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Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences

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https://www.readbyqxmd.com/read/28923999/mass-loss-and-stellar-superwinds
#1
REVIEW
Jorick S Vink
Mass loss bridges the gap between massive stars and supernovae (SNe) in two major ways: (i) theoretically, it is the amount of mass lost that determines the mass of the star prior to explosion and (ii) observations of the circumstellar material around SNe may teach us the type of progenitor that made the SN. Here, I present the latest models and observations of mass loss from massive stars, both for canonical massive O stars, as well as very massive stars that show Wolf-Rayet type features.This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'...
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28923998/luminous-blue-variables-and-the-fates-of-very-massive-stars
#2
REVIEW
Nathan Smith
Luminous blue variables (LBVs) had long been considered massive stars in transition to the Wolf-Rayet (WR) phase, so their identification as progenitors of some peculiar supernovae (SNe) was surprising. More recently, environment statistics of LBVs show that most of them cannot be in transition to the WR phase after all, because LBVs are more isolated than allowed in this scenario. Additionally, the high-mass H shells around luminous SNe IIn require that some very massive stars above 40 M⊙ die without shedding their H envelopes, and the precursor outbursts are a challenge for understanding the final burning sequences leading to core collapse...
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28923997/the-evolution-of-massive-stars-bridging-the-gap-in-the-local-group
#3
REVIEW
Philip Massey, Kathryn F Neugent, Emily M Levesque
The nearby galaxies of the Local Group can act as our laboratories in helping to bridge the gap between theory and observations. In this review, we will describe the complications of identifying samples of OB stars, yellow and red supergiants, and Wolf-Rayet stars, and what we have so far learned from these studies.This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'.
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28923996/predicting-the-nature-of-supernova-progenitors
#4
REVIEW
Jose H Groh
Stars more massive than about 8 solar masses end their lives as a supernova (SN), an event of fundamental importance Universe-wide. The physical properties of massive stars before the SN event are very uncertain, both from theoretical and observational perspectives. In this article, I briefly review recent efforts to predict the nature of stars before death, in particular, by performing coupled stellar evolution and atmosphere modelling of single stars in the pre-SN stage. These models are able to predict the high-resolution spectrum and broadband photometry, which can then be directly compared with the observations of core-collapse SN progenitors...
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28923995/bridging-the-gap-from-massive-stars-to-supernovae
#5
Justyn R Maund, Paul A Crowther, Hans-Thomas Janka, Norbert Langer
Almost since the beginning, massive stars and their resultant supernovae have played a crucial role in the Universe. These objects produce tremendous amounts of energy and new, heavy elements that enrich galaxies, encourage new stars to form and sculpt the shapes of galaxies that we see today. The end of millions of years of massive star evolution and the beginning of hundreds or thousands of years of supernova evolution are separated by a matter of a few seconds, in which some of the most extreme physics found in the Universe causes the explosive and terminal disruption of the star...
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28923994/the-direct-identification-of-core-collapse-supernova-progenitors
#6
REVIEW
Schuyler D Van Dyk
To place core-collapse supernovae (SNe) in context with the evolution of massive stars, it is necessary to determine their stellar origins. I describe the direct identification of SN progenitors in existing pre-explosion images, particularly those obtained through serendipitous imaging of nearby galaxies by the Hubble Space Telescope I comment on specific cases representing the various core-collapse SN types. Establishing the astrometric coincidence of a SN with its putative progenitor is relatively straightforward...
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28923993/spectropolarimetry-of-stripped-envelope-supernovae-observations-and-modelling
#7
Masaomi Tanaka
Spectropolarimetry is one of the most powerful methods to study the multi-dimensional geometry of supernovae (SNe). We present a brief summary of the spectropolarimetric observations of stripped-envelope core-collapse SNe. Observations indicate that stripped-envelope SNe generally have a non-axisymmetric ion distribution in the ejecta. Three-dimensional clumpy geometry nicely explains the observed properties. A typical size of the clumps deduced from observations is relatively large: [Formula: see text]25% of the photosphere...
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28923992/the-mechanism-s-of-core-collapse-supernovae
#8
REVIEW
Sean M Couch
Core-collapse supernovae (CCSNe) are the explosions that attend the deaths of massive stars. Despite decades of research, several aspects of the mechanism that drives these explosions remain uncertain and the subjects of continued investigation. In this short review, I will give an overview of the CCSN mechanism and current research in the field. In particular, I will focus on recent results from three-dimensional simulations and the impact of turbulence and detailed non-spherical progenitor structure on CCSNe...
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28923991/red-supergiants-as-supernova-progenitors
#9
REVIEW
Ben Davies
It is now well-established from pre-explosion imaging that red supergiants (RSGs) are the direct progenitors of Type-IIP supernovae. These images have been used to infer the physical properties of the exploding stars, yielding some surprising results. In particular, the differences between the observed and predicted mass spectrum has provided a challenge to our view of stellar evolutionary theory. However, turning what is typically a small number of pre-explosion photometric points into the physical quantities of stellar luminosity and mass requires a number of assumptions about the spectral appearance of RSGs, as well as their evolution in the last few years of life...
October 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28871056/position-paper-the-science-of-deep-specification
#10
Andrew W Appel, Lennart Beringer, Adam Chlipala, Benjamin C Pierce, Zhong Shao, Stephanie Weirich, Steve Zdancewic
We introduce our efforts within the project 'The science of deep specification' to work out the key formal underpinnings of industrial-scale formal specifications of software and hardware components, anticipating a world where large verified systems are routinely built out of smaller verified components that are also used by many other projects. We identify an important class of specification that has already been used in a few experiments that connect strong component-correctness theorems across the work of different teams...
October 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28871055/verified-trustworthy-software-systems
#11
Philippa Gardner
No abstract text is available yet for this article.
October 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28871054/compositional-relaxed-concurrency
#12
Mark Batty
There is a broad design space for concurrent computer processors: they can be optimized for low power, low latency or high throughput. This freedom to tune each processor design to its niche has led to an increasing diversity of machines, from powerful pocketable devices to those responsible for complex and critical tasks, such as car guidance systems. Given this context, academic concurrency research sounds notes of both caution and optimism. Caution because recent work has uncovered flaws in the way we explain the subtle memory behaviour of concurrent systems: specifications have been shown to be incorrect, leading to bugs throughout the many layers of the system...
October 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28871053/provably-trustworthy-systems
#13
Gerwin Klein, June Andronick, Gabriele Keller, Daniel Matichuk, Toby Murray, Liam O'Connor
We present recent work on building and scaling trustworthy systems with formal, machine-checkable proof from the ground up, including the operating system kernel, at the level of binary machine code. We first give a brief overview of the seL4 microkernel verification and how it can be used to build verified systems. We then show two complementary techniques for scaling these methods to larger systems: proof engineering, to estimate verification effort; and code/proof co-generation, for scalable development of provably trustworthy applications...
October 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28871052/program-synthesis-challenges-and-opportunities
#14
REVIEW
Cristina David, Daniel Kroening
Program synthesis is the mechanized construction of software, dubbed 'self-writing code'. Synthesis tools relieve the programmer from thinking about how the problem is to be solved; instead, the programmer only provides a description of what is to be achieved. Given a specification of what the program should do, the synthesizer generates an implementation that provably satisfies this specification. From a logical point of view, a program synthesizer is a solver for second-order existential logic. Owing to the expressiveness of second-order logic, program synthesis has an extremely broad range of applications...
October 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28871051/formal-verification-will-the-seedling-ever-flower
#15
Neil White, Stuart Matthews, Roderick Chapman
In one sense, formal specification and verification have been highly successful: techniques have been developed in pioneering academic research, transferred to software companies through training and partnerships, and successfully deployed in systems with national significance. Altran UK has been in the vanguard of this movement. This paper summarizes some of our key deployments of formal techniques over the past 20 years, including both security- and safety-critical systems. The impact of formal techniques, however, remains within an industrial niche, and while government and suppliers across industry search for solutions to the problems of poor-quality software, the wider software industry remains resistant to adoption of this proven solution...
October 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28871050/the-hacms-program-using-formal-methods-to-eliminate-exploitable-bugs
#16
Kathleen Fisher, John Launchbury, Raymond Richards
For decades, formal methods have offered the promise of verified software that does not have exploitable bugs. Until recently, however, it has not been possible to verify software of sufficient complexity to be useful. Recently, that situation has changed. SeL4 is an open-source operating system microkernel efficient enough to be used in a wide range of practical applications. Its designers proved it to be fully functionally correct, ensuring the absence of buffer overflows, null pointer exceptions, use-after-free errors, etc...
October 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28871049/industrial-hardware-and-software-verification-with-acl2
#17
Warren A Hunt, Matt Kaufmann, J Strother Moore, Anna Slobodova
The ACL2 theorem prover has seen sustained industrial use since the mid-1990s. Companies that have used ACL2 regularly include AMD, Centaur Technology, IBM, Intel, Kestrel Institute, Motorola/Freescale, Oracle and Rockwell Collins. This paper introduces ACL2 and focuses on how and why ACL2 is used in industry. ACL2 is well-suited to its industrial application to numerous software and hardware systems, because it is an integrated programming/proof environment supporting a subset of the ANSI standard Common Lisp programming language...
October 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28827428/from-slow-to-fast-faulting-recent-challenges-in-earthquake-fault-mechanics
#18
S Nielsen
Faults-thin zones of highly localized shear deformation in the Earth-accommodate strain on a momentous range of dimensions (millimetres to hundreds of kilometres for major plate boundaries) and of time intervals (from fractions of seconds during earthquake slip, to years of slow, aseismic slip and millions of years of intermittent activity). Traditionally, brittle faults have been distinguished from shear zones which deform by crystal plasticity (e.g. mylonites). However such brittle/plastic distinction becomes blurred when considering (i) deep earthquakes that happen under conditions of pressure and temperature where minerals are clearly in the plastic deformation regime (a clue for seismologists over several decades) and (ii) the extreme dynamic stress drop occurring during seismic slip acceleration on faults, requiring efficient weakening mechanisms...
September 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28827427/heating-weakening-and-shear-localization-in-earthquake-rupture
#19
REVIEW
James R Rice
Field and borehole observations of active earthquake fault zones show that shear is often localized to principal deforming zones of order 0.1-10 mm width. This paper addresses how frictional heating in rapid slip weakens faults dramatically, relative to their static frictional strength, and promotes such intense localization. Pronounced weakening occurs even on dry rock-on-rock surfaces, due to flash heating effects, at slip rates above approximately 0.1 m s(-1) (earthquake slip rates are typically of the order of 1 m s(-1))...
September 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28827426/phase-transformation-induced-lubrication-of-earthquake-sliding
#20
Harry W Green
Frictional failure is not possible at depth in Earth, hence earthquakes deeper than 30-50 km cannot initiate by overcoming dry friction. Moreover, the frequency distribution of earthquakes with depth is bimodal, suggesting another change of mechanism at about 350 km. Here I suggest that the change at 30-50 km is from overcoming dry friction to reduction of effective stress by dehydration embrittlement and that the change at 350 km is due to desiccation of slabs and initiation by phase-transformation-induced faulting...
September 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
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