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arXiv · 2602.21642

Geodesic completion of big bangs from emergent geometry

Brooke Berrios·Cameron Corley·Sky O'Donnell·Benjamin Shlaer·Jada Young
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Abstract

Chaplygin gas and other k-essence models exhibit emergent geometry, with perturbations propagating on an acoustic metric disformally related to the Einstein-frame metric. For superluminal sound speed, we identify the disformal metric as the "causal frame," since choosing a finite causal-frame lapse yields hyperbolic equations of motion for fields propagating in either frame. We show that with a phantom Chaplygin gas, the Einstein-frame lapse is forced to pass smoothly through zero and change sign while the causal-frame lapse remains positive. As a result, Einstein-frame degrees of freedom (including the scale factor) undergo spontaneous time-reversal while the Chaplygin gas evolves monotonically, enforcing a robust non-singular bounce even in the presence of additional matter canonically coupled to the Einstein frame.

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Brooke Berrios, Cameron Corley, Sky O'Donnell, Benjamin Shlaer, Jada Young. 2026-02-25. Geodesic completion of big bangs from emergent geometry. https://doi.org/10.1103/n6q5-16h5

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