All Questions
Tagged with dark-energy cosmological-constant
128
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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, ...
- 1,431
10
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531
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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 $...
- 455
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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 ...
- 403
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128
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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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70
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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 ...
- 117
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102
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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 ...
- 163
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3
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164
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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 ...
- 5,148
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96
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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, ...
- 149
2
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3
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189
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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'...
- 131
3
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503
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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 ...
- 149
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72
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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 ...
- 2,472
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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 ...
- 4,170
-3
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84
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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 ...
- 4,170
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40
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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 ...
- 23
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In the $\Lambda$CDM model, is the cosmological constant always interpreted as the vacuum energy contribution?
As in the title, in the $\Lambda$CDM model, is the cosmological constant always interpreted as the vacuum energy contribution? Or is the origin left open?
If I say that "it is usually ...
- 299