168758 20260217214839.0 doi 10.1007/JHEP02(2026)020 sideral 148134 ART-2026-148134 eng Asorey, Manuel Universidad de Zaragoza (orcid)0000-0003-3669-6241 Reflection positivity in a higher-derivative model with physical bound states of ghosts 2026 The inclusion of higher derivatives is a necessary condition for a renormalizable or superrenormalizable local theory of quantum gravity. On the other hand, higher derivatives lead to classical instabilities and a loss of unitarity at the quantum level. A standard way to detect such issues is by examining the reflection positivity condition and the existence of a Källén-Lehmann spectral representation for the two-point function. We demonstrate that these requirements for a consistent quantum theory are satisfied in a theory we have recently proposed. This theory is based on a six-derivative scalar field action featuring a pair of complex-mass ghost fields that form a bound state. Our results support the interpretation that physical observables can emerge from ghost dynamics in a consistent and unitary framework. Access copy available to the general public Unrestricted info:eu-repo/grantAgreement/ES/DGA-FSE/E21-17R info:eu-repo/grantAgreement/ES/MICINN/PGC2022-126078NB-C21 info:eu-repo/semantics/openAccess by https://creativecommons.org/licenses/by/4.0/deed.es info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Krein, Gastão Pardina, Miguel Universidad de Zaragoza Shapiro, Ilya L. 2004 405 Universidad de Zaragoza Dpto. Física Teórica Área Física Teórica 2026, 20 (2026), [14 pp.] J. high energy phys. Journal of High Energy Physics 1126-6708 299317 http://zaguan.unizar.es/record/168758/files/texto_completo.pdf Versión publicada 1467233 http://zaguan.unizar.es/record/168758/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:168758 articulos driver 2026-02-17-20:15:03 ARTICLE