Why the Universe Decelerates: Mass Growth as the Cause of Negative Acceleration in Non-Equilibrium Dynamics

We show that in Non-Equilibrium Dynamics (NED), the present cosmic acceleration is

negative, and identify the physical cause: the growth of cosmic mass consumes the Planck-

scale repulsive force, leaving a negative residual for acceleration. Starting from the equation

of motion

M′

v + M a = F0,

we obtain

a =

F0 − M′R˙

M

.

Using the exact mass scaling M ∝ R(R−ℓp) and the matter-dominated expansion R ∝ t

2/3

,

we find

M′R˙

F0

=

4

3

> 1.

Therefore,

a = −

F0

3M

< 0.

The universe decelerates because mass growth consumes 4/3 of the repulsive force, leaving

−1/3 for acceleration. This result requires no dark energy. It is a falsifiable prediction in

direct conflict with the standard interpretation of Type Ia supernovae, CMB, and BAO. We

discuss the physical interpretation and the observational test.