Morgan Le Delliou

The Abell cluster A586 and the detection of violation of the equivalence principle

We discuss the current bounds on the Equivalence Principle (EP), in particular from structure formation and, reexamine in this context, the recent claim on the evidence of the interaction between dark matter and dark energy in the Abell Cluster A586 and the ensued violation of the EP.

Dark Energy‐Dark Matter Interaction from the Abell Cluster A586 and violation of the Equivalence Principle

We find that the Abell Cluster A586 exhibits evidence of the interaction between dark matter and dark energy and argue that this interaction suggests evidence of violation of the Equivalence Principle. This violation is found in the context of two different models of dark energy‐dark matter interaction.

Local conditions separating expansion from collapse in spherically symmetric models with anisotropic pressures

The authors wish to thank the anonymous referee for many enlightening comments and suggestions and Jose Fernando Pascual-Sanchez for helpful discussions. M. Le D. also wishes to thank Michele Fontanini, Daniel Guariento and Elcio Abdalla for helpful discussions. The work of M. Le D. has been supported by CSIC (JAEDoc072), CICYT (FPA2006-05807) in Spain and FAPESP (2011/24089-5) in Brazil. F.C.M. thanks CMAT, Univ. Minho, for support through FEDER Funds COMPETE and FCT Projects No. Est-C/MAT/UI0013/2011, No. PTDC/MAT/108921/2008 and No. CERN/FP/123609/2011. M. Le D. and J. P. M. acknowledge the CAAULs Project No. PEst-OE/FIS/UI2751/2011. J. P. M. also wishes to thank FCT for Grants No. CERN/FP/123615/2011 and No. CERN/FP/123618/2011.

Separating expansion from contraction in spherically symmetric models with a perfect fluid: Generalization of the Tolman-Oppenheimer-Volkoff condition and application to models with a cosmological constant

We investigate spherically symmetric perfect-fluid spacetimes and discuss the existence and stability of a dividing shell separating expanding and collapsing regions. We perform a 3+1 splitting and obtain gauge invariant conditions relating the intrinsic spatial curvature of the shells to the Misner-Sharp mass and to a function of the pressure that we introduce and that generalizes the Tolman-Oppenheimer-Volkoff equilibrium condition. We find that surfaces fulfilling those two conditions fit, locally, the requirements of a dividing shell, and we argue that cosmological initial conditions should allow its global validity. We analyze the particular cases of the Lemaitre-Tolman-Bondi dust models with a cosmological constant as an example of a cold dark matter model with a cosmological constant ({Lambda}-CDM model) and its generalization to contain a central perfect-fluid core. These models provide simple but physically interesting illustrations of our results.

Separating expansion and collapse in general fluid models with heat flux

The work of M. Le D. has been supported by CSIC (JAEDoc072), CICYT (FPA2006-05807) in Spain and FAPESP (2011/24089-5) in Brazil. F. C. M. thanks CMAT, Universidade Minho, for support through FEDER Funds COMPETE, FCT Projects No. Est-C/MAT/UI0013/2011, No. PTDC/MAT/108921/2008, No. CERN/FP/123609/2011, and also Instituto de Fisica, UERJ, Rio de Janeiro, for hospitality. M. LeD. and J. P. M. acknowledge the CAAULs Project No. PEst-OE/FIS/UI2751/2011. J. P. M. also wishes to thank FCT for Grants No. CERN/FP/123615/2011 and No. CERN/FP/123618/2011. M. F. is supported by FAPESP Grant No. 2011/11365-4, D. C. G. is supported by FAPESP Grant No. 2010/08267-8, and E. A. is supported by FAPESP and CNPq.

Testing the interaction of dark energy to dark matter through the analysis of virial relaxation of clusters Abell clusters A586 and A1689 using realistic density profiles

Interaction between dark energy and dark matter is probed through deviation from the virial equilibrium for two relaxed clusters: A586 and A1689. The evaluation of the virial equilibrium is performed using realistic density profiles. The virial ratios found for the more realistic density profiles are consistent with the absence of interaction.

The role of shell crossing on the existence and stability of trapped matter shells in spherical inhomogeneous \Lambda-CDM models

We analyse the dynamics of trapped matter shells in spherically symmetric inhomogeneous \Lambda-CDM models. The investigation uses a Generalised Lemaitre-Tolman-Bondi description with initial conditions subject to the constraints of having spatially asymptotic cosmological expansion, initial Hubble-type flow and a regular initial density distribution. We discuss the effects of shell crossing and use a qualitative description of the local trapped matter shells to explore global properties of the models. Once shell crossing occurs, we find a splitting of the global shells separating expansion from collapse into, at most, two global shells: an inner and an outer limit trapped matter shell. In the case of expanding models, the outer limit trapped matter shell necessarily exists. We also study the role of shear in this process, compare our analysis with the Newtonian framework and give concrete examples using density profile models of structure formation in cosmology.

Separating expansion from contraction and generalizing TOV condition in spherically symmetric models with pressure

We investigate spherically symmetric solutions with pressure and discuss the existence of a dividing shell separating expanding and collapsing regions. We perform a 3+1 splitting and obtain gauge invariant conditions relating not only the intrinsic spatial curvature of the shells to the ADM mass, but also a function of the pressure which we introduce that generalises the Tolman‐Oppenheimer‐Volkoff equilibrium condition. We consider the particular case of a Lemaitre‐Tolman dust models with a cosmological constant (a Λ‐CDM model) as an example of our results. illustrations of our results.

Spherically symmetric models: Separating expansion from contraction in models with anisotropic pressures

We investigate spherically symmetric spacetimes with an anisotropic fluid and discuss the existence and stability of a dividing shell separating expanding and collapsing regions. We find that the dividing shell is defined by a relation between the pressure gradients, both isotropic and anisotropic, and the strength of the fields induced by the Misner-Sharpe mass inside the separating shell and by the pressure fluxes. This balance is a generalization of the Tolman-Oppenheimer-Volkoff equilibrium condition which defines a local equilibrium condition, but conveys also a non-local character given the definition of the Misner-Sharpe mass. We present a particular solution with dust and radiation that provides an illustration of our results.

Dynamical quintessence fields’ Press–Schechter mass function: detectability and effect on dark haloes

We present investigations on the influence of dynamical quintessence field models on the formation of non-linear structures. In particular, we focus on the structure traced by the mass function. Our contribution builds on previous studies by considering two potentials not treated previously and investigating the impact of the free parameters of two other models. Our approach emphasizes the physical insight into the key role of the evolution of the equation of state: we use the variations in the spherical non-linear collapse caused by quintessence as a function of the models potential in a Press–Schechter scheme to obtain the differences in halo mass functions. The comparison is also done with the more usual scenario ΛCDM. We conclude that the key role lies within the evolution of the equation of state and that the method displays promise for discrimination using cluster mass determination by upcoming surveys.