Happy birthday to #astrophysicist Cecilia Payne-Gaposchkin (1900-1979), trailblazer for women in #astronomy who discovered that hydrogen and helium are the most common elements in the universe.
Born England, she won a scholarship to Newnham College Cambridge in 1919 where she heard a lecture which changed her life. She wrote, “My world had been so shaken that I experienced something very like a nervous breakdown.” 🧵
In #QuantumFieldTheory, scattering amplitudes can be computed as sums of (very many) #FeynmanIntegral s. They contribute differently much, with most integrals contributing near the average (scaled to 1.0 in the plots), but a "long tail" of integrals that are larger by a significant factor.
We looked at patterns in these distributions, and one particularly striking one is that if instead of the Feynman integral P itself, you consider 1 divided by root of P, the distribution is almost Gaussian! To my knowledge, this is the first time anything like this has been observed. We only looked at one quantum field theory, the "phi^4 theory in 4 dimensions". It would be interesting to see if this is coincidence for this particular theory and class of Feynman integrals, or if it persists universally.
More background and relevant papers at https://paulbalduf.com/research/statistics-periods/ #quantum#physics#statistics
British astronomer and astrophysicist Cecilia Payne-Gaposchkin was born #OTD in 1900.
In 1925 she proposed that stars were composed primarily of hydrogen and helium. Her groundbreaking conclusion was initially rejected, because it contradicted the science of the time, which held that no significant elemental differences distinguished the Sun and Earth. Independent observations eventually proved that she was correct.
Books by Cecilia Payne-Gaposchkin are coming soon at PG.
Interview of Cecilia Payne-Gaposchkin by Owen Gingerich on 1968 March 5, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA
Student years at University of Cambridge, 1919-1923; move to Harvard University in 1923, and subsequent career. Comments on being a woman studying physics at Cambridge in the 1920s; influences of Ernest Rutherford, Arthur Eddington and Edward Milne on her career choice; some of her early research.
Massive black holes drag and warp the spacetime around them in extreme ways. Observing these effects firsthand is practically impossible, so physicists look for laboratory-sized analogs that behave similarly. Fluids offer one such avenue, since fluid dynamics mimics gravity if the fluid viscosity is low enough. To chase that near-zero viscosity, experimentalists turned to superfluid helium, a version of liquid helium near absolute zero that flows with virtually no viscosity. At these temperatures, vorticity in the helium shows up as quantized vortices. Normally, these tiny individual vortices repel one another, but a spinning propeller — much like the blades of a blender — draws tens of thousands of these vortices together into a giant quantum vortex.
With that much concentrated vorticity, the team saw interactions between waves and the vortex surface that directly mirrored those seen in black holes. In particular, they detail bound states and black-hole-like ringdown phenomena. Now that the apparatus is up and running, they hope to delve deeper into the mechanics of their faux-black holes. (Image credit: L. Solidoro; research credit: P. Švančara et al.; via Physics World)
The “Astrophysical and Cosmological Relativity” department at the @mpi_grav in Potsdam announces the opening of several postdoctoral appointments.
These appointments will be in the area of data analysis and its interface with waveform modeling for the recently adopted space-based gravitational-wave detector LISA.
Hey, neat! Thank you! It's an "imagination engine" - the original mod @Arotrios kbin.social wrote a detailed description here.
I never really fully got my head around it but it seems to be a combination of art, poetry, music, cinema, mythology, etc and a lot of the posts in it bounce off other posts in it.
Imagine a circular wheel rolling, without skidding, on a flat, horizontal surface. The #locus of any given point on its #circumference is called a #cycloid. It is a #periodic#curve with #period over the #circle's circumference and has #cusps whenever the point is in contact with the surface (the two sides of the curve are tangentially vertical at that point).
Interestingly, it is also the curve that solves the #Brachistochrone problem, which means that starting at a cusp on the inverted curve (maximum height), a frictionless ball will roll under uniform gravity in minimum time from the start to any other point on the curve, even beating the straight line path.
How quantum physics could 'revolutionise everything'
Growing up on a farm in Australia, Liam Hall was a mechanic "getting greasy, scraped knuckles", but in recent years his career has taken a more technical turn.
He's now the head of quantum biotechnology at CSIRO, Australia's national science agency.
Seeking Ultimates: An Intuitive Guide to Physics, Second Edition by Peter T. Landsberg, 2020
Takes us on a journey that explores the limits of our scientific knowledge, emphasizing the gaps that are left. The book starts with everyday concepts such as temperature, and proceeds to energy, the Periodic Table, and then to more advanced ideas.
La France et la Suisse tempèrent les ardeurs du CERN sur le futur collisionneur XXL
Des documents obtenus par «Le Temps» indiquent que les deux pays posent un regard mitigé sur la faisabilité, en l’état, de ce projet hors norme. Ils émettent des recommandations et s’interrogent sur sa compatibilité avec la législation
#VideoGames#GameEngines#Physics#SImulation: "A key part of many game engines is the physics engine, which mathematically models everything we’ve learned about the physical world. A strong wind can be simulated using velocity. An animated bubble might take into account surface tension. Last year, Epic released Lego Fortnite, a family-friendly mode in which players can build—and destroy with dynamite—their own Lego constructions. The game is cartoonish, but its mechanics are grounded in reality. “When the building falls, everybody knows what that’s supposed to look like,” Saxs Persson, an executive at Epic, told me. “It looks good because they got the mass right.
They got the collision volumes right. They got the gravity right. They got friction, which is really hard. They got wind, terrain. All of it has to be perfect.” Even the precise tension of pulling Legos apart, a common muscle memory, has been simulated. “It’s all math,” he said.
Yet certain things remain hard to simulate. There are multiple types of water renderers—an ocean demands a kind of simulation different from that of a river or a swimming pool—but buoyancy is challenging, as are waves and currents."
Weird #plumbing issue. In warm weather, our toilet and drains sound hollow, gurgles, etc, when flushing or draining, like when the tub is drained. In the cold months, it is fine. Last year we had the system snaked 100%. No clogs–been an issue since we bought house in 2019.
I am thinking the warm weather, wind, etc is causing negative air pressure through the main roof plumbing vent
「 Einstein's "model of gravity has been essential for everything from theorizing the Big Bang to photographing black holes," said lead author and Waterloo mathematical physics graduate Robin Wen in a statement about the research. "But when we try to understand gravity on a cosmic scale, at the scale of galaxy clusters and beyond, we encounter apparent inconsistencies with the predictions of general relativity." 」
I've just discovered (should be Sir) Roy Kerr (https://en.wikipedia.org/wiki/Roy_Kerr) , #NewZealand mathematician famous for his solution for rotating black holes published a paper last month which showed #singularities do not have to exist in a #BlackHole, at least not how the 2020 Nobel prize winner Sir Roger Penrose described. For #Physics this is a huge deal. For #NewZealand media it wasn't worth a mention. But, here is a description of what he's done if you are game. https://flip.it/iwDh4a
If you've worked with Godot to make 3D games you probably had trouble getting your characters behave reliably. If you were working on a movement-based game for any amount of time, you've probably felt the pain.
Even though the Navier–Stokes equations are deterministic, it seems that you cannot make predictions beyond a fixed time horizon, no matter how small the initial uncertainty. #physics#fluidmechanics
Swiss mathematician Johann Jakob Balmer was born #OTD in 1825.
Balmer is most renowned for his discovery of the Balmer series, a formula used to predict the wavelengths of visible light emitted by hydrogen. In 1885, he was interested in the spectral lines of hydrogen observed in the sun's spectrum. He then proposed an empirical formula to predict the wavelengths of the visible lines of the hydrogen spectrum.
What some Lemmy communities that are dead or very low number of new posts that you would like to get more active?
My pick is /c/albumartporn