Leo C. Stein is @duetosymmetry on bsky/threads/🐘
@duetosymmetry
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Physics Prof @ U of MS. Black holes, gravitational waves, general relativity & beyond. Formerly @Caltech @MIT @Cornell . Need thin pizza + fruity coffee. He/him
Oxford, MS
Joined February 2009
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Try out my interactive page for visualizing the orbits of photons around spinning black holes!
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There is only one variable here. Why are these laid out on two axes???
The correct choice is E3. I trust there’ll be no further discussion on the matter.
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This is truly the pinnacle of "When you’re accustomed to privilege, equality feels like oppression" 🤡
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Got an email about how the university library budget is tight so they might get rid of some physics journal subscriptions. This will save them $28k/yr.
Meanwhile, the head football coach here makes $4.5 MILLION per year.
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Just sent an email to all the faculty and grads in the department starting with
Dead colleagues,
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Little astrophysics whiplash this morning — start with "The universe is humming with gravitational waves from supermassive black holes", then suddenly shift gears to "We can see the plane of the Milky Way glowing in neutrinos" 🤯 What a time for science!!
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Once again, this is literally "Thanks, Obama."
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I'm sorry but we have different ideas of what is "well-known"
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what is a postdoc but a grad student persevering
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Have you ever put a breve ˘ over a variable name, just so you could take its second derivative ¨ and end up with a tiny happy face ˘̈ ? Hand and Finch went there:
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By the way, when UMiss hired the new football coach, the old coaching team was still under contract. There's like another 4 million or so being paid to football staff who no longer work for the university football program.
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As an expert on curved spacetime, I can confirm that this image contains wibbly wobbly timey wimey stuff
👀 Sneak a peek at the deepest & sharpest infrared image of the early universe ever taken — all in a day’s work for the Webb telescope. (Literally, capturing it took less than a day!) This is Webb’s first image released as we begin to
#UnfoldTheUniverse
:
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Physicists be like "yeah I know a place" and take you to Hilbert space
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Teaching myself Julia by coding up random things that pique my interests. Here are all the complex roots of polynomials of degree 11 where all coefficients are either ±1, computed with arbitrary precision. Any suggestions appreciated!
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If you invite me to your wedding, I *will* talk to your wedding guests about black holes and effective field theory.
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This evening I learned about the magic number 0.4323320871 8590286890… Drop everything left of the decimal place. Take the reciprocal of this fractional part. Keep doing that. This makes a sequence of numbers. What do you notice about the integers left of the decimal place?
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@milknketamine
@benjancewicz
A very fancy version of what glassblowers do to make glass very thin. Start with a solid glass rod, heat it up in a furnace, and pull on it, making it longer and narrower. But now use insanely high purity materials and computer control to pull cables that are a hundred miles long
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Lots of NANOGrav folks are rightly making the news but I want to highlight Prof. Sarah Vigeland, who shies away from the limelight, but is the chair of the NG gravitational-wave Detection working group. It's meticulous scientists like Sarah who make sure the analysis is right!
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Plot cos(n θ) from θ=-π to +π. Print it out on a strip of paper and wrap it around a semicircle. Now project it straight onto the diameter. What started as a trig function is now a *polynomial*. Congratulations, you just invented the Chebyshev polynomials!
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My first PhD student, Sashwat Tanay, just successfully defended his thesis today!!!
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And if you wanted to see how the sausage got made ... here's a movie of the paper-writing process!
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This is a Penrose illustration appreciation thread. Post your favorite figures below.
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Ok, since people were asking… Here's an easy way to see that Hawking radiation is not due to particle–anti-particle pair at the horizon. First thing to remember is a that a black hole is not a point, it has a size: its Schwarzschild radius Rs~2GM/c^2 (figure below)
1/
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This is a public service announcement:
The verb form of
"to take a derivative"
is "differentiate", NOT "derive".
Thank you for your attention.
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"Algebra" simply does not mean what you think it means
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Oh, come on now, topologists...
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The expansion of the universe can't be compared to speed--it doesn't make sense to say it's expanding "faster than the bullet can move". In one second, every piece of the universe (say 1 meter) grows proportionally to its length, with the same factor. Let's talk about it!
🧵 1/
If you shot a gun in space, the bullet would travel forever because the universe is expanding faster than the bullet can move
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FYI we're allowed to be excited about science results, even if they do not revolutionize everything.
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@bitfield
Hey. The geodesic equations are not Einstein's equations. The code for Interstellar only had to ray trace on a fixed analytical background spacetime (Kerr metric), rather than solve partial differential equations for the metric itself. Please correct this.
The software to create the black hole in the movie 'Interstellar' is a full implementation of Einstein's equations in 40,000 lines of C++, and rendered thousands of 23-megapixel IMAX frames on a 32,000-core render farm at about 20 core-hours per frame
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Some people are really trying to get themselves cancelled
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A physics PhD student needs a LinkedIn like a fish needs a bicycle
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Astronomy units are wild. Magnitudes per square arcsecond? nanoJansky per beam? millicrabs? At this point it's a competition to see what you can get other astronomers to believe
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Why should
#ScientistsTakeAKnee
? Thread. It's a common trope to represent science as objective and apart from the difficulties of society 1/
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Another thing to "study" before Thursday's EHT announcement: how does light orbit black holes with different spins, and at different angles? Play here:
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Back in the day, scientists used to have stacks of physical preprints on their desks that they were going to read "real soon". Thanks to the
@arxiv
, we now have 50 browser tabs open with PDFs that we're going to get to any day now. Happy birthday, arXiv!
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I'm seeing people complaining about Overleaf being down.
Did you know that you can run LaTeX on your own computer???
(Ok, I've fulfilled my snark quota for the day)
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ApJL papers are up! Get them here. There's a whole Focus Issue with 6 papers, and a summary page:
#EHT
#EHTBlackHole
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I am once again asking people to read almost anything on numerical integration instead of using 1st order forward Euler
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RUDE
...but probably fair
(from )
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Lack of US investment in the train system
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If you go through a lot of graph paper, or you want custom digital templates for note-taking apps, you should know about
@mcnees
's LaTeX graph paper package! Last weekend, we rewrote it to make it super easy to use. Links+examples below. 1/4
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Exactly 100 years ago today, the Moon's shadow passed directly over the Earth: a total solar eclipse. On that fateful day, several astronomers were working to photograph the stars by the edge of the sun at the moment of totality. This observation would rocket Einstein to fame. 1/
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I don't have a Soundcloud, donate to an abortion fund. MS:
TX:
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Could you imagine if we still had to check our email after death. No release
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I'd like to think Georgia O'Keefe would approve of our potato gratin
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Today I realized that the only reason Roombas have any hope of cleaning your floor is because it's two dimensional. Random walks in 1 and 2 dimensions have probability approaching 100% of visiting any point as the number of steps goes to ∞. Not so in 3 or higher d.
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Teaser for tomorrow's lecture on scattering:
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FYI if you learn index notation, it's all the same product rule
Mathematicians: we want our students to learn about cutting-edge data science, cloud computing, and machine learning.
Also mathematicians: Make sure to learn these differential identities for the test.
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Some tweeps were discussing: does an electron falling in a gravitational field radiate? Is that a violation of the equivalence principle of general relativity? This is a classic thought experiment! Experts were still confused in the 1950s, though EM and GR were long established.
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@teeehum
That dude on the right is Jim Gates, PhD from MIT, pictured here. An expert in SUSY/SUGRA, a trailblazer among black physicists, member of Obama's council of advisors on science, past president of the APS... I could go on
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Sorry (not sorry) to rant about this, but how does a paper get to be a PRL (and editor's suggestion) with this falsehood in the first sentence of the abstract? Gravity *does* couple to spin! More below if you want to know.
[From in
@PhysRevLett
]
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Anybody else wish they could just take math classes full time, or is that just me?
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How the heck do faculty manage their time and all their responsibilities?? Asking for a friend.
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I dare anyone currently writing a textbook on mechanics to define the Lagrangian as:
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Fun fact: cos(2π/17) can be expressed in terms of radicals.
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I kind of feel bad because it's so easy… but El*n continues to defend the title of being a dumb person's idea of a smart person. This is only ~60 digits, done back in 1706. But more importantly, our physical reality has nothing to do with how many digits of pi can be computed!
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Every student of field theory should know about Warren Siegel's 1080 page PDF titled simply "Fields." It's a fantastic resource for QFT, SUSY, and much more! Get the latest version here:
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@benjancewicz
@yelldeadcells
@Sconstio
@milknketamine
Radio waves and light waves are basically the same thing! The genius of fiber optics is making sure the (laser) light stays inside so you lose very little power.
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Academia is actually very conservative because most of us were grad students. We need more curl students.
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This puzzle is so cool and very hard! It's designed so you can unwrap the sphere (projected onto an icosahedron, I think) any way you want, so there are no edge pieces
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There's no problem with the entropy of a system decreasing—when it's not an isolated system. Let your cup of tea cool off (radiatively and evaporatively): it loses entropy. But the entropy of cuppa + universe has increased.
Same thing here. Shaking the box? Not isolated.
This video is controversial but I’d like to explore its physics in this thread
As I see it the potential energy of the nails convert to kinetic energy so it transfers energy all through the box the entropy of the system is increased 1/🧵
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Embarrassing moment: looking through some of my notes from 2016 and found the very same identity I said (a month ago) was unbeknownst to me
I'm sorry but we have different ideas of what is "well-known"
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If you just joined the generating function fan club because of Grant's video: Welcome! And, Herb Wilf has kindly made a PDF of his lovely text, generatingfunctionology, freely available on his web site:
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So we know that polynomials of degree 5 or greater can't be solved "by radicals". But that doesn't stop us from finding other closed form expressions for their roots! Today I learned how to do it for any degree n "trinomial" of this form:
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Forbidden dorito
Meet the oldest volcanic rock ever found. This is my piece of the Erg Chech 002 meteorite. It originated in the crust of an extinct protoplanet, now long since destroyed (or incorporated within another planet) and older than the Earth itself. Its age? 4.566 billion years!
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Help me remember analysis — what topology are we using where we can get "near" infinity?
The tesla website claims that the new truck can pull "near-infinite mass" hhjjkhjslsl this company is so unserious
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If the sun disappeared, then for 8 minutes we wouldn't know that the constraint equations of GR had been violated and you broke physics. Actually we wouldn't know for 0 minutes. Or -42 minutes. The constraint equations are not causal, so these statements don't make any sense.
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@GoodwillMel
@seis_matters
Don't worry, nobody is as fast as LKrauss at interpreting something benign as oppressive to him
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"This is a joke" makes the joke funnier
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The "much of GR and EM" mentioned here are just the Bianchi identities, which would be true regardless of the equations of motion. The real content of Maxwell's equations is not dF=0 (which is automatic from F=dA), but rather d*F=*J. Similarly for GR.
"The boundary of a boundary is always empty."
A huge amount of (classical) physics, including much of general relativity and electromagnetism, can be deduced directly from this simple mathematical fact.
Yet, on the surface, it doesn't seem to have much to do with physics. (1/10)
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More python fun: You can play around with a black hole binary's orientation in *real time* and see what the gravitational wave signal would be that
@LIGO
or
@ego_virgo
would detect from your point of view! [Work in progress by
@vijayvarma392
and me]
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Daaaaamn, you will *never* read a book review as painfully harsh as this one () by Robert Langlands.
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Nobody online seemed to have visualizations of the vector spherical harmonics, so I whipped this up in Mathematica (it's a bit slow for smooth interaction). The "electric type" Yᴱ is "curl-free" and the "magnetic type" Yᴮ is divergence-free.
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Some lovely plots for the history books: the Hellings-Downs curve, predicted in 1983, and finally observed by
@NANOGrav
! Their detection paper is up now:
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Happy chalk day to meeee
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Merry and Pippin decide to learn QFT
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Guide:
❤️ ❤️ Black hole binary
💕 Compact binary
💞 Late inspiral, merger
💓 Ringdown
❤️ Remnant
FYI, unicode has emoji hearts that look like they're going around each other. Imagine that the hearts are black holes
❤️ ❤️
💕
💞
💓
❤️
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It got really real. Like provost-level real. I'm joining the physics faculty at Ole Miss!
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Who else is starting their first year as faculty (or first term they have to teach) and slightly freaking out about preparing their classes? Like, I know all this material, but CAN I EVEN TEACH???
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Oh gourd I opened a SUGRA paper from the late 70s, this was a huge mistake
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I think I need to start blogging about my love of Hamiltonian dynamics via symplectic geometry. Every time I talk about it I get excited
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Lizzo has announced her completion of the binary black hole problem to 4.5 PN order, and matched to the 3 PM calculation, with arbitrary misaligned spins and eccentricity
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I'm honored to have been selected as one of the 2023 Sloan Research Fellows! Thanks to the
@SloanFoundation
, my nominator and letter-writers, and colleagues who've supported me over the years. I'm humbled by the brilliant company I'm in.
We are delighted to announce the winners of this year’s Sloan Research Fellowship! These outstanding researchers are shining examples of innovation and impact—and we are thrilled to support them. Meet the winners here: 🎉
#SloanFellow
#STEM
#ScienceTwitter
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I'm getting faster at TikZ!
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Got word yesterday that Stanley Deser, one of the giants of relativity, passed away. He is the D of ADM, contributed to foundational work in supergravity, showed 1-loop renormalizability of GR+Maxwell, and so much more. May his memory be a blessing
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Not publishing or perishing but a secret third thing
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Bless this recursion
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One of Sidney Coleman's most iconic quotes. Casually lighting up in lecture. Chugging coffee. The cheeky grin and laughing at his own jokes. This lecture had it all! (Will transcribe what he says below)
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Pro tip: Learn as much linear algebra as possible. You won't regret it.
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@DCdoozy
@SeamusBlackley
The football program for sure has its own budget. I don't think that makes this comparison any less absurd.
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cite me you cowards
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