Primordial black hole constraints with Hawking radiation—A review

We consider the possibility of primordial black hole, PBH, formation sourced by a rise in the power spectrum. The power spectrum becomes large at late times due to decay of the inflaton into vectors through a ϕFF̃ coupling. Two background inflaton models which are well supported by current Planck data are considered, natural inflation and hilltop inflation. Many of the papers considering formation of PBHs have considered a peaked power spectrum where Pζ gets small again at late times. This avoids overproducing miniature PBHs which would evaporate and could violate BBN and CMB bounds. This paper examines the other way of avoiding these bounds, producing PBHs from perturbations formed closer to the end of inflation such that the PBHs are too small to violate these bounds. This has the advantage of allowing for simpler models in that no additional feature is needed to be added to evade constraints. Although these black holes would have evaporated, they can be close to without exceeding current BBN bounds, making it possible the signature will be revealed in the future. We calculate how the various model parameters affect the mass and number of PBHs produced. Any evidence for PBHs sourced from an inflationary power spectrum would provide evidence for inflation on a drastically different energy scale from the CMB, and thus would be highly valuable in answering what occurred during inflation.

Section: Jcap07(2023)031mentioning

confidence: 99%

Primordial black hole production in natural and hilltop inflation

Cook

2023

“…Notably, at the intersection of these two major, open problems potentially lie light black holes of non-stellar origin, or Primordial Black Holes (PBHs, see e.g. [3][4][5] for recent reviews of formation mechanism, constraints, and search strategies). The observation of the final stages of black hole evaporation would provide clues on the number of dark sector degrees of freedom independent of them being secluded from the visible sector [6][7][8], and would shed light on physics at energy scales close to the Planck scale (and whether the Planck scale itself corresponds to its standard value, unlike in several beyond-the-Standard-Model extensions), thus offering insights on quantum gravity (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Searching for Exploding black holes

Boluna,

Profumo,

Blé

et al. 2024

The observation of the final stages of the evaporation of a light black hole, which Hawking referred to as “black hole explosion”, would offer critical insights on quantum gravity and high-energy physics phenomena. Here, we explore, review, and revisit the observational features and rates expected for nearby, light, evaporating black holes, and we assess and compare the expected sensitivity of a broad range of observatories. We then focus on the search for candidate black hole explosions in archival data from the Fermi Large Area Telescope and Gamma-ray Burst Monitor, and outline possible future observational campaigns.

“…The persistent absence of any definitive, non-gravitational signal from dark matter (DM) candidates [1], including those in the class of weakly interacting massive particles [2], has led to a renewed interest in black holes of non-stellar origin, also known as primordial black holes (PBHs) [3][4][5]. While at sufficiently large masses gravitational (micro-)lensing strongly constrains the fraction of the cosmological DM that can consist of PBHs [3], finite-size source effects make it virtually impossible to probe masses significantly below around 10 20 grams [6].…”

Section: Introductionmentioning

confidence: 99%

“…While at sufficiently large masses gravitational (micro-)lensing strongly constrains the fraction of the cosmological DM that can consist of PBHs [3], finite-size source effects make it virtually impossible to probe masses significantly below around 10 20 grams [6]. Nonetheless, around that mass black holes are slated to emit abundant and bright nonthermal radiation via Hawking evaporation, offering an alternative way of constraining their global contribution to the cosmological DM [4].…”

Section: Introductionmentioning

confidence: 99%

Updated constraints on primordial black hole evaporation

Korwar

Profumo

2023

The Hawking evaporation process, leading to the production of detectable particle species, constrains the abundance of light black holes, presumably of primordial origin. Here, we reconsider and correct constraints from soft gamma-ray observations, including of the gamma-ray line, at 511 keV, produced by electron-positron pair-annihilation, where positrons originate from black hole evaporation. First, we point out that the INTEGRAL detection of the Large Magellanic Cloud provides one of the strongest bounds attainable with present observations; and that future MeV gamma-ray telescopes, such as GECCO, will greatly enhance such constraints. Second, we discuss issues with previous limits from the isotropic flux at 511 keV and we provide updated, robust constraints from recent measurements of the diffuse Galactic soft gamma-ray emission and from the isotropic soft gamma-ray background.