Beyond CDM: ‘New’ DM candidates and structure formation Céline Boehm IPPP, Durham LAPTH, Annecy Oslo, 16th January 2015
LCDM forever? Planck 2013 Tegmark et al 2002 Are we stuck?
The `magic’ properties of WIMPs You don’t need to know the DM particle mass nor cross section (i.e. their particle properties) to make predictions s k 2 δ b − R − 1 ˙ θ b = k 2 ψ − H θ b + c ˙ θ b = k 2 ψ − H θ b + c 2 ˙ κ ( θ b − θ γ ) � 1 � 1 ⇥ θ γ = k 2 ψ + k 2 ˙ 4 δ θ γ = k 2 ψ + k 2 ˙ 4 δ γ − σ γ − ˙ κ ( θ γ − θ b ) , − ˙ κ ( θ γ − θ b ) − θ DM = k 2 ψ − H θ DM , ˙ θ DM = k 2 ψ − H θ DM ˙ So far observations are consistent with WIMPs too heavy to free-stream significantly too weakly interacting to damp fluctuations effects are expected at very small scales (but as V. Mukhanov said…beliefs are not enough!)
Exploring the parameter space in a systematic way guiding principle? Damping Free-streaming Collisional Damping
Free-streaming (damping) scale (astro-ph/0012504 , astro-ph/0410591 ) Z t nr Z t 0 Z t 0 v ( t ) dt... + dt... No interaction, tdec = “0”time; l fs = a ( t ) dt t dec t nr t dec This calculation only depends on the ⌘ − 4 / 3 ⇣ m DM moment where DM becomes non l struct ∼ 100 kpc keV relativistic so it only depends on the DM mass �;�::��2�:������������3�1�:�D�: �� �;�::��2�:������������3�1�:�D�: �� HDM 1 + ( α k ) 2 µ ⇤ − 5 /µ ⇥ T ( k ) = � 0 . 15 h � 1 . 3 Mpc i − 1 . 15 Ω DM h m DM α = 0 . 048 keV 0 . 4 0 . 65 h rin a
Primordial fluctuations can be used as a tracer very ! small !clumps ! + in !the !primordial ! Universe http://arxiv.org/abs/1404.7012 no !very ! ! WDM + small !clump ! in !the !primordial ! Universe see M. Viel 1306.2314 and many others
WDM candidates keV sterile neutrinos 2 Cold 0 Warm M2L25 − 2 log 10 (k 3 P(k)) − 4 − 6 − 8 − 10 1306.4954 − 12 − 4 − 2 0 2 log 10 (k/h Mpc − 1 ) 0812.0010 + 3.5 keV line gravitinos gravitinos as NLSP can explain a reduction of power 1412.4391 at dwarf scales and be compatible with LHC&BBN/CMB constraints
Sterile neutrino, gravitino all have extremely weak interactions Quid a realistic situation? depend on mass Z t 0 v ( t ) l fs = a ( t ) dt t dec depend on interactions depend on the history of the Universe Z t nr Z t nr Z t 0 v ( t ) v ( t ) c a ( t ) dt if t dec < t nr a ( t ) dt + a ( t ) dt if t dec < t nr t dec t nr t dec 3 parameters t dec , t nr , t eq Γ , m DM , t eq interaction !rate
Classification (astro-ph/0012504 , astro-ph/0410591 ) 3 parameters t dec , t nr , t eq Γ , m DM , t eq RegionIII 1 / Γ dec = t eq Γ RegionII RegionI t nr = t eq m DM to Z t nr Z t nr Z t 0 v ( t ) v ( t ) c a ( t ) dt if t dec < t nr a ( t ) dt + a ( t ) dt if t dec < t nr t dec t nr t dec
Free-streaming & Self-damping only (astro-ph/0012504 , astro-ph/0410591 ) self-interactions strong interactions WIMPS keV masses l fs ∝ m − 4 / 3 neutrino-like DM MeV
“Real” Physics once one adds interactions Both effects together! But collisional damping first. Collisional damping free-streaming A 3�2 !�(� Z t 0 Z t dec(dm − i) id ∼ 2 π 2 ρ i v 2 v l 2 i l fs = a ( t ) × dt dt ρ t a 2 Γ i 3 t dec 0 �:B2AB�A�������������A�3�;��3�1��2�::������� (astro-ph/0012504 , astro-ph/0410591 )
Collisional damping Translation in terms of Cosmological perturbations without DM interactions with DM interactions s k 2 δ b − R − 1 ˙ s k 2 δ b − R − 1 ˙ θ b = k 2 ψ − H θ b + c 2 ˙ κ ( θ b − θ γ ) θ b = k 2 ψ − H θ b + c 2 ˙ κ ( θ b − θ γ ) � 1 ⇥ � 1 ⇥ θ γ = k 2 ψ + k 2 ˙ 4 δ γ − σ γ θ γ = k 2 ψ + k 2 ˙ 4 δ γ − σ γ − ˙ κ ( θ γ − θ b ) , − ˙ κ ( θ γ − θ b ) − ˙ µ ( θ γ − θ DM ) , θ DM = k 2 ψ − H θ DM , ˙ θ DM = k 2 ψ − H θ DM − S − 1 ˙ ˙ µ ( θ DM − θ γ ) .
Implications for the Universe and Milky Way + 10 2 10 0 no !very ! ! P(k) [(h -1 Mpc) 3 ] small !clump ! 10 -2 in !the !primordial ! 10 -4 Universe 10 -6 CDM � CDM + 10 -8 WDM � CDM’ 10 -10 1 10 100 k [h Mpc -1 ]
In agreement with present observations, effects are just at the limit of our ability to test the matter power spectrum One can exclude some values of the elastic scattering cross sections works also with neutrinos possible model building and connection with neutrino masses hep-ph/0612228
Self-interactions 1405.2075 sDAO wDAO 1000 100 P H k L @H Mpc ê h L 3 D 1 P H k L @H Mpc ê h L 3 D m D = 1 GeV 0.01 m D = 1 TeV a D = 0.008 a D = 0.009 0.001 B D = 1 keV B D = 1 keV x 0 = 0.5 10 - 6 x 0 = 0.5 10 - 6 Self - Interacting DM Self - Interacting DM Warm DM Analogue Warm DM Analogue 10 - 10 10 - 9 Silk Damping Envelope Silk Damping Envelope Cold DM Cold DM 10 - 12 10 - 14 10 - 4 0.001 0.01 0.1 1 10 100 10 - 4 0.001 0.01 0.1 1 10 100 k @ h ê Mpc D k @ h ê Mpc D FIG. 1: Comparison between the linear matter power spectra as a function of wavenumber k for SIDM with a light mediator (here, dark atoms) and that of WDM with a free-streaming length comparable to the sound horizon of the former. We also display the standard matter power spectrum for cold collisionless dark matter as well as a fit to the Silk damping envelope of SIDM. The left panel displays the benchmark model for which r DAO � r SD (strong DAO), while the right panel shows the scenario for which r DAO ⇠ r SD (weak DAO). Here, ξ 0 ⌘ ξ ( T CMB , 0 ). core/cusp problem solved naturally… arXiv:1412.1477 The initial to introduce this …
self-interactions http://arxiv.org/pdf/1405.2075.pdf 1.5 CDM WDM 1 ν CDM γ CDM 0.5 ST (r top-hat) log 10 dn/dlnM [h 3 Mpc -3 ] ST (k top-hat) ST (r top-hat) + 0 Schneider correction -0.5 -1 -1.5 interactions with radiation M hm -2 http://arxiv.org/pdf/1412.4905.pdf -2.5 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 log 10 M vir [h -1 M ⊙ ]
Should we see deviations in the CMB? 10 4 40 10 3 TT / 2 � ] ( µ K 2 ) 20 2750 3000 3250 10 2 [l(l+1) C l ACT SPT 10 1 Planck WMAP-9 u = 10 -4 10 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 l http://arxiv.org/pdf/1309.7588.pdf Deviations may show at very small scale for CMB LSS constraints favour no observable deviation. BUT CMB DOES CONSTRAIN THE COSMO PARAMETERS!
Ultra light axions
(see Pedro Ferreira) 1110.0502 SDSS ACT FIG. 2: The matter power spectrum for three cosmolo- ) 3 ] gies shown with current measurements from SDSS [96], and P ( k )[( h − 1 Mpc ACT [63]. We show first the WMAP7 cosmology (dashed 4 10 black line). We also show two axion cosmologies, both with m a = 10 − 29 eV: f ax = 0 . 1 (solid blue line), and f ax = 0 . 01 (solid black line), with all other parameters held fixed at their WMAP7 values. Both axion cosmologies have only a small e ff ect on the CMB power spectrum, but are clearly distin- guished in their e ff ect on P ( k ), with f ax = 0 . 1 clearly ruled out by the data. − 2 − 1 10 10 − 1 ] k [ h Mpc 1110.0502 3 10 Λ CDM f ax = 0 . 1 , m a = 10 − 30 eV f ax = 0 . 1 , m a = 10 − 31 eV f ax = 0 . 01 , m a = 10 − 29 eV f ax = 0 . 01 , m a = 10 − 31 eV 1 2 3 10 10 10 ℓ
Decaying DM
Late or primordial times effect 1406.0527 Figure 2. Small-scale structure in a Milky Way mass halo (Z12) in CDM (left) and DDM models with Γ − 1 = 40 Gyr and V k = 100 km/s (middle) and Γ − 1 = 10 Gyr and V k = 20 km/s (right) within 260 kpc of the halo centers at z = 0 . The color scheme indicates the line-of-sight projected square of the density in order to emphasize the dense structures such as the host halo interiors and the associated subhalos. The DDM halos have slightly more diffuse central regions. The abundance and structure of subhalos are altered significantly compared to CDM in both of the DDM simulations presented. But if decay too fast, this becomes problematic you would see electromagnetic emission (unless you introduce 2 types of DM particles)
Is DM a particle? 1307.5458.pdf no DM particle found so far. Maybe DM is just a modification of gravity Probably! astro-ph/0505519 TeVeS not as good as DM It will get even worse! How to reproduce the 7-8 peaks seen by Planck & ACT/SPT(pol)?
Very heavy DM needs DM particles interacting ~100 times stronger than expected Too small cross section to be seen in LSS pure CDM and no signal to be seen in experiments (LHC???) life expectancy of heavy WIMP: forever (theory) / lost interest in ~5-10 years (unless breakthrough)
Recommend
More recommend
