Baryon masses in Wetterich's new cosmology Christoph Wetterich has put out a paper in which the universe isn't always expanding; it can be static or expanding just some of the time or even shrinking. And then there is an interaction which makes the masses of fundamental particles change in a complementary way, so as to preserve the properties of atoms, etc. 
Now here is what I don't understand. An electron gets its mass through the Higgs mechanism. A nucleon gets its mass through QCD effects. The quarks also get their masses from the Higgs mechanism and that makes a very small contribution to the nucleon mass, but mostly the nucleon mass arises in a different way. So I just don't see how any simple mechanism of varying mass can preserve e.g. the electron/proton mass ratio. Is this a tremendous problem for his theory, or is there something I have overlooked? 
 A: First a correction: Wetterich's paper doesn't say the universe is expanding or shrinking. All it says is that physics is invariant under scale changes and that a perspective in which the universe is static or shrinking (depending on the evolution stage) can lead to a simpler description. 
The scale change applied consists of applying a factor $\lambda$ to all lengths and all time intervals, a factor $1/\lambda$ to all masses, and a factor $\lambda^2$ to the gravitational coupling $G$. Such a rescaling induces a factor $1/\lambda$ scale change in all interactions (including the Higgs mechanism). All this boils down to is that in terms of a description of the physics in dimensionless parameters, the scale change should not incur any changes. 
A: Varying electron mass (via e.g. varying Higgs VEV) alone can cause red shift (reflected as the changed photon frequency while an electron jumps from one quantum state to another, with electron-mass-dependent orbiting energy levels) without resorting to the commonly accepted expanding universe scenario.
That being said, one must substitute the reduced mass for the mass of the electron to take into account the fact that the mass of the atomic nucleus is not actually infinite compared to the mass of the electron. The reduced mass reads
$$
\mu= \frac{M m_e}{M + m_e} = m_e\frac{1}{1 + \frac{m_e}{M}},
$$
where $M$ is the total mass of the nucleus.
Hence, in order to nudge the energy levels in a uniform way for different atoms, one is expecting to hold ratio $m_e/M$ constant. There are two ways to achieve this,


*

*A scale change is applied consistently to all length and time
intervals. Then the whole proposal amounts to an exercise of
rescaling. 

*The spontaneous symmetry breaking scales of electroweak symmetry
(Higgs mechanism) and quark chiral symmetry (NJL + Skyrmion?) are somehow in lockstep.

