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, ...
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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:
$$H(t)^2 = \left(\frac{\dot a}{a}\right)^2 = \frac{8\pi G \...
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Age of a dark energy dominated universe
In a flat universe that is dominated by dark energy (or cosmological constant), the Friedmann equation can be written as:
$H^2 = (\frac{\dot a}{a})^2 = \frac{8\pi G\varepsilon_{\Lambda}}{3c^2}$
Where $...
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Dark energy and conservation of energy in General relativity [duplicate]
i know that conservation of energy in general relativity has been discussed multiple times here at PE, a popular explanation on the topic is Sean Carroll's blog "Energy is not conserved" ...
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If space has a positive curvature, is the expansion of the universe caused by time, not "dark energy"? [closed]
Ok, I will assume that space has a positive curvature, where space is the "surface" of this sphere, and time is the radius from the center, so the universe is a 4D hypersphere. Under these ...
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Do we really know the universal gravitational constant?
We've all heard $$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 ...
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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 ...
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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 ...
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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 ...
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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....
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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 ...
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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) ...
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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 ...
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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 ...
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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 ...
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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 $$\...
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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, ...
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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 ...
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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'...
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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/...
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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 ...
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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 ...
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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 ...
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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 ...
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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 (...
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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 ...
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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?
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