YES Problem: d(a(x1)) -> b(d(x1)) b(x1) -> a(a(a(x1))) c(d(c(x1))) -> a(d(x1)) b(d(d(x1))) -> c(c(d(d(c(x1))))) Proof: Matrix Interpretation Processor: dim=1 interpretation: [c](x0) = x0 + 1, [b](x0) = x0 + 12, [d](x0) = 3x0, [a](x0) = x0 + 4 orientation: d(a(x1)) = 3x1 + 12 >= 3x1 + 12 = b(d(x1)) b(x1) = x1 + 12 >= x1 + 12 = a(a(a(x1))) c(d(c(x1))) = 3x1 + 4 >= 3x1 + 4 = a(d(x1)) b(d(d(x1))) = 9x1 + 12 >= 9x1 + 11 = c(c(d(d(c(x1))))) problem: d(a(x1)) -> b(d(x1)) b(x1) -> a(a(a(x1))) c(d(c(x1))) -> a(d(x1)) Arctic Interpretation Processor: dimension: 2 interpretation: [0 0] [c](x0) = [2 2]x0, [0 0 ] [b](x0) = [-& 3 ]x0, [0 3 ] [d](x0) = [-& -&]x0, [0 -&] [a](x0) = [-& 1 ]x0 orientation: [0 4 ] [0 3 ] d(a(x1)) = [-& -&]x1 >= [-& -&]x1 = b(d(x1)) [0 0 ] [0 -&] b(x1) = [-& 3 ]x1 >= [-& 3 ]x1 = a(a(a(x1))) [5 5] [0 3 ] c(d(c(x1))) = [7 7]x1 >= [-& -&]x1 = a(d(x1)) problem: d(a(x1)) -> b(d(x1)) b(x1) -> a(a(a(x1))) String Reversal Processor: a(d(x1)) -> d(b(x1)) b(x1) -> a(a(a(x1))) Matrix Interpretation Processor: dim=2 interpretation: [1 3] [1] [b](x0) = [0 1]x0 + [0], [1 0] [0] [d](x0) = [0 3]x0 + [1], [1 1] [a](x0) = [0 1]x0 orientation: [1 3] [1] [1 3] [1] a(d(x1)) = [0 3]x1 + [1] >= [0 3]x1 + [1] = d(b(x1)) [1 3] [1] [1 3] b(x1) = [0 1]x1 + [0] >= [0 1]x1 = a(a(a(x1))) problem: a(d(x1)) -> d(b(x1)) Arctic Interpretation Processor: dimension: 3 interpretation: [0 2 -&] [b](x0) = [0 2 1 ]x0 [1 1 1 ] , [0 0 0 ] [d](x0) = [0 0 -&]x0 [-& 0 0 ] , [2 -& 3 ] [a](x0) = [1 1 3 ]x0 [-& 2 3 ] orientation: [2 3 3] [1 2 1] a(d(x1)) = [1 3 3]x1 >= [0 2 1]x1 = d(b(x1)) [2 3 3] [1 2 1] problem: Qed