raattgift

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14 dagen geledendiscuss

Maybe you want to leaf through a copy of Birrell & Davies or Parker & Toms again. QFTCS is good in strong gravity, and is as good as anything else at transplanckian scale (which is to say there's presently no way of knowing when around there QFTCS becomes a bad approximation to an unknown quantum gravity).

We should also remember the enormous cosmological curvature in which testable quantum systems exist; it's not just about compact objects. Significant? There's observed H-sources above z ~ 15, and of course the CMB photons at z ~ 1100. Indeed, B&D deals with Robertson-Walker spacetimes over several chapters before they get to black holes.

Also at the weak but measurable curvature regime there's e.g. Pound-Rebka, time metrology[1], and so forth, and lots of spacecraft confirming the strong equivalence principle (e.g. MESSENGER, LAGEOS) and thus supporting the LLI one expects to find in relativistic QFTs of the sort one would use to describe the behaviour of laser altimeters, distant astrophysical masers (and the Lyman-alpha forest), the spectral lines in stellar atmospheres and so on.

[1] just because it's neat and directly relevant to your comment: https://journals.aps.org/prxquantum/abstract/10.1103/q188-b1... [2025]

5 maanden geledendiscuss

In a terminal window run

  log stream --predicate 'subsystem == "com.apple.TimeMachine" AND NOT (category == "LogLimits" OR category == "VolumeViewModel")' --info --debug --style compact

and then start a backup (either from the menu bar icon, the system settings panel, or "tmutil startbackup"). This will tell you what Time Machine is doing, and might give you some useful information.

  man log

where you can use "show" and a lookback period instead of "stream".

  man tmutil

is pretty decent documentation, although the glossary secdtion ("BACKUP STRUCTURE") is important to understand if reading the whole man page.

Some things to look out for are what filesystem your newly formatted external volume is (APFS might not be great for a single spinny disk, for example), and what version of USB is in use (friends don't let friends do USB 2 mass storage). With inexpensive external media it's often a cable or power supply issue, even if (as in your case) tar appears to work. Have you checked that the contents of the tar file are correct? Also, tar files tend to be streamed out to sequential LBAs, where smaller files and (in Time Machine backups) holes might lead to a different write pattern that the drive might not like. Maybe test with rsync -c instead of tar?

6 maanden geledendiscuss

Indy led Belloq to the Ark. Belloq was looking in the wrong place because he only had the side of the headpiece of the Staff of Ra that was seared into Toht's palm, thus without Jones in the movie, the Nazis might never have acquired the Ark, failing to "take back one kadam to honor the Hebrew God, whose Ark this is".

Moreover, if Indy had not gone to Nepal, then Toht (having obtained the headpiece) and Belloq might have used a staff of the right length to find the Ark. Had they also captured Marion and taken her along to their secret island base, Jones would not have been there to tell her not to look, and thus her face would have melted off too.

Of course, Toht and his henchmen might also just have killed her in Nepal.

Alternatively, as Toht and company followed Jones to Marion, and might not have found her otherwise, they might never have had even half the headpiece of the staff of Ra, and the Ark thus would have remained undisturbed in its resting place, leaving the baddies to deal merely with the wrinkles and creases associated with aging appearing on their faces in the fullness of time.

So: Jones keeps Ravenwood alive, and puts the Belloq and his Nazi colleagues in a position to have their faces melted off. Jones also offed a couple of Nazis and other baddies along the way.

8 maanden geledendiscuss

Cool, so the European Union and overlapping institutions could see this as an opportunity to promote greater public knowledge about one of their respective member states. Seems like an argument in favour of encouraging the display of a member state's flag rather than that of a non-member-state or former member state (especially given that state's history with respect to Ireland).

Using flags alone is already poor UI since there are many languages which spill across the borders into multiple member states and non-member states, and some member states with multiple official and commonly spoken languages.

But a menu item that reads: [Irish flag] (English) like one that reads [Swedish flag] (Svenska) does not seem worse than the legacy use of the UK flag or the popular use of the US one.

9 maanden geledendiscuss

That said, whenever there is a language selection UI (e.g. at banking machines or institutional websites) in wider Europe that uses flags to represent languages -- probably not a good idea to start with, but very common -- the Irish tricolour should be used to indicate English rather than the UK or USA flags. (although cf Airteagal 8 of Bunreacht na hÉireann).

4 jaar geledendiscuss

"Didn't know to look for them; will look for them now", essentially.

Whether it's easy to resolve them (or rule them out, if not resolved) in M31 is a good question for radioastronomers.

However, from a broad Copernican Principle perspective, it would be very strange if they were in our galaxy but not M31 or other spiral galaxies.

4 jaar geledendiscuss

As shown in your reply's parent comment which I made, we are not moving in the plane of the galaxy.

There is further detail from Ethan Siegel here: https://medium.com/starts-with-a-bang/ask-ethan-37-the-earth...

Quoting a tiny fraction that article:

   The Sun appears to move *up-and-down* and in-and-out with respect to the rest of the galaxy as it revolves around the Milky Way.

(I added the asterisks for emphasis)

Additionally, amplifying my previous comment, almost no known black hole candidates' equators are aligned with their host galaxies' thin discs, at any redshift.

4 jaar geledendiscuss

> I’m just saying something that happens small also happens big: that braiding is a fact of the wave equation

There are multiple sources in the galaxy, so on purely a Gauss Law analysis I am pretty sure you are barking up the wrong tree.

4 jaar geledendiscuss

There is ample evidence contradicting the idea that the poles of pulsars are aligned with galactic north-south.

Indeed, our own solar system is not aligned with galactic north-south,

https://commons.wikimedia.org/wiki/File:Motion_of_Sun,_Earth...

and that is hardly unusual or unexpected:

http://curious.astro.cornell.edu/about-us/159-our-solar-syst...

And while we don't have many galactic black hole candidates, the ones we have and can see beaming are haphazardly oriented, and there's no reason why black holes should behave differently from their progenitor stars (oriented haphazardly) or other compact objects (the pulsars mentioned above).

4 jaar geledendiscuss

I think you are looking at the Mouse Pulsar Wind Nebula ("PWN").

Prettier X-ray and radio pictures, and animations : https://www.chandra.harvard.edu/photo/2004/mouse/index.html

A recent summary: https://ui.adsabs.harvard.edu/abs/2018ApJ...861....5K/abstra... ("famous for its spectacular tail"). There is a link to the arxiv preprint below the abstract.

Lots and lots of additional papers about The Mouse, with its conspicuously long tail, PWN G359.23-0.82, driven by its Vela-like pulsar J1747-2958.

https://www.semanticscholar.org/paper/Heartbeat-of-the-Mouse...

4 jaar geledendiscuss

Additionally,

> [the] Great Attractor look[s] like the intersection of a toroidal knot

What? Please explain.

> the galaxy seems unusually bound

Discovered features of our galaxy is about the best evidence for Copernicanism that we have. Up to the limit of current observation, there is nothing at all physically special about the Milky Way for any practical purposes.

We would therefore expect to find filamentary structures in other spiral galaxies in our sky, and be surprised (which is great for theorists) if they were not there when we look.

What do you mean by pulling our galaxy apart? What's the mechanism?

Here is where you should write down the maths you are hoping someone will check, and here is where you get to satisfy your complaint that nobody has ever answered you seriously before.

In particular, and please forgive me that I can't think of a politer way of putting it, I think you need to demonstrate that you have any idea at all about what you are talking about in your numbered paragraphs in this reply-comment's parent.

4 jaar geledendiscuss

I'm afraid I'm not much more clued-in now about what you're thinking. I'll try my best.

> ... "braiding" of any system would contribute a (small?) mass to it -- and I wanted to see the calculation

My best guess is that you are thinking that the (far from active) black hole in the central parsec of our galaxy is somehow lifting mass out of itself and into the wider galaxy, and so will briefly discuss that.

A reasonable first step towards the theoretical footing behind that is Murata & Soda 2006, in Phys. Rev. D. https://journals.aps.org/prd/abstract/10.1103/PhysRevD.74.04..., "Hawking radiation from rotating black holes and gravitational anomalies" (also at https://arxiv.org/abs/hep-th/0606069v2) where the scalar field (also seen in Hawking 1978) is literally a form of "anyon" field. I don't see how the use of the name "anyon" helps, however, and the outward flux is going to be small -- even very very small compared to the ordinary thermal collisions of gas and dust in the galaxy centre, let alone the stars there.

I think that means you're on course for an extension to the Standard Model of Particle Physics to add in some electromagnetically-non-interacting species that decays at some distance into electromagnetically-interacting ones, along the lines of various dark matter decay models, especially those designed to produce "feedback" in spite of quiet galactic centres. I don't think this is likely to bear fruit, but cf. this blog on DM->tau decay: http://honorsfellows.blogs.wm.edu/2011/06/12/decaying-dark-m...

> I assume I'm off on a wild chase, but I want to see where the math fails for my own education.

I'm afraid I can't join you on your chase, wild or not, but I think that the mathematics of black holes is reasonably accessible and easy enough to find in a variety of textbooks. Coupling an anyon field to it is an exercise in quantum field theory on curved spacetime (as in Murata & Soda) or perhaps a second-quantization of an electrovac solution based on Kerr-Newman. I'm really struggling to see how -- given the high temperatures and high particle numbers involved -- anything is to be gained by looking at the truly microscopic behaviour of the stress-energy tensor, even in the very near region of the horizon. I'm also struggling to see how such effects relating to our central black hole are not totally washed out by processes in the bulge or in the thin disc. Our central black hole is not only far from active, it is also quite small compared to the black holes we find in other galaxies, especially Seyferts and recently discovered high-redshift (z ~ 7.6) QSOs. There is also a lot of dust and gas along our line of sight to the galactic centre, and between these filamentary structures and the galactic centre. (A number of these filaments are much closer to known radio-bright supernova remnants, as detailed in the study, but don't seem very different from those far from known SNRs.) There is also no evidence for beyond-the-standard-model(-of-particle-physics) physics in the discovery of these filaments. I don't mind being asked to think about BTSM, but these filaments are a very poor justification for that.

Finally, the only knotting I expect around a quasar or microquasar are bright spots in the plasma of jets consistent with small-angle radiation, and it's hard to think of a better explanation than proper motion of the source. We see this in stellar-mass X-Ray binaries (especially nearby microquasars), for example. The absence in extragalactic quasars supports this idea, since the proper motion of those sources will necessarily be lower than galactic ones by a couple orders of magnitude.

> I want to see where the math fails for my own education

If you care to write down some math now, I promise to at least have a look at it and see if I can aim you at some additional resources which may be more helpful still.

4 jaar geledendiscuss

"Quasar" goes to luminosity, and our galaxy could never have been as luminous as any quasar we know of without some mechanism to totally block fast (matter) outflows and another to block the quenching of star formation from the negative feedback of a highly luminous galactic centre.

Our central black hole is very quiet (as opposed to active), at least a dozen orders of magnitude below the Eddington luminosity in X-rays. Quasars are at (or a very large percentage of) the Eddington luminosity, almost certainly for at least Gyr durations.

The Fermi bubbles are interesting, but around luminous AGNs (at all redshifts) we tend to find extended outflows in ionized ("hibals") and molecular gasses, and afaik we don't see anything like that associated with those gammas. AFAIR there is also a missing ~ 1250 angstrom restframe peak and an associated relativistic wind's redshift (0.1-0.2 c or 30-60 Mm/s) leading to line driving. About a decade ago there was a fair amount of discussion about the Fermi bubbles as evidence of a (not so high) luminosity AGN jet, but it seemed to require contrivances to drop in a sufficiently massive molecular cloud (~ 10^5 solar masses around 10^7 years ago, but don't quote me, not my speciality, and I was already convinced about the present << quasar luminosity (and no trace of tremendous variability or eruptive phase up to considerably more than a few percent of the Eddington luminosity) and by the stellar population).

4 jaar geledendiscuss

Along these lines, why SARAO's MeerKAT radio telescope (https://www.sarao.ac.za/science/meerkat/about-meerkat/) is the observatory behind this discovery is that it has a good view of the galactic centre because of the orientation of the Earth and solar system within the galaxy : https://commons.wikimedia.org/wiki/File:Motion_of_Sun,_Earth...

4 jaar geledendiscuss

> Nobody has ever addressed my question

Ok, I will try. I have to admit I do not fully understand what you are asking.

As noted in the link at the top, it is reasonable to speculate that these filaments are related to the activity of the galactic centre supermassive black hole. However, we do not have a quasar in our galaxy, and it is hard to imagine (consistent with evidence from this and similar galaxies at various cosmological redshifts) that the Milky Way possessed an active galactic centre which subsequently was quenched. Indeed, part of the mystery here is that there is a quite weak magnetic field permeating the galactic centre, and little outward cosmic ray pressure.

The spectral index (more details at https://arxiv.org/abs/2201.10552 §3.1, "nonthermal radio filaments that have broad spectral index distribution as well as the steepest spectral index that can readily be discerned at high latitudes", cf https://en.wikipedia.org/wiki/Spectral_index although neither link is especially friendly to non-experts) is entirely consistent with synchrotron radiation, which does not require any exotic particles at the filamentary sources of the radio emissions. As discussed in §3.2 of the arxiv preprint, all we need is highly accelerated electrons. The mechanism for accelerating the electrons is unknown, but there are several explanations available that do not require exotic particles. §4.3 discusses several plausible alternatives.

I'm no expert on anyons but I do know how Wilczek described them when he first proposed them, and Keilmann's observations of his humour, and I struggle to see what problems introducing anyons might reasonably solve at these bulk scales. Additionally, I do not see how anyonic behaviour -- rather than straightforward magnetobremsstrahlung -- could be relevant, much less a better description, at the warm temperatures in the environments of these filaments and galactic centre molecular clouds.

Unfortunately, I don't understand your second last paragraph at all.

4 jaar geledendiscuss

Judy Schmidt has combined this with Spitzer/WISE infrared data to produce the following image, and has added annotations for some of the more prominent structures (mostly the radio arc and supernova remnants in the galactic centre direction) :

https://www.flickr.com/photos/geckzilla/51854563587/

and the deep link (9144 x 5964, but no annotations) for people who have trouble with flickr's UI:

https://live.staticflickr.com/65535/51854563587_4446b5cd40_o...

4 jaar geledendiscuss

See also this very high-res image (7530x4684) of the spectral density of the Milky Way in radio, which clearly highlights (among other things) these filamentary structures:

https://www.flickr.com/photos/astro_jcm/51847931721