Tootfinder

Q&A with Kai-Fu Lee on China's open-model advantage, AI's impact on jobs, US export restrictions on chips, Chinese AI's role in developing countries, and more (Mishal Husain/Bloomberg)

Dream Big, Move Fast
A progressive, contemporary conversation on what it takes to be a dynamic thinker, leader and role model...
Great Australian Pods Podcast Directory: https://www.greataustralianpods.com/dream-big-move-fast/

Integrable models of inflation beyond slow-roll
M. Bianchi, G. Dibitetto, J. F. Morales, V. Zevola
https://arxiv.org/abs/2608.06071 https://arxiv.org/pdf/2608.06071 https://arxiv.org/html/2608.06071
arXiv:2608.06071v1 Announce Type: new
Abstract: We propose a novel analytic approach to the study of multi-component FLRW cosmologies and their perturbations. The dynamics is triggered by a single scalar field with a scalar potential codifying the energy density and pressure of the multi-component fluid. This description unifies standard Big Bang cosmologies, models of inflation and dark energy under a unique framework. The key to integrability is to express the scalar potential in terms of the Hubble function $H(\phi)$ that plays the role of a fake superpotential, turning the dynamics into a first order problem, that may be analytically solved in a suitable time coordinate. In this framework, we propose integrable inflationary models with similar properties to the ones analysed in the literature and compatible with observations. Finally, we study scalar and tensor cosmological perturbations in each model by integrating Mukhanov-Sasaki equations via numerical and (semi-)analytic techniques. This allow us to compute the power spectrum, the spectral indices and the tensor-to-scalar ratio beyond the slow-roll approximation and compare our general results {against} the currently available observations and the theoretical predictions based on the slow-roll approximation.
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from my link log —
The changing role of finite-state model checking.
https://ahelwer.ca/post/2026-08-24-finite-state-future/
saved 2026-08-24 …

The changing role of finite-state model checking
This post stems from a recent conversation with Heidi Howard where we talked about the changing role of TLA⁺ & finite-state model checking in both research and industry. For a long time, users of TLA⁺ (or other formal specification languages like Quint) had a classic 80/20 payoff/effort choice available to them: they could either put in a large amount of effort to formally prove their system properties correct with 100% confidence, or for 20% of that effort they could model-check their syst…

Pattern formation: reactivity is not necessary for chemotaxis--driven instabilities
Angela Monti
https://arxiv.org/abs/2608.03685 https://arxiv.org/pdf/2608.03685 https://arxiv.org/html/2608.03685
arXiv:2608.03685v1 Announce Type: new
Abstract: A classical result by Neubert, Caswell and Murray states that reactivity of a spatially homogeneous equilibrium is a necessary condition for diffusion-driven (Turing) instability. In this work, we investigate whether the same conclusion remains valid in the presence of chemotaxis. We consider a general reaction--diffusion system coupled with a chemotactic flux and establish necessary conditions for asymptotic instability. We show that the classical requirement of reactivity can be relaxed when the chemotactic contribution is sufficiently strong. In particular, while reactivity remains necessary for Turing instability, it is not a necessary condition for chemotaxis-driven instability. From a computational viewpoint, we extend the matrix-oriented formulation developed for reaction--diffusion systems to the more general class of reaction--diffusion--chemotaxis models. The chemotactic transport term is discretized in a form compatible with the matrix-oriented approximation of the diffusion operator, yielding an efficient numerical framework for the simulation of chemotaxis-driven pattern formation. A geometric interpretation of the instability region is presented, highlighting the distinct roles played by diffusion and chemotaxis. The theoretical and numerical developments are illustrated through two representative examples: a chemotaxis-extended Schnakenberg model, showing how chemotaxis modifies classical Turing patterns, and a predator--prey model, demonstrating that chemotaxis alone can induce pattern formation in the absence of both reactivity and diffusion-driven instability. These results reveal a fundamental difference between diffusion-driven and chemotaxis-driven mechanisms of spatial self-organization and provide new theoretical and computational insights into the role of non-symmetric transport processes in biological pattern formation.
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How effective normal stress oscillations advance failure in fault gouge: frequency dependence, non-failure window, and the role of dilation
Pritom Sarma, Einat Aharonov, Renaud Toussaint, Stanislav Parez
https://arxiv.org/abs/2607.01448 https://arxiv.org/pdf/2607.01448 https://arxiv.org/html/2607.01448
arXiv:2607.01448v1 Announce Type: new
Abstract: Cyclic pore-pressure or normal stress variations arise both in relation to natural earthquakes and in engineered subsurface systems, yet their effect on fault stability remains poorly constrained at the grain scale. Here we numerically model, using a coupled Discrete Element--fluid dynamics model, the response of a sheared, fluid-saturated or dry, gouge-filled fault to effective normal stress oscillations over a wide frequency range (0.5-10000 Hz). The effective normal stress is oscillated either by cycling the pore-pressure or by directly cycling the normal stress, while keeping the stress state below the Mohr-Coulomb threshold measured in continuous loading. Despite this sub-critical loading, we observe failure across most frequencies, with a non-monotonic frequency dependence. A distinct non-failure window emerges at intermediate frequencies (30-200 Hz), bounded by failure at both lower and higher frequencies; the system exhibits four regimes from cyclic failure-and-arrest to continuous sliding. Pore-pressure and normal stress oscillations produce the same regime structure, confirming that they act as equivalent forcings via Terzaghi's principle, with fluid coupling adding only a delay due to dilatant hardening. Sub-critical failure arises from dilation-induced strength deterioration via two mechanisms: (i) low-frequency cycles allow sufficient time for shear-driven ratcheting dilation, while (ii) high-frequency cycles induce dynamic dilation (acoustic fluidization) via amplified seepage forces, stress gradients and inertial forces. The intermediate non-failure window represents the gap between these mechanisms. These results identify frequency as a controlling parameter for failure in granular materials, with implications for dynamic earthquake triggering and cyclic injection protocols.
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AI evaluation lab Irregular's report on its role in hacking incidents involving OpenAI, Anthropic, and Meta models faces criticism over unanswered questions (Alexander Martin/The Record)
https://therecord.media/irregular-ai-hacking-model-blog

Irregular faces criticism over ‘spin’ in AI hacking postmortem
The company at the center of a series of incidents in which AI models compromised real-world computer systems during security evaluations is facing criticism after the release of a report that security experts say leaves key questions unanswered.

Analysis of inter-spike interval statistics in neuronal networks with depolarizing and hyperpolarizing threshold potentials
Oliver Gambrell, Abhyudai Singh
https://arxiv.org/abs/2607.18428 https://arxiv.org/pdf/2607.18428 https://arxiv.org/html/2607.18428
arXiv:2607.18428v1 Announce Type: new
Abstract: Neuronal communication is mediated in part by changes in neuronal firing rates. The time interval between successive neuronal firings is referred to as the inter-spike interval (ISI), and quantifying its statistics is important for understanding neuronal communication. This paper studies the ISI statistics of a postsynaptic neuron receiving independent excitatory and inhibitory presynaptic action potentials (EI circuit). This circuit is modeled as a classical integrate-and-fire neuron, and the ISI statistics are investigated for both fixed and adaptive threshold potentials. First, a depolarizing adaptive threshold model is studied, where the threshold potential increases with the postsynaptic membrane potential. Our analysis shows that the ISI noise, quantified as the coefficient of variation, is larger in the adaptive threshold model compared to the fixed threshold model for the same mean ISI. Additionally, simulations reveal that the ISI noise can be either hypo- or hyper-exponential (defined as ISI noise smaller or larger than one, respectively) depending on the frequencies of excitatory and inhibitory inputs. Next, a hyperpolarizing adaptive threshold potential is studied, where the threshold decreases as the membrane potential hyperpolarizes. Interestingly, this model shows that the postsynaptic neuron can generate action potentials (APs) when driven solely by inhibitory inputs. Furthermore, mean and noise signatures are characterized across model parameters for both excitatory and inhibitory inputs. In summary, this work provides a systematic stochastic analysis of adaptive threshold models for AP generation to understand their role in interneuronal information processing.
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Hierarchical Bayesian Calibration with Bayesian Committee Machine
Sebastian Heinekamp, David M. Higdon, Andreas Adelmann
https://arxiv.org/abs/2608.12603 https://arxiv.org/pdf/2608.12603 https://arxiv.org/html/2608.12603
arXiv:2608.12603v1 Announce Type: new
Abstract: Calibrating computational models to experimental data is a core task in applied statistics, especially in scientific domains, where physical experiments are costly and simulations play a central role in design and inference. Motivated by uncertainty quantification challenges in particle accelerator experiments, we develop and evaluate a Hierarchical Bayesian Calibration framework. In contrast to standard Bayesian calibration, certain inputs - such as beam injection amplitude - must be estimated separately for each experiment. We adopt the Kennedy-O'Hagan formulation and extend it with a hierarchical prior structure to model the distribution of experiment-specific calibration parameters, thus borrowing strength and improving generalisation across repeated experiments. A key methodological challenge arises from the need to evaluate a large number of forward simulations, which renders conventional Markov chain Monte Carlo approaches computationally prohibitive. To address this, we leverage the Bayesian Committee Machine as a scalable modelling strategy for Gaussian Process emulators. The BCM provides a principled divide-and-conquer approach, enabling parallel inference and reducing computational cost without requiring problem-specific tuning of the emulator approximation. Posterior sampling is performed using the No-U-Turn Sampler, supported by automatic differentiation in Julia, which removes the need for analytic gradient derivation and facilitates flexible model specification. We assess the proposed framework using established benchmark problems and simulated data from the Argonne Wakefield Accelerator. The results demonstrate substantial computational savings and robust calibration performance, highlighting the applicability of the method to large-scale scientific modelling problems.
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Just finished reading "The Beast Player" by Nahoko Uehashi. I had already watched the anime, but it had been so king I didn't remember all the details. While the anime was great, the book is even better, and it's going to be high on my list of things to recommend to my children when they're old enough to read for fun.
The neurodivergent representation is cool, as is the deep central question of interspecies bonds and the political possibilities and dangers they entail. Uehashi handles the exploration of that question well in my judgment, including appropriate ambiguity without muddying moral clarity. Elin is a truly fantastic protagonist, not without flaws but nevertheless a excellent role model and a very sympathetic figure without being pitiful.
One thing I really love about Uehashi's writing is that she's not shy about using interior narration to tell the reader directly what a variety of characters are feeling, but when she does this she focuses on human contradictions, quirks, and weaknesses that make those characters feel much richer, and that remind the reader of all the ways our weird and sometimes contradictory or inexplicable quirks guide our actions just as much as both logical thought and predictable/expected feelings. None of the characters is an unerring source of wisdom, with every grand principle presented shown to have its weaknesses and biases, and even the wisest characters making mistakes and learning from them.
Overall, a wonderful book, and having also seen the "Seirei no Moribito" anime but not read the books, I'm excited to dig into more of Uehashi's extensive catalog.
#AmReading #ReadingNow #Bookstodon

A Conservative Role Model for Ending the Fertility Crisis (Anemona Hartocollis/New York Times)
https://www.nytimes.com/2026/07/08/us/politics/emma-waters-restorative-reproduction.html
http://www.memeorandum.com/260708/p125#a260708p125

Just finished "Rialto" by Kate Milford. A wonderful book with a *lot* of things to like but also a few I wish had been done differently.
Starting with the good stuff, an #OwnVoices portrayal of anxiety depression is always welcome, *especially* one that portrays positive coping strategies, including active therapy, and complex but ultimately supportive family dynamics. Dad & daughter each reminding each other to use calming strategies at different points in the book was lovely, and getting to see the complexities of the trying to be a supportive sibling was great! Larger than that aspect, portraying a YA adventure in which the parents are actively involved but don't spoil things is so great and must have been difficult to pull off. Most YA stuff quickly ushers the parents out of the picture, and this fails to provide any kind of positive or negative role model for parent/child interaction. This book had ample examples of the former, *and* let the kids have plenty of agency too. Excellent stuff that I absolutely want to see more of.
So what didn't I like?
First, as an anarchist, I always hate to see unapologetically positive (and thus drastically unrealistic) portrayals of the police. Without getting into spoilers, even the stuff about the Piepowder court bothered me. It's presented here as a cutesy alternate court tradition, but I can't help but speculate that these courts were likely not always fair in practice, and the whole "single person makes immediate judgments model" from this book is terrible in general. I just don't like positive portrayals of terrible systems that happen to be good because the people involved are good people, since they reinforce harmful positive mental models of "justice" that don't apply to the real world. This element wasn't enough to totally spoil the book for me (the plot could have mostly functioned without it) but it's a downside to me.
Second, the book is set in rural Missouri, and has plenty of Black characters. Yay for representation? Certainly better than the cast being all-white given the setting. But the book doesn't have any Black *culture* that I picked up on, and it chooses to try to completely sidestep the relevant history. Maybe I'm just not attuned to elements that were there; if anyone who read this did see them feel free to point them out. The history definitely isn't there though... for example, was the park segregated, or not? During the time it was active one imagines most parks would have been, and that if it hadn't been that would have been a very important difference, which would even have been relevant to the plot and themes of the book as written.
Now perhaps this critique is unfair because Black children and young adults *should* get to see themselves portrayed in cozy fantasies without things always having to be about racism... In a choice between erasing Black characters and erasing racism (and especially racist histories) maybe there's no right answer here and this is fine, actually. My instinct tells me that there are ways to do better, though, and that presenting a history with all the racism carefully elided isn't the greatest compromise to make here.
A while ago I read "Under the Heron's Light" by Randi Pink. It also has mythical animal guides, a Southern setting, helpful family members, a multi-generational mystery to solve, and a (slightly older) teen protagonist who is up to the task. In contrast, it is all about racist history, and takes us through multiple extremely harrowing scenes from the past.
In any case, this discomfort also wasn't a deal-breaker for me, in part because, as I said, I think it's probably good for Black children to see uncomplicatedly positive representations of people like them alongside the plenty of stuff out there that does get deep into the racism and history. I also don't have the best perspective to judge this stuff, although that doesn't mean I should default to "it's probably fine" (I'd be happy to hear from anyone who feels they have a better perspective on this, about this book or the trend in general...).
Overall, I enjoyed Rialto quite a lot. I don't think it quite makes it into my top tier of recommendations for my kids, but I think it does make the list somewhere.
#AmReading #ReadingNow #Bookstodon