One Pebble Versus log(n) Bits
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چکیده
We show that, for any ε > 0, there exists a language accepted in strong ε·log n space by a 2-way deterministic Turing machine working with a single binary worktape, that cannot be accepted in sublogarithmicweak space by any pebble machine (i.e., a 2-way nondeterministic Turing machine with one pebble that can be moved onto the input cells). Moreover, we provide optimal unary lower bounds on the product of space and input head reversals for strong and weak pebble machines accepting nonregular languages.
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تاریخ انتشار 2009