Cosmological Hysteresis and the Cyclic Universe

Understand

A Universe filled with a homogeneous scalar field exhibits `Cosmological hysteresis'.

• Cosmological hysteresis is caused by the asymmetry in the equation of state during expansion and contraction.
• This asymmetry results in the formation of a hysteresis loop: $\oint pdV$, whose value can be non-vanishing during each oscillatory cycle.
• For flat potentials, a negative value of the hysteresis loop leads to the increase in amplitude of consecutive cycles and to a universe with older and larger successive cycles.