Separation results for the size of constant-depth propositional proofs

We define a general method to lift principles requiring exponential tree-size (d+12)-LK-refutations for d∈N to principles requiring exponential sequence-size d-LK-refutations, which will be described for the Ramsey principle and d=0. From this we also deduce width lower bounds for resolution refutations of the Ramsey principle.