Abstract
It is proved that any countable consistent theory with infinite models has a Σ-presentable model of cardinality 2ω over. It is shown that some structures studied in analysis (in particular, a semigroup of continuous functions, certain structures of nonstandard analysis, and infinite-dimensional separable Hilbert spaces) have no simple Σ-presentations in hereditarily finite superstructures over existentially Steinitz structures. The results are proved by a unified method on the basis of a new general sufficient condition.
Original language | English |
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Pages (from-to) | 458-472 |
Number of pages | 15 |
Journal | Algebra and Logic |
Volume | 56 |
Issue number | 6 |
DOIs | |
Publication status | Published - 1 Jan 2018 |
Keywords
- countable consistent theory
- existentially Steinitz structure
- hereditarily finite superstructure
- infinitedimensional separable Hilbert space
- nonstandard analysis
- semigroup of continuous functions
- Σ-presentability
- Sigma-presentability
- MODELS
- infinite-dimensional separable Hilbert space