Homepage of Martin Otto

• Introduction to Mathematical Logic (4+2, winter 16/17), moodle course


• Classical and Non-Classical Model Theory (Vertiefung Logik 4+2, summer 17), moodle course


• Automaten, Formale Sprachen, Entscheidbarkeit (FGdI I, 2+1, winter 16/17), moodle course


• Aussagenlogik & Prädikatenlogik (FGdI II, 2+1, summer 17), moodle course


• Seminar: Logics with Team Semantics (summer 17), announcement

Selected Publications and Preprints

Finite Approximations of Free Groups I: the F-Inverse Cover Problem, with Karl Auinger and Julian Bitterlich.
arXiv:2208.03273, 53 pages, revised 2025.

Finite Approximations of Free Groups II: the Theorems of Ash, Herwig-Lascar and Ribes-Zalesskii -- Revisited and Strengthened, with Karl Auinger and Julian Bitterlich.
arXiv:2507.11685, 85 pages, 2025.

Acyclicity in finite groups and groupoids,
arXiv:1806.08664, (corrected and extended) 60 pages, minor corrections/updates 2024.
replacing old version (withdrawn from arXiv)

Amalgamation and symmetry: from local to global consistency in the finite.
arXiv:1709.00031, (updated) 50 pages, 2024;
substantial re-organization of results from arXiv:1404.4599 (obsolete).

Guarded teams: the horizontally guarded case, with Erich Grädel.
preprint CSL 2020 paper, 2019. CSL proceedings

Graded modal logic and counting bisimulation
arXiv:1910.00039, preprint, 2019, revised 2023.

Inquisitive bisimulation, with Ivano Ciardelli.
Journal of Symbolic Logic, volume 86(1), pp.77-109, 2021. doi:10.1017/jsl.2020.77
older, more comprehensive version, 57 pages, 2018, revised 2020, arXiv:1803.03483;

On the expressive power of inquisitive epistemic logic, with Ivano Ciardelli.
companion paper to Inquisitive bisimulation, revised 2024
accepted for publication in Journal of Symbolic Logic, arXiv:2312.14573;

Cayley structures and common knowledge, with Felix Canavoi.
arXiv:1909.11521 preprint 46 pages, revised 2021.

A first-order framework for inquisitive modal logic, with Silke Meißner.
arxiv:1906.04981, Review of Symbolic Logic, 15 (2): pp. 311-333, 2022.

The freedoms of (guarded) bisimulation, with Erich Grädel.
In: Johan van Benthem on Logic and Information Dynamics, A. Baltag, S. Smets (eds), Springer 2014, pp. 3-31.

Common knowledge & multi-scale locality analysis in Cayley structures, with Felix Canavoi.
Conference paper in LICS 2017.

Pebble games and linear equations, with Martin Grohe.
Journal of Symbolic Logic, volume 80(3), 2015, pp. 797-844;
also see arXiv:1204.1990

Decidability results for the boundedness problem, with A. Blumensath and M. Weyer.
Journal version based on results in the ICALP'09 paper,
Logical Methods in Computer Science, 10 (3), 2014;
also see arXiv:1406.7684, Abstract

Finite conformal hypergraph covers and Gaifman cliques in finite structures, with Ian Hodkinson.
Bulletin of Symbolic Logic, volume 9, 2003, pp. 387-405. Abstract

An Interpolation Theorem,
Bulletin of Symbolic Logic, volume 6, 2000, pp. 447-462. Abstract

Elementary proof of the van Benthem - Rosen characterisation theorem,
technical report, TUD online preprint no.2342, 2004, 11 pages. Abstract

Symmetry and First-Order: Explicitly Presentation-Invariant Circuits.
Unpublished extended version of CSL 96 paper, 1994, 32 pages. Abstract

Selected Talks

Bisimulation and Logics for Knowledge and Information
Padova 2023.

ABC: Amalgamation, Bisimulation, Cycles
Erich Grädel's Fest, Berlin 2018.

Inquisitive bisimulation
Inquisitive Logic 18, Amsterdam 2018.

Modal logics with questions
AlMoTh 18, Berlin 2018.

Cayley structures as generic epistemic models
Logical Structures in Computation, Simons Institute reunion workshop, Berkeley 2017.

Back & forth between malleable finite models
Berkeley Logic Colloquium, Berkeley 2016.
(extended material on slides to go with a blackboard talk)

Symmetry-preserving finite synthesis and amalgamation
Workshop on Symmetry, Logic, Computation, Simons Institute, Berkeley 2016.

Logics for bisimulation invariance
Logical Structures Seminar, Simons Institute, Berkeley 2016.

Amalgamation and symmetries in the finite
Workshop on Model Theory of Finite and Pseudofinite Structures, Leeds 2016.

Amalgamation and local-to-global in the finite with suitable groupoids
New Pathways between Group Theory and Model Theory, Mülheim 2016.

Up to bisimulation -- but keep it finite!, Amsterdam 2015.

Local to Global: Amalgamation and Symmetries in Finite Structures
Leeds Logic Seminar & Algebra, Logic and Algorithms Seminar, Leeds 2015.
(slides to go with a talk delivered in condensed blackboard version)

Finite Global Realisations of Local Overlap Specifications
Special Session on Computational Logic, DMV-PTM meeting, Poznan 2014.

Bisimulation and Coverings for Graphs and Hypergraphs
5th Indian Conference on Logic and Its Applications, ICLA 2013, Chennai 2013.

Tractable Finite Models
Logic Colloquium, Barcelona 2011.

---

photograph at the top (new from 2024)
photograph below by L. Otto (2013)

My research interests primarily lie in connections between mathematical logic, model theory, combinatorics and the expressibility and complexity of structural properties. Before my appointment as a professor in mathematics at TU Darmstadt in 2003, I held a reader position in theoretical computer science at Swansea University in Wales. My academic background also encompasses earlier interests in geometry and mathematical physics (diploma thesis under the supervision of H Römer, Freiburg), abstract model theory (doctoral dissertation under the supervision of H-D Ebbinghaus, Freiburg) and, eventually, a focus on finite model theory (my habilitation in the group of E Grädel, RWTH Aachen) and logic in computer science. One theme that bridges some of these varied interests is that of similarities between and symmetries of structures and associated notions of indistinguishability based on logic and games.

---

April 2016, Martin Otto