Walter Pitts and Neural Nets

Pitts is one of the least studied geniuses of the early information age. See also Wikipedia, Nautil.us. Cabinet Magazine: There are no biographies of Walter Pitts, and any honest discussion of him resists conventional biography. Pitts was among the original participants in the mid-century cybernetics conferences, though he began his association with that group of …

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Baby Universes in the Laboratory

This was on the new books table at our local bookstore. I had almost forgotten about doing an interview and corresponding with the author some time ago. See also here and here. The book is a well-written overview of some of the more theoretical aspects of inflationary cosmology, the big bang, the multiverse, etc. It also …

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Oppenheimer on Bohr (1964 UCLA)

Oppenheimer on Bohr (1964 UCLA) I came across this 1964 UCLA talk by Oppenheimer, on his hero Niels Bohr. Oppenheimer: Mathematics is “an immense enlargement of language, an ability to talk about things which in words would be simply inaccessible.” I find it strange that psychometricians usually define “verbal ability” over a vocabulary set that …

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Are quanta particles or waves?

Are quanta particles or waves? The title of this post is an age-old question isn’t it? Particle or wave? Wave or particle? Many have rightly argued that the so-called “wave-particle duality” is at the very heart of quantum weirdness, and hence, of all of quantum mechanics. Einstein said it. Bohr said it. Feynman said it. …

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Varieties of Time Travel

My kids have been reading lots of books over the break, including an adventure series that involves time travel. Knowing vaguely that dad is a theoretical physicist, they asked me how time travel works. 1. Can one change history by influencing past events? OR 2. Is there only one timeline that cannot be altered, even …

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Time and Memory

Over the holiday I started digging through my mom’s old albums and boxes of photos. I found some pictures I didn’t know existed! Richard Feynman and the 19 year old me at my Caltech graduation: With my mom that morning — hung-over, but very happy! I think those are some crazy old school Ray Bans …

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Three Lectures on AdS/CFT

MSU postdoc Steve Avery explains AdS/CFT to non-specialists (i.e., theoretical physicists who do not primarily work on string theory / quantum gravity). Steve is applying for faculty positions this fall — hire him! :-) AdS/CFT on this blog. See also Entanglement and fast thermalization in heavy ion collisions: application of AdS/CFT to collisions of heavy ions …

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Theory, Money, and Learning

After 25+ years in theoretical physics research, the pattern has become familiar to me. Talented postdoc has difficulty finding a permanent position (professorship), and ends up leaving the field for finance or Silicon Valley. The final phase of the physics career entails study of entirely new subjects, such as finance theory or machine learning, and developing …

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Gell-Mann on quantum foundations

Google knows enough about me that my YouTube feed now routinely suggests content of real interest. A creepy but positive development ;-) Today YouTube suggested this video of Murray Gell-Mann talking about Everett, decoherence, and quantum mechanics. I had seen this video on another web site years ago and blogged about it (post reproduced below), …

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The story of the Monte Carlo Algorithm

George Dyson is Freeman’s son. I believe this talk was given at SciFoo or Foo Camp. More Ulam (neither he nor von Neumann were really logicians, at least not primarily). Wikipedia on Monte Carlo Methods. I first learned these in Caltech’s Physics 129: Mathematical Methods, which used the textbook by Mathews and Walker. This book was …

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EPR and Bell for pedestrians

My old friend Mark Alford (WUSTL) was on campus last week for the inaugural meeting of the FRIB-TA (Facility for Rare Ion Beams Theory Alliance). Over beers he told me he had come up with a pedagogical way to explain Bell’s inequality in a single picture. Here it is. Ghostly action at a distance: a …

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Moore’s Law and AI

By now you’ve probably heard that Moore’s Law is really dead. So dead that the semiconductor industry roadmap for keeping it on track has more or less been abandoned: see, e.g., here, here or here. (Reported on this blog 2 years ago!) What I have not yet seen discussed is how a significantly reduced rate …

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LIGO detects gravity waves

Live-blogging the LIGO announcement of detection of gravity waves. Detection of an event in 2015 (initial science run of advanced LIGO) is good news for the future use of gravity waves as an astrophysical probe — it suggests a fairly high density of NS-NS, NS-BH, and BH-BH binaries in the universe. Each time astronomers have …

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Black Hole Memory and Soft Hair

A recent paper by Hawking, Perry, and Strominger (Soft Hair on Black Holes) proposes a new kind of soft hair (i.e., soft gravitons or photons) on the black hole horizon. This hair is related to recent results on BMS symmetries and soft (zero) modes by Strominger and collaborators. The existence of an infinite number of …

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Feynman’s War

Radar and nuclear weapons could not have been developed without the big brains. Feynman’s War: Modelling Weapons, Modelling Nature Peter Galison* What do I mean by understanding? Nothing deep or accurate—just to be able to see some of the qualitative consequences of the equations by some method other than solving them in detail. — Feynman …

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SOAR

The visit of SOAR was not on our original itinerary, but I asked to visit and my wish was granted (thanks Tim Spuck!). SOAR is just a jaunt down the road from Gemini on the same peak of Cerro Pachon. The reason I wanted to go was because my employer, the Physics-Astronomy department at MSU is one …

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What is medicine’s 5 sigma?

Editorial in the Lancet, reflecting on the Symposium on the Reproducibility and Reliability of Biomedical Research held April 2015 by the Wellcome Trust. Offline: What is medicine’s 5 sigma? … much of the [BIOMEDICAL] scientific literature, perhaps half, may simply be untrue. Afflicted by studies with small sample sizes, tiny effects, invalid exploratory analyses, and …

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Technically Sweet

Regular readers will know that I’ve been interested in the so-called Teller-Ulam mechanism used in thermonuclear bombs. Recently I read Kenneth Ford‘s memoir Building the H Bomb: A Personal History. Ford was a student of John Wheeler, who brought him to Los Alamos to work on the H-bomb project. This led me to look again …

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Schwinger meets Rabi

Seventeen year old Julian Schwinger meets Columbia professor I. I. Rabi (Nobel Prize 1944) and explains the EPR paper to him. Climbing the Mountain: The Scientific Biography of Julian Schwinger [p.22-23] … Rabi appeared; he invited Motz into his office to discuss ‘a certain paper by Einstein in the Physical Review’! Motz introduced Julian and …

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Hopfield on physics and biology

Theoretical physicist John Hopfield, inventor of the Hopfield neural network, on the differences between physics and biology. Hopfield migrated into biology after making important contributions in condensed matter theory. At Caltech, Hopfield co-taught a famous course with Carver Mead and Richard Feynman on the physics of computation. Two cultures? Experiences at the physics-biology interface (Phys. …

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Astrophysical Repulsion from Dark Energy

The manifestation of dark energy on cosmological scales is well known: gravitational repulsion which leads to the accelerating expansion of the universe. Perhaps surprisingly, there are potentially observable effects on galactic length scales as well. The Dark Force: Astrophysical Repulsion from Dark Energy (http://arxiv.org/abs/1501.05952) Chiu Man Ho, Stephen D. H. Hsu Dark energy (i.e., a cosmological …

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Instability of Quantum de Sitter Spacetime

New paper! We show that quantum effects (in particular, the horizon temperature originally discovered by Gibbons and Hawking) modify the geometry of de Sitter spacetime. Instability of Quantum de Sitter Spacetime (http://arxiv.org/abs/1501.00708) Chiu Man Ho, Stephen D. H. Hsu Quantized fields (e.g., the graviton itself) in de Sitter (dS) spacetime lead to particle production: specifically, …

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Quantum GDP

  “It’s been only half jokingly said that today a third of GDP is attributable to quantum mechanics,” — former Lockheed CEO Norm Augustine. I’ve heard the one third or 30% of GDP figure from time to time, but have never seen a detailed analysis. A list of modern technologies that arose from quantum mechanics …

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Feynman Lectures: Epilogue

The full text of The Feynman Lectures is now available online. These lectures were originally delivered to satisfy the physics requirement for first and second year students at Caltech. Legend has it that as the lectures went on, fewer and fewer undergraduates were seen in attendance, with their places taken by graduate students and even members …

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Wandering physicists

This is funny, and does capture the tendency of physicists (not just old ones) to wander into other fields. But the cartoon avoids the hard question (perhaps best addressed by historians of science) as to the actual value brought to other fields by physicists. See, for example, Physicists can do stuff, Prometheus in the basement, …

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Nifty papers I wrote that nobody knows about (Part 4: Complex Langevin equation)

This is the last installment of the “Nifty Papers” series. Here are the links to Part1, Part2, and Part 3. For those outside the computational physics community, the following words don’t mean anything: “The Sign Problem“ For those others that have encountered the problem, these words elicit terror. They stand for sleepless nights. They spell despair. They make grown men …

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Nifty papers I wrote that nobody knows about: (Part 3: Non-equilibrium Quantum Statistical Mechanics)

This is the third part of the “Nifty Papers” series. Link to Part 1. Link to Part 2. In 1999, I was in the middle of writing about quantum information theory with my colleague Nicolas Cerf. We had discovered that quantum conditional entropy can be negative, discussed this finding with respect to the problem of quantum measurement, separability, Bell inequalities, as well …

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Physicists Create Water Tractor Beam

A group of physicists have discovered that they can make objects move against the direction of waves by using a tractor beam on water, which generates waves. This has important real-world applications, including confining oil spills. The physicists do not yet know mathematical theories explaining how it works.  Dr. Horst Punzmann said ” . . …

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HKUST IAS

I have a new candidate for coolest research institute architecture. HKUST’s Institute for Advanced Study is housed in an amazing building with a view of Clearwater Bay in HK. The members of the institute will be mostly theoretical physicists and mathematicians :-) Stiff competition from Benasque’s Center and the Perimeter Institute, however. Also Caltech’s IQIM! …

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