked graphs? - Difficult problem, easy solution. Slides
    3. Topic: What is...the Riemann–Roch theorem? - Allowing poles. Slides
    4. Topic: What is...an inverse fractal? - Zooming out. Slides
    5. Topic: What is...a fractal? - Zooming in. Slides
    6. Topic: What are...nearest neighbors? - Close friends. Slides
    7. Topic: What is...hyperplane separation? - Cutting data into bits. Slides
    8. Topic: What is...a coin toss run? - Why is this difficult? Slides
    9. Topic: What is...the drunken bird constant? - Coming home, or not...? Slides
    10. Topic: What is...the else function? - Counting else. Slides
    11. Topic: What are...multiplicative compositions? - Additive < multiplicative. Slides
    12. Topic: What is...Golomb–Dickman's constant? - Cycles and primes. Slides
    13. Topic: What is...counting of abelian groups? - Commutative = easy. Slides
    14. Topic: What is...the tree constant? - Trees are difficult. Slides
    15. Topic: What is...tree counting? - n+1 and n-1. Slides
    16. Topic: What is...the Cayley–Bacharach theorem? - Nine and nine! Slides
    17. Topic: What is...Nagata's theorem? - Ill-behaved invariants. Slides
    18. Topic: What are...Dehn invariants? - Cutting polyhedra. Slides
    19. Topic: What is...the Gelfond–Schneider? - Logarithms and transcendence. Slides
    20. Topic: What are...Mahler functions? - Self-similarity and transcendence. Slides
    21. Topic: What is...Hilbert's Satz 90? - Number 90 is it! Slides
    22. Topic: What is...the Yang–Mills mass gap? - One comes after zero. Slides
    23. Topic: What is...the Hodge conjecture? - Topology and algebraic geometry. Slides
    24. Topic: What are...the Navier–Stokes equations? - Fluids are difficult. Slides
    25. Topic: What is...the Birch–Swinnerton-Dyer conjecture? - Counting, of course. Slides
    26. Topic: What is...the 3d Poincaré conjecture? - Its a sphere? Its a sphere! Slides
    27. Topic: What is...the Riemann hypothesis? - Critical strip free (almost). Slides
    28. Topic: What are...crystal graphs? - Low temperature behavior. Slides
    29. Topic: What is...Freudenthal's magic square? - Exceptional! Slides
    30. Topic: What are...octonions? - Or: Division = good, associativity = bad. Slides
    31. Topic: What is...planarity testing? - Or: Finding planar embeddings. Slides
    32. Topic: What are...Borcherds–Kac–Moody algebras? - Or: Still emerging from matrices. Slides
    33. Topic: What are...sporadic groups? - Or: Weird, but interesting. Slides
    34. Topic: What are...Kac–Moody algebras? - Or: Emerging from matrices. Slides
    35. Topic: What is...the complexity of embeddings? - Or: How difficult is drawing? Slides
    36. Topic: What are...Hecke algebras? - Or: Counting, or rather not counting?! Slides
    37. Topic: What is...the Bruhat decomposition? - Or: Lower and upper. Slides
    38. Topic: What is...recurrent versus transient? - Or: Leaving or staying. Slides
    39. Topic: What are...tree rotations? - Or: A surprisingly small bound. Slides
    40. Topic: What are...IBIS groups? - Or: Perfectly broken symmetries. Slides
    41. Topic: What are...Coxeter complexes? - Or: Spheres and points. Slides
    42. Topic: What is...the partition number? - Or: To count or not to count... Slides
    43. Topic: What are...Kronecker coefficients? - Or: Terribly difficult. Slides
    44. Topic: What is...a Hopf algebra? - Or: Why we comultiply. Slides
    45. Topic: What is...Padé approximation? - Or: Better than Taylor. Slides
    46. Topic: What are...the groups of Galois theory? - Or: An ocean of symmetric groups. Slides
    47. Topic: What is...Bass-Serre theory? - Or: Trees and groups. Slides
    48. Topic: What are...computer conjectures? - Or: A computer can write poems, so... Slides
    49. Topic: What are...computer proofs? - Or: Who needs mathematicians? Slides
    50. Topic: What is...homotopy type theory? - Or: HoTT = Ho + TT. Slides
    51. Topic: What is...the prime number theorem? - Or: Let us not count! Slides
    52. Topic: What is...the balanced graph theorem? - Or: Sudden appearance. Slides
    53. Topic: What is...the matrix equivalence theorem? - Or: One is ok. Two is, well... Three is impossible. Slides
    54. Topic: What is...Drozd's theorem? - Or: The Jordan normal form doesn't get better... Slides
    55. Topic: What is...Artin-Wedderburn's theorem? - Or: Matrices, of course. Slides
    56. Topic: What is...convolution? - Or: Area, even without area. Slides
    57. Topic: What is...symbolic integration? - Or: Symbolic integration rules! Slides
    58. Topic: What is...Karatsuba's algorithm? - Or: Faster than expected. Slides
    59. Topic: What are...alpha shapes and complexes? - Or: Topology and its applications. Slides
    60. Topic: What are...Frobenius algebras and 2d TQFTs? - Or: Physics and math walk hand in hand. Slides
    61. Topic: What is...Fagin's theorem? - Or: Almost always true, almost always false. Slides
    62. Topic: What is...the Novikov-Boone-Britton theorem? - Or: Sometimes life is not decidable. Slides
    63. Topic: What are...expander graphs? - Or: Sparse and connected. Slides
    64. Topic: What is...Stone's duality? - Or: Graphs and logic. Slides
    65. Topic: What is...Kasteleyn's theorem? - Or: Difficult, yet easy. Slides
    66. Topic: What is...the commuting matrix theorem? - Or: Around 25%. Slides
    67. Topic: What is...the Garden of Eden theorem? - Or: Ignored by life? Slides
    68. Topic: What is...the Ax-Grothendieck theorem? - Or: Polynomials rule! Slides
    69. Topic: What is...the choice zoo? - Or: No general choice, please! Slides
    70. Topic: What is...a Hadamard matrix? - Or: Orthogonality exists! Or not? Slides
    71. Topic: What are...independence results? - Or: Its true and its not true. Slides
    72. Topic: What are...skein relations? - Or: Life knows somehow... Slides
    73. Topic: What are...Riemann surfaces? - Or: Avoid choices! Slides
    74. Topic: What is...counting of Tait colorings? - Or: Evaluating graphs. Slides
    75. Topic: What is...a Tait coloring? - Or: Towards the four color theorem. Slides
    76. Topic: What is...the Rado graph? - Or: The law of large numbers for graphs. Slides
    77. Topic: What is...the LKB representation? - Or: Braids are linear. Slides
    78. Topic: What is...Dirac's belt trick? - Or: 720 degree is it! Slides
    79. Topic: What is...Fortune's algorithm? - Or: Parabolas and distance. Slides
    80. Topic: What is...the genus of a graph? - Or: Building bridges. Slides
    81. Topic: What is...the infinitude of prime knots? - Or: Euclid’s theorem for knots. Slides
    82. Topic: What are...torus knots? - Or: Wind p times, wind q times. Slides
    83. Topic: What is...Fáry's theorem? - Or: Straight lines everywhere. Slides
    84. Topic: What is...the circle packing theorem? - Or: From circles to graphs and back. Slides
    85. Topic: What is...exotic four space? - Or: Dimension four is weird!? Slides
    86. Topic: What is...homotopy of spheres? - Or: Surprisingly hard!? Slides
    87. Topic: What is...Hamming distance? - Or: Cubes! Slides
    88. Topic: What is...the jeu de taquin? - Or: Teasing permutations. Slides
    89. Topic: What is...coloring of numbers? - Or: From colors to set theory. Slides
    90. Topic: What is...the dimension of a graph? - Or: 1d objects can be high dimensional? Slides
    91. Topic: What is...crossing number additivity? - Or: Adding crossings adds crossings? Slides
    92. Topic: What is...the Erdős–Gabbai theorem? - Or: Realizing graphs. Slides
    93. Topic: What is...\((236c)^{11}\)? - Or: That is a polynomial in c! Slides
    94. Topic: What is...Whitney's embedding theorem? - Or: Projective spaces are nasty. Slides
    95. Topic: What is...the square ice constant? - Or: Ice and 1.539601... Slides
    96. Topic: What is...Bondy's theorem? - Or: Forgetting without loss. Slides
    97. Topic: What is...P versus NP? - Or: Building a chair versus recognizing it. Slides
    98. Topic: What is...a pointwise coloring of the plane? - Or: The chromatic number of the plane. Slides
    99. Topic: What is...Hadwiger's conjecture? - Or: Coloring is difficult... Slides
    100. Topic: What is...group growth? - Or: Small, medium-sized and big groups? Slides
    101. Topic: What is...a limit line graph? - Or: Line graphs converge; in some sense... Slides
    102. Topic: What is...card shuffling mathematically? - Or: Random walks. Slides
    103. Topic: What are...zeta functions of languages? - Or: Counting voodoo. Slides
    104. Topic: What is...a demon knot? - Or: Why wireless is great. Slides
    105. Topic: What are...diagram algebras? - Or: Pictures in algebra and algebra in pictures. Slides
    106. Topic: What are...spectra of Cayley graphs? - Or: Eigenvalues and characters. Slides
    107. Topic: What is...Kronecker's theorem? - Or: Darts and polynomials. Slides
    108. Topic: What is...the Robinson-Schensted correspondence? - Or: Boxes and permutations. Slides
    109. Topic: What is...a greedy algorithm? - Or: Greed is good! Well... Slides
    110. Topic: What is...the BEST theorem? - Or: de [B]ruijn, van Aardenne-[E]hrenfest, [S]mith, [T]utte. Slides
    111. Topic: What are...set partitions? - Or: Prototypical lattices!? Slides
    112. Topic: What is...Frucht's theorem? - Or: Graphs and symmetries. Slides
    113. Topic: What are...randomized algorithms? - Or: Randomness rocks! Slides
    114. Topic: What is...the Gauss-Bonnet theorem? - Or: Curvature and Euler. Slides
    115. Topic: What are...prime knots? - Or: The prime numbers of knot theory!? Slides
    116. Topic: What are...operads? - Or: Topological algebra. Slides
    117. Topic: What is...Maschke's theorem? - Or: Blocks out of the blue. Slides
    118. Topic: What is...Kazhdan-Lusztig combinatorics? - Or: It is nonnegative!? Slides
    119. Topic: What is...a Voronoi diagram? - Or: Distance diagrammatically. Slides
    120. Topic: What is...the Tutte polynomial? - Or: Counting using polynomials. Slides
    121. Topic: What is...a Seifert surface? - Or: Soap and knots. Slides
    122. Topic: What is...sphere packing? - Or: Honeycombs in higher dimensions. Slides
    123. Topic: What is...Kolmogorov complexity? - Or: Shakespeare's work is not random. Slides
    124. Topic: What is...the gnu function? - Or: Symmetries are wild. Slides
    125. Topic: What is...a tropical curve? - Or: Straight curves. Slides
    126. Topic: What is...Bézout's theorem? - Or: Counting intersections. Slides
    127. Topic: What is...fuzzy logic? - Or: This video is 90% crap. Slides
    128. Topic: What is...the Gauss-Wantzel theorem? - Or: Why 65537? Slides
    129. Topic: What is...the small-world effect? - Or: Everyone knows everyone!? Slides
    130. Topic: What are...hyperbolic groups? - Or: From groups to Cantor sets. Slides
    131. Topic: What are...the three geometries? - Or: 0, 1 and \(\infty\). Slides
    132. Topic: What are...Chaitin's constants? - Or: Computing a glimpse of randomness. Slides
    133. Topic: What is...a coherence theorem? - Or: Don't underestimate associativity. Slides
    134. Topic: What is...Diffie-Hellman key exchange? - Or: How not to transfer the encryption key. Slides
    135. Topic: What are...Ramsey numbers? - Or: Counting made difficult. Slides
    136. Topic: What is...the Gessel-Viennot lemma? - Or: Determinants are graphs?! Slides
    137. Topic: What is...elliptic addition? - Or: Torus games. Slides
    138. Topic: What is...the fifteen theorem? - Or: What is special about 1,2,3,5,6,7,10,14,15? Slides
    139. Topic: What is...roundness? - Or: My circle has corners! Slides
    140. Topic: What is...the Jordan curve theorem? - Or: Come on, that's trivial... Slides
    141. Topic: What is...a Coxeter group? - Or: What is...1,$\infty$,3,5,3,4,4,4,3,3,3,3,...? Slides
    142. Topic: What is...the difference between Eulerian and Hamiltonian graphs? - Or: They are not dual!? Slides
    143. Topic: What is...the curse of dimensionality? - Or: Hyperballs do not exist! Well, kind of... Slides
    144. Topic: What is...Polya's theorem? - Or: Birds get lost. Slides
    145. Topic: What are...Chebyshev polynomials? - Or: Fibonacci with signs? Slides
    146. Topic: What is...reverse mathematics? - Or: Thinking backwards. Slides
    147. Topic: What is...the axiom of choice? - Or: It works even if you don’t believe in it. Slides
    148. Topic: What is...the Mason-Stothers theorem? - Or: The ABC of polynomials. Slides
    149. Topic: What is...the pea and the sun paradox? - Or: One orange equals two oranges. Slides
    150. Topic: What is...the Robertson-Seymour theorem? - Or: Minors are majors. Slides
    151. Topic: What is...the Kuratowski-Wagner theorem? - Or: Forbidden pieces. Slides
    152. Topic: What is...the Jones polynomial? - Or: Resolving crossings. Slides
    153. Topic: What are...Catalan numbers? - Or: In praise of counting. Slides
    154. Topic: What is...the Abel-Ruffini theorem? - Or: Loops and roots. Slides
    155. Topic: What is...the art gallery theorem? - Or: How many cameras suffice? Slides
    156. Topic: What is...the finite Kakeya problem? - Or: A finite filling. Slides
    157. Topic: What is...Pick's theorem? - Or: Surprisingly simple. Slides
    158. Topic: What is...Kneser's conjecture? - Or: Coloring and topology. Slides
    159. Topic: What are...incarnations of the Borsuk-Ulam theorem? - Or: Topology or combinatorics or...? Slides
    160. Topic: What is...the Borromean impossibility theorem? - Or: Borromean rings do not exist! Slides
    161. Topic: What are...p-adic integers? - Or: Climbing infinite trees. Slides
    162. Topic: What are...Steiner systems? - Or: Finite geometry and puzzles. Slides
    163. Topic: What is...Heawood's conjecture? - Or: I need more than four colors. Slides
    164. Topic: What is...the Strassen algorithm? - Or: Divide and conquer. Slides
    165. Topic: What are...Gröbner bases? - Or: Minimal intersections. Slides
    166. Topic: What is...the chaos game? - Or: Deterministic versus random. Slides
    167. Topic: What is...the art of locating roots? - Or: Finding roots without finding them. Slides
    168. Topic: What is...the Schwartz-Zippel lemma? - Or: The art of not solving equations. Slides
    169. Topic: What are...random numbers? - Or: Compressible? Slides
    170. Topic: What is...Matiyasevich's theorem? - Or: I can't decide... Slides
    171. Topic: What is...the Burnside problem? - Or: Obviously not! Ah, well...? Slides
    172. Topic: What is...a cellular automaton? - Or: From simple rules to life. Slides
    173. Topic: What is...the diamond lemma? - Or: Can you win? Slides
    174. Topic: What is...Goodstein's theorem? - Or: Killing hydras. Slides
    175. Topic: What are...Monte Carlo experiments? - Or: The shotgun method. Slides
    176. Topic: What are...Artin braid groups? - Or: Topology via algebra. Slides
    177. Topic: What is...Frobenius' density theorem? - Or: Does it factor? Slides
    178. Topic: What is...an ADE classification? - Or: A strange reoccurring pattern. Slides
    179. Topic: What is...the discrete periodic table? - Or: Finite simple groups. Slides
    180. Topic: What is...the smooth periodic table? - Or: Simple Lie groups. Slides
    181. Topic: What is...the strong law of small numbers? - Or: There are not enough small numbers. Slides
    182. Topic: What is...Arrow's theorem? - Or: Why voting is always flawed (and is still a good idea). Slides
    183. Topic: What are...the seventeen wallpaper groups? - Or: Mathematics, architecture and decorative art. Slides
    184. Topic: What is...the philosophy of generating functions? - Or: How to encode counting problems. Slides
    185. Topic: What is...the Reidemeister theorem? - Or: Knotting stings in 2d. Slides
    186. Topic: What is...Euler's polyhedron formula? - Or: 2000 years of not doing the count. Slides
    187. Topic: What is...the Brouwer fixed point theorem? - Or: Why lines need to cross. Slides
    188. Topic: What is...the Lucas theorem? - Or: Playing with digits. Slides
    189. Topic: What is...the Gershgorin circle theorem? - Or: Circling the eigenvalues. Slides
    190. Topic: What is...the Perron-Frobenius theorem? - Or: The leading terms. Slides
  • Playlist What is...tropical geometry?
    1. Topic: What are...tropical applications, part 2? - Or: Phylogenetic trees. Slides
    2. Topic: What are...tropical applications, part 1? - Or: The tropical geometry of neural nets. Slides
    3. Topic: What is...tropical linear algebra, part 5? - Or: Tropical matrix ranks. Slides
    4. Topic: What is...tropical linear algebra, part 4? - Or: Eigenvectors and polytropes. Slides
    5. Topic: What is...tropical linear algebra, part 3? - Or: Tropical matrix powers. Slides
    6. Topic: What is...tropical linear algebra, part 2? - Or: Tropical determinants. Slides
    7. Topic: What is...tropical linear algebra, part 1? - Or: Eigenvalues and graphs. Slides
    8. Topic: What is...tropical geometry, part 16? - Or: Initial terms. Slides
    9. Topic: What is...tropical geometry, part 15? - Or: Tropicalization. Slides
    10. Topic: What is...tropical geometry, part 14? - Or: Polyhedral geometry. Slides
    11. Topic: What is...tropical geometry, part 13? - Or: Non-Archimedean fields. Slides
    12. Topic: What is...tropical geometry, part 12? - Or: Valuations. Slides
    13. Topic: What is...tropical geometry, part 11? - Or: Implicitization. Slides
    14. Topic: What is...tropical geometry, part 10? - Or: Amoebas. Slides
    15. Topic: What is...tropical geometry, part 9? - Or: The tropical Bézout's theorem. Slides
    16. Topic: What is...tropical geometry, part 8? - Or: Newton polygons. Slides
    17. Topic: What is...tropical geometry, part 7? - Or: Tropical curves. Slides
    18. Topic: What is...tropical geometry, part 6? - Or: Tropical varieties. Slides
    19. Topic: What is...tropical geometry, part 5? - Or: Linear programming. Slides
    20. Topic: What is...tropical geometry, part 4? - Or: Tropical matrices. Slides
    21. Topic: What is...tropical geometry, part 3? - Or: Tropical polynomials. Slides
    22. Topic: What is...tropical geometry, part 2? - Or: Tropical arithmetic. Slides
    23. Topic: What is...tropical geometry, part 1? - Or: Introduction. Slides
  • Playlist What is...algebraic geometry?
    1. Topic: What is...sheaf cohomology, part 2? - Or: Properties and definition. Slides
    2. Topic: What is...sheaf cohomology, part 1? - Or: Why do we want it? Slides
    3. Topic: What are...Kähler differentials, part 2? - Or: Tangent bundles. Slides
    4. Topic: What are...Kähler differentials, part 1? - Or: Algebraic calculus. Slides
    5. Topic: What are...quasi-coherent sheaves? - Or: Translate to algebra, please. Slides
    6. Topic: What is...sheafification? - Or: Freeness. Slides
    7. Topic: What is...a skyscraper sheaf? - Or: Dirac's delta. Slides
    8. Topic: What is...a tautological sheaf? - Or: Tautological sheaves are tautological sheaves. Slides
    9. Topic: What are...sheaves of modules? - Or: The weather on earth. Slides
    10. Topic: What are...schemes, take 5? - Or: Back to the main example. Slides
    11. Topic: What are...schemes, take 4? - Or: Schemy summary. Slides
    12. Topic: What are...morphisms of schemes? - Or: Functions that are not determined by their input. Slides
    13. Topic: What are...regular function for schemes? - Or: Division without a field. Slides
    14. Topic: What are...schemes, take 3? - Or: How to evaluate at ideals? Slides
    15. Topic: What are...schemes, take 2? - Or: Spec with a topology. Slides
    16. Topic: What are...schemes, take 1? - Or: Spec in action. Slides
    17. Topic: What are...27 lines? - Or: A cubic surprise! Slides
    18. Topic: What are...dual curves? - Or: Ellipse stays ellipse. Slides
    19. Topic: What is...the Jacobi criterion? - Or: Rank of a matrix. Slides
    20. Topic: What are...smooth varieties? - Or: Not smooth is rare. Slides
    21. Topic: What are...tangent cones? - Or: How to compute them. Slides
    22. Topic: What is...a blow up, take 3? - Or: Tangent cones. Slides
    23. Topic: What is...a blow up, take 2? - Or: Playing with a time coordinate. Slides
    24. Topic: What is...a blow up, take 1? - Or: Blowing up balloons. Slides
    25. Topic: What are...birational maps? - Or: Affine is projective. Slides
    26. Topic: What is...Schubert calculus? - Or: Intersecting spaces. Slides
    27. Topic: What are...Grassmannians, take 2? - Or: A crucial example. Slides
    28. Topic: What are...Plücker coordinates? - Or: Exterior powers. Slides
    29. Topic: What are...Grassmannians? - Or: A space in a space. Slides
    30. Topic: What is...the Veronese embedding? - Or: Symmetric powers. Slides
    31. Topic: What is...the Segre embedding? - Or: Multiplying polynomials? Kind of! Slides
    32. Topic: What is...the projective closure? - Or: Add points at infinity. Slides
    33. Topic: What is...the projective Nullstellensatz? - Or: From projective to affine and back. Slides
    34. Topic: What are...cones? - Or: From affine to projective. Slides
    35. Topic: What are...projective varieties? - Or: Up to scalars. Slides
    36. Topic: What is...projective space? - Or: Let's meet at infinity. Slides
    37. Topic: What are...(abstract) varieties? - Or: Zeros, once more! Slides
    38. Topic: What are...prevarieties? - Or: Patchworks. Slides
    39. Topic: What is...the Why of ringed spaces? - Or: Geometry and algebra again. Slides
    40. Topic: What are...ringed spaces? - Or: Enter, morphisms! Slides
    41. Topic: What are...examples of sheaves? - Or: Sheaves are everywhere. Slides
    42. Topic: What are...sheaves, take 3? - Or: Big from small. Slides
    43. Topic: What are...sheaves, take 2? - Or: A discrete version. Slides
    44. Topic: What are...sheaves, take 1? - Or: Complex analysis again. Slides
    45. Topic: What are...examples of regular functions? - Or: Regular functions and localizations. Slides
    46. Topic: What is...the identity theorem? - Or: Complex versus algebraic geometry. Slides
    47. Topic: What are...regular functions? - Or: Analogs of continuous functions. Slides
    48. Topic: What is...the dimension of a variety? - Or: A space in a space in a space... Slides
    49. Topic: What is...the Zariski topology in algebra? - Or: From topology to algebra. Slides
    50. Topic: What is...the Zariski topology? - Or: Varieties are closed, by definition. Slides
    51. Topic: What is...the coordinate ring? - Or: Polynomial functions and varieties. Slides
    52. Topic: What is...Hilbert's Nullstellensatz? - Or: The zero-locus-theorem. Slides
    53. Topic: What are...ideals of sets? - Or: Enter, algebra! Slides
    54. Topic: What are...conic sections? - Or: Light cones and walls. Slides
    55. Topic: What are...algebraic varieties? - Or: Zeros! Slides
    56. Topic: What is...algebraic geometry? - Or: Polynomials, and more. Slides
  • Playlist Magma in a nutshell, lecture notes: Click
    1. Topic: Magma in a nutshell - part 5.
    2. Topic: Magma in a nutshell - part 4.
    3. Topic: Magma in a nutshell - part 3.
    4. Topic: Magma in a nutshell - part 2.
    5. Topic: Magma in a nutshell - part 1.
    6. Topic: Magma in a nutshell - part 0. Slides
  • Playlist What is...algebraic graph theory?
    1. Topic: What are...representable matroids 2? - Or: How to rule out matrices. Slides
    2. Topic: What are...representable matroids? - Or: Matrices and matroids. Slides
    3. Topic: What are...matroid embeddings? - Or: This actually only about greedoids... Slides
    4. Topic: What is...a greedy algorithm 2? - Or: Greedy for matroids. Slides
    5. Topic: What is...a greedy algorithm 1? - Or: Greedy in general. Slides
    6. Topic: What is...the lattice of flats? - Or: The properties of inclusion. Slides
    7. Topic: What are...cryptomorphisms? - Or: Many definitions = good! Slides
    8. Topic: What are...transversal matroids? - Or: More examples from graph theory. Slides
    9. Topic: What are...linearly independent sets? - Or: All bases are of the same size. Slides
    10. Topic: What is a...matroid? - Or: Bases, forests, partitions and friends. Slides
    11. Topic: What are...colorings of random graphs? - Or: Concentrated colors. Slides
    12. Topic: What are...cliques in random graphs? - Or: Peaks! Slides
    13. Topic: What is...the diameter of random graphs? - Or: The same diameter!? Slides
    14. Topic: What are...symmetries of random graphs? - Or: There are no symmetries! Slides
    15. Topic: What is...true for almost all graphs? - Or: Many, many edges... Slides
    16. Topic: What are...subgraphs of random graphs? - Or: A lot of edges. Slides
    17. Topic: What are...random graph models? - Or: Different, yet the same. Slides
    18. Topic: What are...random graphs? - Or: Random is maybe not so random... Slides
    19. Topic: What is...the Tutte polynomial counting? - Or: Its counting a lot! Slides
    20. Topic: What is...the complexity of the Tutte polynomial? - Or: Easy or difficult? Slides
    21. Topic: What is...Tutte universality? - Or: Everyone discovers the same polynomial. Slides
    22. Topic: What is...the Tutte polynomial? - Or: More counting! Slides
    23. Topic: What is...chromatic detection? - Or: Determined by colorings. Slides
    24. Topic: What is...the chromatic polynomial? - Or: Polynomials and colors. Slides
    25. Topic: What are...graph polynomials? - Or: Easy problems, not hard problems. Slides
    26. Topic: What is...graph drawing? - Or: The Laplacian draws graphs. Slides
    27. Topic: What are...clustering methods? - Or: Partitioning made easy. Slides
    28. Topic: What is...the Laplace matrix? - Or: Taking the degree into account. Slides
    29. Topic: What is...spectral Hamiltonicity? - Or: The second largest - part 3. Slides
    30. Topic: What is...the edge expansion constant? - Or: The second largest - part 2. Slides
    31. Topic: What are...the second eigenvalue's contributions? - Or: Not quite canonical. Slides
    32. Topic: What are...applications of the spectrum? - Or: The spectrum knows a lot! Slides
    33. Topic: What are...graphs with small spectrum? - Or: ADE is it! Slides
    34. Topic: What are...example of spectra? - Or: Let us compute! Slides
    35. Topic: What is...path counting via eigenvalues? - Or: Paths “=” matrix powers “=” largest eigenvalue. Slides
    36. Topic: What is...path counting? - Or: Paths “=” matrix powers. Slides
    37. Topic: What are...adjacency matrices? - Or: Graphs “=” matrices. Slides
    38. Topic: What is...algebraic graph theory? - Or: It's a matrix! Slides
  • Playlist What is...geometric topology?
    1. Topic: What is...braid group cryptography? - Or: Applications 2 (topology in cybersecurity). Slides
    2. Topic: What are...knots and DNA? - Or: Applications 1 (topology in biochemistry). Slides
    3. Topic: What is...the unknotting problem? - Or: How to detect the unknot?! Slides
    4. Topic: What is...the h-cobordism theorem in action? - Or: Towards the Poincaré conjecture. Slides
    5. Topic: What is...the h-cobordism theorem? - Or: Nice manifolds between manifolds. Slides
    6. Topic: What is...the Poincaré conjecture? - Or: Spheres will be spheres. Slides
    7. Topic: What is...4d Kirby calculus again? - Or: Knots and four manifolds, part 2. Slides
    8. Topic: What is...4d Kirby calculus? - Or: Knots and four manifolds, part 1. Slides
    9. Topic: What is...a handle decomposition? - Or: Handles and even more handles! Slides
    10. Topic: What are...four manifolds? - Or: Movies and colors! Slides
    11. Topic: What is...a Heegaard diagram? - Or: Handle diagrams. Slides
    12. Topic: What is...a Heegaard splitting? - Or: Attaching handles. Slides
    13. Topic: What are...lens spaces? - Or: The birth of geometric topology!? Slides
    14. Topic: What are...homology spheres? - Or: Spheres, but not really... Slides
    15. Topic: What is...the linking matrix? - Or: Kirby calculus on matrices. Slides
    16. Topic: What is...Kirby calculus? - Or: Knots and three manifolds, part 2. Slides
    17. Topic: What is...Dehn surgery? - Or: Knots and three manifolds. Slides
    18. Topic: What are...three manifolds? - Or: A glimpse of 4d. Slides
    19. Topic: What is...the chromatic number of a surface? - Or: Graphs on surfaces. Slides
    20. Topic: What are...knotted surfaces? - Or: Codimension 2. Slides
    21. Topic: What is...the classification of surfaces? - Or: Punctures, handles, projective planes. Slides
    22. Topic: What are...words for surfaces? - Or: How to “read” surfaces. Slides
    23. Topic: What are...combinatorial surfaces? - Or: Words and friends. Slides
    24. Topic: What are...surfaces? - Or: Spheres and friends. Slides
    25. Topic: What are...homeomorphisms? - Or: Rubber geometry. Slides
    26. Topic: What is...a knot homology? - Or: Vector spaces, not numbers. Slides
    27. Topic: What is...the bracket polynomial? - Or: Jones and co. Slides
    28. Topic: What are...knot groups? - Or: Never forget the complement. Slides
    29. Topic: What is...the knot genus? - Or: Minimal surfaces and knots. Slides
    30. Topic: What is...the Alexander polynomial? - Or: Alexander-Conway skein calculus. Slides
    31. Topic: What is...the knot determinant? - Or: Enter, linear algebra. Slides
    32. Topic: What is...a knot coloring? - Or: A colorful approach. Slides
    33. Topic: What are...knots? - Or: Why knot?! Slides
    34. Topic: What is...geometric topology? - Or: It's a disc! Slides
  • Playlist What is...representation theory?
    1. Topic: What is...chemical representation theory? - Or: Applications (rep theory in chemistry). Slides
    2. Topic: What is...a local-global principle? - Or: Small determines big. Slides
    3. Topic: What is...a defect? - Or: Measuring complexity. Slides
    4. Topic: What is...a block? - Or: Decomposing a problem. Slides
    5. Topic: What are...Brauer characters? - Or: Ignore the ground field. Slides
    6. Topic: What is...modular representation theory? - Or: Division made hard. Slides
    7. Topic: What is...the Tsetlin library? - Or: Sorting books made easy. Slides
    8. Topic: What is...the Ehrenfest model? - Or: Rep theory and diffusion. Slides
    9. Topic: What are...the simples of the transformation monoid? - Or: Through strands, again. Slides
    10. Topic: What are...the simples of the Brauer monoid? - Or: Through strands. Slides
    11. Topic: What is...the Brauer monoid? - Or: 1d cobordisms! Slides
    12. Topic: What is...the CMP theorem? - Or: Clifford-Munn-Ponizovskiĭ theorem a.k.a. H-reduction. Slides
    13. Topic: What are...Green cells? - Or: Measuring information loss. Slides
    14. Topic: What is...representation theory of monoids? - Or: What to expect. Slides
    15. Topic: What is...the Young lattice? - Or: Representations of symmetric groups, part 4. Slides
    16. Topic: What is...Frobenius' character formula? - Or: Representations of symmetric groups, part 3. Slides
    17. Topic: What are...Specht modules? - Or: Representations of symmetric groups, part 2. Slides
    18. Topic: What are...Young diagrams? - Or: Representations of symmetric groups, part 1. Slides
    19. Topic: What is...Frobenius reciprocity? - Or: Back-and-forth. Slides
    20. Topic: What are...induction and restriction? - Or: How to find lost information! Kind of... Slides
    21. Topic: What is...Burnside's theorem? - Or: Groups and representations. Slides
    22. Topic: What is...Lagrange's theorem for representations? - Or: Divisibility. Slides
    23. Topic: What is...finite Fourier analysis? - Or: Fourier and finite groups. Slides
    24. Topic: What is...the dual group? - Or: Groups of characters. Slides
    25. Topic: What is...the regular representation? - Or: Action on itself. Slides
    26. Topic: What are...Schur's orthogonality relations? - Or: An orthonormal basis. Slides
    27. Topic: What are...examples of character tables? - Or: The ATLAS of finite groups and co. Slides
    28. Topic: What is...a character table? - Or: The gist of the matter!? Slides
    29. Topic: What are...characters? - Or: Polynomials! Slides
    30. Topic: What is...Schur's lemma? - Or: Matrices rarely commute. Slides
    31. Topic: What is...semisimplicity? - Or: The finite group miracle. Slides
    32. Topic: What is...the Jordan-Hölder theorem? - Or: Like prime numbers. Slides
    33. Topic: What are...indecomposable representations? - Or: The elements! Well, kind of... Slides
    34. Topic: What is...a simple representation? - Or: The elements! Slides
    35. Topic: What are...intertwiners? - Or: Maps between representations. Slides
    36. Topic: What are...modules? - Or: Linear symmetries. Slides
    37. Topic: What are...representations? - Or: Matrices are cool! Slides
    38. Topic: What is...representation theory? - Or: Lets make life linear! Slides
  • Playlist What is...category theory?
    1. Topic: What are...props? - Or: Applications 2 (category theory in signal processing). Slides
    2. Topic: What are...TQFTs? - Or: Applications 1 (category theory in mathematics). Slides
    3. Topic: What are...2-categories? - Or: Categories in categories. Slides
    4. Topic: What are...braided categories? - Or: Braids and categories. Slides
    5. Topic: What is...duality in categories? - Or: Rigid and pivotal categories. Slides
    6. Topic: What are...string diagrams, take 2? - Or: Two-dimensional algebra. Slides
    7. Topic: What is...strictification? - Or: MacLane's coherence theorem. Slides
    8. Topic: What are...monoidal categories? - Or: Monoids categorified. Slides
    9. Topic: What are...Kan extensions? - Or: Recover information; kind of... Slides
    10. Topic: What is...Beck's monadicity theorem? - Or: Categories via actions. Slides
    11. Topic: What are...algebras? - Or: Actions in action. Slides
    12. Topic: What are...monads? - Or: The natural numbers as functors. Slides
    13. Topic: What are...adjoint functors diagrammatically? - Or: Zigzag! Slides
    14. Topic: What are...string diagrams? - Or: Diagrammatic algebra. Slides
    15. Topic: What is...the adjoint functor theorem? - Or: Identities are free! Slides
    16. Topic: What are...examples of adjoint functors? - Or: Adjoints occur almost everywhere. Slides
    17. Topic: What are...adjoint functors? - Or: Life is not invertible. Slides
    18. Topic: What are...continuous functors? - Or: Functors not functions. Slides
    19. Topic: What is...a complete category? - Or: Real numbers!? Slides
    20. Topic: What are...limits? - Or: Universal diagrams. Slides
    21. Topic: What are...universal properties? - Or: Abstract nonsense in perfection. Slides
    22. Topic: What are...(co)equalizers? - Or: Why kernels? Slides
    23. Topic: What are...pushouts and pullbacks? - Or: Faces “equal” relations. Slides
    24. Topic: What are...products and coproducts? - Or: Vector spaces rock! Slides
    25. Topic: What are...initial and terminal objects? - Or: Another reason why zero is great! Slides
    26. Topic: What is...a concrete category? - Or: Set-based is cool, well sometimes ;-) Slides
    27. Topic: What is...the Yoneda lemma? - Or: Shoot on sight. Slides
    28. Topic: What is...a subcategory? - Or: The symmetric groups and cobordisms. Slides
    29. Topic: What is...the skeleton? - The bare minimum. Slides
    30. Topic: What is...equivalence? - Or: Equal means...? Slides
    31. Topic: What are...natural transformations? - Maps between functors. Slides
    32. Topic: What are...properties of functors? - Or: Preserving diagrams. Slides
    33. Topic: What are...functors? - Maps between categories. Slides
    34. Topic: What is...monic-epic-iso? - Or: Not quite injective-surjective-bijective. Slides
    35. Topic: What is...the duality principle? - Flipping arrows. Slides
    36. Topic: What are...(commuting) diagrams? - Or: Graphs and paths. Slides
    37. Topic: What is...a category? - Arrows in action. Slides
    38. Topic: What is...category theory? - Or: Organizing ideas. Slides
  • Playlist What is...algebraic topology?; for the lecture website see Click
    1. Topic: What is...persistent homology? - Or: Applications 2 (topology in data analysis). Slides
    2. Topic: What are...some applications of topology? - Or: Applications 1 (topology in mathematics). Slides
    3. Topic: What is...the Hurewicz theorem? - Or: Homotopy and homology. Slides
    4. Topic: What are...Eilenberg-MacLane spaces? - Or: They are not spheres. Slides
    5. Topic: What is...cellular approximation of spaces? - Or: My polynomials have cells. Slides
    6. Topic: What is...cellular approximation? - Or: I miss my space-filling curves... Slides
    7. Topic: What is...Whitehead's theorem? - Or: A perfect invariant!? Slides
    8. Topic: What are...homotopy groups? - Or: Spheres in spaces. Slides
    9. Topic: What are...examples of (co)homology groups? - Or: Another of my favorite lists. Slides
    10. Topic: What is...Alexander duality? - Or: Horned spheres!? Slides
    11. Topic: What is...Poincaré duality? - Or: My face is 0-dimensional. Slides
    12. Topic: What is...orientability? - Or: A homological definition. Slides
    13. Topic: What is...the Künneth formula? - Or: Multiplication vs. tensor product. Slides
    14. Topic: What is...the cohomology ring? - Or: Polynomials, of course. Slides
    15. Topic: What is...the cohomology ring intuitively? - Or: Counting intersections. Slides
    16. Topic: What is...the universal coefficient theorem? - Or: Working integrally rocks. Slides
    17. Topic: What is...the Mayer-Vietoris sequence? - Or: More than the sum of its parts!? Slides
    18. Topic: What is...a (co)homology theory? - Or: Shut up and calculate. Slides
    19. Topic: What is...relative homology? - Or: Calculations modulo subspaces. Slides
    20. Topic: What is...cohomology? - Or: Reversing arrows. Slides
    21. Topic: What is...homology categorifying? - Or: Modules, polynomials and numbers. Slides
    22. Topic: What is...cellular homology? - Or: Winding around. Slides
    23. Topic: What are...simplicial and singular homology? - Or: Cycles modulo boundaries. Slides
    24. Topic: What are...simplicial complexes? - Or: Triangles everywhere. Slides
    25. Topic: What is...homology intuitively? - Or: What is a hole? Slides
    26. Topic: What are...examples of fundamental groups? - Or: One of my favorite lists. Slides
    27. Topic: What is...a Cayley complex? - Or: Groups geometrically. Slides
    28. Topic: What are...covering space action? - Or: Deck transformations and friends. Slides
    29. Topic: What is...a covering space? - Or: A topological Galois correspondence. Slides
    30. Topic: What is...the Seifert-Van Kampen theorem? - Or: Cut and compute. Slides
    31. Topic: What is...the fundamental group? - Or: How not to hang pictures on walls. Slides
    32. Topic: What are...operations on cell complexes? - Or: Cell by cell. Slides
    33. Topic: What are...cell complexes? - Or: Constructed from discs. Slides
    34. Topic: What is...homotopy? - Or: The same shape!? Slides
    35. Topic: What is...algebraic topology? - Or: Translating from topology to algebra. Slides
  • Playlist What is...algebra?
    1. Topic: What are...solvable polynomials? - Or: Field and Galois theory, application 3. Slides
    2. Topic: What is...the Kronecker–Weber theorem? - Or: Field and Galois theory, application 2. Slides
    3. Topic: What are...the limits of straightedge and compass? - Or: Field and Galois theory, application 1. Slides
    4. Topic: What are...the Galois groups of finite fields? - Or: Finite fields are easy. Slides
    5. Topic: What is...the fundamental theorem of Galois theory? - Or: From roots to groups and back. Slides
    6. Topic: What are...Galois extensions? - Or: Shuffling roots. Slides
    7. Topic: What are...group actions on fields? - Or: The beginning of Galois theory. Slides
    8. Topic: What are...normal and separable extensions? - Or: Linear factors matter. Slides
    9. Topic: What are...minimal polynomials? - Or: Minimal relations. Slides
    10. Topic: What are...field extensions? - Or: Adjoining roots. Slides
    11. Topic: What are...(finite) fields? - Or: Fields are relatively rare. Slides
    12. Topic: What are...irreducible polynomials? - Or: Analogs of primes. Slides
    13. Topic: What is...a unique factorization domain? - Or: Primes! Slides
    14. Topic: What is...an Euclidean domain? - Or: Generalizing division with remainder. Slides
    15. Topic: What is...the Chinese remainder theorem? - Or: Arranging rectangles. Slides
    16. Topic: What is...Hilbert's basis theorem? - Or: Algebra meets geometry (once again). Slides
    17. Topic: What is...localization? - Or: Why fractions matter. Slides
    18. Topic: What is...the calculus of ideals? - Or: Ideals are like numbers. Slides
    19. Topic: What are...subrings and ideals? - Or: Two valid substructures. Slides
    20. Topic: What is...a ring? - Or: Generalizing the integers. Slides
    21. Topic: What is...the Jordan-Hölder theorem? - Or: The elements of group theory. Slides
    22. Topic: What are...matrix groups? - Or: The most important groups?! Slides
    23. Topic: What is...the classification of abelian groups? - Or: Factoring numbers. Slides
    24. Topic: What are...the Sylow theorems? - Or: Canonical substructures? Slides
    25. Topic: What is a...Cayley graph? - Or: Graphs and groups. Slides
    26. Topic: What are...actions, orbits and stabilizers? - Or: How many ways are there to...? Slides
    27. Topic: What is...the symmetric group? - Or: Why strings can shuffle numbers. Slides
    28. Topic: What are...the isomorphism theorems? - Or: Basic rules of algebra generalize. Slides
    29. Topic: What is...a (normal) subgroup? - Or: Why care about the difference? Slides
    30. Topic: What is...a group? - Or: Abstract symmetries. Slides
    31. Topic: What is...algebra? - Or: How to not solve polynomial equations. Slides
  • Playlist What is...linear algebra?
    1. Topic: What is...a projective space? - Or: My lines cross. Slides
    2. Topic: What is...an affine map? - Or: Translations in action. Slides
    3. Topic: What is...an affine space? - Or: I lost my origin. Slides
    4. Topic: What is...the symmetric algebra? - Or: Polynomials in vector spaces. Slides
    5. Topic: What is...the exterior algebra? - Or: Anticommuting polynomials. Slides
    6. Topic: What are...tensor products? - Or: How to multiply vector spaces and matrices. Slides
    7. Topic: What is...a quotient vector space? - Or: Identifying information. Slides
    8. Topic: What is...the dual vector spaces? - Or: Two flipped sides. Slides
    9. Topic: What is...the LU decomposition? - Or: Lower-upper. Slides
    10. Topic: What is...Gaussian elimination? - Or: How to find intersections. Slides
    11. Topic: What is...a system of linear equations? - Or: Intersections matter. Slides
    12. Topic: What is...Sylvester's law of inertia? - Or: Signatures is linear algebra. Slides
    13. Topic: What is...the spectral theorem? - Or: My eigenvalues are real! Slides
    14. Topic: What is...an isometry? - Or: Tessellations of my walls. Slides
    15. Topic: What is...orthogonality? - Or: Flavors of 90 degrees. Slides
    16. Topic: What is...an inner product? - Or: Generalizing angles and lengths. Slides
    17. Topic: What is...a linear subspace? - Or: Hyperplanes and friends. Slides
    18. Topic: What is...the exponential of a matrix? - Or: Nilpotent vanishing. Slides
    19. Topic: What is...the Jordan normal form again? - Or: How to find and compute a gold standard. Slides
    20. Topic: What is...the Jordan normal form? - Or: Why (almost) all matrices are diagonalizable. Slides
    21. Topic: What is...diagonalization? - Or: Finding the right coordinate system. Slides
    22. Topic: What are...traces? - Or: The best? matrix invariant. Slides
    23. Topic: What are...eigenvalues and eigenvectors? - Or: Linear fixed points. Slides
    24. Topic: What is...the characteristic polynomial? - Or: Matrix roots. Slides
    25. Topic: What is...the permanent? - Or: The trivial representation. Slides
    26. Topic: What is...the determinant? - Or: Signed permutations. Slides
    27. Topic: What are...direct sums? - Or: How to add vector spaces and matrices. Slides
    28. Topic: What is...a change of basis? - Or: Moving, rotating and scaling axes. Slides
    29. Topic: What is...a linear map? - Or: Linear algebra done right. Slides
    30. Topic: What is...matrix multiplication? - Or: Why the definition is not random. Slides
    31. Topic: What is...a matrix? - Or: Incarnations of the same beast. Slides
    32. Topic: What is...a basis? - Or: A notion of dimension. Slides
    33. Topic: What is...a vector space? - Or: Geometry à la Descartes. Slides
    34. Topic: What is...linear algebra? - Or: Everything is linear. Slides