1. The Stability Issue In Models Of Neutrino Dark Energy
by Ole Bjælde
with
A. Brookfield, C. van de Bruck, S. Hannestad,
D. Mota, L. Schrempp, & D. Tocchini-Valentini
Wednesday Cosmo07 Brighton

2. Mass Varying Neutrinos =MaVaNs
Coupling between  and a scalar field 
Conservation of energy
Equations of motion
Fardon, Nelson
& Weiner, 2003

3. Assuming adiabaticity
MaVaNs
Mass Varying Neutrinos
=MaVaNs
NR limit
Assuming adiabaticity

4. MaVaNs
MaVaN-
candidates
Candidate potentials must obey w~-1

5. MaVaNs
Coleman-Weinberg

6. MaVaNs
Power-Law

7. Cosmological Perturbation Theory
Evolution of structures from Big Bang
Perturbations grow because of gravity

8. Stability Dynamics of perturbations governed by
General sound speed described by
MaVaNs
Adiabatic scale

9. Stability Stable MaVaN model-perturbations driven by
Generalising to 3 neutrino generations with a degenerate mass spectrum
Takahashi & Tanimoto, 2003

10. Perturbation Analysis
Perturbations
Perturbation Analysis
Synchronous gauge
Friedmann
Neutrino-e.o.m.

11. Results
Results: C-W

12. Results
Results: Power

13. Conclusion MaVaNs can act as dark energy
Dynamics of MaVaN-perturbations depend crucially on 
Instability in cases of steeply growing 
It is possible to have a stable model!
Ridiculeously small growth in neutrino mass