Simultaneous core partitions with nontrivial common divisor

Jean-Baptiste Gramain, Rishi Nath* (Corresponding Author), James A. Sellers

*Corresponding author for this work

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A tremendous amount of research has been done in the last two decades on (s, t)-core partitions when s and t are relatively prime integers. Here we change perspective slightly and explore properties of (s, t)-core and-core partitions for s and t with a nontrivial common divisor g. We begin by recovering, using the gcore and g-quotient construction, the generating function for (s, t)-core partitions first obtained byAukerman et al. (Discrete Math 309(9):2712–2720, 2009). Then, using a construction developed by the first two authors, we obtain a generating function for the number of -core partitions of n. Our approach allows for new results on t-cores and self-conjugate t-cores that are not g-cores and -cores that are not-cores, thus strengthening positivity results of Ono and Granville (Trans Am Soc 348:221–228, 1996), Baldwin et al. (J Algebra 297:438–452, 2006), and Kiming (J Number Theory 60:97–102, 1996). We then move to bijections between bar-core partitions and self-conjugate partitions. We give a new, short proof of a correspondence between self-conjugate t-core and -core partitions when t is odd and positive first due to Yang (Ramanujan J 44:197, 2019). Then, using two different lattice-path labelings, one due to Ford et al.(J Number Theory 129:858–865, 2009), the other to Bessenrodt and Olsson (J Algebra 306:3–16, 2006), we give a bijection between self-conjugate (s, t)-core and -core partitions when s and t are odd and coprime. We end this section with a bijection between self-conjugate (s, t)-core and -core partitions when s and t are odd and nontrivial g which uses the results stated above. We end the paper by noting (s, t)-core and -core partitions inherit Ramanujan-type congruences from those of g-core and -core partitions.
Original languageEnglish
Pages (from-to)839–863
Number of pages25
JournalThe Ramanujan Journal
Early online date24 Jul 2020
Publication statusPublished - Dec 2021


  • Partition
  • Simultaneous core partition
  • Congruence
  • Generating function


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