# Where Does the Physics of Extreme Gravitational Collapse Reside?

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## Abstract

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## 1. Introduction

## 2. Black Holes and Spacetime Singularities: The Standard GR Picture

#### 2.1. Event Horizons

#### 2.2. Singularities

## 3. Black Holes and Spacetime Singularities: Ultraviolet Effects beyond GR

#### 3.1. Trapping Horizons

#### 3.2. Preventing Singularities

## 4. Ultraviolet Effects: Phenomenological Considerations

#### 4.1. Horizon Predominance

#### 4.2. Preponderance of the Singularity Regularization

## 5. Effective Bounces, Black-Hole to White-Hole Transitions and Shock Waves

#### 5.1. Collapse from Infinity and Homogenous Thin-Layer Transition

#### 5.2. Non-Perturbative Ultraviolet Effects

#### 5.3. Collapse from a Finite Radius and Triangular-Shaped Transition

#### 5.4. Short-Lived Trapping Horizons

#### 5.5. Short Transients and the Propagation of Non-Perturbative Ultraviolet Effects

## 6. Physical and Observational Consequences

#### 6.1. Towards New Figures of Equilibrium

#### 6.2. Energetics of the Transient Phase

#### 6.3. Ripples from the Transient Phase

#### 6.4. Recent Detection of Gravitational Waves from Coalescing Black Holes

## 7. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 1.**Transition from the black-hole patch to the white-hole patch by using a smooth interpolation with characteristic time scale ${t}_{\mathrm{R}}$. The qualitative behavior of light cones for different values of the radial coordinate is shown.

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**MDPI and ACS Style**

Barceló, C.; Carballo-Rubio, R.; Garay, L.J.
Where Does the Physics of Extreme Gravitational Collapse Reside? *Universe* **2016**, *2*, 7.
https://doi.org/10.3390/universe2020007

**AMA Style**

Barceló C, Carballo-Rubio R, Garay LJ.
Where Does the Physics of Extreme Gravitational Collapse Reside? *Universe*. 2016; 2(2):7.
https://doi.org/10.3390/universe2020007

**Chicago/Turabian Style**

Barceló, Carlos, Raúl Carballo-Rubio, and Luis J. Garay.
2016. "Where Does the Physics of Extreme Gravitational Collapse Reside?" *Universe* 2, no. 2: 7.
https://doi.org/10.3390/universe2020007