New posts in nonstandard-models

Gödel's way of teaching non-standard models to Takeuti.

logic model-theory proof-theory incompleteness nonstandard-models

Is there a consistent arithmetically definable extension of PA that proves its own consistency?

logic proof-theory incompleteness nonstandard-models

Exponentiation and a weak fragment of arithmetic

logic model-theory nonstandard-models

Tennenbaum's theorem without overspill

model-theory computability peano-axioms nonstandard-models

What lessons have mathematicians drawn from the existence of non-standard models?

model-theory philosophy foundations nonstandard-models

PA├ ∃xP(x) but PA$\nvdash$ P(n) for any n?

first-order-logic incompleteness nonstandard-models

How does induction fail in computable nonstandard models?

logic nonstandard-models

How does Gödel Completeness fail in second-order logic?

logic model-theory first-order-logic incompleteness nonstandard-models

What is an example of a non standard model of Peano Arithmetic?

logic model-theory peano-axioms nonstandard-models

Model of concatenation theory with left-cancellation but no right-cancellation

logic model-theory proof-theory provability nonstandard-models