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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2501.15667 |
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| _version_ | 1866913666791636992 |
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| author | Campbell, John M. |
| author_facet | Campbell, John M. |
| contents | For an integer partition $ λ$ of $n$ and an $n \times n$ matrix $A$, consider the expansion of the immanant $\text{Imm}^λ(A)$ as a sum indexed by permutations $σ$ of order $n$, with coefficients given by the irreducible characters $χ^λ(\text{ctype}(σ))$ of the symmetric group $S_{n}$, for the cycle type $\text{ctype}(σ) \vdash n$ of $σ$. Skandera et al. have introduced combinatorial interpretations of a generalization of immanants given by replacing the coefficient $χ^λ(\text{ctype}(σ))$ with preimages with respect to the Frobenius morphism of elements among the distinguished bases of the algebra $\textsf{Sym}$ of symmetric functions. Since $ \textsf{Sym}$ is contained in the algebra $\textsf{QSym}$ of quasisymmetric functions, this leads us to further generalize immanants with the use of quasisymmetric functions. Since bases of $ \textsf{QSym}$ are indexed by integer compositions, we make use of cycle compositions in place of cycle types to define the family of quasi-immanants introduced in this paper. This is achieved through the use of the quasisymmetric power sum bases due to Ballantine et al., and we prove a combinatorial formula for the coefficients arising in an analogue, given by a special case of quasi-immanants associated with quasisymmetric Schur functions, of second immanants. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_15667 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Quasi-immanants Campbell, John M. Combinatorics 15A15 For an integer partition $ λ$ of $n$ and an $n \times n$ matrix $A$, consider the expansion of the immanant $\text{Imm}^λ(A)$ as a sum indexed by permutations $σ$ of order $n$, with coefficients given by the irreducible characters $χ^λ(\text{ctype}(σ))$ of the symmetric group $S_{n}$, for the cycle type $\text{ctype}(σ) \vdash n$ of $σ$. Skandera et al. have introduced combinatorial interpretations of a generalization of immanants given by replacing the coefficient $χ^λ(\text{ctype}(σ))$ with preimages with respect to the Frobenius morphism of elements among the distinguished bases of the algebra $\textsf{Sym}$ of symmetric functions. Since $ \textsf{Sym}$ is contained in the algebra $\textsf{QSym}$ of quasisymmetric functions, this leads us to further generalize immanants with the use of quasisymmetric functions. Since bases of $ \textsf{QSym}$ are indexed by integer compositions, we make use of cycle compositions in place of cycle types to define the family of quasi-immanants introduced in this paper. This is achieved through the use of the quasisymmetric power sum bases due to Ballantine et al., and we prove a combinatorial formula for the coefficients arising in an analogue, given by a special case of quasi-immanants associated with quasisymmetric Schur functions, of second immanants. |
| title | Quasi-immanants |
| topic | Combinatorics 15A15 |
| url | https://arxiv.org/abs/2501.15667 |