Trou noir primordial

Résumé

Un trou noir primordial est un type de trou noir hypothétique formé à l'époque de l'univers primordial dans les régions extrêmement denses. Dans les premiers instants de l'Univers selon la théorie du Big Bang, la pression et la température étaient si élevées que de simples fluctuations de densité de la matière suffisaient pour donner naissance à un trou noir. Alors que la plupart des régions de hautes densités ont été dispersées dans l'expansion qui a suivi, les trous noirs primordiaux sont restés stables, et seraient encore présents aujourd'hui. Leur existence a été proposée pour la première fois en 1966 par Iakov Zeldovitch et Igor Novikov. Cinq ans plus tard, Stephen Hawking publie le premier une théorie détaillée sur leur origine. Puisqu'ils n'ont pas été formés à partir d'étoiles, leur masse peut être significativement plus faible que celle d'une étoile. Hawking a calculé qu'elle pourrait être aussi faible que e−8kg (soit de l'ordre de la masse de Planck, 2,176 10-8 kg). Un des

Source officielle

https://fr.wikipedia.org/wiki/Trou_noir_primordial

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (9)

Publications associées

Chargement

Personnes associées

Chargement

Unités associées

Chargement

Concepts associés (27)

Concepts associés

Chargement

Cours associés (2)

Cours associés

Chargement

Séances de cours associées (4)

Afficher plus

Séances de cours associées

Chargement

Femtolensing by dark matter revisited

Sergey Sibiryakov, Wei Xue

Femtolensing of gamma ray bursts (GRBs) has been put forward as an exciting possibility to probe exotic astrophysical objects with masses below 10(-13) solar masses such as small primordial black holes or ultra-compact dark matter minihalos, made up for instance of QCD axions. In this paper we critically review this idea, properly taking into account the extended nature of the source as well as wave optics effects. We demonstrate that most GRBs are inappropriate for femtolensing searches due to their large sizes. This removes the previous femtolensing bounds on primordial black holes, implying that vast regions of parameter space for primordial black hole dark matter are not robustly constrained. Still, we entertain the possibility that a small fraction of GRBs, characterized by fast variability can have smaller sizes and be useful. However, a large number of such bursts would need to be observed to achieve meaningful constraints. We study the sensitivity of future observations as a function of the number of detected GRBs and of the size of the emission region.

IOP PUBLISHING LTD2018

Chargement

, ,

Using a set of cosmological hydro-dynamical simulations, we constrained the properties of primordial magnetic fields by studying their impact on the formation and evolution of dwarf galaxies. We performed a large set of simulations (8 dark matter only and 72 chemo-hydrodynamical) including primordial magnetic fields through the extra density fluctuations they induce at small length scales (k >= 10 h Mpc(-1)) in the matter power spectrum. Our sample of dwarfs includes nine systems selected out of the initial (3.4 Mpc h(-1))(3) parent box, resimulated from z=200 to z=0 using a zoom-in technique and including the physics of baryons. We explored a wide variety of primordial magnetic fields with strength B-lambda ranging from 0.05 to 0.50 nG and magnetic energy spectrum slopes n(B) from -2.9 to -2.1. Strong magnetic fields characterized by a high amplitude (B-lambda=0.50, 0.20 nG with n(B)=-2.9) or by a steep initial power spectrum slope (n(B)=-2.1, -2.4, with B-lambda=0.05 nG) induce perturbations on mass scales from 10(7) to 10(9) M-circle dot. In this context emerging galaxies see their star formation rates strongly boosted. They become more luminous and metal rich than their counterparts without primordial magnetic fields. Such strong fields are ruled out by their inability to reproduce the observed scaling relations of dwarf galaxies. They predict that dwarf galaxies are at the origin of an unrealistically early reionization of the Universe and that they also overproduce luminous satellites in the Local Group. Weaker magnetic fields impacting the primordial density field at corresponding masses less than or similar to 10(6) M-circle dot, produce a large number of mini dark matter halos orbiting the dwarfs, however out of reach for current lensing observations. This study allows us, for the first time, to constrain the properties of primordial magnetic fields based on realistic cosmological simulations of dwarf galaxies.

EDP SCIENCES S A2020

Chargement

Black hole metamorphosis and stabilization by memory burden

Sebastian Zell

Systems of enhanced memory capacity are subjected to a universal effect of memory burden, which suppresses their decay. In this paper, we study a prototype model to show that memory burden can be overcome by rewriting stored quantum information from one set of degrees of freedom to another one. However, due to a suppressed rate of rewriting, the evolution becomes extremely slow compared to the initial stage. Applied to black holes, this predicts a metamorphosis, including a drastic deviation from Hawking evaporation, at the latest after losing half of the mass. This raises a tantalizing question about the fate of a black hole. As two likely options, it can either become extremely long lived or decay via a new classical instability into gravitational lumps. The first option would open up a new window for small primordial black holes as viable dark matter candidates.

AMER PHYSICAL SOC2020

Chargement