Questions tagged [cosmic-string]
Questions about properties, dynamics and phenomenology of cosmic strings and superstrings.
22
questions
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Schwarzschild with cosmic strings: How can I visualize the string?
Geometrically, you can talk about a cosmic string in Schwarzschild black hole with this metric $[1]$:
$$ds^{2} = -\Big(1- \frac{r_{s}}{r}\Big) dt^{2} + \frac{1}{\Big(1- \frac{r_{s}}{r}\Big)}dr^{2} + ...
5
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3answers
119 views
Attraction near a straight cosmic string
I'm having an interpretational issue with the particles behavior around a straight cosmic string.
Consider the infinite cylindrical universe described by the following metric:
$$\tag{1}
ds^2 = dt^2 - ...
3
votes
1answer
72 views
Gravitational attraction/repulsion of cosmic strings and domain walls
It is well known that straight static cosmic strings don't produce any gravitational effects on test-particles, and that static flat domain walls are repulsive. This can be seen from the linearized ...
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2answers
208 views
Cosmic string solution to general relativity
I'm having a difficulty in finalizing a resolution of the Einstein equation for a static cosmic string. I start with the following metric ansatz, for a static straight string oriented along the $z$ ...
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1answer
50 views
What are the two different $\mathbb{S}^n$ in the construction of the homotopy group $\pi_n(\mathbb{S}^n)$ that classifies topological defects?
According to Mukhanov's Physical Foundations of Cosmology,
Homotopy groups give us a useful unifying description of topological defects. Maps of the $n$-dimensional sphere $\mathbb{S}^n$ into a ...
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0answers
19 views
Waves velocity on a cosmic string
I'm trying to understand a few things about cosmic strings in cosmology. Consider a single string of energy density $\rho$ and tension $\tau > 0$. I don't assume $\tau = \rho$, as apparently most ...
1
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1answer
97 views
Straight cosmic string energy-momentum tensor and the cosmic strings EoS
Consider a simple infinite straight "cosmic" string of negligible thickness, in flat spacetime. The string energy-momentum tensor has the following components (in the string proper frame, ...
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0answers
41 views
How to create a cosmic string?
I know about cosmic strings. They are 1-D topological defects in space-time which may had been created during the symmetry breaking phase transition during the big bang. But my question is : Are ...
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0answers
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Gauge cosmic strings and large gauge transformations
I've been going around in circles (hah) about how gauged cosmic strings work (I've been using Preskill's notes for the most part). The global string scenario makes sense to me, since different points ...
6
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1answer
98 views
Does Goldstone theorem have anything to do with Cosmic string
Cosmic strings are formed due to topological defects during symmetry breaking phase transition in early universe.
While Goldstone theorem states whenever we have continuous symmetry and it is ...
1
vote
1answer
42 views
How many cosmic strings are there in the Universe?
While researching cosmic strings, one often encounters terminology ranging from "scaling solutions" to "correlation lengths". As a newcomer, one of the first questions I have had is "how many cosmic ...
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1answer
49 views
Cosmic strings and ground state degeneracy in SSB
There are two conflicting perceptions that I have regarding the notion of ground state post-SSB. Consider the Higgs mechanism e.g. for the electroweak theory.
On the one hand, we say that the vacuum ...
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3answers
302 views
What's the connection between cosmic strings and the strings hypothesized in string theory?
I read somewhere that Edward Witten, the (once) big hotshot of string theory, said that the discovery of cosmic strings (at the beginning of this Wikipedia article it is written: "Not to be confused ...
2
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1answer
152 views
What is a String Wall?
This question has nothing to do with sound waves, physical strings or walls...
I am reading: https://arxiv.org/abs/1709.07091
It states
"In the post-inflationary PQ symmetry breaking scenario, ...
0
votes
1answer
75 views
I've read a cosmic string can accelerate a mass. Can someone explain how it works?
In the book Brief Answers to the Big Questions: the final book from Stephen Hawking Hawking describes cosmic strings as follows;
They are like rubber bands as they are under great tension, ...
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0answers
39 views
Candidates for cosmic strings
What are the observed candidates for cosmic strings (or other defects), that are not ruled out? With references if possible.
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91 views
Black hole and the cosmic string
For a regular black hole, the mass and energy of the black hole are identical（according to first law of black hole thermodynamics), but for a black hole with a cosmic string this is not satisfied. ...
3
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0answers
82 views
Basic question on Cosmic Strings
What is the typical size of Cosmic String Loops?
If a loop is formed today, what are the restrictions on its size?
I would like to know if there is a distribution of cosmic strings depending on its ...
5
votes
1answer
181 views
Gravitational lensing and cosmic strings
Say we have a straight cosmic string lying along the $z$-axis, with energy-momentum tensor
$$T_{\mu\nu}=\mu\delta(x)\delta(y)\operatorname{diag}(1,0,0,-1)\tag{1}\label{1}$$
for some small positive ...
2
votes
1answer
166 views
Kalb-Ramond action and topological string radiation
Let's have simple scalar $\Phi$ action involves spontaneously symmetry breaking in a form
$$
\tag 1 S = \int d^{4}x\left( |\partial_{\mu}\psi|^{2} + \psi^{2}|\partial_{\mu}\theta |^{2} - \frac{\lambda}...
2
votes
1answer
96 views
Global cosmic strings evolution
Recently I've read about axion string. It can be shown that the energy per unit length of the string located along $z$ axis is
$$
\mu = 2 \pi f_{a}^{2}\ln\left( \frac{L}{\delta}\right),
$$
where $L$ ...
0
votes
2answers
190 views
Cosmic string & grandfather paradox
Cosmic string was proposed several decades ago and there are claims stating it can span across the length of the universe and is less than an atom thick. How does a broken pieces of these cosmic ...
