Cosmology as Thermodynamics without CP and Dark Energy

The basic cosmology model is the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric expressing Einstein's field equations in the special case of an isotropic and homogeneous universe according to the Cosmological Principle (CP) stating that no place or direction is better than another, in the form of (i) Friedmann's equation, combined with a (ii) fluid equation.

Friedmann's equation expresses (i) conservation of kinetic energy + gravitational energy, and the fluid equation expresses (ii) conservation of internal energy (heat energy), and thus the FLRW model is nothing but an expression of the basic laws of thermodynamics under the CP of an isotropic and homogeneous universe.

FLWR/CP predicts that the expansion of the universe should slow down by gravitation, and this is the background to the 2011 Nobel Prize of physics for observations of instead acceleration. The Prize is given for the surprising observation that FLWR/CP is wrong!

But is it surprising that FLWR/CP is wrong? Is it surprising if CP is not valid? Of course not!

CP is a incredibly strong assumption and FLWR is an incredibly simplistic model. There is no real reason to believe that such a simple model could say anything correct about the expansion of the universe.

The Noble Prize is thus awarded for the observation that an incredibly simple model of the universe is not correct at all. This is surprising.

Even more surprising is that based on this incredibly simple model and observations that the incredibly simple model is not at all correct, the conclusion is drawn that there is a completely unknown new form of energy named dark energy which is needed to make the simplistic incorrect model less simplistic and incorrect.

But there is another more reasonable conclusion to draw and this is to see what thermodynamics without CP can tell about the universe, maybe without any need to invent any completely new form of energy named dark energy.

This connects to previous posts on dark energy and will be the subject of upcoming posts.