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Nature tidbits [23 October 2025]

Posted in Books, Kids, pictures, Running, Travel, University life with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on November 27, 2025 by xi'an

In this October issue of nature, plenty of the “usual” topics, namely AI and Trump.2.0 wrecking balls, along with two cosmology entries that related to my trip to the early universe last week, and a pros-and-cons opposition about animal testing,

a discussion on the nature of the “little red dots” that have been recently observed and whose nature remains open, the most popular explanation (I was given during lunch) being black holes surrounded by gas (even though I cannot understand why the gas is not attracted by the black hole!) [and would have produced a more exciting cover!]

a review of the recent book Discordance: The Troubled History of the Hubble Constant by Jim Baggott, entitled Why we still don’t understand the Universe — even after a century of dispute! A review that regrets that more time is spent on the Hubble “constant” (which varies with time!) rather than more controversial issues like dark matter and dark energy (And strangely bemoans that the book is focussed on scientific developments, missing sociological ones. Duh?! (Bonus for a picture of suit-and-tie Edwin Hubble sitting at the centre of a telescope),

two entries on the well-being [or lack thereof] of PhD students, with nothing particularly surprising (eg, inclusivity and respect help!), and Brazil, Australia and Italy ranking top locations but in a comparative study that does not mention France (as often in international comparisons found in Nature) despite the place being in the top 10 countries delivering PhD degrees, not that I believe PhD students are particularly well-treated in French academia!, the (unexplained) surprise being Italy ranking so high given the close resemblance between the two countries (low stipends, shortage of postdoc and permanent positions, high teaching loads for the advisor, limited travel budgets),

a conference (purposedly) made of AI-written papers reviewed by AI referees, Agents4Science 2025, how universities are rushed into adapting to AI-fluent students, whose skills are changing, and the rise in fake authors produced by paper mills, with a limited range of acceptable solutions,

why Trump 2.0‘s blackmail on pharmaceutical companies is counter-productive and likely to slow down progress, and why his massive increase of highly qualified scientists is shooting (or nuking) USelf in the foot, given the huge proportion) of im/emigrated Nobel prize winners (for physics, chemistry, and medicine), along the (post-) Nobel prize in economics is a direct or indirect reply to this regression by awarding the Prize to economists who worked on the importance of creativity and science on growth (not very surprising at first look!)

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Nature tidbits [30th October 2025]

Posted in Books, Kids, pictures, Running, Travel, University life with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on November 22, 2025 by xi'an

In this October issue of nature, items of interest (to me) [already highlighted in an emailed News Highlight]:

Google claim a significant ‘quantum advantage’ by quantum-echoes algorithms that they say is 13,000 faster than classical algorithms, but it is unclear from the nature article where and when their algorithms can be used, apparently missing to apply to realistic scientific applications… (Along with a paper on an “atom-array architecture that enables continuous operation with reloading rates of up to 30,000 initialized qubits per second while preserving coherence across a rearranged large-scale qubit array”.)

On the Trump vs. Science scene, a predicted drop in PhD admissions as an adaptation to (uncertain) Trump’s cuts, bans, visa restrictions, and other attempts at arm-bending and blackmailing  (And the novelty of me receiving applications from the US, a first!) Some U.S. departments have simply cancelled PhD admissions… But some universities have so far resisted the Orange pressure. Namely, the MIT, Brown University, (good old) Penn, UCLA, the University of Virginia (albeit agreeing to a deal), Dartmouth College, and the University of Arizona in Tucson. Vanderbilt has given in. (UT Austin and Harvard seem to be continuing the discussion with the Trump administration.) Meanwhile, China is zooming past! The issue also contains articles on how fundamental science discoveries have had hugely practical consequences, in case one need argue with a sceptic.

As a less urgent issue, some researchers at Institut Pasteur in Paris identified new diseases that did not help Napoléon’s Grande Armée as it retreated from Moscow, from the DNA of 13 soldiers buried in Lithuania. (With nature failing to give credit to the painter Adolph Northen for his famous “Napoleon’s retreat from Moscow” illustrating the story, attributed to the researchers in the paper!)

In this period of ERC announcements of their grantees, an analysis of the two-digit rise in applications. Unsurprising, given the international context. Along with a decrease in funding due to a lack of adjustment against inflation since 2007. (Incidentally, I found out this week that Torsten Elßin—at the Max Planck Institute for Astrophysics—I visited once had been selected for a Synergy grant on a 3D Milky Way Atlas. Along another cosmology Synergy grant at MPA on the Epoch of Reionization.)

A runner’s must-read that starts with the statement “the human body has a ‘metabolic ceiling’ that even the most extreme athletes cannot surpass”. Which would be 2.4 times the basal metabolic rate (BMR) for extended periods—by which the authors mean 30 weeks and over!, not a half-marathon. Not so exciting a paper in the end.

As predicted by the cover, a Royal Society meeting acknowledging the AI language models killed Turing’ test and questioning the next one. Since assessing the capacities and limitations of novel AIs and AGIs sounds more relevant and societally important. To wit, “;the Turing test of the future should question whether an AI is safe, reliable and provides meaningful benefit, he said, and should also ask who bears the cost of that benefit”. (As discussed in the book review of The Means of Prediction: How AI Really Works (and Who Benefits) by Maximilian Kasy, in the same volume. And yet another paper on AI biases.)

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the Harvard and Brown school of computer science

Posted in Books, Statistics, Travel, University life with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on October 2, 2025 by xi'an

 “In the late 1980s, LeCun, then a researcher at AT&T Bell Labs, developed a powerful neural network that learned to recognise handwritten zip codes by training on thousands of examples. A parallel development soon unfolded at Harvard and Brown. In 1995, Zhu and a team of researchers there started developing probability-based methods that could learn to recognise patterns and textures (…) and even generate new examples of that pattern. These were not neural networks: members of the “Harvard-Brown school”, as Zhu called his team, cast vision as a problem of statistics and relied on methods such as “Bayesian inference” and “Markov random fields”. The two schools spoke different mathematical languages and had philosophical disagreements. But they shared an underlying logic – that data, rather than hand-coded instructions, could supply the infrastructure for machines to grasp the world and reproduce its patterns – that exists in today’s AI systems such as ChatGPT.” 

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how the election result could affect scientists and science policy

Posted in Books, Kids, Travel, University life with tags , , , , , , , , , , on November 28, 2024 by xi'an

Nature of 08 November 2024 has an article on the consequences of the dreadful election of Donald Trump on AI,

[Trump] promised to repeal US President Joe Biden’s executive order on AI, a guideline released last year for developing the technology safely and responsibly. Trump’s pledge echoes the Republican party’s platform, which says that the executive order “hinders AI Innovation” (…) “The emphasis will shift away from the regulatory environment” and towards technology companies making their own voluntary decisions on safety,” says Suresh Venkatasubramanian, director of the CNTR at Brown University.

on climate,

it will not be easy to undo Biden’s signature climate achievement: the 2022 Inflation Reduction Act (…) Trump could have a bigger — and more negative — impact on climate progress if he moves to weaken climate regulations (…) increases the cost of clean-energy technologies (…) [and] pulls the United States out of the 2015 Paris agreement,

on health.

Trump has said that he will let Kennedy, who has questioned the effectiveness of vaccines, “go wild on” health (…) [and the US] support for global health is also likely to be “greatly scaled back” during Trump’s second term.

and on science in general

it’s unclear whether the second Trump administration will revive the China Initiative, although the House of Representatives advanced legislation in September that would do so. But a reinstatement of the travel ban [for half a dozen countries] is likely (…) [and] will make it harder for new scientific collaborations to arise

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stratified MCMC

Posted in Books, pictures, Statistics with tags , , , , , , , , , , , , on December 3, 2020 by xi'an

When working last week with a student, we came across [the slides of a talk at ICERM by Brian van Koten about] a stratified MCMC method whose core idea is to solve a eigenvector equation z’=z’F associated with the masses of “partition” functions Ψ evaluated at the target. (The arXived paper is also available since 2017 but I did not check it in more details.)Although the “partition” functions need to overlap for the matrix not to be diagonal (actually the only case that does not work is when these functions are truly indicator functions). As in other forms of stratified sampling, the practical difficulty is in picking the functions Ψ so that the evaluation of the terms of the matrix F is not overly impacted by the Monte Carlo error. If spending too much time in estimating these terms, there is not a clear gain in switching to stratified sampling, which may be why it is not particularly developed in the MCMC literature….

As an interesting aside, the illustration in this talk comes from the Mexican stamp thickness data I also used in my earlier mixture papers, concerning the 1872 Hidalgo issue that was printed on different qualities of paper. This makes the number k of components somewhat uncertain, although k=3 is sometimes used as a default. Hence a parameter and simulation space of dimension 8, even though the method is used toward approximating the marginal posteriors on the weights λ¹ and λ².

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