Isomorphism

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Two formulas <math>A</math> and <math>B</math> are isomorphic, when there are two proofs <math>\pi</math> of <math>A \vdash B</math> and <math>\rho</math> of <math>B \vdash A</math> such that eliminating the cut on <math>A</math> in
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Two formulas <math>A</math> and <math>B</math> are isomorphic (denoted <math>A\cong B</math>), when there are two proofs <math>\pi</math> of <math>A \vdash B</math> and <math>\rho</math> of <math>B \vdash A</math> such that eliminating the cut on <math>A</math> in
   
 
<math>\AxRule{}\VdotsRule{\pi}{A \vdash B}\AxRule{}\VdotsRule{\rho}{B \vdash A}\LabelRule{\rulename{cut}}\BinRule{B\vdash B}\DisplayProof</math>
 
<math>\AxRule{}\VdotsRule{\pi}{A \vdash B}\AxRule{}\VdotsRule{\rho}{B \vdash A}\LabelRule{\rulename{cut}}\BinRule{B\vdash B}\DisplayProof</math>
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<math>\LabelRule{\rulename{ax}}\NulRule{A\vdash A}\DisplayProof</math>.
 
<math>\LabelRule{\rulename{ax}}\NulRule{A\vdash A}\DisplayProof</math>.
   
Some well known isomorphisms of linear logic are the following ones:
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Linear logic admits [[List of isomorphisms|many isomorphisms]], but it is not known wether all of them have been discovered or not.
* <math>A\tens B \limp C \cong A\limp B \limp C</math>
 
* …
 

Latest revision as of 20:38, 25 April 2013

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Two formulas A and B are isomorphic (denoted A\cong B), when there are two proofs π of A \vdash B and ρ of B \vdash A such that eliminating the cut on A in

\AxRule{}\VdotsRule{\pi}{A \vdash B}\AxRule{}\VdotsRule{\rho}{B \vdash A}\LabelRule{\rulename{cut}}\BinRule{B\vdash B}\DisplayProof

leads to an η-expansion of

\LabelRule{\rulename{ax}}\NulRule{B\vdash B}\DisplayProof,

and eliminating the cut on B in

\AxRule{}\VdotsRule{\pi}{A \vdash B}\AxRule{}\VdotsRule{\rho}{B \vdash A}\LabelRule{\rulename{cut}}\BinRule{A\vdash A}\DisplayProof

leads to an η-expansion of

\LabelRule{\rulename{ax}}\NulRule{A\vdash A}\DisplayProof.

Linear logic admits many isomorphisms, but it is not known wether all of them have been discovered or not.

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