Cosmic Hysteresis in $f(R)$ Gravity: A Thermodynamic Perspective on Cyclic Bouncing Universes

TL;DR

This paper explores how cosmic hysteresis arises in cyclic bouncing universes within $f(R)$ gravity, showing that scalar field dynamics induce thermodynamic irreversibility and cumulative cosmic evolution.

Contribution

It introduces a thermodynamic perspective to cyclic $f(R)$ cosmologies, deriving conditions for bounces and quantifying hysteresis effects in higher-curvature gravity models.

Findings

Hysteresis leads to non-zero work integral over cycles

Scalar-tensor dynamics cause asymmetric pressure evolution

Cumulative effects influence cosmic scale factor evolution

Abstract

We investigate the emergence of cosmic hysteresis in cyclic bouncing cosmologies within the framework of $f(R)$ modified gravity theories. Building upon previous studies that explored hysteresis phenomena in braneworld and Einstein-Gauss-Bonnet gravity, we analyze how scalar field dynamics coupled to a modified gravitational background generates asymmetric pressure evolution during expansion and contraction phases. This asymmetry manifests as a non-vanishing work integral over complete cosmic cycles, $\oint p\,dV \neq 0$, which we interpret as a fundamental thermodynamic signature of irreversible cyclic evolution. We derive the modified Friedmann equations for a representative $f(R) = R + \alpha R^2$ model, establish analytical conditions for bounce and turnaround events, and quantify the thermodynamic work performed during each cycle through comprehensive numerical analysis. Our findings demonstrate that hysteresis effects are generic features of scalar-tensor dynamics in higher-curvature gravity theories and can drive cumulative evolution of the cosmic scale factor across multiple cycles, potentially providing new insights into the resolution of cosmological singularities and the thermodynamic arrow of time in modified gravity frameworks.