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Harrington’s conservation theorem redone
 In: Archive for Mathematical Logic
, 2008
"... Leo Harrington showed that the secondorder theory of arithmetic WKL0 is Π 1 1conservative over the theory RCA0. Harrington’s proof is modeltheoretic, making use of a forcing argument. A purely prooftheoretic proof, avoiding forcing, has been eluding the efforts of researchers. In this short paper ..."
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Leo Harrington showed that the secondorder theory of arithmetic WKL0 is Π 1 1conservative over the theory RCA0. Harrington’s proof is modeltheoretic, making use of a forcing argument. A purely prooftheoretic proof, avoiding forcing, has been eluding the efforts of researchers. In this short paper, we present a proof of Harrington’s result using a cutelimination argument. 1
Submitted by Jon Brugger
"... Master Thesis Prooftheoretic aspects of weak König’s ..."
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Noname manuscript No. (will be inserted by the editor) Harrington’s Conservation Theorem Redone
"... Abstract Leo Harrington showed that the secondorder theory of arithmetic WKL0 is Π11conservative over the theory RCA0. Harrington’s proof is modeltheoretic, making use of a forcing argument. A purely prooftheoretic proof, avoiding forcing, has been eluding the efforts of researchers. In this sho ..."
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Abstract Leo Harrington showed that the secondorder theory of arithmetic WKL0 is Π11conservative over the theory RCA0. Harrington’s proof is modeltheoretic, making use of a forcing argument. A purely prooftheoretic proof, avoiding forcing, has been eluding the efforts of researchers. In this short paper, we present a proof of Harrington’s result using a cutelimination argument.