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Search Results: 1 - 10 of 6452 matches for " Anthony Hams "
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Fast Algorithm for Finding the Eigenvalue Distribution of Very Large Matrices
Anthony Hams,Hans De Raedt
Physics , 2000, DOI: 10.1103/PhysRevE.62.4365
Abstract: A theoretical analysis is given of the equation of motion method, due to Alben et al., to compute the eigenvalue distribution (density of states) of very large matrices. The salient feature of this method is that for matrices of the kind encountered in quantum physics the memory and CPU requirements of this method scale linearly with the dimension of the matrix. We derive a rigorous estimate of the statistical error, supporting earlier observations that the computational efficiency of this approach increases with matrix size. We use this method and an imaginary-time version of it to compute the energy and the specific heat of three different, exactly solvable, spin-1/2 models and compare with the exact results to study the dependence of the statistical errors on sample and matrix size.
Nonperturbative infrared dynamics of three-dimensional QED with a four-fermion interaction
Valery Gusynin,Anthony Hams,Manuel Reenders
Physics , 2000, DOI: 10.1103/PhysRevD.63.045025
Abstract: A non-linear Schwinger-Dyson (SD) equation for the gauge boson propagator of massless QED in one time and two spatial dimensions is studied. It is shown that the nonperturbative solution leads to a nontrivial renormalization-group infrared fixed point quantitatively close to the one found in the leading order of the 1/N expansion, with N the number of fermion flavors. In the gauged Nambu-Jona-Lasinio (GNJL) model an equation for the Yukawa vertex is solved in an approximation given by the one-photon exchange and an analytic expression is derived for the propagator of the scalar fermion-antifermion composites. Subsequently, the mass and width of the scalar composites near the phase transition line are calculated as functions of the four-fermion coupling g and flavor number N. The possible relevance of these results for describing particle-hole excitations, in particular antiferromagnetic correlations, observed in the underdoped cuprates, is briefly discussed.
Quantum Computer Emulator
Hans De Raedt,Anthony Hams,Kristel Michielsen,Koen De Raedt
Physics , 1999, DOI: 10.1016/S0010-4655(00)00132-6
Abstract: We describe a quantum computer emulator for a generic, general purpose quantum computer. This emulator consists of a simulator of the physical realization of the quantum computer and a graphical user interface to program and control the simulator. We illustrate the use of the quantum computer emulator through various implementations of the Deutsch-Jozsa and Grover's database search algorithm.
Feedback Effect on Landau-Zener-Stueckelberg Transitions in Magnetic Systems
Anthony Hams,Hans De Raedt,Seiji Miyashita,Keiji Saito
Physics , 1999, DOI: 10.1103/PhysRevB.62.13880
Abstract: We examine the effect of the dynamics of the internal magnetic field on the staircase magnetization curves observed in large-spin molecular magnets. We show that the size of the magnetization steps depends sensitively on the intermolecular interactions, even if these are very small compared to the intra-molecular couplings.
On the Problem of Programming Quantum Computers
Hans De Raedt,Anthony Hams,Kristel Michielsen,Seiji Miyashita,Keiji Saito
Physics , 2000,
Abstract: We study effects of the physical realization of quantum computers on their logical operation. Through simulation of physical models of quantum computer hardware, we analyse the difficulties that are encountered in programming physical implementations of quantum computers. We discuss the origin of the instabilities of quantum algorithms and explore physical mechanisms to enlarge the region(s) of stable operation.
Programming physical realizations of quantum computers
Hans De Raedt,Kristel Michielsen,Anthony Hams,Seiji Miyashita,Keiji Saito
Physics , 2001,
Abstract: We study effects of the physical realization of quantum computers on their logical operation. Through simulation of physical models of quantum computer hardware, we analyze the difficulties that are encountered in programming physical realizations of quantum computers. Examples of logically identical implementations of the controlled-NOT operation and Grover's database search algorithm are used to demonstrate that the results of a quantum computation are unstable with respect to the physical realization of the quantum computer. We discuss the origin of these instabilities and discuss possibilities to overcome this, for practical purposes, fundamental limitation of quantum computers.
(2+1)-Dimensional QED with Dynamically Massive Fermions in the Vacuum Polarization
V. P. Gusynin,A. H. Hams,M. Reenders
Physics , 1995, DOI: 10.1103/PhysRevD.53.2227
Abstract: We study chiral symmetry breaking in $\rm QED_3$ with $N_f$ flavors of four-component fermions. A closed system of Schwinger-Dyson equations for fermion and photon propagators and the full fermion-photon vertex is proposed, which is consistent with the Ward-Takahashi identity. A simplified version of that set of equations is reduced (in nonlocal gauge) to the equation for a dynamical fermion mass function, where the one-loop vacuum polarization with dynamically massive fermions has been taken into account. The linearized equation for the fermion mass function is analyzed in real space. The analytical solution is compared with the results of numerical calculations of the nonlinear integral equation in momentum space.
A Review of the Impact of Requirements on Software Project Development Using a Control Theoretic Model  [PDF]
Anthony White
Journal of Software Engineering and Applications (JSEA) , 2010, DOI: 10.4236/jsea.2010.39099
Abstract: Software projects have a low success rate in terms of reliability, meeting due dates and working within assigned budgets with only 16% of projects being considered fully successful while Capers Jones has estimated that such projects only have a success rate of 65%. Many of these failures can be attributed to changes in requirements as the project progresses. This paper reviews several System Dynamics models from the literature and analyses the model of Andersson and Karlsson, showing that this model is uncontrollable and unobservable. This leads to a number of is-sues that need to be addressed in requirements acquisition.
A Cayman Islands Perspective on Transborder Insolvencies and Bankruptcies: The Case for Judicial Co-Operation  [PDF]
Anthony Smellie
Beijing Law Review (BLR) , 2011, DOI: 10.4236/blr.2011.24015
Abstract: The freedom of movement of capital in the modern global economy has been indispensable to the development of international corporate enterprise. This paper argues that the judicial and legal institutions of states are as essential to the stability of the global economy as the traditionally heralded international economic channels that have been so carefully crafted globally. In fact, in the sphere of trans-border insolvency and bankruptcy, judicial and legal institutions could be perceived as even more vital, as the vibrancy and the health of global enterprises can be radically challenged and even severely impeded should countries fail to institute universally accepted legislative and judicial codes of practices. The quest for this normative approach has found expression by the United Nations in its development of the UNCITRAL Model Law, a prototype which has since been adopted by twenty-two States. A number of other States, as well, have adopted measures which mirror the cooperation and co-ordination principles of the UNCITRAL Model Law These States all accept that legislative and judicial capacity and competence are essential ingredients in the salutary infusion of mutual confidence, and it is this very shared trust that is the ultimate catalyst for successful resolution of cross-border and other disputes. For Offshore Financial Centres (OFCs), reinforcement of confidence in their Courts in the international arena is perhaps even more highly critical to their sustained roles in today’s globalized economy. This paper outlines the legislative and judicial competencies and roles that have enabled the Cayman Islands, as an example of a key OFC, to emerge as a major player in international cross-border conflict resolution. This discourse also acknowledges the hurdles OFCs have had to overcome in both perceptions and reality in the global marketplace and the increased pressures faced by Courts today in meeting demands of public policy objectives. With specific regard to the Cayman Islands as an example of an effectively functioning OFC, the paper examines the Islands’ insolvency regime, reviews a number of cases demonstrating the efficacy of the approach of the Islands’ Courts, and highlights relevant Cayman Islands’ legislation and orders made pursuant to those laws. This analysis demonstrates how, by implementing through its Courts a public policy model on a par with international codes of conduct, the territory has vouchsafed its ability to render the kind of international judicial assistance that is critical to the fulfilment of the tenets of the
Food and Nutrition Sciences—Open Special Issues: Public Health Nutrition Initiatives  [PDF]
Anthony Fardet
Food and Nutrition Sciences (FNS) , 2013, DOI: 10.4236/fns.2013.410A001
Abstract:

Food and Nutrition Sciences—Open Special Issues: Public Health Nutrition Initiatives


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