Research by Topics
QCD Green Functions
The infrared behavior of QCD Green Functions is interesting from a purely theoretical point of view as well as with respect to phenomenological
applications in hadron physics. On the one hand, it provides insight into the confinement mechanisms of quarks and gluons. On the other hand, it serves as input into those equations which determine hadrons as bound states of colored constituents, the Bethe-Salpeter equations for mesons and the Faddeev equation
for baryons.
Related members:
Natália Alkofer, Reinhard Alkofer, Markus Hopfer, Valentin Mader, Mario Mitter, Bernd-Jochen Schaefer and Andreas Windisch
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QCD Thermodynamics
Our understanding of the properties of hadronic matter under extreme conditions, e.g. as present in the early universe or in compact stellar objects, has advanced significantly in recent years. Nevertheless, corresponding theoretical
ab initio investigations of QCD have only recently been started. Especially, calculations at non-vanishing chemical potentials are
challenging.
Related members:
Reinhard Alkofer, Tina K. Herbst, Markus Hopfer, Darjan Kozic, Mario Mitter, Matthias Puhr, Bernd-Jochen Schaefer and Andreas Windisch
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Hadron Structure
Our understanding of hadrons as bound states aims at uncovering hadron substructures in terms of quarks and gluons, the fundamental degrees of freedom of QCD.
Related members:
Reinhard Alkofer, Matthias Blatnik and Hèlios Sanchis-Alepuz
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Hadronic Reactions
Among hadronic reactions, our emphasis is on those sensitive to hadron substructure. In particular we aim at unveiling aspects of the confinement mechanism.
Related members:
Reinhard Alkofer and Matthias Blatnik
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Strong-Field QED: Particle Creation and Transport
In strong electromagnetic fields nonperturbative phenomena, e.g., the spontaneous production of electron-positron pairs happen. Studying the
time-dependence of such phenomena provides insight into non-equilibrium features of quantum field theories.
Related members:
Reinhard Alkofer, Florian Hebenstreit and Christian Kohlfürst
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Low-Dimensional Quantum-Field Theories
Low-dimensional Quantum Field Theories are of twofold interest. First, they serve as "laboratories" for novel theoretical methods. Second, there are several systems where such theories provide the description of effective degrees of freedom. E.g.,
QED in 2+1 dimensions is used to describe the low-energy electronic excitations close to the
edges of the d-wave symmetric Fermi surface in cuprates, i.e. the materials showing superconductivity at comparatively large temperatures.
Related members:
Reinhard Alkofer, Markus Hopfer and Andreas Windisch
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Research by Methods
Infrared Analysis of the Yang-Mills Dyson-Schwinger Equations
The infrared analysis of the integral equations representing the field equations for the n-point Green functions provides a novel technique to extract infrared properties of Yang-Mills theories analytically in a self-consistent approach. E.g. the infrared fixed point value of the strong running coupling has been calculated analytically.
Related members:
Natália Alkofer, Reinhard Alkofer and Valentin Mader
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Dyson-Schwinger Bethe-Salpeter Approach to Hadrons
The Dyson-Schwinger equations including the homogeneous Bethe-Salpeter equation allow Poincaré-covariant studies of hadrons as bound states of their constituents. In practice, the corresponding systems of coupled integral equations are solved numerically.
Related members:
Reinhard Alkofer, Matthias Blatnik and Hèlios Sanchis-Alepuz
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Renormalization-Group Equations
Renormalization-Group Equations are a nonperturbative method to determine Green functions of a quantum field theory. One starts with a classical action at large scales for an asymptotically free QFT. By integrating towards lower scales, quantum fluctuations are included and one arrives at an effective quantum action in the infrared.
Related members:
Natália Alkofer, Tina K. Herbst, Darjan Kozic, Mario Mitter, Matthias Puhr and Bernd-Jochen Schaefer
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Effective Field Theory
Effective field theory is a powerful tool that allows to obtain systematically improvable low-energy results for strongly coupled theories and has applications in many different fields of physics. This is achieved by studying only the effective interactions at the scale of interest and neglecting all unimportant microscopic aspects.
Related members:
Darjan Kozic, Tina K. Herbst, Mario Mitter, Matthias Puhr and Bernd-Jochen Schaefer
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Transport Equations
The time-dependence of phenomena like pair production are described within transport equations. E.g., the electron-positron pair production in strong laser fields can be explored using a parameter-free quantum kinetic equation.
Related members:
Reinhard Alkofer, Florian Hebenstreit and Christian Kohlfürst
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