Dual Time Cosmology: A Unified Framework and Comparison with ΛCDM

Abstract We explore a cosmological framework positing a reciprocal relationship between spatial expansion and the flow of time: as the Universe’s expansion accelerates, an absolute cosmic time dimension slows in its passage (and could even reverse direction), while the local time experienced by observers remains as normally perceived. In this dual-time model, time has two aspects: a global Absolute Time T abs that parametrizes the Universe’s evolution and progressively slows relative to observers, and the usual observer-relative time t that corresponds to the proper time measured by comoving observers. We formalize this idea by introducing a modified Friedmann–Lemaître–Robertson–Walker (FLRW) metric in which T abs and t coexist, related by a dynamic lapse function. Using this metric and the Friedmann equations, we derive how accelerated expansion in space is concomitant with a deceleration of T abs , and show that many cosmological observations normally attributed to dark energy can be reinterpreted as consequences of this time deformation. In particular, an apparent acceleration of the expansion arises for t-time observers even if the expansion in T abs is decelerating (e.g. a matter-only universe). Thus, the empirical evidence for cosmic acceleration can be explained without dark energy, by recognizing it as an “illusion” caused by using the relative time t instead of the underlying T abs. We discuss how this dual-time picture mirrors the philosophical duality between Einstein’s realism and the Copenhagen interpretation of quantum mechanics: T abs provides an objective, observer-independent temporal order (analogous to an absolute time or a hidden variable), while t represents the subjective, observer-dependent experience of time. In this view, cosmic acceleration is not due to a new energy component, but is a manifestation of time’s twofold nature.