# Aspects of Quantum Gravity Phenomenology and Astrophysics

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## Abstract

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## 1. Introduction

## 2. Graviton

#### 2.1. The Linearized Theory of the Graviton

#### 2.2. Gravitons in Loop Quantum Gravity

#### 2.3. Gravitons in Semiclassical Gravity

- (i)
- As the coherent states are non-Abelian in nature, the expectation values of operators have semiclassical corrections which originate due to self-interactions. These can be detected for high-frequency gravitational waves.
- (ii)
- The search for individual “gravitons” or quanta of geometry would require much more precise instruments, able to resolve the coarse-graining of geometry itself.

#### 2.4. Summary

## 3. Search for Hawking Radiation and Primordial Black Holes

#### 3.1. Formation of Primordial Black Holes (PBH)

#### 3.2. Jean’s Instability

#### 3.3. A Quantum Entropy Production Fluid and Jean’s Instability

#### 3.4. PBH Formation

#### 3.5. Evaporation of PBH

#### 3.6. Archived Data

#### 3.7. Gamma-Ray Bursts

#### 3.8. HESS

#### 3.9. Neutrino Experiments

## 4. Event Horizon

## 5. Conclusions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) Building block for the decomposition of the 3-geometry. (

**b**) Example of one of the smearing surfaces to calculate the momenta.

**Figure 2.**The upper estimates of the number of final bursts at the 99% confidence limit from some experiments [48].

**Figure 3.**Plot of the semiclassically corrected photon geodesic impact parameter relation. The plot shows a bounce as the distance from the critical radius approaches the semiclassical length scale of $\tilde{t}\sim {10}^{-8}$ units.

**Figure 4.**Plot of the semiclassically corrected photon geodesic impact parameter relation. The plot shows a bounce as the distance from the critical radius approaches the semiclassical length scale of $\tilde{t}\sim {10}^{-66}$ units.

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**MDPI and ACS Style**

Dasgupta, A.; Fajardo-Montenegro, J.
Aspects of Quantum Gravity Phenomenology and Astrophysics. *Universe* **2023**, *9*, 128.
https://doi.org/10.3390/universe9030128

**AMA Style**

Dasgupta A, Fajardo-Montenegro J.
Aspects of Quantum Gravity Phenomenology and Astrophysics. *Universe*. 2023; 9(3):128.
https://doi.org/10.3390/universe9030128

**Chicago/Turabian Style**

Dasgupta, Arundhati, and José Fajardo-Montenegro.
2023. "Aspects of Quantum Gravity Phenomenology and Astrophysics" *Universe* 9, no. 3: 128.
https://doi.org/10.3390/universe9030128