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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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moving singularities

I am aware that black holes can move through space-time. Is there a way to move a naked gravitational singularity artificially? Sorry if this is a little stupid, trying to figure out the feasibility ...
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2answers
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Was the singularity just a mini model of our current unvierse? [duplicate]

Did the singularity just "containe" the matter, the energy and the space-time or it created them. If it just contianed them and then the expansion hppened, can we say it was just a mini model of our ...
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Could the Big Bang be a compressed manifold and not a singularity? [on hold]

What I'm imagining is a sort of fold in spacetime rather than a singular point right at the very beginning. I don't know if the CMB data reflects this or not, I was just wondering what people on here ...
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2answers
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Where is the Physical Singularity under the Holographic Principle?

From this article, it states that The holographic principle states that the entropy of ordinary mass (not just black holes) is also proportional to surface area and not volume; that volume itself ...
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3answers
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Why exactly are singularities avoided or “deleted” in physics?

What is the real reason that make us reject singularities everytime we see them in a theory/model? For example, in GR, it is predicted that black holes singularities have infinite density. This makes ...
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2answers
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Naked singularities and mass distribution of a black hole

Do naked singularities also appear mathematically if the mass of a black hole is uniformly spread around its Schwarzschild surface? I recently heard about the concept of a naked singularity and it ...
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2answers
59 views

Is the zero distance limit of Coulomb's law something to worry about?

Coulomb's law fails when the distance $r$ between to point charges vanishes. As $r\to 0$, the electric field between two point changes increases without limit. I should be bothered about the limit $r\...
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Would a cellular-automata universe allow singularities to exist?

It is usually assumed (almost always) that cosmological singularities (like black hole singularities) are impossible and do not exist in the universe. If the universe was like a cellular automata (...
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3answers
544 views

BH singularity? Infinite density

How can the density of a region of space go from finite density to infinite when there are no numbers larger than any Aleph0 number but smaller than any Aleph1 number (no decimal point in front of it, ...
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3answers
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How to find electric field at a point on an arbitrary surface charge $(\sigma)$ due to it?

Electric field at any point due to any volume charge $(\rho)$ Electric field at a point outside a volume charge is given by Coulomb's law: $$\vec{E}=k \iiint_V \dfrac{\rho}{r^2} (\hat{r})dV \tag1$$ ...
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Causal structure of spacetime. A pathological example of spacetime?

Consider a spacetime $(M,g)$ and $p \in M$. It is known that locally, the boundary of the chronological future of p is just the set of points along (future-directed) null geodesics starting at p. ...
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1answer
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Is the Big Bang a naked spacelike singularity?

While reading some answers on similar topics, I was wondering about the nature of the Big Bang singularity in the standard cosmological model. I know it's a spacelike singularity that have a ...
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1answer
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Silly question about Schwarzschild Black holes and scientific communication

Well, in scientific communication literature often we encounter the following phrase about black holes: A Black Hole is a body that have infinite curvature and infinite density So, with basic GR ...
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2answers
194 views

Naked singularity

Many consider naked singularities as a fundamental problem and that it should be always covered by a horizon (Cosmic censorship hypothesis). But why naked singularities are really a problem? If we ...
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1answer
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Can the gravitational field be considered conservative despite the existence of singularities?

Assuming singularities are physical objects as opposed to mathematical artifiacts, can the gravitational field still be considered conservative? And if not, does this open a possibility of breaking ...
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1answer
76 views

Functions unbounded at a point on the domain: How to show electric field exists for any continuous volume charge density?

My understanding after reading Mike Stone's answer: \begin{align} \vec{E} &= k \iiint_{V} \dfrac{\rho(x',y',z')[x-x'\hat{(i)}+y-y'\hat{(j)}+z-z'\hat{(k)}]}{[(x-x')^{2}+(y-y')^{2}+(z-z')^{2}]^{...
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3answers
104 views

Does time exist at the center of a Black Hole?

A black hole is a wormhole resulting from a dead Star which is capable of sucking any mass/matter along its path due to Gravity. I was wondering what time would be like at the central point of the ...
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1answer
46 views

Magnetic field at points on the circuit

I know magnetic field lines due to a circuit always form closed loops. Therefore $\nabla \cdot \vec{B}=0$ everywhere (even at points on the circuit). However due to singularity, magnetic fields are ...
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2answers
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Weyl anomaly in 2d CFT (string theory lectures by D.Tong)

In his lectures on String Theory (http://www.damtp.cam.ac.uk/user/tong/string.html), Tong gives a proof of the Weyl anomaly, using equation $(4.36)$. It seems wrong to me. Here he uses the OPE ...
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1answer
34 views

Electric field at source points of any continuous charge distribution

In classical electromagnetism, is there a way to find the electric field at source points of a line, surface or volume charge? If there is a way, please explain in detail My idea: I don't really ...
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2answers
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Doesn't the fact that elementary particles are not black holes prove they are not point structures?

De Schwarzschild radius of a mass $m$ is defined as $$r_s=\frac{2mG}{c^2}(\frac m {kg}).$$ So if we insert in this formula the mass of an electron (a point particle, according to mainstream ...
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Are singularities' behaviour really unpredictable?

If a real/true singularity existed our models and theories would become useless to predict what would happen in that singularity. For example if naked singularities really existed, we could not ...
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1answer
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Can we “stir” space-time?

Depending on the energy-momentum density of a given region in space there is an intrinsic curvature to it. I can't help but feel like space-time is a like fluid, which begs the question whether it is ...
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1answer
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Would a 5-dimensional black hole actually break laws of physics?

I discovered a paper by, Figueras, Kunesch, and Tunyasuvunakool, "End Point of Black Ring Instabilities and the Weak Cosmic Censorship Conjecture." A Cambridge University press release is here. The ...
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1answer
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Equation for the field of a magnetic dipole

In my electrodynamics class, my professor derived the equation for the field of the magnetic dipole $$\vec{B}(\vec{r})=\frac{\mu_0}{4\pi}\frac{1}{r^3}[3(\vec{m}\cdot\hat{r})\hat{r}-\vec{m}]+\frac{2\...
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1answer
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Timehole - Black hole physics [closed]

If someone could shed some light so that I can think straight again that would be appreciated.. Anywho, since watching a video on what the universe may look like in trillions of years (each atom ...
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2answers
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How to plot the graph of this expression which involves Dirac delta function?

I was doing a problem on electrostatics which required finding the charge density from the given electric field and then plot a graph of the charge density. I was able to find the charge density which ...
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Easy way to extract UV divergence of an Feynman integral (1-loop, Dim-Reg)

For scalar integral (I mean Feynman integral with no numerator), using dimensional regularization, one could expand the integrand (treating the integration variable infinitely large) and calculate the ...
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1answer
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Where is mass density information of a Black Hole?

Have read that all the information of a black hole is contained on the Event Horizon. Does that include mass density of interior as a function of position? The shape of an event horizon depends on the ...
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0answers
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Normal ordering in 2D thermal CFT

I am trying to understand the notion of normal ordering in thermal CFT in 2D CFT, for instance I consider a two-point function of scalar primary operator with $\Delta$ dimension at finite temperature $...
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0answers
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Black hole interior [closed]

Had a few questions about the "interior" of the black hole. I've read that all the mass of a black hole is concentrated at it's center and that you can't isolate an object to an area of space ...
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1answer
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In string theory, what replaces the black hole singularity?

In string theory, what replaces the black hole singularity? I know that it is possible for a single string to have arbitrarily large energy. Is a black hole just a single string?
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1answer
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Uncertainty cannot be calculated?

I'm doing an experiment on resonance. The phase difference between the driving force and the one oscillating is given by $$\varphi=\arcsin\left(\frac{y_1}{y_2}\right)$$ where $y_1$ and $y_2$ are ...
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1answer
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Does infinite mass exist? [closed]

So when I search up if infinite mass exists, google provides me with a source that states infinite relativistic mass does exist at the speed of light which is why it is impossible to ever reach to ...
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3answers
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Electron falling into proton approaches infinite kinetic energy why?

Foreword I believe this question to be different from the usual "Why don't electrons fall into the nucleus" because this A: asks about the details of explanations for why electrons don't fall into ...
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1answer
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Can a curvature singularity (i.e. BH), as defined in terms of geodesic incompleteness, actually exist in nature?

A curvature invariant is a scalar representation of curvature derived from a curvature tensor. The classic example is the Kretschmann scalar derived from the Riemann curvature, where $K=R_{μνλρ}R^{...
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4answers
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How can infinite density exist?

Thinking in mind, infinite density is where there is no space between particles correct me here if i'm wrong. Inside a blackhole at the core. So if there are 2 particles touching each other Then ...
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1answer
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Are the actual singularities with geodesic incompleteness the same as curvature singularities?

Types of singularities include curvature singularities and conical singularities. So, for a curvature singularity(black hole) with geodesic incompleteness, is it the same as a physical singularity? If ...
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1answer
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General Theory of Relativity [duplicate]

Why is General Theory of Relativity not applicable in the singularity of Black Hole?
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3answers
152 views

Kruskal-Szekeres Coordinates and the Singularity

On the wikipedia page for Kruskal-Szekeres coordinates, it states: [Kruskal-Szekeres] coordinates have the advantage that they cover the entire spacetime manifold of the maximally extended ...
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1answer
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Why is electric field inside a charge distribution not infinite?

Let's consider electric field due to a charge distribution at a point $P$ inside the charge distribution. Due to inverse square nature of electric field, electric field due to an element volume charge ...
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1answer
55 views

Has quantum mechanics been able to define the centre of a black hole? [closed]

It is said that quantum mechanics has defined everything we observed everything so far, but did it predict the existence of the Higgs Boson beforehand and has it been able to define the Singularity?
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Minkowski Space is not truly conformally compact

We say a manifold $(M,g)$ is conformally compact if it is the interior of some $(\overline M, \overline g)$, such that $$g = r^{-2}\overline g|_M,\quad \mathcal Z(r) = \partial M,\quad \text{and}\quad ...
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4answers
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Intuitively, why do attempts to delay hitting a black hole singularity cause you to reach it faster?

In general relativity, proper time is maximized along geodesics. Inside of a black hole, all future-oriented timelike trajectories end at the singularity. Putting these two facts together, we find ...
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Would you reach a singularity before evaporation of the black hole? [duplicate]

When going to a physics camp the other day, we discussed the Schwarzchild-metric for a rotational symmetric non-spinning black hole and its famous time-dilation properties. However, we know that ...
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1answer
105 views

Are physicists still ignorant of the existence of real singularities?

(1) Is the gravitational singularity (or space-time singularity) the same as the black hole singularity? (2) The wikipedia page says Physicists are undecided whether the prediction of ...
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2answers
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What is the energy required to create a gravitational field equivalent to that a mass $m$ shows?

If the mass of a neutron star in its collapse becomes a singularity, then the resting energy of this gravitational field must be $E = mc^2$ ($m$ = star mass). Is this possibility wrong?
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Mass and Expanding Space

1) space is expanding at an increasing rate, therefore things are getting farther from each other and therefore increasing in velocity. 2) the faster an object moves relative to another, the more ...
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2answers
108 views

Actuality of black hole singularity

With the completion of finite theory of physics, even if the theoretical black hole singularity is completely eliminated, how can we be sure that it does not exist in nature? Physics theory is ...
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22 views

Folded strings or hidden preons as black hole interior: signals with gravitational waves?

Suppose the black hole interior (non-kerr, kerr-like,...) is made of some kind of subsubatomic stuff (e.g., folded strings or superstrings, folded branes, buches of preonic pregeometry or whatever). ...