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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4
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1answer
126 views

Events inside a Blackhole [duplicate]

I am trying to understand the concept of event horizon and what really the word "event" means and have some questions. I apologize if the questions seem stupid or vague as I am not a physics student ...
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3answers
163 views

What is meant by "Big Bang" in expressions like "$10^{-36}$ seconds after the Big Bang"?

Sometimes I find expressions like "The inflationary epoch lasted from $10^{−36}$ seconds after the conjectured Big Bang singularity [...]". What is meant by "the Big Bang" in this context? I ...
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2answers
103 views

Related to the information contained in $a = v \frac {dv}{ds}$

While studying kinematics I came to the definition of acceleration which is $a = \frac {dv}{dt}$. But from this equation we can derive that $ a = v \frac {dv}{ds} $ which when I evaluate at $v=0ms^{-1}...
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1answer
48 views

What mechanisms would allow a naked singularity to glow? [closed]

I was reading about why there should be a limit on how fast a blackhole can spin but assuming a naked singularity is real and is exposed, my question is how does it glows? Blackbody? or hawking ...
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1answer
145 views

How do self-loop diagrams end up contributing nothing to observables?

The probability amplitude for single particle to enter our system with momentum $k$ and leaving with momentum $q$ can be calculated as \begin{align} A(k\to q ) = \langle q| T e^{i \int_{-\infty}^\...
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1answer
53 views

If a choice is made, will it create a singularity? [closed]

When I watched videos of a TV show named "Star vs the forces of evil" on Youtube, there was a video about the main character - Star - being forced to solve a Math problem, because all versions of Star ...
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1answer
129 views

Would a "naked singularity" and a spinning black hole behave the same?

So I've been doing a lot of research on spinning black holes and fumbled upon the concept of a "naked singularity" where a gravitational singularity exists without an event horizon. Ignoring the ...
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1answer
194 views

Roger Penrose's conformal cyclic cosmology (CCC)

Does the Weyl curvature tensor $C$ of the black hole singularity in the conformal cyclic cosmology diverge to infinity unlike the Big Bang (C = 0)?
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1answer
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How is it possible to compress matter infinitely like in a black hole?

How can a star that turns into a black hole technically be smaller than a quark? $10^{12}$ atoms $\geq$ 1 quark. That shouldn't work.
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1answer
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How do physicists deal with fields at the location of charges?

In the Feynman Lectures Vol 1, Chapter 28 (at the end of section "28–1 Electromagnetism"), it is mentioned: For those purists who know more (the professors who happen to be reading this), we should ...
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1answer
105 views

Why isn't it a problem that the first term in the perturbative scattering series yields infinity (or one)?

In QFT we usually want to calculate objects of the form $\langle f|\hat S|i\rangle$ which yields the probability amplitude for the process $i \to f$. We can expand the scattering operator $\hat S$ in ...
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1answer
165 views

Regulating a divergent integral in QED

When we try to regulate a divergent integral, we introduce another parameter, say $\lambda$ and then compute the integral. We finally take a limit (either $\lambda \rightarrow 0, \infty $) to restore ...
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0answers
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Point particle and angular deficit

I would like to understand in what sense an angular deficit can be interpreted as a point particle. Typically, if you have a metric in polar coordinates such as: $$ds^2 = -dt^2 + a^2(t,r) dr^2 + r^2 d\...
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0answers
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Infinity problem in basic classical mechanics problem [closed]

My question arises from a classical mechanics problem from a Hong Kong physics training programme: This is not a homework question as I am not asking about how to solve the problems in the image. As ...
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1answer
64 views

Did the big bang start at ONE infinitely curved point (or a 4D curved ball shrunk to a point) with an infinite density of energy?

I'm confused. In this question it is said: The simple answer is that no, the Big Bang did not happen at a point. Instead, it happened everywhere in the universe at the same time. How could it have ...
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1answer
113 views

Black hole mass

It has been taught to us that since the black holes have finite mass, their gravitational force is also finite, which totally fits. The Black hole anyhow has a singularity at it's center which is ...
4
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0answers
140 views

Why can't we accept that there's no black hole? [duplicate]

According to a distant observer, any mass never falls into the event horizon, they just appear to be moving slower towards it. So, why can't we tell people this : there are black holes, but it's just ...
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0answers
35 views

Singularities of conformal coefficient

It is known that the conformal transformation saves the causal structure of the spacetime. Then, what is the physical interpretation of the singularities of the conformal coefficient? I know that ...
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1answer
92 views

Why spacetime fabric don't tears due to mass of heavy black hole?

In GR, All objects create curvatures in the space-time fabric. Why space-time fabric doesn't tear due to the mass of a heavy black hole? What is it made of?
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2answers
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What are the pros and cons of Einstein-Cartan Theory?

As an alternative to General Relativity, i hear that it can avoid the initial big bang singularity as well as the singularities in black holes, so why does it appear to be talked about so little? If ...
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2answers
55 views

Regarding the $E$-field at the location of discrete point

Most textbooks define the $E$-field at the location of $q_{1}$$\\$ as: $$\textbf{E}=-\frac{q_{2}}{r_{21}^2}\hat{\textbf{r}}$$ which is finite. However, the field is also defined as the force per ...
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1answer
428 views

On scheme dependence in QFT renormalization

I searched for the answer to my question quite a while and it seems nobody ever asked similar questions or it is written explicitly in any textbooks. The question is, If physical parameters of any ...
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4answers
125 views

Electric field of point charge

in above picture, we have two point charge ( same size ). Does electric field of q2 at location of q1 depend on size of q1? because we know when we want to measure electric field of a charge, use ...
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2answers
324 views

What does a zero determinant of the metric tensor in a space means?

Does it show that a coordinate transformation occurrs, and how?
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2answers
445 views

How do we know we cannot escape the event horizon?

A doubt assails me: deepening the Schwarzschild and Kerr space-times I found a beautiful article of the University of Rome, which provides a method to identify an event horizon based on the analysis ...
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1answer
64 views

Discontinuities in electric fields

I'm a mathematician self-studying physics for fun and I'm trying to wrap my head around a simple concept, which is a consequence of approximations. Basically, by Coulomb's law, if I have a point ...
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0answers
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Adding up gravitational fields of infinitely many objects?

I'm reading a book introducing gravity and find something I don't understand. Please check the attached image. The sentence in red bracket claims that if one adding up gravitational fields of ...
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5answers
3k views

How can electric field be defined as force per charge, if the charge makes its own, singular electric field?

The electric field $\bf{E}$ represents how much force would act on a particle at a certain position per unit charge. However, if we actually place a particle in that position, the electric field will ...
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1answer
363 views

Difference between Coulomb law and QED

According to Coulomb law, the electromagnetic force between point charges separated at zero distance is infinite. Does QED explains the same result, or there is any difference?
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1answer
62 views

Possible Beginnings of New Universes? [duplicate]

Black holes pull anything and everything that enters past the event horizon into the singularity. What if the current unknown output where all of this infinitely condensed matter goes to is the ...
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2answers
97 views

What is the reason behind black hole making objects near him dissappear? [closed]

If a black hole is formed by the death of a star, why does it suck things with its gravity going inside it? Does it not have a surface or anything? Is it just a hole in the space which keeps on ...
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1answer
344 views

Showing $I=\int d^3k\int dk^0\frac{1}{k^4}$ to be logarithmically divergent

Consider a momentum integral of the form $$I=\int d^3k\int dk^0\frac{1}{k^4}$$ where $k^2=(k^0)^2-(\vec{k})^2$ and the integral over $k^0$ runs from $-\infty$ to $+\infty$. This integral is common in ...
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4answers
166 views

Is there a limit to the amount of mass we can concentrate in a region of space?

Black holes are solutions to Einstein's Field Equations. Black holes contain a singularity hidden from the outer universe. As I understand, these singularities are infinitesimal and contain a very ...
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1answer
88 views

What are quasi-regular singularities?

The book EXACT SPACE-TIMESIN EINSTEIN’SGENERAL RELATIVITY by Podolsky and Griffiths has a section on Taub-Nut space-time metrics and there is defines the singularity made in the Taub metric as quasi-...
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1answer
215 views

Does the second-order correction to degenerate perturbation theory vanish?

Consider a degenerate two-state system with states denoted by $|1\rangle$ and $|2\rangle$. If we apply a perturbation $H^\prime$, the first order correction to the energy is obtained by choosing two ...
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2answers
135 views

How to prove the absence of naked singularities?

Suppose we have a static, spherically symmetric solutions of Einstein equations coupled to a certain matter source, and we are able to show that the scalars obtained by the stress energy tensor on ...
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4answers
4k views

Why does the Schrödinger equation work so well for the hydrogen atom despite the relativistic boundary at the nucleus?

I have been taught that the boundary conditions are just as important as the differential equation itself when solving real, physical problems. When the Schrödinger equation is applied to the ...
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0answers
58 views

How shall we show the surface integral approaches a limit (or does not blow up) at a field point near $S'$

Consider the electric field due to volume charge distribution in volume $V'$: $\mathbf{E}=\displaystyle \int_{V'} \rho' \dfrac{\mathbf{r}-\mathbf{r'}}{|\mathbf{r}-\mathbf{r'}|^3} dV'$ The integrand ...
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1answer
119 views

How can two zero-dimensional black hole singularities have different masses? [duplicate]

(This question is not a duplicate because it is primarily concerned with how different zero dimensional objects/singularities with zero volume, are able to contain differing information on black holes ...
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2answers
268 views

Does a black hole singularity compress mass back into energy? [duplicate]

I was watching this PBS spacetime video which made the case that mass is just a form of bound energy. Essentially massless particles are confined in a small space giving particles the illusion of mass....
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2answers
556 views

Three types of singularities in black holes?

Now, please don't dismiss this question because of its entertaining context. Today I attended a lecture by Kip Thorne and at some point he mentioned, almost offhand, that a few years ago it was found ...
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1answer
133 views

What is wavelength at classical turning points using WKB Approximation? [closed]

According to what I know is that a classical turning point in Newtonian Mechanics is a point where a particle has a zero kinetic energy (Total energy is equal to potential energy) and must be ...
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0answers
69 views

Should stellar black holes contain a singularity? (in GR) [duplicate]

Consider a star, for simplicity a non rotating one. The corresponding spacetime will be similar to a Schwartzschild one (if the star is static and spherically symmetric). Outside the star we will ...
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2answers
154 views

Can a black hole event horizon form before the singularity for an outside observer?

This is not a duplicate, my question is not about whether BHs have or don't have a singularity, but my question is whether, because of time dilation, no matter has reached the center and formed a ...
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0answers
53 views

Due to TIME stopping, are contemporary Black Holes really just Large SHELLS of Matter and not Singularities? [duplicate]

If TIME slows down as you approach a Black Hole, has there been sufficient time in our Universe (13.8 Billion Years since the Big Bang occurred) for ANY matter inside the Event Horizon of ANY Black ...
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4answers
217 views

When GR is not valid passing the event horizon?

A test body crosses the event horizon of a black hole. When can we say that GR breaks down? Only at the singularity? At any point CLOSE enough to the singularity? How much close? In summary, do we ...
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1answer
2k views

Finding the maximum value of electric field for a given two-dimensional charge distribution

Suppose you have a surface of finite area with a fixed surface charge distribution. Does a maximum electric field magnitude $|\vec{E}|_{max}$ exist for each and every possible surface area? If yes, ...
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2answers
522 views

Is it possible to have mass with zero volume?

As we had always studied that matter occupied space and has mass and our universe is made of matter so do that mean that there is no case where mass is present without volume .
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0answers
53 views

Point-like particle vs naked singularity? [duplicate]

In general, physics seems to consider elementary particles such as electrons to be point-like. On the other hand, naked singularities seem to cause all sorts of trouble, including closed time-like ...
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1answer
151 views

What happens when you dump antimatter onto a naked singularity?

Inspired by this question, what would happen if you dumped antimatter onto a naked singularity? The answers for the previous question suggest that once the antimatter crossed the event horizon, no ...

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