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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Negative mass particle [closed]

Im not professional and few years back I came up with theory related to negative mass. I know this subject was up 2 years ago but every post I saw was about negative mass as it's own and it would ...
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If everything in the universe is drifting away will We eventually be able to register things disappearing?

If everything in the universe is slowly drifting away how soon before we see signs of this?Maybe we’ve already registered things at the visible edge of the universe disappearing. If not will, it ever ...
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Is it possible for matter to occupy a singularity, which is the point of rupture of space time caused by a black hole?

Also, are singularities caused by blackholes reversible? May one do work to reverse the singularity or black hole? Do blackholes create permanent holes in space time, thereby shrinking space time, or ...
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Energy is conserved. Dark energy has a fixed value per volume. The universe is expanding. Is non-dark energy decreasing? [duplicate]

I was thinking about this yesterday. Basically, these three premises: The amount of energy in the universe is conserved. Dark energy is a fixed number of joules per cubic meter. The universe is ...
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What is the evidence that dark energy exists? (as of 2020)

Astrophysicists believe that dark energy exists and makes up ~70% of the universe's energy content. What is the evidence that dark energy exists? Wikipedia gives five lines of evidence: Supernovae. A ...
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Models of accelerated expansion

Are there models of accelerated cosmological expansion that involve a changing number of spatial dimensions? I think I've seen a version of string theory that posits a reduction to quasi-3 dimensions ...
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Gravity against dark energy

If inflation of space makes stars and galaxies move apart from each other and gravity does the oposite, what happen to clusters of galaxies that aten't so close to get no effect of dark energy but ...
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Expansion of the relation between the cosmological growth factor and scale factor

Hello i'm studying large scale structure of the Universe (in $\Lambda$CDM Universe) using as time the growth factor defined by $$ \ddot{D}+2H\dot{D}-4\pi G\bar{\rho}_{DM}D=0$$ in my equations i have ...
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What is the largest gravitationally bound structure in the universe?

I understand the galaxy superclusters are not bound due to dark energy. I wonder what matter scale will remain gravitationally bound - galaxy clusters, galaxies, stars - if anything at all, as dark ...
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Does an alternative explanation exists for the observed structure of matter in the universe instead of the dark energy explanation? [closed]

I asked in this question if type Ia supernovae could be different in the past. According to me, this would imply that the existence of dark energy would not be so certain. After reading the answer ...
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How can one be sure that type-Ia supernovae have constant properties in time?

In this Wikipedia article there can be much read about type-Ia supernovae. One can read: This type Ia category of supernovae produces consistent peak luminosity because of the uniform mass of white ...
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What is dark parity?

What is the physical significance of the odd dark parity and even dark parity? Does it mean if a particle has odd dark parity then it is not a dark matter candidate?
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Cosmological lookback time equation and LCDM fits

When performing the lookback time integral and fiting the know Omega parameters, has someone tried to change not the DM but the DE for other w and see if we can find a best data fit?
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Will atoms evaporate given enough time?

Thought experiment: someday in the distant future, space will be expanding faster than the speed of light. Imagine that trillions of years in the future, you have a single hydrogen atom. Will that ...
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Can gravity be conceived of as 'repelling' regions of lower energy density?

*I'm a writer, not a physicist, so please bear with me in my 'ham'-handling of physics and its terminology! My question is about whether repulsive forces over large distances could exist. My ...
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Does this paper falsify the vacuum energy? [duplicate]

If Dark Energy is falsified by this paper, https://arxiv.org/abs/1808.04597, does that mean the vacuum energy is also falsified?
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Is there any other explanation for the expansion of the universe other than dark energy? [closed]

Why did the universe expand from the Big Bang singularity? If gravity was a separate force and in its current form by 1 Plank time, would not have gravity prevented expansion, unless there was some ...
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Why is de Sitter spacetime a better model of our universe than brane world models?

Why is it assumed that we live in a de Sitter space-time? Besides the de Sitter Lambda Cold Dark Matter model, there are Anti de Sitter brane world models, which also generates Friedmann equations ...
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Extracting energy from the universe's expansion using gravitational waves

Would it be possible to extract energy from the universe's expansion by having two massive bodies orbit each other in such a way that their rate of infall due to emitting gravitational waves is ...
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If universe was instead cosmological blueshifted, would we still notice dark energy?

Imagine instead of us seeing more distant galaxy turning redder, they now becomes more blue at a similar rate. This time round would we be able to notice those mythical dark energy? I suppose missing ...
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Gravitational non-linearities and Dark Matter/Energy

I had read Significance of Gravitational Nonlinearities on the Dynamics of Disk Galaxies (https://arxiv.org/abs/1909.00095), was wondering Is there good reason to think that gravitational non-...
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Dark energy time dilation

I have read here that dark energy is somewhat like negative mass. Here Wikipedia states: ... that the cosmological constant required that 'empty space takes the role of gravitating negative masses ...
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Is the GW170817 event evidence or counter evidence for Dark Energy?

I've always figured there must be a simpler explanation for the observed extra red shifting that has lead astronomers to hypothesize Dark Energy. Or at least there must be a simpler explanation of ...
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Quantum tunneling of dark energy from black holes

There was an article posted recently suggesting there is a very deep connection between dark energy and black holes. https://phys.org/news/2019-09-black-holes-dark-energy.html I was thinking this ...
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What do the terms attractive and repulsive gravity mean in Einstein's GR?

What does the jargon repulsive gravity mean in Einstein's GR or even attractive gravity in the same framework? The notions of attractive and/or repulsive only makes sense, or at least we are ...
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Good references to start researching on dark energy knowing only graduate general relativity

I'd like to research on Dark Energy, but I only know (Schutz-Foster-Carroll) general relativity. Can anyone indicate to me some good books to start to research this topic? I'm interested in how to ...
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Why did dark energy play a subdominant role in the radiation and matter dominated era?

After inflation, the Universe passed through radiation dominated (RD) and matter dominated (MD) era during both of which the evolution of the scale factor (or the Hubble parameter) was decreasing with ...
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Negative pressure in general relativity

Is there an intuitive way to understand what negative pressure means in general relativity in the same way as positive pressure can be thought to be kinetic energy of gas particles? Dark energy has ...
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Gravity as a repulsive force

As we know that universe is expanding, why can't we think the gravitational force as repulsive in nature in the realms of dark matter and dark energy?
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“Cosmological constant problem” and dark energy

Simply stated: is the "cosmological constant problem" (the discrepancy of about 120 orders of magnitude between measured values of vacuum energy and the ones predicted by Quantum Field Theory) in any ...
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Quintessential models for dark energy

Following Sean Carroll here There are good reasons to consider dynamical dark energy as an alternative to an honest cosmological constant. First, a dynamical energy density can be evolving slowly ...
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How much dark energy will fit in an average cup of coffee? [closed]

I am looking for the answer in Joules for obvious reasons.
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Accelerating Universe and dark energy or photon absorption or neergy decay?

I’m an RF/microwave engineer with physics background, and had a question regarding dark energy and experimental observations. FYI I don’t qualify as a professional physicist, hence asking a ...
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Is the “cosmological constant tension” the prime reason that we believe the expansion of the universe is accelerating?

Background: For a few years now there is significant difference in the calculation of the cosmological constant between standard candles methods and CMB methods. CMB measurement comes from a very ...
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How do we know that Dark Energy has homogeneous energy density? [duplicate]

I’ve read places that the density of Dark Energy is the same throughout the universe. If the expansion density of dark energy were the same throughout the universe, why don’t all galaxies have the ...
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Could decaying dark energy solve the Hubble tension? [closed]

The redshift-based distance ladder values of the Hubble constant are higher than that inferred by the cosmic microwave background. This discrepancy in the last few years has become highly ...
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What's the difference between “dark energy” and “vacuum energy”?

Let's see if I understood well. "Dark energy" is a term that encapsulates everything that may be accelerating the expansion of Universe, and "vacuum energy" is a kind of energy that permeates the ...
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Justification for “running” cosmological constant

I am looking for papers which seek out to justify that the cosmological "constant" could be time-dependent. I am aware that within the framework of GR the cosmological constants really has to be a ...
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Why Does the amount of gravitational potential energy in the universe increase as it expands?

Ok so this is my thought process... please bear with me I understand that as the universe expands, there is supposed formation of matter due to dark energy,and with an increase in mass comes and ...
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What if there was no baryon-antibaryon asymmetry in our universe?

We know that the universe goes through different evolutionary phases: radiation, matter and later dark energy epoch. What would happen if there was no baryon-antibaryon asymmetry? How would the ...
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Superposition of gravitational waves and the dark energy

Is it theoretically possible to create a superposition of gravitational waves that form a locally static negative curvature, something like the dark energy?
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Where does negative pressure in dark energy arise?

In the 2nd friedmann equation, the pressure term of dark energy is what counteracts the energy density and cause acceleration of the expansion of universe. But normal pressure gradient arises from the ...
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Field equations with cosmological constant

Is it enough to add the cosmological constant in the einstein field equations to guarantee that the obtained solution describes an expanding universe?
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Is the acceleration of the expansion of the universe caused by expansion of spacetime itself?

When considering the accelerating expansion of the universe, it is often stated that dark energy is required to cause acceleration of expansion in order to overcome the pull of gravity. However, it ...
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What is really a negative energy particle (and why is it different from an anti-particle)?

I have read this question: What is negative Energy/Exotic Energy? This does not really give an answer. Why does a particle (charged) change sign passing the event horizon? Black holes and positive/...
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What theories purport to describe “physical-level understanding” of dark energy?

What theories propose to close the gap (as suggested by http://arXiv.org/abs/1210.6008) between 'phenomenological behavior of dark energy' and 'physical-level understanding of dark energy' and to what ...
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Volume of dark energy in space [duplicate]

As I understand it, Dark Energy is believed to reside in empty space. As the Universe exapnds, more empty space exists inside the Universe and so the small energy per unit of empty space adds up to a ...
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Correction to Newton's law of Gravity for dark energy

Is there any correction to Newtons law of Gravity that takes into account the expansion of the universe?
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How do they know the numbers of the energy pie chart of the universe?

They say that the total energy of the universe consists of 4.9\% ordinary matter, 26.8\% dark matter and 68.3\% dark energy. I hear this pie part in virtually every lecture in cosmology. How do we ...
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What are the units of dark energy?

Popular literature seems to equate dark energy with the cosmological constant of the Einstein field equations. We know however that the dimensions of any constituent of the field equations is ${\rm ...

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