This is a paper version of the poster I presented at EmQM17 in London.

Abstract:

Some physicists surmise that gravity lies outside of quantum mechanics. Thus theories like the standard semiclassical theory of quantum to gravity coupling (that of Rosenfeld and Møller) are possible real models of interaction, rather than a mere approximation of a theory of quantum gravity. Unfortunately, semiclassical gravity creates inconsistencies such as superluminal communication. Alternatives by authors such as Diósi, Martin, Penrose, and Wang often use the term ’stochastic’ to set themselves apart from the standard semiclassical theory. These theories couple to fluctuations caused by for instance continuous spontaneous localization, hence the term ’stochastic’. This paper looks at stochastic gravity in the framework of a class of emergent or ontological quantum theories, such as those by Bohm, Cetto, and de Broglie. It is found that much or all of the trouble in connecting gravity with a microscopic system falls away, as Einstein’s general relativity is free to react directly with the microscopic beables. The resulting continuous gravitational wave radiation by atomic and nuclear systems does not, in contrast to Einstein’s speculation, cause catastrophic problems. The small amount of energy exchanged by gravitational waves may have measurable experimental consequences. A very recent experiment by Vinante et al. performed on a small cantilever at mK temperatures shows a surprising non-thermal noise component, the magnitude of which is consistent with the stochastic gravity coupling explored here.

Stochastic Gravity and Ontological Quantum Mechanics

I have made a simple calculator to calculate the flux in watts per square metre of gravitational waves given a frequency and a strain. The idea is to show how easy it would be to hide cosmologically important amounts of energy in high frequency gravitationalScreen Shot 2018-03-11 at 2.07.37 PM waves.

If we take values of a strain of 15 orders of magnitude lower than LIGOs sensitivity, and a frequency of the Compton frequency, we get levels of energy flux and density that are very surprising. No one talks about this, though, since HFGWs are ‘known’ not to exist. I posit that we should not assume anything about gravitational waves at this point. Its an obvious place for experimentalists to work in. Are there any experiments that can detect gravitational radiation at millions of watts per square meter and nuclear frequencies? This is something that experiments should decide.

 

The_Gravitational_wave_spectrum_Sources_and_Detectors

The accepted spectrum of gravitational waves does not include the possibility of high-frequency waves.

 

Just think about it – there is no way we can tell – there may be billions of watts of gravitational wave energy passing through your body right now. They may be there, waiting for us to find them.

The comments on dark energy and dark matter in the calculator are to be interpreted as follows:

How can ‘dark matter’ be gravitational wave energy?

Dark Matter is measured as an excess of mass/energy – as it’s presence is determined by gravitational effects on regular matter. In fact- experimentally, dark matter is too tied to matter – one can predict the amount of dark matter in a galaxy or galaxy cluster, etc by simply writing down the total mass distribution of baryons! What we know of dark matter is that it’s weakly coupled to matter and that it’s much denser than the level of dark energy that is spread throughout the universe.

A possible scenario:

Dark Matter is gravitational waves associated with matter. Call it DarkGW. It looks like the presence of matter controls the amount of dark matter present and DarkGW interacts very weakly with matter (perhaps not in a linear fashion?), perhaps even violatiing the rules of quantum mechanics – after all there is no quantum theory of gravity yet.

In this scenario, dark energy is the ‘leaking’ of this DarkGW into intergalactic space. Thus there is a source for DE and it does not have to have a transcendental source. Its ‘just’ regular radiation – radiation that does not redshift as the Universe ages, as the redshifted bits are replaced on a continual basis by the DarkGW.

This tells us why the amount of DarkGW is related to the amount of Dark Energy (why are they within a factor of two of each other?). As the DarkGW has leaked out, the Universe has expanded. Once the galaxies start to get cold and far apart (say in 200billion years) – the dark energy would start to redshift, and the Universe would approach a ‘balance point’ universe instead of a runaway expansion as in modern LCDM.

 

Something is definitely wrong with dark energy:

Riess says that it could be caused by hypothetical “sterile neutrinos”, interactions with dark matter, or a strengthening over time of dark energy (which accelerates the universe’s expansion).

Sterile Neutrinos are a last ditch effort to keep dark energy as a parameter (Lambda) in Einstein’s equations. Its clear to me that the best answer is that dark energy is getting stronger over time. Dark Energy is on the right side of the Einstein equations, not the left. Lambda was a mistake. Its zero.

Hubble Space Telescope confirms mismatch in cosmic expansion

New Parallaxes of Galactic Cepheids from Spatially Scanning the Hubble Space Telescope: Implications for the Hubble Constant

 

The problem with dark matter in galaxies is that it’s just too organized. Dark matter seems to correlate too well with matter distributions.

What about a field associated with every nucleon that saturates at some level, called S here. (its saturated near dense matter like here on Earth or in the Milky Way plane, while when protons/neutrons get below a certain density, the field then eventually drops as the density of matter drops.

This solves the cuspy galaxy core problem, it also makes the BTFR (Baryonic Tully Fisher Relation) work, it also seems it would work on the bullet cluster, galactic clusters, etc.

BTFR – explained

The  Baryonic Tully Fisher Relation is one of the most accurate relations in cosmology. It’s a huge thorn in the side of LCDM cosmology, since dark matter and regular matter are not supposed to be in lockstep with one another. See Stacy McGaugh

THE SMALL SCATTER OF THE BARYONIC TULLY–FISHER RELATION

With the S field presented here, there is a saturable field associated with every nucleon. When nucleons are about a mm apart or less on average, the field is at some standard strength, then as the density lowers more, the S field maintains its density (or slowly loses density) until at some limiting low matter density this saturable field starts to drop. By the point this happens there is ~100x more energy in the saturable field than the baryonic density.

This effect can explain the BTFR as dark matter is present in quantities as a function of baryonic mass in some fashion.

Bullet Cluster

The bullet cluster poses a problem for MOND like theories – there seems to be excess dark matter causing lensing. So dark matter really exists, it seems. The field solves this nicely. No one thinks that the lensing areas of the Bullet cluster are completely free of matter, it’s just that the dark matter is not located where the bulk of the matter is.

 

The contours show the density (line of sight) of dark matter, while the X-Ray image in orange – purple shows the colliding dense regular matter.

Galactic Clusters

Clusters of galaxies would not hold together without about 5 times the mass of the individual galaxies available between the galaxies to hold the galaxies together. See Galaxy clusters prove dark matter’s existence as an intro by  Ethan Siegel .

The mechanism is clear – the intergalactic dust and gas provide the framework to energize a large S field which keeps the cluster gravitationally bound.

Properties of the S field

The S field is associated with matter and has a limiting high density. At low densities (ie halo galactic densities) the field has a mass of up to about 10 (or 100?) times the mass of a nucleon, per nucleon.

Where does the energy come from? It’s dark energy – just clumped. So S is dark energy. There is always a flow of it running around, and its pulled from dark energy as needed to saturate around matter.

What is the form of the field?

What is the minimum energy density in say GeV/m3  ? Dark Energy has an energy density of about 0.5 GeV/m3 .

The max is determined by the maximum density measured for dark matter which is about 0.5 GeV/cm3 (note the centimeter scale used by astronomers when dealing with matter clouds) see my earlier related post  Is Dark Matter merely Inactive Matter?  so about 1003 or a million times the density of dark energy.

Thus the S field saturates at a density of ~ 5e5 GeV/m3 and is present all around us.

The S field density is then some function of the matter density. It turns out that it’s a cumulative effect from all matter enclosed inside ‘R’.

Consequently, the dark matter contribution is fully specified by that of the baryons. The observed scatter is small and largely dominated by observational uncertainties. This radial acceleration relation is tantamount to a natural law for rotating galaxy.

From http://stacks.iop.org/0004-637X/836/i=2/a=152?key=crossref.21cde6b778a1e42d6160598a6ba24e03

Start at Equation 22:

Then use g_{bar} =\frac{GM_{bar}}{R^2} and simplify to

M_{DM} = \frac{M_{bar}}{e^{\sqrt{\frac{GM_{bar}}{R^2 g_{\dagger}}}} \ - 1}

Thus the quantity of DM inside a certain radius is wholly dependent on the amount of baryonic matter inside that radius. The S field is a cumulative effect of density of regular baryons.

When I use this on density I get

\rho_{DM} (< R) = \frac{\rho_{bar}}{e^{\sqrt{\frac{4/3 \pi GR\rho_{bar} }{g_{\dagger}}}} \ - 1}

This equation states that the density of dark matter depends only on the enclosed average density of baryonic matter.

Calculating the acceleration at R , given a 35kPc distance R, and a density of baryons of 1GeV per cm3 gives 4/3 \pi GR\rho_{bar}  = 1.2×10-10 m/s2 – ie g_{\dagger} which is the Milgrom acceleration. So that’s the cut where dark matter starts to be apparent, as the denominator starts to take off.

Of course, this density equation has limits on both ends. The dark matter S field has a maximum density of about a GeV per cm3 and once the density goes down to about dark energy levels one no longer calls it dark matter. Don’t forget my density version of the equation requires the average density inside R for the galaxy/gas cloud/cluster.

In my mind this S field is HFGW, but it’s not important what is the nature of the field, vs the mass of the field.

It seems to me that battling it out as MOND vs LCDM is perhaps not the best way to approach the problem as there are obviously more models around that might work. One just has to throw out some part of standard model physics!

Looking at the above more, I’m not convinced that sticking exactly to the MOND formula for mass and density is the way to go with this S field idea. I’m hoping there is a function where the density of DM is only given by the local density of matter, but perhaps that will not work. Perhaps there is something happening where DM depends on the total SUM of all all the matter interior to the radius R.

The Tully-Fisher relation (aka Baryonic TFR) is remarkable. As the diagram below shows, the relationship between Vand the baryonic mass of galaxies is just too finely tuned to be caused by dark matter. Something is up. Vis the stellar orbit velocity in the galactic halo. For more details see the paper by Lelli, McGaugh and Schombert .

Screen Shot 2018-02-24 at 5.34.29 PM

MOND (MOdified Newtonian Dynamics) is one explanation for the Tully-Fisher relation. It posits that the force towards the centre of a galaxy at large distances is not simply that of Newton, but is modified with the a0 of  1.2×10-10m/s2 in all galaxies in addition to the usual force predicted by standard Newton or General Relativity’s gravity. LCDM Dark matter is a clumsy explanation for the BTFR, as it needs fine tuning for every galaxy (or every galaxy type) in order to make that straight line be so, well, straight.

There is another way to generate an inward acceleration.

We need a force on each nucleon that changes with how much matter is inside the radius where the particle is. It somehow ‘knows’ the gravitational potential at R, and has a force that depends on that!

What I have so far on this is something to do with dark energy being more concentrated in galaxy cores, so the particle feels this dark energy slope and responds to it.

NOTE: This needs to include a dependence on the enclosed M (ie enclosed Dark Energy inside R).  I call this emission based acceleration ‘Anomalous radial nucleonic radiation’  (ARNR). MOND tells us that particles in the galactic halo can ‘weigh’ the galaxy. They have that information. So there must/might be something like dark energy concentrated in the galaxy and the particles react to this, pushing radiation outward and reacting inward. Note in the galactic core the divergence of the DE is 0 – so no extra force on the particle in the middle of the galaxy.

It might seem strange to have this concerted outward radiation pattern though! Here are some possible explanations for an outward constant radiation by the halo constituents.

    • I’m a fan of super high (nuclear and above) frequency gravitational wave (HFGW) emission/absorption in atoms and nuclei. So we might have some sort of stimulated emission from nucleons based on the outward flow of HFGW out of a galaxy.
    • Dark Energy has a value of about 1GeV/m3 . If this energy is concentrated by the galactic core, then maybe some the nucleon has a force toward the centre of the galaxy in response to the divergence of the DE field.  (i.e. lower radiation resistance in the outward direction). This Dark Energy may be some new field, (or HFGW).
    • Some other mechanism. We don’t have to know the mechanism to predict some consequences.

People don’t generally like the MOND theories because general relativity (GR) in its usual form is so well tested and accurate. LCDM is disliked by many because of the fine-tuning required in order to get everything to match observations.  ‘Anomalous radial nucleonic radiation’  (ARNR) allows GR to exist as is.

Consequences of ARNR

If nuclei really do radiate continuously, (perhaps in violation of quantum – mechanics) then there will be experimental consequences. These consequences may be largely hidden from earth-based experiments, as the emission would be isotropic and take place in some field (such as gravitational waves)  that is hard to detect with current instruments.

There may be other places where cosmological or galactic cluster observations might note this energy output.

In other posts, I have wondered if dark matter is ‘sleeping regular matter‘ and I still think that it may be a viable option, but it seems like any explanation in terms of dark matter may need to be fine-tuned to match observations.

Also, see:

http://backreaction.blogspot.ca/2016/10/what-if-dark-matter-is-not-particle.html

https://tritonstation.wordpress.com/2016/09/26/the-third-law-of-galactic-rotation/

https://tritonstation.wordpress.com/category/dark-matter/

at http://iopscience.iop.org/article/10.1088/0004-637X/802/1/18/pdf

 

 

EmQM 2017 Conference

October 11, 2017 — 2 Comments

I’m headed to London for the EmQM 2017 conference Oct 26 – 28 2017, which will I am looking forward to.

I attended in 2015. The event has the byline – the 4th International Symposium about Quantum Mechanics based on a »Deeper Level Theory«. Its mission this year is

Towards Ontology of Quantum Mechanics and the Conscious Agent
David Bohm Centennial Symposium

When I first really understood what quantum mechanics really was – in second-year undergrad at the University of Toronto, I immediately read all sorts of books and papers by and about Bohm’s theories. He made quite a change in my outlook of physics in general. I became convinced in 1985 that quantum mechanics was incomplete and that something along the lines of Bohm’s theory was the way to go. That makes the conference more special for me, and I’m sure many other attendees share the same view.

I am presenting a poster which I’m still polishing that up right now (the abstract at least was well received!). Its based on a paper called ‘Fully Classical Quantum Gravity (see link)‘. I have renamed the poster to Stochastic Gravity and Ontological Quantum Mechanics and rewritten most of it.

The poster describes the results of a paper by Vinante et al. :

Improved noninterferometric test of collapse models using ultracold cantilevers . If the results hold up, they are quite breathtaking as they state:

 

Screen Shot 2017-10-11 at 10.16.52 PM

The finite intercept, clearly visible in the inset of Fig. 3 implies that the data are not compatible with a pure thermal noise behavior, and a nonthermal ex-cess noise is present.

 

The paper details the careful procedures followed to chase down possible experimental problems. The analysis is carefully thought out. The paper claims the results show a possible signature of Adler’s Continuous Spontaneous Localization (CSL), but to me it seems like if the results hold up that its simply a great puzzle to solve! My take (in line with the ‘Fully Classical Quantum Gravity‘ paper) is that this noise is caused by the continuous emission and/or absorption of gravitational waves at nuclear frequencies.

Gravitational waves are notoriously hard to see, and these high-frequency ones (HFGWs) even more so. Indeed, since gravitational wave power goes with the square of frequency, truly tiny values of the gravitational wave strain ‘h’ (h == 0 in flat space and h < 1) make for large energy fluxes. The LIGO observations saw gravitational waves with h \sim 10 ^{-2} . The formula for the flux of a gravitational wave is:

Screen Shot 2017-10-11 at 10.33.32 PM

So LIGO can see gravitational waves with a flux of about 1^{-3} watts/m^2 , while at nuclear frequencies like 10^{15} Hz , the same formula yields an incredible 10^{19} watts/m^2 – another way to look at that flux is that it represents 400+ kg! of mass per square meter per second! I propose that results like this suggest that matter itself can be made of nothing but elaborate patterns of gravitational structures. Clearly, high-frequency gravitational structures can hold an incredible amount of energy.

Another way of thinking about this result is that anytime a better telescope is built, or one is built that looks at a new wavelength, field or pattern of signals, those signals are not only discovered, they produce deep new insights about our universe. The fact that HFGWs are hard to detect does not mean that they are not there! Indeed, instead of calculating what the flux of HFGWs might be around us, we should instead admit our ignorance and calculate what we don’t know. Huge amounts of gravitational wave energy could be whipping by everything right now and we would not know a thing about it.

It’s going to be a quick few days in London!

–Tom

 

So Leonard Susskind publishes a paper on arXiv

Dear Qubitzers, GR=QM

Which of course is what I have been saying all along. Of course Susskind’s paper is actually ‘of course’ not about QM emerging from GR, which is what I believe, and have good reason to follow up on.

Instead Susskind says:

Dear Qubitzers,
 GR=QM? Well why not? Some of us already accept ER=EPR [1], so why not follow it to
 its logical conclusion? It is said that general relativity and quantum mechanics are separate subjects that don’t fit together comfortably. There is a tension, even a contradiction between them—or so one often hears. I take exception to this view. I think that exactly the opposite is true. It may be too strong to say that gravity and quantum mechanics are exactly the same thing, but those of us who are paying attention, may already sense that the two are inseparable, and that neither makes sense without the other.

The ‘paper’ (perhaps letter is a better name), has made the rounds/  Not Even Wrong,

Instead of that happening, it seems that the field is moving ever forward in a post-modern direction I can’t follow. Tonight the arXiv has something new from Susskind about this, where he argues that one should go beyond “ER=EPR”, to “GR=QM”. While the 2013 paper had very few equations, this one has none at all, and is actually written in the form not of a scientific paper, but of a letter to fellow “Qubitzers”. On some sort of spectrum of precision of statements, with Bourbaki near one end, this paper is way at the other end.

While Woit’s nemesis Lubos Motl,

Susskind also says lots of his usual wrong statements resulting from a deep misunderstanding of quantum mechanics – e.g. that "quantum mechanics is the same as a classical simulation of it". A classical system, a simulation or otherwise, can never be equivalent to a quantum mechanical theory. The former really doesn't obey the uncertainty principle, allows objective facts; the latter requires an observer and is a framework to calculate probabilities of statements that are only meaningful relatively to a chosen observer's observations.

Sabine Hossenfelder put it visually on Twitter:

giphy

My take is about the same as these popular bloggers. Don’t really think much of it.

Except the title. QM can, I believe, emerge from Einstein’s General Relativity, in much the same way that Bush and Couder’s bouncing drops can display quantum behaviour.

My research gate page has more.

Its ridiculous that 11 dimensions and sparticles have hundreds of times more study than fundamental emergent phenomena. Emergence is the way to go forward. You don’t need a new force/particle/dimension/brane to make fundamentally new physics from what we already have in electromagnetism and general relativity.

See the search links on the side of this blog for some recent papers in these areas.

Rings coalescing

August 1, 2017 — Leave a comment

As someone pointed out on reddit, it looks like an inelastic collision.

Singularities, de Broglie and emergent quantum mechanics comes to mind for me.

The interaction causes a wave to propagate. After a time equal to the period of a wave on the ring, it separates into two.

https://file.scirp.org/pdf/ACES_2013100819104983.pdf

 

 

 

The Atomic World Spooky? It Ain’t Necessarily So!: Emergent Quantum Mechanics, How the Classical Laws of Nature Can Conspire to Cause Quantum-Like Behaviour

by Theo van Holten

The hardcover is out – for example here: Amazon.com  or at Springerbut its coming out in paperback soon – Amazon.ca . Its not coming in paperback, so I just bought the hard cover. Its ok if a paperback comes later but I can’t wait!

So what I’m saying is that I’m cheap enough to wait for the paperback, so I actually have not read the book, but it looks like its going to be a real addition to the field. Its aimed at people with at least a science background.

The book takes the discovery (by for example Couder/Bush) that quantum-like behaviour is not solely reserved to atomic particles one step further. If electrons are modelled as vibrating droplets instead of the usually assumed point objects, and if the classical laws of nature are applied, then exactly  the same behaviour  as in quantum  theory is found, quantitatively correct! The world of atoms is strange and quantum mechanics, the theory of this world, is almost magic. Or is it? Tiny droplets of oil bouncing round on a fluid surface can also mimic the world of quantum mechanics. For the layman – for whom the main part of this book is written – this is good news. If the everyday laws of nature can conspire to show up quantum-like phenomena, there is hope to form mental pictures how the atomic world works.

Here is an excerpt from the Preface to the book: (other tidbits can be downloaded from Springer)

To begin with a warning: the contents of this book may be controversial.


 The readers the author had in mind when writing this book are interested laymen, typically the kind of reader who searches bookshops for the latest popular-scientific books on developments in cosmology, on recently found fun- damental particles, or on the ever more magical findings of quantum physics. These readers presumably have some background of classical school physics (although most of it may have been forgotten). It is the kind of reader who does not like to be bothered with formulae or is even allergic to them, but who has the interest and tenacity to read sentences twice if necessary. But complete novices in the matters of the atomic world should be warned: the stories told in this book are not the same as usually found in books about quantum phenomena. This book does not give the conventional explanations. In order to read the usual stories, it is better to start in

one of the many other popular-scientific books.
 What then is this book about? This book certainly does not pretend to contain a

new theory of quantum mechanics, nor does it have the intention. Quantum theory in its present form is an almost perfect tool to calculate the behaviour of elementary particles. But the theory is “strange”, it is not something that intuitively can be understood. What this book tries to add are visualisations or mental pictures, closer to the intuition, because they are based on classical physics. However, the mental pictures in this book are not just half-baked analogies or metaphores, they are solidly founded on a large body of mathematical theory (for the diehards: the theory can be found in the appendix). This aspect makes this book different from other popular-scientific books.
Here is an excerpt from the book’s appendix. You can see that a mathematical treatment is supplied. This book is written for people who already know QM. I can think of some young physics undergrads I might buy this for!
I will do an in depth review when I’m able to get the book.
–Tom Andersen

 

 

I have been reading up on the trans-Planckian problem with the black hole evaporation process. (See the end for an update in March 2018)

Here is the problem.

An observer far away from a black hole sees photons of normal infared or radio wave energies coming from a black hole (i.e. << 1eV). If one calculates the energies that these photons should have once they are in the vicinity of the black hole horizon, the energy is becomes high – higher than the Planck energy, exponentially so. Of course if we ride with the photon down to the horizon, the photon blue shifts like mad, going ‘trans-Planckian’ – i.e. having more energy than the Planck energy.

Looked at another way: if a photon starts out at the horizon, then we won’t ever see it as a distant observer. So it needs to start out just above the horizon where the distance from the horizon is given by the Heisenberg uncertainty principle, and propagate to us. The problem is that the energy of these evaporating photons must be enormous at this quantum distance from the horizon – not merely enormous, but exponentially enormous. A proper analysis actually starts the photon off in the formation of the black hole, but the physics is the same.

Adam Helfer puts it well in his paper. Great clear writing and thinking.

Trans–Planckian modes, back–reaction, and the Hawking process

Helfer, A. D. (2000). Trans–Planckian modes, back–reaction, and the Hawking process. Retrieved from https://arxiv.org/pdf/gr-qc/0008016.pdf See also See Helfer, A. D. (2005). Quantum Character of Black Holes. Retrieved from https://arxiv.org/pdf/gr-qc/0503053.pdf

My take is simple. After reading Hefler’s paper plus others on the subject, I’m fairly convinced that black holes of astrophysical size (or even down to trillions of tons) do not evaporate.

The math is good. The physics isn’t

Let’s get things straight here: the math behind Hawking evaporation is good: Hawking’s math for black hole evaporation is not in question.

It should be emphasized that the problems uncovered here are entirely physical, not mathematical. While there are some technical mathematical concerns with details of Hawking’s computation, we do not anticipate any real difficulty in resolving these (cf. Fredenhagen and Haag 1990). The issues are whether the physical assumptions underlying the mathematics are correct, and whether the correct physical lessons are being drawn from the calculations.

Yet Hawking’s prediction of black hole evaporation is one of the great predictions of late 20th century physics.

Whether black holes turn out to radiate or not, it would be hard to overstate the significance of these papers. Hawking had found one of those key physical systems which at once bring vexing foundational issues to a point, are accessible to analytic techniques, and suggest deep connections between disparate areas of physics. (Helfer, A. D. (2003). Do black holes radiate? Retrieved from https://arxiv.org/pdf/gr-qc/0304042.pdf)

So it’s an important concept. In fact it so important that much of not only black hole physics but quantum gravity and cosmology all use or even depend on black hole evaporation. Papers with titles like “Avoiding the Trans-Planckian Problem in Black Hole Physics” abound.

The trans-Planckian problem is indicative of the state of modern physics.

There are so many theories in physics today that rely on an unreasonable extrapolation of the efficacy of quantum mechanics at energies and scales that are not merely larger than experimental data, but exponentially larger than we have experimental evidence for. Its like that old joke about putting a dollar into a bank account and waiting a million years – even at a few per cent interest your money will be worth more than the planet. A straightforward look at history shows that currency and banks live for hundreds of years – not millions. The same thing happens in physics – you can’t connect two reasonable physical states through an unphysical one and expect it to work.

The trans-Planckian problem is replicated perfectly in inflationary big bang theory.

The trans-Planckian problem seems like a circle the wagons type of situation in physics. Black hole evaporation now has too many careers built on it to be easily torn down.

Torn down:

To emphasize the essential way these high–frequency modes enter, suppose we had initially imposed an ultraviolet cut–off Λ on the in–modes. Then we should have found no Hawking quanta at late times, for the out–modes’ maximum frequency would be ∼ v′(u)Λ, which goes to zero rapidly. (It is worth pointing out that this procedure is within what may be fairly described as text–book quantum field theory: start with a cut–off, do the calculation, and at the very end take the cut–off to infinity. That this results in no Hawking quanta emphasizes the delicacy of the issues. In this sense, the trans–Planckian problem may be thought of as a renormalization–ambiguity problem.)

Some may argue that other researchers have solved the trans-Planckian problem, but its just too simple a problem to get around.

One way around it – which I assume is what many researchers think – is that quantum mechanics is somehow different than every other physical theory ever found, in that it has no UV, IR, no limits at all. In my view that is extremely unlikely. Quantum mechanics has limits, like every other theory.

Possible limits of quantum mechanics:
  • Zero point: Perhaps there is a UV cut – ( Λ ) . The quantum vacuum cannot create particles of arbitrarily large energies.
  • Instant collapse. While its an experimental fact that QM has non-local connections, the actual speed of these connections is only tested to a few times the speed of light.
  • Quantum measurement – Schrödinger’s cat is as Schrödinger initially intended it to be seen – as an illustration of the absurdity of QM in macroscopic systems.

If there is a limit on quantum mechanics – that QM is like any other theory – a tool that works very well in some domain of physical problems, then many many pillars of theoretical physics will have to tumble, black hole evaporation being one of them.

 

The other argument – Unruh saves evaporation?

March 2018 update: Ok – upon reading this paper by Steven B. Giddings

 

Where does Hawking radiation originate? A common picture is that it arises from excitations very near or at the horizon, and this viewpoint has supported the “firewall” argument and arguments for a key role for the UV-dependent entanglement entropy in describing the quantum mechanics of black holes. However, closer investigation of both the total emission rate and the stress tensor of Hawking radiation supports the statement that its source is a near-horizon quantum region, or “atmosphere,” whose radial extent is set by the horizon radius scale.

So after I wrote this I am not convinced that holes don’t radiate.

Adam’s argument is below. Basically in order for Unruh’s/Giddings ‘saving’ of black hole radiation to work, there has to be enough ‘source space’ around the black hole to generate the Hawking radiation. There might be.

 

 

Qingdi Wang, Zhen Zhu, and William G. Unruh

How the huge energy of quantum vacuum gravitates to drive the slow accelerating expansion of the Universe

It (I will call the paper WZU) has been discussed at several places:

Phys.org,

Sabine Hossenfelder at the Backreaction blog,

Reddit ,

Lubos,

Popular Press, more, more,

So why talk about it more here?

Well because its an interesting paper, and I think that many of the most interesting bits have been ignored or misunderstood (I’m talking here about actual physicists not the popular press articles).

For instance here are two paragraphs from Sabine Hossenfelder

Another troublesome feature of their idea is that the scale-factor of the oscillating space-time crosses zero in each cycle so that the space-time volume also goes to zero and the metric structure breaks down. I have no idea what that even means. I’d be willing to ignore this issue if the rest was working fine, but seeing that it doesn’t, it just adds to my misgivings.

So with the first paragraph, Sabine is talking about the a(t, x) factor in the metric (see equation 23 in the paper). I think that she could be a little more up front here: a(t, x) goes to zero alright, but only in very small regions of space for very short times (I’ll come back to that later). So in reality the average of the a(t,x) over any distance/time Planck scale or larger determines an almost flat, almost Lambda free universe -> average(a(t,x)) –> the a(t) as per a FLRW metric. I guess Sabine is worried about those instants when there are singularities in the solution. I agree with the answer to this supplied in the paper:

It is natural for a harmonic os- cillator to pass its equilibrium point a(t,x) = 0 at maximum speed without stopping. So in our solution, the singularity immediately disappears after it forms and the spacetime continues to evolve without stopping. Singularities just serve as the turning points at which the space switches.

...(technical argument which is not all that complicated)...

In this sense, we argue that our spacetime with singularities due to the metric becoming degenerate (a = 0) is a legitimate solution of GR.

As I said, more on that below when we get to my take on this paper.

The second paragraph above from the Backreaction blog concerns the fact that the paper authors used semi classical gravity to derive this result.

The other major problem with their approach is that the limit they work in doesn’t make sense to begin with. They are using classical gravity coupled to the expectation values of the quantum field theory, a mixture known as ‘semi-classical gravity’ in which gravity is not quantized. This approximation, however, is known to break down when the fluctuations in the energy-momentum tensor get large compared to its absolute value, which is the very case they study.

They are NOT using a classical gravity coupled to the expectation values of the quantum field theory. Indeed, according to WZU and the mathematics of the paper they say:

In this paper, we are not trying to quantize gravity. Instead, we are still keeping the spacetime metric a(t, x) as classical, but quantizing the fields propagating on it. The key difference from the usual semiclassical gravity is that we go one more step—instead of assuming the semiclassical Einstein equation, where the curvature of the spacetime is sourced by the expectation value of the quantum field stress energy tensor, we also take the huge fluctuations of the stress energy tensor into account. In our method, the sources of gravity are stochastic classical fields whose stochastic properties are determined by their quantum fluctuations.

So I think that she has it wrong. In her reply to my comment on here blog she states that its still semiclassical gravity as they use the expectation values of the fluctuations (they don’t as you can see by the quote above or better by looking at the paper. See how the equation 29 talks about expectation values, but the actual solution does not use them ). She concludes her comment: “Either way you put it, gravity isn’t quantized.” I think that’s also fair appraisal of  the attitude of many people on reading this paper many people don’t like it because gravity is treated classically.

 

Why I think the paper is interesting.

Gravity is not quantized: get over it

I think its interesting as their approach to connecting gravity to the quantum world is basically identical to my Fully Classical Quantum Gravity experimental proposal – namely that gravity is not quantized at all and that gravity couples directly to the sub-quantum fluctuations. Wang and co-authors apologize for the lack of a quantum theory of gravity, but that appears to me anyway as more of a consensus-towing statement than physics. Indeed, the way its shoved in at the start of section C seems like it is an afterthought.

(Gravitational) Singularities are no big deal

Singularities are predicted by many or (even all?) field theories in physics. In QED the technique of renormalization works to remove singularities (which are the same as infinities). In the rest of modern QFT singularities are only perhaps removed by renormalization. In other words quantum field theory blows up all by itself, without any help from other theories. Its naturally bad.

The Einstein equations have a different behaviour under singular conditions. They are completely well behaved. Its only when other fields are brought in, such as electromagnetism or quantum field theory that trouble starts. But all on their own singularities are no big deal in gravity.

So I don’t worry about the microscopic, extremely short lived singularities in WZU at all.

Why it’s exciting

We have WZU metric equation 23

ds2 = −dt2 +a2(t,x)(dx2 +dy2 +dz2)

a(t,x) oscillates THROUGH zero to negative, but the metric depend on a^2, so we have a positive definite metric that has some zeros. These zeros are spread out quasi periodically in space and time. If one takes two points on the manifold (Alice and Bob denoted A & B), then the distance between A and B will be equivalent to the flat space measure (I am not looking at the A and B being cosmic scale distances apart in time or space, so its almost Minkowski). Thus imagine A and B being 1 thousand km apart. The scale factor a(t, x) averages to 1.

Here is the exciting bit. While an arbitrary line (or the average of an ensemble of routes) from A -> B is measured as a thousand km, there are shorter routes through the metric. Much shorter routes. How short? Perhaps arbitrarily short. It may be that there is a vanishingly small set of paths with length ds = 0, and some number of paths with ds just greater than 0, all the way up to ‘slow paths’ that spend more time in a > 1 areas.

Imagine a thread like singularity (like a cosmic string – or better a singularity not unlike a Kerr singularity where a >> m). In general relativity such a thread is of thickness 0, and the ergo region around it also tends to zero volume. One calculation of the tension on such a gravitational singularity ‘thread’ (I use the term thread as to not get confused with string theory) come out to a value of about 0.1 Newtons. A Newton of tension on something so thin is incredible. Such a thread immersed in the WZU background will find shorter paths – paths that spend more time in areas where a << 1, these paths being much more energetically favoured. There are also very interesting effects when such gravitational thread singularities are dragged through the WZU background. I think that this might be the mechanism that creates enough action to generate electromagnetism from pure general relativity only.

A 2D slice at some time through ordinary WZU vacuum. The spots are places where a~2. The straight line from A to B has an average scale factor a of 1, while the wiggly path follows a ~ 0 and hence has an average scale factor of << 1. Note that these short paths are not unique, and there is little constraint for them to be even approximately straight.

So these thread singularities thread their way through the frothy WZU metric and as such the distance a single such thread may measure between Alice and Bob may be far far less than the flat space equivalent.

It seems to me that one could integrate the metric as given in WZU equation 23 with a shortest path condition and come up with something. Here is one possible numerical way: start out with a straight thread from A to B. Then relax the straight line constraint, assign a tension to the thread, and see what the length of the thread after a few thousand iterations, where at each iteration, each segment allows itself to move toward a lower energy state (i.e. thread contraction).

This opens up:

Quantum non-locality

Realist, local quantum mechanics is usually thought of requiring  on having some dependency on non-local connections, as quantum experiments have shown. This shortcut path may be an answer to the need for non-local connections between particles, i.e. a mechanism for entaglement, a mechanism for Einstein’s “spooky action at a distance”.

Faster than light communication.

Its always fun to see if there are realistic methods where one might beat the speed limit on light. It seems that worm hole traversal has been one of the favourites to date. I think that the WZU paper points at another mechanism – the fact that there exist shorter paths through the sub-quantum general relativistic froth of WZU. How might one construct a radio to do this? Entangled particles, particles that follow the zeros of a(t, x) preferentially, etc etc. One could imagine a brute force method to test this where huge pulses of energy are transmitted through space at random intervals. Perhaps a precursor signal could be measured at the detector, where some of the energy takes a short path through the WZU metric.

 

 

 

 


 

 

An interesting popular article that I found in Quantum . My favourite quote:

But there’s another view — one that’s been around for almost a century — in which particles really do have precise positions at all times. This alternative view, known as pilot-wave theory or Bohmian mechanics,

New Support for Alternative Quantum View

An experiment claims to have invalidated a decades-old criticism against pilot-wave theory, an alternative formulation of quantum mechanics that avoids the most baffling features of the subatomic universe.

I really like this graphic – visit the story for more!
Emergent quantum mechanics comes in many forms: stochastic electrodynamics ( Ana María Cetto) , de Broglie – Bohmian mechanics (John W M Bush) , thermal models ( Gerhard Groessing ) etc. In many of these forms of emergent quantum mechanics, particles have a physical existence and experience sub quantal movement. The paper I have just posted looks at the gravitational consequences of this sub quantal motion. An interesting finding is that while a classical Bohr hydrogen atom has a lifetime of about 10^-11 seconds, it would take that same atom 10^40 seconds or so to radiate away a few eV of energy. This indicates that the stability of the atoms is not an indication that gravity needs to be quantized, which is antithetical to Einstein in 1916:
  • “…Nevertheless, due to the inner-atomic movement of electrons, atoms would have to radiate not only electro-magnetic but also gravitational energy, if only in tiny amounts. As this is hardly true in Nature, it appears that quantum theory would have to modify not only Maxwellian electrodynamics, but also the new theory of gravitation.” – Einstein, 1916
Einstein it would seem was wrong on the gravtitational side of this.
The paper looks at possible ways to see these tiny emissions (nuclear scale emissions are higher) and thus lays out a quantum gravity experiment achievable with today’s technology.
Parameter space for a quantum gravity experiment.

The experimental parameter space. Most important thing to note is that this is a quantum gravity experiment with an achievable parameter space!

 

Here is the paper…

 
Also see these references…

Memory effect of the Kerr response to GW wave bombardment. At resonance, we have the deBroglie fundamental frequency, (i.e. compton) and after being hit with a GW, the Kerr will re-radiate with memory. Memory like in Couder.

So this memory effect combined with energy absorption and re-radiation IS QM.

Kerr ring has two frequency bands. EM band is high frequency exchange in the linear region of the singularity line, while compton – deBroglie frequency is QM.

I have written an app that detects cosmic rays on your iOS device. Its called Cosmic Ray App, its at http://cosmicrapapp.com and it actually seems to work! Get it at the app store.

Details on signal processing can be found here.

 

File 2017-02-18, 7 40 08 AM.pngFile 2017-02-13, 9 01 44 PM.pngFile 2017-02-26, 8 16 40 AM.pngFile 2017-03-27, 8 46 02 AM.jpegFile 2017-03-26, 10 11 41 PM.jpeg

In this two page paper, I look at how the relationship between the dimensions of a Kerr singularity and the strength of the electric Coulomb effect compare.

Continue Reading...

An arXiv paper by M. Chiaberge, et al.   The puzzling radio-loud QSO 3C 186: a gravitational wave recoiling black hole in a young radio source? concludes that a 3e9 solar mass black hole was ejected at a speed of 2000km/sec by the action of gravitational waves.

The story was recently highlighted in the press:

Astronomers using the Hubble Space Telescope have spotted a supermassive black hole that has been propelled out of the centre of the galaxy where it formed. They reckon the huge object was created when two galaxies merged and was then ejected by gravitational waves. 

The discovery centres on galaxy 3C186, which lies about eight billion light-years from Earth and contains an extremely bright object that astronomers believe is a black hole weighing about one billion Suns. Most large galaxies, including our own Milky Way, contain such supermassive black holes at their cores, with these huge, bright objects being powered by radiation given off by matter as it accelerates into the black hole.

See – Supermassive black hole was ejected by gravitational waves,  Hubble detects supermassive black hole kicked out of galactic core etc.

A Maximal Gravitational Wave Effect

It looks like the ejected hole was quite efficiently ‘tractor beamed’ to its ejection velocity by the gravitational wave emission.

The calculations are quite simple here, at least to an first approximation. There is a black hole formed of total mass 3 billion solar masses (using the arXiv paper as a source for all calculations). Since a solar mass black hole has a Schwarzschild radius of 3 km, that makes for a object diameter of about 18 billion km, which is also of order of the wavelength of the waves involved in a gravitational merger.

The merger time when 80% of the energy is released is roughly 100 M for two holes of mass M merging, we have M = 1.5e9 solar masses, so the light travel time is about 1.5e9*3km/3e8meters/sec or 16,000 seconds is M in this case. 100 M is the time where all the energy comes out – AKA the chirp.

So about 1,600,000 seconds is the relevant time. (For GW150914 that LIGO saw the same time would be 0.03 seconds – the holes were only 30 solar masses).

A total interaction time of 20 days. So the black hole is accelerated to a speed of 2000km/sec over 1,600,000 seconds. Thats an acceleration of 1 m/sec^2, or about 1/10 of earths gravity – funny how the numbers work out to be an acceleration that is an understandable number. The force is huge: F = ma  or 1 x10^40 newtons. The total kinetic energy is KE = 1/2 (3e9 solar masses)*(2000km/s)^2, 1.2×10^52 J.

From a conservation of momentum we can get the total momentum of the gw  E/c = (3e9 solar masses)*(2000km/s) –> 10^54 J of gw energy, this much energy was in a region about 18 billion km wide, say 1,600,000 seconds long, so an average of 1e13 J/metre^3, with a peak likely 5x that. We have an h for that from a typical expression for energy in a gravitational wave:  so h = sqrt(32*pi*G*tGW/(w**2c**2)).

Wolfram shows h as 0.8 for these values (h can not be bigger than 1, anything over 0.1 means you need to use full non linear to get accurate results). In other words the math points to some sort of maximal connection – the gravitational waves must have been very connected to the structure. Gravitational waves while only weakly connected to something like LIGO are very strongly connected – a high coupling constant – to areas with large curvature.

http://www.wolframalpha.com/input/?i=sqrt(32*pi*G*(1.7e13J%2F(metre%5E3))%2F((1e-6%2Fsecond)%5E2*c%5E2)

This is already known in the land of GR. My idea is that particles expose areas of very large curvature (naked singularities) and hence also couple extremely well to gravitational waves. Well enough that we can construct electromagnetism as an emergent phenomena of GR.

 

Podcast Link

Ian Sample has a 38 min talk with Gerard t’Hooft about a paper he presented at EmQM2011 in Vienna. The EmQM conference is held every two years, in 2015 I presented a poster called Can a sub-quantum medium be provided by General Relativity?. He also chats with Kings College London’s Dr Eleanor Knox, for some historical perspective, and Professor Carlo Rovelli for a bit about the, relational interpretation of quantum mechanics.

Ian writesscreen-shot-2017-02-11-at-12-25-45-am

The 20th century was a golden one for science. Big bang cosmology, the unravelling of the genetic code of life, and of course Einstein’s general theory of relativity. But it also saw the birth of quantum mechanics – a description of the world on a subatomic level – and unlike many of the other great achievements of the century, the weird world of quantum physics remains as mysterious today as it was a century ago. But what if strange quantum behaviour emerged from familiar, classical physics? How would this alter our view of the quantum world? And, more importantly, what would it tell us about the fundamental nature of reality?

Some notes while listening…

1min The Podcast starts off with Feynman’s guess snippet. Which is as funny as it is right.

2min That is followed by a very short well known (to quantum mechanics like us) intro to quantum mechanics.

4min Then – Ian actually uses the words ‘Emergent Quantum Mechanics’!

5-7min Gerard talks about the accuracy and weirdness of quantum mechanics.

8min Gerard  – “Classical Physics is an approximation.” – not incompatible.

8min Ian brings out ‘God does not play dice’.

9min Knox – talks about the measurement problem. The collapse. The Copenhagen Interpretation.

10min Knox talks about emergent theories – like biology, thermodynamics. So is quantum mechanics emergent? – Will EmQM help with the measurement problem?

13min Gerard – perhaps the randomness of QM does arise from stochastic classical actions. The answer is no – its not classical – “its different to its bones” from classical. Its a fundamental difference. (i.e. Bell).

15min Gerard talks about the Standard Model of Particle Physics. – Lots of people think that is all we need.

16min Gerard says the SM+QM does not feel right. It lacks a certain internal logic. Gerard thinks that the laws of QM are something of an optical illusion, ‘what is it actually that we are describing’.

17min Gerard does not want to change the equations of QM. He keeps the equations of QM. (Tom says this is at odds with most EmQM practitioners today).

18-22min Ian asks if EmQM is controversial. Gerard says yes its controversial. Bell proves that its impossible to have a classical computer reproduce QM. But Gerard has looked at the small print, and finds a way around the Bell theorem – by long range correlations – linked. This correlation is the heart of QM and is not weird – but needs a natural explanation.

22min Ian asks if this solves ‘Spooky action at a distance’. Gerard says yes it does these correlations can explain these peculiar correlations.

23min Ian says Knox calls Gerards plan ‘superdeterminism’.

25min Ian asks why do we need to change QM if it works so well? Gerard says the positive outlook on QM as being exactly correct is the Many World Interpretation. Gerard finds MWI ‘unsatisfactory’.

26min Ian points out that Gerard and EmQM are controversial.

27min Ian talks to Carlo Rovelli.

28min Carlo says we need to get used to QM – it will not be explained or overturned soon. The weakness in EmQM’s are that they do not lead to ‘new ways of thinking’ (Tom says what??). Then he talks about String theory and QM. We should just accept it as is.

30min Ian talks to Gerard about being comfortable with a theory that like QM. Gerard says that the present situation is bad with the MWI multiverse. Gerard thinks that while this works its ‘unsatisfactory’.

31min Gerard – the MWI shows that we are not there yet. We have not found the right description for our universe. All we have today are templates – that is our description, but its not what it actually is.

34min Carlo – his relational theory. Which is not MWI. Take QM seriously, relational QM takes QM at face value. The properties of objects are always measured with respect to something else. Velocity is the property of an object relative to something else.

36min Carlo starts talking about quantum gravity. We need to use relational QM to help us get to quantum gravity.

37min Science is a long sequence of us discovering that we were wrong. The world is different. If we end up agreeing on QM then this changes realism and philosophy – which Carlo thinks that will be the case. QM is the final theory for him.

Re: https://www.theguardian.com/science/audio/2017/feb/09/is-emergent-quantum-mechanics-grounded-in-classical-physics-science-weekly-podcast

Dark Matter – cuspy core problem.

Proposed solution is that dark matter wakes up, turns into matter and then self repels/forms stars, etc.This means no cusp is found.

Note how in the most tenuous gas clouds (well cold ones – the hot tenuous galactic halo does not count as its a supernova effect), the density is the exact same as the dark matter density?

From https://arxiv.org/pdf/1404.1938.pdf – note how dark matter is about about 0.2 protons per cm^3 (BR 13 measurement) . One would think that in the disk of the milky way, this close to the galactic core that the DM density is about as large as it gets. Which seems right:

screen-shot-2017-02-05-at-8-08-27-pm

The Dark Matter Halo of the Milky Way, AD 2013 – https://arxiv.org/pdf/1304.5127v2.pdf

We find that the cored profile is the preferred one, with a shallow central density of ρH ∼ 4 × 107M⊙/kpc3 and a large core radius RH ∼ 10kpc, as observed in external spirals and in agreement with the mass model underlying the Universal Rotation Curve of spirals.

From wikipedia https://en.wikipedia.org/wiki/Interstellar_medium

Note how the lowest density clouds are 0.2 – 0.5 protons/cm^3

Why is this the same density? Answer: The dark matter has a maximum density, if density gets higher it lights up and turns into protons/electrons/H – which results in WIM and WNM clouds. Dark matter might be sleeping matter.

screen-shot-2017-02-05-at-8-08-04-pm

There is a problem – what heats the Warm Ionized Medium?

Journal, T. A. (2000). EVIDENCE FOR AN ADDITIONAL HEAT SOURCE IN THE WARM IONIZED MEDIUM OF GALAXIES, (Rand 1998), 1997–2000.

Dark Matter waking up might naturally result in WIM over WNM.

Also see https://gravityphysics.com/2013/10/20/how-to-make-dark-matter/

 

Update:

You can see a clear (well kinda clear -its astronomy data…) cut at 0.04 electrons (ie protons too) per cm3. http://www.astro.wisc.edu/wham/papers-dir/hill_sins.pdf

Screen Shot 2017-10-08 at 6.48.43 PM

To me this is exciting. WIM has a density wall at about 0.02 particles / cm3 – while dark matter has a density of about the same number (within a factor of 10).

The maximum density of dark matter is about equal to the low-density wall of WIM.

Dark matter does not exist at high densities. So on a galaxy rotation curve, ie

http://iopscience.iop.org/article/10.1088/1742-6596/566/1/012008/pdf

ie – right at about the 15 kPc mark. Dark matter really not needed much below 10 kPc at all. Dark matter turns into regular matter at about these distances. Clumps of regular matter (which is how they get the rotation curves) are centers for DM – regular matter promotion. This promotion results in anomalous heating of the WIM.

Screen Shot 2017-10-08 at 7.22.21 PM

 

Also see: – the ionizing problem is still around. The O star theory seems kinda weak…

http://w.astro.berkeley.edu/~ay216/08/NOTES/Lecture08-08.pdf

Thus O stars are able to ionize the WIM (other obvious sources of Ionizing radiation are weaker), but how do the ionizing photons get from the location of these stars in the thin disk of the Milky Way to far above the mid-plane?

 

 The Li^7 problem ( https://arxiv.org/pdf/1203.3551.pdf ) might be solved if Li 7 somehow does not sleep. Then there would be more of it. Or more likely its all the same but the heavier stuff is easier to re-activate and thus collapses into star-forming more often than H or He.
Update:  remarks on the ‘Superfluid’ solution to dark matter. 
Sabine:
Their new calculations take into account that in general the dark matter will be a mixture of superfluid and normal fluid, and both phases will make a contribution to the gravitational pull. Just what the composition is depends on the gravitational potential (caused by all types of matter) and the equation of state of the superfluid. In the new paper, the authors parameterize the general effects and then constrain the parameters so that they fit observations.
 The gravitational potential is not even supposed to be detectable! In Physics, potentials are not gravitationally even locally detectable – which is why a bird can sit on a high voltage wire.
There are other problems with the superfluid:
From Uncle Al:
1) Why isn't the condensate irreversibly scavenged by the central black hole, and others, over redshift? Black holes should be visibly snacking between meals.
... 2) Added thermodynamic degrees of freedom are spectroscopically invisible?
... 3) The condensate remains unperturbed by compact-body mergers, not perturbing LIGO waveforms?

Yet the theory does solve the cuspy core problem, etc – and you can see why…

The main reason I find this idea convincing is that it explains why some observations are easier to account for with dark matter and others with modified gravity: It’s because dark matter has phase transitions! It behaves differently at different temperatures and densities.

In solar systems, for example, the density of (normal) matter is strongly peaked and the gradient of the gravitational field near a sun is much larger than in a galaxy on the average. In this case, the coherence in the dark matter fluid is destroyed, which is why we do not observe effects of modified gravity in our solar system. And in the early universe, the temperature is too high and dark matter just behaves like a normal fluid.
They are scratching all around it. Dark Matter does change phase – into ordinary matter. There is a phase of ordinary matter that does not have the energy to engage with photons – its darkened matter.

–Tom

Pilot Wave Theory and Quantum Realism

Its quite reasonably done. Host Dr. Matt O’Dowd takes a 15 min tour through the history of the theory, mentioning John von Neumann, David Bohm, Einstein, Louis de Broglie, Niels Bohr and others. The basics are there and the level is a large step higher than TV, making it good to watch even if you know all the basics already. Since 90% of popular physics over the past decade has been on strings and the multiverse, I feel its great when a theory that actually has a possibility to be correct gets some air time, so that’s why I am mentioning it here.

 

Matt mentions this video by Veritasium which has 1.3 million views! I thought QM interpretations was a backwater in the physics backwater, but its seems not always.

Matt has an account at patreon here where you can catch up with other PBS video https://www.patreon.com/pbsspacetime , and Veritasium has one here https://www.patreon.com/veritasium .

 

 

 

 

While I’m not sure myself that the EM drive actually works, the authors of the recently published EM Drive paper promote a realist interpretation of QM in order to explain the EM Drive’s thrust.

 

In the approach used in the quantum vacuum plasma thruster (also known as a Q thruster) supporting physics models, the zero point field (ZPF) plays the role of the guiding wave in a similar manner to the vacuum-based pilot-wave theories. To be specific, the vacuum fluctuations (virtual fermions and virtual photons) serves as the dynamic medium that guides a real particle on its way.
......
If the vacuum is indeed mutable and degradable as was explored, then it might be possible to do/extract work on/from the vacuum, and thereby be possible to push off of the quantum vacuum and preserve the laws of conservation of energy and conservation of momentum.

Is this publicity a good or bad thing?

This widely distributed paper puts the ideas of realist interpretations of QM in the news, as evidenced by articles here, here and here. That’s good in my opinion, as more eyes on the field, the better. Some may think that conflating the EM Drive with an emergent quantum mechanics will only harm the field once the EM Drive is put to rest in a few more years, but that’s not how publicity works.

My take on the EM Drive

There has been a lot of action about these drives over the past decade or two. I am totally open to new ‘unexplained’ physics, but one wonders why this phenomena has not been experimentally accepted after all this time and energy. For reference’s sake, a long awaited upheaval of physics may come from an unexplained yet established result along these lines, but Kuhn’s ideas suggest that well established theories can explain any result, and so we may instead have to look for theories that provide simpler explanations for established experimental results.

 

 

emdrive1