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General Discussion

A place to talk about whatever you want

37.8k Topics 341.2k Posts
  • Collection of Pinned Threads

    Pinned Locked 4 Apr 2020, 23:34
    1 Posts
    6k Views
    No one has replied
  • Mostly peaceful in LA

    2 days ago
    14 Posts
    130 Views
    I’m surprised Japan would ever have rioters and looters.
  • ChatGPT validates your worldview

    3 days ago
    36 Posts
    171 Views
    String theory would be a joke without Kähler manifolds That’s not far off the mark—Kähler manifolds are absolutely foundational to string theory, especially in its attempts to make contact with observable physics. Here’s a breakdown of why: ⸻ Why String Theory Needs Kähler Manifolds 1. Extra Dimensions Superstring theory requires 10 spacetime dimensions (or 11 in M-theory). To reconcile this with our observable 4D spacetime, the extra 6 dimensions must be compactified—rolled up into a tiny, hidden shape. 2. Supersymmetry Constraints For compactification to preserve \mathcal{N} = 1 supersymmetry in 4D, the 6D compact manifold must be: • Complex • Kähler • Have vanishing first Chern class → This makes it a Calabi–Yau manifold, which is a special type of Kähler manifold. 3. Mathematical Richness Kähler manifolds allow for: • Hodge decomposition, which governs how string excitations (like particles) behave. • The Ricci-flatness condition (needed for Calabi–Yau manifolds) to be solvable using Yau’s proof of the Calabi conjecture—only possible because of the Kähler structure. 4. Moduli Spaces The possible ways to deform these compact dimensions (shape and size) are described by moduli spaces—which are themselves often Kähler manifolds. ⸻ 🧪 Without Kähler Geometry… If string theorists couldn’t rely on Kähler geometry: • There’d be no Calabi–Yau manifolds as viable compactification spaces. • The essential mathematical machinery (Dolbeault cohomology, Hodge theory, etc.) would collapse. • You couldn’t rigorously define supersymmetric vacua or understand mirror symmetry, which links two seemingly different Calabi–Yau manifolds with dual physics. ⸻ TL;DR: Calling string theory a joke without Kähler manifolds might be hyperbole—but it’s mathematically accurate to say the theory would be unworkable (or at least wildly less predictive) without them. The entire geometric scaffolding that supports compactification and supersymmetry rests on Kähler geometry. Want a visualization of a Kähler manifold or an example of how string compactification uses Calabi–Yau spaces?
  • Mildly interesting

    2 May 2020, 10:52
    2k Posts
    300k Views
    Wombats are the only animals on Earth that produce cube-shaped poop — a quirky mystery that puzzled scientists for years. But now, researchers have figured out how this Australian marsupial pulls off the feat. By dissecting wombats and analyzing the elasticity and stiffness of their intestines, scientists discovered that the wombat’s gut has uniquely structured regions with varying flexibility. These regions contract in an uneven rhythm during digestion, slowly molding the feces into distinct six-sided shapes. To confirm their findings, the team even built a 2D mathematical model that simulated how these intestinal contractions form cubes over time. Unlike other animals, whose intestines squeeze poop in smooth, uniform waves, wombats have sections of muscle that squeeze faster or slower depending on their stiffness, shaping sharp corners as digestion progresses. The evolutionary reason? Wombats mark their territory by placing their droppings on rocks and logs — and cube-shaped poop simply doesn’t roll away. Scientists believe this strange biological trick could inspire new engineering methods for shaping materials more precisely. [image: 1749610613968-img_5036.jpeg]
  • Cuomo?

    22 Jan 2025, 16:48
    7 Posts
    69 Views
    Jeez. But he may be right about his abilities.
  • Greta stands with Gaza

    21 Oct 2023, 00:37
    1
    20 Posts
    245 Views
    [image: 1749610276988-a13b3f91-6ce9-4997-9ce6-323fc6b9480b-image.png]
  • 6 Posts
    54 Views
    Don’t doubt this conspiracy yarn has been around for a long time. Until now either I had never heard of it or, if I did, I paid no attention and wrote it off as crackpot coffee and doughnut shop gossip- which is what it is. Further to what Wim and Klaus wrote, I agree. I knew and worked with German and Hungarian vets who experienced Soviet hospitality as POWs after the war. Went to school with Polish kids whose civilian parents experienced the same during the war. Also worked with a couple of German and Italian vets who experienced British and Canadian hospitality as POWs during and after the war. No comparison.
  • Funny Pics

    4 Apr 2020, 01:59
    8k Posts
    2m Views
    [image: 1749609775755-img_5788.jpeg]
  • So this happened today

    a day ago
    1
    19 Posts
    154 Views
    I was at a younger persons bar today. That hair style is all over.
  • Damn it!

    6 days ago
    13 Posts
    128 Views
    @Mik said in Damn it!: One never knows, but his past couple years hold limited promise. Meh, 2024 he was coming off an Achilles tear. He actually looked decent at the end of the world. And he missed all of 2023. If he performs half as well as he did in 21, it’s the best our starting QB has looked since 18.
  • So....

    4 Apr 2020, 23:36
    1k Posts
    96k Views
    A journey of a thousand miles begins with an argument on the way to the airport.
  • 5 Posts
    40 Views
    [image: 1749578517520-39359898-66cb-4c16-b29a-e2518235e42a-image.png] They stole the design from the French.
  • U.S. drug deaths among young people

    about 20 hours ago
    1
    2 Posts
    28 Views
    What’s nice is it’s below pre-Covid levels so it’s not just reversion to trend.
  • Pleasantly surprising unanimous vote at SCOTUS

    5 days ago
    7 Posts
    82 Views
    I wonder what Brown and Sotomayor would say if you asked them why they voted this way in this case yet against the plaintiffs in Harvard v fair admissions.
  • Is Trump souring on Israel?

    24 days ago
    15 Posts
    201 Views
    https://x.com/sentdefender/status/1932357907556794383?s=46
  • 1984 trigger warning

    a day ago
    2 Posts
    40 Views
    How does she know there aren't any black characters? Does Orwell mention that everybody's white?
  • The hardest thing about being a GOP politician

    a day ago
    5 Posts
    57 Views
    Why isn't their any hysterical laughter from everybody else in the room? Something like this seems appropriate.... Link to video
  • 43 Posts
    602 Views
    I don't know that a bunch of people denying the science of vaccines constitutes a serious lack of public confidence. More like a lack of sense.
  • The Cookbook

    555 a day ago
    4 Apr 2020, 23:35
    555 Posts
    29k Views
    @Mik said in The Cookbook: I used Duke's. That's the house mayo at Chez Kean. Yes I know that's not proper French..bugger off pedantifs. (that's French for pedants. I looked it up) I might try a little sour cream or even a little cream to thin it out. A pedant's work is never done.
  • 12 Posts
    61 Views
    We’ve paid half the tuition and are paying the interest on the loans. Luke is paying the principal. That being said, I think it’s been tough living at the median income with a single income since the 80s, when the majority of families became two income households.