Automated Reasoning for Security Protocols -- Computer Deduction and (Formal) Proofs in Mathematics -- From Counter-Model-based Quantifier Instantiation to Quantifier Elimination in SMT -- The CADE-27 ATP System Competition - CASC-27 -- Unification modulo Lists with Reverse - Relation with Certain Word Equations -- On the Width of Regular Classes of Finite Structures -- Extending SMT solvers to Higher-Order Logic -- Superposition with Lambdas -- Restricted Combinatory Unification -- dLi: Definite Descriptions in Differential Dynamic Logic -- SPASS-SATT { A CDCL(LA) Solver -- GRUNGE: A Grand Unified ATP Challenge -- Model Completeness, Covers and Superposition -- A Tableaux Calculus for Default Intuitionistic Logic -- NIL: Learning Nonlinear Interpolants -- ENIGMA-NG: Efficient Neural and Gradient-Boosted Inference Guidance for E -- Towards Physical Hybrid Systems -- SCL -- Clause Learning from Simple Models -- Names are not just Sound and Smoke: Word Embeddings for Axiom Selection -- Computing Expected Runtimes for Constant Probability Programs -- Automatic Generation of Logical Models with AGES -- Automata Terms in a Lazy WSkS Decision Procedure -- Confluence by Critical Pair Analysis Revisited -- Composing Proof Terms -- Combining ProVerif and Automated Theorem Provers for Security Protocol Verification -- Towards Bit-Width-Independent Proofs in SMT Solvers -- On Invariant Synthesis for Parametric Systems -- The Aspect Calculus -- Uniform Substitution At One Fell Swoop -- A Formally Verified Abstract Account of Gödel's Incompleteness Theorems -- Old or Heavy? Decaying Gracefully with Age/Weight Shapes -- Induction in Saturation-Based Proof Search -- Faster, Higher, Stronger: E 2.3 -- Certified Equational Reasoning via Ordered Completion -- JGXYZ - An ATP System for Gap and Glut Logics -- GKC: a Reasoning System for Large Knowledge Bases -- Optimization Modulo the Theory of Floating-Point Numbers -- FAME(Q): An Automated Tool for Forgetting in Description Logics with Qualified Number Restrictions. .

This book constitutes the proceeding of the 27th International Conference on Automated Deduction, CADE 27, held in Natal, Brazil, in August 2019. The 27 full papers and 7 system descriptions presented were carefully reviewed and selected from 65 submissions. CADE is the major forum for the presentation of research in all aspects of automated deduction, including foundations, applications, implementations, and practical experience. .