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Grand challenges in low-temperature plasma physics  [PDF]
Christine Charles
Frontiers in Physics , 2014, DOI: 10.3389/fphy.2014.00039
Abstract: 1. INTRODUCTION A plasma is a hot ionized gas and classification of this fourth state of matter can be initially done using the basic concept of temperature. A prime example is the Sun which exhibits a very hot plasma in its core with temperatures of about 1.5x107 K (a result of fusion reactions with a proton density of ~1026 cm-3) and cooler surface temperatures of about 6000 K (Parker, 1997): the Solar wind originates from the Solar Corona, expands into the universe and impacts the Earth’ magnetosphere and ionosphere, the two plasma layers surrounding Earth’s gaseous atmosphere. Aurorae in the Northern and Southern skies near the magnetic poles are examples of this interaction. The electron density in the ionosphere is low (104-106 cm-3) and the background neutral gas density is also low (about 108 cm-3 or 3x109 Torr at 300 km altitude) approaching the ‘space-like’ environment created in laboratories to develop and test hardware for space use (i.e. satellites and payloads). At the surface of the Earth lightning strikes of a storm are naturally occurring plasmas operating near atmospheric pressure (neutral density of about 2x1019cm-3) with large electron densities (about 1015-1017 cm-3) characteristic of streamers, arcs and filamentary discharges. The temperatures and densities of neutral and charged particles are critical parameters affecting the physical mechanisms within the plasma such as particle transport and collisional processes (Lowke, 2013) and their range spans many orders of magnitude, opening doors to an extremely wide range of plasma applications. Plasmas in which fusion reactions take place are often referred to as ‘hot’ plasmas. The high-temperature plasma community has a well defined aim of triggering and controlling fusion plasmas (as can be found in the Sun’s core) for energy production, with various worldwide large scale programs or experiments in place (i.e. the International Thermonuclear Experimental Reactor ITER, the National Ignition Facility ICF…) [Pfalzner, 2006]. Hot plasmas in space also include relativistic plasmas (highest electron temperatures) and quantum plasmas (highest electron densities). All other plasmas are classified as low-temperature or ‘cold’ plasmas: those gaseous plasmas or electrical discharges have been successfully harnessed and studied in the laboratory since the 1920s and in space using satellites since the 1960s. The latter two plasma examples essentially sit at the opposite ends of the ‘cold’ plasma spectrum. The wide range of available plasma parameters has largely contributed to the long and
Grand challenges in computational physics  [PDF]
Christian Klingenberg
Frontiers in Physics , 2013, DOI: 10.3389/fphy.2013.00002
Grand challenges in biomedical physics  [PDF]
David Townsend,Zhen Cheng,Dietmar Georg,Wolfgang Drexler,Ewald Moser
Frontiers in Physics , 2013, DOI: 10.3389/fphy.2013.00001
Grand challenges in computational physics  [PDF]
Kay Hamacher
Frontiers in Physics , 2013, DOI: 10.3389/fphy.2013.00004
Grand challenges in mathematical physics  [PDF]
Emilio Elizalde
Frontiers in Physics , 2013, DOI: 10.3389/fphy.2013.00009
Grand challenges in interdisciplinary physics  [PDF]
Alex Hansen
Frontiers in Physics , 2014, DOI: 10.3389/fphy.2014.00058
Two-dimensional models of early-type fast rotating stars: new challenges in stellar physics  [PDF]
Michel Rieutord,Francisco Espinosa Lara
Physics , 2013, DOI: 10.1051/eas/1363043
Abstract: Two-dimensional models of rapidly rotating stars are already unavoidable for the interpretation of interferometric or asteroseismic data of this kind of stars. When combined with time evolution, they will allow the including of a more accurate physics for the computation of element transport and the determination of surface abundances. In addition, modeling the evolution of rotation will improve gyrochronology. Presently, two-dimensional ESTER models predict the structure and the large-scale flows (differential rotation and meridional circulation) of stars with mass larger than 1.7Msun at any rotation rate. Main sequence evolution can be mimicked by varying the hydrogen content of the convective core. Models have been successfully tested on half a dozen of nearby fast rotating stars observed with optical or infra-red interferometers. They are now the right tool to investigate the oscillation spectrum of early-type fast rotators.
The Sun and stars: Giving light to dark matter  [PDF]
Jordi Casanellas,Ilídio Lopes
Physics , 2014, DOI: 10.1142/S021773231440001X
Abstract: During the last century, with the development of modern physics in such diverse fields as thermodynamics, statistical physics, and nuclear and particle physics, the basic principles of the evolution of stars have been successfully well understood. Nowadays, a precise diagnostic of the stellar interiors is possible with the new fields of helioseismology and astroseismology. Even the measurement of solar neutrino fluxes, once a problem in particle physics, is now a powerful probe of the core of the Sun. These tools have allowed the use of stars to test new physics, in particular the properties of the hypothetical particles that constitute the dark matter of the Universe. Here we present recent results obtained using this approach.
Flavour Physics and Grand Unification
Masiero, A.;Vempati, S. K.;Vives, O.
High Energy Physics - Phenomenology , 2007,
Abstract: In spite of the enormous success of the Standard Model (SM), we have strong reasons to expect the presence of new physics beyond the SM at higher energies. The idea of the Grand Unification of all the known interactions in nature is perhaps the main reason behind these expectations. Low-energy Supersymmetry is closely linked with grand unification as a solution of the hierarchy problem associated with the ratio M_GUT / M_Z. In these lectures we will provide a general overview of Grand Unification and Supersymmetry with special emphasis on their phenomenological consequences at low energies. We will analyse the flavour and CP problems of Supersymmetry and try to identify in these associated low-energy observables possible indications of the existence of a Grand Unified theory at high energies.
Grand challenges for evolutionary robotics  [PDF]
A.E. Eiben
Frontiers in Robotics and AI , 2014, DOI: 10.3389/frobt.2014.00004
Abstract: Evolutionary Robotics is a ?eld that “aims to apply evolutionary computation techniques to evolve the overall design or controllers, or both, for real and simulated autonomous robots” [13]. This approach is “useful both for investigating the design space of robotic applications and for testing scienti?c hypotheses of biological mechanisms and processes” [8]. However, as noted in [2] “the use of metaheuristics [i.e., evolution] sets this sub?eld of robotics apart from the mainstream of robotics research” which “aims to continuously generate better behavior for a given robot, while the long-term goal of Evolutionary Robotics is to create general, robot-generating algorithms”. One could say that Evolutionary Robotics is a test ground or experimental toolbox to study various issues arising on the road to intelligent and autonomous machines. The related issues include embodied cognition and intelligence, self-organization and collective behaviour, the emergence of communication and cooperation, co-evolution, neuro-evolution, and many more with robots forming the substrate or medium for the experiments [2, 3, 8, 10, 12, 13, 14]. Given the fact that many Evolutionary Robotics investigations are performed in simulation there is a big overlap with a sub?eld in Arti?cial Life research that is concerned with evolving virtual creatures and societies. However, I think it is safe to say that robotics can be distinguished by ultimately aiming at real physical robots (a.k.a. intelligent machines, animate artefacts, arti?cial organisms, ...) that exist and operate in the real world. Their bodies can be made of traditional mechatronic components, (self-)assembled from simple modular units, formed by some soft material, 3D printed plastics, some fancy new stuff invented by material scientists, or any combination of these, but in the end the robots must be physical entities. Therefore, Grand Challenges for Evolutionary Robotics must be tangible. Furthermore, Grand Challenges should be demonstrations of evolution, either a particular property of it, or the process of evolution as a whole. In the following I propose three Grand Challenges, subject to discussion. This list is not meant to capture the ultimate goals for the ?eld. Rather, it is meant to inspire the community to deliberate and collectively identify the bold dreams that can lead further developments. This paper achieves its main goal if the list of Grand Challenges is discussed and revised, leading to an adjusted version that has a broad support. THE ROBOT KANGAROO Natural and arti?cial evolution are praised for
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