
arXiv: 2104.11123
The finite models of a universal sentence $\Phi$ in a finite relational signature are the age of a structure if and only if $\Phi$ has the joint embedding property. We prove that the computational problem whether a given universal sentence $\Phi$ has the joint embedding property is undecidable, even if $\Phi$ is additionally Horn and the signature of $\Phi$ only contains relation symbols of arity at most two.
FOS: Computer and information sciences, Computer Science - Logic in Computer Science, universal Horn sentence, Applications of universal algebra in computer science, Analysis of algorithms and problem complexity, Model theory of finite structures, Undecidability and degrees of sets of sentences, Mathematics - Logic, Joint embedding property, Logic in Computer Science (cs.LO), computer science - logic in computer science, QA1-939, FOS: Mathematics, Horn, mathematics - logic, Logic (math.LO), Universal, Mathematics, joint embedding property
FOS: Computer and information sciences, Computer Science - Logic in Computer Science, universal Horn sentence, Applications of universal algebra in computer science, Analysis of algorithms and problem complexity, Model theory of finite structures, Undecidability and degrees of sets of sentences, Mathematics - Logic, Joint embedding property, Logic in Computer Science (cs.LO), computer science - logic in computer science, QA1-939, FOS: Mathematics, Horn, mathematics - logic, Logic (math.LO), Universal, Mathematics, joint embedding property
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