2,550 research outputs found
Computational efficiency of dissolution rules in membrane systems
Trading (in polynomial time) space for time in the framework of membrane systems is not sufficient to
efficiently solve computationally hard problems. On the one hand, an exponential number of objects
generated in polynomial time is not sufficient to solve NP-complete problems in polynomial time.
On the other hand, when an exponential number of membranes is created and used as workspace, the
situation is very different. Two operations in P systems (membrane division and membrane creation)
capable of constructing an exponential number of membranes in linear time are studied in this paper.
NP-complete problems can be solved in polynomial time using P systems with active membranes
and with polarizations, but when electrical charges are not used, then dissolution rules turn out to
be very important. We show that in the framework of P systems with active membranes but without
polarizations and in the framework of P systems with membrane creation, dissolution rules play a
crucial role from the computational efficiency point of view.Ministerio de Educación y Ciencia TIN2005-09345-C04-0
New applications for an old tool
First, the dependency graph technique, not so far from its current application,
was developed trying to nd the shortest computations for membrane systems
solving instances of SAT. Certain families of membrane systems have been demonstrated
to be non-effcient by means of the reduction of nding an accepting computation (respectively,
rejecting computation) to the problem of reaching from a node of the dependency
graph to another one.
In this paper, a novel application to this technique is explained. Supposing that a
problem can be solved by means of a kind of membrane systems leads to a contradiction
by means of using the dependency graph as a reasoning method. In this case, it is demonstrated
that a single system without dissolution, polarizations and cooperation cannot
distinguish a single object from more than one object.
An extended version of this work will be presented in the 20th International Conference
on Membrane Computing.Ministerio de Industria, Economía y Competitividad TIN2017-89842-
Far-infrared polarimetry from the Stratospheric Observatory for Infrared Astronomy
Multi-wavelength imaging polarimetry at far-infrared wavelengths has proven
to be an excellent tool for studying the physical properties of dust, molecular
clouds, and magnetic fields in the interstellar medium. Although these
wavelengths are only observable from airborne or space-based platforms, no
first-generation instrument for the Stratospheric Observatory for Infrared
Astronomy (SOFIA) is presently designed with polarimetric capabilities. We
study several options for upgrading the High-resolution Airborne Wideband
Camera (HAWC) to a sensitive FIR polarimeter. HAWC is a 12 x 32 pixel bolometer
camera designed to cover the 53 - 215 micron spectral range in 4 colors, all at
diffraction-limited resolution (5 - 21 arcsec). Upgrade options include: (1) an
external set of optics which modulates the polarization state of the incoming
radiation before entering the cryostat window; (2) internal polarizing optics;
and (3) a replacement of the current detector array with two state-of-the-art
superconducting bolometer arrays, an upgrade of the HAWC camera as well as
polarimeter. We discuss a range of science studies which will be possible with
these upgrades including magnetic fields in star-forming regions and galaxies
and the wavelength-dependence of polarization.Comment: 12 pages, 5 figure
A Computational Complexity Theory in Membrane Computing
In this paper, a computational complexity theory within the framework
of Membrane Computing is introduced. Polynomial complexity classes associated with
di erent models of cell-like and tissue-like membrane systems are de ned and the most
relevant results obtained so far are presented. Many attractive characterizations of P 6=
NP conjecture within the framework of a bio-inspired and non-conventional computing
model are deduced.Ministerio de Educación y Ciencia TIN2006-13425Junta de Andalucía P08–TIC-0420
Polarizationless P Systems with Active Membranes Working in the Minimally Parallel Mode
We investigate the computing power and the efficiency of P systems with
active membranes without polarizations, working in the minimally parallel mode. We
prove that such systems are computationally complete and able to solve NP-complete
problems even when the rules are of a restricted form, e.g., for establishing computational
completeness we only need rules handling single objects and no division of non-elementary
membranes is usedMinisterio de Educación y Ciencia TIN2005-09345-C04-01Junta de Andalucía TIC 58
Solving SAT with Antimatter in Membrane Computing
The set of NP-complete problems is split into weakly and strongly NP-
complete ones. The di erence consists in the in
uence of the encoding scheme of the
input. In the case of weakly NP-complete problems, the intractability depends on the
encoding scheme, whereas in the case of strongly NP-complete problems the problem
is intractable even if all data are encoded in a unary way. The reference for strongly
NP-complete problems is the Satis ability Problem (the SAT problem). In this paper,
we provide a uniform family of P systems with active membranes which solves SAT {
without polarizations, without dissolution, with division for elementary membranes and
with matter/antimatter annihilation. To the best of our knowledge, it is the rst solution
to a strongly NP-complete problem in this P system model.Ministerio de Economía y Competitividad TIN2012-3743
Uniform Solution to QSAT Using Polarizationless Active Membranes
It is known that the satisfiability problem (SAT) can be solved a semi-
uniform family of deterministic polarizationless P systems with active membranes with
non-elementary membrane division. We present a double improvement of this result by
showing that the satisfiability of a quantified boolean formula (QSAT) can be solved by a
uniform family of P systems of the same kind.Ministerio de Educación y Ciencia TIN2005-09345-C04-0
Minimal Parallelism and Number of Membrane Polarizations
It is known that the satisfiability problem (SAT) can be efficiently solved by a uniform family of P systems with active membranes that have two polarizations working in a maximally parallel way. We study P systems with active membranes without non-elementary membrane division, working in minimally parallel way. The main question we address is what number of polarizations is sufficient for an efficient computation depending on the types of rules used.In particular, we show that it is enough to have four polarizations, sequential evolution rules changing polarizations, polarizationless non-elementary membrane division rules and polarizationless rules of sending an object out. The same problem is solved with the standard evolution rules, rules of sending an object out and polarizationless non-elementary membrane division rules, with six polarizations. It is an open question whether these numbers are optimal
Complexity aspects of polarizationless membrane systems
We investigate polarizationless P systems with active membranes working in
maximally parallel manner, which do not make use of evolution or communication rules, in
order to find which features are sufficient to efficiently solve computationally hard problems.
We show that such systems are able to solve the PSPACE-complete problem
QUANTIFIED 3-SAT, provided that non-elementary membrane division is controlled by the
presence of a (possibly non-elementary) membrane.Ministerio de Educación y Ciencia TIN2006-13425Junta de Andalucía TIC-58
Dependency Graph Technique Revisited
The dependency graph technique was initially thought as a method to find
short paths in the computation tree of a membrane system using weak metrics. It could be
used to obtain reasonably fast SAT-solvers, capable of competing with the ones available in
the literature. Later on, they were used as a method to demonstrate the non-efficiency of
some membrane systems, capturing the dynamics of the systems by a static directed graph
structure. Recently, the dependency graphs have also been used to establish negative
results in Membrane Computing. Specifically, in this work, demonstrating the inability
of a kind of membrane system to solve some decision problems efficiently by means of a
single system.Ministerio de Economía, Industria y Competitividad TIN2017-89842-
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