Quantum Field Theory has become the universal language of most modern theoretical physics. This introductory textbook shows how this beautiful theory offers the correct mathematical framework to describe and understand the fundamental interactions of elementary particles. The book begins with a brief reminder of basic classical field theories, electrodynamics and general relativity, as well as their symmetry properties, and proceeds with the principles of quantisation following Feynman's path integral approach. Special care is used at every step to illustrate the correct mathematical formulation of the underlying assumptions. Gauge theories and the problems encountered in their quantisation are discussed in detail. The last chapters contain a full description of the Standard Model of particle physics and the attempts to go beyond it, such as grand unified theories and supersymmetry. Written for advanced undergraduate and beginning graduate students in physics and mathematics, the book could also serve as a reference for active researchers in the field.

String Theory is our current best candidate for the unification of all fundamental forces, including gravity, in a consistent quantum framework. In this collection of lectures delivered at the Carg se Summer School "String Theory: from Gauge Interactions to Cosmology'', world leading experts provide an up-to-date survey of the latest developments in this topic, including the gauge/gravity correspondence, superstring cosmology and cosmic strings, topological string theory and matrix models, physics beyond the standard model and the landscape of vacua of string theory, conformal field theory and critical phenomena in statistical mechanics. Many more topics are also discussed in shorter contributions by School participants. Written with an emphasis on pedagogy, this volume will be a invaluable resource to students and experts alike.

The book gathers the lecture notes of the Les Houches Summer School that was held in August 2011 for an audience of advanced graduate students and post-doctoral fellows in particle physics, theoretical physics, and cosmology, areas where new experimental results were on the verge of being discovered at CERN. Every Les Houches School has its own distinct character. This one was held during a summer of great anticipation that at any moment contact might be made with the most recent theories of the nature of the fundamental forces and the structure of space-time. In fact, during the session, the long anticipated discovery of the Higgs particle was announced. The book vividly describes the fruitful and healthy "schizophrenia" that is the rule among the community of theoreticians who have split into several components: those doing phenomenology, and those dealing with highly theoretical problems, with a few trying to bridge both domains. The lectures by theoreticians covered many directions in the theory of elementary particles, from classics such as the Supersymmetric Standard Model to very recent ideas such as the relation between black holes, hydrodynamics, and gauge-gravity duality. The lectures by experimentalists explained in detail how intensively and how precisely the LHC collider has verified the theoretical predictions of the Standard Model, predictions that were at the front lines of experimental discovery during the 70's, 80's and 90's, and how the LHC is ready to make new discoveries. They described many of the ingenious and pioneering techniques developed at CERN for the detection and the data analysis of billions of billions of proton-proton collisions.

Fractal Structure in 4d Gravity.- A One Dimensional Ideal Gas of Spinons, or Some Exact Results on the XXX Spin Chain with Long Range Interaction.- Kodaira-Spencer Theory of Gravity.- 3d Gravity and Gauge Theories.- On the W-Gravity Spectrum and its G-Structure.- Light-Cone Quantization of Matrix Models at c>1.- Multicritical Points of 2-Matrix Models.- The Super Self-Dual Matreoshka.- The Phenomenology of Strings and Clusters in the 3-d Ising Model.- Conformai Field Theory Techniques in Large N Yang-Mills Theory.- to Differential W-Geometry.- Topological Strings and QCD in Two Dimensions.- Continuum QCD2 in Terms of Discrete Random Surfaces with Local Weights.- Strings and Causality.- Loop Equation and Area Law in Turbulence.- The Two-Dimensional String as a Topological Field Theory.- Linear Systems for 2d Poincare Supergravities.- Quantization of Mirror Symmetry.- Integrable Qft2 Encoded on Products of Dynkin Diagrams.- Remarks on Topological String Theories.- Hamiltonian Reduction of the BRST Complex and N=2 SUSY.- Lattice Models and N=2 Supersymmetry.- Canonical Construction of Liouville Field Operators with Arbitrary Spin.- Bethe Ansatz for the Bloch Particle in Magnetic Field.

String Theory is our current best candidate for the unification of all fundamental forces, including gravity, in a consistent quantum framework. In this collection of lectures delivered at the Carg se Summer School "String Theory: from Gauge Interactions to Cosmology'', world leading experts provide an up-to-date survey of the latest developments in this topic, including the gauge/gravity correspondence, superstring cosmology and cosmic strings, topological string theory and matrix models, physics beyond the standard model and the landscape of vacua of string theory, conformal field theory and critical phenomena in statistical mechanics. Many more topics are also discussed in shorter contributions by School participants. Written with an emphasis on pedagogy, this volume will be a invaluable resource to students and experts alike.

Quantum Field Theory has become the universal language of most modern theoretical physics. This introductory textbook shows how this beautiful theory offers the correct mathematical framework to describe and understand the fundamental interactions of elementary particles. The book begins with a brief reminder of basic classical field theories, electrodynamics and general relativity, as well as their symmetry properties, and proceeds with the principles of quantisation following Feynman's path integral approach. Special care is used at every step to illustrate the correct mathematical formulation of the underlying assumptions. Gauge theories and the problems encountered in their quantisation are discussed in detail. The last chapters contain a full description of the Standard Model of particle physics and the attempts to go beyond it, such as grand unified theories and supersymmetry. Written for advanced undergraduate and beginning graduate students in physics and mathematics, the book could also serve as a reference for active researchers in the field.