Quantum field theory can be seen as a set of methods and ideas that, besides its importance in the study of the elementary particles, has been widely used in other areas.In particular, it constitutes an indispensable framework in the modern approach to phase transitions and critical phenomena.The origin of this constant relationship between field theory and condensed matter is due to the fact that despite their superficial differences, both deal with problems involving a large number of degrees of freedom.Thus, it is not surprising that the same techniques may be useful in both fields.This work addresses problems in these two areas and it is essentially divided in two parts.The first part is devoted to the study of field theories with an anisotropy between space and time, which implies a breaking of the Lorentz symmetry.One of the motivations for considering this kind of theory is precisely the study of phase transitions in condensed matter systems.Renormalization group analysis with emphasis on the possibility of restoration of the Lorentz symmetry and also a discussion about Ward identities are performed.In the second part, the attention is centered on statistical mechanics but with an approach typical of field theory, in particular, focused to the study of classical and quantum phase transitions from the quantized version of the spherical model and its supersymmetric extension.
Quantum field theory can be seen as a set of methods and ideas that, besides its importance in the study of the elementary particles, has been widely used in other areas.In particular, it constitutes an indispensable framework in the modern approach to phase transitions and critical phenomena.The origin of this constant relationship between field theory and condensed matter is due to the fact that despite their superficial differences, both deal with problems involving a large number of degrees of freedom.Thus, it is not surprising that the same techniques may be useful in both fields.This work addresses problems in these two areas and it is essentially divided in two parts.The first part is devoted to the study of field theories with an anisotropy between space and time, which implies a breaking of the Lorentz symmetry.One of the motivations for considering this kind of theory is precisely the study of phase transitions in condensed matter systems.Renormalization group analysis with emphasis on the possibility of restoration of the Lorentz symmetry and also a discussion about Ward identities are performed.In the second part, the attention is centered on statistical mechanics but with an approach typical of field theory, in particular, focused to the study of classical and quantum phase transitions from the quantized version of the spherical model and its supersymmetric extension.
Abstract Introduced as a quantum extension of Maxwell's classical theory, quantum electrodynamic (QED) has been the first example of a quantum field theory (QFT). Eventually, QFT has become the framework for the discussion of all fundamental interactions at the microscopic scale except, possibly, gravity. More surprisingly, it has also provided a framework for the understanding of second order phase transitions in statistical mechanics. In fact, as hopefully this work illustrates, QFT is the natural framework for the discussion of most systems involving an infinite number of degrees of freedom with local couplings. These systems range from cold Bose gases at the condensation temperature (about ten nanokelvin) to conventional phase transitions (from a few degrees to several hundred) and high energy particle physics up to a TeV, altogether more than twenty orders of magnitude in the energy scale. Therefore, although excellent textbooks about QFT had already been published, I thought, many years ago, that it might not be completely worthless to present a work in which the strong formal relations between particle physics and the theory of critical phenomena are systematically emphasized. This option explains some of the choices made in the presentation. A formulation in terms of field integrals has been adopted to study the properties of QFT. The language of partition and correlation functions has been used throughout, even in applications of QFT to particle physics. Renormalization and renormalization group (RG) properties are systematically discussed. The notion of effective field theory (EFT) and the emergence of renormalizable theories are described. The consequences for fine-tuning and triviality issue are emphasized. This fifth edition has been updated and fully revised.
The sophistication of modern tools used in the study of statistical mechanics and field theory is often an obstacle to the easy understanding of new important current results reported in journals. The main purpose of this book is to introduce the reader to the methods of the fluctuation (field) theory of phase transitions and critical phenomena so as to provide a good source for research. The introductory contents are concerned with ideas of description, thermodynamic stability theory related to phase transitions, major experimental facts, basic models and their relationships. Special attention is paid to the mean field approximation and to the Landau expansion for simple and complex models of critical and multicritical phenomena. An instructive representation of the modern perturbation theory and the method of the renormalization group is developed for field models of phase transitions. The essential influence of the fluctuations on the critical behaviour is established together with the theory of correlation functions, Gaussian approximation, the Ginzburg criterion, [symbol]- and 1/n- expansions as practical realizations of the renormalization group ideas. Applications of the theory to concrete aspects of condensed matter physics are considered: quantum effects, Bose condensation, crystal anisotropy, superconductors and liquid crystals, effects of disorder of type randomly distributed quenched impurities and random fields. This volume can be used as an advanced University course book for students with a basic knowledge of statistical physics and quantum mechanics. It could be considered as a complementary text to a standard University course on statistical physics
Abstract This book provides a thorough introduction to the fascinating world of phase transitions as well as many related topics, including random walks, combinatorial problems, quantum field theory and S-matrix. Fundamental concepts of phase transitions, such as order parameters, spontaneous symmetry breaking, scaling transformations, conformal symmetry, and anomalous dimensions, have deeply changed the modern vision of many areas of physics, leading to remarkable developments in statistical mechanics, elementary particle theory, condensed matter physics and string theory. This self-contained book provides an excellent introduction to frontier topics of exactly solved models in statistical mechanics and quantum field theory, renormalization group, conformal models, quantum integrable systems, duality, elastic S-matrix, thermodynamics Bethe ansatz and form factor theory. The clear discussion of physical principles is accompanied by a detailed analysis of several branches of mathematics, distinguished for their elegance and beauty, such as infinite dimensional algebras, conformal mappings, integral equations or modular functions. Besides advanced research themes, the book also covers many basic topics in statistical mechanics, quantum field theory and theoretical physics. Each argument is discussed in great detail, paying attention to an overall coherent understanding of physical phenomena. Mathematical background is provided in supplements at the end of each chapter, when appropriate. The chapters are also followed by problems of different levels of difficulty. Advanced undergraduate and graduate students will find a rich and challenging source for improving their skills and for accomplishing a comprehensive learning of the many facets of the subject.
This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book highlights quantum field theory techniques that were developed in parallel in high energy physics and condensed matter physics. It explains the relevance of quantum field theory methods developed in the context of high energy physics, to many particle systems, even though, in principle, quantum mechanics may suffice to understand these systems. The book discusses the modern perspective of phase transitions and use a length scale based approach. It deals with the application of the ideas of bosonization in simple one-dimensional models such as spin models and the Hubbard model, where the calculational tools of bosonization and Renormalisation group are used to compute physically relevant quantities like conductances. The book also highlights the idea that topological concepts play an important role in a wide range of phenomena.
Critical phenomena is one of the most exciting areas of modern physics. This 2007 book provides a thorough but economic introduction into the principles and techniques of the theory of critical phenomena and the renormalization group, from the perspective of modern condensed matter physics. Assuming basic knowledge of quantum and statistical mechanics, the book discusses phase transitions in magnets, superfluids, superconductors, and gauge field theories. Particular attention is given to topics such as gauge field fluctuations in superconductors, the Kosterlitz-Thouless transition, duality transformations, and quantum phase transitions - all of which are at the forefront of physics research. This book contains numerous problems of varying degrees of difficulty, with solutions. These problems provide readers with a wealth of material to test their understanding of the subject. It is ideal for graduate students and more experienced researchers in the fields of condensed matter physics, statistical physics, and many-body physics.
A teoria quântica de campos pode ser vista como um conjunto de métodos e idéias que além de sua importância no estudo das partículas elementares, tem sido amplamente usada em outras áreas. Em especial, ela constitui uma ferramenta indispensável no estudo moderno de transições de fases e fenômenos críticos. A origem dessa constante relação entre a teoria de campos e a matéria condensada deve-se ao fato que, apesar de suas diferenças superficiais, ambas tratam de problemas envolvendo um grande número de graus de liberdade. Assim, não é surpreendente que as mesmas técnicas possam ser úteis nos dois campos. Este trabalho trata de problemas nessas duas áreas e está essencialmente divido em duas partes. A primeira parte é dedicada ao estudo de teorias de campos com uma anisotropia entre o espaço e o tempo, o que implica uma quebra da simetria de Lorentz. Uma das motivações para considerar esse tipo de teoria vem justamente do estudo de transições de fase em sistemas da matéria condensada. Análises do grupo de renormalização com ênfase na possibilidade de restauração da simetria de Lorentz e também uma discussão sobre identidades de Ward são realizadas. Na segunda parte, a atenção é voltada para a mecânica estatística mas com uma abordagem típica da teoria de campos, em especial, voltada para o estudo de transições de fase clássicas e quânticas a partir da versão quantizada do modelo esférico e de sua extensão supersimétrica.