https://sites.google.com/view/cosmoscode/

An open-source code for numerical relativity specialized for PBH formation

It is originally translated from SACRA code [Tetsuro Yamamoto, Masaru Shibata, Keisuke Taniguchi(arXiv:0806.4007)] into C++.

Users are supposed to understand the source code to some extent and use it by modifying it themselves. 

Extensive support regarding usage cannot be expected.

Description

• COSMOS for 3+1 dim simulations 

  • https://github.com/cmyoo/cosmos 

  • Perfect fluid with linear equation of states & massless scalar field

  • Non-Cartesian scale-up coordinates

  • Fixed mesh refinement

  • OpenMP parallelization 

• COSMOS-S for 1+1 spherical simulations

  • https://github.com/cmyoo/cosmos-s 

  • Derived from COSMOS with CARTOON method (all items listed above are inherited)

https://sites.google.com/rikkyo.ac.jp/pbhworkshop/home/

Summary of the 7th meeting

[Recent works by postdocs and students]

Kokubu-san:

- The criterion of PBH formation in the matter dominated era and the effect of angular momentum.

- Using dynamical Einstein cluster.

Saito-san (Daiki):

- Average values of PBH spin with softer equation of state, p=w\rho.

- The spin becomes large for smaller w.

Inui-san:

- Accounting for the DM of M~10^(-15)Msun by PBHs with the exponential tail of the curvature perturbation.

- Detectable with scalar induced gravitational wave.

Escrivà-san

- PBH formation duaring QCD phase transition.

- Reduction of w in the EOS leads to smaller threshold values.

Uehera-san

- Numerical simulation of type II PBH formation.

- The schematic picture shown by the Penrose diagram has been consistently confirmed.

Yamamoto-san

- PBH WD merger rate enhancement depending on PBH mass

- Non-Gaussianity measurement from SGWB from BBH mergers

Hirano-san

- The extended Galilean genesis.

- The condition fNL>>1 is achieved implying that the theory is excluded.

Koga

- PBH binary distribution and statistically very small value of the effective inspiral spin.

- Other important effects which should be incorporated?

[Discussion]

- Any impact of recent progress of understanding quantum grav. effects in BH physics on PBH physics?

- Recent discussions on black hole information paradox apply when the graviton is massive (more precisely, some people claim that is the case). Could you use this as a new motivation to study massive gravity?

- Any interesting macroscopic dark matter candidates other than BHs? Soliton star models? Fuzzballs? Wormholes? KK Graviton cluster?

- How can we close the window of the PBH-DM observational constraint?

第6回ミーティングメモ

[参加学生]

（QG）

・上原くん：数値計算・数値相対論

・斎藤くん：PBH spin (softer EOS)

（立教）

・いいづかくん：BH tidal LOVE number

・かつまたくん：Kerrまわりの粒子の軌道

（C研）

・あべくん：ultra compact mini halo

[議論]

（斎藤くん質問から）

・PBH以外でprimordial fluctuationから形成されるobject, soliton star, boson starについて、なにか制限はあるか。

・haloがwimpsなら過剰なradiation。

・localに大きいisocurvature perturbationは可能　->　より小さいスケールでclustering？ -> ultra compact halo形成へ。

・haloからの重力波。stochasticにanisotropicな重力波が観測される？

（かつまたくん質問から）

・PBHとastro BHの違い？formation process -> typical massに違い。

・scalar-tensor theory -> “gravitational memory effect” = BHまわりの重力定数が、BHの形成時の値を保持する。

・refs: Barrow & Carr 1996 (https://journals.aps.org/prd/abstract/10.1103/PhysRevD.54.3920)

・non-dynamicalなscalar理論ならmemory effectをもつ？ -> Cuscuton theory

・Cosmological BH solution to Cuscuton: https://arxiv.org/abs/1312.3682

（あべくんから）

・PBH massのconstraintにwindow。

・GRB parallax (視差)による観測（同時・異なる地点の観測で異なる増光が期待される）

・ただしsourceが有限サイズをもつ際のsuppressionがあるので注意。

・parallaxによる増光が観測される「確率」が重要となるかもしれない。

・ref: Gamma-ray burst lensing parallax: Closing the primordial black hole dark matter mass window, Sunghoon Jung and TaeHun Kim, https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.013113

（佐々木さんから）

・PBH mass distributionについて、以下は問題あり？：Non-linear statistics of primordial black holes from gaussian curvature perturbations, Cristiano Germani, Ravi K. Sheth, https://arxiv.org/abs/1912.07072

・Single-scaled power spectrumなのにbroad mass distributionの結果。 -> Press-Schechter approachを、compaction functionの本来PBHに寄与しない極大に適用してしまっているためか。（柳さんの論文にコメントあり）

（原田さんから）

・BHが蒸発し切らない可能性について

・有限サイズのBH remnantが残り、Planck massよりずっと大きい可能性。ガンマ線もほぼ出ない。

・ただしsemi-classical描像は壊れるだろう。

・参考：蒸発しない場合のconstraint（須山さんら）: https://arxiv.org/abs/2005.05693

・dynamicalなBH時空上で量子場の計算はできないか（lower multipoles）。Hawking放射によるback reactionも取り入れて。

1: Short talks (10 mins. talks)

Sasaki-san, “One small step for an inflaton, One Giant Leap for Inflation”

A tiny step in the inflaton potential can completely change inflationary predictions.

https://arxiv.org/abs/2112.13836

Kusenko-san, “Exploring new connections of PBH formation with leptogenesis, dark matter, gravitational waves”

(Work in progress)

Koga-san, “Effective spin distribution of PBH binaries with critical phenomena”

(In preparation)

2: Next meeting may be in person? @ Nagoya U., Rikkyo U., or IPMU?

Takafumi Kokubu, “PBH formation from dynamical Einstein cluster?”

Suggestion of a new scenario of PBH formation in matter-dominated era.

Dynamical Einstein cluster may serve as a collapse model of density perturbations that have both inhomogeneity and “rotation” in a sense.

Marcos Flores, “Primordial Black Holes from Long-Range Scalar Forces and Scalar Radiative Cooling”

A new scenario of PBH formation in radiation-dominated era.

The long range forces mediated by scalar fields can form halos of heavy particles. This halos collapse into BHs by radiative cooling. An explicit model to explain this scenario is given.

https://arxiv.org/abs/2008.12456

Chul-Moon Yoo, “Simulation of PBH formation from iso-curvature perturbations”

Full numerical simulation of PBH formation by spherical massless scalar field in radiation-dominated era. It turns out that PBHs can form by iso-curvature perturbations of massless scalar field.

・Self-introduction

Shin'ichi Hirano, Kohri-san, Flores-san, Yokoyama-san, Tada-san

・Talk and Discussion

Yoo-san: “Toward a numerical simulation of PBH formation with a multi-component field in spherical symmetry”

The numerical simulation can run thanks to CARTOON method, and a massless scalar can collapse to BH for a specific initial condition at least. 

Sasaki-san: “Isocurvature perturbations in PBH cosmology”

PBH formation from an iso-curvature perturbation based on linear cosmological perturbations. The induced GWs by PBH evaporation would be strongly constrained.

Kusenko-san: “Exploring novel scenarios for PBH formation and their observational consequences.”

Possible PBH formation mechanisms: Yukawa interaction (dark fermion beyond SM), baryon asymmetry (asymmetric dark matter model), attractive force by scalar field in SUSY, multiverse.

PBH spin is a new window.

Koga-san “Review: Who Ordered That? Unequal-mass binary black hole mergers have larger effective spins”

arXiv: 2106.00521

From observational data, we would read offTalk the correlation between the mass ratio and \chi_eff in binary BH mergers.

1. Topics of research: related to PBH, but not restricted too much.

2a. Meeting: once in 2 months. About 1 hour.

2b. Slack:

-Please post informations to each channel.

-#0publications: please post your recent publications regardless of the subjects.

-#0journal_club: please share interesting papers.

2c. Students:

-Hiroki Asami

-Daiki Saito

-Kusenko-san’s student

3. Current status

 Chul-moon: Axion cloud decay, 2 components matter collapse (iso-curvature), PBH spin estimation with mesh refinement, PBH from collisionless particles.

 Hiroki: Catastrophic instability of AdS spacetime with collisionless particles.

 Daiki: False vacuum decay phenomena due to radiation from rotational BH.

 Sachiko: GW from early Universe, waveform of BH-BH merger, GW from PBH collapse.

 Albert: Numerical simulation of PBH, non-linear threshold, Q-ball, non-spherical effects.

 Yasutaka: photon sphere and spacetime instability, PS in dynamical cases, seeking PBH subjects.

 Tomohiro: Classification of singularity, l=0,1 perturbation, PBH formation in matter dominated Universe.

 Alexander: PBH formation from heavy fermion, probing PBHs by n-body simulation.

 Misao: Iso-curvature scenario, PBH in matter dominated phase in the early Universe.

 Shin’ichi: (absent)

4. Others

-Meeting notification by e-mail (Slack automation)? google calendar?

-Organizations by postdocs.