Question

When does $(\square P \land \square Q) \to \square (P \land Q)$ hold?

score 266 · Answer 1 · 2026-02-23 01:20:49

266

Views

When does $(\square P \land \square Q) \to \square (P \land Q)$ hold?

Published on 23 Feb 2026 - 1:20

score 40 · Answer 2 · 2018-11-16 19:58:02

40

Views

Are there any statements $\phi$ where "$\vdash \phi$ or $\vdash \neg \phi$" was shown nonconstructively?

Published on 16 Nov 2018 - 19:58

score 1.4k · Answer 3 · 2026-02-23 01:22:59

1.4k

Views

The use and meaning of the "tilde-equal-symbol" for partial (recursive) functions in Girards monograph 'proof theory and logical complexity, volume 1'

Published on 23 Feb 2026 - 1:22

score 912 · Answer 4 · 2018-11-24 14:48:42

912

Views

proof of formula with Peano-axioms

Published on 24 Nov 2018 - 14:48

score 410 · Answer 5 · 2026-03-25 08:08:38

410

Views

show that for every consistent theory there is a complete consistent theory

Published on 25 Mar 2026 - 8:08

score 56 · Answer 6 · 2018-11-27 01:47:34

56

Views

Proving a statement of the form $P\rightarrow(\lnot Q\lor \lnot R)$.

Published on 27 Nov 2018 - 1:47

score 1.1k · Answer 7 · 2026-02-23 01:20:47

1.1k

Views

Show that $\Sigma \vdash\varphi$ if and only if $\Sigma\,\cup \{\neg\varphi\}$ is inconsistent.

Published on 23 Feb 2026 - 1:20

score 77 · Answer 8 · 2026-03-25 06:22:12

77

Views

Questions in proof theory (PRA-provability of an EA-axiom, Girards Book from '87)

Published on 25 Mar 2026 - 6:22

score 87 · Answer 9 · 2026-03-25 07:45:52

87

Views

Questions in proof theory (Definition of an interpretation of one theory in another, Girards Book from '87)

Published on 25 Mar 2026 - 7:45

score 92 · Answer 10 · 2026-03-25 07:44:38

92

Views

Questions in proof theory (interpretation of PRA in PA, Girards book from '87)

Published on 25 Mar 2026 - 7:44

score 85 · Answer 11 · 2026-03-25 06:24:56

85

Views

Questions in proof theory (PRA-provability of EA-theorems, Girards book from '87)

Published on 25 Mar 2026 - 6:24

score 119 · Answer 12 · 2018-12-01 22:02:29

119

Views

infinite and uncountable structures in specific classes of structures

Published on 01 Dec 2018 - 22:02

score 136 · Answer 13 · 2026-03-25 03:03:42

136

Views

Why the 'natural' consistency proof of PA cannot be carried out $\textbf{in}$ PA

Published on 25 Mar 2026 - 3:03

score 230 · Answer 14 · 2026-03-25 04:42:53

230

Views

An alternative formulation (or corollary) of Tarski's theorem? [Or just a typo?]

Published on 25 Mar 2026 - 4:42

score 50 · Answer 15 · 2018-12-06 09:40:17

50

Views

Is it possible to prove consistency of an axiomatic system without providing a model?

Published on 06 Dec 2018 - 9:40

List Question

When does $(\square P \land \square Q) \to \square (P \land Q)$ hold?

Are there any statements $\phi$ where "$\vdash \phi$ or $\vdash \neg \phi$" was shown nonconstructively?

The use and meaning of the "tilde-equal-symbol" for partial (recursive) functions in Girards monograph 'proof theory and logical complexity, volume 1'

proof of formula with Peano-axioms

show that for every consistent theory there is a complete consistent theory

Proving a statement of the form $P\rightarrow(\lnot Q\lor \lnot R)$.

Show that $\Sigma \vdash\varphi$ if and only if $\Sigma\,\cup \{\neg\varphi\}$ is inconsistent.

Questions in proof theory (PRA-provability of an EA-axiom, Girards Book from '87)

Questions in proof theory (Definition of an interpretation of one theory in another, Girards Book from '87)

Questions in proof theory (interpretation of PRA in PA, Girards book from '87)

Questions in proof theory (PRA-provability of EA-theorems, Girards book from '87)

infinite and uncountable structures in specific classes of structures

Why the 'natural' consistency proof of PA cannot be carried out $\textbf{in}$ PA

An alternative formulation (or corollary) of Tarski's theorem? [Or just a typo?]

Is it possible to prove consistency of an axiomatic system without providing a model?

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