Ebook: Renormalization Group Theory: Impact on Experimental Magnetism

Spin wave theory of magnetism and BCS theory of superconductivity are typical theories of the time before renormalization group (RG) theory. The two theories consider atomistic interactions only and ignore the energy degrees of freedom of the continuous (infinite) solid. Since the pioneering work of Kenneth G. Wilson (Nobel Prize of physics in 1982) we know that the continuous solid is characterized by a particular symmetry: invariance with respect to transformations of the length scale. Associated with this symmetry are particular field particles with characteristic excitation spectra. In diamagnetic solids these are the well known Debye bosons. This book reviews experimental work on solid state physics of the last five decades and shows in a phenomenological way that the dynamics of ordered magnets and conventional superconductors is controlled by the field particles of the infinite solid and not by magnons and Cooper pairs, respectively. In the case of ordered magnets the relevant field particles are called GSW bosons after Goldstone, Salam and Weinberg and in the case of superconductors the relevant field particles are called SC bosons. One can imagine these bosons as magnetic density waves or charge density waves, respectively. Crossover from atomistic exchange interactions to the excitations of the infinite solid occurs because the GSW bosons have generally lower excitation energies than the atomistic magnons. According to the principle of relevance the dynamics is governed by the excitations with the lowest energy. The non relevant atomistic interactions with higher energy are practically unimportant for the dynamics.

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Spin wave theory of magnetism and BCS theory of superconductivity are typical theories of the time before renormalization group (RG) theory. The two theories consider atomistic interactions only and ignore the energy degrees of freedom of the continuous (infinite) solid. Since the pioneering work of Kenneth G. Wilson (Nobel Prize of physics in 1982) we know that the continuous solid is characterized by a particular symmetry: invariance with respect to transformations of the length scale. Associated with this symmetry are particular field particles with characteristic excitation spectra. In diamagnetic solids these are the well known Debye bosons. This book reviews experimental work on solid state physics of the last five decades and shows in a phenomenological way that the dynamics of ordered magnets and conventional superconductors is controlled by the field particles of the infinite solid and not by magnons and Cooper pairs, respectively. In the case of ordered magnets the relevant field particles are called GSW bosons after Goldstone, Salam and Weinberg and in the case of superconductors the relevant field particles are called SC bosons. One can imagine these bosons as magnetic density waves or charge density waves, respectively. Crossover from atomistic exchange interactions to the excitations of the infinite solid occurs because the GSW bosons have generally lower excitation energies than the atomistic magnons. According to the principle of relevance the dynamics is governed by the excitations with the lowest energy. The non relevant atomistic interactions with higher energy are practically unimportant for the dynamics.

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Spin wave theory of magnetism and BCS theory of superconductivity are typical theories of the time before renormalization group (RG) theory. The two theories consider atomistic interactions only and ignore the energy degrees of freedom of the continuous (infinite) solid. Since the pioneering work of Kenneth G. Wilson (Nobel Prize of physics in 1982) we know that the continuous solid is characterized by a particular symmetry: invariance with respect to transformations of the length scale. Associated with this symmetry are particular field particles with characteristic excitation spectra. In diamagnetic solids these are the well known Debye bosons. This book reviews experimental work on solid state physics of the last five decades and shows in a phenomenological way that the dynamics of ordered magnets and conventional superconductors is controlled by the field particles of the infinite solid and not by magnons and Cooper pairs, respectively. In the case of ordered magnets the relevant field particles are called GSW bosons after Goldstone, Salam and Weinberg and in the case of superconductors the relevant field particles are called SC bosons. One can imagine these bosons as magnetic density waves or charge density waves, respectively. Crossover from atomistic exchange interactions to the excitations of the infinite solid occurs because the GSW bosons have generally lower excitation energies than the atomistic magnons. According to the principle of relevance the dynamics is governed by the excitations with the lowest energy. The non relevant atomistic interactions with higher energy are practically unimportant for the dynamics.

Content:
Front Matter....Pages 1-12
Introduction....Pages 1-8
History of Conventional Spin Wave Theory....Pages 9-23
Basic Issues of Renormalization Group (RG) Theory....Pages 25-52
Universality....Pages 53-68
Microscopic Processes....Pages 69-73
Non-Relevant Magnons....Pages 75-92
Crossover Phenomena....Pages 93-128
Metastability of Universality Classes....Pages 129-138
Relevant and Non-Relevant Interactions....Pages 139-158
Temperature Dependence of the Magnon Excitation Spectra....Pages 159-166
Magnetic Heat Capacity....Pages 167-184
Experimental Verification of GSW Bosons....Pages 185-198
Magnets With and Without Magnon Gap (Goldstone Mode)....Pages 199-222
Microscopic Details: Spin Structure, Site Disorder, Two Order Parameters....Pages 223-239
The Critical Magnetic Behaviour....Pages 241-308
Thermal Lattice Expansion and Magnetostriction....Pages 309-334
The Total Energy Content....Pages 335-338
Superconductivity....Pages 339-365
Conclusions....Pages 367-374
Back Matter....Pages 1-19

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Spin wave theory of magnetism and BCS theory of superconductivity are typical theories of the time before renormalization group (RG) theory. The two theories consider atomistic interactions only and ignore the energy degrees of freedom of the continuous (infinite) solid. Since the pioneering work of Kenneth G. Wilson (Nobel Prize of physics in 1982) we know that the continuous solid is characterized by a particular symmetry: invariance with respect to transformations of the length scale. Associated with this symmetry are particular field particles with characteristic excitation spectra. In diamagnetic solids these are the well known Debye bosons. This book reviews experimental work on solid state physics of the last five decades and shows in a phenomenological way that the dynamics of ordered magnets and conventional superconductors is controlled by the field particles of the infinite solid and not by magnons and Cooper pairs, respectively. In the case of ordered magnets the relevant field particles are called GSW bosons after Goldstone, Salam and Weinberg and in the case of superconductors the relevant field particles are called SC bosons. One can imagine these bosons as magnetic density waves or charge density waves, respectively. Crossover from atomistic exchange interactions to the excitations of the infinite solid occurs because the GSW bosons have generally lower excitation energies than the atomistic magnons. According to the principle of relevance the dynamics is governed by the excitations with the lowest energy. The non relevant atomistic interactions with higher energy are practically unimportant for the dynamics.

Content:
Front Matter....Pages 1-12
Introduction....Pages 1-8
History of Conventional Spin Wave Theory....Pages 9-23
Basic Issues of Renormalization Group (RG) Theory....Pages 25-52
Universality....Pages 53-68
Microscopic Processes....Pages 69-73
Non-Relevant Magnons....Pages 75-92
Crossover Phenomena....Pages 93-128
Metastability of Universality Classes....Pages 129-138
Relevant and Non-Relevant Interactions....Pages 139-158
Temperature Dependence of the Magnon Excitation Spectra....Pages 159-166
Magnetic Heat Capacity....Pages 167-184
Experimental Verification of GSW Bosons....Pages 185-198
Magnets With and Without Magnon Gap (Goldstone Mode)....Pages 199-222
Microscopic Details: Spin Structure, Site Disorder, Two Order Parameters....Pages 223-239
The Critical Magnetic Behaviour....Pages 241-308
Thermal Lattice Expansion and Magnetostriction....Pages 309-334
The Total Energy Content....Pages 335-338
Superconductivity....Pages 339-365
Conclusions....Pages 367-374
Back Matter....Pages 1-19
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