In 2008, to mark the 150th birthday of the former director Ludwig Quidde, the German Historical Institute in Rome dedicated a conference to the historian and Nobel Peace Prize winner.

[5] Since 2003, he has initiated several electronic publication formats at the DHI in Rome, which have been accessible on the platform "Romana Repertoria online/Roman Repertories online (RRO)" since 2012.

In his dissertation, he examined the constitutional and socio-historical situation of Trier in the late Middle Ages, mainly on the basis of municipal accounts.

[11] In another extensive study, he devoted himself to harbor cranes in the period between 1300 and 1600, with a geographical focus on the Rhine and its tributaries between Strasbourg and Düsseldorf.

[16] Matheus analyzed the foundings of the universities in Trier and Mainz in the context of intensive efforts at church reform and a general educational awakening in the Roman-German Empire, especially from the middle of the fifteenth century.

Rather, in 1798 the university was transformed into a French central school, which, however, continued to be viewed, in both its own and foreign perceptions, as the Université de Mayence.

The opening of the university in 1946, now named after the inventor of the art of printing Johannes Gutenberg, which was pushed through against competitors (especially Trier), was deliberately staged as a re-foundation by the French and German side.

[19] His thesis is that the importance of the Roman university location has been considerably underestimated thus far, especially for the period after the permanent return of the popes to the city.

The concept of the place of study, coined by Matheus, is also intended to direct our view beyond the university institutions to the considerable spectrum of possibilities for acquiring education in Rome during the Renaissance.

Despite the catastrophe of two world wars, the studies point to a considerable degree of resilience in the field of institutionalized international cooperation, not least thanks to personal networks.

From a comparative perspective, the Mediterranean region as a whole also comes into view, especially the spaces of encounter and conflict in the Levant and on the Iberian Peninsula, which are characterized by monotheistic religions and are important for Europe.

Matheus has demonstrated that the assessment of Lucera as a Muslim enclave, a garrison or an Arab ghetto in a Christian environment, which has dominated since the nineteenth century (expressed, among others, by Ferdinand Gregorovius), is in need of correction.

Rather, Muslims settled in a whole series of formerly Christian settlements in southern Italy, including the episcopal see of Tertiveri, which was established in Byzantine times and is a particular focus of the research.

As a doctoral student, the historian, who comes from a winegrowing family on his mother's side, discovered the oldest record to date that can be linked to Riesling cultivation on the Moselle.

[27] Since then, he has presented numerous studies on the history of the cultivation and culture of wine on the Rhine and Moselle, as well as on processes of continuity, but above all of structural change in wine-growing regions from antiquity to the twentieth century from a comparative European perspective.

[29] Matheus developed a heuristic instrument for comparative European studies on the history of the cultivation and culture of wine with the type of the winegrowers' village, a rural settlement with a pronounced urban character already found in the early Middle Ages.

He showed that before the production of grape marc spirits, high quality wines were produced there and exported north and east across the Alps for centuries.