Search results for "Theoretical Computer Science"
showing 10 items of 1151 documents
Parallel implementation of the MAGPACK package for the analysis of high-nuclearity spin clusters
2010
Abstract Molecular clusters are formed by a finite number of exchange-coupled paramagnetic centers and they are model systems between molecules and extended solids. In order to simulate their properties and extrapolate to solids, the size of the systems to be treated should be as large as possible. In this context, the use of efficient parallel codes is essential. We present the parallel programs ParAni and ParIso , for anisotropic and isotropic models, that enable the calculation of large energy matrices in parallel and the subsequent computation of the relevant spectral information. The evaluation of the matrix elements is based on the serial package Magpack that uses the irreducible tens…
Cluster Embedding Method with Non-orthogonal Wave Functions for Simulation of Nanodevices
2012
Applicability of cluster embedding method with non-orthogonal wave functions for theoretical study of processes in nanodevices has been studied. Processes in nanodevices are treated in the framework of time-dependent DFT. We demonstrate that our cluster embedding method is compatible with DFT Kohn-Sham method and quantum transport theory based on time-dependent DFT. We conclude that the approach for electric current calculation developed for orthogonal wave functions may be applied for non-orthogonal wave functions if we transform the initial equations assuming that overlaps are small (S2 ≪ S).
Theory of Computation, Fuzziness and a physics of the immaterial
2013
In this paper we advance three clear-cut proposals as a contribution to the discussion on the role of notions of Computation and Fuzziness as a bridge between Hard and Soft Sciences. We suggest that an important difference between the two great fami- lies of science lies in their subject or research having a grounding in nature or not, and that Theory of Computation is a glaring exception to this classifi- cation, being a textbook hard science but dealing with the immaterial. We further advance that such unicity is strongly connected with Church-Turing thesis, and discuss about the role of Computation and Fuzziness as pillars of immaterial sciences
Recipes for successful simulation
1997
A Collection of recipes could be called a cookbook, but Daan Frenkel and Berend Smit's book achieves more than that. By explaining the physics behind the algorithms, the authors let you learn how molecular dynamics and Monte Carlo simulation methods work, how to apply these methods in a sensible way and what information can be extracted from them. Although computer simulation, lying between analytical theory and experiment, is now regarded as the third branch science, it is still viewed with skepticism some researchers precisely because of this interdisciplinary character.
Quantum Computing: A Way to Break Complexity?
2003
The perception of time is given by the happening of some events that determines a variation in the state of the observed system. In this sense a computation, i.e. a set of well defined transformations that, starting from an initial state (the input) brings to a final state (the output), can be considered a time generator. Each ticking of the clock corresponds to the computer changes of its states. The speed of computation leads to a different perception of time as well as traveling by airplanes changed the perception of spatial distances.
Information encoding of a qubit into a multilevel environment
2010
I consider the interaction of a small quantum system (a qubit) with a structured environment consisting of many levels. The qubit will experience a decoherence process, which implies that part of its initial information will be encoded into correlations between system and environment. I investigate how this information is distributed on a given subset of levels as a function of its size, using the mutual information between both entities, in the spirit of the partial-information plots studied by Zurek and co-workers. In this case we can observe some differences, which arise from the fact that I am partitioning just one quantum system and not a collection of them. However, some similar featu…
SEA presidential address: Group connectivity and cooperation
2011
A model-free methodology is used for the first time to estimate a daily volatility index (VIBEX-NEW) for the Spanish financial market.We use a public data set of daily option prices to compute this index and showthat daily changes in VIBEXNEW display a negative, tight contemporaneous relationship with IBEX daily returns, contrary to other common volatility indicators, as an implied volatility indicator or a GARCH(1,1) conditional volatility model. This relationship is approximately symmetric to the sign on VIBEX-NEW changes and asymmetric to the IBEX-35 returns sign, which make it clearly a suitable volatility index for the Spanish stock market. We also examine the relationship between curr…
The impact of grain size on the efficiency of embedded SIMD image processing architectures
2004
Pixel-per-processing element (PPE) ratio-the amount of image data directly mapped to each processing element-has a significant impact on the area and energy efficiency of embedded SIMD architectures for image processing applications. This paper quantitatively evaluates the impact of PPE ratio on system performance and efficiency for focal-plane SIMD image processing architectures by comparing throughput, area efficiency, and energy efficiency for a range of common application kernels using architectural and workload simulation. While the impact of grain size is affected by the mix of executed instructions within an application program, the most efficient PPE ratio often does not occur at PE…
A Common Characterization of Finite Projective Spaces and Affine Planes
1981
Let S be a finite linear space for which there is a non-negative integer s such that for any two disjoint lines L, L' of S and any point p outside L and L' there are exactly s lines through p intersecting the two lines L and L'. We prove that one of the following possibilities occurs: (i) S is a generalized projective space, and if the dimension of S is at least 4, then any line of S has exactly two points. (ii) S is an affine plane, an affine plane with one improper point, or a punctured projective plane. (iii) S is the Fano-quasi -plane.
Spatiality for formal topologies
2007
We define what it means for a formal topology to be spatial, and investigate properties related to spatiality both in general and in examples.