Arthur Howell’s Post

Interview with Paul Adrien Maurice Dirac (1902–1984), Nobel Prize in Physics 1933, "for the discovery of new productive forms of atomic theory". In particle physics, the Dirac equation is a relativistic wave equation derived by British physicist Paul Dirac in 1928. In its free form, or including electromagnetic interactions, it describes all spin-1⁄2 massive particles, called "Dirac particles", such as electrons and quarks for which parity is a symmetry. It is consistent with both the principles of quantum mechanics and the theory of special relativity,[1] and was the first theory to account fully for special relativity in the context of quantum mechanics. It was validated by accounting for the fine structure of the hydrogen spectrum in a completely rigorous way. The equation also implied the existence of a new form of matter, antimatter, previously unsuspected and unobserved and which was experimentally confirmed several years later. It also provided a theoretical justification for the introduction of several component wave functions in Pauli's phenomenological theory of spin. The wave functions in the Dirac theory are vectors of four complex numbers (known as bispinors), two of which resemble the Pauli wavefunction in the non-relativistic limit, in contrast to the Schrödinger equation which described wave functions of only one complex value. Moreover, in the limit of zero mass, the Dirac equation reduces to the Weyl equation. Although Dirac did not at first fully appreciate the importance of his results, the entailed explanation of spin as a consequence of the union of quantum mechanics and relativity—and the eventual discovery of the positron—represents one of the great triumphs of theoretical physics. This accomplishment has been described as fully on a par with the works of Newton, Maxwell, and Einstein before him.[2] It has been deemed by some physicists to be the "real seed of modern physics".[3] In the context of quantum field theory, the Dirac equation is reinterpreted to describe quantum fields corresponding to spin-1⁄2 particles.  https://lnkd.in/dE-intfB Dirac equation ( i ℏ γ μ ∂ μ − m c ) ψ ( x ) = 0 https://lnkd.in/dBFd6syy

EngLab@NTUA and QuAID³ were at Madrid for the 19th European Mechanics of Materials Conference and George Pissas presented recent developments on resolving fractures in long fibre composites. We very much thank the organizers for setting up a wonderful and inspiring venue. The research project QuAID³ is implemented in the framework of H.F.R.I call “Basic research Financing (Horizontal support of all Sciences)” under the National Recovery and Resilience Plan “Greece 2.0” funded by the European Union – NextGenerationEU (H.F.R.I. Project Number: 15097). ΕΛΙΔΕΚ - Ελληνικό Ίδρυμα Έρευνας και Καινοτομίας

New preprint on arxiv, together with Ludovico Tesser, Christian Spånslätt Rugarn, Inès Safi, and Janine Splettstoesser: "Thermodynamic and energetic constraints on out-of-equilibrium tunneling rates" https://lnkd.in/dXGZaQr4. In this work, we show how thermodynamic quantities constrain the transition rates between two weakly coupled quantum systems in nonequilibrium conditions, specifically in the presence of a temperature bias. We find that the thermodynamic and energetic costs for establishing or depleting the temperature bias put a bound on the nonequilibrium response of the transition rates to small temperature changes. Our results are applicable to a large class of experimentally relevant systems, as we exemplify by analyzing an atom coupled to a nonlinear cavity and few-sites tight-binding chains, which can be relevant for molecular transport. Special thanks to Ludovico Tesser for the hard work!

I am excited to announce that we have published our second paper as a preprint on arXiv, titled "Gravitational wavefunctions in JT supergravity" (https://lnkd.in/erXaTDqY ). This work focuses on solvable lower-dimensional models of quantum gravity, with a particular emphasis on JT supergravity. In this paper, we leverage the group theoretic framework developed in our previous paper to describe the gravitational wavefunctions of JT supergravity as constrained representation matrices of this supergroup. This approach reveals the underlying structure governing the supergravity model.

Today we recorded the last video before the official launch of geoversity.io. If you want (and you should!) to learn 'why you need boring statistics to save your favourite animals (or plants, or fungi)', then you better stay tuned, because Thomas Groen explains it like no other in his video that will be featured on this cutting-edge platform on geospatial science, which will go live in a few weeks!

Learn more about the emerging field of complexity science and visualization through the lens of interdisciplinary creativity in this article from Liuhuaying Yang and Paul Kahn: https://ow.ly/z2AM50RB5rN

In 1974 we beamed a radio transmission into space that changed the way we think about our place in the cosmos https://trib.al/507OGsC

I am pleased to announce that our new paper on the characterization of a deep conductor using a machine learning-assisted magnetotelluric method is now available online. In this contribution, which I am happy to be part of, we use a new workflow to substantiate the characterization of a prominent deep sediment conductor in the hyper-extended Bjørnøya Basin (SW Barents Sea). This conductor was previously identified in smooth resistivity models from 3D deterministic inversion of magnetotelluric data.  For more information, please refer to the paper entitled “Deep basin conductor characterization using machine learning-assisted magnetotelluric Bayesian inversion in the SW Barents Sea” by Romain Corseri, Hoël Seillé, Jan Inge Faleide, Sverre Planke, Kim Senger, Mansour M. ABDELMALAK, Leiv Jacob Gelius, Geoffroy Mohn, Gerhard Visser https://lnkd.in/dw3D2axR

[ 🎲 Day on probabilities - GDR IFM] 🗣 We are delighted to announce our 5th speaker: Tatiana Starikovskaya from École normale supérieure. Her subject is "𝐻𝑜𝑤 𝑃𝑟𝑜𝑏𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝐻𝑒𝑙𝑝𝑒𝑑 𝐴𝑐ℎ𝑖𝑒𝑣𝑒 𝑈𝑙𝑡𝑟𝑎-𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝐴𝑙𝑔𝑜𝑟𝑖𝑡ℎ𝑚𝑠 𝑓𝑜𝑟 𝑃𝑎𝑡𝑡𝑒𝑟𝑛 𝑀𝑎𝑡𝑐ℎ𝑖𝑛𝑔". Read her abstract: "In the fundamental problem of 𝐩𝐚𝐭𝐭𝐞𝐫𝐧 𝐦𝐚𝐭𝐜𝐡𝐢𝐧𝐠, one is given two strings, usually referred to as a 𝐩𝐚𝐭𝐭𝐞𝐫𝐧 and a 𝐭𝐞𝐱𝐭, and must decide whether the pattern appears as a substring of the text. In 1970, Knuth, Morris, and Pratt gave the first 𝐥𝐢𝐧𝐞𝐚𝐫-𝐭𝐢𝐦𝐞 and 𝐥𝐢𝐧𝐞𝐚𝐫-𝐬𝐩𝐚𝐜𝐞 𝐚𝐥𝐠𝐨𝐫𝐢𝐭𝐡𝐦 for pattern matching. One can argue that this algorithm is optimal: one has to use linear time to read the input and one has to use linear space to store the input. In this talk, we will discuss how probability helped surpass these barriers." 👀 Hope to see you there! 📅 𝐒𝐞𝐩𝐭𝐞𝐦𝐛𝐞𝐫 𝟏𝟔, 𝟐𝟎𝟐𝟒 ⏰ 9am to 6pm 📍 Institut Henri Poincaré, Paris 🌐 More information and registration (free but mandatory) on the event website: https://lnkd.in/gygtZNuJ

ELEMENTS OF NEUROGEOMETRY - VOLUME II - SPRINGER A notable scientific event of 2024, Professor Jean Petitot will release volume II of his work "Elements of Neurogeometry" (more than 1400 pages) from SPRINGER. The deepest and most accomplished thinking to model the connectome of the primary visual cortex. It is a major work, the fruit of work over several years. I was very honored that Professor Petitot sent me the French version first. I invite you to watch his keynote at GSI'21 conference at Sorbonne University: "The primary visual cortex as a Cartan engine" https://lnkd.in/e-iyBYRC Here cover of Volume I: