Astrophysics meets particle physics in search ofblack holes
produced in the Big Bang
Alexander Kusenko(UCLA and Kavli IPMU)
ISCO-2023

Supported by U.S. DOE Office of Science (HEP), and WPI, Japan

Nobel Prize 2020: Black holes’ existence conﬁrmed
Milky Way, Sagittarius A*
M=4x106 M☉

R. Penrose
R. Genzel
A. Ghez

Observations: BHs exist!
⇒PBH is a plausible
dark matter candidate,the only candidate
known to exist in nature

Experimental constraints
A - Dark matter [Murayama, Melia]
B - candidate events from HSC, OGLE
[1701.02151, 1901.07120]
C - interesting for GW, as well astransmuted NS -> BH population[1707.05849; 2008.12780]

DCarr, Kuhnel [2006.02838]

D - seeds of supermassive black holes[astro-ph/0204486,
arXiv:1202.3848, 2008.11184]

First candidate eventsFirst candidate eventsfrom HSC and OGLE
[Niikura et al.. Nature Astron.][Takada et al., IPMU]

Sugiyama

How to make PBHs
Need a ~30% or higher overdensity earlyenough in the history of the universe.
●●●●●

Primordial ﬂuctuations enhanced on
small scales (inﬂation model)
Yukawa interactions, “long-range”
forces, radiative cooling => PBH
Supersymmetry: Q-balls as building
blocks of PBH
Supersymmetry: Q-balls withlong-range scalar forcesMultiverse => PBHs

America's Test Kitchen

horizon

PBH

horizon size on your screen
corresponds to T ~ 102-103 GeV

How to make PBHs
Need a ~30% or higher overdensity earlyenough in the history of the universe.
●●●●●

Primordial ﬂuctuations enhanced onsmall scales (inﬂation model) Sasaki
Yukawa interactions, “long-range”
forces, radiative cooling => PBH
Supersymmetry: Q-balls as building
blocks of PBH
Supersymmetry: Q-balls withlong-range scalar forcesMultiverse => PBHs

America's Test Kitchen

horizon

PBH

horizon size on your screen
corresponds to T ~ 102-103 GeV

How to make PBHs
Need a ~30% or higher overdensity earlyenough in the history of the universe.
●
●
●
●
●

Primordial ﬂuctuations enhanced on
small scales (inﬂation model)
Yukawa interactions, “long-range”
forces, radiative cooling => PBH
Supersymmetry: Q-balls as building
blocks of PBHSupersymmetry: Q-balls withlong-range scalar forcesMultiverse => PBHs

America's Test Kitchen

PBHhorizon

horizon size on your screen
corresponds to T ~ 102-103 GeV

PBH formation mechanism: Yukawa “ﬁfth force”
Yukawa interactions:a heavy fermion interactingwith a light scalar

A light scalar ﬁeld ⇒ long-range attractive force, ⇒stronger than gravity

instability similar to
gravitational instability,
only stronger⇒ halos form even in radiation dominated universe[Amendola et al., 1711.09915; Savastano et al., 1906.05300; Domenech, Sasaki, 2104.05271]

Same Yukawa coupling provides a source of radiative cooling by emission ofgravitational radiation ⇒ halos collapse to black holes[Flores, AK, 2008.12456, PRL 126 (2021) 041101; 2008.12456]

Strong long-range force: instability and structure formationenergy density perturbations (radiation)

density perturbations of a kinetically decoupled particle⇒
p = huge ⇒[Flores, AK, 2008.12456, PRL]

fast growth, even in the radiation-dominated era!

Growth of structures due to Yukawa force: N-body simulations
Inman, PRELIMINARY
Domenech, Inman,Sasaki, AK
work in progressRapid growth of structures… plus radiative cooling!
Same Yukawa ﬁelds allow particles moving with acceleration emit scalar waves⇒ radiative cooling and collapse to black holes

Flores, AK, Phys.Rev.Lett. 126 (2021) 4, 041101;
2008.12456

PBH DM abundance natural for m𝝍~1-100 GeV
Asymmetric dark matter models: Asymmetry in the dark sector = baryon asymmetry
In our case, all these particles end up in black holes:[Flores, AK, 2008.12456, PRL 126 (2021) 041101]
Natural explanation for the ratio(dark matter density) / (ordinary matter density)for ~1-100 GeV masses

Similar to asymmetric dark matter

How to make PBHs
Need a ~30% or higher overdensity earlyenough in the history of the universe.
●

●
●
●
●

America's Test Kitchen

Primordial ﬂuctuations enhanced on
small scales (modify inﬂation)
Yukawa interactions, “long-range”
forces, radiative cooling => PBH
Supersymmetry: Q-balls as building
blocks of PBH
Supersymmetry: Q-balls withlong-range scalar forcesMultiverse => PBHs

PBHhorizon

horizon size on your screen
corresponds to T ~ 102-103 GeV

Scalar ﬁelds in de Sitter space (used by Affleck-Dine)
A scalar with a small mass develops a VEV[Chernikov, Tagirov; Starobinsky, Zeldovich; Bunch, Davies; Linde; Aﬄeck, Dine; Starobinsky, Yokoyama]
4

Scalar ﬁelds in de Sitter space (used by Affleck-Dine)
A scalar with a small mass develops a VEV[Chernikov, Tagirov; Starobinsky, Zeldovich; Bunch, Davies; Linde; Aﬄeck, Dine; Starobinsky, Yokoyama]
4

Scalar ﬁelds: an instability (Q-balls)
Gravitational instability can occurs due to theattractive force of gravity.
Similar instability can occur due to scalarself-interaction which is attractive:
or[AK, Shaposhnikov, hep-ph/9709492]

Scalar ﬁelds: an instability (Q-balls)⇒ growing modes: 0<k<kmax
Also of interest: oscillons

AK, Shaposhnikov, hep-ph/9709492

Numerical simulations of scalar ﬁeld fragmentation
SUSY Q-balls

Affleck - Dine baryogenesis (SUSY): scalars are ﬂat directions

Inﬂationorigin ofprimordial
perturbations

radiation dominatedmatter dominatedp=(⅓) ρρ∝a-4p=0
ρ∝a-3

structures don’t growstructures growmodern era(dark energydominated)Scalar lump (Q-ball) formation can lead to PBHs
Early matter
dominated epoch
in the middle ofradiation
dominated era[Cotner, AK,Phys.Rev.Lett. 119(2017) 031103 ]Size of “particles” affects Poisson ﬂuctuations

many small particles ⇒small (poisson) ﬂuctuations

few GIANT PARTICLES⇒LARGE POISSON FLUCTUATIONSAffleck-Dine process and scalar fragmentation in SUSY
[Cotner, AK, Sasaki, Takhistov et al.,1612.02529, 1706.09003, 1801.03321, 1907.10613]
Flat directions lifted by SUSY breaking
terms, which determine the scale of fragmentation.

Cotner, AK, Phys.Rev.Lett. 119 (2017) 031103
Cotner, AK, Sasaki, Takhistov, JCAP 1910 (2019) 077

How to make PBHs
Need a ~30% or higher overdensity earlyenough in the history of the universe.
●

●
●
●
●

America's Test Kitchen

Primordial ﬂuctuations enhanced on
small scales (modify inﬂation)
Yukawa interactions, “long-range”
forces, radiative cooling => PBH
Supersymmetry: Q-balls as building
blocks of PBH
Supersymmetry: Q-balls withlong-range scalar forcesMultiverse => PBHs

PBHhorizon

horizon size on your screen
corresponds to T ~ 102-103 GeV

Yet another way to get PBHs from SUSY: long-range forces
A SUSY ﬂat direction 𝝋 can couple to another SUSY scalar, 𝝌, which can mediate long-range
forces between SUSY Q-balls, leading to Yukawa long-range potential

Long-range forces
work as in the case ofYukawa interaction
but
individual Q-balls
grow until they reachthe mass/size of a BH

Flores, AK, 2108.08416

How to make PBHs
Need a ~30% or higher overdensity earlyenough in the history of the universe.
●●●●Primordial ﬂuctuations enhanced on
small scales (modify inﬂation)
Yukawa interactions, “long-range”
forces, radiative cooling => PBH
Supersymmetry: Q-balls as building
blocks of PBH
Supersymmetry: Q-balls withlong-range scalar forcesMultiverse => PBHs

America's Test Kitchen

PBH
horizonhorizon size on your screen
corresponds to T ~ 102-103 GeV

And yet another mechanism: inﬂationary multiverse

Tunneling events lead to nucleation of baby universes, which appear to outside
observer as black holes.
Deng, Vilenkin JCAP 12 (2017) 044
AK, Sasaki, Sugiyama, Takada, Takhistov, Vitagliano, Phys Rev Lett 125 (2020) 181304

Tail of the mass the function ∝M-1/2, accessible to HSC[AK, Sasaki, Sugiyama, Takada, Takhistov, Vitagliano, Phys.Rev.Lett. 125 (2020) 181304
arXiv:2001.09160]

PBH masses, spins, and a new window on the early universe
Formation mechanism

Mass range

PBH spin

Inflationary perturbations[review: 2007.10722]

DM, LIGO, supermassive

small

Yukawa “fifth force” [2008.12456]

DM, LIGO, supermassivesmallLong-range forces between SUSY Q-balls[2108.08416]

DM (mass range: 10-16-10-6 M☉)

small

Supersymmetry flat directions, Q-balls[1612.02529, 1706.09003, 1907.10613]

DM (mass range: 10-16-10-6 M☉)

large

Light scalar field Q-balls (not SUSY)[1612.02529, 1706.09003, 1907.10613]

DM, LIGO, supermassivelarge

Oscillons [1801.03321]

DM, LIGO, supermassive

large

Multiverse bubbles[1512.01819, 1710.02865, 2001.09160]

DM, LIGO, supermassivesmall

PBH and neutron stars●●●●Neutron stars can capture PBH, which consume anddestroy them from the inside.
Capture probability high enough in DM richenvironments, e.g. Galactic Center
Missing pulsar problem…
[e.g. Dexter, O'Leary]

Fast-spinning millisecond pulsar.

What happens if NSs really are systematically destroyed byPBH?

Neutron star destruction by black holes⇒r-process nucleosynthesis, 511 keV, FRB[Fuller, AK, Takhistov, Phys.Rev.Lett. 119 (2017) 061101 ]Image: NASA/Dana BerryMSP spun up by an accreting PBH●●●r-process material●MSP with a BH inside, spinning near mass
shedding limit: elongated spheroid
Rigid rotator: viscosity suﬃcient even withoutmagnetic ﬁelds [Kouvaris, Tinyakov]; more so if
magnetic ﬁeld ﬂux tubes are considered
Accretion leads to a decrease in the radius,increase in the angular velocity (by angularmomentum conservation)
Equatorial regions gain speed in excess ofescape velocity: ejection of cold neutron matter[Fuller, AK, Takhistov, Phys. Rev. Lett. 119 (2017) 061101] also, Viewpoint by H.-T. JankaPrimordial black holes, neutron stars, and the origin of gold●●

●Light elements areformed in the Big Bang
Heavy elements, up toFe, are made in stars
What about Au, Pt, U…?
PBH can play a role

Shigehiro Nagataki
Gordon Baym
Ashley Mackenzie / Quantar-process nucleosynthesis: site unknown●●●●Image: Los Alamos, Nuclear Data Groups-process cannot produce
peaks of heavy elements
Observations well described byr-process
Neutron rich environment
neededSite? SNe? NS-NS collisions?..

r-process nucleosynthesis: site unknown●●Image: Los Alamos, Nuclear Data Group

SN? Problematic: neutrinos
NS mergers? Can account for all
r-process?

NS-NS might not be not enough...

[Kobayashi et al.,ApJ 900:179, 2020]

r-process material: observations
Milky Way (total): M~104 M☉
Ultra Faint Dwarfs (UFD): most of UFDs show no enhancement of r-process
abundance.
However, Reticulum II shows an enhancement by factor 102-103!
“Rare event” consistent with the UFD data:
one in ten shows r-process material[Ji, Frebel et al. Nature, 2016]

NS disruptions by PBHs
●Centrifugal ejection of cold
neutron-rich material (~0.1 M☉)
MW: M~104 M☉ ✔

●UFD: a rare event, only one in ten
UFDs could host it in 10 Gyr ✔

●Globular clusters: low/average DM
density, but high density ofmillisecond pulsars. Rates OK. ✔

[Fuller, AK, Takhistov, PRL 119 (2017) 061101]
also, a Viewpoint PRL article by Hans-Thomas JankaNS disruptions by PBHs●●●●

●Weak/diﬀerent GW signal
No signiﬁcant neutrino emission
Fast Radio BurstsKilonova event without a GW
counterpart, but with a possible
coincident FRB(Vera Rubin Observatory, ZTF,...)
511 keV line
[Fuller, AK, Takhistov, Phys. Rev. Lett. 119 (2017) 061101 ]511-keV line in Galactic Center
Origin of positrons unknown. Need to produce
1050 positrons per year. Positrons must be
produced with energies below 3 MeV toannihilate at rest. [Beacom,Yuksel ‘08]
Cold, neutron-rich material ejected in PBH-NS
events is heated by β-decay and ﬁssion toT~0.1 MeV→ generate 1050 e+/yr for the rates needed to
explain r-process nucleosynthesis.
Positrons are non-relativistic.

ESA/Bouchet et al.

Fuller, AK, Takhistov, Phys. Rev. Lett. 119 (2017) 061101

Fast Radio Bursts (FRB)
Origin unknown. One repeater, others: non-repeaters. 𝛕~ ms.
PBH - NS events: ﬁnal stages dynamical time scale 𝛕~ ms.
NS magnetic ﬁeld energy available for release: ~1041erg

Massive rearrangement of magnetic ﬁelds at the end of theNS life, on the time scale ~ms produces an FRB.
Consistent with observed FRB ﬂuence.
Fuller, AK, Takhistov, Phys.Rev.Lett. 119 (2017) 6, 061101; 1704.01129
Abramowicz, Bejger, Wielgus, Astrophys. J. 868, 17 (2018); 1704.05931
Kainulainen, Nurmi, Schiappacasse, Yanagida, arXiv:2108.08717

GW detectors can discover small PBH...
...if it detects mergers ofPBH + NS⇓
BH of 1-2 M☉[Takhistov et al., 1704.01129, 1707.05849;
2008.12780]

1-2 M☉black holes(not expected from evolution of stars)

Kovetz et al.

Conclusion
●●●
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Simple, generic formation scenarios in the early universe:PBH from scalar forces, PBH from a scalar ﬁeld fragmentation, PBH from vacuum bubbles...
PBH with masses 10-16 - 10-10 M☉ , motivated by 1-100 TeV scale supersymmetry,can make up 100% (or less) of dark matter. PBH is a generic dark matter candidate in SUSYPBH from ~ 1-100 GeV scale particles can naturally explain DM abundanceMicrolensing (HSC) can detect the tail of DM mass function.
PBH can contribute to r-process nucleosynthesis
Signatures of PBH:
○ Kilonova without a GW counterpart, or with a weak/unusual GW signature○ An unexpected population of 1-2 M☉ black holes (GW)
○ Galactic positrons, FRB, etc.
Yukawa forces ⇒ primordial structures ⇒ PBH, baryogenesis, other consequences!

ISCO-2023: a whale of a conference!
Local Organizing Committee:
Hiroyo Clemente (OIST)
Tetsuo Hatsuda (RIKEN)
Nicholas M. Luscombe (OIST)Youhei Morita (OIST)
Shigehiro Nagataki (RIKEN)
Tadayuki Takahashi (Kavli IPMU)

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