P!mor"al Black Holes as. Dark Ma$er. Florian Kühnel. work in particular with Bernard Carr Katherine Freese Pavel Naselsky Tommy Ohlsson Glenn Starkman

Transcription

1 P!mor"al Black Holes as Dark Ma$er Florian Kühnel Talk at Particle and Astroparticle Theory Seminar Max Planck Institute for Nuclear Physics Heidelberg, November 20th, 2017 work in particular with Bernard Carr Katherine Freese Pavel Naselsky Tommy Ohlsson Glenn Starkman

2 PBH Generalities Black-hole (BH) formation for. Astrophysical: From down to, but not lower. Have a look at the density To form smaller black holes we need higher density Compare to cosmological density Formation at early times; primordial black holes (PBHs) Masses of primordial black holes:

3 Evaporation Black-hole radiation [Hawking 1974] Quantum Mechanics Thermodynamics General Relativity

4 PBH Formation Mechan%ms Formation of primordial black holes Cosmic string loops Bubble collisions Pressure reduction Large density perturbations scale of the over density Simple estimate: [Carr 1975] Jeans length by

5 PBH Probes of Scales Probe a huge range of scales: Quantum Gravity: Planck relics, Extra dimensions and higher-dimensional black holes, Early Universe: Baryogenesis, Nucleosynthesis, Reionisation, High-Energy Physics: Cosmological and galactic gammarays, Gravity: Critical phenomena, Cold dark matter, Dynamical effects, Lensing effects, Gravitational waves, Black holes in galactic nuclei,

6 PBH Some Numbers Consider an example of primordial black holes constituting all of the dark matter: Mass range: Size: Number in our Galaxy: Distance:

7 PBH Con&raints at Formation Note that Planck LSP Entropy GRB PBH QSO WB MACHO FIRAS DF LSS WMAP3 and hence BBN CMB Galactic EGB 21cm log 10 (M/g) GW [Carr et al. 2010] * *(more recent) constraints for the presently allowed dark-matter fraction later

8 More on PBH Formation Given the density distribution, derive the PBH density parameter: variance In the Gaußian case primordial black holes If furthermore, we find that the fraction of collapsed universes becomes separate universes

9 P!mor"al Black Holes Observed? Milestone detection of gravitational waves by LIGO Confirmation of two merging black holes (GW150914, (GW151226, ) Masses for all BHs: Could be PBHs! [Bird et al. 2016]

10 C!tical Collapse Usually: Assume horizon mass Critical scaling: [Choptuik 93] density contrast Radiation domination: [Miller et al. 2004]

11 C!tical Collapse How would this look for monochromatic mass function? dark-matter fraction f M/M 1 1 [Carr, FK, Sandstad 2016]

12 C!tical Collapse How would this look for monochromatic mass function? dark-matter fraction f It is simply impossible to get a monochromatic spectrum! M/M 1 1 [Carr, FK, Sandstad 2016]

13 More Sy&ematic Study [Green 2016]

14 Extended Mass Spectra and Con&raints We applied this extended mass function to this constraint curtain :* f EG F WD NS K *including forecasts; *( more on bounds later ) ML mlq PT τ M/M [FK, Freese 2017]

15 More Sy&ematic Study Results 2.0 Log 10 (f) σ f Log 10 (M f /M ) [FK, Freese 2017]

16 More Sy&ematic Study O)er s Results With partly different constraints: 6 lognormal σ 3 σ log 10 (M c /M ) [Carr et al. 2017] 0-1

17 More Sy&ematic Study O)er s Results 1) A good understanding of the lognormal 6 6 With partly different constraints: physics of the constraints is 5 4 extremely important! 5 4 σ 3 2) It is crucial to re-derive the 2 constraints for (the realistic(!) case) 1 of extended mass functions! log 10 (M c /M ) σ [Carr et al. 2017]

18 Non-Sphe!cal Effects [FK, Sandstad 2017]

19 Non-Sphe!cal Effects Non-Sphericity ellipsoidal threshold spherical threshold Spherical κ = 0.47; γ = 0.62 κ = 0.65; γ = κ = 1.61; γ = 0.5 β Eq 10-5 [FK, Sandstad 2016] 10-7 ellipticity prolateness M/M 1 1 Simple estimate: As the collapse starts along shortest axis first, consider collapse of largest enclosed sphere (green curve):

20 Non-Sphe!cal Effects Non-Sphericity ellipsoidal threshold Spherical κ = 0.47; γ = 0.62 κ = 0.65; γ = κ = 1.61; γ = 0.5 β Eq Even slight non-sphericity spherical threshold 10-5 reduces the abundance of 10-7 [FK, Sandstad 2016] ellipticity PBHs significantly! prolateness M/M 1 1 Simple estimate: As the collapse starts along shortest axis first, consider collapse of largest enclosed sphere (green curve):

21 Gravitational Waves form PBHs Like ordinary black holes, PBHs can emit gravitational waves. Roughly, there are two types of signals: 1) From early formation of PBH binaries (three-body process!). Starts being significant in the formation of first caustics. Need N-body simulations! Characteristic stochastic gravitational-wave background gw 1 critical density number of events c c 2 2) From late formation of PBH binaries. Z [FK, Mohayaee, Naselsky, von Hausegger; to appear soon] dz N(z) 1+z r E gw d r gravitational-wave energy per event r = (1+z) [Phinney 2001]

22 Gravitational Waves form PBHs If PBHs constitute a significant fraction of the dark matter, at the center of our Galaxy one would have a very large number of PBH inspiralling into SgrA*. Stochastic enhancement; Detection forecasts for LISA: f DM macros only PBHs & macros m / M 11 [FK, Freese, Starkman, Matas 2017]

23 Gravitational Waves form PBHs If PBHs constitute a significant fraction of the dark matter, at the center of our Galaxy one would have a very large number of PBH inspiralling into SgrA*. Stochastic enhancement; Detection forecasts for LISA: LISA will be a splendid PBH dark-matter detection machine!* f DM *If there is a substantial fraction of macroscopic dark matter macros PBHs & macros only m / M 11 [FK, Freese, Starkman, Matas 2017]

24 PBH & Pa,icle Dark Ma$er Study a combined scenario: DM = PBHs + Particles The latter will be accreted by the former. As an example, focus on sterile neutrinos: Decays with rates: *works also for UCMHs The fluxes are quite significant with small average distances: [FK, Ohlsson 2017*] (*accepted for publication in PRD)

25 PBH & Pa,icle Dark Ma$er Hence, these objects possibly pass close by a detector.,,, [FK, Ohlsson 2017*] (*accepted for publication in PRD)

26 PBH & Pa,icle Dark Ma$er Let us now study WIMP annihilations in PBH halos: The annihilation rate / n 2. Halo profile does matter; enhancement of in density spikes. 1) We derive the density profile of the captured WIMPs, 2) calculate the annihilation rate, 3) and compare to data: [Boucenna, FK, Ohlsson, [Visinelli; to appear very soon]

27 PBH & Pa,icle Dark Ma$er Let us now study WIMP annihilations in PBH halos: The annihilation rate / n 2. Halo profile does matter; enhancement of in density spikes. 1) We derive the density profile of the captured WIMPs, 2) calculate the annihilation rate, 3) and compare to data: h vi = cm 3 /s [Boucenna, FK, Ohlsson, [Visinelli; to appear very soon]

28 PBH & Pa,icle Dark Ma$er Let us now study WIMP annihilations in PBH halos: The annihilation rate / n 2. Halo profile does matter; enhancement of in density spikes. 1) We derive the density profile of the captured WIMPs, 2) calculate the annihilation rate, 3) and compare to data: EG F NS K ML E W - HSC [Boucenna, FK, Ohlsson, [Visinelli; to appear very soon]

29 PBH & Pa,icle Dark Ma$er 1) We derive the density profile of the captured WIMPs, 2) calculate the annihilation rate, 3) and compare to data: EG F NS K ML E W - HSC [Boucenna, FK, Ohlsson, [Visinelli; to appear very soon]

30 PBH & Pa,icle Dark Ma$er 1) We derive the density profile of the captured WIMPs, 2) calculate the annihilation rate, 3) and compare to data: EG F NS K ML E W - HSC h vi = cm 3 /s PRELIMINARY [Boucenna, FK, Ohlsson, [Visinelli; to appear very soon]

31 PBH & Pa,icle Dark Ma$er 1) We derive the density profile of the captured WIMPs, 2) calculate the annihilation rate, 3) and compare to data: EG F NS K ML E W - HSC h vi = cm 3 /s PRELIMINARY [Boucenna, FK, Ohlsson, [Visinelli; to appear very soon]

32 Sad or Ha-y? Are these sad prospects for a PBH-WIMP coalition? [ ci102l-w1024/scheitern-der-jamaika-sondierungen.jpg]

33 Sad or Ha-y? or should we be happy? ci102l-w1024/christian-lindner-head-of-the-free.jpg]

34 Sad or Ha-y? or should we be happy? Keep smiling, by choosing well ci102l-w1024/christian-lindner-head-of-the-free.jpg] your coalition partner.

35 Con&raints Words of Caution May constraints rely on rather on uncertain, restrictive, simplistic or even incorrect assumptions! Validity of Hawking radiation log 10 fpbh Evaporation FL WD NS monochromatic K EROS M Planck WB Eri II Accretion models uncertain HSC Assumes a far too large DM density in globular clusters log 10 (M c /M ) Ignore clustering Seg I [Carr et al. 2017]

36 More Words of Caution One may wonder how the constraints on the PBH dark-matter fraction constrain the primordial power spectrum. M/M 11 Go back to the constraints at the time of formation: β' Neutron stars Evaporation Micro lensing WB DF M/g 11

37 More Words of Caution These constraints naïvely translate to: P δ M/M 1 1

38 More Words of Caution drawing in the power spectrum of a running-mass model, which is perfectly d accord with the mentioned constraints: P δ critical collapse M/M 1 1

39 Con&raints on. P!mor"al Power Spectrum? Moreover, take the uncertainty due to non-sphericities into account: non-sphericities P δ apple 1 critical collapse M/M 1 1 [Akrami, FK, Sandstad 2017]

40 Con&raints on. P!mor"al Power Spectrum? Moreover, take the uncertainty due to non-sphericities into account: The primordial power spectrum non-sphericities P δ is essentially not constraint from current apple 1 constraints on the PBH abundance! critical collapse M/M 1 1 [Akrami, FK, Sandstad 2017]

41 Conclusion Primordial black holes are very interesting! They are unique probes of their formation scenarios. They could provide the entire dark matter. A detailed understanding their formation is crucial. Extended mass spectra require special care when comparing to constraints. Most these constraints rely on rather unconfirmed assumptions. LISA might detect PBHs! Also, combined dark-matter scenarios (PBHs + WIMPs or sterile neutrinos) might be well constraint in the near future.