YES Problem: a(a(d(d(x1)))) -> d(d(b(b(x1)))) a(a(x1)) -> b(b(b(b(b(b(x1)))))) b(b(d(d(b(b(x1)))))) -> a(a(c(c(x1)))) c(c(x1)) -> d(d(x1)) Proof: Matrix Interpretation Processor: dim=1 interpretation: [c](x0) = 2x0, [b](x0) = x0 + 1, [a](x0) = x0 + 4, [d](x0) = 2x0 orientation: a(a(d(d(x1)))) = 4x1 + 8 >= 4x1 + 8 = d(d(b(b(x1)))) a(a(x1)) = x1 + 8 >= x1 + 6 = b(b(b(b(b(b(x1)))))) b(b(d(d(b(b(x1)))))) = 4x1 + 10 >= 4x1 + 8 = a(a(c(c(x1)))) c(c(x1)) = 4x1 >= 4x1 = d(d(x1)) problem: a(a(d(d(x1)))) -> d(d(b(b(x1)))) c(c(x1)) -> d(d(x1)) Arctic Interpretation Processor: dimension: 2 interpretation: [0 2] [c](x0) = [0 2]x0, [0 0] [b](x0) = [0 1]x0, [1 1] [a](x0) = [1 2]x0, [0 0 ] [d](x0) = [-& 1 ]x0 orientation: [2 5] [2 3] a(a(d(d(x1)))) = [3 6]x1 >= [3 4]x1 = d(d(b(b(x1)))) [2 4] [0 1 ] c(c(x1)) = [2 4]x1 >= [-& 2 ]x1 = d(d(x1)) problem: a(a(d(d(x1)))) -> d(d(b(b(x1)))) Arctic Interpretation Processor: dimension: 2 interpretation: [0 0 ] [b](x0) = [-& -&]x0, [2 -&] [a](x0) = [-& 1 ]x0, [0 0] [d](x0) = [1 0]x0 orientation: [5 4] [1 1] a(a(d(d(x1)))) = [3 3]x1 >= [1 1]x1 = d(d(b(b(x1)))) problem: Qed