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Early observations with the James Webb Space Telescope (JWST) have revealedthe existence of an unexpectedly large abundance of extremely massive galaxiesat redshifts $z \gtrsim 5$: these observations are in tension with thepredictions not only of the standard $\Lambda$CDM cosmology, but also withthose of a wide class of dynamical dark energy (DE) models, and are generallyin better agreement with models characterized by a phantom behaviour. Here weconsider a model, inspired by string theory and the ubiquity of anti-de Sittervacua therein, featuring an evolving DE component with positive energy densityon top of a negative cosmological constant, argued in an earlier exploratoryanalysis to potentially be able to explain the JWST observations. We perform arobust comparison of this model against JWST data, considering both photometricobservations from the CEERS program, and spectroscopic observations from theFRESCO survey. We show that the model is able to accommodate the JWSTobservations, with a consistency probability of up to $98\%$, even in thepresence of an evolving component with a quintessence-like behaviour (easier toaccommodate theoretically compared to phantom DE), while remaining consistentwith standard low-redshift probes. Our results showcase the tremendouspotential of measurements of high-redshift galaxy abundances in tests offundamental physics, and their valuable complementarity with standardcosmological probes.

Negative cosmological constant in the dark energy sector: tests from JWST photometric and spectroscopic observations of high-redshift galaxies