Exploring the X-ray Universe: XMM-Newton Studies Dark Energy

In summary, there is a growing mystery surrounding the presence of dark energy in the universe, with evidence suggesting that it makes up 73% of the universe's composition. However, recent X-ray surveys of distant galaxy clusters have challenged this theory, proposing that there may be a larger amount of dark matter present. This theory, put forth by Alain Blanchard, suggests that the Hubble parameter may be lower than previously thought, leading to a higher density of matter in the universe. While this idea is not widely accepted, it highlights the need for continued research and a willingness to consider alternative explanations in the scientific community.
  • #141
phantom bounce

http://arxiv.org/abs/astro-ph/0405353
"The Phantom Bounce: A New Oscillating Cosmology"



-----------------------------------------------------------
Perhaps is time to give a bit of attention to another model of dark energy, the Generalized Chaplygin gas. This model was proposed in this paper

http://arxiv.org/abs/gr-qc/0202064

"Generalized Chaplygin Gas, Accelerated Expansion and Dark Energy-Matter Unification"
Authors: M. C. Bento, O. Bertolami, A. A. Sen


and is a generalization of the Chaplygin gas model of dark energy, proposed some time before by other people
 
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Astronomy news on Phys.org
  • #142
"The phantom bounce" was very interesting reading. I didn't know that oscillating universe theories were constrained by Hawking's idea that black holes would grow
as large as the horizon and make the cosmological equations invalid.The paper
says that dark energy needs to tear the black holes apart before a bounce occurs for the equations to be useful.In a particular case the author says that the energy density of dark energy can be inversely proportional to the energy density of radiation.
This would be the case if the dark energy was absorbing energy from the radiation.
Is the cosmic microwave background redshifted because dark energy absorbs energy from photons? If Dark energy absorbs photon energy and undergoes a phase change it would be analagous to what water vapour is to ice and water -Give dark energy some input energy and it "evaporates" and yields a higher "vapour pressure."
If the photons and dark energy are exchanging quanta of energy this would mean
electromagnetic theory needs revising and also we would be able to introduce quantum mechanics into the friedman equations.
One of the arguments against tired light theories of redshift is that
there would be blurring because of the change in momentum of photons
interacting with other particles.But dark energy is unusual, perhaps there would be no blurring involved.And what's more explaining redshift with dark energy means the universe is still expanding and so the microwave background is the afterglow of a Big Bang.
 
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  • #143
Does dark energy absorb energy from photons and cause them to redshift?
Someone told me that the redshift would probably be higher than is experimentally observed if this idea was right, but they didn't give details of why. Can someone tell me why the redshift would be higher? And if dark energy isn't uniformly distributed at every point in space - if it was distributed like a uniform volume of atoms- could that reduce the redshift back to the experimentally observed redshift?
Can dark energy consist of individual quantized particle pairs of
some kind?
Apparently quintessence models have difficulty producing the supposed
flatness of the dark energy distribution in a natural way.There is a
paper on the arxiv that models dark energy as phenomenon with three mutually orthogonal Vectors to guarantee isotropy.Is dark energy a
vector phenomenon?
If dark energy absorbs energy from photons and expands it would keep its density constant - in other words, can dark energy be space-time?
 
  • #144
If dark energy absorbs energy from photons and expands it would keep its density constant - in other words, can dark energy be space-time?
-----------------------------------------------------------------------
photon energy reduces as space expands also photon density,
but i think photon numbers stay constant, i think your suggestion
is close to the tired light theory which has not found favor.
I'm not even sure if total photonic energy is sufficient to power
accelerated expansion, maybe METEOR has some ideas?
 
  • #145
Wolram have you seen
www.cosmologystatement.org[/URL]
it seems that a number of academic folk (some
emeritus) and technically trained brethren
have decided to rain on the dark energy parade
but I have not checked, just saw this

doesnt mean BB is wrong and they are right, just healthy skepticism
on their part, I suppose.
you tend to maintain a skeptical attitude, even while
getting into the details, so this should not seem all that different

I don't like their statement myself, but there it is
published 22 May in New Scientist
 
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  • #146
photon energy reduces as space expands also photon density,
but i think photon numbers stay constant, i think your suggestion
is close to the tired light theory which has not found favor.
I'm not even sure if total photonic energy is sufficient to power
accelerated expansion, maybe METEOR has some ideas?


Tired light arguments don't apply.The dark energy might not have momentum to cause blurring of photons and time dilation would be fine too because the universe is still expanding but the redshift is caused by space-time (dark energy?) absorbing energy from photons.
If rest masses are also supplying energy to dark energy then they might make up the shortage.We could all be evaporating slowly!

As for the cosmology statement: alternative theories to the big bang hypothesis should get funding.When any scientific investigation is done
it usually yields posititve or negative results that help scientists decide what the right answer is.
 
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  • #147
Thanks MARCUS, several learned people giving ms science an itch, i can
only say---------
Good old Halton Arp," I am unsure about others," he keeps banging his drum, maybe some will start to like his music, i think he should not be dismissed
as he has some valid reasons for disputing m/stream science, if i were a scientist i would sign his paper, for no other reason than opening the debate.

KURIOUS seems i misunderstood you how could your theory
be tested?
 
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  • #148
the fluctuations are required by quantum physics. nothing, including consciousness, can remain fixed. universal expansion requires exansion on all levels, including the spectators
 
  • #149
how could your theory
be tested?

--------------------------------------------------------------------------------
Need to know accurately the acceleration rate of the expansion of the universe and the change in that rate.
Then the amount of mass/energy turning into dark energy could be deduced.
If a planet is losing mass/energy to space-time/dark energy then the radius of its orbit
would change slightly.Perhaps a gyroscope would spin more slowly or the magnetic moment of an electron which is known to 11 decimal places might change.But any measurement of the acceleration rate of the expansion of the universe has a high
degree of uncertainty in it.Maybe the way a photon redshifts in the Earth's atmosphere
could help out.
 
  • #150
KURIOUS, i do like your theory, if anything it is more tangible
than some and seems to have a nice intuitive feel to it, maybe
someone will come along and poke holes in it, but i think it is
a theory worth pursuing.
 
  • #151
This would be the case if the dark energy was absorbing energy from the radiation.
Is the cosmic microwave background redshifted because dark energy absorbs energy from photons?

This idea was first proposed by marcus in this thread
https://www.physicsforums.com/showthread.php?t=2220

It would be interesting to clear up some things.
According to the persons that defend that dark energy is a cosmological constant, it means that is due to fluctuations of the electromagnetic field. That is to the emergence of virtual photons that rapidly annihilate and disappear. I have never heard that dark energy can be due to fluctuations of other fields, like the gravitational field, the Dirac field, the gluon field or others. Why?
I can imagine like those virtual photons emerge in spacetime and each of them carry negative pressure, so they make spacetime to expand.
It's like you have a cake, and them, POP!, some virtual raisins appear in it, and the cake expands.
It makes me wonder about two different existent theories about the nature of spacetime: substantivalism and relationalism. In short, the first defends the physical existence of spacetime, but the second denies its physical existence.
Rovelli's book (you can find it for free in his web) talks about it in chapter 2. Rovelli is clearly a relationalist, he DENIES the physical existence of spacetime. It has me confused, I tend to be more of a substantivalist. He explains about the "hole argument", taht got confused Einstein about if the field equations should or not be generally covariant. The hole argument gives two alternatives:
a)the field equations cannot be generally covariant
b)there's no meaning to talk about some given physical spacetime point
At the end, the equations of Einstein were generally covariant. SO it must follow that spacetime don't exist. But, I , wonder, how can spacetime stretch the wavelength of the photons of the CMB as it expands then? how can then exist then gravitational waves, ripples of spacetime? how can then exist phenomena like frame dragging, the dragging of spacetime around a massive body as it rotates? I hope that someone can give some ideas
 
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  • #152
METEOR

I have never heard that dark energy can be due to fluctuations of other fields, like the gravitational field, the Dirac field, the gluon field or others. Why?

Probably because the electromagnetic field is the one that's best understood.
People stick with what they know in detail.

how can spacetime stretch the wavelength of the photons of the CMB as it expands then? how can then exist then gravitational waves, ripples of spacetime? how can then exist phenomena like frame dragging, the dragging of spacetime around a massive body as it rotates? I hope that someone can give some ideas

The rubber sheet analogy people often use for spacetime may be more
realistic than is currently thought.What if spacetime is a substance - like the ghost condensate Nima Arkani Hamed is working on at Harvard
http://arxiv.org/PS_cache/hep-th/pdf/0312/0312099.pdf
Then the Earth rotating could be dragging something which physically sticks to it and distorting that something.Gravitational waves could be like sound waves moving through a medium.


If spacetime doesn't exist...

Relativity makes all the right predictions but spacetime is a counterintuitive
idea. People argue that quantum mechanics which makes counterintuitive real predictions has been misinterpreted by the Copenhagen school, perhaps relativity has been misinterpreted too - perhaps spacetime doesn't exist.
The struggle to find a quantum theory of gravity suggests something is wrong.

I should add that the expansion of the universe and increase in dark energy does not have to relate directly to the photon redshift. What if photons have more energy than we think they do and this energy gets released in a similar way that rest mass releases energy in an atom bomb.So if a photon redshifts by a certain number of kg (E= mc^2), perhaps that
number of kg is analagous to rest mass and can split into many units of light which have a more effective energy - a kind of phase change.Photons will be evaporating and turning into dark energy - so no need to invoke a dark energy that absorbs photon energy.It was mentioned on the previous thread Marcus started in 2003 that the amount of cmbr energy would only be 1/10 of what is required to account for dark energy.But what if E = 10 m c^2 and it takes a long time for the other 9 mc^2 to appear.It will be hard to poke holes in the theory because dark energy is unusual.The challenge is to try and reduce it to more familiar physics - if it exists in the real world then it must be reconciled with the real world.
I noticed on the thread started in 2003 that there was mention of moving the thread to theory development.But dark energy discussions have to be highly speculative because little is known about it and whatever it is, it
is likely to be unusual- unless someone comes up with a dramatically improved idea of what vacuum energy is.
 
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  • #153
This idea was first proposed by marcus in this thread
https://www.physicsforums.com/showthread.php?t=2220
------------------------------------------------------------------------
Well without knowing the source i find myself agreeing with
MARCUS i always knew he knew what he was talking about.
 
  • #154
It's worth to mention that the paper about the phantom bounce says that in the model of phantom energy, the density of energy of dark energy becomes infinite in finite time. This seems totally wacky
 
  • #155
wolram said:
This idea was first proposed by marcus in this thread
https://www.physicsforums.com/showthread.php?t=2220
------------------------------------------------------------------------
Well without knowing the source i find myself agreeing with
MARCUS...

heh heh

the M :surprise:RC :biggrin: S conjecture

well maybe
 
  • #156
Marcus
Well in archeology two stones together is a wall, two stones together
with a shard of roman pottery is a roman wall.
 
  • #157
by KURIOUS

It will be hard to poke holes in the theory because dark energy is unusual.The challenge is to try and reduce it to more familiar physics - if it exists in the real world then it must be reconciled with the real world.
----------------------------------------------------------------------
I second that, if dark energy is "the power" in the universe then
nothing can be fully understood without knowing what it is, it
maybe that dark energy is the normal universe stuff, and baryonic
things are the anomaly.
 
  • #158
http://www.cnn.com/2004/TECH/space/05/18/dark.energy/

CNN) -- The Chandra Space Telescope has gathered further evidence the universe is expanding at an accelerating rate, scientists at NASA and Britain's Institute of Astronomy announced Tuesday. The finding sheds new light on a force known as "dark energy."
 
  • #159
http://xxx.arxiv.cornell.edu/abs/astro-ph/0404601

We discuss the possibility that the existence of dark energy may be due to the presence of a spin zero field $\phi(x)$, either elementary or composite. In the presence of other matter field, the transformation $\phi(x)\to \phi(x) +$ constant can generate a negative pressure, like the cosmological constant. In this picture, our universe can be thought as a very large bag, similar to the much smaller MIT bag model for a single nucleon.
 
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  • #160
http://arxiv.org/abs/astro-ph/0405430
This paper discuss the possibility that dark energy is composed of decaying vacuum energy. Explicitly, vacuum energy that decays in cold dark matter. That's no great? You solve two problems in the same paper. You explain what's dark energy and explain where dark matter come from. But how can the density of vacuum energy stay constant if it's decaying? Something says me that this is not the correct model
 
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  • #161
Chandra is saying that dark energy looks to be constant in density still.
The paper on a spin 0 field seems to suggest that mass can be attributed to this field but then the Higgs field is spin zero too so that would be logical.Stephen Hawking doesn't think that a spin zero Higgs field will be found
and apparently upset Peter Higgs a few years ago when he heard he'd said this!
If dark energy is made from decaying vacuum energy then is that why the vacuum energy is only about 10^-9 J/m^3 instead of 10^120?
 
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  • #162
Hawkings, what has he contributed?
 
  • #163
wolram said:
http://xxx.arxiv.cornell.edu/abs/astro-ph/0404601

We discuss the possibility that the existence of dark energy may be due to the presence of a spin zero field $\phi(x)$, either elementary or composite. In the presence of other matter field, the transformation $\phi(x)\to \phi(x) +$ constant can generate a negative pressure, like the cosmological constant. In this picture, our universe can be thought as a very large bag, similar to the much smaller MIT bag model for a single nucleon.


This from three weeks ago:https://www.physicsforums.com/showthread.php?t=24176

Contains the Authors work?
 
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  • #164
http://arxiv.org/abs/astro-ph/0405596

"Acceleressence: Dark Energy from a Phase Transition at the Seesaw Scale"

In this model called acceleressence (seems some kind of gluing of the words acceleration and quintessence), the acceleration of the universe is related to a phase transition, and dark energy is identified with a scalar field called acceleron. I can't say much more given that, for example, I don't have a clue about what's the seesaw scale
 
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  • #165
meteor said:
http://arxiv.org/abs/astro-ph/0405596

"Acceleressence: Dark Energy from a Phase Transition at the Seesaw Scale"

In this model called acceleressence (seems some kind of gluing of the words acceleration and quintessence), the acceleration of the universe is related to a phase transition, and dark energy is identified with a scalar field called acceleron. I can't say much more given that, for example, I don't have a clue about what's the seesaw scale

Im going to give this a wide berth, but only because of the terminology used!

Just kidding, I believe the paper is referring to the 'post-phase' being Seesaw, a transitional moment where the Universe transfers from one Phase to another, for example from an Expansive mode to a Contracting Mode, the Contracting mode can be derived from the Expansion Mode just as a Deceleration evolves from an Acceleration by the factor of relationary Speed.

The interesting thing to be asked is if this deceleration is prior or post to a Bounce in some Expryotic modeling.
 
  • #166
DARK ENERGY and the AHARANOV BOHM effect.

In the Aharanov -Bohm effect, a magnetic field isolated inside a solenoid,
changes the phase of an electron interference pattern.The magnetic field does not exert a force on the electrons - it has been shown that the electromagnetic
vector potential can account for the phase shift.But is it possible to explain the Aharanov-Bohm effect in another way?
I think the answer to this question is yes and can be given by the force the magnetic field of the solenoid exerts on dark energy particles passing through the solenoid and into the "isolated" magnetic field. If the dark energy particles carry an electric charge they will be deflected by the magnetic field into the path of electrons passing through the slits in the interference experiment and will exert a force on the electrons which will change their trajectories slightly and change the phase of the interference pattern.

Let’s assume the dark energy particles are moving at close to the speed of light – 10^8 m / s . The magnetic field strength of the solenoids used in experiments of this kind are typically abouts 1 Tesla,the superconducting solenoid is about 10^ - 2 metres wide, and so a dark energy particle moving at about 10^8 m / s would take about
10^ - 10 seconds to pass through the solenoid.

The force exerted by the magnetic field in the solenoid on the dark energy particles is:

Force = q v B
Force = q x 10 ^ 8 x 1
Force = 10 ^ 8 q

A maximum force of 10 ^ 8 q is transferred to an electron by the dark energy particle.

The acceleration of the electron is given by Force / mass of electron

This is 10 ^ 8 q / 10 ^ -31 m / s ^ 2 = 10 ^ 39 q metres / s ^ 2

But the force only acts for 10 ^ - 9 seconds ( the time the electron takes to cross the path of the solenoid and the region in which the dark energy particles are interacting with the magnetic field of the solenoid – assuming the electron has a speed close to 10 ^ 7 m / s ) so after this time the electron could have a maximum speed displacing it from its main direction of motion of
10^ 39 q x 10 ^ -9 m / s = 10 ^ 30 q m / s.

In the time the electron takes to cross the path of the solenoid and the region in which the dark energy particles are interacting with the magnetic field of the solenoid,
the electron will be displaced a maximum of 10 ^ 30 q x 10 ^ -9 = 10 ^ 21 q metres.

It is known from experiment that the interference pattern shows a phase shift of
10 ^ -6 metres.
Therefore 10 ^ 21 q = 10 ^ -6
But there is more than one dark energy particle so if N is the total number of dark energy particles acting on the electron over a distance of 10 ^ -2 metres then

10 ^ 21 q x N = 10 ^ -6
The minimum uncertainty in energy of a dark energy particle is given by the maximum time over which it could change its energy state ( assuming dark energy particles can change their energy state).This maximum time is given by the age of the universe which is 10 ^ 18 seconds.

using E x t = h bar

E x 10 ^ 18 = 10 ^ - 34
E = 10 ^ -52 joules

Since a dark energy particle must have at least this energy then this means
the minimum rest mass associated with a dark energy particle is ( by E = m c^ 2 )
10 ^ -69 kg.
If we assume that dark energy particles have the same charge / mass ratio as a proton
( they have approximately the same mass density per cubic metre – about 10 ^ -27 kg / m ^ 3) then they have an electric charge of 10 ^ -61 Coulombs.

Using 10 ^ 21 q x N = 10 ^ -6 and q = 10 ^ -61

we get N the number of dark energy particles in 10 ^ -6 m ^ 3
( the width of the solenoid cubed) is 10 ^ 34

So in one cubic metre there would be 10 ^ 34 x 10 ^ 6 = 10 ^ 40 dark energy particles.

Earlier on I said the mass of a dark energy particles was 10 ^ - 69 kg.

In one cubic metre this amounts to a mass of 10 ^ 40 x 10 ^ -69 =10 ^ - 29 kg.

About one hundreth of the mass of a proton.
 
  • #168

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