63,341 research outputs found
Single-atom entropy squeezing for two two-level atoms interacting with a single-mode radiation field
In this paper we consider a system of two two-level atoms interacting with a
single-mode quantized electromagnetic field in a lossless resonant cavity via
-photon-transition mechanism. The field and the atoms are initially prepared
in the coherent state and the excited atomic states, respectively. For this
system we investigate the entropy squeezing, the atomic variances, the von
Neumann entropy and the atomic inversions for the single-atom case. We show
that the more the number of the parties in the system the less the amounts of
the nonclassical effects exhibited in the entropy squeezing.
The entropy squeezing can give information on the corresponding von Neumann
entropy. Also the nonclassical effects obtained form the asymmetric atoms are
greater than those obtained form the symmetric atoms. Finally, the entropy
squeezing gives better information than the atomic variances only for the
asymmetric atoms.Comment: 15 pages, 4 figures, comments are most welcom
Phase diagram of an Ising model with competitive interactions on a Husimi tree and its disordered counterpart
We consider an Ising competitive model defined over a triangular Husimi tree
where loops, responsible for an explicit frustration, are even allowed. After a
critical analysis of the phase diagram, in which a ``gas of non interacting
dimers (or spin liquid) - ferro or antiferromagnetic ordered state'' transition
is recognized in the frustrated regions, we introduce the disorder for studying
the spin glass version of the model: the triangular +/- J model. We find out
that, for any finite value of the averaged couplings, the model exhibits always
a phase transition, even in the frustrated regions, where the transition turns
out to be a glassy transition. The analysis of the random model is done by
applying a recently proposed method which allows to derive the upper phase
boundary of a random model through a mapping with a corresponding non random
one.Comment: 19 pages, 11 figures; content change
A Framework for Developing Real-Time OLAP algorithm using Multi-core processing and GPU: Heterogeneous Computing
The overwhelmingly increasing amount of stored data has spurred researchers
seeking different methods in order to optimally take advantage of it which
mostly have faced a response time problem as a result of this enormous size of
data. Most of solutions have suggested materialization as a favourite solution.
However, such a solution cannot attain Real- Time answers anyhow. In this paper
we propose a framework illustrating the barriers and suggested solutions in the
way of achieving Real-Time OLAP answers that are significantly used in decision
support systems and data warehouses
Empirical Investigation on Agile Methods Usage: Issues Identified from Early Adopters in Malaysia
Agile Methods are a set of software practices that can help to produce products faster and at the same time deliver what customers want. Despite the benefits that Agile methods can deliver, however, we found few studies from the Southeast Asia region, particularly Malaysia. As a result, less empirical evidence can be obtained in the country making its implementation harder. To use a new method, experience from other practitioners is critical, which describes what is important, what is possible and what is not possible concerning Agile. We conducted a qualitative study to understand the issues faced by early adopters in Malaysia where Agile methods are still relatively new. The initial study involves 13 participants including project managers, CEOs, founders and software developers from seven organisations. Our study has shown that social and human aspects are important when using Agile methods. While technical aspects have always been considered to exist in software development, we found these factors to be less important when using Agile methods. The results obtained can serve as guidelines to practitioners in the country and the neighbouring regions
On classification and invariants of second order non-parabolic linear partial differential equations in two variables
The paper deals with second order abstract linear partial differential
equations (LPDE) over a partial differential field with two commuting
differential operators. In terms of usual differential equations the main
content can be presented as follows. The classification and invariants problems
for second order LPDEs with respect to transformations where are independent and is
the dependent variable of the LPDE, are considered. Solutions to these problems
are given for different subclasses of non-parabolic LPDE which appear naturally
in the equivalence problem of LPDE. A criterion for reducibility of such LPDE
to LPDE with constant coefficients is offered as well
Sticker systems over monoids
Molecular computing has gained many interests among researchers since Head introduced the first theoretical model for DNA based computation using the splicing operation in 1987. Another model for DNA computing was proposed by using the sticker operation which Adlemanused in his successful experiment for the computation of Hamiltonian paths in a graph: a double stranded DNA sequence is composed by prolonging to the left and to the right a sequence of (single or double) symbols by using given single stranded strings or even more complex dominoes with sticky ends, gluing these ends together with the sticky ends of the current sequence according to a complementarity relation. According to this sticker operation, a language generative mechanism, called a sticker system, can be defined: a set of (incomplete) double-stranded sequences (axioms) and a set of pairs of single or double-stranded complementary sequences are given. The initial sequences are prolonged to the left and to the right by using sequences from the latter set, respectively. The iterations of these prolongations produce โcomputationsโ of possibly arbitrary length. These processes stop when a complete double stranded sequence is obtained. Sticker systems will generate only regular languages without restrictions. Additional restrictions can be imposed on the matching pairs of strands to obtain more powerful languages. Several types of sticker systems are shown to have the same power as regular grammars; one type is found to represent all linear languages whereas another one is proved to be able to represent any recursively enumerable language. The main aim of this research is to introduce and study sticker systems over monoids in which with each sticker operation, an element of a monoid is associated and a complete double stranded sequence is considered to be valid if the computation of the associated elements of the monoid produces the neutral element. Moreover, the sticker system over monoids is defined in this study
The Limit Behavior Of The Trajectories of Dissipative Quadratic Stochastic Operators on Finite Dimensional Simplex
The limit behavior of trajectories of dissipative quadratic stochastic
operators on a finite-dimensional simplex is fully studied. It is shown that
any dissipative quadratic stochastic operator has either unique or infinitely
many fixed points. If dissipative quadratic stochastic operator has a unique
point, it is proven that the operator is regular at this fixed point. If it has
infinitely many fixed points, then it is shown that limit set of the
trajectory is contained in the set of fixed points.Comment: 14 pages, accepted in Difference Eq. App
Renormalization method in -adic -model on the Cayley tree
In this present paper, it is proposed the renormalization techniques in the
investigation of phase transition phenomena in -adic statistical mechanics.
We mainly study -adic \l-model on the Cayley tree of order two. We
consider generalized -adic quasi Gibbs measures depending on parameter
\r\in\bq_p, for the \l-model. Such measures are constructed by means of
certain recurrence equations. These equations define a dynamical system. We
study two regimes with respect to parameters. In the first regime we establish
that the dynamical system has one attractive and two repelling fixed points,
which predicts the existence of a phase transition. In the second regime the
system has two attractive and one neutral fixed points, which predicts the
existence of a quasi phase transition. A main point of this paper is to verify
(i.e. rigorously prove) and confirm that the indicated predictions (via
dynamical systems point of view) are indeed true.
To establish the main result, we employ the methods of -adic analysis, and
therefore, our results are not valid in the real setting.Comment: 18 page
Decoy States and Two Way Quantum Key Distribution Schemes
We study the possible application of the decoy state method on a basic two
way quantum key distribution (QKD) scheme to extend its distance. Noting the
obvious advantage of such a QKD scheme in allowing for single as well as double
photon contributions, we derive relevant lower-bounds on the corresponding
gains in a practical decoy state implementation using two intensities for decoy
states. We work with two different approaches in this vein and compare these
with an ideal infinite decoy state case as well as the simulation of the
original.Comment: Much revised from original manuscript. Accepted for publication in
Optics Communications (some variations may exist in some wordings in the
text
Complete Classification of Two-Dimensional Algebras
A complete classification of two-dimensional algebras over algebraically
closed fields is providedComment: A type-mistake in case, page 7, is correcte
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