# Questions tagged [singularities]

Use this tag for questions about singularities in physical quantities, i.e. cases where a quantity becomes or appears to become infinite or ill-defined. Consider the more specific tags [black-holes] and [wormholes] for certain kinds of singularities occurring in general relativity. For the procedure of "getting rid" of singularities, consider the [regularization] tag.

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### Black Hole Singularity Other Universe

It is thought that there is another universe beyond the singularities of black holes. Is it because width of the light cones become zero at the singularity, meaning that you can cross infinite ...
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### Thinking about singularities and the speed of light

I apologize that this takes so much explanation. From what I understand about the idea of the "singularity" in a black hole, it's not taken literally as Infinite mass in zero density or ...
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### Singularity in coordinate transformations

Ok. I would like to apologise if the question is somewhat 'stupid'. So, initially I didn't pay much attention to it, but we know that when the Jacobian vanishes for a particular point, we say that the ...
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### Why does the electromagnetic repulsion between protons in the nuclei fail to prevent the formation of a black hole singularity?

The process of forming a black hole requires all matter to be crushed into a point by gravitational attraction. But the electromagnetic repulsion between protons inside the nuclei of the atoms is way ...
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### How can a singularity move?

When an object approaches the event horizon of a black hole from the point of view of a remote observer time of this object freezes. (Does it also stop? Since it has a finite speed even at the event ...
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### Electrostatic potential resolving singularity

I'm trying to determine the electrostatic potential caused by a specified charge density function: $$\rho_c(\vec{r}) =\begin{cases} 1 & \vec{r} \in V\\ 0 & \text{otherwise} \end{cases}$$ The ...
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### Big Bang and the Pauli Exclusion Principle

Due to some of the basic principles of quantum mechanics, we have the Wolfgang Pauli exclusion principle, where two fermionic bodies cannot occupy the same quantum state simultaneously. If that is ...
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### Can Hawking Radiation occur at the Big Bang singularity or at the Big Crunch singularity?

While reading about Hawking Radiation which occurs due to the quantum effect (quantum fluctuations) at the event horizon of the black hole,I was thinking whether this radiation can take place at the ...
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### Is there any reason that the Schwarzschild radius of a 5(+)-dimensional object would require different math?

$$R_g = \frac{2GM}{c^2}$$ It doesn't seem to me that the gravitational constant or speed of light particularly care how many dimensions there are in this context. Mass is mass whether it comes in ...
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### If the universe started from a singularity expanding based on pressure, how did physics decide which direction each thing would expand toward?

Two entities truly captured within a singularity would have no positional offset from each-other, nor volume to differ either. Yet for two things to push away from each-other, they must have either ...
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### Can there be singular subtensors in the elasticity tensor and what would it mean in that case?

Can the elastic tensor $C_{ijkl}$ describing the stress strain relationship as $$\sigma_{ij} = C_{ijkl} \, \varepsilon_{kl}$$ contain singular subtensors? In that case, what would it mean mechanically?...
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### Time and causality at the beginning of the universe

I have been, quite a few times, been caught up in arguments on the internet, where my opponent posits causal events existed before the "singularity" at the "beginning" of the ...
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### Doubt regarding the existence of conjugate points on timelike geodesics

The expansion of a timelike geodesic congruence with (normalized) tangent vector field $\xi^a$ is defined as $\theta=\nabla_a\xi^a$. Assuming the strong energy condition, $R_{ab}\xi^a\xi^b\geq 0$, and ...
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### Topologically, is a curvature singularity just a hole?

Topologically speaking, a hole can be introduced into a manifold and it will still be a manifold, e.g. remove points within a 2-sphere of some radius from the cartesian plane and you'll still have a ...
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### Does the physical singularity of the Reissner-Nordstrom metric have a ring structure?

The physical singularity of the Kerr metric has a ring structure due to the axi-symmetric nature of the metric. The Reissner-Nordstrom metric is the solution for a non-spinning, electrically charged ...
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### Singularity at the centre of Black hole [duplicate]

Why we assume that there is a singularity at the centre of Black hole? Isn't it possible that there is a different state of matter exist at such a high pressure which we haven't able to explain using ...
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### Aren't Black Holes Just Neutron/Quark Stars?

Disclaimer: My understanding of general relativity is rudimentary at best, so bare with me and correct me where necessary. Also, any math in the explanation is appreciated, but try to also keep the ...
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### What is the dynamic geometry of merging rotating black hole singularities?

In rotating black holes, either Kerr (uncharged) or Kerr-Newman (charged) the singularity is believed to be a one dimensional ring or torus, unlike the single point singularity of a non-rotating black ...
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### Is the mass of a black hole somewhere at all?

The Schwarzschild vacuum solution describes the gravitational field and thus the spacetime curvature of a black hole. The mass of a black hole is sometimes associated with its singularity as pointed ...
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### If black holes are just empty vacuum of space inside, then what causes the curvature?

I have read this question: The fundamental confusion many have about black holes is thinking that they are discrete "things" surrounded by horizons and other phenomena. But they are ...
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### What if black hole is perturbed and it is far from being spherical/symmetric? Can it still sustain a singularity?

Black holes are generally the considered as the most symmetric astrophysical bodies in the Universe. If an intermediate mass black hole consumes a nearby red giant and in the process, for a very short ...
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### Violation of weak vs strong cosmic censorship examples

I am trying to better understand the weak vs strong cosmic censorship through simple examples. On the Wikipedia page, it says: "The two conjectures are mathematically independent, as there exist ...
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### What is the mathematical description of a point torque (or point couple) singularity?

Suppose that a concentrated (point) force is exerted at the origin of a 3D dimensional space along the direction $\boldsymbol{e}$. Mathematically, this could be prescribed in terms of a delta Dirac ...
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### Quantum Mechanic: Sperically symmetric finite well [duplicate]

Consider the following 3D potential: $$V(r)=\begin{cases}-V_0 \ \ \ \ \ \ & r \leq a\\ 0 &r > a\end{cases}$$ we want to find the eigenfunctions for $\ell=0$, in particular we are interested ...
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### How can the jerk tend towards infinity?

Consider a block of mass $m$ kept on a rough surface. A time varying force $F =t$ is applied on the block in a direction parallel to the surface. Assuming the coefficient of static and kinetic ...
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### Singularities of the Coordinate Systems

We know that, the singularity of the Schwarzschild metric at $r=2M$ can be removable via coordinate transformation to Kruskal-Szekers . Can we apply a similar argument to the Kerr metric? If so, what'...
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### What is the problem with a rotating singularity?

In most cases, people ask how can a point spin, resulting in a 'ringularity' as an answer. But I'm not quite sure why a point can't spin. After all, it's like saying how can something with mass have ...