The Stack Overflow podcast is back! Listen to an interview with our new CEO.

Questions tagged [de-sitter-spacetime]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
1answer
38 views

What is the Komar mass of the de-Sitter spacetime?

The Komar mass of some spacetime is defined as an integral (volume or surface, depending on its formulation): https://en.wikipedia.org/wiki/Komar_mass The de-Sitter metric in static coordinates is ($\...
3
votes
0answers
71 views

Negative temperature of the de-Sitter horizon?

I'm considering the $4D$ de-Sitter spacetime, in static coordinates (I'm using $c = 1$ and $k_{\text{B}} = 1$): \begin{equation}\tag{1} ds^2 = (1 - \frac{\Lambda}{3} \, r^2) \, dt^2 - \frac{1}{1 - \...
2
votes
0answers
62 views

Entropy of de-Sitter spacetime and the $10^{120}$ vacuum discrepency

While doing some lazy calculations, I came across a curiosity that I'm unable to interpret. It is well known that the cosmological constant $\Lambda \sim 10^{-52}~\mathrm{m^{-2}}$ is usually ...
1
vote
0answers
19 views

dS/CFT in a positive curvature universe

Since Maldacena ground breaking theoretical discovery, have there been any succesfull efforts to try to transpose the AdS/CFT duality to our universe (not an AdS)?
1
vote
0answers
19 views

Symmetry v.s. isometry of Minkowski and AdS or dS spacetime

We know some nice spacetime have a lot of symmetries. It is said that Minkowski spacetime has $$ISO(d-1,1)/SO(d-1,1),$$ de Sitter spacetime has $$SO(d,1)/SO(d-1,1)$$ and anti-de Sitter spacetime ...
0
votes
1answer
23 views

In de Sitter space, does the cosmic horizon change its shape for fast-moving observer?

If an observer moves at a speed close to the speed of light, will the horizon deviate from spherical shape? If no, will it be the same horizon as for stationary observer (at the same position)?
1
vote
0answers
30 views

Given in de Sitter space time is frozen on the horizon, can we say that in anti-de Sitter space time goes infinitely fast at the space boundary?

Particularly, in de Sitter space everything on the cosmic event horizon is redshifted, while in anti-de Sitter space everything on the horizon is blueshifted.
0
votes
0answers
12 views

Gravitational contribution to the action for Coleman-de Luccia instanton?

In the Coleman-de Luccia calculation of the transition rate from one de Sitter minimum to another, the action for the scalar field $\phi(\xi)$ and Euclidean radius $\rho(\xi)$ is $S_E = 2\pi^2 \int \...
1
vote
1answer
77 views

Minkowski space vs De Sitter Space

Can you explain to a layman the differences between the former two?
0
votes
1answer
84 views

Does an observer inside a black hole experience the de Sitter metric?

My question has emerged, because of the following similarities between the metric an observer experiences in the Schwartzschild space being under the Schwartzschild radius and an observer in the de ...
0
votes
0answers
23 views

Is there a de Sitter or FRW collapse solution for black holes, similar to the Oppenheimer-Snyder-collapse?

I know the Oppenheimer-Snyder-solution and the formation of the black hole event horizon during the collapse. Is there a similar solution for a dynamical collapse, embedded in asymptotic de Sitter ...
0
votes
0answers
56 views

How accurate is the De Sitter solution of the Einstein field equations of general relativity?

The De sitter solution models the universe as spatially flat, neglecting ordinary matter, such that it is dominated by the cosmological constant. The cosmological constant notion arguably suggests the ...
2
votes
0answers
32 views

How is deSitter group tranformations different from poincare group transformations

In QFT, we have studies Poincare group of massive and massless particles. Is the deSitter group also useful to study such things? What exactly is the main role of this group in QFT? I just know the ...
2
votes
4answers
194 views

What would happen to de Sitter universe if the cosmological constant disappears?

De sitter universe is dominated by a cosmological constant (devoid of matter and radiation), corresponding to dark energy in the far future or the inflaton field in the early universe, leading to an ...
0
votes
0answers
25 views

2D deSitter conserved charges

For $1+1$-dimensional dS spacetime, the metric takes the form (in comoving coordinates) $$\mathrm{d}s^2=\left(\mathrm{d}x^0\right)^2-e^{2Hx^0}\left(\mathrm{d}x^1\right)^2.$$ I want to find the ...
0
votes
0answers
48 views

deSitter spacetime metric and curvature

I have to compute the metric of an hyperboloid given by $-(X^0)^2+(X^1)^2+(X^2)^2+(X^3)^2=H^{-2}$ in 5D Minkowski spacetime using the following coordinates: $$X^0=H^{-1}\sinh(Ht)\sqrt{1-H^2r^2}$$ $$X^...
0
votes
1answer
58 views

$dS^d$ and $AdS^d$ are conformally equivalent

I have seen in the book by Zee (Einstein Gravity in a Nutshell) the following metric for $dS^4$: $ds^2 = \frac{1}{\cos^2 \tau} \big( - d\tau^2 + d\psi^2 + \sin^2 \psi \, d\Omega_2^2 \big) $, (Eq. IX....
2
votes
1answer
73 views

Why $dS^d \cong SO(d,1)/SO(d-1,1)$?

I have found a similar question, but there they give a seemingly rigorous proof, and what I am looking for is just an intuition. I understand that $S^2 \cong SO(3)/SO(2)$: for every point in $S^2$ ...
3
votes
1answer
318 views

Metric for 2D de Sitter?

What is the correct metric to use for two dimensional de Sitter? If one starts with the following metric, which looks similar to de Sitter in 4 dimensions: $$ds^2 = -dt^2 + e^{2H t} dx^2,$$ one can ...
1
vote
1answer
94 views

Lorentz transformations in non-Euclidean geometries

I have an assessment/investigation coming up in my math class and I plan to investigate Lorentz transformations in geometries other than Euclidean such as spherical or hyperbolic. For spherical/polar, ...
3
votes
0answers
93 views

Strings 2018 takeaways [closed]

What are the main takeaways from the Strings 2018 conference? What are the main announcements, discoveries or directions emerging from this event? To my knowledge, one is the result by Vafa and ...
1
vote
0answers
110 views

If the Schwarzschild radius of the universe is bigger than the universe, how come the universe didn't collapse into a black hole? [duplicate]

According to this answer, the Schwarzschild radius of the universe is about 3 times the radius of the universe. According to the Newtonian theory of gravity, inside any sphere of a given density, the ...
1
vote
2answers
1k views

Why is our physical Universe a de Sitter space?

Wikipedia says, When $n=4$ (3 space dimensions plus time), it is (the de Sitter space) a cosmological model for the physical universe; see de Sitter universe. It appears to me that the statement ...
0
votes
1answer
291 views

Maximally symmetric spaces

In GR, what is the most precise definition of a maximally symmetric spacetime? Also, we study about the temporal boundary of dS space, and a spatial boundary of AdS space, but aren't these spaces ...
0
votes
0answers
61 views

De sitter spacetime and co-ordinates

I was recently looking at de - Sitter spacetime and I relaized that there are many different parameterizations possible, each of which has it's own advantages. Can someone help me out and list the ...
4
votes
2answers
555 views

Can String Theory really fail to contain a de Sitter vacua?

I was reading a post earlier from Peter Woit's Not Even Wrong blog and came across the following reference to the paper "What if string theory has no de Sitter vacua?" by Ulf H. Danielsson, Thomas Van ...
2
votes
1answer
39 views

Can a De Sitter universe have a detectable rotation?

In De Sitter relativity, the cosmological constant becomes a geometric term with the dimensions of radius, and the universe becomes a pseudo-sphere. Is it meaningful to speak of intrinsic rotation of ...
1
vote
2answers
236 views

Is the dynamics of spacetime observer-dependent?

Consider de Sitter spacetime in static coordinates: $$ ds^2 = \Big(1- (H_\Lambda r)^2 \Big) dt^2 - \frac{dr^2}{1- (H_\Lambda r)^2} -r^2 d\Omega^2, \qquad r\lt H_\Lambda^{-1} \,. $$ This metric ...
5
votes
1answer
221 views

Holography on non-AdS spacetime

I have a question regarding AdS/CFT and what it teaches about our world. AdS/CFT if often treated as our best tool to explore quantum gravity, and people have worked very hard in trying to understand ...
2
votes
1answer
218 views

Issues with de Sitter Space and Conformal Field Theory

As a de Sitter universe is more convenient for cosmology, what are the current issues with a dS/CFT type correspondence? Earlier work by Strominger, seemed promising but I haven't heard of additional ...
6
votes
2answers
1k views

Is the de Sitter Universe static?

In the book Tolman R.C. Relativity, thermodynamics, and cosmology (3pr., Oxford, 1949) I read that the de Sitter Universe is static as well as the Einstein Universe. But the de Sitter Universe is ...
0
votes
1answer
400 views

Is the de Sitter Universe equivalent to the static Einstein Universe?

The de Sitter universe is a flat exponentially expanding universe with a cosmological constant $\Lambda$ and no matter. Einstein's static universe also has a cosmological constant $\Lambda$ but it ...
1
vote
0answers
39 views

What coordinate system produces this particular form of the line element of de Sitter spacetime?

To save space, all the symbols and conventions are adopted from this Wikipedia article. We know that the line element of $n$ dimensional de Sitter space in static coordinates is $$ds^2=-\bigg(1-\...
0
votes
1answer
902 views

Is de Sitter space with non-zero curvature an acceptable model for the universe?

On wikipedia I can find that a de Sitter-space has maximal symmetry and a constant curvature. Recently the interest of de Sitter spaces has increased as it could serve as a model for the universe, an ...
1
vote
0answers
41 views

Is there a homogeneous $\Lambda$-vacuum spacetime with spatial topology $\mathbb{R}^2\times S^1$?

This question is about homogeneous $\Lambda$-vacuum spacetimes. The unique isotropic solution is de Sitter space, which has the spatial topology of $\mathbb{R}^3$. There is the Kantowski-Sachs metric, ...
2
votes
0answers
107 views

Does the curvature parameter $k$ change with coordinate choice (de Sitter spacetime)?

The de Sitter spacetime can be derived from the vacuum Friedmann equations given a choice of $k=0$, where $k$ defines the spatial curvature of the spacetime. The resulting metric in $(t,x,y,z)$ is ...
5
votes
0answers
91 views

de-Sitter spacetimes

In classical textbooks for GR, Schwarzschild and Kerr spacetimes are adequately described. In which books or articles, it is mostly believed that Reissner-Nordstrom, Kerr-Newman, Schwarzschild-de ...
2
votes
3answers
186 views

Large $D$ limit of (Anti) de Sitter Space is Minkowskian Space?

As is well known, the solution of the vacuum Einstein equations with a non-zero cosmological constant, $G_{\mu\nu}+\Lambda g_{\mu\nu}=0$, is an asymptotically (anti) de Sitter space based on the sign ...
6
votes
0answers
2k views

A Universal Upper Limit on Mass Within a Radius $R$?

Since the universe has a positive cosmological constant, there is an upper limit on the mass of the black holes as evident from the so-called Schwarzschild-de Sitter metric: $ds^2 = -f(r)dt^2 + \...
4
votes
1answer
144 views

How does one write a three dimensional de Sitter space as the quotient $SL(2, C)/SL(2, R)$?

In arXiv:hep-th/0110108 the $(2+1)-$dimensional de Sitter space is represented as a quotient space of $SL(2, C)/SL(2, \mathbb{R})$. I couldn't understand how, both mathematically and intuitively, is ...
0
votes
1answer
159 views

Totally geodesic spacelike surfaces in de Sitter space

Let $S^2_1$ be the de Sitter space $$\{x:\langle x,x\rangle=x_0^2-x_1^2-x_2^2-x_3^2=-1\}$$ in Minkowski space $\mathbb {R}^3_1$ with $ds^2=dx_0^2-dx_1^2-dx_2^2-dx_3^2$. Is it true that for each pair ...
1
vote
1answer
654 views

What are the de Sitter Killing vectors?

I'm trying to find the Killing vectors for de Sitter space using global coordinates, i.e. the spherical foliation. In the end, I want to know how to perform a boost on the 1+1 and 3+1 de Sitter ...
6
votes
1answer
340 views

Entropy of the de Sitter cosmological horizon

For an eternal dS universe, the entropy of an observer in the static patch goes as the area of the horizon which for 3+1 D goes as $S_H = \frac{Area_{H}}{4} \sim H^{-2}$, as given by Gibbons & ...
2
votes
0answers
190 views

Lapse Function and Shift Vector in Minkowski and de Sitter

I'd like to find the lapse function and shift vector in 1+1 Minkowski as well as 1+1 de Sitter (flat foliation) for a region foliated this way: The $y$-axis represents time while the x-axis ...
2
votes
1answer
193 views

de Sitter reviews?

I'm very interested in learning more about de Sitter and anti-de Sitter spaces and their applications in GR and cosmology. Can anyone recommend favorite review articles -- or, more likely, a series ...
6
votes
3answers
1k views

If the expansion of the Universe accelerates, why its horizon does not shrink?

In de Sitter (expanding) universe to which our universe asymptotically approaches, the higher the rate of space expansion, the smaller the radius of the cosmic horizon. Why then our universe is ...
6
votes
2answers
241 views

Are orbits possible in de sitter space?

Since the de sitter space has constant positive curvature does that mean that objects can't orbit around other objects?
3
votes
1answer
300 views

Why $C_{abcd}C^{abcd}$ in de Sitter–Schwarzschild metric doesn't depend on $\Lambda$

With the de Sitter–Schwarzschild metric: $$ds^2=-\left(1-\frac{2M}{r}-\frac{\Lambda r^2}{3}\right)dt^2+\left(1-\frac{2M}{r}-\frac{\Lambda r^2}{3}\right)^{-1}dr^2+r^2d\theta+r^2\sin^2\theta d\phi$$ I ...
1
vote
2answers
188 views

Why can only asymptotically flat and AdS black hole have the thermodynamics? What's about asymptoticaly dS black hole?

Almost all advanced GR textbooks will have the content of black hole thermodynamics for asymptotically flat black hole. And this paper solve the asymptotically AdS (Anti-de Sitter) black hole http://...
3
votes
0answers
281 views

How to find de Sitter and almost de Sitter solutions in (super)string theory

From Cosmology, we have learned that we live in an almost de Sitter (positively accelerated!) Universe. It seems that dS space solutions in superstring/theory are problematic and there are some no-go ...