Adler's conjecture on spectra of two-cardinal counting functions

Let TT be a countable theory and let fT(κ,λ)f_T(\kappa,\lambda) be the associated two-cardinal counting function for infinite cardinals kappaleqlambdakappaleqlambda. Adler's counting-spectrum conjecture. There are only finitely many possible functions fT(κ,λ)f_T(\kappa,\lambda) as TT ranges over countable theories, and the property that TT is NTP2_2 can be detected from fT(κ,λ)f_T(\kappa,\lambda). If TT has TP2_2, the function is maximal, namely fT(κ,λ)=λκf_T(\kappa,\lambda)=\lambda^{\kappa} for all aleph0leqkappaleqlambdaaleph_0leqkappaleqlambda. The first assertion is addressed by later results in the paper, while the second is explicitly refuted by the counterexample identified below.

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Primary source

Artem Chernikov and Chuyin Jiang, “Fractional Helly property and combinatorics of forking in NTP_2 theories”, arXiv:2605.18123 (2026).

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