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 [tag:black-holes] and [tag:wormholes] for certain kinds of singularities occuring in [tag:general-relativity]. For the procedure of "getting rid" of singularities, consider [tag:regularization].

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71 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 ...
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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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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
72 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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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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Black hole in timespace: point or “trench”? [duplicate]

I wonder what is the nature of a black hole as set of points of manifold. A single point (with infinite curvature) or a "trench" ? I thought that it is a "point", but since black holes can collide and ...
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2answers
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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
110 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
74 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
70 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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3answers
363 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
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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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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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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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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
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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
92 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
226 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
144 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
53 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
57 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
105 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
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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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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
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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
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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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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
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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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59 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
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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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1answer
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If all spacetime paths inside a black hole point towards the singularity, then does that mean entropy is decreasing?

Entropy is a concept of disorder. A drop of blue ink inside a glass of water only has 10^10 factorial possible ways of being an ink drop, but it has 10^11 factorial possible ways of being an ink soup. ...
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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
141 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
257 views

Finding the maximum value of electric field

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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31 views

What happens to renormalisation counter-terms in the classical limit?

My understanding is we add counter-terms to the actions in the process of renormalisation. Presumably these terms don't have a physical effect in a classical interpretation of the action. i.e. they ...
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149 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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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
96 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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32 views

What happens when a black hole evaporates?

I have read other articles here on the subject and I think my question is different.. When a singularity evaporates enough to reach just above the limit of mass required to make the singularity, what ...
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2answers
121 views

Electrostatic values where there are some charge

I've started asking myself: What is the value of the electric field at the surface of a shell with uniform distribution? In particular, is it infinite, as this point is over an (infinitesimal) ...
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1answer
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Does the center of a black hole have a physical body?

From science class, I'm led to belive that all matter breaks down once it's sucked into a black hole. I get that part, but doesn't all that matter still exist in the center of the black hole? yes it's ...
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What is inside a black hole? [duplicate]

I'm trying to understand what causes a black hole in terms of it's composition. We know a start can die and collapse into a neutron star, but if the neutro star is not dense enough to create a black ...
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1answer
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Black hole and its density

I'm an amateur to astrophysics but I'm slowly teaching myself things and I have these three doubts. How does more compression relate to a stronger gravitational pull. Like, when we say that a black ...
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1answer
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Black holes as universal “anchors”? [closed]

I'm not a Physicist, but was watching a program about black holes. As I understand it time and space "stop" at the singularity of a black hole, which made me think of a black hole as some kind of "...
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Is math truly infinite or is it just theory? [closed]

I imagine you can theoretically add +1 to any number But untill it happens it isnt so. That + no free will = math is limited and has a definite value. I imagine its tied in with conservation laws... ...
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Curvature scalars and singularities

Without resorting to the singularity theorems, can we say that there is a singularity at a particular $r=\textrm{constant}$ if the value of the Ricci and Kretschmann scalars get infinitely large at ...
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1answer
109 views

Metric diameter of a ring singularity

In the Kerr metric the ring singularity is located at the coordinate radius $r=0$, which corresponds to a ring with the cartesian radius $R=a$. So the center of the ring singularity in cartesian ...
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Can the electrostatic force be infinite in magnitude? [closed]

The magnitude of the electrostatic force between two charges $Q$ and $q$ separated by a distance $r$ is given by $$F=\frac{kqQ}{r^2}$$ but the minimum value of $r$ must be $10^{-15}\ \rm m$. Therefore,...
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AdS/CFT correspondence and gravitational singularities

While Einstein‘s equation breaks down at singularities, the question arises: which statements/answers can be provided by the corresponding conformal field theory (CFT) in this case?
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Curl and circulation of a vector field that is ill-defined at the origin: any interesting physical effects?

In the cylindrical polar $(\rho,\phi,z)$ coordinate, suppose the velocity field in a liquid is given by $$\vec{v}=\frac{K}{\rho}\hat{e}_{\phi}, \qquad K=\text{constant}.\tag{1}$$ It can be easily ...