# General Physics Colloquium - Fulvio Melia: "Zero Active Mass in FRW Cosmologies"

## Info about event

### Time

### Location

Fys. Aud.

## General Physics Colloquium

**Speaker: **

Fulvio Melia

University of Arizona

**Title: **

Zero Active Mass in FRW Cosmologies

**Abstract:**

The standard model of cosmology is based on the Friedmann-Robertson-Walker

(FRW) metric. Often written in terms of co-moving coordinates, this elegant and

highly practical solution to Einstein's equations is based on the Cosmological

principal and Weyl's postulate. But not all of the physics behind such symmetries

has yet been recognized. We invoke the fact that the co-moving frame also happens

to be in free fall to demonstrate that the FRW metric is apparently valid only for

a medium with zero active mass. In other words, the application of FRW appears

to require an equation-of-state rho+3p = 0, in terms of the total energy density

rho and total pressure p. Though the standard model is not framed in these

terms, the optimization of its parameters brings it ever closer to this constraint

as the precision of the observations continues to improve. For example, the

latest high-precision BAO measurements rule out the standard model at better

than the 99.95% C.L. if the zero active mass condition is ignored.

*Coffee and cake will be served at 14:05*