# 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.

672 questions
Filter by
Sorted by
Tagged with
284 views

### Better derivation for the gravitational potential energy

I was shown this derivation for the gravitational potential energy, and I'm not very happy about it assuming that $\frac{1}{\infty} = 0$. Is there a better derivation, either using a completely ...
2k views

43 views

### Physical Size of a Naked Singularity [closed]

I have watched a few videos about naked singularities, and it is my understanding that one is a singularity without an event horizon. My question, is could you ever have that with anything larger ...
32 views

### What is the physical shape of a rapidly spinning singularity?

Let's say I have a star 20x the mass of the sun. At the end of its life, it collapses into a black hole. Now correct me if I am wrong, but as it collapses it rotational speed dramatically increases ...
97 views

### Black Hole Formation

If you plot a space-time diagram of an object falling through the event horizon of a black hole, and draw the past and future "light cones" of the object at every point, wouldn't the point ...
59 views

### What happens when an expression for a physical quantity becomes undefined?

Now I am taking a quite a specific example here. Let's consider a circular race track banked at an angle of $\theta$. The coefficient of friction between the track and the tire is $\mu$. What's the ...
53 views

### What is a naked singularity?

What is a naked singularity? Would a naked singularity be one that that the event horizon is so small that it is the same size as the singularity? what could make one that small?
70 views

### Seeking intuitive explanations regarding $A_{n-1}$ singularities

I am studying Ben Craps' lecture notes Big Bang Models In String Theory for my undergraduate thesis. I am not well versed in topology, and would like intuitive explanations for certain ideas regarding ...
58 views

### Non-Vacuum Solutions for Black Hole Interiors

Everything I read about black holes—discussions using Penrose diagrams and Kruskal coordinates, etc.—seems to be based on vacuum solutions to EFE. Sometimes it’s said that all trajectories entering a ...
39 views

### Derivation of the Schwarzschild solution [duplicate]

For the Derivation of the Schwarzschild solution my Professor use: $R_{\mu\nu} = 0$ since we are in vacuum. I see that we are in vacuum, but we assume a mass at point $r = 0$. Thus, the curvature is ...
32 views

### What causes a singularity as opposed to something of a quantitatively extreme value?

Something that approaches infinity or is "essentially infinity" (an oxymoron) or is "near-zero" is the very opposite of the quality of infinity, and yet explanations tend to use ...
55 views

### Schwarzschild Naked Singularity Creation

In the Schwarzschild metrics (Plank units): $$ds^2=-\left(1-\frac{2m}{r}\right)dt^2+\left(1-\frac{2m}{r}\right)^{-1}dr^2+r^2\left(d\theta^2+\sin^{2}\theta d\phi^{2}\right),$$ we can have a Black Hole (...
90 views

### Gravitational attraction as distance approaches zero

Imagine a $x$-$y$ plane, which induces an acceleration field obeyed by the equation $a= -\frac{C}{z^2} \vec{k}$ where $z$ is the perpendicular distance from the plane to the ball and $C$ is just ...
26 views

### Does tidal force continue to increase as a man falls into a black hole?

Small black holes have collosal tidal forces at their event horizons. But there are black holes large enough where a man can cross the event horizon without being ripped apart. But does the tidal ...
26 views

### Is black hole supposed to oscillate in/out of singularity as matter falls on it?

So, as soon as star radius becomes smaller that Schwarzschild radius it becomes a black hole. But as matter continues to fall on it attracted by the gravitational pull its radius sooner or later will ...
82 views

40 views

### Basic confusion about fields and infinite potential

Consider a system of two electrically charged particles. Their charge doesn’t matter for my question but suppose they are both positive. I am confused about what the correct way to calculate forces on ...
35 views

26 views

### What are timelike singularities? [duplicate]

What are timelike singularities? I'm trying to learn about the properties of timelike singularities.
94 views

### Is there any observational evidence for the existence of Schwarzschild black holes?

So AFAIK the objects that have been confirmed to be black holes by direct observation of the event horizon("black hole shadow"), like M87 for instance, also show observable evidence of frame dragging (...
84 views

### Confusions on QED renormalization

In many QFT textbooks, we usually see the calculations of vertex function, vacuum polarization and electron self-energy. For example, one calculates the vacuum polarization to correct photon ...
75 views

### Physical interpretation of propagator pole

In QFT the propagator is divergent for the on-shell momentum of the particles. When e.g. calculating the amplitude for a box loop, the propagator diverges for on-shell particles running in the box-...
64 views

### What happens to Coulomb's law at small distances? [closed]

I searched in the forum and found the maximum distance is $r=1.75\times 10^{-15} m$. Ok, imagine an electron hits a plate with charge of 1 proton, the result of Coulomb's law is $230$ Newtons. ...
38 views

### Question about Renormalization of Ghosts in QCD in MS scheme

During a calculation of the Renormalization constant of the ghosts in QCD I stumbled over the following question: When I calculate the self-energy of the Faddeev-Popov ghosts in $SU(N)$ non-abelian ...
One can show that for the phase difference $\Delta$ between the two wave functions (slit 1 and slit 2) it holds the first equality on the LHS \Delta=\oint_{\partial\Omega} \vec{A}\overset{!}{=}\...