Primordial black holes as DM? Introduction Constraints from P . - PowerPoint PPT Presentation

Primordial black holes as DM? P. Tinyakov Primordial black holes as DM? Introduction Constraints from P . Tinyakov compact stars Summary ULB, Brussels Original part is based on: Capela, Pshirkov, PT, PRD87 (2013) 023507 Capela, Pshirkov, PT, PRD87 (2013) 123524 Capela, Pshirkov, PT, PRD90 (2014) 083507 Defillon, Granet, PT, Tytgat, PRD90 (2014) 103522 Trieste, April 13-17, 2015

Primordial black holes Outline as DM? P. Tinyakov Introduction Constraints Introduction 1 from compact Production of PHB stars Existing astrophysical constraints Summary Constraints from compact stars 2 Capture of PBH in stars – during lifetime – at star formation Resulting constraints 3 Summary

Primordial black holes INTRODUCTION as DM? P. Tinyakov Introduction • Many (indirect) arguments suggest the existence of Production of PHB Existing dark matter with Ω DM ≃ 0 . 26 astrophysical constraints • Despite we are sure of the DM existence, we are Constraints from ignorant of its mass to an amazing degree — the compact stars uncertainty is 95 (!) orders of magnitude. Summary • The DM is often assumed to be a new stable particle: axion-like particle, sterile neutrinos, WIMPs, ... We will discuss here another possibility — that DM is composed of primordial black holes (PBH) Hawking, MNRAS 152 (1971) 75 • PBH interact very weakly with other matter and among themselves = ⇒ good DM candidate • Bonus: no new stable particles are needed.

Primordial black holes INTRODUCTION as DM? P. Tinyakov Introduction • Many (indirect) arguments suggest the existence of Production of PHB Existing dark matter with Ω DM ≃ 0 . 26 astrophysical constraints • Despite we are sure of the DM existence, we are Constraints from ignorant of its mass to an amazing degree — the compact stars uncertainty is 95 (!) orders of magnitude. Summary • The DM is often assumed to be a new stable particle: axion-like particle, sterile neutrinos, WIMPs, ... We will discuss here another possibility — that DM is composed of primordial black holes (PBH) Hawking, MNRAS 152 (1971) 75 • PBH interact very weakly with other matter and among themselves = ⇒ good DM candidate • Bonus: no new stable particles are needed.

Primordial black holes INTRODUCTION as DM? P. Tinyakov Introduction • Many (indirect) arguments suggest the existence of Production of PHB Existing dark matter with Ω DM ≃ 0 . 26 astrophysical constraints • Despite we are sure of the DM existence, we are Constraints from ignorant of its mass to an amazing degree — the compact stars uncertainty is 95 (!) orders of magnitude. Summary • The DM is often assumed to be a new stable particle: axion-like particle, sterile neutrinos, WIMPs, ... We will discuss here another possibility — that DM is composed of primordial black holes (PBH) Hawking, MNRAS 152 (1971) 75 • PBH interact very weakly with other matter and among themselves = ⇒ good DM candidate • Bonus: no new stable particles are needed.

Primordial black holes INTRODUCTION as DM? P. Tinyakov Introduction • Many (indirect) arguments suggest the existence of Production of PHB Existing dark matter with Ω DM ≃ 0 . 26 astrophysical constraints • Despite we are sure of the DM existence, we are Constraints from ignorant of its mass to an amazing degree — the compact stars uncertainty is 95 (!) orders of magnitude. Summary • The DM is often assumed to be a new stable particle: axion-like particle, sterile neutrinos, WIMPs, ... We will discuss here another possibility — that DM is composed of primordial black holes (PBH) Hawking, MNRAS 152 (1971) 75 • PBH interact very weakly with other matter and among themselves = ⇒ good DM candidate • Bonus: no new stable particles are needed.

Primordial black holes PRODUCTION OF PHB: as DM? P. Tinyakov BASICS Introduction Production of PHB Existing • The mass of PBH M PBH produced at a given time t astrophysical constraints (temperature T ) is limited by the horizon mass at this Constraints from time compact stars • In most of the models this is also an estimate of the Summary PBH mass • Horizon mass at temperature T : M H ≃ 0 . 02 M 3 Pl T 2 10 8 GeV T MeV 100 MeV 100 GeV 3 × 10 4 M ⊙ 3 × 10 − 6 M ⊙ 3 × 10 − 18 M ⊙ M H 3 M ⊙ 6 × 10 37 g 6 × 10 33 g 6 × 10 27 g 6 × 10 15 g

Primordial black holes PRODUCTION OF PHB: as DM? P. Tinyakov BASICS Introduction Production of PHB Existing • The mass of PBH M PBH produced at a given time t astrophysical constraints (temperature T ) is limited by the horizon mass at this Constraints from time compact stars • In most of the models this is also an estimate of the Summary PBH mass • Horizon mass at temperature T : M H ≃ 0 . 02 M 3 Pl T 2 10 8 GeV T MeV 100 MeV 100 GeV 3 × 10 4 M ⊙ 3 × 10 − 6 M ⊙ 3 × 10 − 18 M ⊙ M H 3 M ⊙ 6 × 10 37 g 6 × 10 33 g 6 × 10 27 g 6 × 10 15 g

Primordial black holes PRODUCTION OF PHB: as DM? P. Tinyakov BASICS Introduction Production of PHB Existing astrophysical constraints • To have all of DM composed of PBH today, at a time of Constraints from production only a small fraction f of the total energy compact stars density has to be converted into BH, Summary at T : ρ PBH = f ρ R • For the production at temperature T one has to have f = T eq ∼ eV T ≪ 1 T • = ⇒ Easy to have overproduction

Primordial black holes PRODUCTION OF PHB: as DM? P. Tinyakov BASICS Introduction Production of PHB Existing astrophysical constraints • To have all of DM composed of PBH today, at a time of Constraints from production only a small fraction f of the total energy compact stars density has to be converted into BH, Summary at T : ρ PBH = f ρ R • For the production at temperature T one has to have f = T eq ∼ eV T ≪ 1 T • = ⇒ Easy to have overproduction

Primordial black holes PRODUCTION MECHANISMS as DM? P. Tinyakov • From primordial density perturbations Introduction Carr, ApJ 201(1975)1 Production of PHB Existing • Need overdensities of ∼ 1. More precisely, for the astrophysical constraints equation of state Constraints p = γρ from compact stars one needs Summary δρ/ρ > γ at scales L of the order of horizon size at the production epoch. One typically has L ∼ R H M PBH ∼ M H • In case of (approximately) flat spectrum of perturbations, the PBH mass spectrum is extended. • Note: one needs to modify the primordial perturbation spectrum at very high multipole l . For instance, to produce M PBH ∼ M ⊙ the relevant l ∼ 10 8 .

Primordial black holes PRODUCTION MECHANISMS as DM? P. Tinyakov • From primordial density perturbations Introduction Carr, ApJ 201(1975)1 Production of PHB Existing • Need overdensities of ∼ 1. More precisely, for the astrophysical constraints equation of state Constraints p = γρ from compact stars one needs Summary δρ/ρ > γ at scales L of the order of horizon size at the production epoch. One typically has L ∼ R H M PBH ∼ M H • In case of (approximately) flat spectrum of perturbations, the PBH mass spectrum is extended. • Note: one needs to modify the primordial perturbation spectrum at very high multipole l . For instance, to produce M PBH ∼ M ⊙ the relevant l ∼ 10 8 .

Primordial black holes PRODUCTION MECHANISMS as DM? P. Tinyakov • From primordial density perturbations Introduction Carr, ApJ 201(1975)1 Production of PHB Existing • Need overdensities of ∼ 1. More precisely, for the astrophysical constraints equation of state Constraints p = γρ from compact stars one needs Summary δρ/ρ > γ at scales L of the order of horizon size at the production epoch. One typically has L ∼ R H M PBH ∼ M H • In case of (approximately) flat spectrum of perturbations, the PBH mass spectrum is extended. • Note: one needs to modify the primordial perturbation spectrum at very high multipole l . For instance, to produce M PBH ∼ M ⊙ the relevant l ∼ 10 8 .

Primordial black holes PRODUCTION MECHANISMS as DM? P. Tinyakov Introduction Production of PHB Existing • Soft equation of state at some period of evolution astrophysical constraints Carr, ApJ 201 (1975) 1 Constraints from Khlopov, Malomed, Zel’dovich, MNRAS 215 (1985) 575 compact stars Summary p = γρ ; γ → 0 • This gets rid of the pressure that opposes the collapse. Smaller amplitude initial perturbations may collapse into BH. • Typically period of “softness” is limited = ⇒ compact PBH mass spectrum centered at a value set by the corresponding horizon mass

Primordial black holes PRODUCTION MECHANISMS as DM? P. Tinyakov • Bubble collisions during phase transitions Introduction Hall, Hsu, PRL64 (1990) 2848 Production of PHB Existing Jedamzik, PRD55 (1997) 5871 astrophysical constraints Jedamzik, Niemeyer, PRD59 (1999) 124014 Constraints Bubble nucleation rate needs to be finely tuned from compact stars – if the rate is much larger than the expansion rate the Summary whole Universe undergoes the transition at once and there is no time to form BHs – if the rate is much smaller than the expansion rate the bubbles are rage and never collide = ⇒ One gets a compact spectrum with M BH ∼ M H For a QCD phase transition at T ∼ O ( 100 MeV ) one would get M BH ∼ M ⊙