Dark energy Definition and 553 Threads

I am writing a 2nd year essay for my Physics degree, and have chosen dark energy as my topic. I've been reading papers and material for around a week now, and would like some reassurance that I am heading in the right direction and have made no major blunders or omissions. Here's the general...

http://arxiv.org/abs/astro-ph/0504416 Authors: Mustapha Ishak (Princeton University) Comments: 10 pages, 5 figures Associated with the cosmic acceleration are the old and new cosmological constant problems, recently put into the more general context of the dark energy problem. In...

MOND is a theory the modifies the theory of gravity in weak fields which predicts, from luminous matter observations only, most of the galactic dynamics which motivated dark matter theory. It was developed by an Israeli scientist by the name of Milgrom in 1983. TeVeS is a relativistic...

Hello Marcus, selfAdjoint, nightcleaner, Chronos, setAI and others I think the following speaks for itself Viable exact model universe without dark energy from primordial inflation David L. Wiltshire http://www.arxiv.org/abs/gr-qc/0503099 Regards Kea :wink:

Or in other words, is dark energy the energy of dark matter? and vive versa. Please give reasons to your answers.

I was wondering what kinds of experiments we are doing to find out what DARK MATTER and DARK ENERGY is and where there being preformed

Brian Greene in "The Fabric of the Cosmos" gives the above three as indirect, universal fields in which we exist but have not yet directly detected. Could they be mathematically interlinked among themselves or with immediately observable phenomena?

"RE: Hubble's law is WHAT is driving the expansion: the not so recent Findings (last 10-5 yrs) is that experimentally it looks like there is a dark energy component." Question: At what point does Hubble's Law begin to suggest this dark energy component? Suzanne Elizabeth Seitz

http://xxx.lanl.gov/pdf/astro-ph/0309679 Mechanism for vanishing zero point energy Robert D klauber. Jan 2005. This paper is way beyond my ken, if anyone has an interest, will they please explain the basics.

http://arxiv.org/pdf/astro-ph/0501152 Is dark energy needed in a perturbed universe. I came across this letter and thought it may be of interest.

Relativity and the "Dark Energy" question I am an amateur and I am looking for help in answering the following question concretely - with numbers. Time passes more slowly in a gravity well. This we know. Regarding the expansion of the universe, and the increasing rate of expansion. If...

It's a very simple question i guess, what is dark energy? Is it like that proton and anti proton thing where the anti-proton contains dark energy or something like that? I read recently that they had found evidence of dark energy, what is it, what is the evidence, how did they find it and what...

Two new October papers. the first is notable because of the reputation of some of the authors. Sean Carroll and Michael Turner are among a handful of the most prominent mainstream cosmologists. here they are trying to see if one can avoid the need for dark energy by a modification of the...

what is dark energy? i heard that when i was watching a Tv programme about space.

Another one of the physics teacher working at the college I attended (see my previous post) wrote a book on basic http://universite.deboeck.com/Resources/Titles/28011100266200/Images/28011100266200L.gif . In this book it says that the expansion of the Universe is due to the expansion of space...

How does dark energy exert pressure - what does it push against.It must push against something solid if it has pressure units like Nm^-2?

https://www.physicsforums.com/showthread.php?p=288415#post288415 here's a straw in the wind. A good thing about Baez post is the intuition comes through---nuance, the changing barometer I think there is a hint here that he approves of people using the term "dark energy" because he sees a...

I'm reading Hawking's take on ground state energies never being zero, and he adds an interesting point. He said based on the casimir effect the denisty of ground state fluctuations (wavelengths) are less by a finite amount between the plates, causeing them to draw together. To me this explains...

Could anybody list (and write a few explanatory words about) the various theories which explain the origin of the dark matter and the dark energy? Thanks!

dark matter --- dark energy Can anyone explain to me the difference between dark matter and dark energy ? What are their proper relations to the expanding universe? Dark matter should be taken into account because we know not enough matter that can be held responsible for keeping...

It's interesting to note that if the universe expands to twice its current radius,then it will require 10^60 m^3 of space to be created per second, and so 10^60 x 10^-27kg of dark energy = 10^33kg of dark energy per second. This means that the mass of 1000 Suns must be created every second in...

dark energy + "missing" antimatter Did dark energy stop antimatter from being produced in the early universe and is this why there is not much antimatter around today?

If black holes create dark energy, then the tendency for dark energy to cause expansion of space in the black hole would be balanced by the tendency of gravity to pull the mass of the black hole to one point.So a singularity would not form.Since dark energy is a kind of energy, its energy must...

The question that follows assumes that there can be energy conservation in general relativity: Dark energy is said to have a uniform energy distribution in space.But how can the distribution be uniform if dark energy is created from some other energy source, and energy sources such as...

If Dark Matter was the mirror twin to Dark Energy, then normal matter would be siamese twins?

Do dark energy models explain anything about the expansionary phase after the Big Bang? Maybe matter wasn't formed well enough and gravity wasn't working too well, so dark energy was by a large margin, the dominant force? Also, can anyone give me a link to a timetable of the universe's...

Dark energy is space and its interaction with vacuum particles is space-time. Matter affects dark energy and vacuum particles to curve space-time. Anyone agree?

If I double the size of a classical,non-quantum mechanical vacuum, I double the volume of space and its density stays constant at zero kg/ m ^3.As the amount of dark energy in the universe increases the volume of space increases and the density stays constant.Is dark energy space?

If I take two spherical regions of space about one metre in radius, they would contain about 10 ^ - 27 kg of dark energy each. If I now say that the centres of these regions are one metre apart, and assume that there is rest mass associated with dark energy (this rest mass being uniformly...

Gluons are dark energy. They emit gravitons and these collide with photons and cause them to lose energy - as yet more gravitons - and redshift. As the photons travel through space they get longer wavelengths and gravitons of longer wavelength (emitted by gluons) collide with them so that...

Dark energy could be the energy of a huge number of gravitons. As photons traveling from one galaxy to another redshift they could emit gravitons that adds to the dark energy total and so keep the density of dark energy constant.Also if the gravitons carry the colour force , like gluons, then...

http://www.physicsweb.org/article/news/8/6/14 The latest findings, supposedly, refute the string theory approach, whereby the Dark Energy portion of the Universe is dynamical... or we don't have all the pieces in the puzzle yet?

http://arxiv.org/abs/gr-qc/0406056 Casimir Energy Density at Planck Time: Cosmic Coincidence or Double Solution to the Cosmological Dark Energy Problem? C. S. Unnikrishnan (Tata Institute, Mumbai) 5 pages "The Casimir energy density calculated for a spherical shell of radius equal...

What is the difference between a scalar field and a vector field? If I had a point mass with vectors pointing in all directions from its surface the field of the mass could be said to have a magnitude and direction in all directions.I could call this a scalar because it is different from a...

"Vacuum fluctuations and the Casimir effect are considered in a cosmological setting. It is suggested that the dark energy, which recent observations suggest makes up 73% of our universe, is vacuum energy due to a causal boundary effect at the cosmological horizon." A poster on SPR named...

Dark energy waves absorb energy from photons in intergalactic space and the total energy of dark energy increases, increasing the acceleration of the universe. Because the dark energy is quantised when it absorbs energy from a photon it changes to a higher energy quantum state.If a cosmic...

Dark energy has a constant density as the universe expands. Doesn't this suggest that the baryonic mass of the universe is expanding in a substance of constant volume and density that occupies a volume far larger than the universe itself currently occupies?

If this 'Dark Energy' is actually 'energy', how would we go about tapping into it and convert it to something we can use? (or at least see it work)

The whole business of dark energy or cosmological constant or quintessence is novel, unfamiliar, and nebulous. Different models or mechanisms have been offered to explain apparent acceleration in expansion of U during past one-to-four billion years. If you go back more than four or five billion...

http://www.astronomy.com/Content/Dynamic/Articles/000/000/001/604djcxv.asp XMM-Newton studies the X-ray universe from Earth orbit. ESA A mystery that has been haunting the fields of physics and cosmology has just grown deeper. Dark energy, that stealthy ghost that lurks in the...

http://arxiv.org./abs/gr-qc/0402066 these people (at U British Columbia) study an idea for observing the effect of the cosmological constant (dark energy, negative pressure...) on the spectrum of Xrays coming from a black hole their conclusion is disappointing, the test they study...

http://www.universetoday.com/am/publish/dark_energy_doubts.html ESA's X-ray observatory, XMM-Newton, has returned tantalising new data about the nature of the Universe. In a survey of distant clusters of galaxies, XMM-Newton has found puzzling differences between today's clusters of galaxies...

this was a new post today http://arxiv.org/astro-ph/0401244 it is still just a germinal idea remember in 1998 type IA supernovae were used as a standard candle and the luminosity-distances of them at various redshifts pointed to the existence of dark energy or cosmological constant...

http://arxiv.org/astro-ph/0309800 A group at University of Washington, Fardon et al just posted "Dark Energy from Mass-Varying Neutrinos" which does not seem to me as far-fetched as other speculation I've seen about cause of DE they seem to think that some element of their idea is...

http://news.bbc.co.uk/2/hi/science/nature/3155200.stm

what is dark energy? i think that when dark energy was discovered science didnt know how profound the discovery was. i think that dark energy is the primal source of everything, i imagine an instability in the dark energy built to such an extent that it could no longer be contained, this...

Properties of "Dark Energy" ? Has their been any progress in discovering what properties this Dark Energy might have?

Well, apparently we have now found new and more direct evidence for the existence of the so called 'dark energy.' I find it quite remarkable. http://www.space.com/scienceastronomy/dark_energy_030805.html

What's dark energy? It's important to know what is the most common type of energy of the universe

I was just reading a 1995 paper by Lee Smolin arXiv:gr-qc/9505028 "Linking topological quantum field theory and non-perturbative quantum gravity" not such a catchy title, but contains some surprising things We all know the story about how Einstein put Lambda (cosmological constant) in...