arXiv subjects
Publications and source records attributed to Alexander R. Miller.
For any irreducible character $χ$ of a finite group $G$, let $θ(χ)$ denote the proportion of elements $g\in G$ for which $χ(g)$ is either zero or a root of unity. Then for any $L\in[1/2,1]$ and any $ε>0$, there exists an irreducible character $χ$ of a finite group such that $|θ(χ)-L|<ε$.
Topological models are characterized by a quantized topological invariant and provide a description of novel phases of matter that can exhibit localized edge states, corner modes, and chiral transport. We experimentally realize two 1-D lattices supporting symmetry-protected topology - the Su-Schrieffer-Heeger (SSH) and extended SSH models using the synthetic frequency dimension of coupled fiber ring resonators. We introduce and experimentally demonstrate cascaded heterodyning as a technique for low-noise, single-shot winding number measurements through the mean chiral displacement and band structure measurements. Through our robust setup and detection techniques we can extend our capability to realizing 1-D ladder models, demonstrating a modified Creutz ladder with a staggered flux with each plaquette. This highly reconfigurable and compact fiber optics platform for Hamiltonian simulation, along with a low-noise detection scheme, provides a path forward for chip-scale realizations.
If $n>4$ and $c(θ)$ denotes the set of irreducible constituents of a character $θ$, then $c(χ^k)={\rm Irr}(S_n)$ for all nonlinear $χ\in {\rm Irr}(S_n)$ if and only if $k\geq n-1$.
We provide an example of a finite group with a conjugacy class of average size on which fewer than half of the irreducible characters are either zero or a root of unity.
This is a brief report on some recent large-scale Monte Carlo simulations for approximating the density of zeros in character tables of large symmetric groups. Previous computations suggested that a large fraction of zeros cannot be explained by classical vanishing results. Our computations eclipse previous ones and suggest that the opposite is true. We find empirically that almost all of the zeros are of a single classical type.
If all of the entries of a large $S_n$ character table are covered up and you are allowed to uncover one entry at a time, then how can you quickly identify all of the indexing characters and conjugacy classes? We present a fast algorithmic solution that works even when n is so large that almost none of the entries of the character table can be computed. The fraction of the character table that needs to be uncovered has exponential decay, and for many of these entries we are only interested in whether the entry is zero.
For any finite group $G$, Thompson proved that, for each $χ\in {\rm Irr}(G)$, $χ(g)$ is a root of unity or zero for more than a third of the elements $g\in G$, and Gallagher proved that, for each larger than average class $g^G$, $χ(g)$ is a root of unity or zero for more than a third of the irreducible characters $χ\in {\rm Irr}(G)$. We show that in many cases "more than a third" can be replaced by "more than half".
The characters $χ(π)$ of $S_n$ that depend only on the number of cycles of $π$ are completely determined.
Orthogonality relations for Foulkes characters of full monomial groups are presented, along with three solutions to the problem of decomposing products of these characters, and new applications, including a product reformulation of a Markov chain for adding random numbers studied by Diaconis and Fulman, and a new proof of a theorem of Zagier which generalizes one of Harer and Zagier on the enumeration of Riemann surfaces of a given genus.
If $λ$ and $μ$ are two non-empty Young diagrams with the same number of squares, and $\boldsymbolλ$ and $\boldsymbolμ$ are obtained by dividing each square into $d^2$ congruent squares, then the corresponding character value $χ_{\boldsymbolλ}(\boldsymbolμ)$ is divisible by $d!$.
In the high rank limit, the fraction of non-zero character table entries of finite simple groups of Lie type goes to zero.
For $G={\rm GL}(n,q)$, the proportion $P_{n,q}$ of pairs $(χ,g)$ in ${\rm Irr}(G)\times G$ with $χ(g)\neq 0$ satisfies $P_{n,q}\to 0$ as $n\to\infty$.
For a real reflection group the reflecting hyperplanes cut out on the unit sphere a simplicial complex called the Coxeter complex. Abramenko showed that each reflecting hyperplane meets the Coxeter complex in another Coxeter complex if and only if the Coxeter diagram contains no subdiagram of type $D_4$, $F_4$, or $H_4$. The present paper extends Abramenko's result to a wider class of complex reflection groups. These groups have a Coxeter-like presentation and a Coxeter-like complex called the Milnor fiber complex. Our first main theorem classifies the groups whose reflecting hyperplanes meet the Milnor fiber complex in another Milnor fiber complex. To understand better the walls that fail to be Milnor fiber complexes we introduce Milnor walls. Our second main theorem generalizes Abramenko's result in a second way. It says that each wall of a Milnor fiber complex is a Milnor wall if and only if the diagram contains no subdiagram of type $D_4$, $F_4$, or $H_4$.
The object of this short note is to prove a theorem and present a conjecture for the number of even entries in the character table of the symmetric group.
Smith normal form evaluations found by Bessenrodt and Stanley for some Hankel matrices of q-Catalan numbers are proven in two ways. One argument generalizes the Bessenrodt-Stanley results for the Smith normal form of a certain multivariate matrix that refines one studied by Berlekamp, Carlitz, Roselle, and Scoville. The second argument, which uses orthogonal polynomials, generalizes to a number of other Hankel matrices, Toeplitz matrices, and Gram matrices. It gives new results for q-Catalan numbers, q-Motzkin numbers, q-Schröder numbers, q-Stirling numbers, q-matching numbers, q-factorials, q-double factorials, as well as generating functions for permutations with eight statistics.
It is well-known that the number of planar maps with prescribed vertex degree distribution and suitable labeling can be represented as the leading coefficient of the $\frac{1}{N}$-expansion of a joint cumulant of traces of powers of an $N$-by-$N$ GUE matrix. Here we undertake the calculation of this leading coefficient in a different way. Firstly, we tridiagonalize the GUE matrix in the manner of Trotter and Dumitriu-Edelman and then alter it by conjugation to make the subdiagonal identically equal to $1$. Secondly, we apply the cluster expansion technique (specifically, the Brydges-Kennedy-Abdesselam-Rivasseau formula) from rigorous statistical mechanics. Thirdly, by sorting through the terms of the expansion thus generated we arrive at an alternate interpretation for the leading coefficient related to factorizations of the long cycle $(12\cdots n)\in S_n$. Finally, we reconcile the group-theoretical objects emerging from our calculation with the labeled mobiles of Bouttier-Di Francesco-Guitter.
We consider random character values X(g) of the symmetric group on n symbols, where X is chosen at random from the set of irreducible characters and g is chosen at random from the group, and we show that X(g)=0 with probability tending to one as n tends to infinity.
The lattice of intersections of reflecting hyperplanes of a complex reflection group W may be considered as the poset of 1-eigenspaces of the elements of W. In this paper we replace 1 with an arbitrary eigenvalue and study the topology and homology representation of the resulting poset. After posing the main question of whether this poset is shellable, we show that all its upper intervals are geometric lattices, and then answer the question in the affirmative for the infinite family G(m,p,n) of complex reflection groups, and the first 31 of the 34 exceptional groups, by constructing CL-shellings. In addition, we completely determine when these eigenspaces of W form a K(pi,1) (resp. free) arrangement. For the symmetric group, we also extend the combinatorial model available for its intersection lattice to all other eigenvalues by introducing "balanced partition posets", presented as particular upper order ideals of Dowling lattices, study the representation afforded by the top (co)homology group, and give a simple map to the posets of pointed d-divisible partitions.