Single-tape reset machines
Some modifications of auxiliary pushdown automata
Strategies to scan pictures with automata based on Wang tiles
Wang automata are devices for picture language recognition recently introduced by us, which characterize the class REC of recognizable picture languages. Thus, Wang automata are equivalent to tiling systems or online tessellation acceptors, and are based like Wang systems on labeled Wang tiles. The present work focus on scanning strategies, to prove that the ones Wang automata are based on are those following four kinds of movements: boustrophedonic, “L-like”, “U-like”, and spirals.
Strategies to scan pictures with automata based on Wang tiles
Wang automata are devices for picture language recognition recently introduced by us, which characterize the class REC of recognizable picture languages. Thus, Wang automata are equivalent to tiling systems or online tessellation acceptors, and are based like Wang systems on labeled Wang tiles. The present work focus on scanning strategies, to prove that the ones Wang automata are based on are those following four kinds of movements: boustrophedonic, “L-like”, “U-like”, and spirals.
String Assembling Systems
We introduce and investigate string assembling systems which form a computational model that generates strings from copies out of a finite set of assembly units. The underlying mechanism is based on piecewise assembly of a double-stranded sequence of symbols, where the upper and lower strand have to match. The generation is additionally controlled by the requirement that the first symbol of a unit has to be the same as the last symbol of the strand generated so far, as well as by the distinction...
String Assembling Systems
We introduce and investigate string assembling systems which form a computational model that generates strings from copies out of a finite set of assembly units. The underlying mechanism is based on piecewise assembly of a double-stranded sequence of symbols, where the upper and lower strand have to match. The generation is additionally controlled by the requirement that the first symbol of a unit has to be the same as the last symbol of the strand generated so far, as well as by the distinction...
Sublogarithmic -space is not closed under complement and other separation results
Superiority of one-way and realtime quantum machines∗∗∗
In automata theory, quantum computation has been widely examined for finite state machines, known as quantum finite automata (QFAs), and less attention has been given to QFAs augmented with counters or stacks. In this paper, we focus on such generalizations of QFAs where the input head operates in one-way or realtime mode, and present some new results regarding their superiority over their classical counterparts. Our first result is about the nondeterministic...
Superiority of one-way and realtime quantum machines
In automata theory, quantum computation has been widely examined for finite state machines, known as quantum finite automata (QFAs), and less attention has been given to QFAs augmented with counters or stacks. In this paper, we focus on such generalizations of QFAs where the input head operates in one-way or realtime mode, and present some new results regarding their superiority over their classical counterparts. Our first result is about the nondeterministic acceptance mode: Each quantum model...
Superiority of one-way and realtime quantum machines∗∗∗
In automata theory, quantum computation has been widely examined for finite state machines, known as quantum finite automata (QFAs), and less attention has been given to QFAs augmented with counters or stacks. In this paper, we focus on such generalizations of QFAs where the input head operates in one-way or realtime mode, and present some new results regarding their superiority over their classical counterparts. Our first result is about the nondeterministic...
Systolic tree acceptors
The difference and truth-table hierarchies for NP
The helping hierarchy
Schöning [14] introduced a notion of helping and suggested the study of the class of the languages that can be helped by oracles in a given class . Later, Ko [12], in order to study the connections between helping and “witness searching”, introduced the notion of self-helping for languages. We extend this notion to classes of languages and show that there exists a self-helping class that we call which contains all the self-helping classes. We introduce the Helping hierarchy whose levels are...
The Helping Hierarchy
Schöning [14] introduced a notion of helping and suggested the study of the class of the languages that can be helped by oracles in a given class . Later, Ko [12], in order to study the connections between helping and "witness searching" , introduced the notion of self-helping for languages. We extend this notion to classes of languages and show that there exists a self-helping class that we call SH which contains all the self-helping classes. We introduce the Helping hierarchy whose levels...
The laterality problem for non-erasing Turing machines on is completely solved
The role of rudimentary relations in complexity theory
The second machine class 2, an encyclopedic view on the parallel computation thesis
Threshold circuits for iterated matrix product and powering
Threshold Circuits for Iterated Matrix Product and Powering
The complexity of computing, via threshold circuits, the iterated product and powering of fixed-dimension matrices with integer or rational entries is studied. We call these two problems and , respectively, for short. We prove that: (i) For , does not belong to , unless .newline (ii) For stochastic matrices : belongs to while, for , does not belong to , unless . (iii) For any k, belongs to .
Time and space complexity of reversible pebbling
This paper investigates one possible model of reversible computations, an important paradigm in the context of quantum computing. Introduced by Bennett, a reversible pebble game is an abstraction of reversible computation that allows to examine the space and time complexity of various classes of problems. We present a technique for proving lower and upper bounds on time and space complexity for several types of graphs. Using this technique we show that the time needed to achieve optimal space for...