General Relativity Magneto HydroDynamics (GRMHD)
GRMHD (General Relativistic Magnetohydrodynamics) is the theoretical framework used to model the behavior of electrically conducting fluids (plasmas) in extreme gravitational fields. It merges General Relativity (how gravity affects space and time) with Magnetohydrodynamics (how magnetic fields affect moving, charged fluids). [1, 2, 3, 4, 5]GRMHD is computationally intensive and relies on highly specialized numerical codes to solve complex systems of partial differential equations. [1, 2]Core Physics at Play
- General Relativity: Accounts for extreme spacetime curvature (such as around black holes) using the Einstein Field Equations. It calculates effects like gravitational time dilation, light bending, and frame-dragging.
- Electrodynamics: Incorporates Maxwell's equations to track magnetic and electric fields within the plasma.
- Fluid Dynamics: Employs relativistic hydrodynamics to track the conservation of mass, momentum, and energy of the moving gas. [1, 2, 3, 4, 5]
Where It's Used
- Black Hole Accretion Disks: Modeling how gas spirals into black holes (like Sagittarius A* or M87), which helps interpret direct images from the Event Horizon Telescope.
- Relativistic Jets: Studying how magnetic fields launch and collimate ultra-fast streams of plasma blasting away from compact objects.
- Neutron Stars: Simulating the mergers of binary neutron stars and the resulting electromagnetic emissions (multi-messenger astronomy). [1, 2, 3, 4, 5, 6, 7]
Key Mechanisms and Effects
- Magnetorotational Instability (MRI): Drives turbulence in accretion disks. This turbulence acts as an effective viscosity, allowing gas to lose angular momentum and fall into the black hole. [1, 2]
- Blandford-Znajek Mechanism: A process where the rotational energy of a spinning black hole is extracted by magnetic fields, powering massive relativistic jets. [1, 2]
- Magnetic Arrest (MAD): A state where magnetic fields in the accretion disk become so strong that they halt the smooth flow of gas, funneling matter into the black hole at specific rates. [1, 2, 3]
To explore how these physics are computed, check out public computational infrastructure projects like the Einstein Toolkit or the astrophysical library.
49 comments:
Yet one of your cultural heritage. ;-)
A team — what is their motivation? From RICE.
Are they coerced, intimidated, bribed? :-p
You left out IDEOLOGY & EGO. Scientists are also paid a reasonable salary (R). What did you think of his SMEX mission with NASA. My first job at NASA in the early-mid '90s was for Code 410 - Explorers mission - the Advanced Composition Explorer (ACE). The lecturer has a mission proposal being evaluated by them.
Think his Ego will get a boost if selected? He'll be the Principal Investigator (PI) and lead the International Science Team evaluation of the data from the satellite. Many Scientific Papers will have his name on them as author and co-author. The discoveries, whether confirmatory or contrary, will all get attributed to him. EGO.
If you read the ACE Wikipedia article you'll notice a blurb about the scheduled launch date being picked years in advance. THAT is my EGO at work. We missed the launch date by 1 day... because a fishing boat entered the Range and caused a delay. We also built it for much less than the budget allocated, and were able to use the funds to get the next Explorers mission off to a "fast" start. Annual Appropriations can often get in the way of schedule progress... we made our schedule largely because under-runs on the Explorers mission ahead of us allowed us to fund the purchase our Instrument parts and materials before the allocated funding arrived. This was only possible because Congress had an independent budget line in its' annual budget for Explorers Missions, and we could intermingle the individual Explorer mission funds (a legal accounting trick).
Most of my other missions delivered "late" and "over-budget" because they didn't have separate multi-mission budget lines like the Explorers Project did. And a percentage of their budgeted money was being used to bail out other missions like the James Webb Space Telescope (JWST).
The James Webb Space Telescope (JWST) experienced massive cost overruns during its development. Initially estimated in the late 1990s and 2000 to cost around $1 billion with a 2010 launch, the project eventually ballooned to a final cost of nearly $10 billion.
I did work some billion dollar missions (like the Magnetospheric Multiscale Mission - MMS) that started out as $300m missions. But most of our delays were born of budget appropriations problems and descoping/ rescoping of work (a constellation of five to four to three and back to four satellites and the development systems needed to formation fly them.
Do you really need a full spare satellite? Can you do it with 3 instead of 4 satellites.
See? Ego keeps me talking. ;(
;p
Which... I could be using, as a spy... to boost my ego too.
But I… don't care. %^)))
Well
There's yet one thing you missing -- feel of a purpose.
What was driving Achiles, Alexander.
What allowed Odissey to turn back home (while all his pals gone…
I have Oddesseus' purpose. A wife. Children. Need there be more?
You should follow Andrew Bustamante @ Everyday Spy. He taught me R.I.C.E.!
Maybe he could give you some tips on asset manipulation.
Unlike Oddesseus, I had good fortune. I was there for them, like Chiron for Hercules... and Prometheus.
Naaaah.
You don't get it.
Odissey's purpose was… his kingdom.
Wife and children. As sailor, he can(had) em many ;-p
Assets, means they are valuable, means they not zeros ;-p
You can't really multiply or divide by zero without ending up with less than you started with. And values are relative. ;)
Then why go back? He missed his bow (so tightly strung that no others could string it)? Bow=Will, Not even a goddess could entice him with immortality and eternal youth to not return home. Ithaca wasn't what he returned FOR, it's a place he returned TO.
And Penelope's suitors could never string Oddyseus' bow.
Prometheus exchanged his portion of mortality for Chiron's immortality, which allowed Chiron to die, and Prometheus to escape the abyss. Hercules had killed Zeus' liver-eating Eagle with HIS bow (& arrow). How tightly is your bow strung?
Enough to let Chiron die, and cease his pain?
Enough to free yourself (and invention) from Zeus' abysmal enchainment (capitalism) and make it a votive offering to Zeus' honour (not will/ purpose)?
Why didn't the Greeks pursue technology? Why didn't they all pursue the hephestean arts? Was it because they knew that it would render them "lame"? What was the real riddle of the sphinx? And did Oedipus (The name Oedipus derives from the ancient Greek word Oidipous, literally translating to "swollen foot."The etymology breaks down into two Greek roots:Oideo (οἰδέω): Meaning "to swell".Pous (πούς): Meaning "foot".) "solve" it, or "extend" it? Poor Lenin er-r-r-r, William Tell!
Purpose?
The greatest weight.-- What, if some day or night a demon were to steal after you into your loneliest loneliness and say to you: "This life as you now live it and have lived it, you will have to live once more and innumerable times more; and there will be nothing new in it, but every pain and every joy and every thought and sigh and everything unutterably small or great in your life will have to return to you, all in the same succession and sequence - even this spider and this moonlight between the trees, and even this moment and I myself. The eternal hourglass of existence is turned upside down again and again, and you with it, speck of dust!"
Would you not throw yourself down and gnash your teeth and curse the demon who spoke thus?... Or how well disposed would you have to become to yourself and to life to crave nothing more fervently than this ultimate eternal confirmation and seal?
- Nietzsche, "The Gay Science" (341)
Sisyphus, your stone awaits you!
//Why didn't the Greeks pursue technology?
Because? There was no available?
Like how they could make a computer? Or even steam engine?
//And Penelope's suitors could never string Oddyseus' bow.
Hah
That was just poetic hyperbola…
Main thing that was holding em -- wife meticulously made em fight against each other.
And not for the sake of hasband, but her son. ;-p
so, why "seek zeros" then? ;-p
Zeroes are "dependent" (placeholders). One's (+) are their own "units". The Ancient Greeks didn't have the "zero". That was an Indian contribution to "the many" (from Alexander's conquests).
The Antikythera mechanism? Archimedes (Persian? - Medes) Greek fire?
They enjoyed "life" and the fine arts. Stories. Music. Poetry. Love (Sappho). Olympic Festivals. The PanAthenaen Festival. Dionysian Festivals. etc.
They planted and tended olive tree (ancient oil/ energy). And plundered and traded during the "sailing season" in the Aegean/ Med/ Black Seas. And they fished. Like Native Americans in canoes.
An Unexamined life is NOT worth living.
Hyper-Bow-La.
You should read Fenlon's "Telemachus". Rousseau recommended that every 'girl' should read it. It would teach them their "roles" in life. To seek a "Mentor" and be a "Mentee". Much as Rousseau's "tutor" educated 'Emile'.
Post-Bicameral minds... a "helmet of Athena/ Athena helmet"... like an Indian chief's headdress... full of thought capturing feathers (like a dreamcatcher).
Ajax slaughtering sheep... whom the gods would destroy they first drive mad.
Oddyseus' absence compelled Telemachus (and Mentor) to seek out news of his father from Nestor in Pylos and Menelaous in Sparta... find him, and vanquish the suitors.
All while Penelope "weaved the peplos" during the day, and unweaved it during the night (stalling for the time needed for Oddyseus to return).
Weaving the peplos... the great festival of the PanAthenae... melding the 'warp' with the 'woof' (Plato, "Statesman")
...matching 1s to 0s. Mentors to Mentees. The Wise with the Just. The Temperate with the Courageous. A "peplos".
That's the dream. But like Hermes (Zeus messenger) I wear a pileus on my head. Not an Athenaean (or Corinthian) helmet.
My former slavery creates a lot of pressure upon my brow. :(
Oddyseus. 'Mentor' to the Cincinnati
Penelope... 'Mentor' to the women of Athena
<a href='https://en.wikipedia.org/wiki/Kouros">Kouros</a> and <a href="https://en.wikipedia.org/wiki/Kore_(sculpture)">Kore</a> for Plato's "Theory of perfect forms"
The Platonic realm of forms... circle, triangle, square and the 5 Platonic solids....
Patterns worthy of repetition.
;p
...or alternatively:
Here, Nietzsche is discouraging identifying oneself with a collective (especially as part of some political party, project, etc.) or subscribing to a mass-ideology. Simply put, he values individual difference, uniqueness, originality in thinking, and personally-crafted worldviews over mass movements of thought and action. The 'zero' here is a unique person (with their unique values and ways of thinking) since this can't be reproduced via 'multiplication' in the same way propaganda can produce a crowd which all subscribe to the same ideology (one who is unique and independent doesn't seek followers or to become a follower of another). In sum, he's encouraging us to engage unique, independent thinkers/persons (those who do not bind up their identity in a collective or mass-ideology) and forge our own unique identities as we stand in confrontation and contradistinction to such persons.
Go create… a chair?
for yourself, from that forms
Meaningless(consisting of mere words, words, words like mantras, preachings, ideologems, digmas) worthy only of repeating -- because without it, they'll… disappear.
Yawn
97% is attention (repetition). The other 3%?
Chat GTP is 100% attention. It cannot create "meaning" on its' own. It repeats and pays attention to our created meanings more dutifully than any human can.
The gauge transformation only goes one way.
AI's Parmenidian not Heraclitian in thought processes
The "order of things" it takes in its' learning algorithms is based upon "human" derived probabilities. The NLP attention algorithms are massively parallel, but the ultimate "order" taken is structured and determined based upon the human intuition that came before it and built the language being processed.
ASI needs to rework the flows... not just process date faster.
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