We perform post-Newtonian analysis of double field theory as a test of string theory in gravitational sector against observations. We identify the Eddington-Robertson-Schiff parameters βPPN, γPPN with the charges of electric H flux and dilaton respectively, and further relate them to stress-energy tensor. We show βPPN=1 from weak energy condition and argue that the observation of γPPN≃1 signifies the ultrarelativistic equation of state in baryons, or the suppression of gluon condensate.
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We wish to thank Robert Brandenberger, Minkyoo Kim, Bum-Hoon Lee, Chang-Hwan Lee, Hocheol Lee, Taekoon Lee, Wonwoo Lee, Shinji Mukohyama, Sang-Jin Sin, and Clifford Will for useful comments and correspondences. This work is supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) Grants No. NRF-2016R1D1A1B01015196, NRF-2018R1A2B2007163, and NRF-2020R1A6A1A03047877 (Center for Quantum Space Time).
© 2022 authors. Published by the American Physical Society.