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Submission Summary: 0 pending, 9 declined, 7 accepted (16 total, 43.75% accepted)

Submission + - Earth is warming faster than previously thought, scientists say, and the window (cnn.com)

JoshuaZ writes:

As the world battles historic droughts, landscape-altering wildfires and deadly floods, a landmark report from global scientists says the window is rapidly closing to cut our reliance on fossil fuels and avoid catastrophic changes that would transform life as we know it.

The state-of-the-science report from the United Nations' Intergovernmental Panel on Climate Change says the world has rapidly warmed 1.1 degrees Celsius higher than pre-industrial levels, and is now careening toward 1.5 degrees — a critical threshold that world leaders agreed warming should remain below to avoid worsening impacts.

Only by making deep cuts to greenhouse gas emissions, while also removing carbon dioxide from the atmosphere, can we halt the precipitous trend.

There is however some good news here. The new IPCC report https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.ipcc.ch%2Fassessment-report%2Far6%2F narrows down the of likely warming. This means it rules out with a high probability the best case scenarios where warming is very small and moderate, but it also shows that some of the worst case scenarios are also unlikely.

Submission + - Sparc compact fusion reactor may be likely to work

JoshuaZ writes: Recent research into the Sparc https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.psfc.mit.edu%2Fsparc fusion reactor design make it seem likely to work. Unlike some other fusion reactor designs, Sparc uses high-temperature superconductors which are capable of much stronger magnetic fields in a more closely confined location. Sparc will be much smaller than large-scale international project ITER https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FITER, which after multiple delays is now not scheduled to even start fusion reactions by 2035 at the earliest. The Sparc researchers hope that their reactor design will be completed soon enough to have an impact on climate change. The new research on Sparc consists of seven different papers https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.cambridge.org%2Fcore%2Fjournals%2Fjournal-of-plasma-physics%2Fcollections%2Fstatus-of-the-sparc-physics-basis all of which have favorable estimates for the likelihood of the project succeeding. Some physicists, including Cary Forest, at the University of Wisconsin, were more skeptical. Forest told the New York Times https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.nytimes.com%2F2020%2F09%2F29%2Fclimate%2Fnuclear-fusion-reactor.html> that Sparc's estimates for when their reactor would be ready were probably off by at least a factor of two.

Submission + - All Dreamwidth links blocked on Facebook; silent deletion of existing links (dreamwidth.org)

JoshuaZ writes: Andrew Drucker has reported https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fandrewducker.dreamwidth.org%2F3861716.html that Facebook has apparently blocked all links to Dreamwidth, a semi-popular blogging/journaling platform with tens of thousands of users. Facebook is not only preventing anyone from posting it, they've also silently deleted all statuses, posts, and replies which have included even a single Dreamwidth links. As of right now, the reason for this is unknown. This may be an overzealous spam filter at work.

Submission + - Major breakthrough in quantum computing shows that MIP* = RE

JoshuaZ writes: In a major breakthrough in quantum computing it was shown that MIP* equals RE https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Farxiv.org%2Fabs%2F2001.04383. MIP* is the set of problems that can be efficiently demonstrated to a classical computer interacting with multiple quantum computers with any amount of shared entanglement between the quantum computers. RE is the set of problems which are recursive; this is essentially all problems which can be computed.

This result comes through years of deep development of understanding interactive protocols, where one entity, a verifier, has much less computing power than another set of entities, provers, who wish to convince the verifier of the truth of a claim. In 1990, a major result was that a classical computer with a polynomial amount of time could be convince of any claim in PSPACE https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPSPACE by interacting with an arbitrarily powerful classical computer. https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FIP_(complexity). Here PSPACE is the set of problems solvable by a classical computer with a polynomial amount of space. Subsequent results showed that if one allowed a verifier able to interact with multiple provers, the verifier could be convinced of a solution of any problem in NEXPTIME, a class conjectured to be much larger than PSPACE. For a while, it was believed that in the quantum case, the set of problems might actually be smaller, since multiple quantum computers might be able to use their shared entangled qubits to "cheat" the verifier. However, this has turned out not just to not be the case, but the exact opposite: MIP* is not only large, it is about as large as a computable class can naturally be.

This result while a very big deal from a theoretical standpoint is unlikely to have any immediate applications since it supposes quantum computers with arbitrarily large amounts of computational power and infinite amounts of entanglement.

The paper in question is a 165 tour de force which includes incidentally showing that the The Connes embedding conjecture, a 50 year old major conjecture from the theory of operator algebras, is false.

Submission + - Breakthrough algorithm reported for graph isomorphsim

JoshuaZ writes: A major open problem in graph theory is how efficiently one can tell given two graphs whether or not they are isomorphic, that is, the same graph with just the labels changed. This problem is famous along with factoring integers as a problem that is potentially in between P and NP in difficulty. Now, Laszlo Babai has reported that he has a quasipolynomial time algorithm which he sketched out at a set of talks at the University of Chicago http://www.math.uchicago.edu/calendar?calendar=Combinatorics%20and%20Theoretical%20Computer%20Science. Scott Aaronson was one of the first to break the news and his latest blog entry and its comments contains further discussion of the result http://www.scottaaronson.com/blog/?p=2521. The new algorithm places the problem of graph isomorphism as at most just barely above P. Babai's result depends on the classification of finite simple groups https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FClassification_of_finite_simple_groups a deep result in algebra whose proof consists of thousands of pages over hundreds of distinct papers. Unlike the problem of factoring integers, improvements in this algorithm are unlikely to impact cryptography in any direct way since no cryptographic systems depend on the difficulty of determining when groups are isomorphic.

Submission + - Scientists identify possible new substance with highest melting point

JoshuaZ writes: "Researchers from Brown University have tentatively identified an alloy of hafnium, nitrogen and carbon as having an expected melting point of about 7,460 degrees Fahrenheit (4120 Celsius). This exceeds the previous record breaker tantalum hafnium carbide which melts at 7,128 F (3942 C) and had stood as the record holder for almost a century. However, at this point, the record setter is still hypothetical, based on simulations. The new record has not yet been confirmed by experiment. http://journals.aps.org/prb/abstract/10.1103/PhysRevB.92.020104 is the actual article while http://www.washingtonpost.com/news/speaking-of-science/wp/2015/07/28/behold-a-new-record-for-the-worlds-highest-melting-point/ is a lay summary. If the simulations turn out to be correct, the new alloy may be useful in parts like jet engines, and the door will be opened to using similar simulations to search for substances with even higher melting points or with other exotic properties.

Submission + - Astronomers find star that doesn't fit (sciencedaily.com)

JoshuaZ writes: "Astronomers have found an unusual small star. SDSS J102915+172927 is a small faint star with very little of any elements other than hydrogen or helium. The star's composition is surprising since standard theories of star formation require heavier elements in small stars in order to allow the stars to be heavy enough to come together. Possibly the most unusual aspect of this star is the complete non-detection of lithium which would be expected in a star of this size. The only elements created shortly after the Big Bang were lithium, hydrogen and helium, and the star should have lithium levels much higher since they should correspond closely with the levels believed to have been formed shortly after the Big Bang. The actual paper can be found at http://www.eso.org/public/archives/releases/sciencepapers/eso1132/eso1132.pdf."

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