The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Francesco Mauri - One of the best experts on this subject based on the ideXlab platform.
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nonlocal pseudopotentials and Magnetic Fields
Physical Review Letters, 2003Co-Authors: Chris J. Pickard, Francesco MauriAbstract:We show how to describe the coupling of electrons to nonuniform Magnetic Fields in the framework of the widely used norm-conserving pseudopotential approximation for electronic structure calculations. Our derivation applies to Magnetic Fields that are smooth on the scale of the core region. The method is validated by application to the calculation of the Magnetic susceptibility of molecules within density functional theory (DFT) in the local density approximation. Our results are compared with high-quality all-electron DFT results obtained using Gaussian basis sets and another recently proposed pseudopotential formalism.
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Nonlocal pseudopotentials and Magnetic Fields
Physical Review Letters, 2003Co-Authors: Chris J. Pickard, Francesco MauriAbstract:We show how to describe the coupling of electrons to non-uniform Magnetic Fields in the framework of the widely used norm-conserving pseudopotential appro ximation for electronic structure calculations. Our derivation applies to Magnetic Fields that are smooth on the scale of the core region. The method is validated by application to the calculation of the Magnetic susceptibility of molecules. Our results are compared with high quality all electron quantum chemical results, and another recently proposed formalism.
Kandaswamy Subramanian - One of the best experts on this subject based on the ideXlab platform.
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the origin evolution and signatures of primordial Magnetic Fields
Reports on Progress in Physics, 2016Co-Authors: Kandaswamy SubramanianAbstract:The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host Magnetic Fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak ∼ 10(-16) Gauss Magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed Magnetic Fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial Magnetic Fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to Magnetic field generation during inflation and phase transitions. We trace the linear and nonlinear evolution of the generated primordial Fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial Magnetic Fields on the cosmic microwave background, including current constraints from Planck, are discussed. After recombination, primordial Magnetic Fields could strongly influence structure formation, especially on dwarf galaxy scales. The resulting signatures on reionization, the redshifted 21 cm line, weak lensing and the Lyman-α forest are outlined. Constraints from radio and γ-ray astronomy are summarized. Astrophysical batteries and the role of dynamos in reshaping the primordial field are briefly considered. The review ends with some final thoughts on primordial Magnetic Fields.
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the origin evolution and signatures of primordial Magnetic Fields
arXiv: Cosmology and Nongalactic Astrophysics, 2015Co-Authors: Kandaswamy SubramanianAbstract:The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host Magnetic Fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak $\sim 10^{-16}$ Gauss Magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed Magnetic Fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial Magnetic Fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to Magnetic field generation during inflation and other phase transitions. We trace the linear and nonlinear evolution of the generated primordial Fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial Magnetic Fields on the cosmic microwave background, including current constraints from Planck, are discussed. After recombination, primordial Magnetic Fields could strongly influence structure formation, especially on dwarf galaxy scales. The resulting signatures on reionization, the redshifted 21 cm line, weak lensing and the Lyman-$\alpha$ forest are outlined. Constraints from radio and $\gamma$-ray astronomy are summarized. Astrophysical batteries and the role of dynamos in reshaping the primordial field are briefly considered. The review ends with some final thoughts on primordial Magnetic Fields.
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The First Magnetic Fields
Space Science Reviews, 2012Co-Authors: Lawrence M Widrow, D. Ryu, D. R. G. Schleicher, Christos G Tsagas, Kandaswamy Subramanian, Rudolf A. TreumannAbstract:We review current ideas on the origin of galactic and extragalactic Magnetic Fields. We begin by summarizing observations of Magnetic Fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale Magnetic Fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of Magnetic Fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark–hadron phase transition. The implications of strong primordial Magnetic Fields for the reionization epoch as well as the first generation of stars are discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate Fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, Magnetic Fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium.
Rudolf A. Treumann - One of the best experts on this subject based on the ideXlab platform.
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The Strongest Magnetic Fields in the Universe - The strongest Magnetic Fields in the Universe
Space Sciences Series of ISSI, 2016Co-Authors: V. S. Beskin, André Balogh, Maurizio Falanga, M. Lyutikov, S. Mereghetti, T. Piran, Rudolf A. TreumannAbstract:This volume extends the ISSI series on Magnetic Fields in the Universe into the domain of what are by far the strongest Fields in the Universe, and stronger than any field that could be produced on Earth. The chapters describe the Magnetic Fields in non-degenerate strongly magnetized stars, degenerate stars (such as white dwarfs and neutron stars), exotic members called magnetars, and in their environments, as well as Magnetic Fields in the environments of black holes. These strong Fields have a profound effect on the behavior of matter, visible in particular in highly variable processes like radiation in all known wavelengths, including Gamma-Ray bursts. The generation and structure of such strong Magnetic Fields and effects on the environment are also described
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Large-Scale Magnetic Fields in the Universe - Large-scale Magnetic Fields in the universe
Space Sciences Series of ISSI, 2013Co-Authors: Rainer Beck, Andrei Bykov, André Balogh, Rudolf A. Treumann, Lawrence M WidrowAbstract:From the Contents: Magnetic Fields in the Large-scale Structure of the Universe.- The First Magnetic Fields.- Current Status of Turbulent Dynamo Theory: From Large-scale to Small-scale Dynamos.- Magnetic Fields in Cosmic Particle Acceleration Sources.- Cosmic rays in galactic and extragalactic Magnetic Fields.- Magnetic Fields in galactic haloes.- Magnetic Fields in Massive Stars, their Winds, and their Nebulae.- Magnetic Fields, Relativistic Particles, and Shock Waves in Cluster Outskirts.- Magnetic Fields in Galaxies.
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Magnetic Fields in the Large-Scale Structure of the Universe
Space Science Reviews, 2012Co-Authors: D. Ryu, D. R. G. Schleicher, Rudolf A. Treumann, Christos G Tsagas, Lawrence M WidrowAbstract:Magnetic Fields appear to be ubiquitous in astrophysical environments. Their existence in the intracluster medium is established through observations of synchrotron emission and Faraday rotation. On the other hand, the nature of Magnetic Fields outside of clusters, where observations are scarce and controversial, remains largely unknown. In this chapter, we review recent developments in our understanding of the nature and origin of intergalactic Magnetic Fields, and in particular, intercluster Fields. A plausible scenario for the origin of galactic and intergalactic Magnetic Fields is for seed Fields, created in the early universe, to be amplified by turbulent flows induced during the formation of the large scale structure. We present several mechanisms for the generation of seed Fields both before and after recombination. We then discuss the evolution and role of Magnetic Fields during the formation of the first starts. We describe the turbulent amplification of seed Fields during the formation of large scale structure and the nature of the Magnetic Fields that arise. Finally, we discuss implications of intergalactic Magnetic Fields.
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The First Magnetic Fields
Space Science Reviews, 2012Co-Authors: Lawrence M Widrow, D. Ryu, D. R. G. Schleicher, Christos G Tsagas, Kandaswamy Subramanian, Rudolf A. TreumannAbstract:We review current ideas on the origin of galactic and extragalactic Magnetic Fields. We begin by summarizing observations of Magnetic Fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale Magnetic Fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of Magnetic Fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark–hadron phase transition. The implications of strong primordial Magnetic Fields for the reionization epoch as well as the first generation of stars are discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate Fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, Magnetic Fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium.
Chris J. Pickard - One of the best experts on this subject based on the ideXlab platform.
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nonlocal pseudopotentials and Magnetic Fields
Physical Review Letters, 2003Co-Authors: Chris J. Pickard, Francesco MauriAbstract:We show how to describe the coupling of electrons to nonuniform Magnetic Fields in the framework of the widely used norm-conserving pseudopotential approximation for electronic structure calculations. Our derivation applies to Magnetic Fields that are smooth on the scale of the core region. The method is validated by application to the calculation of the Magnetic susceptibility of molecules within density functional theory (DFT) in the local density approximation. Our results are compared with high-quality all-electron DFT results obtained using Gaussian basis sets and another recently proposed pseudopotential formalism.
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Nonlocal pseudopotentials and Magnetic Fields
Physical Review Letters, 2003Co-Authors: Chris J. Pickard, Francesco MauriAbstract:We show how to describe the coupling of electrons to non-uniform Magnetic Fields in the framework of the widely used norm-conserving pseudopotential appro ximation for electronic structure calculations. Our derivation applies to Magnetic Fields that are smooth on the scale of the core region. The method is validated by application to the calculation of the Magnetic susceptibility of molecules. Our results are compared with high quality all electron quantum chemical results, and another recently proposed formalism.
Richard M Crutcher - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Fields in molecular clouds
Annual Review of Astronomy and Astrophysics, 2012Co-Authors: Richard M CrutcherAbstract:This review examines observations of Magnetic Fields in molecular clouds and what those observations tell us about the theory of molecular cloud evolution and star formation. First, the review briefly summarizes classes of theoretical models of molecular clouds and specific predictions of the models that can be tested by observation. Then, the review describes the techniques for observing and mapping Magnetic Fields in molecular clouds, followed by discussion of important examples of observational studies using each technique. A synthesis of results from all observational techniques summarizes the current state, which is that though Magnetic Fields generally dominate turbulence, there is no definitive evidence for Magnetic Fields dominating gravity in molecular clouds or for ambipolar-diffusion-driven star formation. Finally, the review discusses prospects for advances in our observational capabilities with telescopes and instruments now beginning operation or under construction.
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Magnetic Fields in molecular clouds
Eas Publications Series, 2007Co-Authors: Richard M CrutcherAbstract:Observations of Magnetic Fields in molecular clouds are essential for understanding their role in the evolution of dense clouds and in the star formation process. The two extreme-case models of star formation are the weak Magnetic field scenario, in which turbulence drives molecular cloud evolution and therefore star formation, and the strong Magnetic field scenario, with Magnetic Fields governing molecular cloud formation and ambipolar diffusion ultimately driving star formation. Continuum and spectral line polarization observations make it possible to infer Magnetic field strengths and morphologies, and therefore to test which of the two star formation scenarios dominates. The observational techniques available for such observations – the Zeeman effect, mapping of polarized dust emission, and mapping of linearly polarized line emission – are briefly described, together with how these observations can test star formation theory. Examples of the existing observations and the current state of the testing of Magnetically controlled star formation are presented. Finally, the prospects for the future of study of Magnetic Fields in molecular clouds and their role in the star formation process is discussed.
