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Questions tagged [dark-energy]

Dark energy is the unknown form of energy that drives the acceleration of the universe's expansion.

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Is the dark energy equation of state constant over time?

There are plenty of questions and answers here about what the dark energy equation of state (EoS) parameter $w_{de}$ is and, its impact on the future of the Universe, if if happens to be $w_{de} = -1, ...
Mr Anderson's user avatar
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Can Poincaré recurrences happen eventually in a universe with zero vacuum energy?

I am interested in the topic of possible vacuum up-tunneling and down-tunneling events in cosmology. One popular instance of this is a vacuum decay from a metastable vacuum energy level to a "...
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Beginning of a dark energy (cosmological constant) dominated universe

Consider a flat universe with only dark energy (cosmological constant) In such universe, the Friedmann Equation can be written as: $$H(t)^2 = \left(\frac{\dot a}{a}\right)^2 = \frac{8\pi G \...
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Age of a dark energy dominated universe

In a flat universe that is dominated by dark energy (or cosmological constant), the Friedmann equation can be written as: $H^2 = (\frac{\dot a}{a})^2 = \frac{8\pi G\varepsilon_{\Lambda}}{3c^2}$ Where $...
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Dark energy and conservation of energy in General relativity [duplicate]

i know that conservation of energy in general relativity has been discussed multiple times here at PE, a popular explanation on the topic is Sean Carroll's blog "Energy is not conserved" ...
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If space has a positive curvature, is the expansion of the universe caused by time, not "dark energy"? [closed]

Ok, I will assume that space has a positive curvature, where space is the "surface" of this sphere, and time is the radius from the center, so the universe is a 4D hypersphere. Under these ...
Rick Gennings's user avatar
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Do we really know the universal gravitational constant?

We've all heard $$F_g=\frac{gm_1m_2}{r^2}.$$ However, since I took physics, we've discovered "dark energy," which if I have any concept of the current thinking is caused by space being ...
Cristobol Polychronopolis's user avatar
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Could the increasing anisotropy of the universe lead to an additional blueshift?

I'm contemplating the possible sources of a wavelength-shift within our universe: The CMB had a lot more energy when it was produced (around 3000 K). Due to the expansion of the universe, it has been ...
MartyMcFly's user avatar
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Does dark energy work on the principle of anti-gravity, i.e. repulsive gravity?

Our universe is made up of 95% dark energy+ dark matter (of which most is dark energy), and this dark energy is considered to be the main reason for the expansion of our universe. But, anything that ...
Sambhav Khandelwal's user avatar
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Different types of Dark energy and conservation of energy

According to this Sean Carroll article, and other threads in here, depending on your definition of energy, dark energy does not violate conservation of energy. My question is if this is true ...
FACald's user avatar
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Relation between energy of cosmic inflation and dark energy

Searching for "relation between inflation and dark energy" I found: "The energy scale of inflation is possibly 10^24eV, while the energy scale of dark energy is around 10^-3eV." e....
qatch's user avatar
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If dark energy has constant density, would it still be subject to quantum variations; would increase/decrease be symmetrical, or would one take over?

There are different suggestions, but it stills seems like the basic scenario is for dark energy to have constant density, as a property of space (and as represented by the cosmological constant in ...
Atlantis Vel's user avatar
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Question on linear perturbations in cosmology

I've been studying clustering dark energy when I came across a paper named "A Short Review on clustering dark energy" by Ronaldo Batista. there are 2 equations in this paper (eq.8 and eq.9) ...
Arian Esmaieli's user avatar
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Does dark energy get used up in the expansion of the universe?

Now, I am a beginner in Cosmology, so I am not sure if this makes sense. Since the universe is expanding at an accelerating rate, and thus distant objects are also accelerating away. In that sense, ...
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Sign and physical meaning of the cosmological constant

I've heard that a cosmological constant can be used to model dark energy (e.g. $\Lambda$-CDM model), and that the constant $\Lambda$ should be positive. But my (quite small) understanding of dark ...
Chris's user avatar
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Why are dark matter and dark energy favoured over changes to our physical models? [closed]

I am instinctively skeptical of the existence of "dark matter" and "dark energy". Together, they strike me as being analogous to luminiferous aether -- something that was invented ...
spraff's user avatar
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Does dark energy increase tidal forces in cosmic voids...?

I would like to ask you some questions I have about some interesting work I was reading (https://arxiv.org/abs/1205.4238 & https://academic.oup.com/mnras/article/527/4/11962/7457744) where the ...
vengaq's user avatar
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Klein-Gordon equations in quintessence

I'm studying the quintessence model from a dynamical system point of view. I denoted the scalar field for the dark energy as $\phi$, so I have the following Klein-Gordon equation for the field $$\...
Guillermo García Sáez's user avatar
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Measurement of the Cosmological Constant

Is there some way to measure Lambda, the cosmological constant, independent of $H_o$, the Hubble constant and omega_lambda, the Dark Energy density? A standard equation for calculating Lambda, ...
user86742's user avatar
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If the observable universe had only one galaxy, how would people know the expansion of the universe?

Hubble measured high redshifted galaxies to discover the cosmic expansion. In a hypothetical universe where only one galaxy exists, would there still be observational evidence for the Big Bang theory? ...
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Electromagnetic field pressure

Wikipedia gives that maxwell tensor components have minus in the electromagnetic stress energy tensor https://en.wikipedia.org/wiki/Electromagnetic_stress%E2%80%93energy_tensor. That mean the ...
Lexorde's user avatar
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Will cosmic microwave background become invisible in the future?

If my understanding of CMB and Hubble's Law is correct, then CMB photons emitted from more than ~14.4 Glyr during Recombination Epoch would not reach us. The reason is this would correspond to Hubble'...
FritzS's user avatar
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Does the accelerated expansion of the universe have any effects in the orbital precession of galaxies? And in their eccentricity?

I found several papers (https://iopscience.iop.org/article/10.3847/2041-8213/ace90b; https://link.springer.com/article/10.1134/S1063772920100054; https://arxiv.org/abs/gr-qc/0301057; https://arxiv.org/...
vengaq's user avatar
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Does energy exist on its own? [closed]

So to my understanding as a layman is that energy transfers from one material to another (I guess that's why there's potential and kinetic energy), for example photons to solar panels. Now my question ...
Ed_Gravy's user avatar
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Cosmological constant, dynamical friction and structure formation?

I would like to ask a question about an interesting article that I found (https://repositorio.unesp.br/server/api/core/bitstreams/b8a5a5b8-4b3b-4198-9f5d-bf69431db1ae/content) In the context of ...
vengaq's user avatar
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Ejected bodies, dynamical friction and dark energy?

I have a question after reading a couple of papers (https://arxiv.org/abs/1707.06220 and https://www.arxiv-vanity.com/papers/1102.0007/). Here, the authors seem to indicate that when bodies like stars ...
vengaq's user avatar
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Does dark energy have mass?

For personal writing purposes, I’ve been researching dark energy, amongst other similar subjects. I’ve found it hard to discern whether or not we have any conclusive answers or generally accepted ...
Wasteland Vassal's user avatar
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2 answers
143 views

Suppose the universe from our big bang is surrounded by many distant blackholes with each a mass of sextillions of suns. Could it explain dark energy?

Could dark energy "simply" be from multiple distant universe-scale mass black holes, that are there "all-around" the big bang? Scattered apparently randomly, throughout infinity (...
MGamsby's user avatar
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Can a receding body due to the accelerated spacetime expansion be "rescued"?

Once a body "crosses" the limit where dark energy wins over gravitational forces (Is there a distance from a gravitational source where the influence of gravity and dark energy are balanced ...
vengaq's user avatar
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3 answers
108 views

Is Dark Energy Taking Over?

First question, trying to keep it simple 😃 Because it's constant it grows in magnitude as the universe expands, whereas normal matter does not? Is this accurate as far as we know?
Wileyo's user avatar
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Dark energy, bound systems and orbits...?

As far as I understand it, dark energy can affect bound systems at cosmological scales (How does dark energy affect the dynamics of galaxy clusters?) effectively modifying their orbits. This ...
vengaq's user avatar
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Does Dark Energy contribute to increase the isothermal temperature of plasma in galaxy clusters?

I have a question about this work called "Dark energy and key physical parameters of clusters of galaxies" There, towards the end, the authors talk about the isothermal velocities and ...
vengaq's user avatar
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Effects of dark energy in the kinetic energy of a body?

If I launch a ball into the sky it would reach a distance after which it would return into the ground transforming the potential energy into kinetic energy as it hits the ground This is similar to ...
vengaq's user avatar
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Tidal effects of galaxies orbiting one another in presence of dark energy?

I recently asked this question about whether there was a "distance" between two galaxies where both the gravitational force and the influence of dark energy would be balanced. The answers ...
vengaq's user avatar
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Theoretically, is it feasible for the dark matter density to be constant and homogeneous, as dark energy is, and the two to be related?

I know that currently dark matter and dark energy are separate things, not related and one not deriving from the other. But if both are included in a generalized gravitation theory, the picture can ...
Rahim's user avatar
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12 votes
1 answer
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Is there a distance from a gravitational source where the influence of gravity and dark energy are balanced out?

While gravity is a force that attracts objects with mass, dark energy (or, alternatively, the accelerated expansion of the universe) is not. However, I have found numerous articles, forums, questions ...
vengaq's user avatar
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1 vote
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Dark energy contributing to, or modifying, mass estimates?

I have found some papers (like this one: https://www.aanda.org/articles/aa/full_html/2009/45/aa12762-09/aa12762-09.html) which say that dark energy increases the potential energy in a system of a ...
vengaq's user avatar
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Casimir Effect & Redshifting

The classic plate experiment highlights how omitted wavelengths of light create an energy differential and pressure. This pressure is dependent on the distance between the plates, including how this ...
Eric Roche's user avatar
2 votes
2 answers
181 views

How does dark energy affect the dynamics of galaxy clusters?

Galaxies interact with each other gravitationally (just as every other celestial object) and in many cases they form groups or clusters. Does the expansion of the universe (or dark energy) affect the ...
vengaq's user avatar
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-5 votes
1 answer
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Is gravity just a repulsion coming from all directions? [closed]

Why not explain the apparent attraction of masses by a repulsion coming from all directions in space (perhaps the dark force)? I.e. there is no gravitational force, just a repulsive force. A point in ...
Leo's user avatar
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What is the formalism for calculating the vacuum energy density from the observed data of the expansion of the universe?

Wikipedia states here the calculated effective vacuum energy density value of free space from the observed and collected cosmological constant data of the 2015 Planck telescope satellite mission. But ...
Markoul11's user avatar
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What is the evidence against a variable gravitational constant? [duplicate]

I understand that our main supporting evidence for dark matter is the anomalous speed of objects orbiting around the edges of distant galaxies. Is there a reason why dark matter solves this problem ...
Miles Gould's user avatar
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1 answer
151 views

What if dark matter/energy did not exist?

What if dark matter and dark energy did not exist and were only due to a misinterpretation of the red shift of light or a measurement bias? What would be the implications/consequences?
Olandelie's user avatar
3 votes
2 answers
169 views

What is the correlation between the Hubble tension and Dark Energy?

When Dark Energy was first discovered it was because we noticed that distance type 1A supernovae were dimmer given their perspective redshifts. However, to determine the Hubble constant in the late ...
Python House's user avatar
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0 answers
44 views

What causes a big rip?

If dark energy has $w<-1$ you get the Big rip scenario, where dark energy becomes more and more powerful until it eventually rips all matter apart. Why does this occur? Why does having $w<-1$ ...
blademan9999's user avatar
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Does spacetime move? With respect to what?

Can spacetime itself rotate along a body, like a black hole? Would it move like a wave?
Antoniou's user avatar
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1 answer
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Can matter and light exist without the free space absolute vacuum?

According to the standard model of particle physics, is matter and light possible to exist without the existence of the omnipresent vacuum? By "vacuum" here I mean the ideal perfect vacuum ...
Markoul11's user avatar
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-1 votes
2 answers
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The speed of expansion of space in big freeze

In the case of big freeze, space expansion will be accelerating and there appears to be a lot of different phenomena occurring. However, in the case of big rip, the expansion is super-accelerating so ...
hi13's user avatar
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What exactly do astrophysicists mean when they say that the universe is expanding at an accelerated rate? [duplicate]

What exactly do astrophysicists mean when they say that the universe is expanding at an accelerated rate? Assuming that the universe is a sphere, do they mean that the radius of the universe increases ...
SPANDAN DASH's user avatar
3 votes
2 answers
502 views

What is the longest detectable EM wavelength?

What is the longest detectable (by today's technology) EM wavelength? and is there a limit of the energy that those with longer wavelengths that we cannot detect can carry? can there be a galactic or &...
USER249's user avatar
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