Li-Yuan ChiangYU-TIN HUANGWei LiLaurentiu RodinaHe-Chen Weng2022-12-162022-12-162021-05-071029-8479https://scholars.lib.ntu.edu.tw/handle/123456789/626570https://www.scopus.com/inward/record.uri?eid=2-s2.0-85126207650&doi=10.1007%2fJHEP03%282022%29063&partnerID=40&md5=5e570c26b6923815d5cf4c5c8477ccbav2. Comparison with SDPB results updated, with perfect matching and improved analytic boundaries given v3. Streamlined discussion of double moment problem in Section 2; closer comparison with numerical results in Section 3Recently it was proposed that the theory space of effective field theories with consistent UV completions can be described as a positive geometry, termed the EFThedron. In this paper we demonstrate that at the core, the geometry is given by the convex hull of the product of two moment curves. This makes contact with the well studied bi-variate moment problem, which in various instances has known solutions, generalizing the Hankel matrices of couplings into moment matrices. We are thus able to obtain analytic expressions for bounds, which perfectly match numerical results from semi-definite programing methods. Furthermore, we demonstrate that crossing symmetry in the IR imposes non-trivial constraints on the UV spectrum. In particular, permutation invariance for identical scalar scattering requires that any UV completion beyond the scalar sector must contain arbitrarily high spins, including at least all even spins $\ell\le28$, with the ratio of spinning spectral functions bounded from above, exhibiting large spin suppression. The spinning spectrum must also include at least one state satisfying a bound $m^2_{J}<M^2 \frac{( J^2-12) ( J^4 - 32 J^2 +204)}{8 (150 - 43 J^2 + 2 J^4)}$, where $J^2=\ell(\ell+1)$, and $M^2$ is the mass of the heaviest spin 2 state in the spectrum.Effective Field Theories; Scattering Amplitudes; MOMENT PROBLEM; High Energy Physics - Theory; High Energy Physics - Theoryjournal article10.1007/JHEP03(2022)0632-s2.0-85126207650WOS:000767221800001http://arxiv.org/abs/2105.02862v3