Space Expansion and Darkness

[AbstractDreamer]

How does quantum mechanics explain or describe observations that space is expanding?

 

If qm cannot describe such phenomenon, is there any other model that can?

 

How does dark energy and dark matter fit into the qm approach.

 

Which of following terms is most likely to exist assuming some unexplained behaviour is observed: Dark Time, Dark Mass, Dark Speed, Dark Spin, Dark Momentum, Dark Field, Dark Direction, Dark Gravity, Dark Observer.

 

Where would unexplained behaviour most likely be observed?

[Klaynos]

How does quantum mechanics explain or describe observations that space is expanding?

 

This is outside the domain over which QM is a good model so it says nothing about this.

 

If qm cannot describe such phenomenon, is there any other model that can?

The lambda CDN model. Which is a parameterisation of the big bang model.

 

How does dark energy and dark matter fit into the qm approach.

They don't at the moment. Dark matter will probably turn out to be some kind of wimp in the standard model. Which will be consistent with QM. Who knows about dark energy.

 

Which of following terms is most likely to exist assuming some unexplained behaviour is observed: Dark Time, Dark Mass, Dark Speed, Dark Spin, Dark Momentum, Dark Field, Dark Direction, Dark Gravity, Dark Observer.

Who knows. The term dark matter and dark energy were first coined because we know little about them, like the dark ages. With dark matter it also doesn't interact strongly with em radiation so will quite probably always be known as dark.

 

Where would unexplained behaviour most likely be observed?

On the edges of what we already know and have measured.

[Strange]

Great answer. Nothing to add really, except that a future theory of quantum gravity might tells us more about the early history of the universe, the nature of dark energy and dark matter.

[AbstractDreamer]

Very good answers.

 

Arbitrary parameterisation. Pick some numbers till it fits? Hmm.

 

Observed space expansion? Lets make up some Dark Energy

Observed gravitational anomalies? Lets make up some Dark Matter

 

Do we have a model of DM that explains all the gravitational anomalies, or are some anomalies more different that others?

 

If the nature of DM and DE is unknown, why do we need to separate the two concepts. Could they be part of a greater underlying Dark Thing that exhibits behaviour of both DE and DM? Isn't the goal of physics to simplify the model? Is there anything to tell us they must be different?

 

Or could there be more types of fundamental Darkness?

 

What other observations do no fit into the QM model at present?

 

How might QM explain DE?

[swansont]

Very good answers.

 

Arbitrary parameterisation. Pick some numbers till it fits? Hmm.

 

Observed space expansion? Lets make up some Dark Energy

Observed gravitational anomalies? Lets make up some Dark Matter

 

 

 

!

Moderator Note

 

Either you know enough about the science to give a better response, or you don't in which case your critique is ill-informed.

 

It looks like trolling and smells like trolling. You've got one more chance to show that it's not trolling. Because right now this has all the flavor of someone with an agenda, just looking to stir the pot. If your participation is sincere, do a better job of asking questions without characterizing science as some sort of ruse.

 

Do not waste your chance responding to this modnote in the thread.

[Strange]

Observed space expansion? Lets make up some Dark Energy

 

 

Wrong. Expansion does not require dark energy.

 

However, the rate of expansion is seen to accelerate. This needs to be explained. We do not know what the explanation is so we call it "dark energy".

 

 

 

Observed gravitational anomalies? Lets make up some Dark Matter

 

What should we do? Ignore them?

 

 

 

Do we have a model of DM that explains all the gravitational anomalies, or are some anomalies more different that others?

 

Dark matter appears to fit all the evidence. Attempts at modified gravity theories can work for galaxies but not galaxy clusters, so still seem to need some dark matter.

 

 

 

If the nature of DM and DE is unknown, why do we need to separate the two concepts. Could they be part of a greater underlying Dark Thing that exhibits behaviour of both DE and DM? Isn't the goal of physics to simplify the model? Is there anything to tell us they must be different?

 

They do completely different things. You might as well ask if photosynthesis and earthquakes are caused by the same thing.

 

(I have seen a couple of pretty speculative attempts to unify them, but it is not clear they will get anywhere.)

 

 

 

Or could there be more types of fundamental Darkness?

 

As the "dark" name is just used to indicate something we don't understand, I'm sure there are or will be other unknown things that get a similar label.

 

 

What other observations do no fit into the QM model at present?

 

The problem is that there isn't any clear evidence that doesn't fit the current model. So there are few good directions for new physics to go.

 

 

How might QM explain DE?

 

If dark matter is actually matter, then it will be a new form of matter that and so QM will need to be extended.

[Mordred]

I should note that there is an entire field of Quantum mechanics that describes expansion.

 

That field is LQC. loop quantum gravity.

 

So yes it is possible to show expansion using action under QM.

How does quantum mechanics explain or describe observations that space is expanding?

 

 

see above LQC can also model the influence of dark matter and dark energy. Even if it can't identify the cause of the two we can model their influence upon expansion.

 

A little side note it decades of research for both dark energy and dark matter to be accepted under LCDM. There was so many variations and counter arguments that one could fill a library on alternative ideas.

 

PS I should also include quantum geometrodynamics on the list above.

 

 

Some information on how expansion is modelled via its particle contributors might be order.

Every particle SM model, the cosmological constant aka dark energy and dark matter. Is assigned an equation of state.

Every particle has a temperature and pressure influence. These influences can be calculated using the particles quantum numbers such as spin, charge etc using the Fermi-Dirac and Bose-Einstein statistics which employ the Boltzmann constant.

 

The quantum numbers and interactions such as entropy density determine the amount of influence upon temperature and pressure. You often hear the term used "degrees of freedom" Which correlates the above.

 

The equations of state are then applied to the fluid equations in both the EFE and FLRW metric. In a sense pressure performs the work for expansion but as there isn't a pressure gradient does not cause expansion.

 

Expansion occurs when the particles kinetic energy overcomes the particles self gravity. One might argue there is no walls for pressure to occur but under adiabatic expansion walls are not a requirement.

 

here is the EoS.

https://en.m.wikipedia.org/wiki/Equation_of_state_(cosmology)

 

You can find the above better described in these two articles.

 

http://arxiv.org/pdf/hep-th/0503203.pdf "Particle Physics and Inflationary Cosmology" by Andrei Linde

http://www.wiese.itp.unibe.ch/lectures/universe.pdf:" Particle Physics of the Early universe" by Uwe-Jens Wiese Thermodynamics, Big bang Nucleosynthesis

Edited November 16, 2016 by Mordred

[Strange]

Which of following terms is most likely to exist assuming some unexplained behaviour is observed: Dark Time, Dark Mass, Dark Speed, Dark Spin, Dark Momentum, Dark Field, Dark Direction, Dark Gravity, Dark Observer.

 

 

The term "dark flow" was coined for a possible anomalous velocity of galaxy clusters.

[Mordred]

As I mentioned equations of state...

here is another workup I did on another thread. Its an easier heuristic view than those articles but will help in understanding them

 

[latex]DU=pdV[/latex].

 

First take the first law of thermodynamics.

[latex]dU=dW=dQ[/latex]

U is internal energy W =work.

As we dont need heat transfer Q we write this as [latex]DW=Fdr=pdV[/latex]

Which leads to [latex]dU=-pdV.[/latex]. Which is the first law of thermodynamics for an ideal gas.

[latex]U=\rho V[/latex]

[latex]\dot{U}=\dot{\rho}V+{\rho}\dot{V}=-p\dot{V}[/latex]

[latex]V\propto r^3[/latex]

[latex]\frac{\dot{V}}{V}=3\frac{\dot{r}}{r}[/latex]

Which leads to

[latex]\dot{\rho}=-3(\rho+p)\frac{\dot{r}}{r}[/latex]

We will use the last formula for both radiation and matter.

Assuming density of matter

[latex]\rho=\frac{M}{\frac{4}{3}\pi r^3}[/latex]

[latex]\rho=\frac{dp}{dr}\dot{r}=-3\rho \frac{\dot{r}}{r}[/latex]

Using the above equation the pressure due to matter gives an Eos of Pressure=0. Which makes sense as matter doesn't exert a lot of kinetic energy/momentum.

For radiation we will need some further formulas. Visualize a wavelength as a vibration on a string.

[latex]L=\frac{N\lambda}{2}[/latex]

As we're dealing with relativistic particles

[latex]c=f\lambda=f\frac{2L}{N}[/latex]

substitute [latex]f=\frac{n}{2L}c[/latex] into Plancks formula

[latex]U=\hbar w=hf[/latex]

[latex]U=\frac{Nhc}{2}\frac{1}{L}\propto V^{-\frac{1}{3}}[/latex]

Using

[latex]dU=-pdV[/latex]

using

[latex]p=-\frac{dU}{dV}=\frac{1}{3}\frac{U}{V}[/latex]

As well as

[latex]\rho=\frac{U}{V}[/latex]

leads to

[latex]p=1/3\rho[/latex] for ultra relativistic radiation.

Those are examples of how the first law of thermodynamics fit within the equations of state. There is more intensive formulas involved. In particular the Bose-Einstein statistics and Fermi-Dirac statistics

What the above correlates to is particle degrees of freedom.

 

One can calculate how much influence any particle with known properties influence the temperature... pressure... expansion relations. Provided one knows the correct correlations to the Einstein field equations

[AbstractDreamer]

EoS link is gone. Can you link the other thread of yours?

Edited November 18, 2016 by AbstractDreamer

[Mordred]

EoS link is gone. Can you link the other thread of yours?

Not easily lol I've posted that example numerous times. ( its a handy time saver) However I can fix you up with something better.

 

First lets relink the EoS link to the wiki article. In case you have problems a google search " Equations of state Cosmology" will pull up the correct link. Don't forget to add cosmology or you will get classical mechanics lol.

 

https://en.m.wikipedia.org/wiki/Equation_of_state_(cosmology)

 

Here is a lecture note calculating the three main EoS. though it doesn't detail the scalar field EoS.

 

http://www.google.ca/url?q=http://eagle.phys.utk.edu/guidry/astro421/lectures/lecture490_ch19.pdf&sa=U&ved=0ahUKEwjV3tGYtrHQAhUMyWMKHeAiCW84FBAWCB4wBA&usg=AFQjCNESxFBeqzW7M7nh-oLqj62DyUUq6A

 

Seems to be links I post from my laptop as opposed to my phone that causes grief though I'm not sure why that is.

Edited November 18, 2016 by Mordred

[AbstractDreamer]

It's the end bracket that is dropped from the hyperlink. Sorry I had a lot of tabs opened and just saw a null wiki link.

There two papers are really fabulous.

[Mordred]

understood I'm glad your enjoying the papers. Nice to get feedback on them. If you want more decent ones on a given subject feel free to ask. I have a database of articles I often use.

Edited November 18, 2016 by Mordred

[AbstractDreamer]

My holidays are over. I'd have to admit I wasn't prepared for my curiosity to lead me down this rabbit hole. I have more than enough outstanding issues at the moment to get my head around. Plenty of ideas to fuel my dreams. Too much fuel might lead to singular collapse!

[Mordred]

lol no problem It is a lot to take in at once. You might note my signature has a link to further articles. Also the lightcone calculator is incredibly flexible.

 

A proper study of those two textbooks should take several months though lol

Edited November 18, 2016 by Mordred