Latest News from the Universe: LambdaWDM, CMB,Warm Dark Matter, Dark Energy, Neutrinos and Sterile Neutrinos

The new concordance model in agreement with observations: ΛWDM (Lambda-dark energy- Warm Dark Matter). Recently, Warm (keV scale) Dark Matter emerged impressively over CDM (Cold Dark Matter) as the leading Dark Matter candidate. Astronomical evidence that Cold Dark Matter (LambdaCDM) and its proposed tailored baryonic cures do not work at galactic and small scales is staggering. LambdaWDM solves naturally the problems of LambdaCDM and agrees remarkably well with the observations at galactic and small scales as well as large and cosmological scales. In contrast, LambdaCDM simulations only agree with observations at large scales. In the context of this new Dark Matter situation, which implies novelties in the astrophysical, cosmological, particle and nuclear physics context, the 18th Paris Colloquium 2014 is devoted to the Latest News from the Universe.

This Colloquium is within the astrofundamental physics spirit of the Chalonge School, focalised on recent observational and theoretical progress in the CMB, dark matter, dark energy, the new WDM framework to galaxy formation, and the effective theory of the early universe inflation with predictive power in the context of the LambdaWDM Standard Model of the Universe. The Colloquium addresses as well the theory and experimental search for the WDM particle physics candidates (keV sterile neutrinos). Astrophysical constraints including sterile neutrino decays points the sterile neutrino mass m around 2 keV or nearly larger. In summary, the aim of the meeting is to put together real data : cosmological, astrophysical, particle, nuclear physics data, and hard theory predictive approach connected to them in the framework of the LambdaWDM Standard Model of the Universe. Two observed quantities crucially constrain the DM nature in an inescapable way independently of the particle physics model: the average DM density rho and the phase space density Q. The observed values of rho and Q in galaxies today robustly point to a keV scale DM particle (WDM) and exclude CDM as well as axion Bose-Einstein condensate DM.

The fermionic quantum pressure of WDM ensures the observed small scale structures as the cores of galaxies and their right sizes (including the dwarf galaxies). N-body simulations in classical (non-quantum) physics do not take into account the fermionic quantum pressure of WDM and produce unreliable results at small scales: That is the reason of the too small core size problem in classical (non quantum) Nbody WDM simulations and its similar dwarf galaxies problem.

Lyman alpha bounds on the WDM particle mass apply only to specific sterile neutrino models and many sterile neutrino models are available today for which the Lyman alpha bounds are unknown. Therefore, WDM cannot be disfavoured in general on the grounds of the Lyman alpha bounds (only valid or specific models), as erroneously stated and propagated in the literature. Astrophysical constraints put the sterile neutrino mass m in the range 1< m <10 keV. Most of the constraints and last results points to m about 2 keV or nearly larger. MARE, KATRIN, ECHO and PTOLEMY experiments could detect such a keV sterile neutrino. It will be a fantastic discovery to detect dark matter in a beta decay or in electron capture. A exciting WDM work to perform is ahead of us.

The New Context today, the CDM and WIMP crisis and their decline: On large cosmological scales, CDM agrees in general with observations but CDM does not agree with observations on galaxy scales and small scales. Over most of twenty five years, increasing number of cyclic arguments and ad-hoc mechanisms or recipes (so called “baryonic solutions”) were-and continue to be- introduced in the CDM galaxy scale simulations, in trying to deal with the CDM small scale crisis: Cusped profiles and overabundance of substructures are predicted by CDM. Too many satellites are predicted by CDM simulations while cored profiles and no such overabundant substructures are seen by astronomical observations. Galaxy formation and evolution within CDM + baryonic models is increasingly confusing and and are plagued with always increasing tailoring, fine tuning and recipes.

On the CDM WIMP particle physics side, the situation is no less critical: So far, all the different and dedicated experimental searches after most of twenty five years to find the theoretically proposed CDM particle candidate (WIMP) have repeatedly failed. The CDM indirect searches (invoking CDM annihilation) to explain cosmic ray positron excesses, are in crisis as well, as wimp annihilation models are plagued with growing tailoring or fine tuning, and in any case, such cosmic rays excesses are well explained and reproduced by natural astrophysical process and sources. The so-called and continuously invoked ‘wimp miracle’ is nothing but being able to solve one equation with three unknowns (mass, decoupling temperature, and annihilation cross section) within the wimp models theoretically motivated by SUSY model building twenty five years ago (at that time those models were fashionable and believed for many proposals which is not anymore the case).

After more than twenty five years, and as often in big-sized science, CDM research (CDM+ baryon simulations, direct and indirect WIMP experimental research and model building),has by now its own internal inertia and own organized community, without reproducing the astronomical observations and failing to provide any experimental signal of wimps (except signals compatible with experimental noise). Growing CDM + baryon galactic simulations involve ever increasing large super-computers and large number of people working with, CDM particle wimp search involved (and involve) large and long-time planned experiments, huge number of people and huge budgets. One should not to be surprised then if a strategic scientific change have not yet operated in the CDM + baryon research and in the wimp research, given the way in which the organization operates, although their real scientific situation is of decline. Wimps are not the DM particle, DM is not Cold because the right DM particle is at the keV scale, DM is Warm.


  • Observational and theoretical progress on the nature of dark matter : keV scale warm dark matter
  • Cored density profiles in agreement with observations.
  • Large and small scale structure formation in agreement with observations at large scales and small (galactic) scales.
  • Warm (keV scale) dark matter from theory and observations.
  • The new quantum mechanical framework to galactic structure. WDM core sizes in agreement with observations.
  • The Thomas Fermi framework to describe the structure and physical states of galaxies in agreement with observations.
  • The DM distribution function and the equation of state of galaxies
  • Universal and non universal profiles. Cored density profiles with WDM core sizes in agreement with observations.
  • Supermassive Black Holes : Theory and Observations. The clarifing and unifying WDM framework for stars, galaxies and cosmology.
  • Warm (keV scale) dark matter N-body simulations in agreement with observations.
  • Neutrinos in astrophysics and cosmology.
  • The new serious dark matter candidate: Sterile neutrinos at the keV scale.
  • Active and sterile neutrinos mass bounds from cosmological data and from astrophysical and X ray data and from high precision beta decay experiments.
  • News on neutrinos and eV scale sterile neutrinos. News from reactor and accelerator experiments on neutrinos and their science implications.
  • Dark energy: cosmological constant: the quantum energy of the cosmological vacuum.Axions
  • The analysis of the CMB+LSS+SN data with the effective (Ginsburg-Landau) effective theory of inflation: New Inflation (double well inflaton potential) strongly favored by the CMB + LSS + SN data.
  • The presence of the lower bound for the primordial gravitons (non vanishing tensor to scalar ratio r) with the present CMB+LSS+SN data.
  • CMB news and polarization. Forecasts and last CMB data sets and. The new CMB + LSS data analysis including non-zero mass neutrinos and light sterile neutrinos..
  • and Other Topics…