Nikolai Durov introduced the theory of generalized rings and schemes to study Arakelov geometry in an alternative algebraic framework, and introduced the residue field at the infinite place, F∞. We show an elementary algebraic approach to modules and algebras over this object, define prime congruences, show that the polynomial ring of n variables is of Krull dimension n, and derive a prime decomposition theorem for these primes.Proof. These are all trivial consequences of theorems in universal algebra.Proposition 2.11. Hom(M 1 , M 2 ) has a natural F-structure.Proof. The pointwise sum and scalar multiple of two homomorphisms is a homomorphism.Definition 2.12. Given two F-modules M 1 and M 2 , the tensor product M 1 ⊗ M 2 is a module with a natural bilinear map M 1 ×M 2 → M 1 ⊗M 2 where M 1 ×M 2 is the set of pairs, such that for any bilinear map M 1 × M 2 → N for some other module N , there is exactly one map M 1 ⊗ M 2 → N that makes the diagramProposition 2.13. Given two F-modules M 1 and M 2 , M 1 ⊗ M 2 exists and is unique. It is generated by elements of the form m 1 ⊗ m 2 with m 1 ∈ M 1 and m 2 ∈ M 2 . Furthermore · ⊗ M is a covariant functor.