The following text, taken from the original proposal for corpes05, gives preliminary informations on the scope of the seminar.

Strong need for interface between theory and experiment ARPES has conquered a central position in the experimental research on strongly correlated electronic materials, because it gives access to the self-energy corrections of low-lying single particle excitations in the many-electron system, concerning both energy and momentum dependence. It allows, in some materials, to confirm and visualise Landau's famous concept of quasi-particles, but also to explore the limits of this concept in others. Data acquisition itself goes through an explosive period of qualitative and quantitative improvements. Forthcoming new generations of synchrotrons and analysers are at the centre of this development. The polarisation and frequency of ever more sharply defined photon beams, as well as spin polarization of the photocurrent are recognized as additional, highly pertinent experimental control parameters. Multi-channel analysers allow to simultaneously cover large portions of the parameter space. The newly achieved resolutions, together with very low temperature sample environment, will allow studying strongly renormalized electrons on multi-sheeted Fermi surfaces. In order to extract reliable information from this wealth of data, all the following topics from solid-state theory, some in rapid evolution others well established, have to be dealt with, many of them simultaneously: Dynamical mean field theory (DMFT) for itinerant self-energy corrections, in the presence of local repulsion within d- and f-shells. Competing (or complementary) routines for the "impurity solvers" in DMFT. Momentum and crystal-field dependence of self-energy corrections beyond DMFT. Multi-band Dyson equation. Hybridisation versus Coulomb repulsion. Orbital effects. Spin-orbit coupling. Fully relativistic theory. Quantum chemistry methods. Cluster calculations. High-spin states (Hund's rule) versus low-spin states (Goodman, Zhang-Rice). Link to GW and Gutzwiller methods Modelling of sample surface and disorder. Reduction or enhancement of many-body effects in the outer layers. Numerical renormalisation group. Kondo screening. Fixed point behaviour. Dimensional crossover. Solvable toy models in low dimensions. Exact diagonalisation of finite systems. Phonons. Collective degrees of freedom. Effective boson-fermion models. Phenomenological self-energy corrections of non-Fermi liquid type. Downfolded Hilbert space, spanned by single-electron orbitals, calculated "ab-initio" (static mean field theory) including superstructure and surface. Initial state Bloch and Wannier orbitals. DFT-, LDA-methods. Final state orbitals. Multiple scattering (Inverse LEED). "Lifetime broadening" from finite escape depth. Matrix elements of photo-ionisation process, using orbitals in the downfolded Hilbert space. Symmetry analysis. Low symmetry approach. Photon and electron beam polarisation. Dichroism. Resonant photoemission. Fano or Cooper interference phenomena. "Extrinsic" energy loss as function of binding energy and photon energy. This list, and it is not exhaustive, is looked at by most as a collection of concepts, explaining some features that prevail in a given set of data. In fact, the importance of intuition in combining these concepts cannot be denied, since the solution of the full problem will remain open for a long time. However, there are attempts to unite two or more of the above areas, to place them more systematically in the framework of a "one-step" formalism, in a way that can be made operational for data analysis and eventually lead to the establishment of user friendly codes. The fact that such codes exist already for weakly correlated systems and for surface physics can be one of the guidelines. Most urgently: The initial state of correlated electrons is not approximated precisely enough in the established "one-step" codes for the photocurrent. Then, roughly speaking, combining items at the top of the list with those towards the end appears central to the new effort that is required. Obviously, it will depend on this task, to be carried out on the theory side, whether the interface between many-body theory and ARPES can be increased. We want to encourage such attempts and support them in the seminar part of CORPES05. It will not be a school. We shall prefer candidates already involved in the described type of synthesis or willing to enter a cooperation. Some experimentalists, strongly motivated by theoretical interpretation, eventually some software- and data analysis- specialists can ideally complete the profile of the seminar. For the theorists, it will ideally involve a commitment of 2-3 weeks. Pioneering applications could concern any of the experimental systems with strong correlations that are studied by ARPES, involving a variety of proposed model Hamiltonians. High Tc cuprates are presently still a main focus. Among other exciting fields we mention transition metal compounds: manganates, ruthenates, cobaltates; heavy fermion- and Kondo-insulator compounds; quasi one- and two-dimensional metals; surface and edge states; nano-tubes and artificial structures.

Proposal for a periodic event We think that it would be desirable to install a periodic event, focusing on this type of synthesis as a common denominator and being divided up, similarly as CORPES05, into a seminar and a workshop. Infrastructure and financing should come from existing and planned high performance synchrotron facilities, which could also take turns in hosting the event. It would require, in fact, only a minute fraction of the budget, now invested in improving the light sources and analysers. The complexity of the problems justifies a limitation to ARPES, notwithstanding the need to cross-fertilise with other techniques in more general meetings on spectroscopy of correlated electrons, such as the SNS series (last SNS2004 in Sitges, Spain). Whereas the seminar is dedicated to the advancement of photoemission theory, new experimental results, along with progress in the data interpretation and availability of codes, could be discussed among the interested community in the joint workshop of shorter length. The Max Planck Society's theoretical institute for the physics of complex systems, MPI-PKS, in the pleasant city of Dresden, is the ideal venue to jump-start our project. The institute is used to events combining a longer seminar with 15-20 invited participants and a shorter workshop with up to 100 participants. It will provide know-how, financial support and infrastructure for CORPES05. The celebration of the centenary of Einstein's groundbreaking paper on photoemission is an additional motivation.