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Elementary Symmetric Partitions

  • Cristina Ballantine,
  • George Beck,
  • Mircea Merca,
  • Bruce E. Sagan

摘要

Let \(e_k(x_1,\ldots ,x_\ell )\) e k ( x 1 , , x ) be an elementary symmetric polynomial and let \(\lambda =(\lambda _1,\ldots ,\lambda _\ell )\) λ = ( λ 1 , , λ ) be an integer partition. Define \({{\,\textrm{pre}\,}}_k(\lambda )\) pre k ( λ ) to be the partition whose parts are the summands in the evaluation \(e_k(\lambda _1,\ldots ,\lambda _\ell )\) e k ( λ 1 , , λ ) . The study of such partitions was initiated by Ballantine, Beck, and Merca who showed (among other things) that \({{\,\textrm{pre}\,}}_2\) pre 2 is injective as a map on binary partitions of n. In the present work, we derive a host of identities involving the sequences which count the number of parts of a given value in the image of \({{\,\textrm{pre}\,}}_2\) pre 2 . These include generating functions, explicit expressions, and formulas for forward differences. We generalize some of these to d-ary partitions and explore connections with color partitions. Our techniques include the use of generating functions and bijections on rooted partitions. We end with a list of conjectures and a direction for future research.