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8 votes
0 answers
318 views

Why are these Littlewood-Richardson coefficients congruent to 1 mod 8?

Let $n\in{\mathbb N}$ and write $n=q_1+q_2+\dots+q_t$, where $q_1>q_2>\dots>q_t$ are powers of $2$. Let $\lambda_n$ be the partition with Frobenius symbol $(q_1-1,q_2-1,\dots,q_t-1;q_t,q_{t-1}...
John Murray's user avatar
  • 1,090
9 votes
0 answers
398 views

When do almost all these invariants of tensors vanish?

Let $A,B,C,D$ be $n$-dimensional vector spaces over a field $k$. There is a natural homomorphism from the $mn^m$th tensor power $A^{\otimes (m n^m)} $ of $A$ to $k$ given by the determinant map $A^{\...
Will Sawin's user avatar
  • 149k
14 votes
1 answer
835 views

Special configurations on a circle from a homological algebra problem

Here is the short version of the combinatorial problem: Given a positive integer $n \geq 2$. Draw a circle with $2n$ points indexed by the numbers from $\mathbb{Z}/ 2n \mathbb{Z}$. We colour the ...
Mare's user avatar
  • 26.5k
27 votes
1 answer
891 views

Why do the adjoint representations of three exceptional groups have the same first eight moments?

For a representation of a compact Lie group, the $n$th moment of the trace of that representation against the Haar measure is the dimension of the invariant subspace of the $n$th tensor power. The ...
Will Sawin's user avatar
  • 149k