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.

Filter by
Sorted by
Tagged with
1
vote
1answer
48 views

Can a gauge transformation eliminate singularity of gauge potential?

Suppose I have a gauge potential $A$ which goes to infinity at some point $x_0$. Can I use a gauge transformation \begin{equation} A'=U^{-1}AU+U^{-1}dU,~~~U=\exp\{-i\alpha^a(x)T^a\} \end{equation} to ...
1
vote
0answers
27 views

Is there physical reason for a stably causal spacetime, or the existence of a Cauchy surface?

In their 1979 essay Global structure of spacetimes, Geroch and Horowitz describe methods of determining the topology, causal structure and singularity of spacetimes. Their (mathematical) arguments are ...
0
votes
0answers
28 views

Are the Infinities in QFT Perturbation (closed loop diagrams) a Consequence of Point Interactions?

I have heard (and read) that the infinities that arise in QFT interactions using higher-order perturbations are "a problem that comes down to the fact that the interactions occur at a single ...
-2
votes
1answer
78 views

Is infinity measurable? [closed]

Is infinity really measurable, and can anything be measured without counting (at least to "one")? My teacher asked me whether infinity's measurable, and believes that our farthest point of ...
0
votes
0answers
20 views

Singularity in a BH - pointlike? [duplicate]

This answer https://hsm.stackexchange.com/a/12505/13669 has the curious sentence The singularity of a black hole is not a point at its center, it's a spacelike singularity. What is that supposed to ...
13
votes
2answers
2k views

Is there a limit to how much spacetime can be curved?

My question is about the fact that general relativity predicts bending of space and time. However, I have not seen anything regarding the limits to how much space or time can be bent. So my question ...
0
votes
1answer
74 views

How to apply Feynman rules of counterterms to calculate amplitudes?

Consider $\phi^4$-theory with counter-terms and renormalized mass, field and coupling constant, described by the Lagrangian $$\mathcal{L}= \underbrace{\frac{1}{2} \partial_{\mu} \phi_{r} \partial^{\mu}...
9
votes
1answer
859 views

Do black holes exist in 1+1 dimensional spacetime?

I'm currently working in 1+1 dimensional spacetime and would like to know if black holes can exist in such a manifold? I think they can because the Schwarzchild metric has the coordinate singularity, ...
-1
votes
1answer
75 views

Centre of a black hole

In a text intended for people without background in general relativity or quantum mechanics, I read two statements which are false or do not make sense, if I'm correct. Am I correct, and why (not)? ...
1
vote
1answer
49 views

How did the Holm 15A Galaxy BH reach 40 Billion Solar Masses?

The most massive supermassive black hole discovered to date lies within the Abell 85 galaxy cluster. At the heart of this cluster is the galaxy Holm 15A, containing an estimated 2 trillion solar masse ...
-1
votes
1answer
178 views

Race to the singularity, who wins, the photon or the neutrino?

There are a lot of questions and answers about speed falling into a black hole, none of them answer my question. Most of them only talk about speeds outside the event horizon. The only relevant answer'...
1
vote
1answer
48 views

Does string theory remove the singularity of black holes? [duplicate]

One of the reasons we want a theory of Quantum gravity is to understand black holes and string theory is the most popular approach, but so far I haven't seen any attempt of the theory to remove the ...
1
vote
1answer
97 views

Is there any example from physics, supporting $\int_0^1\frac1xdx=\int_1^\infty\frac1xdx$?

This question is related to the potential possibilities of classification of divergent integrals more precisely than just "divergent to infinity" and the like. Improper divergent integrals ...
0
votes
0answers
51 views

How is rotational information transferred to a singularity? [duplicate]

If some mass spirals into a black hole the conservation of angular momentum means that the result will have to spin (at least to my albeit limited understanding). But if the singularity is a point, ...
2
votes
0answers
109 views

Do Singularities really exist? [duplicate]

This question has been on my mind for quite some time. I don't really have in-depth knowledge about singularities, but from what I understand they rupture the spacetime and they are hard/impossible to ...
3
votes
0answers
49 views

Regular black hole with an evanescent horizon

I'm reading a great paper named Geodesically Complete Black Holes by R. Carballo, F. Filippo, S. Liberati and M. Visser about regular black holes and I'm trying to understand a particular situation. ...
1
vote
2answers
93 views

Why are constant electric fields considered when their energy is infinite?

Sometimes in some problems (that i am facing in high school physics related to electrostatics) like the problems of finding flux crossing through a cube where magnitude of electric field is some ...
2
votes
2answers
56 views

How is the Coulomb potential infinity resolved in quantum field theory?

People always says that the infinity of the coulomb potential $V(r)=\frac{k}{r}$ as $r$ approach to zero is resolved in quantum field theory. I would like to know how this is done.
2
votes
1answer
99 views

How can an observer reach the singularity if black hole interiors grow forever?

This article https://www.quantamagazine.org/why-black-hole-interiors-grow-forever-20181206/ describes how black hole interiors grow forever although the exterior volume of the black hole does not ...
0
votes
0answers
54 views

Correct a misunderstanding about the black hole paradox

I think I have misunderstood the black hole information paradox. Here's my view, first of all a black hole is not an actual singularity, the singularity comes from the space-time metric when $r=0$, ...
1
vote
1answer
69 views

Why can't we use the line element to distinguish coordinate from gravitational singularities?

I am a bit confused as to why we can't use the line element to identify coordinate from gravitational singularities. My question stems from learning about the Schwarzschild Metric and the singularity ...
2
votes
1answer
52 views

Black hole atlases

What sort of atlases of spaces that contain a black hole (that is, including the space inside the event horizon), if any, are there? Does the central singularity have to be excluded? Are there atlases ...
1
vote
1answer
56 views

Definition of density of black holes

For a blackhole of mass $M$, radius $R$ and Schwarzschild radius $R^*$ (where $R<R^*$), its density $\rho$ is defined as $$\rho=\frac{M}{(R^*)^3}.$$ One reason I read for using the Schwarzschild ...
1
vote
0answers
29 views

Euclidean Schwarzschild black hole

I am studying the Euclidean Schwarzschild metric and trying to find its isometries. It still has $\partial_{\phi}$ as a Killing vector, but I wonder if the range of $\phi$ is still $0$ to $2\pi$. The ...
5
votes
4answers
349 views

Schwarzschild solution, stress-energy side of Einstein's equation

The Schwarzschild solution in GR only has a singularity at the origin $r=0$: otherwise there is no matter content. The right-hand side of Einstein's equation is hence almost everywhere zero, but I ...
1
vote
1answer
78 views

Is Loop quantum cosmology replacing the Big Bang singularity with a big bounce?

Am I correct in understanding that in the cosmological version of Loop quantum gravity, namely Loop quantum cosmology, the universe in all models starts with a big bounce? Are there other models, for ...
1
vote
1answer
51 views

Are there 3D singularities in general relativity?

In the commonly considered spacetimes with singularities, the singularities - to my knowledge - always have less than 3 spatial dimensions: The singularity of the Schwarzschild spacetime (describing ...
1
vote
1answer
70 views

What is the physical interpretation of self-contraction being divergent?

If we take vacuum expectation value of two scalar field at the same point (2-point correlation function when 2 points coincide) it diverges. what is the physical reason(interpretation)behind this? ...
0
votes
2answers
42 views

Is there a maximum replusion between two electrons?

Coulomb's law says that as the distance between two electrons approaches zero, the force becomes infinite. However this is just an approximation, and electrons are better described as fuzzy clouds of ...
1
vote
1answer
37 views

Is Penrose's CCC consistent with Penrose's singularity theorem?

According to Penrose's Comformal Cyclic Cosmology (CCC), there were universes prior to ours, prior to the singularity of our universe. But how is this claim compatible with his famous singularity ...
38
votes
11answers
7k views

What does it mean when people say “Physics break down”?

So I keep hearing people talking about how physics break down at for example the center of a black hole. And maybe I am just to stupid but, why? How can we say that? For all we know a black hole could ...
8
votes
1answer
381 views

Is the event horizon of an extremal black-hole just a coordinate singularity?

For generic black holes one demonstrates that the event horizon is just a coordinate singularity by changing coordinates to a system where the metric is well defined. For example we have Kruskal-type ...
0
votes
0answers
65 views

How Many Universes in Hawking's theory?

In Stephen-Hawking's theory, the explosion of a singularity (How would that be achieved?) would set time into reverse, returning to time, $t = 0$ (the origin of the Universe). How did this singularity ...
0
votes
2answers
179 views

Black holes: where is its mass? In a singularity or on the horizon?

The entropy of a Schwarzschild black hole is located near the horizon, and the moment of inertia of a Schwarzschild black hole is $MR^2$. Both aspects imply that the mass of a Schwarzschild black hole ...
0
votes
0answers
38 views

Green function for Laplace's equation in complex three dimensional space

The Green function for Laplace's equation in three dimensions for a source at the origin is $$ \nabla^2 G(\mathbf{r})= \delta(\mathbf{r}) =\delta(x)\delta(y)\delta(z) $$ where is $\mathbf{r}=\mathbf{...
2
votes
1answer
109 views

Singularities in path integrals

So, I once watched a video (I think it was by Andrew Dotson) that I can't find any more about techniques used to deal with singularities in path integrals. The presenter mentioned how the integral ...
0
votes
0answers
19 views

DOS for anisotropic 2D electron gas dispersion

If we start with the simple 2D isotropic-parabolic dispersion, \begin{align} E\left(\textbf{p}\right) & \approx\tilde{\varepsilon}_{0}+\alpha p_{y}^{2}+\alpha p_{x}^{2}, \label{1} \end{align} ...
4
votes
1answer
134 views

Could spacetimes have singular manifolds?

Let's take a spacetime as a pair $(M,g)$ where $M$ is the manifold and $g$ the metric. I've seen that there exist a generalization of manifolds. This generalization consist in accept singularities in ...
2
votes
2answers
59 views

For a radially symmetric wavefunction is $\Psi$ allowed to blow up at $r=0$ provided that $|\Psi|^2r^2$ doesn't?

For a spherically symmetric wavefunction the probability is proportional to $|\Psi|^2r^2$, and if the wave function blows up at $r=0$ then at $r=0$ $|\Psi|^2=\infty$, and $r^2=0$ meaning that the ...
6
votes
1answer
61 views

Is ergosphere without singularity possible?

The ergosphere is created because of the twisting of spacetime by a fast-rotating black hole. Then what if we rotate a non-singular object (I mean just a normal object that is not a black hole) really ...
3
votes
1answer
434 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 ...
17
votes
5answers
2k views

Work done in assembling a point charge is infinite [closed]

Griffiths says The energy of a point charge is infinite $$W=\frac{\epsilon_{0}}{2\left(4 \pi \epsilon_{0}\right)^{2}} \int_0^\infty\left(\frac{q^{2}}{r^{4}}\right)\left(r^{2} \sin \theta\; \mathrm{d}...
3
votes
1answer
141 views

Expansion in flat spacetime

I have been studying Raychaudhuri equation and focusing theorem related to it. Focusing theorem says that if the strong energy condition is satisfied and rotation tensor vanishes $\omega_{ab}$=0 then ...
2
votes
2answers
68 views

How do you actually use fields?

Note: I'm probably using the wrong letters/notation here. I apologize. I use $\omega$ to represent an object, and $\mathcal{U}$ is the universe. I'm not sure how else to do it. $m(\omega)$ and $x(\...
1
vote
1answer
68 views

Removable singularity of metric?

The metric of 2D plane is \begin{equation} ds^2=dr^2+r^2d\phi^2, \end{equation} which is singular at $r=0$ (is it because vanishing Jacobian?). It is said this singularity is removable if $0<\phi&...
-2
votes
1answer
54 views

Is it possible that a black hole has a universe in itself? [duplicate]

Every black hole has a singularity. But the singularity is covered by a thing called 'Event horizon'or ' Schwarzchild Radius'. Our universe is originated from a naked singularity. By naked singularity,...
2
votes
1answer
65 views

Does electric charge $e$ become complex at some scale $\mu$?

\begin{equation} \mu \frac{\partial{e}}{\partial \mu }=\frac{{e}^3}{12\pi^2}=\beta({e})\end{equation} This is the equation for beta function in quantum electrodynamics, it tells us about how coupling ...
0
votes
0answers
79 views

What kind of causality would be broken if black hole singularities would be real?

In his article "The Universe as a Whole" 1, physicist Dennis Sciama said We therefore face a crisis in theoretical physics. Either classical general relativity breaks down, or effectively ...
2
votes
1answer
82 views

Infinite Coulomb force when charges contact

The Coulomb force between charged particles is inversely proportional to the square of the distance. Yet, why don't we observe the infinite force when the distance approaches zero? Say we can bring ...
0
votes
1answer
40 views

Distinction between different points at Big Bang Singularity

As per the Big Bang model of Cosmology roughly 13.8 billion years ago a singularity exploded exponentially to eventually become the present universe. At the present time (basically current time-slice) ...

1
2 3 4 5
15