I guess I haven't been posting much this month. I'll get back to it when I have the energy, but quite a long time after testing COVID negative, I'm still really, really tired most of the time. Posts here take more thought and energy than posts at its sister blog or quick shares with a little quip or two on Facebook.
I'm trying to scan for new notable scientific journal articles and bookmark them as they come out, for future reference, with the little energy that I have.
Rest well
ReplyDeleteIn addition to the Polynesian crops, the researchers found three species of South American starchy foods: achira, sweet potato and cassava. In particular, "the identification of sweet potato starch grains in the lower levels of the Anakena site suggests an introduction of this species to Rapa Nui during the earliest settlement period," the researchers wrote. Cassava also seems to have been present on Rapa Nui long before European explorers visited its shores.
ReplyDeletehttps://www.livescience.com/archaeology/obsidian-blades-with-food-traces-reveal-1st-settlers-of-rapa-nui-had-regular-contact-with-south-americans-1000-years-ago
arXiv:2403.14309 [pdf, other]
ReplyDeleteProbing modified Hawking evaporation with gravitational waves from the primordial black hole dominated universe
Shyam Balaji, Guillem Domènech, Gabriele Franciolini, Alexander Ganz, Jan Tränkle
Comments: 18 pages+appendices, 7 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
It has been recently proposed that Hawking evaporation might slow down after a black hole has lost about half of its mass. Such an effect, called "memory burden", is parameterized as a suppression in the mass loss rate by negative powers n of the black hole entropy and could considerably extend the lifetime of a black hole. We study the impact of memory burden on the Primordial Black Hole (PBH) reheating scenario. Modified PBH evaporation leads to a significantly longer PBH dominated stage. Requiring that PBHs evaporate prior enough to Big Bang Nucleosynthesis shrinks the allowed PBH mass range. Indeed, we find that for n>2.5 the PBH reheating scenario is not viable. The frequency of the Gravitational Waves (GWs) induced by PBH number density fluctuations is bound to be larger than about a Hz, while the amplitude of the GW spectrum is enhanced due to the longer PBH dominated phase. Interestingly, we show that, in some models, the slope of the induced GW spectrum might be sensitive to the modifications to Hawking evaporation, proving it may be possible to test the "memory burden" effect via induced GWs. Lastly, we argue that our results could also apply to general modifications of Hawking evaporation.
DDeden and neo. Thanks for pointing out these points. It will be good to have a backlog of things to write about when I have enough energy.
ReplyDeleteI know you are the biggest fan of Deur for MOND,
ReplyDeletebut there are now 3 recent papers that purport to get MOND from GR, that isn't self-interaction, which was met at PF with intense skepticism. all in 2024, maybe if you combine all 3 you get MOND from GR,
and also since MOND doesn't explain galaxy clusters, or third peak of CMB, there are 2 recent papers that show PBH could be dark matter since hawking radiation changes and asteroid mass PBH isn't ruled out
arXiv:2403.13019 (gr-qc)
[Submitted on 18 Mar 2024]
Many body gravity and the galaxy rotation curves
S Ganesh
A novel theory was proposed earlier to model systems with thermal gradients, based on the postulate that the spatial and temporal variation in temperature can be recast as a variation in the metric. Combining the variation in the metric due to the thermal variations and gravity, leads to the concept of thermal gravity in a 5-D space-time-temperature setting. When the 5-D Einstein field equations are projected to a 4-D space, they result in additional terms in the field equations. This may lead to unique phenomena such as the spontaneous symmetry breaking of scalar particles in the presence of a strong gravitational field. This theory, originally conceived in a quantum mechanical framework, is now adapted to explain the galaxy rotation curves. A galaxy is not in a state of thermal equilibrium. A parameter called the "degree of thermalization" is introduced to model partially thermalized systems. The generalization of thermal gravity to partially thermalized systems, leads to the theory of many-body gravity. The theory of many-body gravity is now shown to be able to explain the rotation curves of the Milky Way and the M31 (Andromeda) galaxies, to a fair extent. The radial acceleration relation (RAR) for 21 galaxies, with variations spanning three orders of magnitude in galactic mass, is also reproduced.
Comments: 13 pages, 6 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)
Cite as: arXiv:2403.13019 [gr-qc]
I found that fresh fruit and spinach salads seemed to boost my energy levels, even though I am in the slightly pre-Boomer age bracket. Hopefully that will work for you as well. Now I was just reading a post of yours from July 19, 2012 titled: "Koide's Formula and Running Fermion Masses". I was drawn to the post while looking up CP violation in the weak interactions. Back in the 90's I hit upon a simple idea to explain why there are three and only three generations of quarks and leptons, and submitted the paper to various venues - Scientific American, Il Nuovo Cimento, and others. All declined to publish, which didn't surprise me, as it was quite speculative, among other things. But just recently a modification of that idea, which would handily explain Parity and CP violation in a more direct manner than the original idea, occurred to me. It also might explain (via a direct physical mechanism) why physicists apparently prefer to use the complex-valued pole mass for unstable particle masses. It's wildly speculative, but I'll post this new iteration of an old idea on viXra, when its finished.
ReplyDelete@DavidSchroeder
ReplyDeleteI'd be interested in reading it. Please post a link when you post something.
Sorry, I was premature to mention it on your site in that the paper, which encompasses a range of topics, is just a Microsoft word file, and not yet posted anywhere. The paper(s), only dealing with the weak interactions, written about 1993-1994 are complete, but have some inconsistencies and problems that will be addressed in the multi-topic paper that incorporates the modification in the weak interaction section. Three of 12 sections, in this paper are in need of completion. These "sections" range from a single paragraph to several pages. To be honest my paper is semi-amateur, and I'll leave it to people with much greater knowledge and certainly higher IQ's than I have to decide if it has any ultimate value. I'm currently trying to understand spinors at a level where I can (hopefully) make a deep connection between the ideas in this paper and the Standard Model.
ReplyDelete