Quantum Field Theory is a rock on which rests the edifice of physics as we know it. The Standard Model, based on principles of Quantum Field Theory, describes the elementary constituents of matter and forces among them in an economic and mathematically elegant way. It has withstood innumerable tests and accurately predicts diverse phenomena from tiny quantum effects in electrodynamics to strong forces that keep atomic nuclei together. Understanding the nature and origin of the dark matter, an asymmetry between matter and anti-matter, and the formation of primordial inhomogeneities that eventually evolved into stars and galaxies all likely require an input from Quantum Field Theory.
Quantum Field Theory is blessed by symmetries, among which the gauge symmetry is central to our understanding of fundamental interactions. The Standard Model of elementary particles is a gauge theory encompassing the strong, electromagnetic and weak forces. The discovery of the Higgs boson at the Large Hadron Collider reconfirmed the validity of the Standard Model up to the highest energies accessible on Earth.
The most developed approach to Quantum Fields, based on the celebrated Feynman diagrams, is perturbative in an interaction strength. Feynman diagram technique is a highly versatile tool with applications in collider phenomenology, physics of Gravitational Waves, and theory of critical phenomena, to name a few. Experimental accuracy puts high demands on theoretical precision and new, more efficient perturbative tools are constantly being developed.
At strong coupling, when perturbation theory breaks down, Quantum Fields become highly non-linear and their dynamics cannot in general be predicted. The novel advances inspired by String Theory gave us a glimpse into strongly coupled behavior of Quantum Fields by means of Holographic Duality. Non-perturbative Quantum Field Theory has profound connections to many areas of mathematics. Symmetries, such as integrability or supersymmetry, play an increasingly important role and give rise to elegant solvable models where highly non-linear phenomena are under full analytic control.
The High-Energy Physics group at Nordita explores different areas of Quantum Field Theory, ranging from its fundamentals, and connection to mathematics to applications in particle phenomenology. Current activities are focussed on exactly solvable models, connections between Quantum Field Theory and String Theory, Holographic Duality, scattering amplitudes in gauge theories and gravity, and new ways to do perturbation theory more efficiently.
