Is gravitino still a warm dark matter candidate?

At large scales and for sufficiently early times, dark matter is described as a pressureless perfect fluid-dust-non-interacting with Standard Model fields. These features are captured by a simple model with two scalars: a Lagrange multiplier and another playing the role of the velocity potential. That model arises naturally in some gravitational frameworks, e.g., the mimetic dark matter scenario. We consider an extension of the model by means of higher derivative terms, such that the dust solutions are preserved at the background level, but there is a non-zero sound speed at the linear level. We associate this Modified Dust with dark matter, and study the linear evolution of cosmological perturbations in that picture. The most prominent effect is the suppression of their power spectrum for sufficiently large cosmological momenta. This can be relevant in view of the problems that cold dark matter faces at sub-galactic scales, e.g., the missing satellites problem. At even shorter scales, however, perturbations of Modified Dust are enhanced compared to the predictions of more common particle dark matter scenarios. This is a peculiarity of their evolution in radiation dominated background. We also briefly discuss clustering of Modified Dust. We write the system of equations in the Newtonian limit, and sketch the possible mechanism which could prevent the appearance of caustic singularities. The same mechanism may be relevant in light of the core-cusp problem.

show abstract

“…The picture 2 is quite analogous to what one has in the case of WDM scenarios [50,51]. There are two important qualifications, however.…”

Section: Generic Casesupporting

confidence: 54%

Modified dust and the small scale crisis in CDM

Capela

Ramazanov

2015

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

show abstract

“…Compared to CDM, the WDM particle is much lighter, and therefore has more significant free-streaming. Popular candidates for WDM are the gravitino (Gorbunov et al 2008) and the (right-handed) sterile neutrino (Drewes 2013), with a Fermi-Dirac-like momentum distribution, which can yield the desired cut-off of the power spectrum at small scales. These are models that follow in the category of thermal relics, and this is the category that we will always implicitly assume in this paper.…”

Section: Introductionmentioning

confidence: 99%

Constraining the Nature of Dark Matter with the Star-formation History of the Faintest Local Group Dwarf Galaxy Satellites

Chau

Mayer

Governato

2017

ApJ

View full text Add to dashboard Cite

Λ warm dark matter (ΛWDM), realized by collisionless particles of 1-3 keV, has been proposed as an alternative scenario to Λ-Cold-Dark Matter (ΛCDM) for the dwarf galaxy scale discrepancies. We present an approach to test the viability of such WDM models using star-formation histories (SFHs) of the dwarf spheroidal galaxies (dSphs) in the Local Group. We compare their high-time-resolution SFHs with the collapse redshift of their dark halos in CDM and WDM. Collapse redshift is inferred after determining the subhalo infall mass. This is based on the dwarf current mass inferred from stellar kinematics, combined with cosmological simulation results on subhalo evolution. WDM subhalos close to the filtering mass scale, forming significantly later than CDM, are the most difficult to reconcile with early truncation of star formation (z 3). The ultra-faint dwarfs (UFDs) provide the most stringent constraints. Using six UFDs and eight classical dSphs, we show that a 1 keV particle is strongly disfavored, consistently with other reported methods. Excluding other models is only hinted for a few UFDs. Other UFDs for which the lack of robust constraints on halo mass prevents us from carrying out our analysis rigorously, show a very early onset of star formation that will strengthen the constraints delivered by our method in the future. We discuss the various caveats, notably the low number of dwarfs with accurately determined SFHs and the uncertainties when determining the subhalo infall mass, most notably the baryonic physics. Our preliminary analysis may serve as a pathfinder for future investigations that will combine accurate SFHs for local dwarfs with direct analysis of WDM simulations with baryons. Abstract Λ warm dark matter (ΛWDM), realized by collisionless particles of 1-3 keV, has been proposed as an alternative scenario to Λ-Cold-Dark Matter (ΛCDM) for the dwarf galaxy scale discrepancies. We present an approach to test the viability of such WDM models using star-formation histories (SFHs) of the dwarf spheroidal galaxies (dSphs) in the Local Group. We compare their high-time-resolution SFHs with the collapse redshift of their dark halos in CDM and WDM. Collapse redshift is inferred after determining the subhalo infall mass. This is based on the dwarf current mass inferred from stellar kinematics, combined with cosmological simulation results on subhalo evolution. WDM subhalos close to the filtering mass scale, forming significantly later than CDM, are the most difficult to reconcile with early truncation of star formation (z3). The ultra-faint dwarfs (UFDs) provide the most stringent constraints. Using six UFDs and eight classical dSphs, we show that a 1 keV particle is strongly disfavored, consistently with other reported methods. Excluding other models is only hinted for a few UFDs. Other UFDs for which the lack of robust constraints on halo mass prevents us from carrying out our analysis rigorously, show a very early onset of star formation that will strengthen the constraints delivered by our metho...

show abstract

“…Nevertheless, such low reheating temperatures have been considered [37], and Ref. [38] has examined an explicit low-reheat scenario in which a gravitino of mass mG ¼ 1-15 keV can have the right abundance to be the dark matter.…”

Section: B Nonstandard Early-universe Scenariosmentioning

confidence: 99%

Light gravitinos at colliders and implications for cosmology

2010

View full text Add to dashboard Cite

Light gravitinos, with mass in the eV to MeV range, are well motivated in particle physics, but their status as dark-matter candidates is muddled by early-Universe uncertainties. We investigate how upcoming data from colliders may clarify this picture. Light gravitinos are produced primarily in the decays of the next-to-lightest supersymmetric particle, resulting in spectacular signals, including di-photons, delayed and nonpointing photons, kinked charged tracks, and heavy metastable charged particles. We find that the Tevatron with 20 fb À1 and the 7 TeV LHC with 1 fb À1 may both see evidence for hundreds of light-gravitino events. Remarkably, this collider data is also well suited to distinguish between currently viable light-gravitino scenarios, with striking implications for structure formation, inflation, and other early-Universe cosmology.

show abstract

Is gravitino still a warm dark matter candidate?

Cited by 57 publications

References 69 publications

Modified dust and the small scale crisis in CDM

Modified dust and the small scale crisis in CDM

Constraining the Nature of Dark Matter with the Star-formation History of the Faintest Local Group Dwarf Galaxy Satellites

Light gravitinos at colliders and implications for cosmology

Contact Info

Product

Resources

About