Cold Runny Matter

some cosmology tainted with a macroeconomics sneeze or two

Originally published here as “Variations of Cosmic Grey”, on 2024-11-22.

Is Dark Energy (the vacuum energy density) white or black or grey? You can see right through it, but it emits no photons. So it is transparent? It also gravitates (or anti-gravitates, depending on your model & data) so should bend light. Being almost completely isotropic and homogeneous the light bending of the vacuum is pure quantum fuzz, so virtually undetectable.

I think I am coming around to “Grey Energy”. As I become a geriatric senior that’ll be my story. Not as sexy as Dark. So for now… it is still Dark, especially as I am still deep into my Radiohead era, and see no exit therefrom.

It’s the Data Stupid

Don’t get me started on The Economy.

Jokes aside. Big news out November 2024, the DESI survey analysis reveals:

• Einstein’s GR is good.

• The cosmological constant might not be constant, and might be tending to zero.

The statistics are still sketchy, and you have to take a few grains of salt since astronomy is rife with unknown systematic errors. But these results got onto the arXiv, so are “valid as things in the arXiv”. lol. Seriously though, just check out the list of authors. This is Big Science.

Going with such validity… I should make a few comments from a T4G theoretical perspective.

This webinar here was pretty good:

Cosmological Constant-ish

I don’t really like this result. GR based cosmology is a lot more sensible if Λ is constant and small and positive. However…

If Λ→0 then that is good for T4G because I am aligning or allying with a CPT-Symmetric Universe (Turok & Boyle). I would love to know Turok’s opinion on the DESI results. But from what I can tell it is the completely other hex #000000 story — of Dark Matter that is more critical for CPT-SU.

Having noted that, CPT-SU suggests dark energy is the spacetime vacuum symmetry, and that should be — according to CPT-SU —- governed by the 36 dimension=0 Bogoliubov scalars. I would not know how they are supposed to vary because they are symmetries, not particles.

On yet another hand, my personal bias is towards only a small positive Λ. If for some reason it varies in time then that’s fascinating and worth looking into. What sort of order effect is it? Is it GR or is it more QM?

My bet would be it is in the QM sector of gravity (the non-classical sector). Maybe the vacuum wormhole gas has something to do with the variation? I really have no good hypothesis. By goodness, some T4G theorist should look into it.

Astronomy Background

The main focus of DESI galaxy surveys is the baryon acoustic oscillation (BAO). Obviously that is a very sensitive test of gravity theories on large scales. The good news (for T4G) is that GR is more strongly validated. Still our best theory of gravity yo!

Here are some technical words I strung together…

The Baryon Acoustic Oscillations (BAO) in the DESI galaxy surveys refer to a pattern of matter density fluctuations in the large-scale structure of the universe. These oscillations originated from sound waves in the early universe and left an imprint as a characteristic scale in the distribution of galaxies.

BAO measurements from DESI are crucial for studying dark energy and its effects on cosmic expansion. They help to narrow the range of possible Dark Energy (vacuum energy) theories.

Key aspects of BAO in DESI surveys include:

1. Cosmic Ruler: BAO serves as a “standard ruler” for measuring cosmic distances. By analyzing the apparent size of these oscillations at different redshifts, researchers can determine distances to galaxies and map the expansion history of the universe.

2. DESI’s BAO measurements provide highly precise data on the universe’s expansion rate at different cosmic times. The 2024 DESI results achieved a combined precision of ~0.52% across six redshift bins, surpassing previous measurements.

3. Redshift Range: DESI measures BAO using various tracers (galaxies and quasars) over a wide redshift range from 0.1 to 2.1, allowing for a comprehensive view of cosmic expansion history.

4. For analysis DESI employs advanced techniques like blinded analysis and improved BAO fitting and reconstruction methods to enhance the accuracy and reliability of results.

If that all makes me look knowledgeable I have to disabuse you of that notion. I only read a few abstracts, since observational astronomy is not of much interest to me personally. Obviously it is of enormous interest to me generally! Like watching the All Blacks versus playing for the All Blacks.

Is Λ really Λ?

The 2024 DESI data does not definitively refute the hypothesis of a constant vacuum energy (cosmological constant), but it does provide some evidence that slightly favours a dynamical dark energy model. Whatever that means! How does the vacuum energy of spacetime itself vary dynamically? I do not think any one knows.

You might think the Causal Sets modellers probably would say they can predict a dynamical Λ. I would highly doubt the veracity of such claims, since anyone can dream up a way to make the vacuum dynamical. The problem is Causal Sets is not yet a well-tested theory. You do not throw out the baby of GR with the bathwater of the cosmological constant. What you do is wait until Turok & Boyle have some idea of whether the dimension=0 Bogoliubov scalars explain a time varying effect Λ.

My suspicion is that the vacuum energy density is constant, but the galaxy survey data are picking up dynamical effects of the cosmic expansion that impart a time-varying Λ shadow. Just what I mean by “shadow” is something I have no clue about, that’s why I use a non-technical poetic term.

Also, there is still a possibility within data uncertainty that the ‘cosmological constant’ is indeed constant.

1. DESI’s year-one BAO measurements are compatible with a cosmological constant, but they slightly favor a model suggesting dark energy is evolving or “dynamical” .

2. The evidence for evolving dark energy is not yet strong enough to claim a discovery. The observations favor the erosion of dark energy with a middling statistical significance that could vanish with additional data .

3. When combining DESI BAO data with CMB data, there is a statistical preference for a dark energy model with a time-varying equation of state (EOS) compared to the standard ΛCDM model.

4. Assuming a constant EOS, DESI BAO results are fully compatible with a cosmological constant, with w0=−0.997±0.025 (2.5% uncertainty) when combined with CMB and Pantheon+ data.

5. However, when considering a varying EOS, the combined DESI and CMB data show a 2.6σ deviation from a cosmological constant, with w0​=−0.45 (−0.21,+0.34) and wa=−1.79 (−1.00,+0.48).

6. Researchers have stressed that more data is needed to confirm or refute these findings. The next batch of DESI data is expected to be released in late 2025, which may provide more clarity on the Λ=Λ🤣 issue.

A brief summary would be: while the 2024 DESI data presents some evidence favouring dynamical dark energy, it does not conclusively refute the cosmological constant hypothesis. The possibility of a constant vacuum energy remains within the current data uncertainty, and further observations are required to resolve this question definitively.

About the Equation of State (EOS)

The parameters w0​ and wa​ are used to describe the time evolution of the dark energy equation of state (EOS). They appear in a common parameterization of the dark energy EOS, which is expressed as: w(a)=w0+wa(1−a). Here, w0​ represents the present-day value of the dark energy EOS, while wawa​ describes how the EOS changes over time

The scale factor a is related to redshift z by a=1/(1+z),A few other notes for youngsters with big brains:

• Constant w: If wa​=0, then w(a)=w0, representing a constant equation of state

• Cosmological constant: For w0​=−1 and wa​=0, the model reduces to the cosmological constant (Λ) in ΛCDM (the so-called “Standard Model of Cosmology” — not directly related to the SM of particle physics (SMoPP), but the two are coupled, since baryonic matter properties are given by the SMoPP).

• Dynamical dark energy: Non-zero wa​ indicates evolving dark energy, with its behavior changing over cosmic time.

• Observational constraints: other current data provide bounds on these parameters. For instance, a recent analysis combining various datasets found w0​=−1.013 (+0.038,−0.043), consistent with a cosmological constant.

• Phantom divide: Values of w<−1 are referred to as “phantom” dark energy. Some observations hint at a slightly phantom EOS (w∼−1.03), though evidence remains inconclusive.

Thermodynamic constraints: The second law of thermodynamics can place additional restrictions on the w0​−wa​ parameter space.

• This parameterization allows for a flexible description of dark energy behaviour while remaining simple enough for efficient observational testing

The phantom divide

What is this you ask?

In this phantom regime, when w(a)<−1, the energy density of dark energy would increase as the universe expands, rather than decrease or remain constant. This behaviour is considered exotic and challenges our understanding of physics.

The term “phantom” is used metaphorically to describe this strange, ghost-like behaviour of dark energy that seems to defy conventional physical laws. If w < -1 and remains so, it could lead to a scenario called the “Big Rip,” where the expansion of the universe accelerates so rapidly that it eventually tears apart all structures, from galaxies to atoms.

Current Theoretical Alternatives

Just bookmarking here a few of the theoretical angles on time-varying Λ.

Some plausible “quantum gravity'' and other quantum gravity approaches can motivate a time-varying cosmological constant or dark energy.

1. Causal Set Theory and “Everpresent Λ":
   Causal Set Theory predicts that the cosmological constant Λ is “everpresent” and fluctuates between positive and negative values over cosmic time. This model generates a space of histories of dark energy, which can be compared to observational data.

2. Quantum Gravity and Quintessence:
   Some quantum gravity approaches suggest dark energy could be dynamical, known as quintessence . In this scenario, dark energy’s density changes over time, potentially decreasing, which is described as “like a ball rolling down a hill.”

3. Quantum Origins of Gravity:
   A recent theoretical study proposes that gravity’s quantum origins might explain dark energy[3]. This model suggests that interactions between quantum objects making up space can cause an acceleration in cosmic expansion at later stages, resembling dark energy.

4. Swampland Conjecture:
   The “swampland” conjecture in string theory suggests that a constant dark energy is incompatible with quantum gravity, favoring a time-varying Swampland dark energy .

5. Quantum Disentanglement:
   Some researchers propose that dark energy could be a consequence of quantum disentanglement processes , potentially allowing for time variation.

6. Cosmologically coupled black-holes . Whoa! This is a good one.

It’s important to note that while these theories provide motivations for time-varying dark energy, they are still speculative and require further theoretical development and observational confirmation. The standard ΛCDM model with a constant cosmological constant remains consistent with most current data, though tensions exist that may be alleviated by dynamical dark energy models.

I rather like options 5 and 6. They also seem to be closely related?

The Most T4G-ish

I am rather liking El-Naschie, M.S., (2017). Quantum Disentanglement as the Physics behind Dark Energy although that author is pretty eccentric.

Nerds 🤓🤣 more thought.

Dark Matter?

Although most press releases about DESI 2024 do not mention dark matter, that is only because few astronomers are considering the Turok & Boyle revision of the right-handed neutrino as the perfect dark matter candidate.

But DESI 2024 does help, the survey narrows the possible sum of neutrino masses, ∑mν​<0.071eV This upper limit is very close to the minimum possible value known from laboratory experiments (∑mν​>0.06eV) for the normal hierarchy ordering (favoured).

Recall, for the RH neutrino to be dark matter the lightest left-handed neutrino must have nearly zero mass. DESI is heading in this direction, so good news for the CPT-Symmetric Universe hypothesis.

Paradigm Shunting?

Overall this is good news from DESI, it is interesting but not too interesting. GR is confirmed as still our best model for gravity. I did not here much about Dark Matter. The Dark Energy (vacuum pressure) still seems to be negative, but could be time-varying. That’s the bizarre bit.

Someone like Hossenfelder might get up on her soap box and rail against the establishment that they are not taking the data seriously, and so need to MONDify or completely revise theoretical cosmology and turf out ΛCDM. I think it is too early for that. So this is not like macroeconomics territory where entire generations of workers have been held hostage to a hostile and cruel and unnecessary ideology (neoclassical monetarism and the NAIRU myth.)

It would be cool if someone had a minimal conservative extension of GR/spacetime that had a time varying Λ. I think the sanguine assessment right now is that no one ever bothered to look for that! Everyone just assumed the vacuum was not too wild.

But could this revive String Theory? In String Theory the vacuum is not well-defined, and so a model is available where vacuum states are determined dynamically. This could also be true without 11-dimensional spacetime.

In the CPT-Symmetric Universe the vacuum state is largely hypothesized to be determined by zero-dimension Bogoliubov scalars, they are not particles (they have zero propagator). Despite not being particles, these scalars are like real existing accounting tools that cure the vacuum (prevent Weyl and vacuum energy anomalies).

However, as such, they are only accounting tools. Why would an accounting rule vary with time?

Hence, to my mind, there is a possible lovely minimal conservative extension of ΛCDM, that has a real physical model for the vacuum state, and it can have dynamical properties. Who the heck knows what though? It is totally unexplored territory from what I can tell (I did not conduct an arXiv search to rally check, I only did a quick scan:

• Chen, W. and Wu, Y.S., 1990. Implications of a cosmological constant varying as R− 2. Physical Review D, 41(2), p.695.

• Sinha, K.P., Sivaram, C. and Sudarshan, E.C.G., 1976. The superfluid vacuum state, time-varying cosmological constant, and nonsingular cosmological models. Foundations of Physics, 6, pp.717-726.

• Barrow, J.D., 1996. Time-varying G. Monthly Notices of the Royal Astronomical Society, 282(4), pp.1397-1406.

• Aldrovandi, R., Almeida, J.P. and Pereira, J.G., 2003. Time-varying cosmological term: emergence and fate of a FRW universe. arXiv preprint gr-qc/0312017.

• Singh, C.P., 2011. Cosmological models with time-varying gravitational and cosmological “constants”. Astrophysics and Space Science, 331, pp.337-342.

Barrow crops up… lol. Been a while.

These all go in my “all abstract, no grok,” basket.

A problem with getting motivated to read them in more depth is that they are really astronomical consequences of Λ(t), not models for Λ(t), so this leaves me flat-footed.

The tantalizing prospect from DESI 2024 is that a whole lot of research papers might be coming out in the next years that have actual models of the vacuum state for all the various theories from Strings to Loops and beyond. Thanks to Turok & Boyle the good old LR Standard Model can also play that game.

There are a few old models for time-varying Λ, such as,

• Quintessence

• Phantom energy (don’t ask)

• Chaplygin gas , and this paper compares a Chaplygin gas with a quintessence model.

The Chapylgin gas is only an equation of state: p=−Aρp=−ρA​ it is not a proposition for an actual cosmological fluid. Same I think with so-called phantom energy. Such models however employ scalar fields to describe the cosmologies for these constituents in spacetime, and this cannot be a pure coincidence with the need for the 36 dimension-zero Bogoliubov scalars in the CPT-Symmetric SM.

Horizons

One thing which might be telling a large chunk of the Dark Energy story is the fact we have astronomical horizons. It is a known fact (I want to say) that any theory of quantum gravity will exhibit Unruh radiation, which means any moving horizon will look like a generator of particles ‘out of nothing’. Except they are real for honest-real real-ass particles!

The thing is, the vacuum produces them, and more. Any form of energy will have a component in the Unruh radiation. Just you try telling the vacuum otherwise. So this seems like one way to have a varying dark energy content. It is not due to a dynamical vacuum, but rather due to our cosmological horizons being dynamic. Justathought.

However, I have to throw a little bit of conservative shade on the DESI 2024 hype. When you observe an apparently time varying cosmic parameter, and your method of data analysis involves looking back further in time, aren’t you subject to the most extreme systematic uncertainties in the history of science biased towards the parameter looking like it varies in time? Why yes, you are.

It is thus by far, imho, the more parsimonious explanation for the discrepancy with ΛCDM that the DESI data analysis still has kinks to be worked out. Many an astronomy signal before has been sent to the Elephant Graveyard .

I am no expert astronomer, so my opinion here is as good as any lay persons. We might trust the astronomers they know their systematic uncertainties. But then there are always the Rumsfeldian unknown Unknowns. LOL. Fatal in neocon chicanery, mildly annoying for Nobel Prize hopium in astro-physics (hey, no shade on them… taking money off the Oil soaked Norwegians just for doing thinking good 🤣 is not a bad aspiration).

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I don’t know, but it seems like there is some sort of emerging or converging view here in the wide literature on the cosmological constant-ish.

Also, I’d pose this to your favourite Ai bot:

Kirillov and Savelova are theoretical physicists who have proposed a “wormhole gas” model for dark matter. However, could one reinterpret their model as a form of dark energy instead? This reinterpretation could be based on Coleman, Hawking, Prescott, et al, who long ago showed that a wormhole gas was an ideal small positive Λ candidate (they predicted a small positive cosmological constant). If so, is the equation of state for such a model similar to “phantom”, i.e., p=−A/ρ?
I think it is you know.

You know…. I prefer the right-handed neutrino for the dark matter, and I prefer a physical Λ not a dark arts Λ.

Mild flu virus on me today. Too lethargic to go into more depth. Just some last feeble punches:

1. Beware the anti-establishment folks who are blindly anti-=government. The aim is to have government under our loosely collective control, not the control of the few.

2. In physics, it is far less dangerous (for society) to entertain heretics and anti-establishment types. But nevertheless Eric Weinstein is still dangerously insane.

Unlike Sabine Hossenfelder’s opinion on science funding, here from the MMT window panoramic views, government grants for useless paper science research is a good thing. It’s basic income for people who like to only think. Not directly inflationary to first order, and keeps the geeks out of trouble designing weapons systems in order to be able to eat lunch. And you just never know when a crackpot turns out to be a genius. The probability is irrelevant, if government grant agencies knew ahead of time who will be the geniuses crowned in 2030 people running these agencies would clearly have godlike powers and there’d likely be peace in the world (every god knows that war and tryranny promote Idol worship).