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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Do merging BHs have two or just one singularity?

There are a lot of questions about BH mergers on this site, and based on those, there are two main possibilities: 1. Initially, the merged BHs, now a joint single BH, have two singularities, that ...
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How to reach a singularity? [duplicate]

In the instant a singularity tries to form, it simultaneously would try to create a infinite density/gravity/time well. This raises a doubt in my mind that the singularity ever does actually form, ...
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3answers
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Are black holes 0 dimensional? [duplicate]

If black holes are mass of the star concentrated on a single point then how can it be moving through a 3-dimensional space? How can they spin?
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Particles falling towards a singularity [duplicate]

This is a revision of my earlier question. Sorry. I'm a beginner here and on a learning curve regarding format. If the gravity well steepens to infinity at the point of a singularity, then so does ...
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1answer
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Particles reaching a singularity [closed]

If the gravity well steepens to infinity at the point of a singularity, then so does the "time well". Understandingly, the inward falling energy/matter is not aware of this change in time relative to ...
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1answer
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Infinite Electric Field Energy [duplicate]

If the total electric energy associated with a field is: and the electric field of a point charge follows an inverse square law: then $U_{ES}$ would be infnite if you compute the integral. Can ...
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2answers
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Geodesic Incompleteness and the Kretschmann Scalar

If my understanding is correct, singularities (whether time-like or space-like) are defined by geodesic incompleteness. Since it is easier, we use the Kretschmann scalar $R^{\alpha\beta\gamma\delta}...
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How do singularities combine when two black holes combine?

If we solved GR in the case of two black holes colliding, does each individual black hole have a single pointlike singularity at their respective centres, and would those singularity combine? Trying ...
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1answer
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Description of singularities

In Hawking's (and Ellis') book the section 8.3 says: The preceding theorems prove the occurrence of singularities in a large class of solutions but give little information as to their nature. To ...
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8answers
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The Enigma of Universal Gravitation Forces [closed]

This is taken from a book called "Physical Paradoxes and Sophisms" by V. N. Lange. 1.22. The Enigma of Universal Gravitation Forces The law of gravitation can be written $F=\gamma\frac{m_1m_2}{R^...
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Why we can use the divergence theorem for electric/gravitational fields if they have singular point?

If we were to calculate the surface flux of the total field, we would only require the vector field to be continuous on the boundary. But in order to replace the surface integral by a volume integral ...
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Physical meaning of infinite energy density?

I was reading about the Rayleigh-Jeans law and the UV catastrophe. One of the limitations of the theory proposed was that it predicted the total energy density to be infinite. In books it's just ...
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1answer
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Is it possible for matter to occupy a singularity, which is the point of rupture of space time caused by a black hole?

Also, are singularities caused by blackholes reversible? May one do work to reverse the singularity or black hole? Do blackholes create permanent holes in space time, thereby shrinking space time, or ...
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Van Hove singularity (calculating the logarithm)

I am trying for hours to understand this calculation, I hope someone can help me with it. In the paper of Van Hove himself (https://journals.aps.org/pr/abstract/10.1103/PhysRev.89.1189) he derived the ...
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How to calculate the total cross section of a QCD process? (qq->gg)

I want to calculate the total cross section of various QCD processes (let's go with $q\bar{q}\rightarrow gg$ for this question) at tree level for some colliding hadrons at a certain energy (let's go ...
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Black Hole Mass Density Ratio [duplicate]

(1) The density of water increases as one approaches the bottom of the sea. (2) The density of neutron stars also increases from crust to core. Black holes with greater mass have a larger radius and ...
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Was the singularity at the big bang a black hole? [duplicate]

Was the singularity at the big bang a black hole? If not, how does the singularity compare to a black hole?
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Curing spacetime singularities by a higher-curvature gravitational Lagrangian

It is well known that the self-energy of a point charge is diverging in the classical (Maxwell) electrodynamics. In 1930's, Born and Infeld introduced their nonlinear electrodynamics (with a ...
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What are the topological properties of a Schwarzschild black hole, and of its horizon and singularity?

What is the topology of a black hole spacetime? What about its horizon and its singularity?
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239 views

What's the proper distance from the event horizon to the singularity?

How far away is the event horizon of a (Schwarzschild) black hole away from the central singularity for a radially infalling observer starting with $v=0$ somewhere outside the black hole? After ...
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3answers
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0% of speed of clock outside infinite well

Juan Maldacena says here: "For a very massive and very compact object the deformation (or warping) of spacetime can have a big effect. For example, on the surface of a neutron star a clock runs slower,...
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2answers
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Zero gravity condition

If I made a hole in the center of the moon I would experience zero gravity because all of the mass would surround me. Since a black hole is so named do we consider that the center also has zero ...
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1answer
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Anatomy of a black hole: which are its layers?

I'm trying to find out how a Kerr-type black hole is structured (that is, a black hole with non-zero angular momentum but no net electrical charge). According to the information I have found, the ...
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Question about electric field singularities

I was reading the first chapter of Purcell-Morin (3rd Edition) and came across an explanation of what a singularity is. It said that a singularity of the field isn't necessarily a point where E$\...
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Does an event horizon imply a singularity

I surprisingly did not find anyone addressing this directly. The weak cosmic censorship states, very loosely that singularities imply event horizons. I am wondering whether the converse is true. I.e. ...
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QED infrared divergences

How do infrared divergences arise in QED? What is an example case of such a divergence and how do we usually deal with such divergences? Are they absorbed like ultraviolet divergences?
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If the running coupling constant $\alpha(\mu)$ of QED becomes of order one at high $\mu$, why not changing $\mu$?

In the (modified) MS renormalization scheme, after dimensional regularization, we introduce some parameter $\mu$ with power of mass to keep the dimensionality of integrals under control. The ...
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What is the radius of the ringlike singularity of a Kerr BH?

For a rotating (Kerr) Black Hole the radius of the ring singularity is evaluated mathematically as R = a, see Metric diameter of a ring singularity. This means that R is always greater (or equal) to ...
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Where is the singularity located in a Kerr black hole?

In a rotating Kerr black hole is the ringlike singularity situated between the inner and the outer event horizon of the black hole?
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Divergence of Feynman diagram

Can we say whether the given Feynman diagram is divergent or not by just looking into the Feynman diagram? How to remove these divergences?
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Feynman rules and the hydrogen atom

In his Quantum theory of fields, Vol. 1, Weinberg claims that the old-fashioned perturbation theory allows studying an appearance of singularities in matrix elements by intermediate states. As an ...
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1answer
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What do I see looking forward inside the black hole? [closed]

I have read this question: Future light cones inside black hole What happens to light that falls into a black hole? What would be the view like from inside a black hole looking towards the event ...
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Dirac Delta Function and Schwarzschild Singularity [duplicate]

Pardon my naive question. I recently found out about Dirac Delta function. It is interesting to note that Schwarzschild singularity gives the infinity values of the General relativity field equations ...
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42 views

Kretschmann scalar is discontinuous

I am studying this paper: "Non-singular rotating black hole with a time delay in the center" by T. de Lorenzo et al. In this paper authors calculate a new metric for a regular, rotating black hole. ...
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1answer
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How to interprete this singularity? [closed]

I am calculating the Kretschmann scalar for the Schwartzchild metric. This is the graphic I get: Where $R$ is the radial coordinate and $x=\cos(\theta)$. So, there is the singularity at $R=0$ as it ...
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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
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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
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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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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
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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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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
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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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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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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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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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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
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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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Query concerning black holes [duplicate]

What information can be conveyed from a black hole about the substances and radiations it absorbs into it's singularity.
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30 views

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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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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