Takizawa, Kenji; Tezduyar, Tayfun E.; Otoguro, Yuto
2018-04-01
Stabilized methods, which have been very common in flow computations for many years, typically involve stabilization parameters, and discontinuity-capturing (DC) parameters if the method is supplemented with a DC term. Various well-performing stabilization and DC parameters have been introduced for stabilized space-time (ST) computational methods in the context of the advection-diffusion equation and the Navier-Stokes equations of incompressible and compressible flows. These parameters were all originally intended for finite element discretization but quite often used also for isogeometric discretization. The stabilization and DC parameters we present here for ST computations are in the context of the advection-diffusion equation and the Navier-Stokes equations of incompressible flows, target isogeometric discretization, and are also applicable to finite element discretization. The parameters are based on a direction-dependent element length expression. The expression is outcome of an easy to understand derivation. The key components of the derivation are mapping the direction vector from the physical ST element to the parent ST element, accounting for the discretization spacing along each of the parametric coordinates, and mapping what we have in the parent element back to the physical element. The test computations we present for pure-advection cases show that the parameters proposed result in good solution profiles.
Scalable space-time adaptive simulation tools for computational electrocardiology
Krause, Dorian; Krause, Rolf
2013-01-01
This work is concerned with the development of computational tools for the solution of reaction-diffusion equations from the field of computational electrocardiology. We designed lightweight spatially and space-time adaptive schemes for large-scale parallel simulations. We propose two different adaptive schemes based on locally structured meshes, managed either via a conforming coarse tessellation or a forest of shallow trees. A crucial ingredient of our approach is a non-conforming morta...
On the stability of scalar-vacuum space-times
Energy Technology Data Exchange (ETDEWEB)
Bronnikov, K.A. [VNIIMS, Center for Gravitation and Fundamental Metrology, Moscow (Russian Federation); PFUR, Institute of Gravitation and Cosmology, Moscow (Russian Federation); Fabris, J.C. [Universidade Federal do Espirito Santo, Departamento de Fisica, Vitoria, ES (Brazil); Zhidenko, A. [Universidade Federal do ABC, Centro de Matematica, Computacao e Cognicao, Santo Andre, SP (Brazil)
2011-11-15
We study the stability of static, spherically symmetric solutions to the Einstein equations with a scalar field as the source. We describe a general methodology of studying small radial perturbations of scalar-vacuum configurations with arbitrary potentials V({phi}), and in particular space-times with throats (including wormholes), which are possible if the scalar is phantom. At such a throat, the effective potential for perturbations V{sub eff} has a positive pole (a potential wall) that prevents a complete perturbation analysis. We show that, generically, (i) V{sub eff} has precisely the form required for regularization by the known S-deformation method, and (ii) a solution with the regularized potential leads to regular scalar field and metric perturbations of the initial configuration. The well-known conformal mappings make these results also applicable to scalar-tensor and f(R) theories of gravity. As a particular example, we prove the instability of all static solutions with both normal and phantom scalars and V({phi}){identical_to}0 under spherical perturbations. We thus confirm the previous results on the unstable nature of anti-Fisher wormholes and Fisher's singular solution and prove the instability of other branches of these solutions including the anti-Fisher ''cold black holes''. (orig.)
Stability of black holes and solitons in Anti-de Sitter space-time
Energy Technology Data Exchange (ETDEWEB)
Hartmann, Betti
2014-06-15
The stability of black holes and solitons in d-dimensional Anti-de Sitter (AdS{sub d}) space-time against scalar field condensation is discussed. The resulting solutions are “hairy” black holes and solitons, respectively. In particular, we will discuss static black hole solutions with hyperbolic, flat and spherical horizon topology and emphasize that two different type of instabilities exist depending on whether the scalar field is charged or uncharged, respectively. We will also discuss the influence of Gauss-Bonnet curvature terms. The results have applications within the AdS/CFT correspondence and describe e.g. holographic insulator/conductor/superconductor phase transitions.
International Nuclear Information System (INIS)
Dubois, Daniel M.
2000-01-01
This paper is a continuation of our preceding paper dealing with computational derivation of the Klein-Gordon quantum relativist equation and the Schroedinger quantum equation with forward and backward space-time shifts. The first part introduces forward and backward derivatives for discrete and continuous systems. Generalized complex discrete and continuous derivatives are deduced. The second part deduces the Klein-Gordon equation from the space-time complex continuous derivatives. These derivatives take into account forward-backward space-time shifts related to an internal phase velocity u. The internal group velocity v is related to the speed of light u.v=c 2 and to the external group and phase velocities u.v=v g .v p . Without time shift, the Schroedinger equation is deduced, with a supplementary term, which could represent a reference potential. The third part deduces the Quantum Relativist Klein-Gordon equation for a particle in an electromagnetic field
Computer-games for gravitational wave science outreach: Black Hole Pong and Space Time Quest
International Nuclear Information System (INIS)
Carbone, L; Bond, C; Brown, D; Brückner, F; Grover, K; Lodhia, D; Mingarelli, C M F; Fulda, P; Smith, R J E; Unwin, R; Vecchio, A; Wang, M; Whalley, L; Freise, A
2012-01-01
We have established a program aimed at developing computer applications and web applets to be used for educational purposes as well as gravitational wave outreach activities. These applications and applets teach gravitational wave physics and technology. The computer programs are generated in collaboration with undergraduates and summer students as part of our teaching activities, and are freely distributed on a dedicated website. As part of this program, we have developed two computer-games related to gravitational wave science: 'Black Hole Pong' and 'Space Time Quest'. In this article we present an overview of our computer related outreach activities and discuss the games and their educational aspects, and report on some positive feedback received.
Efficient Geo-Computational Algorithms for Constructing Space-Time Prisms in Road Networks
Directory of Open Access Journals (Sweden)
Hui-Ping Chen
2016-11-01
Full Text Available The Space-time prism (STP is a key concept in time geography for analyzing human activity-travel behavior under various Space-time constraints. Most existing time-geographic studies use a straightforward algorithm to construct STPs in road networks by using two one-to-all shortest path searches. However, this straightforward algorithm can introduce considerable computational overhead, given the fact that accessible links in a STP are generally a small portion of the whole network. To address this issue, an efficient geo-computational algorithm, called NTP-A*, is proposed. The proposed NTP-A* algorithm employs the A* and branch-and-bound techniques to discard inaccessible links during two shortest path searches, and thereby improves the STP construction performance. Comprehensive computational experiments are carried out to demonstrate the computational advantage of the proposed algorithm. Several implementation techniques, including the label-correcting technique and the hybrid link-node labeling technique, are discussed and analyzed. Experimental results show that the proposed NTP-A* algorithm can significantly improve STP construction performance in large-scale road networks by a factor of 100, compared with existing algorithms.
Stability of geodesic imcompleteness for Robertson-Walker space-times
International Nuclear Information System (INIS)
Beem, J.K.
1981-01-01
Let (M,g) be a Lorentzian warped product space-time M = (a, b) X H,g = -dt 2 x fh, where -infinity -infinity and (H,h) is homogeneous, then the past incompleteness of every timelike geodesic of (M,g) is stable under small C 0 perturbations in the space Lor(M) of Lorentzian metrics for M. Also it is shown that if (H,h) is isotropic and (M,g) contains a past-inextendible, past-incomplete null geodesic, then the past incompleteness of all null geodesics is stable under small C 1 perturbations in Lor(M). Given either the isotropy or homogeneity of the Riemannian factor, the background space-time (M,g) is globally hyperbolic. The results of this paper, in particular, answer a question raised by D. Lerner for big bang Robertson-Walker cosmological models affirmatively. (author)
Multiscale Space-Time Computational Methods for Fluid-Structure Interactions
2015-09-13
thermo-fluid analysis of a ground vehicle and its tires ST-SI Computational Analysis of a Vertical - Axis Wind Turbine We have successfully...of a vertical - axis wind turbine . Multiscale Compressible-Flow Computation with Particle Tracking We have successfully tested the multiscale...Tezduyar, Spenser McIntyre, Nikolay Kostov, Ryan Kolesar, Casey Habluetzel. Space–time VMS computation of wind - turbine rotor and tower aerodynamics
International Nuclear Information System (INIS)
Aoyama, Tatsumi; Kawai, Hikaru; Shibusa, Yuuichiro
2006-01-01
We investigate the origin of our four-dimensional space-time by considering dynamical aspects of the IIB matrix model using the improved mean field approximation. Previous works have focused on the specific choices of configurations as ansatz which preserve SO(d) rotational symmetry. In this report, an extended ansatz is proposed and examined up to a third-order approximation which includes both the SO(4) ansatz and the SO(7) ansatz in their respective limits. From the solutions of the self-consistency condition represented by the extrema of the free energy of the system, it is found that some of the solutions found in the SO(4) or SO(7) ansatz disappear in the extended ansatz. This implies that the extension of ansatz can be used to distinguish stable solutions from unstable solutions. It is also found that there is a non-trivial accumulation of extrema including the SO(4)-preserving solution, which may lead to the formation of a plateau. (author)
International Nuclear Information System (INIS)
Rouet, J.L.; Feix, M.R.
1996-01-01
The test particle picture is a central theory of weakly correlated plasma. While experiments and computer experiments have confirmed the validity of this theory at thermal equilibrium, the extension to meta-equilibrium distributions presents interesting and intriguing points connected to the under or over-population of the tail of these distributions (high velocity) which have not yet been tested. Moreover, the general dynamical Debye cloud (which is a generalization of the static Debye cloud supposing a plasma at thermal equilibrium and a test particle of zero velocity) for any test particle velocity and three typical velocity distributions (equilibrium plus two meta-equilibriums) are presented. The simulations deal with a one-dimensional two-component plasma and, moreover, the relevance of the check for real three-dimensional plasma is outlined. Two kinds of results are presented: the dynamical cloud itself and the more usual density (or energy) fluctuation spectrums. Special attention is paid to the behavior of long wavelengths which needs long systems with very small graininess effects and, consequently, sizable computation efforts. Finally, the divergence or absence of energy in the small wave numbers connected to the excess or lack of fast particles of the two above mentioned meta-equilibrium is exhibited. copyright 1996 American Institute of Physics
Numerical Computation of Detonation Stability
Kabanov, Dmitry
2018-06-03
Detonation is a supersonic mode of combustion that is modeled by a system of conservation laws of compressible fluid mechanics coupled with the equations describing thermodynamic and chemical properties of the fluid. Mathematically, these governing equations admit steady-state travelling-wave solutions consisting of a leading shock wave followed by a reaction zone. However, such solutions are often unstable to perturbations and rarely observed in laboratory experiments. The goal of this work is to study the stability of travelling-wave solutions of detonation models by the following novel approach. We linearize the governing equations about a base travelling-wave solution and solve the resultant linearized problem using high-order numerical methods. The results of these computations are postprocessed using dynamic mode decomposition to extract growth rates and frequencies of the perturbations and predict stability of travelling-wave solutions to infinitesimal perturbations. We apply this approach to two models based on the reactive Euler equations for perfect gases. For the first model with a one-step reaction mechanism, we find agreement of our results with the results of normal-mode analysis. For the second model with a two-step mechanism, we find that both types of admissible travelling-wave solutions exhibit the same stability spectra. Then we investigate the Fickett’s detonation analogue coupled with a particular reaction-rate expression. In addition to the linear stability analysis of this model, we demonstrate that it exhibits rich nonlinear dynamics with multiple bifurcations and chaotic behavior.
Andonov, Zdravko
This R&D represent innovative multidimensional 6D-N(6n)D Space-Time (S-T) Methodology, 6D-6nD Coordinate Systems, 6D Equations, new 6D strategy and technology for development of Planetary Space Sciences, S-T Data Management and S-T Computational To-mography. . . The Methodology is actual for brain new RS Microwaves' Satellites and Compu-tational Tomography Systems development, aimed to defense sustainable Earth, Moon, & Sun System evolution. Especially, extremely important are innovations for monitoring and protec-tion of strategic threelateral system H-OH-H2O Hydrogen, Hydroxyl and Water), correspond-ing to RS VHRS (Very High Resolution Systems) of 1.420-1.657-22.089GHz microwaves. . . One of the Greatest Paradox and Challenge of World Science is the "transformation" of J. L. Lagrange 4D Space-Time (S-T) System to H. Minkovski 4D S-T System (O-X,Y,Z,icT) for Einstein's "Theory of Relativity". As a global result: -In contemporary Advanced Space Sciences there is not real adequate 4D-6D Space-Time Coordinate System and 6D Advanced Cosmos Strategy & Methodology for Multidimensional and Multitemporal Space-Time Data Management and Tomography. . . That's one of the top actual S-T Problems. Simple and optimal nD S-T Methodology discovery is extremely important for all Universities' Space Sci-ences' Education Programs, for advances in space research and especially -for all young Space Scientists R&D!... The top ten 21-Century Challenges ahead of Planetary and Space Sciences, Space Data Management and Computational Space Tomography, important for successfully de-velopment of Young Scientist Generations, are following: 1. R&D of W. R. Hamilton General Idea for transformation all Space Sciences to Time Sciences, beginning with 6D Eukonal for 6D anisotropic mediums & velocities. Development of IERS Earth & Space Systems (VLBI; LLR; GPS; SLR; DORIS Etc.) for Planetary-Space Data Management & Computational Planetary & Space Tomography. 2. R&D of S. W. Hawking Paradigm for 2D
Schrödinger, Erwin
1985-01-01
In response to repeated requests this classic book on space-time structure by Professor Erwin Schrödinger is now available in the Cambridge Science Classics series. First published in 1950, and reprinted in 1954 and 1960, this lucid and profound exposition of Einstein's 1915 theory of gravitation still provides valuable reading for students and research workers in the field.
International Nuclear Information System (INIS)
Lucas, J.R.
1984-01-01
Originating from lectures given to first year undergraduates reading physics and philosophy or mathematics and philosophy, formal logic is applied to issues and the elucidation of problems in space, time and causality. No special knowledge of relativity theory or quantum mechanics is needed. The text is interspersed with exercises and each chapter is preceded by a suggested 'preliminary reading' and followed by 'further reading' references. (U.K.)
Computationally designed libraries for rapid enzyme stabilization
Wijma, Hein J.; Floor, Robert J.; Jekel, Peter A.; Baker, David; Marrink, Siewert J.; Janssen, Dick B.
The ability to engineer enzymes and other proteins to any desired stability would have wide-ranging applications. Here, we demonstrate that computational design of a library with chemically diverse stabilizing mutations allows the engineering of drastically stabilized and fully functional variants
Numerical Computation of Detonation Stability
Kabanov, Dmitry
2018-01-01
Then we investigate the Fickett’s detonation analogue coupled with a particular reaction-rate expression. In addition to the linear stability analysis of this model, we demonstrate that it exhibits rich nonlinear dynamics with multiple bifurcations and chaotic behavior.
Braverman, Amy; Nguyen, Hai; Olsen, Edward; Cressie, Noel
2011-01-01
Space-time Data Fusion (STDF) is a methodology for combing heterogeneous remote sensing data to optimally estimate the true values of a geophysical field of interest, and obtain uncertainties for those estimates. The input data sets may have different observing characteristics including different footprints, spatial resolutions and fields of view, orbit cycles, biases, and noise characteristics. Despite these differences all observed data can be linked to the underlying field, and therefore the each other, by a statistical model. Differences in footprints and other geometric characteristics are accounted for by parameterizing pixel-level remote sensing observations as spatial integrals of true field values lying within pixel boundaries, plus measurement error. Both spatial and temporal correlations in the true field and in the observations are estimated and incorporated through the use of a space-time random effects (STRE) model. Once the models parameters are estimated, we use it to derive expressions for optimal (minimum mean squared error and unbiased) estimates of the true field at any arbitrary location of interest, computed from the observations. Standard errors of these estimates are also produced, allowing confidence intervals to be constructed. The procedure is carried out on a fine spatial grid to approximate a continuous field. We demonstrate STDF by applying it to the problem of estimating CO2 concentration in the lower-atmosphere using data from the Atmospheric Infrared Sounder (AIRS) and the Japanese Greenhouse Gasses Observing Satellite (GOSAT) over one year for the continental US.
Hestenes, David
2015-01-01
This small book started a profound revolution in the development of mathematical physics, one which has reached many working physicists already, and which stands poised to bring about far-reaching change in the future. At its heart is the use of Clifford algebra to unify otherwise disparate mathematical languages, particularly those of spinors, quaternions, tensors and differential forms. It provides a unified approach covering all these areas and thus leads to a very efficient ‘toolkit’ for use in physical problems including quantum mechanics, classical mechanics, electromagnetism and relativity (both special and general) – only one mathematical system needs to be learned and understood, and one can use it at levels which extend right through to current research topics in each of these areas. These same techniques, in the form of the ‘Geometric Algebra’, can be applied in many areas of engineering, robotics and computer science, with no changes necessary – it is the same underlying mathematics, a...
Space-Time Crystal and Space-Time Group.
Xu, Shenglong; Wu, Congjun
2018-03-02
Crystal structures and the Bloch theorem play a fundamental role in condensed matter physics. We extend the static crystal to the dynamic "space-time" crystal characterized by the general intertwined space-time periodicities in D+1 dimensions, which include both the static crystal and the Floquet crystal as special cases. A new group structure dubbed a "space-time" group is constructed to describe the discrete symmetries of a space-time crystal. Compared to space and magnetic groups, the space-time group is augmented by "time-screw" rotations and "time-glide" reflections involving fractional translations along the time direction. A complete classification of the 13 space-time groups in one-plus-one dimensions (1+1D) is performed. The Kramers-type degeneracy can arise from the glide time-reversal symmetry without the half-integer spinor structure, which constrains the winding number patterns of spectral dispersions. In 2+1D, nonsymmorphic space-time symmetries enforce spectral degeneracies, leading to protected Floquet semimetal states. We provide a general framework for further studying topological properties of the (D+1)-dimensional space-time crystal.
Statistical geometry and space-time
International Nuclear Information System (INIS)
Grauert, H.
1976-01-01
In this paper I try to construct a mathematical tool by which the full structure of Lorentz geometry to space time can be given, but beyond that the background - to speak pictorially - the subsoil for electromagnetic and matter waves, too. The tool could be useful to describe the connections between various particles, electromagnetism and gravity and to compute observables which were not theoretically related, up to now. Moreover, the tool is simpler than the Riemann tensor: it consists just of a set S of line segments in space time, briefly speaking. (orig.) [de
Numerical computation of homogeneous slope stability.
Xiao, Shuangshuang; Li, Kemin; Ding, Xiaohua; Liu, Tong
2015-01-01
To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS) to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM) and particle swarm optimization algorithm (PSO) to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759) were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS).
Numerical Computation of Homogeneous Slope Stability
Directory of Open Access Journals (Sweden)
Shuangshuang Xiao
2015-01-01
Full Text Available To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM and particle swarm optimization algorithm (PSO to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759 were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS.
Jing, Yindi
2014-01-01
Distributed Space-Time Coding (DSTC) is a cooperative relaying scheme that enables high reliability in wireless networks. This brief presents the basic concept of DSTC, its achievable performance, generalizations, code design, and differential use. Recent results on training design and channel estimation for DSTC and the performance of training-based DSTC are also discussed.
Directory of Open Access Journals (Sweden)
Ronald E. Meyers
2015-03-01
Full Text Available We report on an experimental and theoretical investigation of quantum imaging where the images are stored in both space and time. Ghost images of remote objects are produced with either one or two beams of chaotic laser light generated by a rotating ground glass and two sensors measuring the reference field and bucket field at different space-time points. We further observe that the ghost images translate depending on the time delay between the sensor measurements. The ghost imaging experiments are performed both with and without turbulence. A discussion of the physics of the space-time imaging is presented in terms of quantum nonlocal two-photon analysis to support the experimental results. The theoretical model includes certain phase factors of the rotating ground glass. These experiments demonstrated a means to investigate the time and space aspects of ghost imaging and showed that ghost imaging contains more information per measured photon than was previously recognized where multiple ghost images are stored within the same ghost imaging data sets. This suggests new pathways to explore quantum information stored not only in multi-photon coincidence information but also in time delayed multi-photon interference. The research is applicable to making enhanced space-time quantum images and videos of moving objects where the images are stored in both space and time.
Harmonic Balance Computations of Fan Aeroelastic Stability
Bakhle, Milind A.; Reddy, T. S. R.
2010-01-01
A harmonic balance (HB) aeroelastic analysis, which has been recently developed, was used to determine the aeroelastic stability (flutter) characteristics of an experimental fan. To assess the numerical accuracy of this HB aeroelastic analysis, a time-domain aeroelastic analysis was also used to determine the aeroelastic stability characteristics of the same fan. Both of these three-dimensional analysis codes model the unsteady flowfield due to blade vibrations using the Reynolds-averaged Navier-Stokes (RANS) equations. In the HB analysis, the unsteady flow equations are converted to a HB form and solved using a pseudo-time marching method. In the time-domain analysis, the unsteady flow equations are solved using an implicit time-marching approach. Steady and unsteady computations for two vibration modes were carried out at two rotational speeds: 100 percent (design) and 70 percent (part-speed). The steady and unsteady results obtained from the two analysis methods compare well, thus verifying the recently developed HB aeroelastic analysis. Based on the results, the experimental fan was found to have no aeroelastic instability (flutter) at the conditions examined in this study.
International Nuclear Information System (INIS)
Hawking, S.
1993-01-01
What happened at the beginning of the expansion of the universe. Did space time have an edge at the Big Bang. The answer is that, if the boundary conditions of the universe are that it has no boundary, time ceases to be well-defined in the very early universe as the direction ''north'' ceases to be well defined at the North Pole of the Earth. The quantity that we measure as time has a beginning but that does not mean spacetime has an edge, just as the surface of the Earth does not have an edge at the North Pole. 8 figs
An, Xinliang; Wong, Willie Wai Yeung
2018-01-01
Many classical results in relativity theory concerning spherically symmetric space-times have easy generalizations to warped product space-times, with a two-dimensional Lorentzian base and arbitrary dimensional Riemannian fibers. We first give a systematic presentation of the main geometric constructions, with emphasis on the Kodama vector field and the Hawking energy; the construction is signature independent. This leads to proofs of general Birkhoff-type theorems for warped product manifolds; our theorems in particular apply to situations where the warped product manifold is not necessarily Einstein, and thus can be applied to solutions with matter content in general relativity. Next we specialize to the Lorentzian case and study the propagation of null expansions under the assumption of the dominant energy condition. We prove several non-existence results relating to the Yamabe class of the fibers, in the spirit of the black-hole topology theorem of Hawking–Galloway–Schoen. Finally we discuss the effect of the warped product ansatz on matter models. In particular we construct several cosmological solutions to the Einstein–Euler equations whose spatial geometry is generally not isotropic.
Field, F.; Goodbun, J.; Watson, V.
Architects have a role to play in interplanetary space that has barely yet been explored. The architectural community is largely unaware of this new territory, for which there is still no agreed method of practice. There is moreover a general confusion, in scientific and related fields, over what architects might actually do there today. Current extra-planetary designs generally fail to explore the dynamic and relational nature of space-time, and often reduce human habitation to a purely functional problem. This is compounded by a crisis over the representation (drawing) of space-time. The present work returns to first principles of architecture in order to realign them with current socio-economic and technological trends surrounding the space industry. What emerges is simultaneously the basis for an ecological space architecture, and the representational strategies necessary to draw it. We explore this approach through a work of design-based research that describes the construction of Ocean; a huge body of water formed by the collision of two asteroids at the Translunar Lagrange Point (L2), that would serve as a site for colonisation, and as a resource to fuel future missions. Ocean is an experimental model for extra-planetary space design and its representation, within the autonomous discipline of architecture.
Space, time and conservation laws
International Nuclear Information System (INIS)
Aronov, R.A.; Ugarov, V.A.
1978-01-01
The Neter theorem establishing correspondence between conservation laws and symmetry properties (space and time in particular) is considered. The theorem is based on one of the possible ways of finding equations of motion for a physical system. From a certain expression (action functional) equations of motion for a system can be obtained which do not contain new physical assertions in principal in comparison with the Newtonian laws. Neter suggested a way of deriving conservation laws by transforming space and time coordinates. Neter theorem consequences raise a number of problems: 1). Are conservation laws (energy, momentum) consequences of space and time symmetry properties. 2). Is it possible to obtain conservation laws in theory neglecting equations of motion. 3). What is of the primary importance: equations of motion, conservation laws or properties of space and time symmetry. It is shown that direct Neter theorem does not testify to stipulation of conservation laws by properties of space and time symmetry and symmetry properties of other non-space -time properties of material systems in objective reality. It says nothing of whether there is any subordination between symmetry properties and conservation laws
Matter fields in curved space-time
International Nuclear Information System (INIS)
Viet, Nguyen Ai; Wali, Kameshwar C.
2000-01-01
We study the geometry of a two-sheeted space-time within the framework of non-commutative geometry. As a prelude to the Standard Model in curved space-time, we present a model of a left- and a right- chiral field living on the two sheeted-space time and construct the action functionals that describe their interactions
On the differentiability of space-time
International Nuclear Information System (INIS)
Clarke, C.J.S.
1977-01-01
It is shown that the differentiability of a space-time is implied by that of its Riemann tensor, assuming a priori only boundedness of the first derivations of the metric. Consequently all the results on space-time singularities proved in earlier papers by the author hold true in C 2- space-times. (author)
International Nuclear Information System (INIS)
Raine, D.J.; Heller, M.
1981-01-01
Analyzing the development of the structure of space-time from the theory of Aristotle to the present day, the present work attempts to sketch a science of relativistic mechanics. The concept of relativity is discussed in relation to the way in which space-time splits up into space and time, and in relation to Mach's principle concerning the relativity of inertia. Particular attention is given to the following topics: Aristotelian dynamics Copernican kinematics Newtonian dynamics the space-time of classical dynamics classical space-time in the presence of gravity the space-time of special relativity the space-time of general relativity solutions and problems in general relativity Mach's principle and the dynamics of space-time theories of inertial mass the integral formation of general relativity and the frontiers of relativity
Directory of Open Access Journals (Sweden)
Petré Frederik
2004-01-01
Full Text Available In the downlink of DS-CDMA, frequency-selectivity destroys the orthogonality of the user signals and introduces multiuser interference (MUI. Space-time chip equalization is an efficient tool to restore the orthogonality of the user signals and suppress the MUI. Furthermore, multiple-input multiple-output (MIMO communication techniques can result in a significant increase in capacity. This paper focuses on space-time block coding (STBC techniques, and aims at combining STBC techniques with the original single-antenna DS-CDMA downlink scheme. This results into the so-called space-time block coded DS-CDMA downlink schemes, many of which have been presented in the past. We focus on a new scheme that enables both the maximum multiantenna diversity and the maximum multipath diversity. Although this maximum diversity can only be collected by maximum likelihood (ML detection, we pursue suboptimal detection by means of space-time chip equalization, which lowers the computational complexity significantly. To design the space-time chip equalizers, we also propose efficient pilot-based methods. Simulation results show improved performance over the space-time RAKE receiver for the space-time block coded DS-CDMA downlink schemes that have been proposed for the UMTS and IS-2000 W-CDMA standards.
Computation of robustly stabilizing PID controllers for interval systems.
Matušů, Radek; Prokop, Roman
2016-01-01
The paper is focused on the computation of all possible robustly stabilizing Proportional-Integral-Derivative (PID) controllers for plants with interval uncertainty. The main idea of the proposed method is based on Tan's (et al.) technique for calculation of (nominally) stabilizing PI and PID controllers or robustly stabilizing PI controllers by means of plotting the stability boundary locus in either P-I plane or P-I-D space. Refinement of the existing method by consideration of 16 segment plants instead of 16 Kharitonov plants provides an elegant and efficient tool for finding all robustly stabilizing PID controllers for an interval system. The validity and relatively effortless application of presented theoretical concepts are demonstrated through a computation and simulation example in which the uncertain mathematical model of an experimental oblique wing aircraft is robustly stabilized.
computation of the stability constants for the inclusion complexes of
African Journals Online (AJOL)
PrF MU
stability constants of ADA with β-CD with the use of MO as an auxiliary agent were evaluated. ..... The latter statement can also be strengthened by the computed species distribution diagram for .... and 5-position of the adamantyl body.
Path integration on space times with symmetry
International Nuclear Information System (INIS)
Low, S.G.
1985-01-01
Path integration on space times with symmetry is investigated using a definition of path integration of Gaussian integrators. Gaussian integrators, systematically developed using the theory of projective distributions, may be defined in terms of a Jacobi operator Green function. This definition of the path integral yields a semiclassical expansion of the propagator which is valid on caustics. The semiclassical approximation to the free particle propagator on symmetric and reductive homogeneous spaces is computed in terms of the complete solution of the Jacobi equation. The results are used to test the validity of using the Schwinger-DeWitt transform to compute an approximation to the coincidence limit of a field theory Green function from a WKB propagator. The method is found not to be valid except for certain special cases. These cases include manifolds constructed from the direct product of flat space and group manifolds, on which the free particle WKB approximation is exact and two sphere. The multiple geodesic contribution to 2 > on Schwarzschild in the neighborhood of rho = 3M is computed using the transform
Possibility of extending space-time coordinates
International Nuclear Information System (INIS)
Wang Yongcheng.
1993-11-01
It has been shown that one coordinate system can describe a whole space-time region except some supersurfaces on which there are coordinate singularities. The conditions of extending a coordinate from real field to complex field are studied. It has been shown that many-valued coordinate transformations may help us to extend space-time regions and many-valued metric functions may make one coordinate region to describe more than one space-time regions. (author). 11 refs
Fermion systems in discrete space-time
International Nuclear Information System (INIS)
Finster, Felix
2007-01-01
Fermion systems in discrete space-time are introduced as a model for physics on the Planck scale. We set up a variational principle which describes a non-local interaction of all fermions. This variational principle is symmetric under permutations of the discrete space-time points. We explain how for minimizers of the variational principle, the fermions spontaneously break this permutation symmetry and induce on space-time a discrete causal structure
Fermion systems in discrete space-time
Energy Technology Data Exchange (ETDEWEB)
Finster, Felix [NWF I - Mathematik, Universitaet Regensburg, 93040 Regensburg (Germany)
2007-05-15
Fermion systems in discrete space-time are introduced as a model for physics on the Planck scale. We set up a variational principle which describes a non-local interaction of all fermions. This variational principle is symmetric under permutations of the discrete space-time points. We explain how for minimizers of the variational principle, the fermions spontaneously break this permutation symmetry and induce on space-time a discrete causal structure.
Fermion Systems in Discrete Space-Time
Finster, Felix
2006-01-01
Fermion systems in discrete space-time are introduced as a model for physics on the Planck scale. We set up a variational principle which describes a non-local interaction of all fermions. This variational principle is symmetric under permutations of the discrete space-time points. We explain how for minimizers of the variational principle, the fermions spontaneously break this permutation symmetry and induce on space-time a discrete causal structure.
Fermion systems in discrete space-time
Finster, Felix
2007-05-01
Fermion systems in discrete space-time are introduced as a model for physics on the Planck scale. We set up a variational principle which describes a non-local interaction of all fermions. This variational principle is symmetric under permutations of the discrete space-time points. We explain how for minimizers of the variational principle, the fermions spontaneously break this permutation symmetry and induce on space-time a discrete causal structure.
Wu, Ning
2012-01-01
When we discuss problems on gravity, we can not avoid some fundamental physical problems, such as space-time, inertia, and inertial reference frame. The goal of this paper is to discuss the logic system of gravity theory and the problems of space-time, inertia, and inertial reference frame. The goal of this paper is to set up the theory on space-time in gauge theory of gravity. Based on this theory, it is possible for human kind to manipulate physical space-time on earth, and produce a machin...
Soffel, Michael
2013-01-01
The high accuracy of modern astronomical spatial-temporal reference systems has made them considerably complex. This book offers a comprehensive overview of such systems. It begins with a discussion of ‘The Problem of Time’, including recent developments in the art of clock making (e.g., optical clocks) and various time scales. The authors address the definitions and realization of spatial coordinates by reference to remote celestial objects such as quasars. After an extensive treatment of classical equinox-based coordinates, new paradigms for setting up a celestial reference system are introduced that no longer refer to the translational and rotational motion of the Earth. The role of relativity in the definition and realization of such systems is clarified. The topics presented in this book are complemented by exercises (with solutions). The authors offer a series of files, written in Maple, a standard computer algebra system, to help readers get a feel for the various models and orders of magnitude. ...
Space-time and matter in 'prephysics'
International Nuclear Information System (INIS)
Terazawa, Hidezumi.
1985-05-01
Many fundamental questions concerning the space-time and matter are asked and answered in ''prephysics'', a new line of physics (or philosophy but not metaphysics). They include the following: 1) ''Why is our space-time of 4 dimensions.'', 2) ''What is the ultimate form of matter.'' and 3) ''How was our universe created.''. (author)
Spontaneous symmetry breaking in curved space-time
International Nuclear Information System (INIS)
Toms, D.J.
1982-01-01
An approach dealing with some of the complications which arise when studying spontaneous symmetry breaking beyond the tree-graph level in situations where the effective potential may not be used is discussed. These situations include quantum field theory on general curved backgrounds or in flat space-times with non-trivial topologies. Examples discussed are a twisted scalar field in S 1 xR 3 and instabilities in an expanding universe. From these it is seen that the topology and curvature of a space-time may affect the stability of the vacuum state. There can be critical length scales or times beyond which symmetries may be broken or restored in certain cases. These features are not present in Minkowski space-time and so would not show up in the usual types of early universe calculations. (U.K.)
Some consequences of a non-commutative space-time structure
International Nuclear Information System (INIS)
Vilela Mendes, R.
2005-01-01
The existence of a fundamental length (or fundamental time) has been conjectured in many contexts. Here we discuss some consequences of a fundamental constant of this type, which emerges as a consequence of deformation-stability considerations leading to a non-commutative space-time structure. This mathematically well defined structure is sufficiently constrained to allow for unambiguous experimental predictions. In particular we discuss the phase-space volume modifications and their relevance for the calculation of the Greisen-Zatsepin-Kuz'min sphere. The (small) corrections to the spectrum of the Coulomb problem are also computed. (orig.)
Preconditioned iterative methods for space-time fractional advection-diffusion equations
Zhao, Zhi; Jin, Xiao-Qing; Lin, Matthew M.
2016-08-01
In this paper, we propose practical numerical methods for solving a class of initial-boundary value problems of space-time fractional advection-diffusion equations. First, we propose an implicit method based on two-sided Grünwald formulae and discuss its stability and consistency. Then, we develop the preconditioned generalized minimal residual (preconditioned GMRES) method and preconditioned conjugate gradient normal residual (preconditioned CGNR) method with easily constructed preconditioners. Importantly, because resulting systems are Toeplitz-like, fast Fourier transform can be applied to significantly reduce the computational cost. We perform numerical experiments to demonstrate the efficiency of our preconditioners, even in cases with variable coefficients.
Computation of stabilizing PI and PID controllers using the stability boundary locus
International Nuclear Information System (INIS)
Tan, Nusret; Kaya, Ibrahim; Yeroglu, Celaleddin; Atherton, Derek P.
2006-01-01
In this paper, a new method for the calculation of all stabilizing PI controllers is given. The proposed method is based on plotting the stability boundary locus in the (k p , k i )-plane and then computing the stabilizing values of the parameters of a PI controller. The technique presented does not require sweeping over the parameters and also does not need linear programming to solve a set of inequalities. Thus it offers several important advantages over existing results obtained in this direction. Beyond stabilization, the method is used to shift all poles to a shifted half plane that guarantees a specified settling time of response. Computation of stabilizing PI controllers which achieve user specified gain and phase margins is studied. It is shown via an example that the stabilizing region in the (k p , k i )-plane is not always a convex set. The proposed method is also used to design PID controllers. The limiting values of a PID controller which stabilize a given system are obtained in the (k p , k i )-plane (k p , k d )-plane and (k i , k d )-plane. Furthermore, the proposed method is used to compute all the parameters of a PI controller which stabilize a control system with an interval plant family. Examples are given to show the benefits of the method presented
Hyperbolic statics in space-time
Pavlov, Dmitry; Kokarev, Sergey
2014-01-01
Based on the concept of material event as an elementary material source that is concentrated on metric sphere of zero radius --- light-cone of Minkowski space-time, we deduce the analog of Coulomb's law for hyperbolic space-time field universally acting between the events of space-time. Collective field that enables interaction of world lines of a pair of particles at rest contains a standard 3-dimensional Coulomb's part and logarithmic addendum. We've found that the Coulomb's part depends on...
Semiclassical expanding discrete space-times
International Nuclear Information System (INIS)
Cobb, W.K.; Smalley, L.L.
1981-01-01
Given the close ties between general relativity and geometry one might reasonably expect that quantum effects associated with gravitation might also be tied to the geometry of space-time, namely, to some sort of discreteness in space-time itself. In particular it is supposed that space-time consists of a discrete lattice of points rather than the usual continuum. Since astronomical evidence seems to suggest that the universe is expanding, the lattice must also expand. Some of the implications of such a model are that the proton should presently be stable, and the universe should be closed although the mechanism for closure is quantum mechanical. (author)
Performance measurements in 3D ideal magnetohydrodynamic stability computations
International Nuclear Information System (INIS)
Anderson, D.V.; Cooper, W.A.; Gruber, R.; Schwenn, U.
1989-10-01
The 3D ideal magnetohydrodynamic stability code TERPSICHORE has been designed to take advantage of vector and microtasking capabilities of the latest CRAY computers. To keep the number of operations small most efficient algorithms have been applied in each computational step. The program investigates the stability properties of fusion reactor relevant plasma configurations confined by magnetic fields. For a typical 3D HELIAS configuration that has been considered we obtain an overall performance in excess of 1 Gflops on an eight processor CRAY-YMP machine. (author) 3 figs., 1 tab., 11 refs
Twistor Cosmology and Quantum Space-Time
International Nuclear Information System (INIS)
Brody, D.C.; Hughston, L.P.
2005-01-01
The purpose of this paper is to present a model of a 'quantum space-time' in which the global symmetries of space-time are unified in a coherent manner with the internal symmetries associated with the state space of quantum-mechanics. If we take into account the fact that these distinct families of symmetries should in some sense merge and become essentially indistinguishable in the unified regime, our framework may provide an approximate description of or elementary model for the structure of the universe at early times. The quantum elements employed in our characterisation of the geometry of space-time imply that the pseudo-Riemannian structure commonly regarded as an essential feature in relativistic theories must be dispensed with. Nevertheless, the causal structure and the physical kinematics of quantum space-time are shown to persist in a manner that remains highly analogous to the corresponding features of the classical theory. In the case of the simplest conformally flat cosmological models arising in this framework, the twistorial description of quantum space-time is shown to be effective in characterising the various physical and geometrical properties of the theory. As an example, a sixteen-dimensional analogue of the Friedmann-Robertson-Walker cosmologies is constructed, and its chronological development is analysed in some detail. More generally, whenever the dimension of a quantum space-time is an even perfect square, there exists a canonical way of breaking the global quantum space-time symmetry so that a generic point of quantum space-time can be consistently interpreted as a quantum operator taking values in Minkowski space. In this scenario, the breakdown of the fundamental symmetry of the theory is due to a loss of quantum entanglement between space-time and internal quantum degrees of freedom. It is thus possible to show in a certain specific sense that the classical space-time description is an emergent feature arising as a consequence of a
Minkowski space-time is locally extendible
International Nuclear Information System (INIS)
Beem, J.K.
1980-01-01
An example of a real analytic local extension of Minkowski space-time is given in this note. This local extension is not across points of the b-boundary since Minkowski space-time has an empty b-boundary. Furthermore, this local extension is not across points of the causal boundary. The example indicates that the concept of local inextendibility may be less useful than originally envisioned. (orig.)
On discrete models of space-time
International Nuclear Information System (INIS)
Horzela, A.; Kempczynski, J.; Kapuscik, E.; Georgia Univ., Athens, GA; Uzes, Ch.
1992-02-01
Analyzing the Einstein radiolocation method we come to the conclusion that results of any measurement of space-time coordinates should be expressed in terms of rational numbers. We show that this property is Lorentz invariant and may be used in the construction of discrete models of space-time different from the models of the lattice type constructed in the process of discretization of continuous models. (author)
Space-Time Disarray and Visual Awareness
Directory of Open Access Journals (Sweden)
Jan Koenderink
2012-04-01
Full Text Available Local space-time scrambling of optical data leads to violent jerks and dislocations. On masking these, visual awareness of the scene becomes cohesive, with dislocations discounted as amodally occluding foreground. Such cohesive space-time of awareness is technically illusory because ground truth is jumbled whereas awareness is coherent. Apparently the visual field is a construction rather than a (veridical perception.
Quantum fields in curved space-times
International Nuclear Information System (INIS)
Ashtekar, A.; Magnon, A.
1975-01-01
The problem of obtaining a quantum description of the (real) Klein-Gordon system in a given curved space-time is discussed. An algebraic approach is used. The *-algebra of quantum operators is constructed explicitly and the problem of finding its *-representation is reduced to that of selecting a suitable complex structure on the real vector space of the solutions of the (classical) Klein-Gordon equation. Since, in a static space-time, there already exists, a satisfactory quantum field theory, in this case one already knows what the 'correct' complex structure is. A physical characterization of this 'correct' complex structure is obtained. This characterization is used to extend quantum field theory to non-static space-times. Stationary space-times are considered first. In this case, the issue of extension is completely straightforward and the resulting theory is the natural generalization of the one in static space-times. General, non-stationary space-times are then considered. In this case the issue of extension is quite complicated and only a plausible extension is presented. Although the resulting framework is well-defined mathematically, the physical interpretation associated with it is rather unconventional. Merits and weaknesses of this framework are discussed. (author)
Space-time-modulated stochastic processes
Giona, Massimiliano
2017-10-01
Starting from the physical problem associated with the Lorentzian transformation of a Poisson-Kac process in inertial frames, the concept of space-time-modulated stochastic processes is introduced for processes possessing finite propagation velocity. This class of stochastic processes provides a two-way coupling between the stochastic perturbation acting on a physical observable and the evolution of the physical observable itself, which in turn influences the statistical properties of the stochastic perturbation during its evolution. The definition of space-time-modulated processes requires the introduction of two functions: a nonlinear amplitude modulation, controlling the intensity of the stochastic perturbation, and a time-horizon function, which modulates its statistical properties, providing irreducible feedback between the stochastic perturbation and the physical observable influenced by it. The latter property is the peculiar fingerprint of this class of models that makes them suitable for extension to generic curved-space times. Considering Poisson-Kac processes as prototypical examples of stochastic processes possessing finite propagation velocity, the balance equations for the probability density functions associated with their space-time modulations are derived. Several examples highlighting the peculiarities of space-time-modulated processes are thoroughly analyzed.
Topics in Modeling of Cochlear Dynamics: Computation, Response and Stability Analysis
Filo, Maurice G.
This thesis touches upon several topics in cochlear modeling. Throughout the literature, mathematical models of the cochlea vary according to the degree of biological realism to be incorporated. This thesis casts the cochlear model as a continuous space-time dynamical system using operator language. This framework encompasses a wider class of cochlear models and makes the dynamics more transparent and easier to analyze before applying any numerical method to discretize space. In fact, several numerical methods are investigated to study the computational efficiency of the finite dimensional realizations in space. Furthermore, we study the effects of the active gain perturbations on the stability of the linearized dynamics. The stability analysis is used to explain possible mechanisms underlying spontaneous otoacoustic emissions and tinnitus. Dynamic Mode Decomposition (DMD) is introduced as a useful tool to analyze the response of nonlinear cochlear models. Cochlear response features are illustrated using DMD which has the advantage of explicitly revealing the spatial modes of vibrations occurring in the Basilar Membrane (BM). Finally, we address the dynamic estimation problem of BM vibrations using Extended Kalman Filters (EKF). Due to the limitations of noninvasive sensing schemes, such algorithms are inevitable to estimate the dynamic behavior of a living cochlea.
Advances in Computational Stability Analysis of Composite Aerospace Structures
International Nuclear Information System (INIS)
Degenhardt, R.; Araujo, F. C. de
2010-01-01
European aircraft industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents different advances from the area of computational stability analysis of composite aerospace structures which contribute to that field. For stringer stiffened panels main results of the finished EU project COCOMAT are given. It investigated the exploitation of reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. For unstiffened cylindrical composite shells a proposal for a new design method is presented.
DEFF Research Database (Denmark)
Kepp, Kasper Planeta
2015-01-01
Fast and accurate computation of protein stability is increasingly important for e.g. protein engineering and protein misfolding diseases, but no consensus methods exist for important proteins such as globins, and performance may depend on the type of structural input given. This paper reports be...
Axiomatics of uniform space-time models
International Nuclear Information System (INIS)
Levichev, A.V.
1983-01-01
The mathematical statement of space-time axiomatics of the special theory of relativity is given; it postulates that the space-time M is the binding single boundary Hausedorf local-compact four-dimensional topological space with the given order. The theorem is proved: if the invariant order in the four-dimensional group M is given by the semi-group P, which contingency K contains inner points , then M is commutative. The analogous theorem is correct for the group of two and three dimensionalities
Verifiable Measurement-Only Blind Quantum Computing with Stabilizer Testing.
Hayashi, Masahito; Morimae, Tomoyuki
2015-11-27
We introduce a simple protocol for verifiable measurement-only blind quantum computing. Alice, a client, can perform only single-qubit measurements, whereas Bob, a server, can generate and store entangled many-qubit states. Bob generates copies of a graph state, which is a universal resource state for measurement-based quantum computing, and sends Alice each qubit of them one by one. Alice adaptively measures each qubit according to her program. If Bob is honest, he generates the correct graph state, and, therefore, Alice can obtain the correct computation result. Regarding the security, whatever Bob does, Bob cannot get any information about Alice's computation because of the no-signaling principle. Furthermore, malicious Bob does not necessarily send the copies of the correct graph state, but Alice can check the correctness of Bob's state by directly verifying the stabilizers of some copies.
Mass Formulae for Broken Supersymmetry in Curved Space-Time
Ferrara, Sergio
2016-01-01
We derive the mass formulae for ${\\cal N}=1$, $D=4$ matter-coupled Supergravity for broken (and unbroken) Supersymmetry in curved space-time. These formulae are applicable to de Sitter configurations as is the case for inflation. For unbroken Supersymmetry in anti-de Sitter (AdS) one gets the mass relations modified by the AdS curvature. We compute the mass relations both for the potential and its derivative non-vanishing.
Computing Stability Effects of Mutations in Human Superoxide Dismutase 1
DEFF Research Database (Denmark)
Kepp, Kasper Planeta
2014-01-01
Protein stability is affected in several diseases and is of substantial interest in efforts to correlate genotypes to phenotypes. Superoxide dismutase 1 (SOD1) is a suitable test case for such correlations due to its abundance, stability, available crystal structures and thermochemical data......, and physiological importance. In this work, stability changes of SOD1 mutations were computed with five methods, CUPSAT, I-Mutant2.0, I-Mutant3.0, PoPMuSiC, and SDM, with emphasis on structural sensitivity as a potential issue in structure-based protein calculation. The large correlation between experimental...... literature data of SOD1 dimers and monomers (r = 0.82) suggests that mutations in separate protein monomers are mostly additive. PoPMuSiC was most accurate (typical MAE ∼ 1 kcal/mol, r ∼ 0.5). The relative performance of the methods was not very structure-dependent, and the more accurate methods also...
Space-time modeling of timber prices
Mo Zhou; Joseph Buongriorno
2006-01-01
A space-time econometric model was developed for pine sawtimber timber prices of 21 geographically contiguous regions in the southern United States. The correlations between prices in neighboring regions helped predict future prices. The impulse response analysis showed that although southern pine sawtimber markets were not globally integrated, local supply and demand...
Strings in arbitrary space-time dimensions
International Nuclear Information System (INIS)
Fabbrichesi, M.E.; Leviant, V.M.
1988-01-01
A modified approach to the theory of a quantum string is proposed. A discussion of the gauge fixing of conformal symmetry by means of Kac-Moody algebrae is presented. Virasoro-like operators are introduced to cancel the conformal anomaly in any number of space-time dimensions. The possibility of massless states in the spectrum is pointed out. 18 refs
Relativistic positioning in Schwarzschild space-time
International Nuclear Information System (INIS)
Puchades, Neus; Sáez, Diego
2015-01-01
In the Schwarzschild space-time created by an idealized static spherically symmetric Earth, two approaches -based on relativistic positioning- may be used to estimate the user position from the proper times broadcast by four satellites. In the first approach, satellites move in the Schwarzschild space-time and the photons emitted by the satellites follow null geodesics of the Minkowski space-time asymptotic to the Schwarzschild geometry. This assumption leads to positioning errors since the photon world lines are not geodesics of any Minkowski geometry. In the second approach -the most coherent one- satellites and photons move in the Schwarzschild space-time. This approach is a first order one in the dimensionless parameter GM/R (with the speed of light c=1). The two approaches give different inertial coordinates for a given user. The differences are estimated and appropriately represented for users located inside a great region surrounding Earth. The resulting values (errors) are small enough to justify the use of the first approach, which is the simplest and the most manageable one. The satellite evolution mimics that of the GALILEO global navigation satellite system. (paper)
Charge conjugation and internal space time symmetries
International Nuclear Information System (INIS)
Pavsic, M.; Recami, E.
1982-01-01
The relativistic framework in which fundamental particles are regarded as extended objects is adopted. Then it is shown than the geometrical operation which reflects the internal space time particle is equivalent to the operation C which inverts the sign of all its additive charges
Space-time and Local Gauge Symmetries
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 2. Symmetries of Particle Physics: Space-time and Local Gauge Symmetries. Sourendu Gupta. General Article Volume 6 Issue 2 February 2001 pp 29-38. Fulltext. Click here to view fulltext PDF. Permanent link:
Local and nonlocal space-time singularities
International Nuclear Information System (INIS)
Konstantinov, M.Yu.
1985-01-01
The necessity to subdivide the singularities into two classes: local and nonlocal, each of them to be defined independently, is proved. Both classes of the singularities are defined, and the relation between the definitions introduced and the standard definition of singularities, based on space-time, incompleteness, is established. The relation between definitions introduced and theorems on the singularity existence is also established
Quantum space-time and gravitational consequences
International Nuclear Information System (INIS)
Namsrai, K.
1986-01-01
Relativistic particle dynamics and basic physical quantities for the general theory of gravity are reconstructed from a quantum space-time point of view. An additional force caused by quantum space-time appears in the equation of particle motion, giving rise to a reformulation of the equivalence principle up to values of O(L 2 ), where L is the fundamental length. It turns out that quantum space-time leads to quantization of gravity, i.e. the metric tensor g/sub uv/ (/ZETA/) becomes operator-valued and is not commutative at different points x/sup micro/ and y/sup micro/ in usual space-time on a large scale, and its commutator depending on the ''vielbein'' field (gaugelike graviton field) is proportional to L 2 multiplied by a translationinvariant wave function propagated between points x/sup micro/ and y/sup micro/. In the given scheme, there appears to be an antigravitational effect in the motion of a particle in the gravitational force. This effect depends on the value of particle mass; when a particle is heavy its free-fall time is long compared to that for a light-weight particle. The problem of the change of time scale and the anisotropy of inertia are discussed. From experimental data from testing of the latter effect it follows that L ≤ 10 -22 cm
Special relativity and space-time geometry.
Molski, M.
An attempt has been made to formulate the special theory of relativity in a space-time that is explicitly absolute and strictly determines the kinematical characteristics of a particle in uniform translational motion. The approach developed is consistent with Einstein's relativity and permits explanation of the inertia phenomenon.
Space-Time Transformation in Flux-form Semi-Lagrangian Schemes
Directory of Open Access Journals (Sweden)
Peter C. Chu Chenwu Fan
2010-01-01
Full Text Available With a finite volume approach, a flux-form semi-Lagrangian (TFSL scheme with space-time transformation was developed to provide stable and accurate algorithm in solving the advection-diffusion equation. Different from the existing flux-form semi-Lagrangian schemes, the temporal integration of the flux from the present to the next time step is transformed into a spatial integration of the flux at the side of a grid cell (space for the present time step using the characteristic-line concept. The TFSL scheme not only keeps the good features of the semi-Lagrangian schemes (no Courant number limitation, but also has higher accuracy (of a second order in both time and space. The capability of the TFSL scheme is demonstrated by the simulation of the equatorial Rossby-soliton propagation. Computational stability and high accuracy makes this scheme useful in ocean modeling, computational fluid dynamics, and numerical weather prediction.
Mach's principle and space-time structure
International Nuclear Information System (INIS)
Raine, D.J.
1981-01-01
Mach's principle, that inertial forces should be generated by the motion of a body relative to the bulk of matter in the universe, is shown to be related to the structure imposed on space-time by dynamical theories. General relativity theory and Mach's principle are both shown to be well supported by observations. Since Mach's principle is not contained in general relativity this leads to a discussion of attempts to derive Machian theories. The most promising of these appears to be a selection rule for solutions of the general relativistic field equations, in which the space-time metric structure is generated by the matter content of the universe only in a well-defined way. (author)
Topology of classical vacuum space-time
International Nuclear Information System (INIS)
Cho, Y.M.
2007-04-01
We present a topological classification of classical vacuum space-time. Assuming the 3-dimensional space allows a global chart, we show that the static vacuum space-time of Einstein's theory can be classified by the knot topology π 3 (S 3 ) = π 3 (S 2 ). Viewing Einstein's theory as a gauge theory of Lorentz group and identifying the gravitational connection as the gauge potential of Lorentz group, we construct all possible vacuum gravitational connections which give a vanishing curvature tensor. With this we show that the vacuum connection has the knot topology, the same topology which describes the multiple vacua of SU(2) gauge theory. We discuss the physical implications of our result in quantum gravity. (author)
A comparison between space-time video descriptors
Costantini, Luca; Capodiferro, Licia; Neri, Alessandro
2013-02-01
The description of space-time patches is a fundamental task in many applications such as video retrieval or classification. Each space-time patch can be described by using a set of orthogonal functions that represent a subspace, for example a sphere or a cylinder, within the patch. In this work, our aim is to investigate the differences between the spherical descriptors and the cylindrical descriptors. In order to compute the descriptors, the 3D spherical and cylindrical Zernike polynomials are employed. This is important because both the functions are based on the same family of polynomials, and only the symmetry is different. Our experimental results show that the cylindrical descriptor outperforms the spherical descriptor. However, the performances of the two descriptors are similar.
Vector mass in curved space-times
International Nuclear Information System (INIS)
Maia, M.D.
The use of the Poincare-symmetry appears to be incompatible with the presence of the gravitational field. The consequent problem of the definition of the mass operator is analysed and an alternative definition based on constant curvature tangent spaces is proposed. In the case where the space-time has no killing vector fields, four independent mass operators can be defined at each point. (Author) [pt
The manifold model for space-time
International Nuclear Information System (INIS)
Heller, M.
1981-01-01
Physical processes happen on a space-time arena. It turns out that all contemporary macroscopic physical theories presuppose a common mathematical model for this arena, the so-called manifold model of space-time. The first part of study is an heuristic introduction to the concept of a smooth manifold, starting with the intuitively more clear concepts of a curve and a surface in the Euclidean space. In the second part the definitions of the Csub(infinity) manifold and of certain structures, which arise in a natural way from the manifold concept, are given. The role of the enveloping Euclidean space (i.e. of the Euclidean space appearing in the manifold definition) in these definitions is stressed. The Euclidean character of the enveloping space induces to the manifold local Euclidean (topological and differential) properties. A suggestion is made that replacing the enveloping Euclidean space by a discrete non-Euclidean space would be a correct way towards the quantization of space-time. (author)
International Nuclear Information System (INIS)
Namsrai, K.
1988-01-01
The review presents systematically the results of studies which develop an idea of quantum properties of space-time in the microworld or near exotic objects (black holes, magnetic monopoles and others). On the basis of this idea motion equations of nonrelativistic and relativistic particles are studied. It is shown that introducing concept of quantum space-time at small distances (or near superdense matter) leads to an additional force giving rise to appearance of spiral-like behaviour of a particle along its classical trajectory. Given method is generalized to nonrelativistic quantum mechanics and to motion of a particle in gravitational force. In the latter case, there appears to be an antigravitational effect in the motion of a particle leading to different value of free-fall time (at least for gravitational force of exotic objects) for particles with different masses. Gravitational consequences of quantum space-time and tensor structures of physical quantities are investigated in detail. From experimental data on testing relativity and anisotropy of inertia estimation L ≤ 10 -22 cm on the value of the fundamental length is obtained. (author)
Vacuum polarization on black hole space times
International Nuclear Information System (INIS)
Jensen, B.P.
1985-01-01
The effects of vacuum polarization in black hole space times are examined. Particular attention is given to the vacuum physics inside the event horizon. The analytic properties of the solutions to the radial wave equation in Schwarzs child space time as functions of argument, frequency, and angular momentum are given. These functions are employed to define the Feynmann Green function (G/sub F/(x,x') for a scalar field subject to the Hartle-Hawking boundary conditions. An examination of the Schwarzschild mode functions near r = 0 is provided. This work is necessary background for a future calculation of 2 > and the quantum stress-energy tensor for small r. Some opinions are given on how this calculation might be performed. A solution of the one-loop Einstein equations for Schwarzs child Anti-deSitter (SAdS) space time is presented, using Page's approximation to the quantum stress tensor. The resulting perturbed metric is shown to be unphysical, as it leads to a system of fields with infinite total energy. This problem is believed to be due to a failure of Page's method in SAdS. Suggestions are given on how one might correct the method
Space-time modeling of soil moisture
Chen, Zijuan; Mohanty, Binayak P.; Rodriguez-Iturbe, Ignacio
2017-11-01
A physically derived space-time mathematical representation of the soil moisture field is carried out via the soil moisture balance equation driven by stochastic rainfall forcing. The model incorporates spatial diffusion and in its original version, it is shown to be unable to reproduce the relative fast decay in the spatial correlation functions observed in empirical data. This decay resulting from variations in local topography as well as in local soil and vegetation conditions is well reproduced via a jitter process acting multiplicatively over the space-time soil moisture field. The jitter is a multiplicative noise acting on the soil moisture dynamics with the objective to deflate its correlation structure at small spatial scales which are not embedded in the probabilistic structure of the rainfall process that drives the dynamics. These scales of order of several meters to several hundred meters are of great importance in ecohydrologic dynamics. Properties of space-time correlation functions and spectral densities of the model with jitter are explored analytically, and the influence of the jitter parameters, reflecting variabilities of soil moisture at different spatial and temporal scales, is investigated. A case study fitting the derived model to a soil moisture dataset is presented in detail.
The space-time model according to dimensional continuous space-time theory
International Nuclear Information System (INIS)
Martini, Luiz Cesar
2014-01-01
This article results from the Dimensional Continuous Space-Time Theory for which the introductory theoretician was presented in [1]. A theoretical model of the Continuous Space-Time is presented. The wave equation of time into absolutely stationary empty space referential will be described in detail. The complex time, that is the time fixed on the infinite phase time speed referential, is deduced from the New View of Relativity Theory that is being submitted simultaneously with this article in this congress. Finally considering the inseparable Space-Time is presented the duality equation wave-particle.
Aspects of space-time dualities
Giveon, Amit
1996-01-01
Duality groups of Abelian gauge theories on four manifolds and their reduction to two dimensions are considered. The duality groups include elements that relate different space-times in addition to relating different gauge-coupling matrices. We interpret (some of) such dualities as the geometrical symmetries of compactified theories in higher dimensions. In particular, we consider compactifications of a (self-dual) 2-form in 6-D, and compactifications of a self-dual 4-form in 10-D. Relations with a self-dual superstring in 6-D and with the type IIB superstring are discussed.
Quantum mechanics, stochasticity and space-time
International Nuclear Information System (INIS)
Ramanathan, R.
1986-04-01
An extended and more rigorous version of a recent proposal for an objective stochastic formulation of quantum mechanics along with its extension to the relativistic case without spin is presented. The relativistic Klein-Gordon equation is shown to be a particular form of the relativistic Kolmogorov-Fokker-Planck equation which is derived from a covariant formulation of the Chapman-Kolmogorov condition. Complexification of probability amplitudes is again achieved only through a conformal rotation of Minkowski space-time M 4 . (author)
The theory of space, time and gravitation
Fock, V
2015-01-01
The Theory of Space, Time, and Gravitation, 2nd Revised Edition focuses on Relativity Theory and Einstein's Theory of Gravitation and correction of the misinterpretation of the Einsteinian Gravitation Theory. The book first offers information on the theory of relativity and the theory of relativity in tensor form. Discussions focus on comparison of distances and lengths in moving reference frames; comparison of time differences in moving reference frames; position of a body in space at a given instant in a fixed reference frame; and proof of the linearity of the transformation linking two iner
International Nuclear Information System (INIS)
Bombelli, L.; Lee, J.; Meyer, D.; Sorkin, R.D.
1987-01-01
We propose that space-time at the smallest scales is in reality a causal set: a locally finite set of elements endowed with a partial order corresponding to the macroscopic relation that defines past and future. We explore how a Lorentzian manifold can approximate a causal set, noting in particular that the thereby defined effective dimensionality of a given causal set can vary with length scale. Finally, we speculate briefly on the quantum dynamics of causal sets, indicating why an appropriate choice of action can reproduce general relativity in the classical limit
Space-Time Discrete KPZ Equation
Cannizzaro, G.; Matetski, K.
2018-03-01
We study a general family of space-time discretizations of the KPZ equation and show that they converge to its solution. The approach we follow makes use of basic elements of the theory of regularity structures (Hairer in Invent Math 198(2):269-504, 2014) as well as its discrete counterpart (Hairer and Matetski in Discretizations of rough stochastic PDEs, 2015. arXiv:1511.06937). Since the discretization is in both space and time and we allow non-standard discretization for the product, the methods mentioned above have to be suitably modified in order to accommodate the structure of the models under study.
International Nuclear Information System (INIS)
Villasenor, R.F.; Bonilla, J.L.L.; Zuniga, G.O.; Matos, T.
1989-01-01
The authors study space-times embedded in E 5 (that means, pseudo-euclidean five-dimensional spaces) in the intrinsic rigidity case, i.e., when the second fundamental form b if can be determined by the internal geometry of the four-dimensional Riemannian space R 4 . They write down the Gauss and Codazzi equations determining the local isometric embedding of R 4 in E 5 and give some consequences of it. They prove that when there exists intrinsic rigidity, then b if is a linear combination of the metric and Ricci tensor; it is given some applications for the de Sitter and Einstein models
Computational Study of Hypersonic Boundary Layer Stability on Cones
Gronvall, Joel Edwin
Due to the complex nature of boundary layer laminar-turbulent transition in hypersonic flows and the resultant effect on the design of re-entry vehicles, there remains considerable interest in developing a deeper understanding of the underlying physics. To that end, the use of experimental observations and computational analysis in a complementary manner will provide the greatest insights. It is the intent of this work to provide such an analysis for two ongoing experimental investigations. The first focuses on the hypersonic boundary layer transition experiments for a slender cone that are being conducted at JAXA's free-piston shock tunnel HIEST facility. Of particular interest are the measurements of disturbance frequencies associated with transition at high enthalpies. The computational analysis provided for these cases included two-dimensional CFD mean flow solutions for use in boundary layer stability analyses. The disturbances in the boundary layer were calculated using the linear parabolized stability equations. Estimates for transition locations, comparisons of measured disturbance frequencies and computed frequencies, and a determination of the type of disturbances present were made. It was found that for the cases where the disturbances were measured at locations where the flow was still laminar but nearly transitional, that the highly amplified disturbances showed reasonable agreement with the computations. Additionally, an investigation of the effects of finite-rate chemistry and vibrational excitation on flows over cones was conducted for a set of theoretical operational conditions at the HIEST facility. The second study focuses on transition in three-dimensional hypersonic boundary layers, and for this the cone at angle of attack experiments being conducted at the Boeing/AFOSR Mach-6 quiet tunnel at Purdue University were examined. Specifically, the effect of surface roughness on the development of the stationary crossflow instability are investigated
Technology for computer-stabilized peak of NaI(Tl) gamma spectrum
International Nuclear Information System (INIS)
Chen Jianzhen; Guo Lanying; Ling Qiu; Qu Guopu; Zhao Lihong; Hu Chuangye
2005-01-01
An improved technology for spectrum stabilization of NaI(Tl) gamma spectrum was introduced. This technology is based on the system using a reference peak, which is equivalent gamma peak of 241 Am source. The computer seeks peak's position deviation and computes adjust value of programmable amplifier and controls programmable amplifier to stabilize spectrum by digital PID. This is a technology of spectrum stabilizing with 'hardware + reference-peak + software' and has high stability and fast speed of spectrum stabilizing. (author)
Evolution in Many-Sheeted Space-time
Pitkänen, Matti
2010-01-01
The topics of the article has been restricted to those, which seem to represent the most well-established ideas about evolution in many-sheeted space-time. a) Basic facts about and TGD based model for pre-biotic evolution are discussed. b) A model for the ATP-ADP process based on DNA as topological quantum computer vision, the identification of universal metabolic energy quanta in terms of zero point kinetic energies, and the notion of remote metabolism is discussed. c) A model f...
Mass formulae for broken supersymmetry in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Ferrara, Sergio [Theoretical Physics Department, CERN, Geneva (Switzerland); INFN - Laboratori Nazionali di Frascati, Frascati (Italy); Department of Physics and Astronomy, U.C.L.A, Los Angeles, CA (United States); Proeyen, Antoine van [KU Leuven, Institute for Theoretical Physics, Leuven (Belgium)
2016-11-15
We derive the mass formulae for N = 1, D = 4 matter-coupled Supergravity for broken (and unbroken) Supersymmetry in curved space-time. These formulae are applicable to De Sitter configurations as is the case for inflation. For unbroken Supersymmetry in anti-de Sitter (AdS) one gets the mass relations modified by the AdS curvature. We compute the mass relations both for the potential and its derivative non-vanishing. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
A Reparametrization Approach for Dynamic Space-Time Models
Lee, Hyeyoung; Ghosh, Sujit K.
2008-01-01
Researchers in diverse areas such as environmental and health sciences are increasingly working with data collected across space and time. The space-time processes that are generally used in practice are often complicated in the sense that the auto-dependence structure across space and time is non-trivial, often non-separable and non-stationary in space and time. Moreover, the dimension of such data sets across both space and time can be very large leading to computational difficulties due to...
Canonical quantization of general relativity in discrete space-times.
Gambini, Rodolfo; Pullin, Jorge
2003-01-17
It has long been recognized that lattice gauge theory formulations, when applied to general relativity, conflict with the invariance of the theory under diffeomorphisms. We analyze discrete lattice general relativity and develop a canonical formalism that allows one to treat constrained theories in Lorentzian signature space-times. The presence of the lattice introduces a "dynamical gauge" fixing that makes the quantization of the theories conceptually clear, albeit computationally involved. The problem of a consistent algebra of constraints is automatically solved in our approach. The approach works successfully in other field theories as well, including topological theories. A simple cosmological application exhibits quantum elimination of the singularity at the big bang.
Intraoperative computed tomography with integrated navigation system in spinal stabilizations.
Zausinger, Stefan; Scheder, Ben; Uhl, Eberhard; Heigl, Thomas; Morhard, Dominik; Tonn, Joerg-Christian
2009-12-15
STUDY DESIGN.: A prospective interventional case-series study plus a retrospective analysis of historical patients for comparison of data. OBJECTIVE.: To evaluate workflow, feasibility, and clinical outcome of navigated stabilization procedures with data acquisition by intraoperative computed tomography. SUMMARY OF BACKGROUND DATA.: Routine fluoroscopy to assess pedicle screw placement is not consistently reliable. Our hypothesis was that image-guided spinal navigation using an intraoperative CT-scanner can improve the safety and precision of spinal stabilization surgery. METHODS.: CT data of 94 patients (thoracolumbar [n = 66], C1/2 [n = 12], cervicothoracic instability [n = 16]) were acquired after positioning the patient in the final surgical position. A sliding gantry 40-slice CT was used for image acquisition. Data were imported to a frameless infrared-based neuronavigation workstation. Intraoperative CT was obtained to assess the accuracy of instrumentation and, if necessary, the extent of decompression. All patients were clinically evaluated by Odom-criteria after surgery and after 3 months. RESULTS.: Computed accuracy of the navigation system reached /=2 mm without persistent neurologic or vascular damage in 20/414 screws (4.8%) leading to immediate correction of 10 screws (2.4%). Control-iCT changed the course of surgery in 8 cases (8.5% of all patients). The overall revision rate was 8.5% (4 wound revisions, 2 CSF fistulas, and 2 epidural hematomas). There was no reoperation due to implant malposition. According to Odom-criteria all patients experienced a clinical improvement. A retrospective analysis of 182 patients with navigated thoracolumbar transpedicular stabilizations in the preiCT era revealed an overall revision rate of 10.4% with 4.4% of patients requiring screw revision. CONCLUSION.: Intraoperative CT in combination with neuronavigation provides high accuracy of screw placement and thus safety for patients undergoing spinal stabilization
The method of covariant symbols in curved space-time
International Nuclear Information System (INIS)
Salcedo, L.L.
2007-01-01
Diagonal matrix elements of pseudodifferential operators are needed in order to compute effective Lagrangians and currents. For this purpose the method of symbols is often used, which however lacks manifest covariance. In this work the method of covariant symbols, introduced by Pletnev and Banin, is extended to curved space-time with arbitrary gauge and coordinate connections. For the Riemannian connection we compute the covariant symbols corresponding to external fields, the covariant derivative and the Laplacian, to fourth order in a covariant derivative expansion. This allows one to obtain the covariant symbol of general operators to the same order. The procedure is illustrated by computing the diagonal matrix element of a nontrivial operator to second order. Applications of the method are discussed. (orig.)
Finiteness principle and the concept of space-time
International Nuclear Information System (INIS)
Tati, T.
1984-01-01
It is shown that the non-space-time description can be given by a system of axioms under the postulate of a certain number of pre-supposed physical concepts in which space-time is not included. It is found that space-time is a compound concept of presupposed concepts of non-space-time description connected by an additional condition called 'space-time condition'. (L.C.) [pt
International Nuclear Information System (INIS)
Koronovskij, A.A.; Rempen, I.S.; Khramov, A.E.
2003-01-01
The set of the unstable periodic space-time states, characterizing the chaotic space-time dynamics of the electron beam with the supercritical current in the Pierce diode is discussed. The Lyapunov indicators of the revealed instable space-time states of the chaotic dynamics of the distributed self-excited system are calculated. It is shown that change in the set of the unstable periodic states in dependence on the Pierce parameter is determined by change in the various orbits stability, which is demonstrated by the values of senior Lyapunov unstable state index [ru
On static and radiative space-times
International Nuclear Information System (INIS)
Friedrich, H.
1988-01-01
The conformal constraint equations on space-like hypersurfaces are discussed near points which represent either time-like or spatial infinity for an asymptotically flat solution of Einstein's vacuum field equations. In the case of time-like infinity a certain 'radiativity condition' is derived which must be satisfied by the data at that point. The case of space-like infinity is analysed in detail for static space-times with non-vanishing mass. It is shown that the conformal structure implied here on a slice of constant Killing time, which extends analytically through infinity, satisfies at spatial infinity the radiativity condition. Thus to any static solution exists a certain 'radiative solution' which has a smooth structure at past null infinity and is regular at past time-like infinity. A characterization of these solutions by their 'free data' is given and non-symmetry properties are discussed. (orig.)
Dirac equation in Kerr space-time
Energy Technology Data Exchange (ETDEWEB)
Iyer, B R; Kumar, Arvind [Bombay Univ. (India). Dept. of Physics
1976-06-01
The weak-field low-velocity approximation of Dirac equation in Kerr space-time is investigated. The interaction terms admit of an interpretation in terms of a 'dipole-dipole' interaction in addition to coupling of spin with the angular momentum of the rotating source. The gravitational gyro-factor for spin is identified. The charged case (Kerr-Newman) is studied using minimal prescription for electromagnetic coupling in the locally intertial frame and to the leading order the standard electromagnetic gyro-factor is retrieved. A first order perturbation calculation of the shift of the Schwarzchild energy level yields the main interesting result of this work: the anomalous Zeeman splitting of the energy level of a Dirac particle in Kerr metric.
Stochastic space-time and quantum theory
International Nuclear Information System (INIS)
Frederick, C.
1976-01-01
Much of quantum mechanics may be derived if one adopts a very strong form of Mach's principle such that in the absence of mass, space-time becomes not flat, but stochastic. This is manifested in the metric tensor which is considered to be a collection of stochastic variables. The stochastic-metric assumption is sufficient to generate the spread of the wave packet in empty space. If one further notes that all observations of dynamical variables in the laboratory frame are contravariant components of tensors, and if one assumes that a Lagrangian can be constructed, then one can obtain an explanation of conjugate variables and also a derivation of the uncertainty principle. Finally the superposition of stochastic metrics and the identification of root -g in the four-dimensional invariant volume element root -g dV as the indicator of relative probability yields the phenomenon of interference as will be described for the two-slit experiment
Quantum electrodynamics in curved space-time
International Nuclear Information System (INIS)
Buchbinder, I.L.; Gitman, D.M.; Fradkin, E.S.
1981-01-01
The lagrangian of quantum electrodynamics in curved space-time is constructed and the interaction picture taking into account the external gravitational field exactly is introduced. The transform from the Heisenberg picture to the interaction picture is carried out in a manifestly covariant way. The properties of free spinor and electromagnetic quantum fields are discussed and conditions under which initial and final creation and annihilation operators are connected by unitarity transformation are indicated. The derivation of Feynman's rules for quantum processes are calculated on the base of generalized normal product of operators. The way of reduction formula derivations is indicated and the suitable Green's functions are introduced. A generating functional for this Green's function is defined and the system of functional equations for them is obtained. The representation of different generating funcationals by means of functional integrals is introduced. Some consequences of S-matrix unitary condition are considered which leads to the generalization of the optic theorem
Computational Approach for Epitaxial Polymorph Stabilization through Substrate Selection
Energy Technology Data Exchange (ETDEWEB)
Ding, Hong; Dwaraknath, Shyam S.; Garten, Lauren; Ndione, Paul; Ginley, David; Persson, Kristin A.
2016-05-25
With the ultimate goal of finding new polymorphs through targeted synthesis conditions and techniques, we outline a computational framework to select optimal substrates for epitaxial growth using first principle calculations of formation energies, elastic strain energy, and topological information. To demonstrate the approach, we study the stabilization of metastable VO2 compounds which provides a rich chemical and structural polymorph space. We find that common polymorph statistics, lattice matching, and energy above hull considerations recommends homostructural growth on TiO2 substrates, where the VO2 brookite phase would be preferentially grown on the a-c TiO2 brookite plane while the columbite and anatase structures favor the a-b plane on the respective TiO2 phases. Overall, we find that a model which incorporates a geometric unit cell area matching between the substrate and the target film as well as the resulting strain energy density of the film provide qualitative agreement with experimental observations for the heterostructural growth of known VO2 polymorphs: rutile, A and B phases. The minimal interfacial geometry matching and estimated strain energy criteria provide several suggestions for substrates and substrate-film orientations for the heterostructural growth of the hitherto hypothetical anatase, brookite, and columbite polymorphs. These criteria serve as a preliminary guidance for the experimental efforts stabilizing new materials and/or polymorphs through epitaxy. The current screening algorithm is being integrated within the Materials Project online framework and data and hence publicly available.
Space-time neutronic analysis of postulated LOCA's in CANDU reactors
International Nuclear Information System (INIS)
Luxat, J.C.; Frescura, G.M.
1978-01-01
Space-time neutronic behaviour of CANDU reactors is of importance in the analysis and design of reactor safety systems. A methodology has been developed for simulating CANDU space-time neutronics with application to the analysis of postulated LOCA'S. The approach involves the efficient use of a set of computer codes which provide a capability to perform simulations ranging from detailed, accurate 3-dimensional space-time to low-cost survey calculations using point kinetics with some ''effective'' spatial content. A new, space-time kinetics code based upon a modal expansion approach is described. This code provides an inexpensive and relatively accurate scoping tool for detailed 3-dimensional space-time simulations. (author)
Verifying Stability of Dynamic Soft-Computing Systems
Wen, Wu; Napolitano, Marcello; Callahan, John
1997-01-01
Soft computing is a general term for algorithms that learn from human knowledge and mimic human skills. Example of such algorithms are fuzzy inference systems and neural networks. Many applications, especially in control engineering, have demonstrated their appropriateness in building intelligent systems that are flexible and robust. Although recent research have shown that certain class of neuro-fuzzy controllers can be proven bounded and stable, they are implementation dependent and difficult to apply to the design and validation process. Many practitioners adopt the trial and error approach for system validation or resort to exhaustive testing using prototypes. In this paper, we describe our on-going research towards establishing necessary theoretic foundation as well as building practical tools for the verification and validation of soft-computing systems. A unified model for general neuro-fuzzy system is adopted. Classic non-linear system control theory and recent results of its applications to neuro-fuzzy systems are incorporated and applied to the unified model. It is hoped that general tools can be developed to help the designer to visualize and manipulate the regions of stability and boundedness, much the same way Bode plots and Root locus plots have helped conventional control design and validation.
Space-time reference with an optical link
International Nuclear Information System (INIS)
Berceau, P; Hollberg, L; Taylor, M; Kahn, J
2016-01-01
We describe a concept for realizing a high performance space-time reference using a stable atomic clock in a precisely defined orbit and synchronizing the orbiting clock to high-accuracy atomic clocks on the ground. The synchronization would be accomplished using a two-way lasercom link between ground and space. The basic approach is to take advantage of the highest-performance cold-atom atomic clocks at national standards laboratories on the ground and to transfer that performance to an orbiting clock that has good stability and that serves as a ‘frequency-flywheel’ over time-scales of a few hours. The two-way lasercom link would also provide precise range information and thus precise orbit determination. With a well-defined orbit and a synchronized clock, the satellite could serve as a high-accuracy space-time reference, providing precise time worldwide, a valuable reference frame for geodesy, and independent high-accuracy measurements of GNSS clocks. Under reasonable assumptions, a practical system would be able to deliver picosecond timing worldwide and millimeter orbit determination, and could serve as an enabling subsystem for other proposed space-gravity missions, which are briefly reviewed. (paper)
Space/time non-commutative field theories and causality
International Nuclear Information System (INIS)
Bozkaya, H.; Fischer, P.; Pitschmann, M.; Schweda, M.; Grosse, H.; Putz, V.; Wulkenhaar, R.
2003-01-01
As argued previously, amplitudes of quantum field theories on non-commutative space and time cannot be computed using naive path integral Feynman rules. One of the proposals is to use the Gell-Mann-Low formula with time-ordering applied before performing the integrations. We point out that the previously given prescription should rather be regarded as an interaction-point time-ordering. Causality is explicitly violated inside the region of interaction. It is nevertheless a consistent procedure, which seems to be related to the interaction picture of quantum mechanics. In this framework we compute the one-loop self-energy for a space/time non-commutative φ 4 theory. Although in all intermediate steps only three-momenta play a role, the final result is manifestly Lorentz covariant and agrees with the naive calculation. Deriving the Feynman rules for general graphs, we show, however, that such a picture holds for tadpole lines only. (orig.)
Applications of Space-Time Duality
Plansinis, Brent W.
The concept of space-time duality is based on a mathematical analogy between paraxial diffraction and narrowband dispersion, and has led to the development of temporal imaging systems. The first part of this thesis focuses on the development of a temporal imaging system for the Laboratory for Laser Energetics. Using an electro-optic phase modulator as a time lens, a time-to-frequency converter is constructed capable of imaging pulses between 3 and 12 ps. Numerical simulations show how this system can be improved to image the 1-30 ps range used in OMEGA-EP. By adjusting the timing between the pulse and the sinusoidal clock of the phase modulator, the pulse spectrum can be selectively narrowed, broadened, or shifted. An experimental demonstration of this effect achieved spectral narrowing and broadening by a factor of 2. Numerical simulations show narrowing by a factor of 8 is possible with modern phase modulators. The second part of this thesis explores the space-time analog of reflection and refraction from a moving refractive index boundary. From a physics perspective, a temporal boundary breaks translational symmetry in time, requiring the momentum of the photon to remain unchanged while its energy may change. This leads to a shifting and splitting of the pulse spectrum as the boundary is crossed. Equations for the reflected and transmitted frequencies and a condition for total internal reflection are found. Two of these boundaries form a temporal waveguide, which confines the pulse to a narrow temporal window. These waveguides have a finite number of modes, which do not change during propagation. A single-mode waveguide can be created, allowing only a single pulse shape to form within the waveguide. Temporal reflection and refraction produce a frequency dependent phase shift on the incident pulse, leading to interference fringes between the incident light and the reflected light. In a waveguide, this leads to self-imaging, where the pulse shape reforms
Kepp, Kasper P
2015-10-01
Fast and accurate computation of protein stability is increasingly important for e.g. protein engineering and protein misfolding diseases, but no consensus methods exist for important proteins such as globins, and performance may depend on the type of structural input given. This paper reports benchmarking of six protein stability calculators (POPMUSIC 2.1, I-Mutant 2.0, I-Mutant 3.0, CUPSAT, SDM, and mCSM) against 134 experimental stability changes for mutations of sperm-whale myoglobin. Six different high-resolution structures were used to test structure sensitivity that may impair protein calculations. The trend accuracy of the methods decreased as I-Mutant 2.0 (R=0.64-0.65), SDM (R=0.57-0.60), POPMUSIC2.1 (R=0.54-0.57), I-Mutant 3.0 (R=0.53-0.55), mCSM (R=0.35-0.47), and CUPSAT (R=0.25-0.48). The mean signed errors increased as SDMMean absolute errors increased as I-Mutant 2.0
Charged fluid distribution in higher dimensional spheroidal space-time
Indian Academy of Sciences (India)
A general solution of Einstein field equations corresponding to a charged fluid distribution on the background of higher dimensional spheroidal space-time is obtained. The solution generates several known solutions for superdense star having spheroidal space-time geometry.
Constant scalar curvature hypersurfaces in extended Schwarzschild space-time
International Nuclear Information System (INIS)
Pareja, M. J.; Frauendiener, J.
2006-01-01
We present a class of spherically symmetric hypersurfaces in the Kruskal extension of the Schwarzschild space-time. The hypersurfaces have constant negative scalar curvature, so they are hyperboloidal in the regions of space-time which are asymptotically flat
The Space-Time Asymmetry Research (STAR) program
Buchman, Sasha
Stanford University, NASA Ames, and international partners propose the Space-Time Asymme-try Research (STAR) program, a series of three Science and Technology Development Missions, which will probe the fundamental relationships between space, time and gravity. What is the nature of space-time? Is space truly isotropic? Is the speed of light truly isotropic? If not, what is its direction and location dependency? What are the answers beyond Einstein? How will gravity and the standard model ultimately be combined? The first mission, STAR-1, will measure the absolute anisotropy of the velocity of light to one part in 1017 , derive the Kennedy-Thorndike (KT) coefficient to 7x10-10 (150-fold improvement over modern ground measurements), derive the Michelson-Morley (MM) coefficient to 10-11 (confirming the ground measurements), and derive the coefficients of Lorentz violation in the Standard Model Exten-sion (SME), in the range 7x10-17 to 10-13 (an order of magnitude improvement over ground measurements). The follow-on missions will achieve a factor of 100 higher sensitivities. The core instruments are high stability optical cavities and high accuracy gas spectroscopy frequency standards using the "NICE-OHMS technique. STAR-1 is accomplished with a fully redundant instrument flown on a standard bus, spin-stabilized spacecraft with a mission lifetime of two years. Spacecraft and instrument have a total mass of less than 180 kg and consume less than 200 W of power. STAR-1 would launch in 2015 as a secondary payload in a 650 km, sun-synchronous orbit. We describe the STAR-1 mission in detail and the STAR series in general, with a focus on how each mission will build on the development and success of the previous missions, methodically enhancing both the capabilities of the STAR instrument suite and our understanding of this important field. By coupling state-of-the-art scientific instrumentation with proven and cost-effective small satellite technology in an environment
A unifying computational framework for stability and flexibility of arousal
Directory of Open Access Journals (Sweden)
Christin eKosse
2014-10-01
Full Text Available Arousal and consciousness flexibly adjust to salient cues, but remain stable despite noise and disturbance. Diverse, highly interconnected neural networks govern the underlying transitions of behavioural state; these networks are robust but very complex. Frameworks from systems engineering provide powerful tools for understanding functional logic behind component complexity. From a general systems viewpoint, a minimum of three communicating control modules may enable flexibility and stability to coexist. Comparators would subtract current arousal from desired arousal, producing an error signal. Regulators would compute control signals from this error. Generators would convert control signals into arousal, which is fed back to comparators, to make the system noise-proof through self-correction. Can specific neurons correspond to these control elements? To explore this, here we consider the brain-wide orexin/hypocretin network, which is experimentally established to be vital for flexible and stable arousal. We discuss whether orexin neurons may act as comparators, and their target neurons as regulators and generators. Experiments are proposed for testing such predictions, based on computational simulations showing that comparators, regulators, and generators have distinct temporal signatures of activity. If some regulators integrate orexin-communicated errors, robust arousal control may be achieved via integral feedback (a basic engineering strategy for tracking a set-point despite noise. An integral feedback view also suggests functional roles for specific molecular aspects, such as differing life-spans of orexin peptides. The proposed framework offers a unifying logic for molecular, cellular, and network details of arousal systems, and provides insight into behavioral state transitions, complex behaviour, and bases for disease.
Abediseid, Walid
2012-01-01
complexity of sphere decoding for the quasi- static, lattice space-time (LAST) coded MIMO channel. Specifically, we drive an upper bound of the tail distribution of the decoder's computational complexity. We show that when the computational complexity exceeds
The topology of geodesically complete space-times
International Nuclear Information System (INIS)
Lee, C.W.
1983-01-01
Two theorems are given on the topology of geodesically complete space-times which satisfy the energy condition. Firstly, the condition that a compact embedded 3-manifold in space-time be dentless is defined in terms of causal structure. Then it is shown that a dentless 3-manifold must separate space-time, and that it must enclose a compact portion of space-time. Further, it is shown that if the dentless 3-manifold is homeomorphic to S 3 then the part of space-time that it encloses must be simply connected. (author)
A higher order space-time Galerkin scheme for time domain integral equations
Pray, Andrew J.; Beghein, Yves; Nair, Naveen V.; Cools, Kristof; Bagci, Hakan; Shanker, Balasubramaniam
2014-01-01
Stability of time domain integral equation (TDIE) solvers has remained an elusive goal formany years. Advancement of this research has largely progressed on four fronts: 1) Exact integration, 2) Lubich quadrature, 3) smooth temporal basis functions, and 4) space-time separation of convolutions with the retarded potential. The latter method's efficacy in stabilizing solutions to the time domain electric field integral equation (TD-EFIE) was previously reported for first-order surface descriptions (flat elements) and zeroth-order functions as the temporal basis. In this work, we develop the methodology necessary to extend the scheme to higher order surface descriptions as well as to enable its use with higher order basis functions in both space and time. These basis functions are then used in a space-time Galerkin framework. A number of results are presented that demonstrate convergence in time. The viability of the space-time separation method in producing stable results is demonstrated experimentally for these examples.
MHC I stabilizing potential of computer-designed octapeptides.
Wisniewska, Joanna M; Jäger, Natalie; Freier, Anja; Losch, Florian O; Wiesmüller, Karl-Heinz; Walden, Peter; Wrede, Paul; Schneider, Gisbert; Hiss, Jan A
2010-01-01
Experimental results are presented for 180 in silico designed octapeptide sequences and their stabilizing effects on the major histocompatibility class I molecule H-2K(b). Peptide sequence design was accomplished by a combination of an ant colony optimization algorithm with artificial neural network classifiers. Experimental tests yielded nine H-2K(b) stabilizing and 171 nonstabilizing peptides. 28 among the nonstabilizing octapeptides contain canonical motif residues known to be favorable for MHC I stabilization. For characterization of the area covered by stabilizing and non-stabilizing octapeptides in sequence space, we visualized the distribution of 100,603 octapeptides using a self-organizing map. The experimental results present evidence that the canonical sequence motives of the SYFPEITHI database on their own are insufficient for predicting MHC I protein stabilization.
MHC I Stabilizing Potential of Computer-Designed Octapeptides
Directory of Open Access Journals (Sweden)
Joanna M. Wisniewska
2010-01-01
Full Text Available Experimental results are presented for 180 in silico designed octapeptide sequences and their stabilizing effects on the major histocompatibility class I molecule H-2Kb. Peptide sequence design was accomplished by a combination of an ant colony optimization algorithm with artificial neural network classifiers. Experimental tests yielded nine H-2Kb stabilizing and 171 nonstabilizing peptides. 28 among the nonstabilizing octapeptides contain canonical motif residues known to be favorable for MHC I stabilization. For characterization of the area covered by stabilizing and non-stabilizing octapeptides in sequence space, we visualized the distribution of 100,603 octapeptides using a self-organizing map. The experimental results present evidence that the canonical sequence motives of the SYFPEITHI database on their own are insufficient for predicting MHC I protein stabilization.
Scanless nonlinear optical microscope for image reconstruction and space-time correlation analysis
Ceffa, N. G.; Radaelli, F.; Pozzi, P.; Collini, M.; Sironi, L.; D'alfonso, L.; Chirico, G.
2017-06-01
Optical Microscopy has been applied to life science from its birth and reached widespread application due to its major advantages: limited perturbation of the biological tissue and the easy accessibility of the light sources. However, as the spatial and time resolution requirements and the time stability of the microscopes increase, researchers are struggling against some of its limitations: limited transparency and the refractivity of the living tissue to light and the field perturbations induced by the path in the tissue. We have developed a compact stand-alone, completely scan-less, optical setup that allows to acquire non-linear excitation images and to measure the sample dynamics simultaneously on an ensemble of arbitrary chosen regions of interests. The image is obtained by shining a square array of spots on the sample obtained by a spatial light modulator and by shifting it (10 ms refresh time) on the sample. The final image is computed from the superposition of (100-1000) images. Filtering procedures can be applied to the raw images of the excitation array before building the image. We discuss results that show how this setup can be used for the correction of wave front aberrations induced by turbid samples (such as living tissues) and for the computation of space-time cross-correlations in complex networks.
Recursive evaluation of space-time lattice Green's functions
International Nuclear Information System (INIS)
De Hon, Bastiaan P; Arnold, John M
2012-01-01
Up to a multiplicative constant, the lattice Green's function (LGF) as defined in condensed matter physics and lattice statistical mechanics is equivalent to the Z-domain counterpart of the finite-difference time-domain Green's function (GF) on a lattice. Expansion of a well-known integral representation for the LGF on a ν-dimensional hyper-cubic lattice in powers of Z −1 and application of the Chu–Vandermonde identity results in ν − 1 nested finite-sum representations for discrete space-time GFs. Due to severe numerical cancellations, these nested finite sums are of little practical use. For ν = 2, the finite sum may be evaluated in closed form in terms of a generalized hypergeometric function. For special lattice points, that representation simplifies considerably, while on the other hand the finite-difference stencil may be used to derive single-lattice-point second-order recurrence schemes for generating 2D discrete space-time GF time sequences on the fly. For arbitrary symbolic lattice points, Zeilberger's algorithm produces a third-order recurrence operator with polynomial coefficients of the sixth degree. The corresponding recurrence scheme constitutes the most efficient numerical method for the majority of lattice points, in spite of the fact that for explicit numeric lattice points the associated third-order recurrence operator is not the minimum recurrence operator. As regards the asymptotic bounds for the possible solutions to the recurrence scheme, Perron's theorem precludes factorial or exponential growth. Along horizontal lattices directions, rapid initial growth does occur, but poses no problems in augmented dynamic-range fixed precision arithmetic. By analysing long-distance wave propagation along a horizontal lattice direction, we have concluded that the chirp-up oscillations of the discrete space-time GF are the root cause of grid dispersion anisotropy. With each factor of ten increase in the lattice distance, one would have to roughly
Empty space-times with separable Hamilton-Jacobi equation
International Nuclear Information System (INIS)
Collinson, C.D.; Fugere, J.
1977-01-01
All empty space-times admitting a one-parameter group of motions and in which the Hamilton-Jacobi equation is (partially) separable are obtained. Several different cases of such empty space-times exist and the Riemann tensor is found to be either type D or N. The results presented here complete the search for empty space-times with separable Hamilton-Jacobi equation. (author)
A short history of fractal-Cantorian space-time
International Nuclear Information System (INIS)
Marek-Crnjac, L.
2009-01-01
The article attempts to give a short historical overview of the discovery of fractal-Cantorian space-time starting from the 17th century up to the present. In the last 25 years a great number of scientists worked on fractal space-time notably Garnet Ord in Canada, Laurent Nottale in France and Mohamed El Naschie in England who gave an exact mathematical procedure for the derivation of the dimensionality and curvature of fractal space-time fuzzy manifold.
Some Peculiarities of Newton-Hooke Space-Times
Tian, Yu
2011-01-01
Newton-Hooke space-times are the non-relativistic limit of (anti-)de Sitter space-times. We investigate some peculiar facts about the Newton-Hooke space-times, among which the "extraordinary Newton-Hooke quantum mechanics" and the "anomalous Newton-Hooke space-times" are discussed in detail. Analysis on the Lagrangian/action formalism is performed in the discussion of the Newton-Hooke quantum mechanics, where the path integral point of view plays an important role, and the physically measurab...
Black Hole Space-time In Dark Matter Halo
Xu, Zhaoyi; Hou, Xian; Gong, Xiaobo; Wang, Jiancheng
2018-01-01
For the first time, we obtain the analytical form of black hole space-time metric in dark matter halo for the stationary situation. Using the relation between the rotation velocity (in the equatorial plane) and the spherical symmetric space-time metric coefficient, we obtain the space-time metric for pure dark matter. By considering the dark matter halo in spherical symmetric space-time as part of the energy-momentum tensors in the Einstein field equation, we then obtain the spherical symmetr...
Stabilization of computational procedures for constrained dynamical systems
Park, K. C.; Chiou, J. C.
1988-01-01
A new stabilization method of treating constraints in multibody dynamical systems is presented. By tailoring a penalty form of the constraint equations, the method achieves stabilization without artificial damping and yields a companion matrix differential equation for the constraint forces; hence, the constraint forces are obtained by integrating the companion differential equation for the constraint forces in time. A principal feature of the method is that the errors committed in each constraint condition decay with its corresponding characteristic time scale associated with its constraint force. Numerical experiments indicate that the method yields a marked improvement over existing techniques.
Conserved quantities for stationary Einstein-Maxwell space-times
International Nuclear Information System (INIS)
Esposito, F.P.; Witten, L.
1978-01-01
It is shown that every stationary Einstein-Maxwell space-time has eight divergence-free vector fields and these are isolated in general form. The vector fields and associated conserved quantities are calculated for several families of space-times. (Auth.)
Quantum space-times in the year 2002
Indian Academy of Sciences (India)
These ideas of space-time are suggested from developments in fuzzy physics, string theory, and deformation quantization. The review focuses on the ideas coming from fuzzy physics. We ﬁnd models of quantum space-time like fuzzy 4 on which states cannot be localized, but which ﬂuctuate into other manifolds like CP3.
Feynman propagator and space-time transformation technique
International Nuclear Information System (INIS)
Nassar, A.B.
1987-01-01
We evaluate the exact propagator for the time-dependent two-dimensional charged harmonic oscillator in a time-varying magnetic field, by taking direct recourse to the corresponding Schroedinger equation. Through the usage of an appropriate space-time transformation, we show that such a propagator can be obtained from the free propagator in the new space-time coordinate system. (orig.)
Space-time algebra for the generalization of gravitational field
Indian Academy of Sciences (India)
The Maxwell–Proca-like field equations of gravitolectromagnetism are formulated using space-time algebra (STA). The gravitational wave equation with massive gravitons and gravitomagnetic monopoles has been derived in terms of this algebra. Using space-time algebra, the most generalized form of ...
Causal boundary for stably causal space-times
International Nuclear Information System (INIS)
Racz, I.
1987-12-01
The usual boundary constructions for space-times often yield an unsatisfactory boundary set. This problem is reviewed and a new solution is proposed. An explicit identification rule is given on the set of the ideal points of the space-time. This construction leads to a satisfactory boundary point set structure for stably causal space-times. The topological properties of the resulting causal boundary construction are examined. For the stably causal space-times each causal curve has a unique endpoint on the boundary set according to the extended Alexandrov topology. The extension of the space-time through the boundary is discussed. To describe the singularities the defined boundary sets have to be separated into two disjoint sets. (D.Gy.) 8 refs
Quantum Space-Time Deformed Symmetries Versus Broken Symmetries
Amelino-Camelia, G
2002-01-01
Several recent studies have concerned the faith of classical symmetries in quantum space-time. In particular, it appears likely that quantum (discretized, noncommutative,...) versions of Minkowski space-time would not enjoy the classical Lorentz symmetries. I compare two interesting cases: the case in which the classical symmetries are "broken", i.e. at the quantum level some classical symmetries are lost, and the case in which the classical symmetries are "deformed", i.e. the quantum space-time has as many symmetries as its classical counterpart but the nature of these symmetries is affected by the space-time quantization procedure. While some general features, such as the emergence of deformed dispersion relations, characterize both the symmetry-breaking case and the symmetry-deformation case, the two scenarios are also characterized by sharp differences, even concerning the nature of the new effects predicted. I illustrate this point within an illustrative calculation concerning the role of space-time symm...
Stochastic quantization of geometrodynamic curved space-time
International Nuclear Information System (INIS)
Prugovecki, E.
1981-01-01
It is proposed that quantum rather than classical test particles be used in recent operational definitions of space-time. In the resulting quantum space-time the role of test particle trajectories is taken over by propagators. The introduced co-ordinate values are stochastic rather than deterministic, the afore-mentioned propagators providing probability amplitudes describing fluctuations of measured co-ordinates around their mean values. It is shown that, if a geometrodynamic point of view based on 3 + 1 foliations of space-time is adopted, self-consistent families of propagators for quantum test particles in free fall can be constructed. The resulting formalism for quantum space-time is outlined and the quantization of spatially flat Robertson-Walker space-times is provided as an illustration. (author)
Global Stability of an Epidemic Model of Computer Virus
Directory of Open Access Journals (Sweden)
Xiaofan Yang
2014-01-01
Full Text Available With the rapid popularization of the Internet, computers can enter or leave the Internet increasingly frequently. In fact, no antivirus software can detect and remove all sorts of computer viruses. This implies that viruses would persist on the Internet. To better understand the spread of computer viruses in these situations, a new propagation model is established and analyzed. The unique equilibrium of the model is globally asymptotically stable, in accordance with the reality. A parameter analysis of the equilibrium is also conducted.
Guidelines for Computing Longitudinal Dynamic Stability Characteristics of a Subsonic Transport
Thompson, Joseph R.; Frank, Neal T.; Murphy, Patrick C.
2010-01-01
A systematic study is presented to guide the selection of a numerical solution strategy for URANS computation of a subsonic transport configuration undergoing simulated forced oscillation about its pitch axis. Forced oscillation is central to the prevalent wind tunnel methodology for quantifying aircraft dynamic stability derivatives from force and moment coefficients, which is the ultimate goal for the computational simulations. Extensive computations are performed that lead in key insights of the critical numerical parameters affecting solution convergence. A preliminary linear harmonic analysis is included to demonstrate the potential of extracting dynamic stability derivatives from computational solutions.
On Numerical Stability in Large Scale Linear Algebraic Computations
Czech Academy of Sciences Publication Activity Database
Strakoš, Zdeněk; Liesen, J.
2005-01-01
Roč. 85, č. 5 (2005), s. 307-325 ISSN 0044-2267 R&D Projects: GA AV ČR 1ET400300415 Institutional research plan: CEZ:AV0Z10300504 Keywords : linear algebraic systems * eigenvalue problems * convergence * numerical stability * backward error * accuracy * Lanczos method * conjugate gradient method * GMRES method Subject RIV: BA - General Mathematics Impact factor: 0.351, year: 2005
Conical singularities in AdS space time
International Nuclear Information System (INIS)
Ferreira, Cristine Nunes
2011-01-01
Full text: In recent years, the study of conformal gauge theories from 10-D has been motivated by the AdS d+1 /CFT d correspondence, first conjectured by J. Maldacena. The aim of this work is to consider the d = 4 case by analysing the configuration of the N coincident D3 branes. In this context, the work shows that there is a duality between type IIB string theory in AdS 5 x S 5 and N = 4 SU(N) Super Yang-Mills Theory in the IR. The AdS 5 /CFT 4 correspondence brought also new approaches to the strong coupling problem in QCD. Nowadays, there is a whole line of works that focus on the low dimensional correspondence AdS 4 /CFT 3 , like the application to graphene and topological insulators, and the AdS 3 /CFT 2 correspondence, related with the entanglement entropy. In this work, we consider the vortex configuration solution to the AdS 4 and AdS 3 space-time. The most important motivation is to discuss the boundary theory resulting from these solutions. We have examined a straightforward approach to a holographic computation of the graphene and entanglement entropy in the presence of the conical singularity. After this analysis, we consider the scalar field in the bulk in the presence of this metrics and work out the compactification modes. Taking the holographic point of view, we study and discuss the resulting Green function. (author)
Voluble: a space-time diagram of the solar system
Aguilera, Julieta C.; SubbaRao, Mark U.
2008-02-01
Voluble is a dynamic space-time diagram of the solar system. Voluble is designed to help users understand the relationship between space and time in the motion of the planets around the sun. Voluble is set in virtual reality to relate these movements to our experience of immediate space. Beyond just the visual, understanding dynamic systems is naturally associated to the articulation of our bodies as we perform a number of complex calculations, albeit unconsciously, to deal with simple tasks. Such capabilities encompass spatial perception and memory. Voluble investigates the balance between the visually abstract and the spatially figurative in immersive development to help illuminate phenomena that are beyond the reach of human scale and time. While most diagrams, even computer-based interactive ones, are flat, three-dimensional real-time virtual reality representations are closer to our experience of space. The representation can be seen as if it was "really there," engaging a larger number of cues pertaining to our everyday spatial experience.
Collision-free gases in spatially homogeneous space-times
International Nuclear Information System (INIS)
Maartens, R.; Maharaj, S.D.
1985-01-01
The kinematical and dynamical properties of one-component collision-free gases in spatially homogeneous, locally rotationally symmetric (LRS) space-times are analyzed. Following Ray and Zimmerman [Nuovo Cimento B 42, 183 (1977)], it is assumed that the distribution function f of the gas inherits the symmetry of space-time, in order to construct solutions of Liouville's equation. The redundancy of their further assumption that f be based on Killing vector constants of the motion is shown. The Ray and Zimmerman results for Kantowski--Sachs space-time are extended to all spatially homogeneous LRS space-times. It is shown that in all these space-times the kinematic average four-velocity u/sup i/ can be tilted relative to the homogeneous hypersurfaces. This differs from the perfect fluid case, in which only one space-time admits tilted u/sup i/, as shown by King and Ellis [Commun. Math. Phys. 31, 209 (1973)]. As a consequence, it is shown that all space-times admit nonzero acceleration and heat flow, while a subclass admits nonzero vorticity. The stress π/sub i/j is proportional to the shear sigma/sub i/j by virtue of the invariance of the distribution function. The evolution of tilt and the existence of perfect fluid solutions is also discussed
On the existence of conformal Killing vectors for ST-homogeneous Godel type space-times
Energy Technology Data Exchange (ETDEWEB)
Parra, Y.; Patino, A.; Percoco, U. [Laboratorio de Fisica Teorica, Facultad de Ciencias Universidad de los Andes, Merida 5101 (Venezuela); Tsamparlis, M. [seccion de Astronomia-Astrofisica-Mecanica, Universidad de Atenas, Atenas 157 83 (Greece)
2006-07-01
Tsamparlis with another authors have developed a systematic method for computing of the conformal algebra of 1+3 space-times. The proper CKV's are found in terms of gradient CKVs of the 3-space. In this paper we apply Tsamparlis' results to the study CKVs of the Godel ST-Homogeneous type spacetimes. We find that the only space-time admitting proper CKV's is the ST-Homogeneous Godel type with m{sup 2} = 4{omega}{sup 2} (RT). (Author)
Metric space construction for the boundary of space-time
International Nuclear Information System (INIS)
Meyer, D.A.
1986-01-01
A distance function between points in space-time is defined and used to consider the manifold as a topological metric space. The properties of the distance function are investigated: conditions under which the metric and manifold topologies agree, the relationship with the causal structure of the space-time and with the maximum lifetime function of Wald and Yip, and in terms of the space of causal curves. The space-time is then completed as a topological metric space; the resultant boundary is compared with the causal boundary and is also calculated for some pertinent examples
Space-Time Geometry of Quark and Strange Quark Matter
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
We study quark and strange quark matter in the context of general relativity. For this purpose, we solve Einstein's field equations for quark and strange quark matter in spherical symmetric space-times. We analyze strange quark matter for the different equations of state (EOS) in the spherical symmetric space-times, thus we are able to obtain the space-time geometries of quark and strange quark matter. Also, we discuss die features of the obtained solutions. The obtained solutions are consistent with the results of Brookhaven Laboratory, i.e. the quark-gluon plasma has a vanishing shear (i.e. quark-gluon plasma is perfect).
A composite model of the space-time and 'colors'
International Nuclear Information System (INIS)
Terazawa, Hidezumi.
1987-03-01
A pregeometric and pregauge model of the space-time and ''colors'' in which the space-time metric and ''color'' gauge fields are both composite is presented. By the non-triviality of the model, the number of space-time dimensions is restricted to be not larger than the number of ''colors''. The long conjectured space-color correspondence is realized in the model action of the Nambu-Goto type which is invariant under both general-coordinate and local-gauge transformations. (author)
Approaching space-time through velocity in doubly special relativity
International Nuclear Information System (INIS)
Aloisio, R.; Galante, A.; Grillo, A.F.; Luzio, E.; Mendez, F.
2004-01-01
We discuss the definition of velocity as dE/d vertical bar p vertical bar, where E, p are the energy and momentum of a particle, in doubly special relativity (DSR). If this definition matches dx/dt appropriate for the space-time sector, then space-time can in principle be built consistently with the existence of an invariant length scale. We show that, within different possible velocity definitions, a space-time compatible with momentum-space DSR principles cannot be derived
Ghost neutrinos as test fields in curved space-time
International Nuclear Information System (INIS)
Audretsch, J.
1976-01-01
Without restricting to empty space-times, it is shown that ghost neutrinos (their energy-momentum tensor vanishes) can only be found in algebraically special space-times with a neutrino flux vector parallel to one of the principal null vectors of the conformal tensor. The optical properties are studied. There are no ghost neutrinos in the Kerr-Newman and in spherically symmetric space-times. The example of a non-vacuum gravitational pp-wave accompanied by a ghost neutrino pp-wave is discussed. (Auth.)
Quaternion wave equations in curved space-time
Edmonds, J. D., Jr.
1974-01-01
The quaternion formulation of relativistic quantum theory is extended to include curvilinear coordinates and curved space-time in order to provide a framework for a unified quantum/gravity theory. Six basic quaternion fields are identified in curved space-time, the four-vector basis quaternions are identified, and the necessary covariant derivatives are obtained. Invariant field equations are derived, and a general invertable coordinate transformation is developed. The results yield a way of writing quaternion wave equations in curvilinear coordinates and curved space-time as well as a natural framework for solving the problem of second quantization for gravity.
The Stabilization, Exploration, and Expression of Computer Game History
Kaltman, Eric
2017-01-01
Computer games are now a significant cultural phenomenon, and a significant artistic output of humanity. However, little effort and attention have been paid to how the medium of games and interactive software developed, and even less to the historical storage of software development documentation. This thesis borrows methodologies and practices…
Dynamic stability calculations for power grids employing a parallel computer
Energy Technology Data Exchange (ETDEWEB)
Schmidt, K
1982-06-01
The aim of dynamic contingency calculations in power systems is to estimate the effects of assumed disturbances, such as loss of generation. Due to the large dimensions of the problem these simulations require considerable computing time and costs, to the effect that they are at present only used in a planning state but not for routine checks in power control stations. In view of the homogeneity of the problem, where a multitude of equal generator models, having different parameters, are to be integrated simultaneously, the use of a parallel computer looks very attractive. The results of this study employing a prototype parallel computer (SMS 201) are presented. It consists of up to 128 equal microcomputers bus-connected to a control computer. Each of the modules is programmed to simulate a node of the power grid. Generators with their associated control are represented by models of 13 states each. Passive nodes are complemented by 'phantom'-generators, so that the whole power grid is homogenous, thus removing the need for load-flow-iterations. Programming of microcomputers is essentially performed in FORTRAN.
An analytic algorithm for the space-time fractional reaction-diffusion equation
Directory of Open Access Journals (Sweden)
M. G. Brikaa
2015-11-01
Full Text Available In this paper, we solve the space-time fractional reaction-diffusion equation by the fractional homotopy analysis method. Solutions of different examples of the reaction term will be computed and investigated. The approximation solutions of the studied models will be put in the form of convergent series to be easily computed and simulated. Comparison with the approximation solution of the classical case of the studied modeled with their approximation errors will also be studied.
Differential Space-Time Modulation for Wideband Wireless Networks
National Research Council Canada - National Science Library
Li, Hongbin
2006-01-01
.... The objective was to provide full spatio-spectral diversity and coding gain at affordable decoding complexity without the burden of estimating the underlying space-time frequency-selective channel...
Problems of space-time behaviour of nuclear reactors
International Nuclear Information System (INIS)
Obradovic, D.
1966-01-01
This paper covers a review of literature and mathematical methods applied for space-time behaviour of nuclear reactors. The review of literature is limited to unresolved problems and trends of actual research in the field of reactor physics [sr
Quantum Dynamics of Test Particle in Curved Space-Time
International Nuclear Information System (INIS)
Piechocki, W.
2002-01-01
To reveal the nature of space-time singularities of removable type we examine classical and quantum dynamics of a free particle in the Sitter type spacetimes. Consider space-times have different topologies otherwise are isometric. Our systems are integrable and we present analytic solutions of the classical dynamics. We quantize the systems by making use of the group theoretical method: we find an essentially self-adjoint representation of the algebra of observables integrable to the irreducible unitarity representation of the symmetry group of each consider gravitational system. The massless particle dynamics is obtained in the zero-mass limit of the massive case. Global properties of considered gravitational systems are of primary importance for the quantization procedure. Systems of a particle in space-times with removable singularities appear to be quantizable. We give specific proposal for extension of our analysis to space-times with essential type singularities. (author)
Point-like Particles in Fuzzy Space-time
Francis, Charles
1999-01-01
This paper is withdrawn as I am no longer using the term "fuzzy space- time" to describe the uncertainty in co-ordinate systems implicit in quantum logic. Nor am I using the interpretation that quantum logic can be regarded as a special case of fuzzy logic. This is because there are sufficient differences between quantum logic and fuzzy logic that the explanation is confusing. I give an interpretation of quantum logic in "A Theory of Quantum Space-time"
Renormalization of the δ expansion in curved space-time
International Nuclear Information System (INIS)
Cho, H.T.
1991-01-01
Renormalization of a recently proposed δ expansion for a self-interacting scalar field theory in curved space-time is examined. The explicit calculation is carried out up to order δ 2 , which indicates that the expansion is renormalizable, but reduces to essentially the λφ 4 theory when the cutoff is removed. A similar conclusion has been reached in a previous paper where the case of flat space-time is considered
On the minimum uncertainty of space-time geodesics
International Nuclear Information System (INIS)
Diosi, L.; Lukacs, B.
1989-10-01
Although various attempts for systematic quantization of the space-time geometry ('gravitation') have appeared, none of them is considered fully consistent or final. Inspired by a construction of Wigner, the quantum relativistic limitations of measuring the metric tensor of a certain space-time were calculated. The result is suggested to be estimate for fluctuations of g ab whose rigorous determination will be a subject of a future relativistic quantum gravity. (author) 11 refs
Quantum field theory in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Davies, P C.W. [King' s Coll., London (UK)
1976-09-30
It is stated that recent theoretical developments indicate that the presence of gravity (curved space-time) can give rise to important new quantum effects, such as cosmological particle production and black-hole evaporation. These processes suggest intriguing new relations between quantum theory, thermodynamics and space-time structure and encourage the hope that a better understanding of a full quantum theory of gravity may emerge from this approach.
Quantum relativity theory and quantum space-time
International Nuclear Information System (INIS)
Banai, M.
1984-01-01
A quantum relativity theory formulated in terms of Davis' quantum relativity principle is outlined. The first task in this theory as in classical relativity theory is to model space-time, the arena of natural processes. It is shown that the quantum space-time models of Banai introduced in another paper is formulated in terms of Davis's quantum relativity. The recently proposed classical relativistic quantum theory of Prugovecki and his corresponding classical relativistic quantum model of space-time open the way to introduce, in a consistent way, the quantum space-time model (the quantum substitute of Minkowski space) of Banai proposed in the paper mentioned. The goal of quantum mechanics of quantum relativistic particles living in this model of space-time is to predict the rest mass system properties of classically relativistic (massive) quantum particles (''elementary particles''). The main new aspect of this quantum mechanics is that it provides a true mass eigenvalue problem, and that the excited mass states of quantum relativistic particles can be interpreted as elementary particles. The question of field theory over quantum relativistic model of space-time is also discussed. Finally it is suggested that ''quarks'' should be considered as quantum relativistic particles. (author)
An evaluation of space time cube representation of spatiotemporal patterns.
Kristensson, Per Ola; Dahlbäck, Nils; Anundi, Daniel; Björnstad, Marius; Gillberg, Hanna; Haraldsson, Jonas; Mårtensson, Ingrid; Nordvall, Mathias; Ståhl, Josefine
2009-01-01
Space time cube representation is an information visualization technique where spatiotemporal data points are mapped into a cube. Information visualization researchers have previously argued that space time cube representation is beneficial in revealing complex spatiotemporal patterns in a data set to users. The argument is based on the fact that both time and spatial information are displayed simultaneously to users, an effect difficult to achieve in other representations. However, to our knowledge the actual usefulness of space time cube representation in conveying complex spatiotemporal patterns to users has not been empirically validated. To fill this gap, we report on a between-subjects experiment comparing novice users' error rates and response times when answering a set of questions using either space time cube or a baseline 2D representation. For some simple questions, the error rates were lower when using the baseline representation. For complex questions where the participants needed an overall understanding of the spatiotemporal structure of the data set, the space time cube representation resulted in on average twice as fast response times with no difference in error rates compared to the baseline. These results provide an empirical foundation for the hypothesis that space time cube representation benefits users analyzing complex spatiotemporal patterns.
MODELING OF THE CONTROLLED TRACTION POWER SUPPLY SYSTEM IN THE SPACE-TIME COORDINATES
Directory of Open Access Journals (Sweden)
Dmitry BOSYI
2017-09-01
Full Text Available The problems of the traction power supply system calculation are considered in the article. The authors proposed the space-time model, which is based on the analytical functions of the current- and voltage-drop distributions in the contact network. The usage of the proposed model is shown for the control law calculation both to stabilize the voltage at the pantographs of the electric rolling stocks and to reduce the power losses.
Arbitrary Dimension Convection-Diffusion Schemes for Space-Time Discretizations
Energy Technology Data Exchange (ETDEWEB)
Bank, Randolph E. [Univ. of California, San Diego, CA (United States); Vassilevski, Panayot S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zikatanov, Ludmil T. [Bulgarian Academy of Sciences, Sofia (Bulgaria)
2016-01-20
This note proposes embedding a time dependent PDE into a convection-diffusion type PDE (in one space dimension higher) with singularity, for which two discretization schemes, the classical streamline-diffusion and the EAFE (edge average finite element) one, are investigated in terms of stability and error analysis. The EAFE scheme, in particular, is extended to be arbitrary order which is of interest on its own. Numerical results, in combined space-time domain demonstrate the feasibility of the proposed approach.
Shell stability analysis in a computer aided engineering (CAE) environment
Arbocz, J.; Hol, J. M. A. M.
1993-01-01
The development of 'DISDECO', the Delft Interactive Shell DEsign COde is described. The purpose of this project is to make the accumulated theoretical, numerical and practical knowledge of the last 25 years or so readily accessible to users interested in the analysis of buckling sensitive structures. With this open ended, hierarchical, interactive computer code the user can access from his workstation successively programs of increasing complexity. The computational modules currently operational in DISDECO provide the prospective user with facilities to calculate the critical buckling loads of stiffened anisotropic shells under combined loading, to investigate the effects the various types of boundary conditions will have on the critical load, and to get a complete picture of the degrading effects the different shapes of possible initial imperfections might cause, all in one interactive session. Once a design is finalized, its collapse load can be verified by running a large refined model remotely from behind the workstation with one of the current generation 2-dimensional codes, with advanced capabilities to handle both geometric and material nonlinearities.
A discrete classical space-time could require 6 extra-dimensions
Guillemant, Philippe; Medale, Marc; Abid, Cherifa
2018-01-01
We consider a discrete space-time in which conservation laws are computed in such a way that the density of information is kept bounded. We use a 2D billiard as a toy model to compute the uncertainty propagation in ball positions after every shock and the corresponding loss of phase information. Our main result is the computation of a critical time step above which billiard calculations are no longer deterministic, meaning that a multiverse of distinct billiard histories begins to appear, caused by the lack of information. Then, we highlight unexpected properties of this critical time step and the subsequent exponential evolution of the number of histories with time, to observe that after certain duration all billiard states could become possible final states, independent of initial conditions. We conclude that if our space-time is really a discrete one, one would need to introduce extra-dimensions in order to provide supplementary constraints that specify which history should be played.
International Nuclear Information System (INIS)
Tupper, B.O.J.
1983-01-01
The work of a previous article is extended to show that space-times which are the exact solutions of the field equations for a perfect fluid also may be exact solutions of the field equations for a viscous magnetohydrodynamic fluid. Conditions are found for this equivalence to exist and viscous magnetohydrodynamic solutions are found for a number of known perfect fluid space-times. (author)
Space-time least-squares Petrov-Galerkin projection in nonlinear model reduction.
Energy Technology Data Exchange (ETDEWEB)
Choi, Youngsoo [Sandia National Laboratories (SNL-CA), Livermore, CA (United States). Extreme-scale Data Science and Analytics Dept.; Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Carlberg, Kevin Thomas [Sandia National Laboratories (SNL-CA), Livermore, CA (United States). Extreme-scale Data Science and Analytics Dept.
2017-09-01
Our work proposes a space-time least-squares Petrov-Galerkin (ST-LSPG) projection method for model reduction of nonlinear dynamical systems. In contrast to typical nonlinear model-reduction methods that first apply Petrov-Galerkin projection in the spatial dimension and subsequently apply time integration to numerically resolve the resulting low-dimensional dynamical system, the proposed method applies projection in space and time simultaneously. To accomplish this, the method first introduces a low-dimensional space-time trial subspace, which can be obtained by computing tensor decompositions of state-snapshot data. The method then computes discrete-optimal approximations in this space-time trial subspace by minimizing the residual arising after time discretization over all space and time in a weighted ℓ^{2}-norm. This norm can be de ned to enable complexity reduction (i.e., hyper-reduction) in time, which leads to space-time collocation and space-time GNAT variants of the ST-LSPG method. Advantages of the approach relative to typical spatial-projection-based nonlinear model reduction methods such as Galerkin projection and least-squares Petrov-Galerkin projection include: (1) a reduction of both the spatial and temporal dimensions of the dynamical system, (2) the removal of spurious temporal modes (e.g., unstable growth) from the state space, and (3) error bounds that exhibit slower growth in time. Numerical examples performed on model problems in fluid dynamics demonstrate the ability of the method to generate orders-of-magnitude computational savings relative to spatial-projection-based reduced-order models without sacrificing accuracy.
ELECTRODYNAMIC STABILITY COMPUTATIONS FOR FLEXIBLE CONDUCTORS OF THE AERIAL LINES
Directory of Open Access Journals (Sweden)
I. I. Sergey
2015-01-01
Full Text Available In aerial transmission lines aluminium multiwire conductors are in use. Owing to their flexible design the electrodynamic effect of short circuit currents may lead to intolerable mutual rendezvous and even cross-whipping of the phase conductors. The increasing motion of the conductors caused by effect of the short-circuit electrodynamic force impulse is accompanied by the dynamic load impact affecting the conductors, insulating and supporting constructions of the aerial lines. Intensity of the short-circuit currents electrodynamic impact on the flexible conductors depends on the short circuit current magnitude. For research into electrodynamic endurance of the conductors of the aerial lines located at the vertices of arbitrary triangle with spans of a large length, the authors assume the conductor analytical model in the form of a flexible tensile thread whose mass is distributed evenly lengthwise the conductor. With this analytical model, by the action of the imposed forces the conductor assumes the form conditioned by the diagram of applied external forces, and resists neither bending nor torsion. The initial conditions calculation task reduces to solving the flexible thread statics equations. The law of motion of the conductor marginal points comes out of the conjoint solution of dynamic equations of the conductor and structural components of the areal electric power lines. Based on the proposed algorithm, the researchers of the Chair of the Electric Power Stations of BNTU developed a software program LINEDYS+, which in its characteristics yields to no foreign analogs, e. g. SAMSEF. To calculate the initial conditions they modified a software program computing the flexible conductor mechanics named MR 21. The conductor short-circuit electrodynamic interaction estimation considers structural elements of the areal lines, ice and wind loads, objective parameters of the short circuit. The software programs are accommodated with the simple and
Stability and Hopf Bifurcation in a Delayed SEIRS Worm Model in Computer Network
Directory of Open Access Journals (Sweden)
Zizhen Zhang
2013-01-01
Full Text Available A delayed SEIRS epidemic model with vertical transmission in computer network is considered. Sufficient conditions for local stability of the positive equilibrium and existence of local Hopf bifurcation are obtained by analyzing distribution of the roots of the associated characteristic equation. Furthermore, the direction of the local Hopf bifurcation and the stability of the bifurcating periodic solutions are determined by using the normal form theory and center manifold theorem. Finally, a numerical example is presented to verify the theoretical analysis.
Stability and Hopf Bifurcation for a Delayed SLBRS Computer Virus Model
Directory of Open Access Journals (Sweden)
Zizhen Zhang
2014-01-01
Full Text Available By incorporating the time delay due to the period that computers use antivirus software to clean the virus into the SLBRS model a delayed SLBRS computer virus model is proposed in this paper. The dynamical behaviors which include local stability and Hopf bifurcation are investigated by regarding the delay as bifurcating parameter. Specially, direction and stability of the Hopf bifurcation are derived by applying the normal form method and center manifold theory. Finally, an illustrative example is also presented to testify our analytical results.
Stability and Hopf bifurcation for a delayed SLBRS computer virus model.
Zhang, Zizhen; Yang, Huizhong
2014-01-01
By incorporating the time delay due to the period that computers use antivirus software to clean the virus into the SLBRS model a delayed SLBRS computer virus model is proposed in this paper. The dynamical behaviors which include local stability and Hopf bifurcation are investigated by regarding the delay as bifurcating parameter. Specially, direction and stability of the Hopf bifurcation are derived by applying the normal form method and center manifold theory. Finally, an illustrative example is also presented to testify our analytical results.
Linear stability analysis of detonations via numerical computation and dynamic mode decomposition
Kabanov, Dmitry; Kasimov, Aslan R.
2018-01-01
We introduce a new method to investigate linear stability of gaseous detonations that is based on an accurate shock-fitting numerical integration of the linearized reactive Euler equations with a subsequent analysis of the computed solution via the dynamic mode decomposition. The method is applied to the detonation models based on both the standard one-step Arrhenius kinetics and two-step exothermic-endothermic reaction kinetics. Stability spectra for all cases are computed and analyzed. The new approach is shown to be a viable alternative to the traditional normal-mode analysis used in detonation theory.
Linear stability analysis of detonations via numerical computation and dynamic mode decomposition
Kabanov, Dmitry I.
2017-12-08
We introduce a new method to investigate linear stability of gaseous detonations that is based on an accurate shock-fitting numerical integration of the linearized reactive Euler equations with a subsequent analysis of the computed solution via the dynamic mode decomposition. The method is applied to the detonation models based on both the standard one-step Arrhenius kinetics and two-step exothermic-endothermic reaction kinetics. Stability spectra for all cases are computed and analyzed. The new approach is shown to be a viable alternative to the traditional normal-mode analysis used in detonation theory.
Linear stability analysis of detonations via numerical computation and dynamic mode decomposition
Kabanov, Dmitry
2018-03-20
We introduce a new method to investigate linear stability of gaseous detonations that is based on an accurate shock-fitting numerical integration of the linearized reactive Euler equations with a subsequent analysis of the computed solution via the dynamic mode decomposition. The method is applied to the detonation models based on both the standard one-step Arrhenius kinetics and two-step exothermic-endothermic reaction kinetics. Stability spectra for all cases are computed and analyzed. The new approach is shown to be a viable alternative to the traditional normal-mode analysis used in detonation theory.
Beyond peaceful coexistence the emergence of space, time and quantum
2016-01-01
Beyond Peaceful Coexistence: The Emergence of Space, Time and Quantum brings together leading academics in mathematics and physics to address going beyond the 'peaceful coexistence' of space-time descriptions (local and continuous ones) and quantum events (discrete and non-commutative ones). Formidable challenges waiting beyond the Standard Model require a new semantic consistency within the theories in order to build new ways of understanding, working and relating to them. The original A. Shimony meaning of the peaceful coexistence (the collapse postulate and non-locality) appear to be just the tip of the iceberg in relation to more serious fundamental issues across physics as a whole.Chapters in this book present perspectives on emergent, discrete, geometrodynamic and topological approaches, as well as a new interpretative spectrum of quantum theories after Copenhagen, discrete time theories, time-less approaches and 'super-fluid' pictures of space-time.As well as stimulating further research among establis...
FLRW cosmology in Weyl-integrable space-time
Energy Technology Data Exchange (ETDEWEB)
Gannouji, Radouane [Department of Physics, Faculty of Science, Tokyo University of Science, 1–3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan); Nandan, Hemwati [Department of Physics, Gurukula Kangri Vishwavidayalaya, Haridwar 249404 (India); Dadhich, Naresh, E-mail: gannouji@rs.kagu.tus.ac.jp, E-mail: hntheory@yahoo.co.in, E-mail: nkd@iucaa.ernet.in [IUCAA, Post Bag 4, Ganeshkhind, Pune 411 007 (India)
2011-11-01
We investigate the Weyl space-time extension of general relativity (GR) for studying the FLRW cosmology through focusing and defocusing of the geodesic congruences. We have derived the equations of evolution for expansion, shear and rotation in the Weyl space-time. In particular, we consider the Starobinsky modification, f(R) = R+βR{sup 2}−2Λ, of gravity in the Einstein-Palatini formalism, which turns out to reduce to the Weyl integrable space-time (WIST) with the Weyl vector being a gradient. The modified Raychaudhuri equation takes the form of the Hill-type equation which is then analysed to study the formation of the caustics. In this model, it is possible to have a Big Bang singularity free cyclic Universe but unfortunately the periodicity turns out to be extremely short.
A geometric renormalization group in discrete quantum space-time
International Nuclear Information System (INIS)
Requardt, Manfred
2003-01-01
We model quantum space-time on the Planck scale as dynamical networks of elementary relations or time dependent random graphs, the time dependence being an effect of the underlying dynamical network laws. We formulate a kind of geometric renormalization group on these (random) networks leading to a hierarchy of increasingly coarse-grained networks of overlapping lumps. We provide arguments that this process may generate a fixed limit phase, representing our continuous space-time on a mesoscopic or macroscopic scale, provided that the underlying discrete geometry is critical in a specific sense (geometric long range order). Our point of view is corroborated by a series of analytic and numerical results, which allow us to keep track of the geometric changes, taking place on the various scales of the resolution of space-time. Of particular conceptual importance are the notions of dimension of such random systems on the various scales and the notion of geometric criticality
MEST- avoid next extinction by a space-time effect
Cao, Dayong
2013-03-01
Sun's companion-dark hole seasonal took its dark comets belt and much dark matter to impact near our earth. And some of them probability hit on our earth. So this model kept and triggered periodic mass extinctions on our earth every 25 to 27 million years. After every impaction, many dark comets with very special tilted orbits were arrested and lurked in solar system. When the dark hole-Tyche goes near the solar system again, they will impact near planets. The Tyche, dark comet and Oort Cloud have their space-time center. Because the space-time are frequency and amplitude square of wave. Because the wave (space-time) can make a field, and gas has more wave and fluctuate. So they like dense gas ball and a dark dense field. They can absorb the space-time and wave. So they are ``dark'' like the dark matter which can break genetic codes of our lives by a dark space-time effect. So the upcoming next impaction will cause current ``biodiversity loss.'' The dark matter can change dead plants and animals to coal, oil and natural gas which are used as energy, but break our living environment. According to our experiments, which consciousness can use thought waves remotely to change their systemic model between Electron Clouds and electron holes of P-N Junction and can change output voltages of solar cells by a life information technology and a space-time effect, we hope to find a new method to the orbit of the Tyche to avoid next extinction. (see Dayong Cao, BAPS.2011.APR.K1.17 and BAPS.2012.MAR.P33.14) Support by AEEA
Space-Time Diffeomorphisms in Noncommutative Gauge Theories
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L. Román Juarez
2008-07-01
Full Text Available In previous work [Rosenbaum M. et al., J. Phys. A: Math. Theor. 40 (2007, 10367–10382] we have shown how for canonical parametrized field theories, where space-time is placed on the same footing as the other fields in the theory, the representation of space-time diffeomorphisms provides a very convenient scheme for analyzing the induced twisted deformation of these diffeomorphisms, as a result of the space-time noncommutativity. However, for gauge field theories (and of course also for canonical geometrodynamics where the Poisson brackets of the constraints explicitely depend on the embedding variables, this Poisson algebra cannot be connected directly with a representation of the complete Lie algebra of space-time diffeomorphisms, because not all the field variables turn out to have a dynamical character [Isham C.J., Kuchar K.V., Ann. Physics 164 (1985, 288–315, 316–333]. Nonetheless, such an homomorphic mapping can be recuperated by first modifying the original action and then adding additional constraints in the formalism in order to retrieve the original theory, as shown by Kuchar and Stone for the case of the parametrized Maxwell field in [Kuchar K.V., Stone S.L., Classical Quantum Gravity 4 (1987, 319–328]. Making use of a combination of all of these ideas, we are therefore able to apply our canonical reparametrization approach in order to derive the deformed Lie algebra of the noncommutative space-time diffeomorphisms as well as to consider how gauge transformations act on the twisted algebras of gauge and particle fields. Thus, hopefully, adding clarification on some outstanding issues in the literature concerning the symmetries for gauge theories in noncommutative space-times.
Joint Estimation and Decoding of Space-Time Trellis Codes
Directory of Open Access Journals (Sweden)
Zhang Jianqiu
2002-01-01
Full Text Available We explore the possibility of using an emerging tool in statistical signal processing, sequential importance sampling (SIS, for joint estimation and decoding of space-time trellis codes (STTC. First, we provide background on SIS, and then we discuss its application to space-time trellis code (STTC systems. It is shown through simulations that SIS is suitable for joint estimation and decoding of STTC with time-varying flat-fading channels when phase ambiguity is avoided. We used a design criterion for STTCs and temporally correlated channels that combats phase ambiguity without pilot signaling. We have shown by simulations that the design is valid.
Topology and isometries of the de Sitter space-time
International Nuclear Information System (INIS)
Mitskevich, N.V.; Senin, Yu.E.
1982-01-01
Spaces with a constant four-dimensional curvature, which are locally isometric to the de Sitter space-time but differing from it in topology are considered. The de Sitter spaces are considered in coordinates fitted at best for introduction of topology for three cross sections: S 3 , S 1 x S 2 , S 1 x S 2 x S 3 . It is shown that the de Sitter space-time covered by the family of layers, each of them is topologically identical, may be covered by another family of topologically identical layers. But layers in these families will have different topology
Holographic analysis of dispersive pupils in space--time optics
International Nuclear Information System (INIS)
Calatroni, J.; Vienot, J.C.
1981-01-01
Extension of space--time optics to objects whose transparency is a function of the temporal frequency v = c/lambda is examined. Considering the effects of such stationary pupils on white light waves, they are called temporal pupils. It is shown that simultaneous encoding both in the space and time frequency domains is required to record pupil parameters. The space-time impulse response and transfer functions are calculated for a dispersive nonabsorbent material. An experimental method providing holographic recording of the dispersion curve of any transparent material is presented
The scalar wave equation in a Schwarzschild space-time
International Nuclear Information System (INIS)
Schmidt, B.G.; Stewart, J.M.
1979-01-01
This paper studies the asymptotic behaviour of solutions of the zero rest mass scalar wave equation in the Schwarzschild space-time in a neighbourhood of spatial infinity which includes parts of future and pass null infinity. The behaviour of such fields is essentially different from that which occurs in a flat space-time. In particular fields which have a Bondi-type expansion in powers of 'r(-1)' near past null infinity do not have such an expansion near future null infinity. Further solutions which have physically reasonable Cauchy data probably fail to have Bondi-type expansions near null infinity. (author)
On signature change in p-adic space-times
International Nuclear Information System (INIS)
Dragovic, B.G.
1991-01-01
Change of signature by linear coordinate transformations in p-adic space-times is considered. In this paper it is shown that there exists arbitrary change of trivial signature in Q p n for all n ≥ 1 if p ≡ 1 (mod 4). In other cases it is possible to change only even number of the signs of the signature. The authors suggest new concept of signature with respect to distinct quadratic extensions, of Q p . If space-time dimension is restricted to four there is no signature change
On quantization of free fields in stationary space-times
International Nuclear Information System (INIS)
Moreno, C.
1977-01-01
In Section 1 the structure of the infinite-dimensional Hamiltonian system described by the Klein-Gordon equation (free real scalar field) in stationary space-times with closed space sections, is analysed, an existence and uniqueness theorem is given for the Lichnerowicz distribution kernel G 1 together with its proper Fourier expansion, and the Hilbert spaces of frequency-part solutions defined by means of G 1 are constructed. In Section 2 an analysis, a theorem and a construction similar to the above are formulated for the free real field spin 1, mass m>0, in one kind of static space-times. (Auth.)
On maximal surfaces in asymptotically flat space-times
International Nuclear Information System (INIS)
Bartnik, R.; Chrusciel, P.T.; O Murchadha, N.
1990-01-01
Existence of maximal and 'almost maximal' hypersurfaces in asymptotically flat space-times is established under boundary conditions weaker than those considered previously. We show in particular that every vacuum evolution of asymptotically flat data for Einstein equations can be foliated by slices maximal outside a spatially compact set and that every (strictly) stationary asymptotically flat space-time can be foliated by maximal hypersurfaces. Amongst other uniqueness results, we show that maximal hypersurface can be used to 'partially fix' an asymptotic Poincare group. (orig.)
Holographic analysis of dispersive pupils in space--time optics
Energy Technology Data Exchange (ETDEWEB)
Calatroni, J.; Vienot, J.C.
1981-06-01
Extension of space--time optics to objects whose transparency is a function of the temporal frequency v = c/lambda is examined. Considering the effects of such stationary pupils on white light waves, they are called temporal pupils. It is shown that simultaneous encoding both in the space and time frequency domains is required to record pupil parameters. The space-time impulse response and transfer functions are calculated for a dispersive nonabsorbent material. An experimental method providing holographic recording of the dispersion curve of any transparent material is presented.
Gauge fields in algebraically special space-times
International Nuclear Information System (INIS)
Torres del Castillo, G.F.
1985-01-01
It is shown that in an algebraically special space-time which admits a congruence of null strings, a source-free gauge field aligned with the congruence is determined by a matrix potential which has to satisfy a second-order differential equation with quadratic nonlinearities. The Einstein--Yang--Mills equations are then reduced to a scalar and two matrix equations. In the case of self-dual gauge fields in a self-dual space-time, the existence of an infinite set of conservation laws, of an associated linear system, and of infinitesimal Baecklund transformations is demonstrated. All the results apply for an arbitrary gauge group
Two theorems on flat space-time gravitational theories
International Nuclear Information System (INIS)
Castagnino, M.; Chimento, L.
1980-01-01
The first theorem states that all flat space-time gravitational theories must have a Lagrangian with a first term that is an homogeneous (degree-1) function of the 4-velocity usup(i), plus a functional of nsub(ij)usup(i)usup(j). The second theorem states that all gravitational theories that satisfy the strong equivalence principle have a Lagrangian with a first term gsub(ij)(x)usup(i)usup(j) plus an irrelevant term. In both cases the theories must issue from a unique variational principle. Therefore, under this condition it is impossible to find a flat space-time theory that satisfies the strong equivalence principle. (author)
Null geodesic deviation II. Conformally flat space--times
International Nuclear Information System (INIS)
Peters, P.C.
1975-01-01
The equation of geodesic deviation is solved in conformally flat space--time in a covariant manner. The solution is given as an integral equation for general geodesics. The solution is then used to evaluate second derivatives of the world function and derivatives of the parallel propagator, which need to be known in order to find the Green's function for wave equations in curved space--time. A method of null geodesic limits of two-point functions is discussed, and used to find the scalar Green's function as an iterative series
Flat synchronizations in spherically symmetric space-times
International Nuclear Information System (INIS)
Herrero, Alicia; Morales-Lladosa, Juan Antonio
2010-01-01
It is well known that the Schwarzschild space-time admits a spacelike slicing by flat instants and that the metric is regular at the horizon in the associated adapted coordinates (Painleve-Gullstrand metric form). We consider this type of flat slicings in an arbitrary spherically symmetric space-time. The condition ensuring its existence is analyzed, and then, we prove that, for any spherically symmetric flat slicing, the densities of the Weinberg momenta vanish. Finally, we deduce the Schwarzschild solution in the extended Painleve-Gullstrand-LemaItre metric form by considering the coordinate decomposition of the vacuum Einstein equations with respect to a flat spacelike slicing.
A higher order space-time Galerkin scheme for time domain integral equations
Pray, Andrew J.
2014-12-01
Stability of time domain integral equation (TDIE) solvers has remained an elusive goal formany years. Advancement of this research has largely progressed on four fronts: 1) Exact integration, 2) Lubich quadrature, 3) smooth temporal basis functions, and 4) space-time separation of convolutions with the retarded potential. The latter method\\'s efficacy in stabilizing solutions to the time domain electric field integral equation (TD-EFIE) was previously reported for first-order surface descriptions (flat elements) and zeroth-order functions as the temporal basis. In this work, we develop the methodology necessary to extend the scheme to higher order surface descriptions as well as to enable its use with higher order basis functions in both space and time. These basis functions are then used in a space-time Galerkin framework. A number of results are presented that demonstrate convergence in time. The viability of the space-time separation method in producing stable results is demonstrated experimentally for these examples.
Spinor Field Nonlinearity and Space-Time Geometry
Saha, Bijan
2018-03-01
Within the scope of Bianchi type VI,VI0,V, III, I, LRSBI and FRW cosmological models we have studied the role of nonlinear spinor field on the evolution of the Universe and the spinor field itself. It was found that due to the presence of non-trivial non-diagonal components of the energy-momentum tensor of the spinor field in the anisotropic space-time, there occur some severe restrictions both on the metric functions and on the components of the spinor field. In this report we have considered a polynomial nonlinearity which is a function of invariants constructed from the bilinear spinor forms. It is found that in case of a Bianchi type-VI space-time, depending of the sign of self-coupling constants, the model allows either late time acceleration or oscillatory mode of evolution. In case of a Bianchi VI 0 type space-time due to the specific behavior of the spinor field we have two different scenarios. In one case the invariants constructed from bilinear spinor forms become trivial, thus giving rise to a massless and linear spinor field Lagrangian. This case is equivalent to the vacuum solution of the Bianchi VI 0 type space-time. The second case allows non-vanishing massive and nonlinear terms and depending on the sign of coupling constants gives rise to accelerating mode of expansion or the one that after obtaining some maximum value contracts and ends in big crunch, consequently generating space-time singularity. In case of a Bianchi type-V model there occur two possibilities. In one case we found that the metric functions are similar to each other. In this case the Universe expands with acceleration if the self-coupling constant is taken to be a positive one, whereas a negative coupling constant gives rise to a cyclic or periodic solution. In the second case the spinor mass and the spinor field nonlinearity vanish and the Universe expands linearly in time. In case of a Bianchi type-III model the space-time remains locally rotationally symmetric all the time
PURE STATE ENTANGLEMENT ENTROPY IN NONCOMMUTATIVE 2D DE SITTER SPACE TIME
Directory of Open Access Journals (Sweden)
M.F Ghiti
2014-12-01
Full Text Available Using the general modified field equation, a general noncommutative Klein-Gordon equation up to the second order of the noncommutativity parameter is derived in the context of noncommutative 2D De Sitter space-time. Using Bogoliubov coefficients and a special technics called conformal time; the boson-antiboson pair creation density is determined. The Von Neumann boson-antiboson pair creation quantum entanglement entropy is presented to compute the entanglement between the modes created presented.
Casimir force in the Goedel space-time and its possible induced cosmological inhomogeneity
Energy Technology Data Exchange (ETDEWEB)
Khodabakhshi, Sh. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Shojai, A. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), Foundations of Physics Group, School of Physics, Tehran (Iran, Islamic Republic of)
2017-07-15
The Casimir force between two parallel plates in the Goedel universe is computed for a scalar field at finite temperature. It is observed that when the plates' separation is comparable with the scale given by the rotation of the space-time, the force becomes repulsive and then approaches zero. Since it has been shown previously that the universe may experience a Goedel phase for a small period of time, the induced inhomogeneities from the Casimir force are also studied. (orig.)
Operational definition of (brane-induced) space-time and constraints on the fundamental parameters
International Nuclear Information System (INIS)
Maziashvili, Michael
2008-01-01
First we contemplate the operational definition of space-time in four dimensions in light of basic principles of quantum mechanics and general relativity and consider some of its phenomenological consequences. The quantum gravitational fluctuations of the background metric that comes through the operational definition of space-time are controlled by the Planck scale and are therefore strongly suppressed. Then we extend our analysis to the braneworld setup with low fundamental scale of gravity. It is observed that in this case the quantum gravitational fluctuations on the brane may become unacceptably large. The magnification of fluctuations is not linked directly to the low quantum gravity scale but rather to the higher-dimensional modification of Newton's inverse square law at relatively large distances. For models with compact extra dimensions the shape modulus of extra space can be used as a most natural and safe stabilization mechanism against these fluctuations
Computer program for storage and retrieval of thermal-stability data for explosives
International Nuclear Information System (INIS)
Ashcraft, R.W.
1981-06-01
A computer program for storage and retrieval of thermal stability data has been written in HP Basic for the HP-9845 system. The data library is stored on a 9885 flexible disk. A program listing and sample outputs are included as appendices
Three computer codes for safety and stability of large superconducting magnets
International Nuclear Information System (INIS)
Turner, L.R.
1985-01-01
For analyzing the safety and stability of large superconducting magnets, three computer codes TASS, SHORTURN, and SSICC have been developed, applicable to bath-cooled magnets, bath-cooled magnets with shorted turns, and magnets with internally cooled conductors respectively. The TASS code is described, and the use of the three codes is reviewed
Stability and Bifurcation Analysis of a Modified Epidemic Model for Computer Viruses
Directory of Open Access Journals (Sweden)
Chuandong Li
2014-01-01
Full Text Available We extend the three-dimensional SIR model to four-dimensional case and then analyze its dynamical behavior including stability and bifurcation. It is shown that the new model makes a significant improvement to the epidemic model for computer viruses, which is more reasonable than the most existing SIR models. Furthermore, we investigate the stability of the possible equilibrium point and the existence of the Hopf bifurcation with respect to the delay. By analyzing the associated characteristic equation, it is found that Hopf bifurcation occurs when the delay passes through a sequence of critical values. An analytical condition for determining the direction, stability, and other properties of bifurcating periodic solutions is obtained by using the normal form theory and center manifold argument. The obtained results may provide a theoretical foundation to understand the spread of computer viruses and then to minimize virus risks.
On the performance of diagonal lattice space-time codes
Abediseid, Walid; Alouini, Mohamed-Slim
2013-01-01
There has been tremendous work done on designing space-time codes for the quasi-static multiple-input multiple output (MIMO) channel. All the coding design up-to-date focuses on either high-performance, high rates, low complexity encoding
Strings reinterpreted as topological elements of space time
International Nuclear Information System (INIS)
Ne'eman, Y.
1986-01-01
In 1974, Scherk and Schwarz suggested a reinterpretation of string dynamics as a theory of quantum gravity with unification. We suggest completing the transition through the reinterpretation of the strings themselves as Feynman-paths, spanning the topology of space time in the Hawking-King-McCarthy model. This explains the emergency of gravity
Projected space-time and varying speed of light
International Nuclear Information System (INIS)
Iovane, G.; Bellucci, S.; Benedetto, E.
2008-01-01
In this paper starting from El Naschie's Cantorian space-time and our model of projected Universe, we consider its properties in connection with varying speed of light. A possible way-out of the related problem is provided by the Fantappie group approach
Unsupervised action classification using space-time link analysis
DEFF Research Database (Denmark)
Liu, Haowei; Feris, Rogerio; Krüger, Volker
2010-01-01
In this paper we address the problem of unsupervised discovery of action classes in video data. Different from all existing methods thus far proposed for this task, we present a space-time link analysis approach which matches the performance of traditional unsupervised action categorization metho...
Space-time structure and the origin of physical law
International Nuclear Information System (INIS)
Green, M.A.
1980-01-01
In the first part of this theses the author adopts a traditional world view, with space-time a topologically simple geometrical manifold, matter being represented by smooth classical fields, and space a Riemannian submanifold of space-time. It is shown how to characterize the space-time geometry in terms of fields defined on three-dimensional space. Accepting a finite number of the fields induced on space as independent initial data, a procedure is given for constructing dynamical and constraint equations which will propagate these fields forward in time. When the initial data are restricted to include only the hypersurface metric and the extrinsic curvature, the resulting equations combine to form the Einstein gravitational field equations with the cosmological term. The synthesis of gravitational and quantum physics is approached by proposing that the objective world underlying the perceived world is a four-dimensional topological manifold w, with no physically significant field structure and an unconstrianed and complex global topology. Conventional space-time is then a topologically simple replacement manifold for w. A preliminary outline of the correspondence is presented, based on a similarity between a natural graphical representation of 2 and the Feynman graphs of quantum field theory
Space-time design of the public city
Thomaier, Susanne; Könecke, Benjamin; Zedda, Roberto; Stabilini, Stefano
2013-01-01
Time has become an increasingly important topic in urban studies and urban planning. The spatial-temporal interplay is not only of relevance for the theory of urban development and urban politics, but also for urban planning and governance. The space-time approach focuses on the human being with its various habits and routines in the city. Understanding and taking those habits into account in urban planning and public policies offers a new way to improve the quality of life in our cities. Adapting the supply and accessibility of public spaces and services to the inhabitants’ space-time needs calls for an integrated approach to the physical design of urban space and to the organization of cities. In the last two decades the body of practical and theoretical work on urban space-time topics has grown substantially. The book offers a state of the art overview of the theoretical reasoning, the development of new analytical tools, and practical experience of the space-time design of public cities in major Europea...
Poisson's equation in de Sitter space-time
Energy Technology Data Exchange (ETDEWEB)
Pessa, E [Rome Univ. (Italy). Ist. di Matematica
1980-11-01
Based on a suitable generalization of Poisson's equation for de Sitter space-time the form of gravitation's law in 'projective relativity' is examined; it is found that, in the interior case, a small difference with the customary Newtonian law arises. This difference, of a repulsive character, can be very important in cosmological problems.
Space-time transformations in radial path integrals
International Nuclear Information System (INIS)
Steiner, F.
1984-09-01
Nonlinear space-time transformations in the radial path integral are discussed. A transformation formula is derived, which relates the original path integral to the Green's function of a new quantum system with an effective potential containing an observable quantum correction proportional(h/2π) 2 . As an example the formula is applied to spherical Brownian motion. (orig.)
Scalar metric fluctuations in space-time matter inflation
International Nuclear Information System (INIS)
Anabitarte, Mariano; Bellini, Mauricio
2006-01-01
Using the Ponce de Leon background metric, which describes a 5D universe in an apparent vacuum: G-bar AB =0, we study the effective 4D evolution of both, the inflaton and gauge-invariant scalar metric fluctuations, in the recently introduced model of space-time matter inflation
The order axiom and the biological space time
International Nuclear Information System (INIS)
Vu Huu Nhu
2014-01-01
This work focuses on the field of Biological Space - Time. In fact the conception of Biological Space - Time is connected with order character of sets. Because the illustration of order axioms is very important for searching order systems. In this work, the new form of order axioms has been illustrated in the form of (a,b) ≠ (b.a). It is a common form of Descartes product. Based on this we suggest the following formation of order lemma (a.b) ≠(b.a)↔ a Φ b. In this case Φ is an order relation. From the new form of order axiom, we determine the order system as follows: If S = (a,b) the set of two elements and the order axiom (a.b) ≠ (b.a) is satisfied. So that, in this case, S is called an order system. The life system are the most important order systems. We could illustrate the biological system as: S = (A, T, G, C). In this set, A, T, G, C are the elements of the genetic code and the order axiom is satisfied. As we know, for example, in genetic code: (AUG) ≠ (UGA) ≠ (UAG). The order biological system induces an order relation and it is the origin of the conception of Biological Space Time. The students of Physics and Biology could use this book as basic course for studies of Biological Space Time. (author)
Zen and the Art of Space-Time Manufacturing
Directory of Open Access Journals (Sweden)
Bertolami Orfeu
2013-09-01
Full Text Available We present a general discussion about the so-called emergent properties and discuss whether space-time and gravity can be regarded as emergent features of underlying more fundamental structures. Finally, we discuss some ideas about the multiverse, and speculate on how our universe might arise from the multiverse.
The wave equation on a curved space-time
International Nuclear Information System (INIS)
Friedlander, F.G.
1975-01-01
It is stated that chapters on differential geometry, distribution theory, and characteristics and the propagation of discontinuities are preparatory. The main matter is in three chapters, entitled: fundamental solutions, representation theorems, and wave equations on n-dimensional space-times. These deal with general construction of fundamental solutions and their application to the Cauchy problem. (U.K.)
Notes on a class of homogeneous space-times
International Nuclear Information System (INIS)
Calvao, M.O.; Reboucas, M.J.; Teixeira, A.F.F.; Silva Junior, W.M.
1987-01-01
The breakdown of causality in homogeneous Goedel-type space-time manifolds is examined. An extension of Reboucas-Tiomno (RT) study is made. The existence of noncausal curves is also investigated under two different conditions on the energy-momentum tensor. An integral representation of the infinitesimal generators of isometries is obtained extending previous works on the RT geometry. (Author) [pt
International Nuclear Information System (INIS)
Dey, Dipanjan
2015-01-01
Dark-matter is a hypothetical matter which can't be seen but around 27% of our universe is made of it. Its distribution, evolution from early stage of our universe to present stage, its particle constituents all these are great unsolved mysteries of modern Cosmology and Astrophysics. In this talk I will introduce a special kind of space-time which is known as Bertrand Space-time (BST). I will show this space-time interestingly shows some dark-matter properties like- flat velocity curve, density profile of Dark-matter, total mass of Dark matter-halo, gravitational lensing etc, for that reason we consider BST is seeded by Dark-matter or it is a space-time of Dark-matter. At last I will show using modified gravity formalism the behaviour of the equation of state parameter of Dark-matter and the behaviour of the Newton's gravitational constant in the vicinity of the singularity. (author)
Space-times carrying a quasirecurrent pairing of vector fields
International Nuclear Information System (INIS)
Rosca, R.; Ianus, S.
1977-01-01
A quasirecurrent pairing of vector fields(X 1 ,X 2 ,) defined previously by Rosca (C.R. Acad. Sci. 282 (1976)) is investigated on a space-time in two cases: (1) X 1 is spacelike and X 2 is timelike; (2) X 1 is null and X 2 is spacelike. The physical interpretation of these vector fields is given. (author)
Computational stability of the Von Neumann--Richtmyer method for the case of the ideal gas law
International Nuclear Information System (INIS)
Hicks, D.L.
1978-07-01
Two stability concepts are of interest for partial difference equations--one arises in theory--the other in practice. The theoretical kind, referred to here as asymptotic stability, is essentially just asymptotic (as Δt, Δx → 0) boundedness of the discrete solution. The other kind, referred to here as computational stability, is stability for a fixed Δt and Δx--computational instability is indicated in practice by oscillatory behavior of the discrete approximation--in particular, oscillations of period 2Δx. This report is concerned with computational stability. Only approximate stability analyses of the von Neumann-Richtmyer scheme have been done for the case of the ideal gas law. Herein a more rigorous computational stability analysis is sought. The analysis leads to a recommendation for the improvement of the time step restriction in WONDY for the case of the ideal gas law
Bennett, R. M.; Bland, S. R.; Redd, L. T.
1973-01-01
Computer programs for calculating the stability characteristics of a balloon tethered in a steady wind are presented. Equilibrium conditions, characteristic roots, and modal ratios are calculated for a range of discrete values of velocity for a fixed tether-line length. Separate programs are used: (1) to calculate longitudinal stability characteristics, (2) to calculate lateral stability characteristics, (3) to plot the characteristic roots versus velocity, (4) to plot the characteristic roots in root-locus form, (5) to plot the longitudinal modes of motion, and (6) to plot the lateral modes for motion. The basic equations, program listings, and the input and output data for sample cases are presented, with a brief discussion of the overall operation and limitations. The programs are based on a linearized, stability-derivative type of analysis, including balloon aerodynamics, apparent mass, buoyancy effects, and static forces which result from the tether line.
Leus, G.; Petré, F.; Moonen, M.
2004-01-01
In the downlink of DS-CDMA, frequency-selectivity destroys the orthogonality of the user signals and introduces multiuser interference (MUI). Space-time chip equalization is an efficient tool to restore the orthogonality of the user signals and suppress the MUI. Furthermore, multiple-input
Trajectory data analyses for pedestrian space-time activity study.
Qi, Feng; Du, Fei
2013-02-25
It is well recognized that human movement in the spatial and temporal dimensions has direct influence on disease transmission(1-3). An infectious disease typically spreads via contact between infected and susceptible individuals in their overlapped activity spaces. Therefore, daily mobility-activity information can be used as an indicator to measure exposures to risk factors of infection. However, a major difficulty and thus the reason for paucity of studies of infectious disease transmission at the micro scale arise from the lack of detailed individual mobility data. Previously in transportation and tourism research detailed space-time activity data often relied on the time-space diary technique, which requires subjects to actively record their activities in time and space. This is highly demanding for the participants and collaboration from the participants greatly affects the quality of data(4). Modern technologies such as GPS and mobile communications have made possible the automatic collection of trajectory data. The data collected, however, is not ideal for modeling human space-time activities, limited by the accuracies of existing devices. There is also no readily available tool for efficient processing of the data for human behavior study. We present here a suite of methods and an integrated ArcGIS desktop-based visual interface for the pre-processing and spatiotemporal analyses of trajectory data. We provide examples of how such processing may be used to model human space-time activities, especially with error-rich pedestrian trajectory data, that could be useful in public health studies such as infectious disease transmission modeling. The procedure presented includes pre-processing, trajectory segmentation, activity space characterization, density estimation and visualization, and a few other exploratory analysis methods. Pre-processing is the cleaning of noisy raw trajectory data. We introduce an interactive visual pre-processing interface as well as an
Directory of Open Access Journals (Sweden)
C.G. Ozoegwu
2016-01-01
Full Text Available The general least squares model for milling process state term is presented. A discrete map for milling stability analysis that is based on the third-order case of the presented general least squares milling state term model is first studied and compared with its third-order counterpart that is based on the interpolation theory. Both numerical rate of convergence and chatter stability results of the two maps are compared using the single degree of freedom (1DOF milling model. The numerical rate of convergence of the presented third-order model is also studied using the two degree of freedom (2DOF milling process model. Comparison gave that stability results from the two maps agree closely but the presented map demonstrated reduction in number of needed calculations leading to about 30% savings in computational time (CT. It is seen in earlier works that accuracy of milling stability analysis using the full-discretization method rises from first-order theory to second-order theory and continues to rise to the third-order theory. The present work confirms this trend. In conclusion, the method presented in this work will enable fast and accurate computation of stability diagrams for use by machinists.
A space-time lower-upper symmetric Gauss-Seidel scheme for the time-spectral method
Zhan, Lei; Xiong, Juntao; Liu, Feng
2016-05-01
The time-spectral method (TSM) offers the advantage of increased order of accuracy compared to methods using finite-difference in time for periodic unsteady flow problems. Explicit Runge-Kutta pseudo-time marching and implicit schemes have been developed to solve iteratively the space-time coupled nonlinear equations resulting from TSM. Convergence of the explicit schemes is slow because of the stringent time-step limit. Many implicit methods have been developed for TSM. Their computational efficiency is, however, still limited in practice because of delayed implicit temporal coupling, multiple iterative loops, costly matrix operations, or lack of strong diagonal dominance of the implicit operator matrix. To overcome these shortcomings, an efficient space-time lower-upper symmetric Gauss-Seidel (ST-LU-SGS) implicit scheme with multigrid acceleration is presented. In this scheme, the implicit temporal coupling term is split as one additional dimension of space in the LU-SGS sweeps. To improve numerical stability for periodic flows with high frequency, a modification to the ST-LU-SGS scheme is proposed. Numerical results show that fast convergence is achieved using large or even infinite Courant-Friedrichs-Lewy (CFL) numbers for unsteady flow problems with moderately high frequency and with the use of moderately high numbers of time intervals. The ST-LU-SGS implicit scheme is also found to work well in calculating periodic flow problems where the frequency is not known a priori and needed to be determined by using a combined Fourier analysis and gradient-based search algorithm.
Analysis of Characteristics of Lateral Stability of Sailplane Lak 17a by Computational Method
Directory of Open Access Journals (Sweden)
Paulius Gildutis
2011-04-01
Full Text Available A computer-based geometrical model of the Lak-17a sailplane was generated with the program AVL (Athena Vortex Lattice, which is designed to analyse the characteristics of flight and to provide a rapid analysis of the configuration of an aircraft. Various characteristics of stability and control were calculated by simulating a real flight with the program. According to the results, a conclusion was formulated and suggestions about how to improve the stability and control of the aircraft were offered. Article in Lithuanian
Stabilization of emission of CO2: A computable general equilibrium assessment
International Nuclear Information System (INIS)
Glomsroed, S.; Vennemo, H.; Johnsen, T.
1992-01-01
A multisector computable general equilibrium model is used to study economic development perspectives in Norway if CO 2 emissions were stabilized. The effects discussed include impacts on main macroeconomic indicators and economic growth, sectoral allocation of production, and effects on the market for energy. The impact of other pollutants than CO 2 on emissions is assessed along with the related impact on noneconomic welfare. The results indicate that CO 2 emissions might be stabilized in Norway without dramatically reducing economic growth. Sectoral allocation effects are much larger. A substantial reduction in emissions to air other than CO 2 is found, yielding considerable gains in noneconomic welfare. 25 refs., 6 tabs., 2 figs
Hamiltonian Dynamics of Doubly-Foliable Space-Times
Directory of Open Access Journals (Sweden)
Cecília Gergely
2018-01-01
Full Text Available The 2 + 1 + 1 decomposition of space-time is useful in monitoring the temporal evolution of gravitational perturbations/waves in space-times with a spatial direction singled-out by symmetries. Such an approach based on a perpendicular double foliation has been employed in the framework of dark matter and dark energy-motivated scalar-tensor gravitational theories for the discussion of the odd sector perturbations of spherically-symmetric gravity. For the even sector, however, the perpendicularity has to be suppressed in order to allow for suitable gauge freedom, recovering the 10th metric variable. The 2 + 1 + 1 decomposition of the Einstein–Hilbert action leads to the identification of the canonical pairs, the Hamiltonian and momentum constraints. Hamiltonian dynamics is then derived via Poisson brackets.
Space-time modeling of electricity spot prices
DEFF Research Database (Denmark)
Abate, Girum Dagnachew; Haldrup, Niels
In this paper we derive a space-time model for electricity spot prices. A general spatial Durbin model that incorporates the temporal as well as spatial lags of spot prices is presented. Joint modeling of space-time effects is necessarily important when prices and loads are determined in a network...... in the spot price dynamics. Estimation of the spatial Durbin model show that the spatial lag variable is as important as the temporal lag variable in describing the spot price dynamics. We use the partial derivatives impact approach to decompose the price impacts into direct and indirect effects and we show...... that price effects transmit to neighboring markets and decline with distance. In order to examine the evolution of the spatial correlation over time, a time varying parameters spot price spatial Durbin model is estimated using recursive estimation. It is found that the spatial correlation within the Nord...
The Verriest Lecture: Color lessons from space, time, and motion
Shevell, Steven K.
2012-01-01
The appearance of a chromatic stimulus depends on more than the wavelengths composing it. The scientific literature has countless examples showing that spatial and temporal features of light influence the colors we see. Studying chromatic stimuli that vary over space, time or direction of motion has a further benefit beyond predicting color appearance: the unveiling of otherwise concealed neural processes of color vision. Spatial or temporal stimulus variation uncovers multiple mechanisms of brightness and color perception at distinct levels of the visual pathway. Spatial variation in chromaticity and luminance can change perceived three-dimensional shape, an example of chromatic signals that affect a percept other than color. Chromatic objects in motion expose the surprisingly weak link between the chromaticity of objects and their physical direction of motion, and the role of color in inducing an illusory motion direction. Space, time and motion – color’s colleagues – reveal the richness of chromatic neural processing. PMID:22330398
Convexity and the Euclidean Metric of Space-Time
Directory of Open Access Journals (Sweden)
Nikolaos Kalogeropoulos
2017-02-01
Full Text Available We address the reasons why the “Wick-rotated”, positive-definite, space-time metric obeys the Pythagorean theorem. An answer is proposed based on the convexity and smoothness properties of the functional spaces purporting to provide the kinematic framework of approaches to quantum gravity. We employ moduli of convexity and smoothness which are eventually extremized by Hilbert spaces. We point out the potential physical significance that functional analytical dualities play in this framework. Following the spirit of the variational principles employed in classical and quantum Physics, such Hilbert spaces dominate in a generalized functional integral approach. The metric of space-time is induced by the inner product of such Hilbert spaces.
Spinors, superalgebras and the signature of space-time
Ferrara, S.
2001-01-01
Superconformal algebras embedding space-time in any dimension and signature are considered. Different real forms of the $R$-symmetries arise both for usual space-time signature (one time) and for Euclidean or exotic signatures (more than one times). Application of these superalgebras are found in the context of supergravities with 32 supersymmetries, in any dimension $D \\leq 11$. These theories are related to $D = 11, M, M^*$ and $M^\\prime$ theories or $D = 10$, IIB, IIB$^*$ theories when compactified on Lorentzian tori. All dimensionally reduced theories fall in three distinct phases specified by the number of (128 bosonic) positive and negative norm states: $(n^+,n^-) = (128,0), (64,64), (72,56)$.
Pre-Big Bang, space-time structure, asymptotic Universe
Directory of Open Access Journals (Sweden)
Gonzalez-Mestres Luis
2014-04-01
Full Text Available Planck and other recent data in Cosmology and Particle Physics can open the way to controversial analyses concerning the early Universe and its possible ultimate origin. Alternatives to standard cosmology include pre-Big Bang approaches, new space-time geometries and new ultimate constituents of matter. Basic issues related to a possible new cosmology along these lines clearly deserve further exploration. The Planck collaboration reports an age of the Universe t close to 13.8 Gyr and a present ratio H between relative speeds and distances at cosmic scale around 67.3 km/s/Mpc. The product of these two measured quantities is then slightly below 1 (about 0.95, while it can be exactly 1 in the absence of matter and cosmological constant in patterns based on the spinorial space-time we have considered in previous papers. In this description of space-time we first suggested in 1996-97, the cosmic time t is given by the modulus of a SU(2 spinor and the Lundmark-Lemaître-Hubble (LLH expansion law turns out to be of purely geometric origin previous to any introduction of standard matter and relativity. Such a fundamental geometry, inspired by the role of half-integer spin in Particle Physics, may reflect an equilibrium between the dynamics of the ultimate constituents of matter and the deep structure of space and time. Taking into account the observed cosmic acceleration, the present situation suggests that the value of 1 can be a natural asymptotic limit for the product H t in the long-term evolution of our Universe up to possible small corrections. In the presence of a spinorial space-time geometry, no ad hoc combination of dark matter and dark energy would in any case be needed to get an acceptable value of H and an evolution of the Universe compatible with observation. The use of a spinorial space-time naturally leads to unconventional properties for the space curvature term in Friedmann-like equations. It therefore suggests a major modification of
Optical Properties of Quantum Vacuum. Space-Time Engineering
International Nuclear Information System (INIS)
Gevorkyan, A. S.; Gevorkyan, A. A.
2011-01-01
The propagation of electromagnetic waves in the vacuum is considered taking into account quantum fluctuations in the limits of Maxwell-Langevin (ML) type stochastic differential equations. For a model of fluctuations, type of 'white noise', using ML equations a partial differential equation of second order is obtained which describes the quantum distribution of virtual particles in vacuum. It is proved that in order to satisfy observed facts, the Lamb Shift etc, the virtual particles should be quantized in unperturbed vacuum. It is shown that the quantized virtual particles in toto (approximately 86 percent) are condensed on the 'ground state' energy level. It is proved that the extension of Maxwell electrodynamics with inclusion of quantum vacuum fluctuations may be constructed on a 6D space-time continuum, where 4D is Minkowski space-time and 2D is a compactified subspace. In detail is studied of vacuum's refraction indexes under the influence of external electromagnetic fields.
Quantum gravity effects in Myers-Perry space-times
International Nuclear Information System (INIS)
Litim, Daniel F.; Nikolakopoulos, Konstantinos
2014-01-01
We study quantum gravity effects for Myers-Perry black holes assuming that the leading contributions arise from the renormalization group evolution of Newton’s coupling. Provided that gravity weakens following the asymptotic safety conjecture, we find that quantum effects lift a degeneracy of higher-dimensional black holes, and dominate over kinematical ones induced by rotation, particularly for small black hole mass, large angular momentum, and higher space-time dimensionality. Quantum-corrected space-times display inner and outer horizons, and show the existence of a black hole of smallest mass in any dimension. Ultra-spinning solutions no longer persist. Thermodynamic properties including temperature, specific heat, the Komar integrals, and aspects of black hole mechanics are studied as well. Observing a softening of the ring singularity, we also discuss the validity of classical energy conditions
Interference Cancellation Using Space-Time Processing and Precoding Design
Li, Feng
2013-01-01
Interference Cancellation Using Space-Time Processing and Precoding Design introduces original design methods to achieve interference cancellation, low-complexity decoding and full diversity for a series of multi-user systems. In multi-user environments, co-channel interference will diminish the performance of wireless communications systems. In this book, we investigate how to design robust space-time codes and pre-coders to suppress the co-channel interference when multiple antennas are available. This book offers a valuable reference work for graduate students, academic researchers and engineers who are interested in interference cancellation in wireless communications. Rigorous performance analysis and various simulation illustrations are included for each design method. Dr. Feng Li is a scientific researcher at Cornell University.
Individuation in Quantum Mechanics and Space-Time
Jaeger, Gregg
2010-10-01
Two physical approaches—as distinct, under the classification of Mittelstaedt, from formal approaches—to the problem of individuation of quantum objects are considered, one formulated in spatiotemporal terms and one in quantum mechanical terms. The spatiotemporal approach itself has two forms: one attributed to Einstein and based on the ontology of space-time points, and the other proposed by Howard and based on intersections of world lines. The quantum mechanical approach is also provided here in two forms, one based on interference and another based on a new Quantum Principle of Individuation (QPI). It is argued that the space-time approach to individuation fails and that the quantum approach offers several advantages over it, including consistency with Leibniz’s Principle of Identity of Indiscernibles.
A MAPLE Package for Energy-Momentum Tensor Assessment in Curved Space-Time
International Nuclear Information System (INIS)
Murariu, Gabriel; Praisler, Mirela
2010-01-01
One of the most interesting problem which remain unsolved, since the birth of the General Theory of Relativity (GR), is the energy-momentum localization. All our reflections are within the Lagrange formalism of the field theory. The concept of the energy-momentum tensor for gravitational interactions has a long history. To find a generally accepted expression, there have been different attempts. This paper is dedicated to the investigation of the energy-momentum problem in the theory of General Relativity. We use Einstein [1], Landau-Lifshitz [2], Bergmann-Thomson [3] and Moller's [4] prescriptions to evaluate energy-momentum distribution. In order to cover the huge volume of computation and, bearing in mind to make a general approaching for different space-time configurations, a MAPLE application to succeed in studying the energy momentum tensor was built. In the second part of the paper for two space-time configuration, the comparative results were presented.
Nuclear disassembly time scales using space time correlations
Energy Technology Data Exchange (ETDEWEB)
Durand, D.; Colin, J.; Lecolley, J.F.; Meslin, C.; Aboufirassi, M.; Bougault, R.; Brou, R. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire; Bilwes, B.; Cosmo, F. [Strasbourg-1 Univ., 67 (France); Galin, J. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France); and others
1996-09-01
The lifetime, {tau}, with respect to multifragmentation of highly excited nuclei is deduced from the analysis of strongly damped Pb+Au collisions at 29 MeV/u. The method is based on the study of space-time correlations induced by `proximity` effects between fragments emitted by the two primary products of the reaction and gives the time between the re-separation of the two primary products and the subsequent multifragment decay of one partner. (author). 2 refs.
String dynamics in curved space-time revisited
International Nuclear Information System (INIS)
Marrakchi, A.L.; Singh, L.P.
1989-09-01
The equations of motion of the general background of curved space-time, Einstein's equations, are derived simply by demanding the renormalized energy-momentum tensor of a bosonic string propagating in this background to be traceless. The energy-momentum tensor of such a string is then separable into a holomorphic and an antiholomorphic parts as a consequence of the conformal invariance of the theory regained at the quantum level. (author). 8 refs
On fractal space-time and fractional calculus
Directory of Open Access Journals (Sweden)
Hu Yue
2016-01-01
Full Text Available This paper gives an explanation of fractional calculus in fractal space-time. On observable scales, continuum models can be used, however, when the scale tends to a smaller threshold, a fractional model has to be adopted to describe phenomena in micro/nano structure. A time-fractional Fornberg-Whitham equation is used as an example to elucidate the physical meaning of the fractional order, and its solution process is given by the fractional complex transform.
Semianalytic Solution of Space-Time Fractional Diffusion Equation
Directory of Open Access Journals (Sweden)
A. Elsaid
2016-01-01
Full Text Available We study the space-time fractional diffusion equation with spatial Riesz-Feller fractional derivative and Caputo fractional time derivative. The continuation of the solution of this fractional equation to the solution of the corresponding integer order equation is proved. The series solution of this problem is obtained via the optimal homotopy analysis method (OHAM. Numerical simulations are presented to validate the method and to show the effect of changing the fractional derivative parameters on the solution behavior.
Detecting space-time cancer clusters using residential histories
Jacquez, Geoffrey M.; Meliker, Jaymie R.
2007-04-01
Methods for analyzing geographic clusters of disease typically ignore the space-time variability inherent in epidemiologic datasets, do not adequately account for known risk factors (e.g., smoking and education) or covariates (e.g., age, gender, and race), and do not permit investigation of the latency window between exposure and disease. Our research group recently developed Q-statistics for evaluating space-time clustering in cancer case-control studies with residential histories. This technique relies on time-dependent nearest neighbor relationships to examine clustering at any moment in the life-course of the residential histories of cases relative to that of controls. In addition, in place of the widely used null hypothesis of spatial randomness, each individual's probability of being a case is instead based on his/her risk factors and covariates. Case-control clusters will be presented using residential histories of 220 bladder cancer cases and 440 controls in Michigan. In preliminary analyses of this dataset, smoking, age, gender, race and education were sufficient to explain the majority of the clustering of residential histories of the cases. Clusters of unexplained risk, however, were identified surrounding the business address histories of 10 industries that emit known or suspected bladder cancer carcinogens. The clustering of 5 of these industries began in the 1970's and persisted through the 1990's. This systematic approach for evaluating space-time clustering has the potential to generate novel hypotheses about environmental risk factors. These methods may be extended to detect differences in space-time patterns of any two groups of people, making them valuable for security intelligence and surveillance operations.
The Dirac equation in the Lobachevsky space-time
International Nuclear Information System (INIS)
Paramonov, D.V.; Paramonova, N.N.; Shavokhina, N.S.
2000-01-01
The product of the Lobachevsky space and the time axis is termed the Lobachevsky space-time. The Lobachevsky space is considered as a hyperboloid's sheet in the four-dimensional pseudo-Euclidean space. The Dirac-Fock-Ivanenko equation is reduced to the Dirac equation in two special forms by passing from Lame basis in the Lobachevsky space to the Cartesian basis in the enveloping pseudo-Euclidean space
Space-time reactor kinetics for heterogeneous reactor structure
Energy Technology Data Exchange (ETDEWEB)
Raisic, N [Boris Kidric Institute of nuclear sciences Vinca, Belgrade (Yugoslavia)
1969-11-15
An attempt is made to formulate time dependent diffusion equation based on Feinberg-Galanin theory in the from analogue to the classical reactor kinetic equation. Parameters of these equations could be calculated using the existing codes for static reactor calculation based on the heterogeneous reactor theory. The obtained kinetic equation could be analogues in form to the nodal kinetic equation. Space-time distribution of neutron flux in the reactor can be obtained by solving these equations using standard methods.
Nuclear disassembly time scales using space time correlations
International Nuclear Information System (INIS)
Durand, D.; Colin, J.; Lecolley, J.F.; Meslin, C.; Aboufirassi, M.; Bougault, R.; Brou, R.; Galin, J.; and others.
1996-01-01
The lifetime, τ, with respect to multifragmentation of highly excited nuclei is deduced from the analysis of strongly damped Pb+Au collisions at 29 MeV/u. The method is based on the study of space-time correlations induced by 'proximity' effects between fragments emitted by the two primary products of the reaction and gives the time between the re-separation of the two primary products and the subsequent multifragment decay of one partner. (author)
The energy-momentum operator in curved space-time
International Nuclear Information System (INIS)
Brown, M.R.; Ottewill, A.C.
1983-01-01
It is argued that the only meaningful geometrical measure of the energy-momentum of states of matter described by a free quantum field theory in a general curved space-time is that provided by a normal ordered energy-momentum operator. The finite expectation values of this operator are contrasted with the conventional renormalized expectation values and it is further argued that the use of renormalization theory is inappropriate in this context. (author)
Potentiality of an orbiting interferometer for space-time experiments
International Nuclear Information System (INIS)
Grassi Strini, A.M.; Strini, G.; Tagliaferri, G.
1979-01-01
It is suggested that by putting a Michelson interferometer aboard a spacecraft orbiting around the earth, very substantial progress could be made in space-time experiments. It is estimated that in measurements of e.g. some anisotropy of the light velocity, a spacecraft-borne interferometer of quite small size (0.1 m arm-length) would reach a sensitivity greater by a factor of approximately 10 8 than the best achievements to date of ground-based devices. (author)
2016-01-01
Purpose The objective of this study was to investigate the relationships between primary implant stability as measured by impact response frequency and the structural parameters of trabecular bone using cone-beam computed tomography(CBCT), excluding the effect of cortical bone thickness. Methods We measured the impact response of a dental implant placed into swine bone specimens composed of only trabecular bone without the cortical bone layer using an inductive sensor. The peak frequency of the impact response spectrum was determined as an implant stability criterion (SPF). The 3D microstructural parameters were calculated from CT images of the bone specimens obtained using both micro-CT and CBCT. Results SPF had significant positive correlations with trabecular bone structural parameters (BV/TV, BV, BS, BSD, Tb.Th, Tb.N, FD, and BS/BV) (Pmicro-CT and CBCT (Pimplant stability prediction by combining BV/TV and SMI in the stepwise forward regression analysis. Bone with high volume density and low surface density shows high implant stability. Well-connected thick bone with small marrow spaces also shows high implant stability. The combination of bone density and architectural parameters measured using CBCT can predict the implant stability more accurately than the density alone in clinical diagnoses. PMID:27127692
Quantum field theory in curved space-time
International Nuclear Information System (INIS)
Najmi, A.-H.
1982-09-01
The problem of constructing states for quantum field theories in nonstationary background space-times is set out. A formalism in which the problem of constructing states can be attacked more easily than at present is presented. The ansatz of energy-minimization as a means of constructing states is formulated in this formalism and its general solution for the free scalar field is found. It has been known, in specific cases, that such states suffer from the problem of unitary inequivalence (the pathology). An example in Minowski space-time is presented in which global operators, such as the particle-number operator, do not exist but all physical observables, such as the renormalized energy density are finite. This model has two Fock-sectors as its space of physical states. A simple extension of this model, i.e. enlarging the Fock-space of states is found not to remedy the pathology: in a Robertson-Walker space-time the quantum field acquires an infinite amount of renormalized energy density to the future of the hypersurface on which the energy density is minimized. Finally, the solution of the ansatz of energy minimization for the free, massive Hermitian fermion field is presented. (author)
Nonlocality and Multipartite Entanglement in Asymptotically Flat Space-Times
International Nuclear Information System (INIS)
Moradi, Shahpoor; Amiri, Firouz
2016-01-01
We study the Bell's inequality and multipartite entanglement generation for initially maximally entangled states of free Dirac field in a non inertial frame and asymptotically flat Robertson–Walker space-time. For two qubit case, we show that the Bell's inequality always is violated as measured by the accelerated observers which are in the causally connected regions. On the other hand, for those observers in the causally disconnected regions inequality is not violated for any values of acceleration. The generated three qubit state from two qubit state due to acceleration of one parties has a zero 3-tangle. For a three qubit state, the inequality violated for measurements done by both causally connected and disconnected observers. Initially GHZ state with non zero 3-tangle, in accelerated frame, transformed to a four qubit state with vanishing 4-tangle value. On the other hand, for a W-state with zero 3-tangle, in non inertial frame, transformed to a four qubit state with a non-zero 4-tangle acceleration dependent. In an expanding space-time with asymptotically flat regions, for an initially maximally entangled state, the maximum value of violation of Bell's inequality in the far past decreased in the far future due to cosmological particle creation. For some initially maximally entangled states, the generated four qubit state due to expansion of space-time, has non vanishing 4-tangle. (paper)
Relativistic helicity and link in Minkowski space-time
International Nuclear Information System (INIS)
Yoshida, Z.; Kawazura, Y.; Yokoyama, T.
2014-01-01
A relativistic helicity has been formulated in the four-dimensional Minkowski space-time. Whereas the relativistic distortion of space-time violates the conservation of the conventional helicity, the newly defined relativistic helicity conserves in a barotropic fluid or plasma, dictating a fundamental topological constraint. The relation between the helicity and the vortex-line topology has been delineated by analyzing the linking number of vortex filaments which are singular differential forms representing the pure states of Banach algebra. While the dimension of space-time is four, vortex filaments link, because vorticities are primarily 2-forms and the corresponding 2-chains link in four dimension; the relativistic helicity measures the linking number of vortex filaments that are proper-time cross-sections of the vorticity 2-chains. A thermodynamic force yields an additional term in the vorticity, by which the vortex filaments on a reference-time plane are no longer pure states. However, the vortex filaments on a proper-time plane remain to be pure states, if the thermodynamic force is exact (barotropic), thus, the linking number of vortex filaments conserves
A stochastic space-time model for intermittent precipitation occurrences
Sun, Ying; Stein, Michael L.
2016-01-01
Modeling a precipitation field is challenging due to its intermittent and highly scale-dependent nature. Motivated by the features of high-frequency precipitation data from a network of rain gauges, we propose a threshold space-time t random field (tRF) model for 15-minute precipitation occurrences. This model is constructed through a space-time Gaussian random field (GRF) with random scaling varying along time or space and time. It can be viewed as a generalization of the purely spatial tRF, and has a hierarchical representation that allows for Bayesian interpretation. Developing appropriate tools for evaluating precipitation models is a crucial part of the model-building process, and we focus on evaluating whether models can produce the observed conditional dry and rain probabilities given that some set of neighboring sites all have rain or all have no rain. These conditional probabilities show that the proposed space-time model has noticeable improvements in some characteristics of joint rainfall occurrences for the data we have considered.
A stochastic space-time model for intermittent precipitation occurrences
Sun, Ying
2016-01-28
Modeling a precipitation field is challenging due to its intermittent and highly scale-dependent nature. Motivated by the features of high-frequency precipitation data from a network of rain gauges, we propose a threshold space-time t random field (tRF) model for 15-minute precipitation occurrences. This model is constructed through a space-time Gaussian random field (GRF) with random scaling varying along time or space and time. It can be viewed as a generalization of the purely spatial tRF, and has a hierarchical representation that allows for Bayesian interpretation. Developing appropriate tools for evaluating precipitation models is a crucial part of the model-building process, and we focus on evaluating whether models can produce the observed conditional dry and rain probabilities given that some set of neighboring sites all have rain or all have no rain. These conditional probabilities show that the proposed space-time model has noticeable improvements in some characteristics of joint rainfall occurrences for the data we have considered.
Geodesics in Goedel-type space-times
International Nuclear Information System (INIS)
Calvao, M.O.; Soares, I.D.; Tiomno, J.
1988-01-01
The geodesic curves of the homogeneous Goedel-type space-times, which constitute a two-parameter ({ l and Ω}) class of solutions presented to several theories of gravitation (general relativity, Einstein-Cartan and higher derivative) are investigated. The qualitative properties of those curves by means of the introduction of an effective potential and then accomplish the analytical integration of the equations of motion are examined. It is shown that some of the qualitative features of the free motion in Godel's universe (l 2 =2Ω 2 ) are preserved in all space-times, namely the projections of the geodesics onto the 2-surface (r,ψ) are simple closed curves, and the geodesics for which the ratio of azymuthal angular momentum to total energy, υ is equal to zero always cross the origin r = o. However, two new cases appear: (i) radially unbounded geodesics with υ assuming any (real) value, which may occur only for the causal space-times (l 2 ≥ 4 Ω 2 ), and (ii) geodesics with υ bounded both below and above, which always occur for the circular family (l 2 [pt
Experimental Constraints of the Exotic Shearing of Space-Time
Energy Technology Data Exchange (ETDEWEB)
Richardson, Jonathan William [Univ. of Chicago, IL (United States)
2016-08-01
The Holometer program is a search for rst experimental evidence that space-time has quantum structure. The detector consists of a pair of co-located 40-m power-recycled interferometers whose outputs are read out synchronously at 50 MHz, achieving sensitivity to spatiallycorrelated uctuations in dierential position on time scales shorter than the light-crossing time of the instruments. Unlike gravitational wave interferometers, which time-resolve transient geometrical disturbances in the spatial background, the Holometer is searching for a universal, stationary quantization noise of the background itself. This dissertation presents the nal results of the Holometer Phase I search, an experiment congured for sensitivity to exotic coherent shearing uctuations of space-time. Measurements of high-frequency cross-spectra of the interferometer signals obtain sensitivity to spatially-correlated eects far exceeding any previous measurement, in a broad frequency band extending to 7.6 MHz, twice the inverse light-crossing time of the apparatus. This measurement is the statistical aggregation of 2.1 petabytes of 2-byte dierential position measurements obtained over a month-long exposure time. At 3 signicance, it places an upper limit on the coherence scale of spatial shear two orders of magnitude below the Planck length. The result demonstrates the viability of this novel spatially-correlated interferometric detection technique to reach unprecedented sensitivity to coherent deviations of space-time from classicality, opening the door for direct experimental tests of theories of relational quantum gravity.
On the performance of diagonal lattice space-time codes
Abediseid, Walid
2013-11-01
There has been tremendous work done on designing space-time codes for the quasi-static multiple-input multiple output (MIMO) channel. All the coding design up-to-date focuses on either high-performance, high rates, low complexity encoding and decoding, or targeting a combination of these criteria [1]-[9]. In this paper, we analyze in details the performance limits of diagonal lattice space-time codes under lattice decoding. We present both lower and upper bounds on the average decoding error probability. We first derive a new closed-form expression for the lower bound using the so-called sphere lower bound. This bound presents the ultimate performance limit a diagonal lattice space-time code can achieve at any signal-to-noise ratio (SNR). The upper bound is then derived using the union-bound which demonstrates how the average error probability can be minimized by maximizing the minimum product distance of the code. Combining both the lower and the upper bounds on the average error probability yields a simple upper bound on the the minimum product distance that any (complex) lattice code can achieve. At high-SNR regime, we discuss the outage performance of such codes and provide the achievable diversity-multiplexing tradeoff under lattice decoding. © 2013 IEEE.
Stability and Hopf Bifurcation in a Computer Virus Model with Multistate Antivirus
Directory of Open Access Journals (Sweden)
Tao Dong
2012-01-01
Full Text Available By considering that people may immunize their computers with countermeasures in susceptible state, exposed state and using anti-virus software may take a period of time, a computer virus model with time delay based on an SEIR model is proposed. We regard time delay as bifurcating parameter to study the dynamical behaviors which include local asymptotical stability and local Hopf bifurcation. By analyzing the associated characteristic equation, Hopf bifurcation occurs when time delay passes through a sequence of critical value. The linerized model and stability of the bifurcating periodic solutions are also derived by applying the normal form theory and the center manifold theorem. Finally, an illustrative example is also given to support the theoretical results.
Robust flow stability: Theory, computations and experiments in near wall turbulence
Bobba, Kumar Manoj
Helmholtz established the field of hydrodynamic stability with his pioneering work in 1868. From then on, hydrodynamic stability became an important tool in understanding various fundamental fluid flow phenomena in engineering (mechanical, aeronautics, chemical, materials, civil, etc.) and science (astrophysics, geophysics, biophysics, etc.), and turbulence in particular. However, there are many discrepancies between classical hydrodynamic stability theory and experiments. In this thesis, the limitations of traditional hydrodynamic stability theory are shown and a framework for robust flow stability theory is formulated. A host of new techniques like gramians, singular values, operator norms, etc. are introduced to understand the role of various kinds of uncertainty. An interesting feature of this framework is the close interplay between theory and computations. It is shown that a subset of Navier-Stokes equations are globally, non-nonlinearly stable for all Reynolds number. Yet, invoking this new theory, it is shown that these equations produce structures (vortices and streaks) as seen in the experiments. The experiments are done in zero pressure gradient transiting boundary layer on a flat plate in free surface tunnel. Digital particle image velocimetry, and MEMS based laser Doppler velocimeter and shear stress sensors have been used to make quantitative measurements of the flow. Various theoretical and computational predictions are in excellent agreement with the experimental data. A closely related topic of modeling, simulation and complexity reduction of large mechanics problems with multiple spatial and temporal scales is also studied. A nice method that rigorously quantifies the important scales and automatically gives models of the problem to various levels of accuracy is introduced. Computations done using spectral methods are presented.
International Nuclear Information System (INIS)
Krishnani, Mayur; Basu, Dipankar N.
2017-01-01
Highlights: • Computational model developed for single-phase rectangular natural circulation loop. • Role of loop inclination to vertical on thermalhydraulic stability is explored. • Inclination has strong stabilizing effect due to lower effective gravitation force. • Increase in tilt angle reduces settling time and highest amplitude of oscillation. • An angle of 15° is suggested for the selected loop geometry. - Abstract: Controlling stability behavior of single-phase natural circulation loops, without significantly affecting its steady-state characteristics, is a topic of wide research interest. Present study explores the role of loop inclination on a particular loop geometry. Accordingly a 3D computational model of a rectangular loop is developed and transient conservation equations are solved to obtain the temporal variation in flow parameters. Starting from the quiescent state, simulations are performed for selected sets of operating conditions and also with a few selected inclination angles. System experiences instability at higher heater powers and also with higher sink temperatures. Inclination is found to have a strong stabilizing influence owing to the reduction in the effective gravitational acceleration and subsequent decline in local buoyancy effects. The settling time and highest amplitude of oscillations substantially reduces for a stable system with a small inclination. Typically-unstable systems can also suppress the oscillations, when subjected to tilting, within a reasonable period of time. It is possible to stabilize the loop within shorter time span by increasing the tilt angle, but at the expense of reduction in steady-state flow rate. Overall a tilt angle of 15° is suggested for the selected geometry. Results from the 3D model is compared with the predictions from an indigenous 1D code. While similar qualitative influence of inclination is observed, the 1D model predicts early appearance of the stability threshold and hence hints
Singular lensing from the scattering on special space-time defects
Energy Technology Data Exchange (ETDEWEB)
Mavromatos, Nick E. [University of Valencia - CSIC, Department of Theoretical Physics and IFIC, Valencia (Spain); King' s College London, Theoretical Particle Physics and Cosmology Group, Department of Physics, London (United Kingdom); Papavassiliou, Joannis [University of Valencia - CSIC, Department of Theoretical Physics and IFIC, Valencia (Spain)
2018-01-15
It is well known that certain special classes of self-gravitating point-like defects, such as global (non gauged) monopoles, give rise to non-asymptotically flat space-times characterized by solid angle deficits, whose size depends on the details of the underlying microscopic models. The scattering of electrically neutral particles on such space-times is described by amplitudes that exhibit resonant behaviour when thescattering and deficit angles coincide. This, in turn, leads to ring-like structures where the cross sections are formally divergent (''singular lensing''). In this work, we revisit this particular phenomenon, with the twofold purpose of placing it in a contemporary and more general context, in view of renewed interest in the theory and general phenomenology of such defects, and, more importantly, of addressing certain subtleties that appear in the particular computation that leads to the aforementioned effect. In particular, by adopting a specific regularization procedure for the formally infinite Legendre series encountered, we manage to ensure the recovery of the Minkowski space-time, and thus the disappearance of the lensing phenomenon, in the no-defect limit, and the validity of the optical theorem for the elastic total cross section. In addition, the singular nature of the phenomenon is confirmed by means of an alternative calculation, which, unlike the original approach, makes no use of the generating function of the Legendre polynomials, but rather exploits the asymptotic properties of the Fresnel integrals. (orig.)
Singular lensing from the scattering on special space-time defects
International Nuclear Information System (INIS)
Mavromatos, Nick E.; Papavassiliou, Joannis
2018-01-01
It is well known that certain special classes of self-gravitating point-like defects, such as global (non gauged) monopoles, give rise to non-asymptotically flat space-times characterized by solid angle deficits, whose size depends on the details of the underlying microscopic models. The scattering of electrically neutral particles on such space-times is described by amplitudes that exhibit resonant behaviour when thescattering and deficit angles coincide. This, in turn, leads to ring-like structures where the cross sections are formally divergent (''singular lensing''). In this work, we revisit this particular phenomenon, with the twofold purpose of placing it in a contemporary and more general context, in view of renewed interest in the theory and general phenomenology of such defects, and, more importantly, of addressing certain subtleties that appear in the particular computation that leads to the aforementioned effect. In particular, by adopting a specific regularization procedure for the formally infinite Legendre series encountered, we manage to ensure the recovery of the Minkowski space-time, and thus the disappearance of the lensing phenomenon, in the no-defect limit, and the validity of the optical theorem for the elastic total cross section. In addition, the singular nature of the phenomenon is confirmed by means of an alternative calculation, which, unlike the original approach, makes no use of the generating function of the Legendre polynomials, but rather exploits the asymptotic properties of the Fresnel integrals. (orig.)
Singular lensing from the scattering on special space-time defects
Mavromatos, Nick E.; Papavassiliou, Joannis
2018-01-01
It is well known that certain special classes of self-gravitating point-like defects, such as global (non gauged) monopoles, give rise to non-asymptotically flat space-times characterized by solid angle deficits, whose size depends on the details of the underlying microscopic models. The scattering of electrically neutral particles on such space-times is described by amplitudes that exhibit resonant behaviour when thescattering and deficit angles coincide. This, in turn, leads to ring-like structures where the cross sections are formally divergent ("singular lensing"). In this work, we revisit this particular phenomenon, with the twofold purpose of placing it in a contemporary and more general context, in view of renewed interest in the theory and general phenomenology of such defects, and, more importantly, of addressing certain subtleties that appear in the particular computation that leads to the aforementioned effect. In particular, by adopting a specific regularization procedure for the formally infinite Legendre series encountered, we manage to ensure the recovery of the Minkowski space-time, and thus the disappearance of the lensing phenomenon, in the no-defect limit, and the validity of the optical theorem for the elastic total cross section. In addition, the singular nature of the phenomenon is confirmed by means of an alternative calculation, which, unlike the original approach, makes no use of the generating function of the Legendre polynomials, but rather exploits the asymptotic properties of the Fresnel integrals.
Land use and land cover change based on historical space-time model
Sun, Qiong; Zhang, Chi; Liu, Min; Zhang, Yongjing
2016-09-01
Land use and cover change is a leading edge topic in the current research field of global environmental changes and case study of typical areas is an important approach understanding global environmental changes. Taking the Qiantang River (Zhejiang, China) as an example, this study explores automatic classification of land use using remote sensing technology and analyzes historical space-time change by remote sensing monitoring. This study combines spectral angle mapping (SAM) with multi-source information and creates a convenient and efficient high-precision land use computer automatic classification method which meets the application requirements and is suitable for complex landform of the studied area. This work analyzes the histological space-time characteristics of land use and cover change in the Qiantang River basin in 2001, 2007 and 2014, in order to (i) verify the feasibility of studying land use change with remote sensing technology, (ii) accurately understand the change of land use and cover as well as historical space-time evolution trend, (iii) provide a realistic basis for the sustainable development of the Qiantang River basin and (iv) provide a strong information support and new research method for optimizing the Qiantang River land use structure and achieving optimal allocation of land resources and scientific management.
Re-examination of globally flat space-time.
Directory of Open Access Journals (Sweden)
Michael R Feldman
Full Text Available In the following, we offer a novel approach to modeling the observed effects currently attributed to the theoretical concepts of "dark energy," "dark matter," and "dark flow." Instead of assuming the existence of these theoretical concepts, we take an alternative route and choose to redefine what we consider to be inertial motion as well as what constitutes an inertial frame of reference in flat space-time. We adopt none of the features of our current cosmological models except for the requirement that special and general relativity be local approximations within our revised definition of inertial systems. Implicit in our ideas is the assumption that at "large enough" scales one can treat objects within these inertial systems as point-particles having an insignificant effect on the curvature of space-time. We then proceed under the assumption that time and space are fundamentally intertwined such that time- and spatial-translational invariance are not inherent symmetries of flat space-time (i.e., observable clock rates depend upon both relative velocity and spatial position within these inertial systems and take the geodesics of this theory in the radial Rindler chart as the proper characterization of inertial motion. With this commitment, we are able to model solely with inertial motion the observed effects expected to be the result of "dark energy," "dark matter," and "dark flow." In addition, we examine the potential observable implications of our theory in a gravitational system located within a confined region of an inertial reference frame, subsequently interpreting the Pioneer anomaly as support for our redefinition of inertial motion. As well, we extend our analysis into quantum mechanics by quantizing for a real scalar field and find a possible explanation for the asymmetry between matter and antimatter within the framework of these redefined inertial systems.
QCD-instantons and conformal space-time inversion symmetry
International Nuclear Information System (INIS)
Klammer, D.
2008-04-01
In this paper, we explore the appealing possibility that the strong suppression of large-size QCD instantons - as evident from lattice data - is due to a surviving conformal space-time inversion symmetry. This symmetry is both suggested from the striking invariance of highquality lattice data for the instanton size distribution under inversion of the instanton size ρ→(left angle ρ right angle 2 )/(ρ) and from the known validity of space-time inversion symmetry in the classical instanton sector. We project the instanton calculus onto the four-dimensional surface of a five-dimensional sphere via conformal stereographic mapping, before investigating conformal inversion. This projection to a compact, curved geometry is both to avoid the occurence of divergences and to introduce the average instanton size left angle ρ right angle from the lattice data as a new length scale. The average instanton size is identified with the radius b of this 5d-sphere and acts as the conformal inversion radius. For b= left angle ρ right angle, our corresponding results are almost perfectly symmetric under space-time inversion and in good qualitative agreement with the lattice data. For (ρ)/(b)→0 we recover the familiar results of instanton perturbation theory in flat 4d-space. Moreover, we illustrate that a (weakly broken) conformal inversion symmetry would have significant consequences for QCD beyond instantons. As a further successful test for inversion symmetry, we present striking implications for another instanton dominated lattice observable, the chirality-flip ratio in the QCD vacuum. (orig.)
ADM Mass for Asymptotically de Sitter Space-Time
International Nuclear Information System (INIS)
Huang Shiming; Yue Ruihong; Jia Dongyan
2010-01-01
In this paper, an ADM mass formula for asymptotically de Sitter(dS) space-time is derived from the energy-momentum tensor. We take the vacuum dS space as the background and investigate the ADM mass of the (d + 3)-dimensional sphere-symmetric space with a positive cosmological constant, and find that the ADM mass of asymptotically dS space is based on the ADM mass of Schwarzschild field and the cosmological background brings some small mass contribution as well. (general)
P-adic space-time and string theory
International Nuclear Information System (INIS)
Volovich, I.V.
1987-01-01
Arguments for the possibility of a p-adic structure of space-time are advanced. The p-adic analog of the Veneziano amplitude is proposed, and this permits a start to be made on the construction of the theory of p-adic strings. The same questions are considered over Galois fields, for which the analog of the Veneziano amplitude is a Jacobi sum that can be expressed in terms of p-adic cohomologies of Fermat curves. An explicit expression for the vertex operator of the corresponding string theory is given
Blackbody radiation from light cone in flat space time
International Nuclear Information System (INIS)
Gerlach, U.H.
1983-01-01
Blackbody radiation in flat space-time is not necessarily associated with the flat event horizon of a single accelerated observer. The author considers a spherical bubble which expands in a uniformly accelerating fashion. Its history traces out a time-like hyperboloid. Suppose the bubble membrane has a spatially isotropic and homogeneous (surface) stress energy tensor i.e. the membrane is made out of the stiffest possible material permitted by causality considerations. It follows that this bubble membrane is in equilibrium even though it is expanding. Such an expanding bubble membrane may serve as a detector of electromagnetic radiation if the membrane can interact with the electromagnetic field. (Auth.)
Massless fields in curved space-time: The conformal formalism
International Nuclear Information System (INIS)
Castagnino, M.A.; Sztrajman, J.B.
1986-01-01
A conformally invariant theory for massless quantum fields in curved space-time is formulated. We analyze the cases of spin-0, - 1/2 , and -1. The theory is developed in the important case of an ''expanding universe,'' generalizing the particle model of ''conformal transplantation'' known for spin-0 to spins- 1/2 and -1. For the spin-1 case two methods introducing new conformally invariant gauge conditions are stated, and a problem of inconsistency that was stated for spin-1 is overcome
Annotated trajectories and the Space-Time-Cube
DEFF Research Database (Denmark)
Kveladze, Irma; Kraak, Menno-Jan
2012-01-01
too, because these have not been adopted to the purpose. A suitable solution to display and study movements is the Space-Time-Cube (STC), the graphic representation of Hägerstrand’s Time Geography. This paper answers the question of how suitable the STC is to display the above describe combination...... of trajectories and annotations to avoid the visual clutter. Although the STC will be described here as a stand-alone solution it is part of a wider geovisual analytics environment and is used next to maps and other graphics to be able to answer user questions. As a case study data set the travel log data...
Space, Time, Matter, and Form Essays on Aristotle's Physics
Bostock, David
2006-01-01
Space, Time, Matter, and Form collects ten of David Bostock's essays on themes from Aristotle's Physics, four of them published here for the first time. The first five papers look at issues raised in the first two books of the Physics, centred on notions of matter and form, and the idea of substance as what persists through change. They also range over other of Aristotle's scientific works, such as his biology and psychology and the account of change in his De Generatione et Corruptione. The volume's remaining essays examine themes in later books of the Physics, including infinity, place, time
A heterotic N=2 string with space-time supersymmetry
International Nuclear Information System (INIS)
Bellucci, S.; Galajinsky, A.; Lechtenfeld, O.
2001-02-01
It is reconsidered the issue of embedding space-time fermions into the four dimensional N=2 world-sheet supersymmetric string. A new heterotic theory is constructed, taking the right-movers from the N =4 topological extension of the conventional N=2 string but a c=0 conformal field theory supporting target-space supersymmetry for the left-moving sector. The global bosonic symmetry of the full formalism proves to be U(1,1), just as in the usual N=2 string. Quantization reveals a spectrum of only two physical states, one boson and one fermion, which fall in a multiplet of (1,0) supersymmetry
The algebraic approach to space-time geometry
International Nuclear Information System (INIS)
Heller, M.; Multarzynski, P.; Sasin, W.
1989-01-01
A differential manifold can be defined in terms of smooth real functions carried by it. By rejecting the postulate, in such a definition, demanding the local diffeomorphism of a manifold to the Euclidean space, one obtains the so-called differential space concept. Every subset of R n turns out to be a differential space. Extensive parts of differential geometry on differential spaces, developed by Sikorski, are reviewed and adapted to relativistic purposes. Differential space as a new model of space-time is proposed. The Lorentz structure and Einstein's field equations on differential spaces are discussed. 20 refs. (author)
Quantum stress tensor in Schwarzschild space-time
International Nuclear Information System (INIS)
Howard, K.W.; Candelas, P.
1984-01-01
The vacuum expectation value of the stress-energy tensor for the Hartle-Hawking state in Schwartzschild space-time has been calculated for the conformal scalar field. separates naturally into the sum of two terms. The first coincides with an approximate expression suggested by Page. The second term is a ''remainder'' that may be evaluated numerically. The total expression is in good qualitative agreement with Page's approximation. These results are at variance with earlier results given by Fawcett whose error is explained
Space-Time, Phenomenology, and the Picture Theory of Language
Grelland, Hans Herlof
To estimate Minkowski's introduction of space-time in relativity, the case is made for the view that abstract language and mathematics carries meaning not only by its connections with observation but as pictures of facts. This view is contrasted to the more traditional intuitionism of Hume, Mach, and Husserl. Einstein's attempt at a conceptual reconstruction of space and time as well as Husserl's analysis of the loss of meaning in science through increasing abstraction is analysed. Wittgenstein's picture theory of language is used to explain how meaning is conveyed by abstract expressions, with the Minkowski space as a case.
Extended Cellular Automata Models of Particles and Space-Time
Beedle, Michael
2005-04-01
Models of particles and space-time are explored through simulations and theoretical models that use Extended Cellular Automata models. The expanded Cellular Automata Models consist go beyond simple scalar binary cell-fields, into discrete multi-level group representations like S0(2), SU(2), SU(3), SPIN(3,1). The propagation and evolution of these expanded cellular automatas are then compared to quantum field theories based on the "harmonic paradigm" i.e. built by an infinite number of harmonic oscillators, and with gravitational models.
On quantum field theory in curved space-time
International Nuclear Information System (INIS)
Hajicek, P.
1976-01-01
It is well known that the existence of quanta or particles of a given field is directly revealed by only a subset of all possible experiments with the field. It is considered a class of such experiments performable at any regular point of any space-time, which includes all terrestrial particle experiments as well as asymptotic observations of an evaporating black hole. A definition based on this class keeps the quanta observable and renders the notion of particle relative and local. Any complicated mathematics is avoided with the intention to emphasize the physical ideas
Mathematical aspects of the discrete space-time hypothesis
International Nuclear Information System (INIS)
Sardanashvili, G.A.
1979-01-01
A hypothesis of a microcosm space discreteness is considered from the theoretical-mathematical point of view. The type of topological spaces, which formalizes representations on the discrete space-time, is determined. It is explained, how these spaces arise in physical models. The physical task, in which the discrete space could arise as a version of its solution, is considered. It is shown that the discrete structure of space can arise with a certain interaction type in the system, for example, with its considerable self-shielding, which can take place, in particular, in the particles or in the cosmological and astrophysical singularities
Naked singularities in higher dimensional Vaidya space-times
International Nuclear Information System (INIS)
Ghosh, S. G.; Dadhich, Naresh
2001-01-01
We investigate the end state of the gravitational collapse of a null fluid in higher-dimensional space-times. Both naked singularities and black holes are shown to be developing as the final outcome of the collapse. The naked singularity spectrum in a collapsing Vaidya region (4D) gets covered with the increase in dimensions and hence higher dimensions favor a black hole in comparison to a naked singularity. The cosmic censorship conjecture will be fully respected for a space of infinite dimension
Quantum field theory in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Hajicek, P [Bern Univ. (Switzerland). Inst. fuer Theoretische Physik
1976-06-11
It is well known that the existence of quanta or particles of a given field is directly revealed by only a subset of all possible experiments with the field. A class of such experiments performable at any regular point of any space-time is considered, which includes all terrestrial particle experiments as well as asymptotic observations of an evaporating black hole. A definition based on this class keeps the quanta observable and renders the notion of particle relative and local. Any complicated mathematics is avoided with the intention to emphasize the physical ideas.
Founding Gravitation in 4D Euclidean Space-Time Geometry
International Nuclear Information System (INIS)
Winkler, Franz-Guenter
2010-01-01
The Euclidean interpretation of special relativity which has been suggested by the author is a formulation of special relativity in ordinary 4D Euclidean space-time geometry. The natural and geometrically intuitive generalization of this view involves variations of the speed of light (depending on location and direction) and a Euclidean principle of general covariance. In this article, a gravitation model by Jan Broekaert, which implements a view of relativity theory in the spirit of Lorentz and Poincare, is reconstructed and shown to fulfill the principles of the Euclidean approach after an appropriate reinterpretation.
Simulation of the space-time evolution of color-flux tubes (guidelines to the TERMITE program)
International Nuclear Information System (INIS)
Dyrek, A.
1990-08-01
We give the description of the computer program which simulates boost-invariant evolution of color-flux tubes in high-energy processes. The program provides a graphic demonstration of space-time trajectories of created particles and can also be used as Monte-Carlo generator of events. (author)
Space, time, and the third dimension (model error)
Moss, Marshall E.
1979-01-01
The space-time tradeoff of hydrologic data collection (the ability to substitute spatial coverage for temporal extension of records or vice versa) is controlled jointly by the statistical properties of the phenomena that are being measured and by the model that is used to meld the information sources. The control exerted on the space-time tradeoff by the model and its accompanying errors has seldom been studied explicitly. The technique, known as Network Analyses for Regional Information (NARI), permits such a study of the regional regression model that is used to relate streamflow parameters to the physical and climatic characteristics of the drainage basin.The NARI technique shows that model improvement is a viable and sometimes necessary means of improving regional data collection systems. Model improvement provides an immediate increase in the accuracy of regional parameter estimation and also increases the information potential of future data collection. Model improvement, which can only be measured in a statistical sense, cannot be quantitatively estimated prior to its achievement; thus an attempt to upgrade a particular model entails a certain degree of risk on the part of the hydrologist.
Brain system for mental orientation in space, time, and person.
Peer, Michael; Salomon, Roy; Goldberg, Ilan; Blanke, Olaf; Arzy, Shahar
2015-09-01
Orientation is a fundamental mental function that processes the relations between the behaving self to space (places), time (events), and person (people). Behavioral and neuroimaging studies have hinted at interrelations between processing of these three domains. To unravel the neurocognitive basis of orientation, we used high-resolution 7T functional MRI as 16 subjects compared their subjective distance to different places, events, or people. Analysis at the individual-subject level revealed cortical activation related to orientation in space, time, and person in a precisely localized set of structures in the precuneus, inferior parietal, and medial frontal cortex. Comparison of orientation domains revealed a consistent order of cortical activity inside the precuneus and inferior parietal lobes, with space orientation activating posterior regions, followed anteriorly by person and then time. Core regions at the precuneus and inferior parietal lobe were activated for multiple orientation domains, suggesting also common processing for orientation across domains. The medial prefrontal cortex showed a posterior activation for time and anterior for person. Finally, the default-mode network, identified in a separate resting-state scan, was active for all orientation domains and overlapped mostly with person-orientation regions. These findings suggest that mental orientation in space, time, and person is managed by a specific brain system with a highly ordered internal organization, closely related to the default-mode network.
D-particle Recoil Space Times and "Glueball" Masses
Mavromatos, Nikolaos E; Mavromatos, Nick E.; Winstanley, Elizabeth
2001-01-01
We discuss the properties of matter in a D-dimensional anti-de-Sitter-type space time induced dynamically by the recoil of a very heavy D(irichlet)-particle defect embedded in it. The particular form of the recoil geometry, which from a world-sheet view point follows from logarithmic conformal field theory deformations of the pertinent sigma-models, results in the presence of both infrared and ultraviolet (spatial) cut-offs. These are crucial in ensuring the presence of mass gaps in scalar matter propagating in the D-particle recoil space time. The analogy of this problem with the Liouville-string approach to QCD, suggested earlier by John Ellis and one of the present authors, prompts us to identify the resulting scalar masses with those obtained in the supergravity approach based on the Maldacena's conjecture, but without the imposition of any supersymmetry in our case. Within reasonable numerical uncertainties, we observe that agreement is obtained between the two approaches for a particular value of the ra...
Exactly solvable string models of curved space-time backgrounds
International Nuclear Information System (INIS)
Russo, J.G.
1995-01-01
We consider a new 3-parameter class of exact 4-dimensional solutions in closed string theory and solve the corresponding string model, determining the physical spectrum and the partition function. The background fields (4-metric, antisymmetric tensor, two Kaluza-Klein vector fields, dilaton and modulus) generically describe axially symmetric stationary rotating (electro)magnetic flux-tube type universes. Backgrounds of this class include both the ''dilatonic'' (a=1) and ''Kaluza-Klein'' (a=√(3)) Melvin solutions and the uniform magnetic field solution, as well as some singular space-times. Solvability of the string σ-model is related to its connection via duality to a simpler model which is a ''twisted'' product of a flat 2-space and a space dual to 2-plane. We discuss some physical properties of this model (tachyonic instabilities in the spectrum, gyromagnetic ratio, issue of singularities, etc.). It provides one of the first examples of a consistent solvable conformal string model with explicit D=4 curved space-time interpretation. (orig.)
Physics in space-time with scale-dependent metrics
Balankin, Alexander S.
2013-10-01
We construct three-dimensional space Rγ3 with the scale-dependent metric and the corresponding Minkowski space-time Mγ,β4 with the scale-dependent fractal (DH) and spectral (DS) dimensions. The local derivatives based on scale-dependent metrics are defined and differential vector calculus in Rγ3 is developed. We state that Mγ,β4 provides a unified phenomenological framework for dimensional flow observed in quite different models of quantum gravity. Nevertheless, the main attention is focused on the special case of flat space-time M1/3,14 with the scale-dependent Cantor-dust-like distribution of admissible states, such that DH increases from DH=2 on the scale ≪ℓ0 to DH=4 in the infrared limit ≫ℓ0, where ℓ0 is the characteristic length (e.g. the Planck length, or characteristic size of multi-fractal features in heterogeneous medium), whereas DS≡4 in all scales. Possible applications of approach based on the scale-dependent metric to systems of different nature are briefly discussed.
Relativity for everyone how space-time bends
Fischer, Kurt
2015-01-01
This book, now in a revised and updated second edition, explains the theory of special and general relativity in detail without approaching Einstein's life or the historical background. The text is formulated in such a way that the reader will be able to understand the essence intuitively, and new sections have been added on time machines, the twin paradoxes, and tensors. The first part of the book focuses on the essentials of special relativity. It explains the famous equivalence between mass and energy and tells why Einstein was able to use the theory of electrodynamics as a template for his "electrodynamics of moving bodies". General relativity is then addressed, mainly with the help of thought experiments. Reference is made to the previously introduced special relativity and the equivalence principle and, using many figures, it is explained how space-time is bending under gravity. The climax of the book is the Einstein equation of gravity, which describes the way in which matter bends space-time. The read...
Representations of G+++ and the role of space-time
International Nuclear Information System (INIS)
Kleinschmidt, A.; West, P.
2004-01-01
We consider the decomposition of the adjoint and fundamental representations of very extended Kac-Moody algebras G+++ with respect to their regular A type subalgebra which, in the corresponding non-linear realisation, is associated with gravity. We find that for many very extended algebras almost all the A type representations that occur in the decomposition of the fundamental representations also occur in the adjoint representation of G+++ . In particular, for E 8 +++ , this applies to all its fundamental representations. However, there are some important examples, such as A N-3 +++ , where this is not true and indeed the adjoint representation contains no generator that can be identified with a space-time translation. We comment on the significance of these results for how space-time can occur in the non-linear realisation based on G+++ . Finally we show that there is a correspondence between the A representations that occur in the fundamental representation associated with the very extended node and the adjoint representation of G+++ which is consistent with the interpretation of the former as charges associated with brane solutions. (author)
Relativistic space-time positioning: principles and strategies
Tartaglia, Angelo
2013-11-01
Starting from the description of space- time as a curved four-dimensional manifold, null Gaussian coordinates systems as appropriate for relativistic positioning will be discussed. Different approaches and strategies will be reviewed, implementing the null coordinates with both continuous and pulsating electromagnetic signals. In particular, methods based on purely local measurements of proper time intervals between pulses will be expounded and the various possible sources of uncertainty will be analyzed. As sources of pulses both artificial and natural emitters will be considered. The latter will concentrate on either radio- or X ray-emitting pulsars, discussing advantages and drawbacks. As for artificial emitters, various solutions will be presented, from satellites orbiting the Earth to broadcasting devices carried both by spacecrafts and celestial bodies of the solar system. In general the accuracy of the positioning is expected to be limited, besides the instabilities and drift of the sources, by the precision of the local clock, but in any case in long journeys systematic cumulated errors will tend to become dominant. The problem can be kept under control properly using a high level of redundancy in the procedure for the calculation of the coordinates of the receiver and by mixing a number of different and complementary strategies. Finally various possibilities for doing fundamental physics experiments by means of space-time topography techniques will shortly be presented and discussed.
Introducing the Dimensional Continuous Space-Time Theory
International Nuclear Information System (INIS)
Martini, Luiz Cesar
2013-01-01
This article is an introduction to a new theory. The name of the theory is justified by the dimensional description of the continuous space-time of the matter, energy and empty space, that gathers all the real things that exists in the universe. The theory presents itself as the consolidation of the classical, quantum and relativity theories. A basic equation that describes the formation of the Universe, relating time, space, matter, energy and movement, is deduced. The four fundamentals physics constants, light speed in empty space, gravitational constant, Boltzmann's constant and Planck's constant and also the fundamentals particles mass, the electrical charges, the energies, the empty space and time are also obtained from this basic equation. This theory provides a new vision of the Big-Bang and how the galaxies, stars, black holes and planets were formed. Based on it, is possible to have a perfect comprehension of the duality between wave-particle, which is an intrinsic characteristic of the matter and energy. It will be possible to comprehend the formation of orbitals and get the equationing of atomics orbits. It presents a singular comprehension of the mass relativity, length and time. It is demonstrated that the continuous space-time is tridimensional, inelastic and temporally instantaneous, eliminating the possibility of spatial fold, slot space, worm hole, time travels and parallel universes. It is shown that many concepts, like dark matter and strong forces, that hypothetically keep the cohesion of the atomics nucleons, are without sense.
On the structure of space-time caustics
International Nuclear Information System (INIS)
Rosquist, K.
1983-01-01
Caustics formed by timelike and null geodesics in a space-time M are investigated. Care is taken to distinguish the conjugate points in the tangent space (T-conjugate points) from conjugate points in the manifold (M-conjugate points). It is shown that most nonspacelike conjugate points are regular, i.e. with all neighbouring conjugate points having the same degree of degeneracy. The regular timelike T-conjugate locus is shown to be a smooth 3-dimensional submanifold of the tangent space. Analogously, the regular null T-conjugate locus is shown to be a smooth 2-dimensional submanifold of the light cone in the tangent space. The smoothness properties of the null caustic are used to show that if an observer sees focusing in all directions, then there will necessarily be a cusp in the caustic. If, in addition, all the null conjugate points have maximal degree of degeneracy (as in the closed Friedmann-Robertson-Walker universes), then the space-time is closed. (orig.)
Applications of asynoptic space - Time Fourier transform methods to scanning satellite measurements
Lait, Leslie R.; Stanford, John L.
1988-01-01
A method proposed by Salby (1982) for computing the zonal space-time Fourier transform of asynoptically acquired satellite data is discussed. The method and its relationship to other techniques are briefly described, and possible problems in applying it to real data are outlined. Examples of results obtained using this technique are given which demonstrate its sensitivity to small-amplitude signals. A number of waves are found which have previously been observed as well as two not heretofore reported. A possible extension of the method which could increase temporal and longitudinal resolution is described.
Infrared behaviour of massless QED in space-time dimensions 2
International Nuclear Information System (INIS)
Mitra, Indrajit; Ratabole, Raghunath; Sharatchandra, H.S.
2005-01-01
We show that the logarithmic infrared divergences in electron self-energy and vertex function of massless QED in 2+1 dimensions can be removed at all orders of 1/N by an appropriate choice of a non-local gauge. Thus the infrared behaviour given by the leading order in 1/N is not modified by higher order corrections. Our analysis gives a computational scheme for the Amati-Testa model, resulting in a non-trivial conformal invariant field theory for all space-time dimensions 2< d<4
Infrared behaviour of massless QED in space-time dimensions 2
Energy Technology Data Exchange (ETDEWEB)
Mitra, Indrajit [The Institute of Mathematical Sciences, C.I.T. Campus, Taramani P.O., Chennai 600113 (India) and Theory Group, Saha Institute of Nuclear Physics, 1/AF Bidhan-Nagar, Kolkata 700064 (India)]. E-mail: indra@theory.saha.ernet.in; Ratabole, Raghunath [The Institute of Mathematical Sciences, C.I.T. Campus, Taramani P.O., Chennai 600113 (India)]. E-mail: raghu@imsc.res.in; Sharatchandra, H.S. [The Institute of Mathematical Sciences, C.I.T. Campus, Taramani P.O., Chennai 600113 (India)]. E-mail: sharat@imsc.res.in
2005-04-07
We show that the logarithmic infrared divergences in electron self-energy and vertex function of massless QED in 2+1 dimensions can be removed at all orders of 1/N by an appropriate choice of a non-local gauge. Thus the infrared behaviour given by the leading order in 1/N is not modified by higher order corrections. Our analysis gives a computational scheme for the Amati-Testa model, resulting in a non-trivial conformal invariant field theory for all space-time dimensions 2
Positivity-preserving space-time CE/SE scheme for high speed flows
Shen, Hua
2017-03-02
We develop a space-time conservation element and solution element (CE/SE) scheme using a simple slope limiter to preserve the positivity of the density and pressure in computations of inviscid and viscous high-speed flows. In general, the limiter works with all existing CE/SE schemes. Here, we test the limiter on a central Courant number insensitive (CNI) CE/SE scheme implemented on hybrid unstructured meshes. Numerical examples show that the proposed limiter preserves the positivity of the density and pressure without disrupting the conservation law; it also improves robustness without losing accuracy in solving high-speed flows.
Positivity-preserving space-time CE/SE scheme for high speed flows
Shen, Hua; Parsani, Matteo
2017-01-01
We develop a space-time conservation element and solution element (CE/SE) scheme using a simple slope limiter to preserve the positivity of the density and pressure in computations of inviscid and viscous high-speed flows. In general, the limiter works with all existing CE/SE schemes. Here, we test the limiter on a central Courant number insensitive (CNI) CE/SE scheme implemented on hybrid unstructured meshes. Numerical examples show that the proposed limiter preserves the positivity of the density and pressure without disrupting the conservation law; it also improves robustness without losing accuracy in solving high-speed flows.
Beghein, Yves
2013-03-01
The time domain combined field integral equation (TD-CFIE), which is constructed from a weighted sum of the time domain electric and magnetic field integral equations (TD-EFIE and TD-MFIE) for analyzing transient scattering from closed perfect electrically conducting bodies, is free from spurious resonances. The standard marching-on-in-time technique for discretizing the TD-CFIE uses Galerkin and collocation schemes in space and time, respectively. Unfortunately, the standard scheme is theoretically not well understood: stability and convergence have been proven for only one class of space-time Galerkin discretizations. Moreover, existing discretization schemes are nonconforming, i.e., the TD-MFIE contribution is tested with divergence conforming functions instead of curl conforming functions. We therefore introduce a novel space-time mixed Galerkin discretization for the TD-CFIE. A family of temporal basis and testing functions with arbitrary order is introduced. It is explained how the corresponding interactions can be computed efficiently by existing collocation-in-time codes. The spatial mixed discretization is made fully conforming and consistent by leveraging both Rao-Wilton-Glisson and Buffa-Christiansen basis functions and by applying the appropriate bi-orthogonalization procedures. The combination of both techniques is essential when high accuracy over a broad frequency band is required. © 2012 IEEE.
Computation On dP Type power System Stabilizer Using Fuzzy Logic
International Nuclear Information System (INIS)
Iskandar, M.A.; Irwan, R.; Husdi; Riza; Mardhana, E.; Triputranto, A.
1997-01-01
Power system stabilizers (PSS) are widely applied in power generators to damp power oscillation caused by certain disturbances in order to increase the power supply capacity. PSS design is often suffered from the difficulty on setting periodically its parameters, which are gain and compensators, in order to have an optimal damping characteristic. This paper proposes a methode to determine parameters of dP type PSS by implementing fuzzy logic rules in a computer program,to obtain the appropriate characteristics of synchronous torque and damping torque. PSS with the calculated parameters is investigated on a simulation using a non-linear electric power system of a thermal generator connected to infinite bus system model. Simulation results show that great improvement in damping characteristic and enhancement of stability margin of electric power system are obtained by using the proposed PSS
Numerical computation of the linear stability of the diffusion model for crystal growth simulation
Energy Technology Data Exchange (ETDEWEB)
Yang, C.; Sorensen, D.C. [Rice Univ., Houston, TX (United States); Meiron, D.I.; Wedeman, B. [California Institute of Technology, Pasadena, CA (United States)
1996-12-31
We consider a computational scheme for determining the linear stability of a diffusion model arising from the simulation of crystal growth. The process of a needle crystal solidifying into some undercooled liquid can be described by the dual diffusion equations with appropriate initial and boundary conditions. Here U{sub t} and U{sub a} denote the temperature of the liquid and solid respectively, and {alpha} represents the thermal diffusivity. At the solid-liquid interface, the motion of the interface denoted by r and the temperature field are related by the conservation relation where n is the unit outward pointing normal to the interface. A basic stationary solution to this free boundary problem can be obtained by writing the equations of motion in a moving frame and transforming the problem to parabolic coordinates. This is known as the Ivantsov parabola solution. Linear stability theory applied to this stationary solution gives rise to an eigenvalue problem of the form.
Abediseid, Walid
2012-12-21
The exact average complexity analysis of the basic sphere decoder for general space-time codes applied to multiple-input multiple-output (MIMO) wireless channel is known to be difficult. In this work, we shed the light on the computational complexity of sphere decoding for the quasi- static, lattice space-time (LAST) coded MIMO channel. Specifically, we drive an upper bound of the tail distribution of the decoder\\'s computational complexity. We show that when the computational complexity exceeds a certain limit, this upper bound becomes dominated by the outage probability achieved by LAST coding and sphere decoding schemes. We then calculate the minimum average computational complexity that is required by the decoder to achieve near optimal performance in terms of the system parameters. Our results indicate that there exists a cut-off rate (multiplexing gain) for which the average complexity remains bounded. Copyright © 2012 John Wiley & Sons, Ltd.
Entanglement, space-time and the Mayer-Vietoris theorem
Patrascu, Andrei T.
2017-06-01
Entanglement appears to be a fundamental building block of quantum gravity leading to new principles underlying the nature of quantum space-time. One such principle is the ER-EPR duality. While supported by our present intuition, a proof is far from obvious. In this article I present a first step towards such a proof, originating in what is known to algebraic topologists as the Mayer-Vietoris theorem. The main result of this work is the re-interpretation of the various morphisms arising when the Mayer-Vietoris theorem is used to assemble a torus-like topology from more basic subspaces on the torus in terms of quantum information theory resulting in a quantum entangler gate (Hadamard and c-NOT).
The standard model on non-commutative space-time
International Nuclear Information System (INIS)
Calmet, X.; Jurco, B.; Schupp, P.; Wohlgenannt, M.; Wess, J.
2002-01-01
We consider the standard model on a non-commutative space and expand the action in the non-commutativity parameter θ μν . No new particles are introduced; the structure group is SU(3) x SU(2) x U(1). We derive the leading order action. At zeroth order the action coincides with the ordinary standard model. At leading order in θ μν we find new vertices which are absent in the standard model on commutative space-time. The most striking features are couplings between quarks, gluons and electroweak bosons and many new vertices in the charged and neutral currents. We find that parity is violated in non-commutative QCD. The Higgs mechanism can be applied. QED is not deformed in the minimal version of the NCSM to the order considered. (orig.)
The standard model on non-commutative space-time
Energy Technology Data Exchange (ETDEWEB)
Calmet, X.; Jurco, B.; Schupp, P.; Wohlgenannt, M. [Sektion Physik, Universitaet Muenchen (Germany); Wess, J. [Sektion Physik, Universitaet Muenchen (Germany); Max-Planck-Institut fuer Physik, Muenchen (Germany)
2002-03-01
We consider the standard model on a non-commutative space and expand the action in the non-commutativity parameter {theta}{sup {mu}}{sup {nu}}. No new particles are introduced; the structure group is SU(3) x SU(2) x U(1). We derive the leading order action. At zeroth order the action coincides with the ordinary standard model. At leading order in {theta}{sup {mu}}{sup {nu}} we find new vertices which are absent in the standard model on commutative space-time. The most striking features are couplings between quarks, gluons and electroweak bosons and many new vertices in the charged and neutral currents. We find that parity is violated in non-commutative QCD. The Higgs mechanism can be applied. QED is not deformed in the minimal version of the NCSM to the order considered. (orig.)
Momentum-subtraction renormalization techniques in curved space-time
Energy Technology Data Exchange (ETDEWEB)
Foda, O.
1987-10-01
Momentum-subtraction techniques, specifically BPHZ and Zimmermann's Normal Product algorithm, are introduced as useful tools in the study of quantum field theories in the presence of background fields. In a model of a self-interacting massive scalar field, conformally coupled to a general asymptotically-flat curved space-time with a trivial topology, momentum-subtractions are shown to respect invariance under general coordinate transformations. As an illustration, general expressions for the trace anomalies are derived, and checked by explicit evaluation of the purely gravitational contributions in the free field theory limit. Furthermore, the trace of the renormalized energy-momentum tensor is shown to vanish at the Gell-Mann Low eigenvalue as it should.
Momentum-subtraction renormalization techniques in curved space-time
International Nuclear Information System (INIS)
Foda, O.
1987-01-01
Momentum-subtraction techniques, specifically BPHZ and Zimmermann's Normal Product algorithm, are introduced as useful tools in the study of quantum field theories in the presence of background fields. In a model of a self-interacting massive scalar field, conformally coupled to a general asymptotically-flat curved space-time with a trivial topology, momentum-subtractions are shown to respect invariance under general coordinate transformations. As an illustration, general expressions for the trace anomalies are derived, and checked by explicit evaluation of the purely gravitational contributions in the free field theory limit. Furthermore, the trace of the renormalized energy-momentum tensor is shown to vanish at the Gell-Mann Low eigenvalue as it should
Relativity for everyone how space-time bends
Fischer, Kurt
2013-01-01
This book explains the theory of special and general relativity in detail, without digressions such as information on Einstein's life or the historical background. However, complicated calculations are replaced with figures and thought experiments, the text being formulated in such a way that the reader will be able to understand the gist intuitively. The first part of the book focuses on the essentials of special relativity. Explanations are provided of the famous equivalence between mass and energy and of why Einstein was able to use the theory of electrodynamics as a template for his "electrodynamics of moving bodies", simply because besides the speed of light, the electric charge itself is also absolute, leading to the relativity of other physical quantities. General relativity is then introduced, mainly with the help of thought experiments. Reference is made to the previously introduced special relativity and the equivalence principle and, using many figures, it is explained how space-time is bending und...
Space, time and the limits of human understanding
Ghirardi, Giancarlo
2017-01-01
In this compendium of essays, some of the world’s leading thinkers discuss their conceptions of space and time, as viewed through the lens of their own discipline. With an epilogue on the limits of human understanding, this volume hosts contributions from six or more diverse fields. It presumes only rudimentary background knowledge on the part of the reader. Time and again, through the prism of intellect, humans have tried to diffract reality into various distinct, yet seamless, atomic, yet holistic, independent, yet interrelated disciplines and have attempted to study it contextually. Philosophers debate the paradoxes, or engage in meditations, dialogues and reflections on the content and nature of space and time. Physicists, too, have been trying to mold space and time to fit their notions concerning micro- and macro-worlds. Mathematicians focus on the abstract aspects of space, time and measurement. While cognitive scientists ponder over the perceptual and experiential facets of our consciousness of spac...
Einstein's dream : the space-time unification of fundamental forces
Energy Technology Data Exchange (ETDEWEB)
Salam, A [International Centre for Theoretical Physics, Trieste (Italy)
1981-06-01
The historical developments in physics which started with Galileo in the 11th century, Newton in the 17 century, culminated in the unification of space-time by Einstein in this century are traced. The theories put forward by Einstein himself and by subsequent workers in the field after him, regarding the unification of all basic forces of nature (i.e.) the electromagnetic and the gravitational ones and the weak and strong nuclear forces are discussed. The experiments being conducted in Kolar and other places to detect a heavier photon which would be a positive proof of the validity of the unification theory, are touched upon. The possible application of this concept even in industry has been pointed out.
Space-time foam as the universal regulator
International Nuclear Information System (INIS)
Crane, L.; Smolin, L.
1985-01-01
A distribution of virtual black holes in the vacuum will induce modifications in the density of states for small perturbations of gravitational and matter fields. If the virtual black holes fill the volume of a typical spacelike surface then perturbation theory becomes more convergent and may even be finite, depending on how fast the number of virtual black holes increases as their size decreases. For distributions of virtual black holes which are scale invariant the effective dimension of space-time is lowered to a noninteger value less than 4, leading to an interpretation in terms of fractal geometry. In this case general relativity is renormalizable in the 1/N expansion without higher derivative terms. As the Hamiltonian is not modified the theory is stable. (author)
Point splitting in a curved space-time background
International Nuclear Information System (INIS)
Liggatt, P.A.J.; Macfarlane, A.J.
1979-01-01
A prescription is given for point splitting in a curved space-time background which is a natural generalization of that familiar in quantum electrodynamics and Yang-Mills theory. It is applied (to establish its validity) to the verification of the gravitational anomaly in the divergence of a fermion axial current. Notable features of the prescription are that it defines a point-split current that can be differentiated straightforwardly, and that it involves a natural way of averaging (four-dimensionally) over the directions of point splitting. The method can extend directly from the spin-1/2 fermion case treated to other cases, e.g., to spin-3/2 Rarita-Schwinger fermions. (author)
Topological properties and global structure of space-time
International Nuclear Information System (INIS)
Bergmann, P.G.; De Sabbata, V.
1986-01-01
This book presents information on the following topics: measurement of gravity and gauge fields using quantum mechanical probes; gravitation at spatial infinity; field theories on supermanifolds; supergravities and Kaluza-Klein theories; boundary conditions at spatial infinity; singularities - global and local aspects; matter at the horizon of the Schwarzschild black hole; introluction to string theories; cosmic censorship and the strengths of singularities; conformal quantisation in singular spacetimes; solar system tests in transition; integration and global aspects of supermanifolds; the space-time of the bimetric general relativity theory; gravitation without Lorentz invariance; a uniform static magnetic field in Kaluza-Klein theory; introduction to topological geons; and a simple model of a non-asymptotically flat Schwarzschild black hole
Quantum vacuum energy in two dimensional space-times
International Nuclear Information System (INIS)
Davies, P.C.W.; Fulling, S.A.
1977-01-01
The paper presents in detail the renormalization theory of the energy-momentum tensor of a two dimensional massless scalar field which has been used elsewhere to study the local physics in a model of black hole evaporation. The treatment is generalized to include the Casimir effect occurring in spatially finite models. The essence of the method is evaluation of the field products in the tensor as functions of two points, followed by covariant subtraction of the discontinuous terms arising as the points coalesce. In two dimensional massless theories, conformal transformations permit exact calculations to be performed. The results are applied here to some special cases, primarily space-times of constant curvature, with emphasis on the existence of distinct 'vacuum' states associated naturally with different conformal coordinate systems. The relevance of the work to the general problems of defining observables and of classifying and interpreting states in curved-space quantum field theory is discussed. (author)
Exactly solvable string models of curved space-time backgrounds
Russo, J.G.; Russo, J G; Tseytlin, A A
1995-01-01
We consider a new 3-parameter class of exact 4-dimensional solutions in closed string theory and solve the corresponding string model, determining the physical spectrum and the partition function. The background fields (4-metric, antisymmetric tensor, two Kaluza-Klein vector fields, dilaton and modulus) generically describe axially symmetric stationary rotating (electro)magnetic flux-tube type universes. Backgrounds of this class include both the dilatonic Melvin solution and the uniform magnetic field solution discussed earlier as well as some singular space-times. Solvability of the string sigma model is related to its connection via duality to a much simpler looking model which is a "twisted" product of a flat 2-space and a space dual to 2-plane. We discuss some physical properties of this model as well as a number of generalizations leading to larger classes of exact 4-dimensional string solutions.
Virtual Black Holes and Space-Time Structure
't Hooft, Gerard
2018-01-01
In the standard formalism of quantum gravity, black holes appear to form statistical distributions of quantum states. Now, however, we can present a theory that yields pure quantum states. It shows how particles entering a black hole can generate firewalls, which however can be removed, replacing them by the `footprints' they produce in the out-going particles. This procedure can preserve the quantum information stored inside and around the black hole. We then focus on a subtle but unavoidable modification of the topology of the Schwarzschild metric: antipodal identification of points on the horizon. If it is true that vacuum fluctuations include virtual black holes, then the structure of space-time is radically different from what is usually thought.
Transient space-time surface waves characterization using Gabor analysis
Energy Technology Data Exchange (ETDEWEB)
Martinez, L; Wilkie-Chancellier, N; Caplain, E [Universite de Cergy Pontoise, ENS Cachan, UMR CNRS 8029, Laboratoire Systemes et Applications des Techniques de l' Information et de l' Energie (SATIE), 5 mail Gay-Lussac, F 9500 Cergy-Pontoise (France); Glorieux, C; Sarens, B, E-mail: nicolas.wilkie-chancellier@u-cergy.f [Katholieke Universiteit Leuven, Laboratorium voor Akoestiek en Thermische Fysica (LATF), Celestijnenlaan 200D, B-3001 Leuven (Belgium)
2009-11-01
Laser ultrasonics allow the observation of transient surface waves along their propagation media and their interaction with encountered objects like cracks, holes, borders. In order to characterize and localize these transient aspects in the Space-Time-Wave number-Frequency domains, the 1D, 2D and 3D Gabor transforms are presented. The Gabor transform enables the identification of several properties of the local wavefronts such as their shape, wavelength, frequency, attenuation, group velocity and the full conversion sequence along propagation. The ability of local properties identification by Gabor transform is illustrated by two experimental studies: Lamb waves generated by an annular source on a circular quartz and Lamb wave interaction with a fluid droplet. In both cases, results obtained with Gabor transform enable ones to identify the observed local waves.
Entropic force, holography and thermodynamics for static space-times
International Nuclear Information System (INIS)
Konoplya, R.A.
2010-01-01
Recently Verlinde has suggested a new approach to gravity which interprets gravitational interaction as a kind of entropic force. The new approach uses the holographic principle by stating that the information is kept on the holographic screens which coincide with equipotential surfaces. Motivated by this new interpretation of gravity (but not being limited by it) we study equipotential surfaces, the Unruh-Verlinde temperature, energy and acceleration for various static space-times: generic spherically symmetric solutions, axially symmetric black holes immersed in a magnetic field, traversable spherically symmetric wormholes of an arbitrary shape function, system of two and more extremely charged black holes in equilibrium. In particular, we have shown that the Unruh-Verlinde temperature of the holographic screen reaches absolute zero on the wormhole throat independently of the particular form of the wormhole solution. (orig.)
Fermions in odd space-time dimensions: back to basics
International Nuclear Information System (INIS)
Anguiano Jesus de, Ma.; Bashir, A.
2005-01-01
It is a well-known feature of odd space-time dimensions d that there exist two inequivalent fundamental representations A and B of the Dirac gamma matrices. Moreover, the parity transformation swaps the fermion fields living in A and B. As a consequence, a parity-invariant Lagrangian can only be constructed by incorporating both the representation. Based upon these ideas and contrary to long-held belief, we show that in addition to a discrete exchange symmetry for the massless case, we can also define chiral symmetry provided the Lagrangian contains fields corresponding to both the inequivalent representations. We also study the transformation properties of the corresponding chiral currents under parity and charge-conjugation operations. We work explicitly in 2 + 1 dimensions and later show how some of these ideas generalize to an arbitrary number of odd dimensions. (author)
Quantum vacuum energy in two dimensional space-times
Energy Technology Data Exchange (ETDEWEB)
Davies, P C.W.; Fulling, S A [King' s Coll., London (UK). Dept. of Mathematics
1977-04-21
The paper presents in detail the renormalization theory of the energy-momentum tensor of a two dimensional massless scalar field which has been used elsewhere to study the local physics in a model of black hole evaporation. The treatment is generalized to include the Casimir effect occurring in spatially finite models. The essence of the method is evaluation of the field products in the tensor as functions of two points, followed by covariant subtraction of the discontinuous terms arising as the points coalesce. In two dimensional massless theories, conformal transformations permit exact calculations to be performed. The results are applied here to some special cases, primarily space-times of constant curvature, with emphasis on the existence of distinct 'vacuum' states associated naturally with different conformal coordinate systems. The relevance of the work to the general problems of defining observables and of classifying and interpreting states in curved-space quantum field theory is discussed.
Quantum field theory on discrete space-time. II
International Nuclear Information System (INIS)
Yamamoto, H.
1985-01-01
A quantum field theory of bosons and fermions is formulated on discrete Lorentz space-time of four dimensions. The minimum intervals of space and time are assumed to have different values in this paper. As a result the difficulties encountered in the previous paper (complex energy, incompleteness of solutions, and inequivalence between phase representation and momentum representation) are removed. The problem in formulating a field theory of fermions is solved by introducing a new operator and considering a theorem of translation invariance. Any matrix element given by a Feynman diagram is calculated in this theory to give a finite value regardless of the kinds of particles concerned (massive and/or massless bosons and/or fermions)
Directory of Open Access Journals (Sweden)
Jianguo Ren
2014-01-01
Full Text Available A new computer virus propagation model with delay and incomplete antivirus ability is formulated and its global dynamics is analyzed. The existence and stability of the equilibria are investigated by resorting to the threshold value R0. By analysis, it is found that the model may undergo a Hopf bifurcation induced by the delay. Correspondingly, the critical value of the Hopf bifurcation is obtained. Using Lyapunov functional approach, it is proved that, under suitable conditions, the unique virus-free equilibrium is globally asymptotically stable if R01. Numerical examples are presented to illustrate possible behavioral scenarios of the mode.
Quantum universe on extremely small space-time scales
International Nuclear Information System (INIS)
Kuzmichev, V.E.; Kuzmichev, V.V.
2010-01-01
The semiclassical approach to the quantum geometrodynamical model is used for the description of the properties of the Universe on extremely small space-time scales. Under this approach, the matter in the Universe has two components of the quantum nature which behave as antigravitating fluids. The first component does not vanish in the limit h → 0 and can be associated with dark energy. The second component is described by an extremely rigid equation of state and goes to zero after the transition to large spacetime scales. On small space-time scales, this quantum correction turns out to be significant. It determines the geometry of the Universe near the initial cosmological singularity point. This geometry is conformal to a unit four-sphere embedded in a five-dimensional Euclidean flat space. During the consequent expansion of the Universe, when reaching the post-Planck era, the geometry of the Universe changes into that conformal to a unit four-hyperboloid in a five-dimensional Lorentzsignatured flat space. This agrees with the hypothesis about the possible change of geometry after the origin of the expanding Universe from the region near the initial singularity point. The origin of the Universe can be interpreted as a quantum transition of the system from a region in the phase space forbidden for the classical motion, but where a trajectory in imaginary time exists, into a region, where the equations of motion have the solution which describes the evolution of the Universe in real time. Near the boundary between two regions, from the side of real time, the Universe undergoes almost an exponential expansion which passes smoothly into the expansion under the action of radiation dominating over matter which is described by the standard cosmological model.
Study of the stability of a SEIRS model for computer worm propagation
Hernández Guillén, J. D.; Martín del Rey, A.; Hernández Encinas, L.
2017-08-01
Nowadays, malware is the most important threat to information security. In this sense, several mathematical models to simulate malware spreading have appeared. They are compartmental models where the population of devices is classified into different compartments: susceptible, exposed, infectious, recovered, etc. The main goal of this work is to propose an improved SEIRS (Susceptible-Exposed-Infectious-Recovered-Susceptible) mathematical model to simulate computer worm propagation. It is a continuous model whose dynamic is ruled by means of a system of ordinary differential equations. It considers more realistic parameters related to the propagation; in fact, a modified incidence rate has been used. Moreover, the equilibrium points are computed and their local and global stability analyses are studied. From the explicit expression of the basic reproductive number, efficient control measures are also obtained.
Variance stabilization for computing and comparing grand mean waveforms in MEG and EEG.
Matysiak, Artur; Kordecki, Wojciech; Sielużycki, Cezary; Zacharias, Norman; Heil, Peter; König, Reinhard
2013-07-01
Grand means of time-varying signals (waveforms) across subjects in magnetoencephalography (MEG) and electroencephalography (EEG) are commonly computed as arithmetic averages and compared between conditions, for example, by subtraction. However, the prerequisite for these operations, homogeneity of the variance of the waveforms in time, and for most common parametric statistical tests also between conditions, is rarely met. We suggest that the heteroscedasticity observed instead results because waveforms may differ by factors and additive terms and follow a mixed model. We propose to apply the asinh-transformation to stabilize the variance in such cases. We demonstrate the homogeneous variance and the normal distributions of data achieved by this transformation using simulated waveforms, and we apply it to real MEG data and show its benefits. The asinh-transformation is thus an essential and useful processing step prior to computing and comparing grand mean waveforms in MEG and EEG. Copyright © 2013 Society for Psychophysiological Research.
Directory of Open Access Journals (Sweden)
Heng-Yi Su
2016-11-01
Full Text Available This paper proposes an efficient approach for the computation of voltage stability margin (VSM in a large-scale power grid. The objective is to accurately and rapidly determine the load power margin which corresponds to voltage collapse phenomena. The proposed approach is based on the impedance match-based technique and the model-based technique. It combines the Thevenin equivalent (TE network method with cubic spline extrapolation technique and the continuation technique to achieve fast and accurate VSM computation for a bulk power grid. Moreover, the generator Q limits are taken into account for practical applications. Extensive case studies carried out on Institute of Electrical and Electronics Engineers (IEEE benchmark systems and the Taiwan Power Company (Taipower, Taipei, Taiwan system are used to demonstrate the effectiveness of the proposed approach.
Numerical relativity for D dimensional axially symmetric space-times: Formalism and code tests
International Nuclear Information System (INIS)
Zilhao, Miguel; Herdeiro, Carlos; Witek, Helvi; Nerozzi, Andrea; Sperhake, Ulrich; Cardoso, Vitor; Gualtieri, Leonardo
2010-01-01
The numerical evolution of Einstein's field equations in a generic background has the potential to answer a variety of important questions in physics: from applications to the gauge-gravity duality, to modeling black hole production in TeV gravity scenarios, to analysis of the stability of exact solutions, and to tests of cosmic censorship. In order to investigate these questions, we extend numerical relativity to more general space-times than those investigated hitherto, by developing a framework to study the numerical evolution of D dimensional vacuum space-times with an SO(D-2) isometry group for D≥5, or SO(D-3) for D≥6. Performing a dimensional reduction on a (D-4) sphere, the D dimensional vacuum Einstein equations are rewritten as a 3+1 dimensional system with source terms, and presented in the Baumgarte, Shapiro, Shibata, and Nakamura formulation. This allows the use of existing 3+1 dimensional numerical codes with small adaptations. Brill-Lindquist initial data are constructed in D dimensions and a procedure to match them to our 3+1 dimensional evolution equations is given. We have implemented our framework by adapting the Lean code and perform a variety of simulations of nonspinning black hole space-times. Specifically, we present a modified moving puncture gauge, which facilitates long-term stable simulations in D=5. We further demonstrate the internal consistency of the code by studying convergence and comparing numerical versus analytic results in the case of geodesic slicing for D=5, 6.
Study of spontaneously broken conformal symmetry in curved space-times
International Nuclear Information System (INIS)
Janson, M.M.
1977-05-01
Spontaneous breakdown of Weyl invariance (local scale invariance) in a conformally-invariant extension of a gauge model for weak and electromagnetic interactions is considered. The existence of an asymmetric vacuum for the Higgs field, phi, is seen to depend on the space-time structure via the Gursey-Penrose term, approximately phi + phi R, in the action. (R denotes the scalar curvature.) The effects of a prescribed space-time structure on spontaneously broken Weyl invariance is investigated. In a cosmological space-time, it is found that initially, in the primordial fireball, the symmetry must hold exactly. Spontaneous symmetry breaking (SSB) develops as the universe expands and cools. Consequences of this model include a dependence of G/sub F/, the effective weak interaction coupling strength, on ''cosmic time.'' It is seen to decrease monotonically; in the present epoch (G/sub F//G/sub F/)/sub TODAY/ approximately less than 10 -10 (year) -1 . The effects of the Schwarzschild geometry on SSB are explored. In the interior of a neutron star the Higgs vacuum expectation value, and consequently G/sub F/, is found to have a radial dependence. The magnitude of this variation does not warrant revision of present models of neutron star structures. Another perspective on the problem considered a theory of gravitation (conformal relativity) to be incorporated in the conformally invariant gauge model of weak and electromagnetic interactions. If SSB develops, the vacuum gravitational field equations are the Einstein field equations with a cosmological constant. The stability of the asymmetric vacuum solution is investigated to ascertain whether SSB can occur
Modeling Space-Time Dependent Helium Bubble Evolution in Tungsten Armor under IFE Conditions
International Nuclear Information System (INIS)
Qiyang Hu; Shahram Sharafat; Nasr Ghoniem
2006-01-01
The High Average Power Laser (HAPL) program is a coordinated effort to develop Laser Inertial Fusion Energy. The implosion of the D-T target produces a spectrum of neutrons, X-rays, and charged particles, which arrive at the first wall (FW) at different times within about 2.5 μs at a frequency of 5 to 10 Hz. Helium is one of several high-energy charged particle constituents impinging on the candidate tungsten armored low activation ferritic steel First Wall. The spread of the implanted debris and burn helium energies results in a unique space-time dependent implantation profile that spans about 10 μm in tungsten. Co-implantation of X-rays and other ions results in spatially dependent damage profiles and rapid space-time dependent temperature spikes and gradients. The rate of helium transport and helium bubble formation will vary significantly throughout the implanted region. Furthermore, helium will also be transported via the migration of helium bubbles and non-equilibrium helium-vacancy clusters. The HEROS code was developed at UCLA to model the spatial and time-dependent helium bubble nucleation, growth, coalescence, and migration under transient damage rates and transient temperature gradients. The HEROS code is based on kinetic rate theory, which includes clustering of helium and vacancies, helium mobility, helium-vacancy cluster stability, cavity nucleation and growth and other microstructural features such as interstitial loop evolution, grain boundaries, and precipitates. The HEROS code is based on space-time discretization of reaction-diffusion type equations to account for migration of mobile species between neighboring bins as single atoms, clusters, or bubbles. HAPL chamber FW implantation conditions are used to model helium bubble evolution in the implanted tungsten. Helium recycling rate predictions are compared with experimental results of helium ion implantation experiments. (author)
Is the local linearity of space-time inherited from the linearity of probabilities?
Müller, Markus P.; Carrozza, Sylvain; Höhn, Philipp A.
2017-02-01
The appearance of linear spaces, describing physical quantities by vectors and tensors, is ubiquitous in all of physics, from classical mechanics to the modern notion of local Lorentz invariance. However, as natural as this seems to the physicist, most computer scientists would argue that something like a ‘local linear tangent space’ is not very typical and in fact a quite surprising property of any conceivable world or algorithm. In this paper, we take the perspective of the computer scientist seriously, and ask whether there could be any inherently information-theoretic reason to expect this notion of linearity to appear in physics. We give a series of simple arguments, spanning quantum information theory, group representation theory, and renormalization in quantum gravity, that supports a surprising thesis: namely, that the local linearity of space-time might ultimately be a consequence of the linearity of probabilities. While our arguments involve a fair amount of speculation, they have the virtue of being independent of any detailed assumptions on quantum gravity, and they are in harmony with several independent recent ideas on emergent space-time in high-energy physics.
Fitted Hanbury-Brown Twiss radii versus space-time variances in flow-dominated models
Frodermann, Evan; Heinz, Ulrich; Lisa, Michael Annan
2006-04-01
The inability of otherwise successful dynamical models to reproduce the Hanbury-Brown Twiss (HBT) radii extracted from two-particle correlations measured at the Relativistic Heavy Ion Collider (RHIC) is known as the RHIC HBT Puzzle. Most comparisons between models and experiment exploit the fact that for Gaussian sources the HBT radii agree with certain combinations of the space-time widths of the source that can be directly computed from the emission function without having to evaluate, at significant expense, the two-particle correlation function. We here study the validity of this approach for realistic emission function models, some of which exhibit significant deviations from simple Gaussian behavior. By Fourier transforming the emission function, we compute the two-particle correlation function, and fit it with a Gaussian to partially mimic the procedure used for measured correlation functions. We describe a novel algorithm to perform this Gaussian fit analytically. We find that for realistic hydrodynamic models the HBT radii extracted from this procedure agree better with the data than the values previously extracted from the space-time widths of the emission function. Although serious discrepancies between the calculated and the measured HBT radii remain, we show that a more apples-to-apples comparison of models with data can play an important role in any eventually successful theoretical description of RHIC HBT data.
Fitted Hanbury-Brown-Twiss radii versus space-time variances in flow-dominated models
International Nuclear Information System (INIS)
Frodermann, Evan; Heinz, Ulrich; Lisa, Michael Annan
2006-01-01
The inability of otherwise successful dynamical models to reproduce the Hanbury-Brown-Twiss (HBT) radii extracted from two-particle correlations measured at the Relativistic Heavy Ion Collider (RHIC) is known as the RHIC HBT Puzzle. Most comparisons between models and experiment exploit the fact that for Gaussian sources the HBT radii agree with certain combinations of the space-time widths of the source that can be directly computed from the emission function without having to evaluate, at significant expense, the two-particle correlation function. We here study the validity of this approach for realistic emission function models, some of which exhibit significant deviations from simple Gaussian behavior. By Fourier transforming the emission function, we compute the two-particle correlation function, and fit it with a Gaussian to partially mimic the procedure used for measured correlation functions. We describe a novel algorithm to perform this Gaussian fit analytically. We find that for realistic hydrodynamic models the HBT radii extracted from this procedure agree better with the data than the values previously extracted from the space-time widths of the emission function. Although serious discrepancies between the calculated and the measured HBT radii remain, we show that a more apples-to-apples comparison of models with data can play an important role in any eventually successful theoretical description of RHIC HBT data
Fitted HBT radii versus space-time variances in flow-dominated models
International Nuclear Information System (INIS)
Lisa, Mike; Frodermann, Evan; Heinz, Ulrich
2007-01-01
The inability of otherwise successful dynamical models to reproduce the 'HBT radii' extracted from two-particle correlations measured at the Relativistic Heavy Ion Collider (RHIC) is known as the 'RHIC HBT Puzzle'. Most comparisons between models and experiment exploit the fact that for Gaussian sources the HBT radii agree with certain combinations of the space-time widths of the source which can be directly computed from the emission function, without having to evaluate, at significant expense, the two-particle correlation function. We here study the validity of this approach for realistic emission function models some of which exhibit significant deviations from simple Gaussian behaviour. By Fourier transforming the emission function we compute the 2-particle correlation function and fit it with a Gaussian to partially mimic the procedure used for measured correlation functions. We describe a novel algorithm to perform this Gaussian fit analytically. We find that for realistic hydrodynamic models the HBT radii extracted from this procedure agree better with the data than the values previously extracted from the space-time widths of the emission function. Although serious discrepancies between the calculated and measured HBT radii remain, we show that a more 'apples-to-apples' comparison of models with data can play an important role in any eventually successful theoretical description of RHIC HBT data. (author)
A Space-Time Signal Decomposition Algorithm for Downlink MIMO DS-CDMA Receivers
Wang, Yung-Yi; Fang, Wen-Hsien; Chen, Jiunn-Tsair
We propose a dimension reduction algorithm for the receiver of the downlink of direct-sequence code-division multiple access (DS-CDMA) systems in which both the transmitters and the receivers employ antenna arrays of multiple elements. To estimate the high order channel parameters, we develop a layered architecture using dimension-reduced parameter estimation algorithms to estimate the frequency-selective multipath channels. In the proposed architecture, to exploit the space-time geometric characteristics of multipath channels, spatial beamformers and constrained (or unconstrained) temporal filters are adopted for clustered-multipath grouping and path isolation. In conjunction with the multiple access interference (MAI) suppression techniques, the proposed architecture jointly estimates the direction of arrivals, propagation delays, and fading amplitudes of the downlink fading multipaths. With the outputs of the proposed architecture, the signals of interest can then be naturally detected by using path-wise maximum ratio combining. Compared to the traditional techniques, such as the Joint-Angle-and-Delay-Estimation (JADE) algorithm for DOA-delay joint estimation and the space-time minimum mean square error (ST-MMSE) algorithm for signal detection, computer simulations show that the proposed algorithm substantially mitigate the computational complexity at the expense of only slight performance degradation.
Is the local linearity of space-time inherited from the linearity of probabilities?
International Nuclear Information System (INIS)
Müller, Markus P; Carrozza, Sylvain; Höhn, Philipp A
2017-01-01
The appearance of linear spaces, describing physical quantities by vectors and tensors, is ubiquitous in all of physics, from classical mechanics to the modern notion of local Lorentz invariance. However, as natural as this seems to the physicist, most computer scientists would argue that something like a ‘local linear tangent space’ is not very typical and in fact a quite surprising property of any conceivable world or algorithm. In this paper, we take the perspective of the computer scientist seriously, and ask whether there could be any inherently information-theoretic reason to expect this notion of linearity to appear in physics. We give a series of simple arguments, spanning quantum information theory, group representation theory, and renormalization in quantum gravity, that supports a surprising thesis: namely, that the local linearity of space-time might ultimately be a consequence of the linearity of probabilities. While our arguments involve a fair amount of speculation, they have the virtue of being independent of any detailed assumptions on quantum gravity, and they are in harmony with several independent recent ideas on emergent space-time in high-energy physics. (paper)
Quantum mechanics in curved space-time and its consequences for the theory on the flat space-time
International Nuclear Information System (INIS)
Tagirov, E.A.
1997-01-01
Thus, the structure is extracted from the initial general-relativistic setting of the quantum theory of the scalar field φ that can be considered as quantum mechanics in V 1,3 in the Schroedinger picture, which includes relativistic corrections not only in the Hamiltonian of the Schroedinger equation but also in the operators of primary observables. In the terms pertaining to these corrections the operators differ from their counterparts resulting from quantization of a classical spinless particle. In general, they do not commute at all and thus the quantum phase space loses the feature that half its coordinates retain a manifold structure, which Biedenharn called 'a miracle of quantization'. This non-commutativity expands up to the exact (in the sense 'non-asymptotic in c -2 ') quantum mechanics of a free motion in the Minkowski space-time if curvilinear coordinates are taken as observables, which are necessary if non-inertial frames of references are considered
Computer Simulation Study of the Stability Mechanism of Thermophile, MJ0305
Song, Hyundeok; Beck, Thomas
2011-04-01
Methanococcus jannaschii (MJ) is a methane-producing thermophile, which was discovered in a 2600m-deep Pacific Ocean vent in 1983. It has the ability to thrive at high temperatures and high pressures, which are unfavorable for most life forms. There have been some experiments to study its stability under extreme conditions, but still the origin of the stability of MJ is not exactly known. MJ0305 is MJ's chloride channel protein. The structure of MJ0305 was built by homology modeling. We compared the stability of MJ0305 with mesophilic Ecoli at 300K, 330K, and 360K by computer simulation to test the effects of temperature. Our results show that high temperatures significantly affect the number of salt bridges and hydrogen bonds. High temperatures decreased the average number of hydrogen bonds for Ecoli and MJ0305. Increased salt bridges at 330K make MJ0305 more stable. Network analysis of MJ0305 showed an increase in the number of hubs at high temperatures. In contrast, the number of hubs of Ecoli was decreased at high temperatures. Calculated network entropy is proportional to the number of hubs. Increased network entropy of MJ0305 at 330K implies increased robustness.
On fully three-dimensional resistive wall mode and feedback stabilization computations
International Nuclear Information System (INIS)
Strumberger, E.; Merkel, P.; Sempf, M.; Guenter, S.
2008-01-01
Resistive walls, located close to the plasma boundary, reduce the growth rates of external kink modes to resistive time scales. For such slowly growing resistive wall modes, the stabilization by an active feedback system becomes feasible. The fully three-dimensional stability code STARWALL, and the feedback optimization code OPTIM have been developed [P. Merkel and M. Sempf, 21st IAEA Fusion Energy Conference 2006, Chengdu, China (International Atomic Energy Agency, Vienna, 2006, paper TH/P3-8] to compute the growth rates of resistive wall modes in the presence of nonaxisymmetric, multiply connected wall structures and to model the active feedback stabilization of these modes. In order to demonstrate the capabilities of the codes and to study the effect of the toroidal mode coupling caused by multiply connected wall structures, the codes are applied to test equilibria using the resistive wall structures currently under debate for ITER [M. Shimada et al., Nucl. Fusion 47, S1 (2007)] and ASDEX Upgrade [W. Koeppendoerfer et al., Proceedings of the 16th Symposium on Fusion Technology, London, 1990 (Elsevier, Amsterdam, 1991), Vol. 1, p. 208
International Nuclear Information System (INIS)
Raza, K.S.M.
2004-01-01
This paper demonstrates that if a complicated nonlinear, non-square, state-coupled multi variable system is smartly linearized and subjected to a thorough stability analysis then we can achieve our design objectives via a controller which will be quite simple (in term of resource usage and execution time) and very efficient (in terms of robustness). Further the aim is to implement this controller via computer in a real time environment. Therefore first a nonlinear mathematical model of the system is achieved. An intelligent work is done to decouple the multivariable system. Linearization and stability analysis techniques are employed for the development of a linearized and mathematically sound control law. Nonlinearities like the saturation in actuators are also been catered. The controller is then discretized using Runge-Kutta integration. Finally the discretized control law is programmed in a computer in a real time environment. The programme is done in RT -Linux using GNU C for the real time realization of the control scheme. The real time processes, like sampling and controlled actuation, and the non real time processes, like graphical user interface and display, are programmed as different tasks. The issue of inter process communication, between real time and non real time task is addressed quite carefully. The results of this research pursuit are presented graphically. (author)
International Nuclear Information System (INIS)
Lovejoy, S.; Lima, M. I. P. de
2015-01-01
Over the range of time scales from about 10 days to 30–100 years, in addition to the familiar weather and climate regimes, there is an intermediate “macroweather” regime characterized by negative temporal fluctuation exponents: implying that fluctuations tend to cancel each other out so that averages tend to converge. We show theoretically and numerically that macroweather precipitation can be modeled by a stochastic weather-climate model (the Climate Extended Fractionally Integrated Flux, model, CEFIF) first proposed for macroweather temperatures and we show numerically that a four parameter space-time CEFIF model can approximately reproduce eight or so empirical space-time exponents. In spite of this success, CEFIF is theoretically and numerically difficult to manage. We therefore propose a simplified stochastic model in which the temporal behavior is modeled as a fractional Gaussian noise but the spatial behaviour as a multifractal (climate) cascade: a spatial extension of the recently introduced ScaLIng Macroweather Model, SLIMM. Both the CEFIF and this spatial SLIMM model have a property often implicitly assumed by climatologists that climate statistics can be “homogenized” by normalizing them with the standard deviation of the anomalies. Physically, it means that the spatial macroweather variability corresponds to different climate zones that multiplicatively modulate the local, temporal statistics. This simplified macroweather model provides a framework for macroweather forecasting that exploits the system's long range memory and spatial correlations; for it, the forecasting problem has been solved. We test this factorization property and the model with the help of three centennial, global scale precipitation products that we analyze jointly in space and in time
Exploring space-time structure of human mobility in urban space
Sun, J. B.; Yuan, J.; Wang, Y.; Si, H. B.; Shan, X. M.
2011-03-01
Understanding of human mobility in urban space benefits the planning and provision of municipal facilities and services. Due to the high penetration of cell phones, mobile cellular networks provide information for urban dynamics with a large spatial extent and continuous temporal coverage in comparison with traditional approaches. The original data investigated in this paper were collected by cellular networks in a southern city of China, recording the population distribution by dividing the city into thousands of pixels. The space-time structure of urban dynamics is explored by applying Principal Component Analysis (PCA) to the original data, from temporal and spatial perspectives between which there is a dual relation. Based on the results of the analysis, we have discovered four underlying rules of urban dynamics: low intrinsic dimensionality, three categories of common patterns, dominance of periodic trends, and temporal stability. It implies that the space-time structure can be captured well by remarkably few temporal or spatial predictable periodic patterns, and the structure unearthed by PCA evolves stably over time. All these features play a critical role in the applications of forecasting and anomaly detection.
Zanotti, Olindo; Dumbser, Michael
2016-01-01
We present a new version of conservative ADER-WENO finite volume schemes, in which both the high order spatial reconstruction as well as the time evolution of the reconstruction polynomials in the local space-time predictor stage are performed in primitive variables, rather than in conserved ones. To obtain a conservative method, the underlying finite volume scheme is still written in terms of the cell averages of the conserved quantities. Therefore, our new approach performs the spatial WENO reconstruction twice: the first WENO reconstruction is carried out on the known cell averages of the conservative variables. The WENO polynomials are then used at the cell centers to compute point values of the conserved variables, which are subsequently converted into point values of the primitive variables. This is the only place where the conversion from conservative to primitive variables is needed in the new scheme. Then, a second WENO reconstruction is performed on the point values of the primitive variables to obtain piecewise high order reconstruction polynomials of the primitive variables. The reconstruction polynomials are subsequently evolved in time with a novel space-time finite element predictor that is directly applied to the governing PDE written in primitive form. The resulting space-time polynomials of the primitive variables can then be directly used as input for the numerical fluxes at the cell boundaries in the underlying conservative finite volume scheme. Hence, the number of necessary conversions from the conserved to the primitive variables is reduced to just one single conversion at each cell center. We have verified the validity of the new approach over a wide range of hyperbolic systems, including the classical Euler equations of gas dynamics, the special relativistic hydrodynamics (RHD) and ideal magnetohydrodynamics (RMHD) equations, as well as the Baer-Nunziato model for compressible two-phase flows. In all cases we have noticed that the new ADER
A computational framework for investigating the positional stability of aortic endografts.
Prasad, Anamika; Xiao, Nan; Gong, Xiao-Yan; Zarins, Christopher K; Figueroa, C Alberto
2013-10-01
Endovascular aneurysm repair (Greenhalgh in N Engl J Med 362(20):1863-1871, 2010) techniques have revolutionized the treatment of thoracic and abdominal aortic aneurysm disease, greatly reducing the perioperative mortality and morbidity associated with open surgical repair techniques. However, EVAR is not free of important complications such as late device migration, endoleak formation and fracture of device components that may result in adverse events such as aneurysm enlargement, need for long-term imaging surveillance and secondary interventions or even death. These complications result from the device inability to withstand the hemodynamics of blood flow and to keep its originally intended post-operative position over time. Understanding the in vivo biomechanical working environment experienced by endografts is a critical factor in improving their long-term performance. To date, no study has investigated the mechanics of contact between device and aorta in a three-dimensional setting. In this work, we developed a comprehensive Computational Solid Mechanics and Computational Fluid Dynamics framework to investigate the mechanics of endograft positional stability. The main building blocks of this framework are: (1) Three-dimensional non-planar aortic and stent-graft geometrical models, (2) Realistic multi-material constitutive laws for aorta, stent, and graft, (3) Physiological values for blood flow and pressure, and (4) Frictional model to describe the contact between the endograft and the aorta. We introduce a new metric for numerical quantification of the positional stability of the endograft. Lastly, in the results section, we test the framework by investigating the impact of several factors that are clinically known to affect endograft stability.
Discrete random walk models for space-time fractional diffusion
International Nuclear Information System (INIS)
Gorenflo, Rudolf; Mainardi, Francesco; Moretti, Daniele; Pagnini, Gianni; Paradisi, Paolo
2002-01-01
A physical-mathematical approach to anomalous diffusion may be based on generalized diffusion equations (containing derivatives of fractional order in space or/and time) and related random walk models. By space-time fractional diffusion equation we mean an evolution equation obtained from the standard linear diffusion equation by replacing the second-order space derivative with a Riesz-Feller derivative of order α is part of (0,2] and skewness θ (moduleθ≤{α,2-α}), and the first-order time derivative with a Caputo derivative of order β is part of (0,1]. Such evolution equation implies for the flux a fractional Fick's law which accounts for spatial and temporal non-locality. The fundamental solution (for the Cauchy problem) of the fractional diffusion equation can be interpreted as a probability density evolving in time of a peculiar self-similar stochastic process that we view as a generalized diffusion process. By adopting appropriate finite-difference schemes of solution, we generate models of random walk discrete in space and time suitable for simulating random variables whose spatial probability density evolves in time according to this fractional diffusion equation
Nucleon structure functions in noncommutative space-time
Energy Technology Data Exchange (ETDEWEB)
Rafiei, A.; Rezaei, Z.; Mirjalili, A. [Yazd University, Physics Department, Yazd (Iran, Islamic Republic of)
2017-05-15
In the context of noncommutative space-time we investigate the nucleon structure functions which play an important role in identifying the internal structure of nucleons. We use the corrected vertices and employ new vertices that appear in two approaches of noncommutativity and calculate the proton structure functions in terms of the noncommutative tensor θ{sub μν}. To check our results we plot the nucleon structure function (NSF), F{sub 2}(x), and compare it with experimental data and the results from the GRV, GJR and CT10 parametrization models. We show that with the new vertex that arises the noncommutativity correction will lead to a better consistency between theoretical results and experimental data for the NSF. This consistency will be better for small values of the Bjorken variable x. To indicate and confirm the validity of our calculations we also act conversely. We obtain a lower bound for the numerical values of Λ{sub NC} scale which correspond to recent reports. (orig.)
Conformal quantum mechanics and holography in noncommutative space-time
Gupta, Kumar S.; Harikumar, E.; Zuhair, N. S.
2017-09-01
We analyze the effects of noncommutativity in conformal quantum mechanics (CQM) using the κ-deformed space-time as a prototype. Up to the first order in the deformation parameter, the symmetry structure of the CQM algebra is preserved but the coupling in a canonical model of the CQM gets deformed. We show that the boundary conditions that ensure a unitary time evolution in the noncommutative CQM can break the scale invariance, leading to a quantum mechanical scaling anomaly. We calculate the scaling dimensions of the two and three point functions in the noncommutative CQM which are shown to be deformed. The AdS2 / CFT1 duality for the CQM suggests that the corresponding correlation functions in the holographic duals are modified. In addition, the Breitenlohner-Freedman bound also picks up a noncommutative correction. The strongly attractive regime of a canonical model of the CQM exhibit quantum instability. We show that the noncommutativity softens this singular behaviour and its implications for the corresponding holographic duals are discussed.
Aging in a Relativistic Biological Space-Time
Directory of Open Access Journals (Sweden)
Davide Maestrini
2018-05-01
Full Text Available Here we present a theoretical and mathematical perspective on the process of aging. We extend the concepts of physical space and time to an abstract, mathematically-defined space, which we associate with a concept of “biological space-time” in which biological dynamics may be represented. We hypothesize that biological dynamics, represented as trajectories in biological space-time, may be used to model and study different rates of biological aging. As a consequence of this hypothesis, we show how dilation or contraction of time analogous to relativistic corrections of physical time resulting from accelerated or decelerated biological dynamics may be used to study precipitous or protracted aging. We show specific examples of how these principles may be used to model different rates of aging, with an emphasis on cancer in aging. We discuss how this theory may be tested or falsified, as well as novel concepts and implications of this theory that may improve our interpretation of biological aging.
Yu, Xinguang; Li, Lianfeng; Wang, Peng; Yin, Yiheng; Bu, Bo; Zhou, Dingbiao
2014-07-01
This study was designed to report our preliminary experience with stabilization procedures for complex craniovertebral junction malformation (CVJM) using intraoperative computed tomography (iCT) with an integrated neuronavigation system (NNS). To evaluate the workflow, feasibility and clinical outcome of stabilization procedures using iCT image-guided navigation for complex CVJM. The stabilization procedures in CVJM are complex because of the area's intricate geometry and bony structures, its critical relationship to neurovascular structures and the intricate biomechanical issues involved. A sliding gantry 40-slice computed tomography scanner was installed in a preexisting operating room. The images were transferred directly from the scanner to the NNS using an automated registration system. On the basis of the analysis of intraoperative computed tomographic images, 23 cases (11 males, 12 females) with complicated CVJM underwent navigated stabilization procedures to allow more control over screw placement. The age of these patients were 19-52 years (mean: 33.5 y). We performed C1-C2 transarticular screw fixation in 6 patients to produce atlantoaxial arthrodesis with better reliability. Because of a high-riding transverse foramen on at least 1 side of the C2 vertebra and an anomalous vertebral artery position, 7 patients underwent C1 lateral mass and C2 pedicle screw fixation. Ten additional patients were treated with individualized occipitocervical fixation surgery from the hypoplasia of C1 or constraints due to C2 bone structure. In total, 108 screws were inserted into 23 patients using navigational assistance. The screws comprised 20 C1 lateral mass screws, 26 C2, 14 C3, or 4 C4 pedicle screws, 32 occipital screws, and 12 C1-C2 transarticular screws. There were no vascular or neural complications except for pedicle perforations that were detected in 2 (1.9%) patients and were corrected intraoperatively without any persistent nerves or vessel damage. The overall
Directory of Open Access Journals (Sweden)
Muhammad H. Al-Malack
2016-07-01
Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.
A global conformal extension theorem for perfect fluid Bianchi space-times
International Nuclear Information System (INIS)
Luebbe, Christian; Tod, Paul
2008-01-01
A global extension theorem is established for isotropic singularities in polytropic perfect fluid Bianchi space-times. When an extension is possible, the limiting behaviour of the physical space-time near the singularity is analysed
The space-time operator product expansion in string theory duals of field theories
International Nuclear Information System (INIS)
Aharony, Ofer; Komargodski, Zohar
2008-01-01
We study the operator product expansion (OPE) limit of correlation functions in field theories which possess string theory duals, from the point of view of the string worldsheet. We show how the interesting ('single-trace') terms in the OPE of the field theory arise in this limit from the OPE of the worldsheet theory of the string dual, using a dominant saddle point which appears in computations of worldsheet correlation functions in the space-time OPE limit. The worldsheet OPE generically contains only non-physical operators, but all the non-physical contributions are resummed by the saddle point to a contribution similar to that of a physical operator, which exactly matches the field theory expectations. We verify that the OPE limit of the worldsheet theory does not have any other contributions to the OPE limit of space-time correlation functions. Our discussion is completely general and applies to any local field theory (conformal at high energies) that has a weakly coupled string theory dual (with arbitrary curvature). As a first application, we compare our results to a proposal of R. Gopakumar for the string theory dual of free gauge theories
Space-time-matter analytic and geometric structures
Brüning, Jochen
2018-01-01
At the boundary of mathematics and mathematical physics, this monograph explores recent advances in the mathematical foundations of string theory and cosmology. The geometry of matter and the evolution of geometric structures as well as special solutions, singularities and stability properties of the underlying partial differential equations are discussed.
A new theory of space-time and gravitation
International Nuclear Information System (INIS)
Denisov, V.I.; Logunov, A.A.
1982-01-01
Field theory of gravitation is constructed. It uses a symmetrical second rank tensor field in pseudoeuclidean space-time for describing the gravitational field. The theory is based on the condition of the presence of conservation laws for gravitational field and matter taken together and on the geometrization principle. The field theory of gravitation has the same post-newtonian parame-- ters as the general relativity theory (GRT) which implies that both theories are indistinguishable from the viewpoint of any post- newtonian experiment. The description of the effects in strong gravitational fields as well as properties of gravitational waves in the field theory of gravitation and GRT differ significantly from each other. The distinctions between two theories include also the itational red shifti curving of light trajectories and timabsence in the field theory of gravitation of the effects of grav.. delay/ in processes of propagation of gravitational waves in external fields. These distinctions made it possible to suggest a number of experiments with gravitational waves in which the predictions of the field theory of gravitation can be compared with those of the GRT. Model of the Universe in the field theory of gravitation makes it possible to describe the cosmological red shift of the frequency. Character of the evolution in this mode is determined by the delay parameter q 0 : at q 0 0 >4-3/2xα the ''expansion'' at some moment will ''change'' to contraction'' and the Universe will return to the singular state, where α=8πepsilon 0 /3M 2 (H is the Hubble constant) [ru
Two methods of space--time energy densification
International Nuclear Information System (INIS)
Sahlin, R.L.
1976-01-01
With a view to the goal of net energy production from a DT microexplosion, we study two ideas (methods) through which (separately or in combination) energy may be ''concentrated'' into a small volume and short period of time--the so-called space-time energy densification or compression. We first discuss the advantages and disadvantages of lasers and relativistic electron-beam (E-beam) machines as the sources of such energy and identify the amplification of laser pulses as a key factor in energy compression. The pulse length of present relativistic E-beam machines is the most serious limitation of this pulsed-power source. The first energy-compression idea we discuss is the reasonably efficient production of short-duration, high-current relativistic electron pulses by the self interruption and restrike of a current in a plasma pinch due to the rapid onset of strong turbulence. A 1-MJ plasma focus based on this method is nearing completion at this Laboratory. The second energy-compression idea is based on laser-pulse production through the parametric amplification of a self-similar or solitary wave pulse, for which analogs can be found in other wave processes. Specifically, the second energy-compression idea is a proposal for parametric amplification of a solitary, transverse magnetic pulse in a coaxial cavity with a Bennett dielectric rod as an inner coax. Amplifiers of this type can be driven by the pulsed power from a relativistic E-beam machine. If the end of the inner dielectric coax is made of LiDT or another fusionable material, the amplified pulse can directly drive a fusion reaction--there would be no need to switch the pulse out of the system toward a remote target
Surviving in a metastable de Sitter space-time
International Nuclear Information System (INIS)
Kashyap, Sitender Pratap; Mondal, Swapnamay; Sen, Ashoke; Verma, Mritunjay
2015-01-01
In a metastable de Sitter space any object has a finite life expectancy beyond which it undergoes vacuum decay. However, by spreading into different parts of the universe which will fall out of causal contact of each other in future, a civilization can increase its collective life expectancy, defined as the average time after which the last settlement disappears due to vacuum decay. We study in detail the collective life expectancy of two comoving objects in de Sitter space as a function of the initial separation, the horizon radius and the vacuum decay rate. We find that even with a modest initial separation, the collective life expectancy can reach a value close to the maximum possible value of 1.5 times that of the individual object if the decay rate is less than 1% of the expansion rate. Our analysis can be generalized to any number of objects, general trajectories not necessarily at rest in the comoving coordinates and general FRW space-time. As part of our analysis we find that in the current state of the universe dominated by matter and cosmological constant, the vacuum decay rate is increasing as a function of time due to accelerated expansion of the volume of the past light cone. Present decay rate is about 3.7 times larger than the average decay rate in the past and the final decay rate in the cosmological constant dominated epoch will be about 56 times larger than the average decay rate in the past. This considerably weakens the lower bound on the half-life of our universe based on its current age.
Two methods of space-time energy densification
International Nuclear Information System (INIS)
Sahlin, H.L.
1975-01-01
With a view to the goal of net energy production from a DT microexplosion, two ideas (methods) are studied through which (separately or in combination) energy may be ''concentrated'' into a small volume and short period of time--the so-called space-time energy densification or compression. The advantages and disadvantages of lasers and relativistic electron-beam (E-beam) machines as the sources of such energy are studied and the amplification of laser pulses as a key factor in energy compression is discussed. The pulse length of present relativistic E-beam machines is the most serious limitation of this pulsed-power source. The first energy-compression idea discussed is the reasonably efficient production of short-duration, high-current relativistic electron pulses by the self interruption and restrike of a current in a plasma pinch due to the rapid onset of strong turbulence. A 1-MJ plasma focus based on this method is nearing completion at this Laboratory. The second energy-compression idea is based on laser-pulse production through the parametric amplification of a self-similar or solitary wave pulse, for which analogs can be found in other wave processes. Specifically, the second energy-compression idea is a proposal for parametric amplification of a solitary, transverse magnetic pulse in a coaxial cavity with a Bennett dielectric rod as an inner coax. Amplifiers of this type can be driven by the pulsed power from a relativistic E-beam machine. If the end of the inner dielectric coax is made of LiDT or another fusionable material, the amplified pulse can directly drive a fusion reaction--there would be no need to switch the pulse out of the system toward a remote target. (auth)
Surviving in a metastable de Sitter space-time
Energy Technology Data Exchange (ETDEWEB)
Kashyap, Sitender Pratap; Mondal, Swapnamay [Harish-Chandra Research Institute,Chhatnag Road, Jhusi, Allahabad 211019 (India); Sen, Ashoke [Harish-Chandra Research Institute,Chhatnag Road, Jhusi, Allahabad 211019 (India); School of Physics, Korea Institute for Advanced Study,Seoul 130-722 (Korea, Republic of); Verma, Mritunjay [Harish-Chandra Research Institute,Chhatnag Road, Jhusi, Allahabad 211019 (India); International Centre for Theoretical Sciences,Malleshwaram, Bengaluru 560 012 (India)
2015-09-21
In a metastable de Sitter space any object has a finite life expectancy beyond which it undergoes vacuum decay. However, by spreading into different parts of the universe which will fall out of causal contact of each other in future, a civilization can increase its collective life expectancy, defined as the average time after which the last settlement disappears due to vacuum decay. We study in detail the collective life expectancy of two comoving objects in de Sitter space as a function of the initial separation, the horizon radius and the vacuum decay rate. We find that even with a modest initial separation, the collective life expectancy can reach a value close to the maximum possible value of 1.5 times that of the individual object if the decay rate is less than 1% of the expansion rate. Our analysis can be generalized to any number of objects, general trajectories not necessarily at rest in the comoving coordinates and general FRW space-time. As part of our analysis we find that in the current state of the universe dominated by matter and cosmological constant, the vacuum decay rate is increasing as a function of time due to accelerated expansion of the volume of the past light cone. Present decay rate is about 3.7 times larger than the average decay rate in the past and the final decay rate in the cosmological constant dominated epoch will be about 56 times larger than the average decay rate in the past. This considerably weakens the lower bound on the half-life of our universe based on its current age.
Electromagnetic-field equations in the six-dimensional space-time R6
International Nuclear Information System (INIS)
Teli, M.T.; Palaskar, D.
1984-01-01
Maxwell's equations (without monopoles) for electromagnetic fields are obtained in six-dimensional space-time. The equations possess structural symmetry in space and time, field and source densities. Space-time-symmetric conservation laws and field solutions are obtained. The results are successfully correlated with their four-dimensional space-time counterparts
Hassan, Mubashir; Abbas, Qamar; Raza, Hussain; Moustafa, Ahmed A; Seo, Sung-Yum
2017-07-25
Misfolding and structural alteration in proteins lead to serious malfunctions and cause various diseases in humans. Mutations at the active binding site in tyrosinase impair structural stability and cause lethal albinism by abolishing copper binding. To evaluate the histidine mutational effect, all mutated structures were built using homology modelling. The protein sequence was retrieved from the UniProt database, and 3D models of original and mutated human tyrosinase sequences were predicted by changing the residual positions within the target sequence separately. Structural and mutational analyses were performed to interpret the significance of mutated residues (N 180 , R 202 , Q 202 , R 211 , Y 363 , R 367 , Y 367 and D 390 ) at the active binding site of tyrosinases. CSpritz analysis depicted that 23.25% residues actively participate in the instability of tyrosinase. The accuracy of predicted models was confirmed through online servers ProSA-web, ERRAT score and VERIFY 3D values. The theoretical pI and GRAVY generated results also showed the accuracy of the predicted models. The CCA negative correlation results depicted that the replacement of mutated residues at His within the active binding site disturbs the structural stability of tyrosinases. The predicted CCA scores of Tyr 367 (-0.079) and Q/R 202 (0.032) revealed that both mutations have more potential to disturb the structural stability. MD simulation analyses of all predicted models justified that Gln 202 , Arg 202 , Tyr 367 and D 390 replacement made the protein structures more susceptible to destabilization. Mutational results showed that the replacement of His with Q/R 202 and Y/R 363 has a lethal effect and may cause melanin associated diseases such as OCA1. Taken together, our computational analysis depicts that the mutated residues such as Q/R 202 and Y/R 363 actively participate in instability and misfolding of tyrosinases, which may govern OCA1 through disturbing the melanin biosynthetic pathway.
International Nuclear Information System (INIS)
Gui Xuewen; Cai Qi; Luo Bangqi
2007-01-01
A two-group three-dimension space-time neutron kinetics model is applied to the RELAP5 code, which replaces the point reactor kinetics model. A visual operation interface is designed to convenience interactive operation between operator and computer. The calculation results and practical applications indicate that the functions and precision of improved RELAP5 are enhanced and can be easily used. The improved RELAP5 has a good application perspective in nuclear power plant simulation. (authors)
Insight into the structures and stabilities of Tc and Re DMSA complexes: A computational study
International Nuclear Information System (INIS)
Blanco González, Alejandro; Hernández Valdés, Daniel; García Fleitas, Ariel; Rodríguez Riera, Zalua; Jáuregui Haza, Ulises
2016-01-01
Meso-2,3-dimercaptosuccinic acid (DMSA) is used in nuclear medicine as ligand for preparation of radiopharmaceuticals for diagnostic and therapy. DMSA has been the subject of numerous investigations during the past three decades and new and significant information of the chemistry and pharmacology of DMSA complexes have emerged. In comparison to other ligands, the structure of some DMSA complexes is unclear up today. The structures and applications of DMSA complexes are strictly dependent on the chemical conditions of their preparation, especially pH and the ratio of components. A computational study of M-DMSA (M = Tc, Re) complexes has been performed using density functional theory. Different isomers for M(V) and M(III) complexes were study. The pH influence over ligand structures was taken into account and the solvent effect was evaluated using an implicit solvation model. The fully optimized complex syn-endo Re(V)-DMSA shows a geometry similar to the X-ray data and was used to validate the methodology. Moreover, new alternative structures for the renal agent 99mTc(III)-DMSA were proposed and computationally studied. For two complex structures, a larger stability respect to that proposed in the literature was obtained. Furthermore, Tc(V)-DMSA complexes are more stable than the Tc(III)-DMSA proposed structures. In general, Re complexes are more stables than the corresponding Tc ones. (author)
Energy Technology Data Exchange (ETDEWEB)
Lundquist, J K; Chan, S T
2005-11-30
The validity of omitting stability considerations when simulating transport and dispersion in the urban environment is explored using observations from the Joint URBAN 2003 field experiment and computational fluid dynamics simulations of that experiment. Four releases of sulfur hexafluoride, during two daytime and two nighttime intensive observing periods, are simulated using the building-resolving computational fluid dynamics model, FEM3MP to solve the Reynolds Averaged Navier-Stokes equations with two options of turbulence parameterizations. One option omits stability effects but has a superior turbulence parameterization using a non-linear eddy viscosity (NEV) approach, while the other considers buoyancy effects with a simple linear eddy viscosity (LEV) approach for turbulence parameterization. Model performance metrics are calculated by comparison with observed winds and tracer data in the downtown area, and with observed winds and turbulence kinetic energy (TKE) profiles at a location immediately downwind of the central business district (CBD) in the area we label as the urban shadow. Model predictions of winds, concentrations, profiles of wind speed, wind direction, and friction velocity are generally consistent with and compare reasonably well with the field observations. Simulations using the NEV turbulence parameterization generally exhibit better agreement with observations. To further explore this assumption of a neutrally-stable atmosphere within the urban area, TKE budget profiles slightly downwind of the urban wake region in the 'urban shadow' are examined. Dissipation and shear production are the largest terms which may be calculated directly. The advection of TKE is calculated as a residual; as would be expected downwind of an urban area, the advection of TKE produced within the urban area is a very large term. Buoyancy effects may be neglected in favor of advection, shear production, and dissipation. For three of the IOPs, buoyancy
Multiple-Symbol Decision-Feedback Space-Time Differential Decoding in Fading Channels
Directory of Open Access Journals (Sweden)
Wang Xiaodong
2002-01-01
Full Text Available Space-time differential coding (STDC is an effective technique for exploiting transmitter diversity while it does not require the channel state information at the receiver. However, like conventional differential modulation schemes, it exhibits an error floor in fading channels. In this paper, we develop an STDC decoding technique based on multiple-symbol detection and decision-feedback, which makes use of the second-order statistic of the fading processes and has a very low computational complexity. This decoding method can significantly lower the error floor of the conventional STDC decoding algorithm, especially in fast fading channels. The application of the proposed multiple-symbol decision-feedback STDC decoding technique in orthogonal frequency-division multiplexing (OFDM system is also discussed.
Energy Savings in Cellular Networks Based on Space-Time Structure of Traffic Loads
Sun, Jingbo; Wang, Yue; Yuan, Jian; Shan, Xiuming
Since most of energy consumed by the telecommunication infrastructure is due to the Base Transceiver Station (BTS), switching off BTSs when traffic load is low has been recognized as an effective way of saving energy. In this letter, an energy saving scheme is proposed to minimize the number of active BTSs based on the space-time structure of traffic loads as determined by principal component analysis. Compared to existing methods, our approach models traffic loads more accurately, and has a much smaller input size. As it is implemented in an off-line manner, our scheme also avoids excessive communications and computing overheads. Simulation results show that the proposed method has a comparable performance in energy savings.
Coherent states for FLRW space-times in loop quantum gravity
International Nuclear Information System (INIS)
Magliaro, Elena; Perini, Claudio; Marciano, Antonino
2011-01-01
We construct a class of coherent spin-network states that capture properties of curved space-times of the Friedmann-Lamaitre-Robertson-Walker type on which they are peaked. The data coded by a coherent state are associated to a cellular decomposition of a spatial (t=const) section with a dual graph given by the complete five-vertex graph, though the construction can be easily generalized to other graphs. The labels of coherent states are complex SL(2,C) variables, one for each link of the graph, and are computed through a smearing process starting from a continuum extrinsic and intrinsic geometry of the canonical surface. The construction covers both Euclidean and Lorentzian signatures; in the Euclidean case and in the limit of flat space we reproduce the simplicial 4-simplex semiclassical states used in spin foams.
International Nuclear Information System (INIS)
Pontaza, J.P.; Reddy, J.N.
2004-01-01
We consider least-squares finite element models for the numerical solution of the non-stationary Navier-Stokes equations governing viscous incompressible fluid flows. The paper presents a formulation where the effects of space and time are coupled, resulting in a true space-time least-squares minimization procedure, as opposed to a space-time decoupled formulation where a least-squares minimization procedure is performed in space at each time step. The formulation is first presented for the linear advection-diffusion equation and then extended to the Navier-Stokes equations. The formulation has no time step stability restrictions and is spectrally accurate in both space and time. To allow the use of practical C 0 element expansions in the resulting finite element model, the Navier-Stokes equations are expressed as an equivalent set of first-order equations by introducing vorticity as an additional independent variable and the least-squares method is used to develop the finite element model of the governing equations. High-order element expansions are used to construct the discrete model. The discrete model thus obtained is linearized by Newton's method, resulting in a linear system of equations with a symmetric positive definite coefficient matrix that is solved in a fully coupled manner by a preconditioned conjugate gradient method in matrix-free form. Spectral convergence of the L 2 least-squares functional and L 2 error norms in space-time is verified using a smooth solution to the two-dimensional non-stationary incompressible Navier-Stokes equations. Numerical results are presented for impulsively started lid-driven cavity flow, oscillatory lid-driven cavity flow, transient flow over a backward-facing step, and flow around a circular cylinder; the results demonstrate the predictive capability and robustness of the proposed formulation. Even though the space-time coupled formulation is emphasized, we also present the formulation and numerical results for least
Argula, Rahul G; Kokosi, Maria; Lo, Pechin; Kim, Hyun J; Ravenel, James G; Meyer, Cristopher; Goldin, Jonathan; Lee, Hye-Seung; Strange, Charlie; McCormack, Francis X
2016-03-01
The Multicenter International Lymphangioleiomyomatosis Efficacy and Safety of Sirolimus (MILES) trial demonstrated that sirolimus stabilized lung function and improved measures of functional performance and quality of life in patients with lymphangioleiomyomatosis. The physiologic mechanisms of these beneficial actions of sirolimus are incompletely understood. To prospectively determine the longitudinal computed tomographic lung imaging correlates of lung function change in MILES patients treated with placebo or sirolimus. We determined the baseline to 12-month change in computed tomographic image-derived lung volumes and the volume of the lung occupied by cysts in the 31 MILES participants (17 in sirolimus group, 14 in placebo group) with baseline and 12-month scans. There was a trend toward an increase in median expiratory cyst volume percentage in the placebo group and a reduction in the sirolimus group (+2.68% vs. +0.97%, respectively; P = 0.10). The computed tomographic image-derived residual volume and the ratio of residual volume to total lung capacity increased more in the placebo group than in the sirolimus group (+214.4 ml vs. +2.9 ml [P = 0.054] and +0.05 ml vs. -0.01 ml [P = 0.0498], respectively). A Markov transition chain analysis of respiratory cycle cyst volume changes revealed greater dynamic variation in the sirolimus group than in the placebo group at the 12-month time point. Collectively, these data suggest that sirolimus attenuates progressive gas trapping in lymphangioleiomyomatosis, consistent with a beneficial effect of the drug on airflow obstruction. We speculate that a reduction in lymphangioleiomyomatosis cell burden around small airways and cyst walls alleviates progressive airflow limitation and facilitates cyst emptying.
Quantum theory of spinor field in four-dimensional Riemannian space-time
International Nuclear Information System (INIS)
Shavokhina, N.S.
1996-01-01
The review deals with the spinor field in the four-dimensional Riemannian space-time. The field beys the Dirac-Fock-Ivanenko equation. Principles of quantization of the spinor field in the Riemannian space-time are formulated which in a particular case of the plane space-time are equivalent to the canonical rules of quantization. The formulated principles are exemplified by the De Sitter space-time. The study of quantum field theory in the De Sitter space-time is interesting because it itself leads to a method of an invariant well for plane space-time. However, the study of the quantum spinor field theory in an arbitrary Riemannian space-time allows one to take into account the influence of the external gravitational field on the quantized spinor field. 60 refs
Forecasting the space-time stability of radioactive waste isolation in salt formations
International Nuclear Information System (INIS)
Anderson, E.B.; Karelin, A.I.; Krivokhatsiy, A.S.; Savonenkov, V.G.
1992-01-01
The possibilities to use salt formations for radioactive waste isolation are realized by creating shaft-type underground repositories in these rocks in Germany and the USA. The burial safety of low- and intermediate-level wastes for several hundred years have been substantiated for the sites chosen. Specialists of different countries presented positive properties of rock salt as a medium for isolation of radionuclides. A rich experience in building subsurface structures for different purposes in salts is accumulated in our country. Detailed investigations of salt formation have shown that far from all the saliferous areas and structures may be used for constructing burial sites. One of the reasons for this limitation is a sharp difference of individual deposits by their compositions, structures, the character of deposition and the conditions of formation. The geological criteria of safety acquire special significance in connection with the necessity to isolate radionuclides having the half-loves more than 1000 years. The time intervals required for stable isolation make up millions of years and cover great cycles of the evolution of the Earth surface and biosphere
Regularization and renormalization of quantum field theory in curved space-time
International Nuclear Information System (INIS)
Bernard, C.; Duncan, A.
1977-01-01
It is proposed that field theories quantized in a curved space-time manifold can be conveniently regularized and renormalized with the aid of Pauli-Villars regulator fields. The method avoids the conceptual difficulties of covariant point-separation approaches, by starting always from a manifestly generally covariant action, and the technical limitations of the dimensional reqularization approach, which requires solution of the theory in arbitrary dimension in order to go beyond a weak-field expansion. An action is constructed which renormalizes the weak-field perturbation theory of a massive scalar field in two space-time dimensions--it is shown that the trace anomaly previously found in dimensional regularization and some point-separation calculations also arises in perturbation theory when the theory is Pauli-Villars regulated. One then studies a specific solvable two-dimensional model of a massive scalar field in a Robertson-Walker asymptotically flat universe. It is shown that the action previously considered leads, in this model, to a well defined finite expectation value for the stress-energy tensor. The particle production (less than 0 in/vertical bar/theta/sup mu nu/(x,t)/vertical bar/0 in greater than for t → + infinity) is computed explicitly. Finally, the validity of weak-field perturbation theory (in the appropriate range of parameters) is checked directly in the solvable model, and the trace anomaly computed in the asymptotic regions t→ +- infinity independently of any weak field approximation. The extension of the model to higher dimensions and the renormalization of interacting (scalar) field theories are briefly discussed
DEFF Research Database (Denmark)
Silcowitz-Hansen, Morten; Abel, Sarah Maria Niebe; Erleben, Kenny
2010-01-01
We present a novel, yet simple, method for stabilization of normal forces. A normal stabilization term, carefully designed from hypotheses about interactive usability, is added to the contact force problem. Further, we propose friction stabilization as a completely new stabilization paradigm...
Temperature and entropy of Schwarzschild-de Sitter space-time
International Nuclear Information System (INIS)
Shankaranarayanan, S.
2003-01-01
In the light of recent interest in quantum gravity in de Sitter space, we investigate semiclassical aspects of four-dimensional Schwarzschild-de Sitter space-time using the method of complex paths. The standard semiclassical techniques (such as Bogoliubov coefficients and Euclidean field theory) have been useful to study quantum effects in space-times with single horizons; however, none of these approaches seem to work for Schwarzschild-de Sitter space-time or, in general, for space-times with multiple horizons. We extend the method of complex paths to space-times with multiple horizons and obtain the spectrum of particles produced in these space-times. We show that the temperature of radiation in these space-times is proportional to the effective surface gravity--the inverse harmonic sum of surface gravity of each horizon. For the Schwarzschild-de Sitter space-time, we apply the method of complex paths to three different coordinate systems--spherically symmetric, Painleve, and Lemaitre. We show that the equilibrium temperature in Schwarzschild-de Sitter space-time is the harmonic mean of cosmological and event horizon temperatures. We obtain Bogoliubov coefficients for space-times with multiple horizons by analyzing the mode functions of the quantum fields near the horizons. We propose a new definition of entropy for space-times with multiple horizons, analogous to the entropic definition for space-times with a single horizon. We define entropy for these space-times to be inversely proportional to the square of the effective surface gravity. We show that this definition of entropy for Schwarzschild-de Sitter space-time satisfies the D-bound conjecture
Charged anisotropic star on paraboloidal space-time
Indian Academy of Sciences (India)
2015-11-27
Proceedings of the International Workshop/Conference on Computational Condensed Matter Physics and Materials Science (IWCCMP-2015). Posted on November 27, 2015. Guest Editors: Anurag Srivastava, C. S. Praveen, H. S. Tewari. © 2017 Indian Academy of Sciences, Bengaluru. Contact | Site index.
Fang, Yi; Peng, Chen; Guo, Rui; Zheng, Linfeng; Qin, Jinbao; Zhou, Benqing; Shen, Mingwu; Lu, Xinwu; Zhang, Guixiang; Shi, Xiangyang
2013-06-07
We report here a general approach to synthesizing dendrimer-stabilized bismuth sulfide nanoparticles (Bi2S3 DSNPs) for potential computed tomography (CT) imaging applications. In this study, ethylenediamine core glycidol hydroxyl-terminated generation 4 poly(amidoamine) dendrimers (G4.NGlyOH) were used as stabilizers to first complex the Bi(III) ions, followed by reaction with hydrogen sulfide to generate Bi2S3 DSNPs. By varying the molar ratio of Bi atom to dendrimer, stable Bi2S3 DSNPs with an average size range of 5.2-5.7 nm were formed. The formed Bi2S3 DSNPs were characterized via different techniques. X-ray absorption coefficient measurements show that the attenuation of Bi2S3 DSNPs is much higher than that of iodine-based CT contrast agent at the same molar concentration of the active element (Bi versus iodine). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay and hemolysis assay reveal that the formed Bi2S3 DSNPs are noncytotoxic and have a negligible hemolysis effect in the studied concentration range. Furthermore, we show that cells incubated with the Bi2S3 DSNPs are able to be imaged using CT, a prominent enhancement at the point of rabbit injected subcutaneously with the Bi2S3 DSNPs is able to be visualized via CT scanning, and the mouse's pulmonary vein can be visualized via CT after intravenous injection of the Bi2S3 DSNPs. With the good biocompatibility, enhanced X-ray attenuation property, and tunable dendrimer chemistry, the designed Bi2S3 DSNPs should be able to be further functionalized, allowing them to be used as a highly efficient contrast agent for CT imaging of different biological systems.
A space-time analysis of PWR rod ejection accident
International Nuclear Information System (INIS)
Aoki, K.; Kanezashi, M.; Kato, M.; Nishimura, Y.; Satoh, T.
1985-01-01
This paper presents an efficient and reliable method to perform V-Q loss minimization control. A method proposed here is suitable for a decentralized control system (a hierarchy control system), taking full advantage of the dispatching organization and system structures. This is also a practical method, taking computational requirements and transmitted information into consideration. A feasible type, decomposition technique of quadratic programming underlies our method. Numerical results show that execution time, memory requirements, and convergence property are satisfactory
International Nuclear Information System (INIS)
Koukkari, P.; Olin, M.; Laitinen, T.; Sippola, H.
1999-04-01
The oxide films formed on primary circuit surfaces incorporate radioactive species from the coolant and influence different corrosion phenomena in nuclear power plants. One approach to improve the understanding on the formation and properties of these oxide films is to evaluate their thermodynamic stability. The aim of this work was to compare and demonstrate the applicability of different commercial thermodynamic computer programs to model the deposition of oxides containing iron, chromium and/or nickel in various nuclear power plant environments. The programs considered in this evaluation comprised the EQ3/6 program and a product group including such products as ChemSage, HSC (including SOLGASMIX and GIBBS), H+PLUS and ChemSheet. In the group the transfer of data between different products is relatively easy. The goal was to find out which programs can be applied to evaluate the stability of oxide films, but not to assess the absolute accuracy of the calculations. The evaluation was done by means of applying the programs to calculate the stability of pure and mixed oxides of iron, nickel and chromium on stainless steel both in WWER and BWR conditions at different temperatures and coolant compositions. The comparison showed that EQ3/6 is suitable for most thermodynamic calculations. EQ3/6 can be characterised as a professional tool, for which no commercial training is available. ChemSage is a versatile and reliable program, which can be well used together with HSC and H+PLUS. ChemSage is mainly a professional tool, while HSC is easier to operate by an occasional user. Commercial training and support is available for both ChemSage and HSC. ChemSheet has been designed to utilise the properties of ChemSage in a user-friendly spreadsheet environment. All the products tested calculate thermodynamic equilibrium. Thus they are suitable to characterise such conditions in which the formation of a certain phase is or becomes possible. On the other hand, the modelling of the
VALIDATING A COMPUTER-BASED TECHNIQUE FOR ASSESSING STABILITY TO FAILURE STRESS
Directory of Open Access Journals (Sweden)
I. F. Arshava
2013-03-01
Full Text Available An upsurge of interest in the implicit personality assessment, currently observed both in personality psycho-diagnostics and in experimental studies of social attitudes and prejudices, signals the shifting of researchers’ attention from de?ning between-person personality taxonomy to specifying comprehensive within-person processes, the dynamics of which can be captured at the level of an individual case. This research examines the possibility of the implicit assessment of the individual’s stability vs. susceptibility to failure stress by comparing the degrees of ef?cacy in the voluntary self-regulation of a computer-simulated information-processing activity under different conditions (patent of Ukraine № 91842, issued in 2010. By exposing two groups of participants (university undergraduates to processing the information, the scope of which exceeds the human short-term memory capacity at one of the stages of the modeled activity an unexpected and unavoidable failure is elicited. The participants who retain stability of their self-regulation behavior after having been exposed to failure, i.e. who keep processing information as effectively as they did prior to failure, are claimed to retain homeostasis and thus possess emotional stability. Those, who loose homeostasis after failure and display lower standards of self-regulation behavior, are considered to be susceptible to stress. The validity of the suggested type of the implicit diagnostics was empirically tested by clustering (K-means algorithm two samples of the participants on the properties of their self-regulation behavior and testing between-cluster differences by a set of the explicitly assessed variables: Action control ef?cacy (Kuhl, 2001, preferred strategies of Coping with Stressful Situations (Endler, Parker, 1990, Purpose-in-Life orientation (a Russian version of the test by Crumbaugh and Maholick, modi?ed by D.Leontiev, 1992, Psychological Well-being (Ryff, 1989
Directory of Open Access Journals (Sweden)
Tatiana R. Shmeleva
2018-01-01
Full Text Available In this paper, we consider the classification and applications of switching methods, their advantages and disadvantages. A model of a computing grid was constructed in the form of a colored Petri net with a node which implements cut-through packet switching. The model consists of packet switching nodes, traffic generators and guns that form malicious traffic disguised as usual user traffic. The characteristics of the grid model were investigated under a working load with different intensities. The influence of malicious traffic such as traffic duel was estimated on the quality of service parameters of the grid. A comparative analysis of the computing grids stability was carried out with nodes which implement the store-and-forward and cut-through switching technologies. It is shown that the grids performance is approximately the same under work load conditions, and under peak load conditions the grid with the node implementing the store-and-forward technology is more stable. The grid with nodes implementing SAF technology comes to a complete deadlock through an additional load which is less than 10 percent. After a detailed study, it is shown that the traffic duel configuration does not affect the grid with cut-through nodes if the workload is increases to the peak load, at which the grid comes to a complete deadlock. The execution intensity of guns which generate a malicious traffic is determined by a random function with the Poisson distribution. The modeling system CPN Tools is used for constructing models and measuring parameters. Grid performance and average package delivery time are estimated in the grid on various load options.
Tetrahedral-Mesh Simulation of Turbulent Flows with the Space-Time Conservative Schemes
Chang, Chau-Lyan; Venkatachari, Balaji; Cheng, Gary C.
2015-01-01
Direct numerical simulations of turbulent flows are predominantly carried out using structured, hexahedral meshes despite decades of development in unstructured mesh methods. Tetrahedral meshes offer ease of mesh generation around complex geometries and the potential of an orientation free grid that would provide un-biased small-scale dissipation and more accurate intermediate scale solutions. However, due to the lack of consistent multi-dimensional numerical formulations in conventional schemes for triangular and tetrahedral meshes at the cell interfaces, numerical issues exist when flow discontinuities or stagnation regions are present. The space-time conservative conservation element solution element (CESE) method - due to its Riemann-solver-free shock capturing capabilities, non-dissipative baseline schemes, and flux conservation in time as well as space - has the potential to more accurately simulate turbulent flows using unstructured tetrahedral meshes. To pave the way towards accurate simulation of shock/turbulent boundary-layer interaction, a series of wave and shock interaction benchmark problems that increase in complexity, are computed in this paper with triangular/tetrahedral meshes. Preliminary computations for the normal shock/turbulence interactions are carried out with a relatively coarse mesh, by direct numerical simulations standards, in order to assess other effects such as boundary conditions and the necessity of a buffer domain. The results indicate that qualitative agreement with previous studies can be obtained for flows where, strong shocks co-exist along with unsteady waves that display a broad range of scales, with a relatively compact computational domain and less stringent requirements for grid clustering near the shock. With the space-time conservation properties, stable solutions without any spurious wave reflections can be obtained without a need for buffer domains near the outflow/farfield boundaries. Computational results for the
International Nuclear Information System (INIS)
Comelli, D.; Riotto, A.
1995-06-01
Motivated by cosmological applications like electroweak baryogenesis, we develop a field theoretic approach to the computation of particle currents on a space-time dependent and CP-violating Higgs background. We consider the Standard Model model with two Higgs doublets and CP violation in the scalar sector, and compute both fermionic and Higgs currents by means of an expansion in the background fields. We discuss the gauge dependence of the results and the renormalization of the current operators, showing that in the limit of local equilibrium, no extra renormalization conditions are needed in order to specify the system completely. (orig.)
Kia, Mohammad; Wright, Timothy M; Cross, Michael B; Mayman, David J; Pearle, Andrew D; Sculco, Peter K; Westrich, Geoffrey H; Imhauser, Carl W
2018-01-01
The correct amount of external rotation of the femoral component during TKA is controversial because the resulting changes in biomechanical knee function associated with varying degrees of femoral component rotation are not well understood. We addressed this question using a computational model, which allowed us to isolate the biomechanical impact of geometric factors including bony shapes, location of ligament insertions, and implant size across three different knees after posterior-stabilized (PS) TKA. Using a computational model of the tibiofemoral joint, we asked: (1) Does external rotation unload the medial collateral ligament (MCL) and what is the effect on lateral collateral ligament tension? (2) How does external rotation alter tibiofemoral contact loads and kinematics? (3) Does 3° external rotation relative to the posterior condylar axis align the component to the surgical transepicondylar axis (sTEA) and what anatomic factors of the femoral condyle explain variations in maximum MCL tension among knees? We incorporated a PS TKA into a previously developed computational knee model applied to three neutrally aligned, nonarthritic, male cadaveric knees. The computational knee model was previously shown to corroborate coupled motions and ligament loading patterns of the native knee through a range of flexion. Implant geometries were virtually installed using hip-to-ankle CT scans through measured resection and anterior referencing surgical techniques. Collateral ligament properties were standardized across each knee model by defining stiffness and slack lengths based on the healthy population. The femoral component was externally rotated from 0° to 9° relative to the posterior condylar axis in 3° increments. At each increment, the knee was flexed under 500 N compression from 0° to 90° simulating an intraoperative examination. The computational model predicted collateral ligament forces, compartmental contact forces, and tibiofemoral internal/external and
International Nuclear Information System (INIS)
Pletzer, A.; Bondeson, A.; Dewar, R.L.
1993-11-01
The quest to determine accurately the stability of tearing and resistive interchange modes in two-dimensional toroidal geometry led to the development of the PEST-3 code, which is based on solving the singular, zero-frequency ideal MHD equation in the plasma bulk and determining the outer data Δ', Γ' and A' needed to match the outer region solutions to those arising in the inner layers. No assumption regarding the aspect ratio, the number of rational surfaces or the pressure are made a priori. This approach is numerically less demanding than solving the full set of resistive equations, and has the major advantage of non-MHD theories of the non-ideal layers. Good convergence is ensured by the variational Galerkin scheme used to compute the outer matching data. To validate the code, we focus on the growth rate calculations of resistive kink modes which are reproduced in good agreement with those obtained by the full resistive MHD code MARS. (author) 11 figs., 27 refs
Venkatachari, Balaji Shankar; Streett, Craig L.; Chang, Chau-Lyan; Friedlander, David J.; Wang, Xiao-Yen; Chang, Sin-Chung
2016-01-01
Despite decades of development of unstructured mesh methods, high-fidelity time-accurate simulations are still predominantly carried out on structured, or unstructured hexahedral meshes by using high-order finite-difference, weighted essentially non-oscillatory (WENO), or hybrid schemes formed by their combinations. In this work, the space-time conservation element solution element (CESE) method is used to simulate several flow problems including supersonic jet/shock interaction and its impact on launch vehicle acoustics, and direct numerical simulations of turbulent flows using tetrahedral meshes. This paper provides a status report for the continuing development of the space-time conservation element solution element (CESE) numerical and software framework under the Revolutionary Computational Aerosciences (RCA) project. Solution accuracy and large-scale parallel performance of the numerical framework is assessed with the goal of providing a viable paradigm for future high-fidelity flow physics simulations.
Directory of Open Access Journals (Sweden)
Haiwen Li
2018-01-01
Full Text Available The estimation speed of positioning parameters determines the effectiveness of the positioning system. The time of arrival (TOA and direction of arrival (DOA parameters can be estimated by the space-time two-dimensional multiple signal classification (2D-MUSIC algorithm for array antenna. However, this algorithm needs much time to complete the two-dimensional pseudo spectral peak search, which makes it difficult to apply in practice. Aiming at solving this problem, a fast estimation method of space-time two-dimensional positioning parameters based on Hadamard product is proposed in orthogonal frequency division multiplexing (OFDM system, and the Cramer-Rao bound (CRB is also presented. Firstly, according to the channel frequency domain response vector of each array, the channel frequency domain estimation vector is constructed using the Hadamard product form containing location information. Then, the autocorrelation matrix of the channel response vector for the extended array element in frequency domain and the noise subspace are calculated successively. Finally, by combining the closed-form solution and parameter pairing, the fast joint estimation for time delay and arrival direction is accomplished. The theoretical analysis and simulation results show that the proposed algorithm can significantly reduce the computational complexity and guarantee that the estimation accuracy is not only better than estimating signal parameters via rotational invariance techniques (ESPRIT algorithm and 2D matrix pencil (MP algorithm but also close to 2D-MUSIC algorithm. Moreover, the proposed algorithm also has certain adaptability to multipath environment and effectively improves the ability of fast acquisition of location parameters.
Black holes in loop quantum gravity: the complete space-time.
Gambini, Rodolfo; Pullin, Jorge
2008-10-17
We consider the quantization of the complete extension of the Schwarzschild space-time using spherically symmetric loop quantum gravity. We find an exact solution corresponding to the semiclassical theory. The singularity is eliminated but the space-time still contains a horizon. Although the solution is known partially numerically and therefore a proper global analysis is not possible, a global structure akin to a singularity-free Reissner-Nordström space-time including a Cauchy horizon is suggested.
A flat space-time relativistic explanation for the perihelion advance of Mercury
Behera, Harihar; Naik, P. C.
2003-01-01
Starting with the flat space-time relativistic versions of Maxwell-Heaviside's toy model vector theory of gravity and introducing the gravitational analogues for the electromagnetic Lienard-Wiechert potentials together with the notion of a gravitational Thomas Precession; the observed anomalous perihelion advance of Mercury's orbit is here explained as a relativistic effect in flat (Minkowski) space-time, unlike Einstein's curved space-time relativistic explanation. In this new explanation fo...
Fermion Systems in Discrete Space-Time Exemplifying the Spontaneous Generation of a Causal Structure
Diethert, A.; Finster, F.; Schiefeneder, D.
As toy models for space-time at the Planck scale, we consider examples of fermion systems in discrete space-time which are composed of one or two particles defined on two up to nine space-time points. We study the self-organization of the particles as described by a variational principle both analytically and numerically. We find an effect of spontaneous symmetry breaking which leads to the emergence of a discrete causal structure.
Quantum fields in cosmological space-times: a soluble example
International Nuclear Information System (INIS)
Costa, I.; Novello, M.; Svaiter, N.F.; Deruelle, N.
1988-01-01
The Klein-Gordon equation for a massive real scalar field in the Novello-Salim Eternal Universe, i.e., non singular spatial homogeneous and isotropic cosmological background which is tangent to Milne universes in the distant past and future (and hence asymptotically flat) and evolves between these two geometries via a phase of contraction to a point of maximum curvature followed by expansion is solved. This allows a computation of the Bogolyubov coefficients of the scalar field, usually interpreted as the rate of creation of matter by the time varying gravitational field, either when the vacuum is defined at the moment of maximum curvature (the false Big-Bang) or at the far beginning of the cosmic evolution. This new exact solution is compared to the results obtained when the geometry is that of the Milne universe. (author) [pt
Quaternionic formulation of tachyons, superluminal transformations and a complex space-time
Energy Technology Data Exchange (ETDEWEB)
Imaeda, K [Dublin Inst. for Advanced Studies (Ireland)
1979-04-11
A theory of tachyons and superluminal transformations is developed on the basis of the quaternionic formulation. A complex space-time adn a complex transformation group which contains both Lorentz transformations and superluminal transformations are introduced. The complex space-time '' the biquaternion space'' which is closed under the superluminal transformations is introduced. The principle of special relativity, such as the conservation of the quadratic form of the metric of the space-time, and the principle of duality are extended to the complex space-time and to bradyons, luxons and tachyons under the complex transformations. SeVeral characteristic features of the superluminal transformations and of tachyons are derived.
A bivariate space-time downscaler under space and time misalignment.
Berrocal, Veronica J; Gelfand, Alan E; Holland, David M
2010-12-01
Ozone and particulate matter PM(2.5) are co-pollutants that have long been associated with increased public health risks. Information on concentration levels for both pollutants come from two sources: monitoring sites and output from complex numerical models that produce concentration surfaces over large spatial regions. In this paper, we offer a fully-model based approach for fusing these two sources of information for the pair of co-pollutants which is computationally feasible over large spatial regions and long periods of time. Due to the association between concentration levels of the two environmental contaminants, it is expected that information regarding one will help to improve prediction of the other. Misalignment is an obvious issue since the monitoring networks for the two contaminants only partly intersect and because the collection rate for PM(2.5) is typically less frequent than that for ozone.Extending previous work in Berrocal et al. (2009), we introduce a bivariate downscaler that provides a flexible class of bivariate space-time assimilation models. We discuss computational issues for model fitting and analyze a dataset for ozone and PM(2.5) for the ozone season during year 2002. We show a modest improvement in predictive performance, not surprising in a setting where we can anticipate only a small gain.
Coding space-time stimulus dynamics in auditory brain maps
Directory of Open Access Journals (Sweden)
Yunyan eWang
2014-04-01
Full Text Available Sensory maps are often distorted representations of the environment, where ethologically-important ranges are magnified. The implication of a biased representation extends beyond increased acuity for having more neurons dedicated to a certain range. Because neurons are functionally interconnected, non-uniform representations influence the processing of high-order features that rely on comparison across areas of the map. Among these features are time-dependent changes of the auditory scene generated by moving objects. How sensory representation affects high order processing can be approached in the map of auditory space of the owl’s midbrain, where locations in the front are over-represented. In this map, neurons are selective not only to location but also to location over time. The tuning to space over time leads to direction selectivity, which is also topographically organized. Across the population, neurons tuned to peripheral space are more selective to sounds moving into the front. The distribution of direction selectivity can be explained by spatial and temporal integration on the non-uniform map of space. Thus, the representation of space can induce biased computation of a second-order stimulus feature. This phenomenon is likely observed in other sensory maps and may be relevant for behavior.
Super-nodal methods for space-time kinetics
Mertyurek, Ugur
The purpose of this research has been to develop an advanced Super-Nodal method to reduce the run time of 3-D core neutronics models, such as in the NESTLE reactor core simulator and FORMOSA nuclear fuel management optimization codes. Computational performance of the neutronics model is increased by reducing the number of spatial nodes used in the core modeling. However, as the number of spatial nodes decreases, the error in the solution increases. The Super-Nodal method reduces the error associated with the use of coarse nodes in the analyses by providing a new set of cross sections and ADFs (Assembly Discontinuity Factors) for the new nodalization. These so called homogenization parameters are obtained by employing consistent collapsing technique. During this research a new type of singularity, namely "fundamental mode singularity", is addressed in the ANM (Analytical Nodal Method) solution. The "Coordinate Shifting" approach is developed as a method to address this singularity. Also, the "Buckling Shifting" approach is developed as an alternative and more accurate method to address the zero buckling singularity, which is a more common and well known singularity problem in the ANM solution. In the course of addressing the treatment of these singularities, an effort was made to provide better and more robust results from the Super-Nodal method by developing several new methods for determining the transverse leakage and collapsed diffusion coefficient, which generally are the two main approximations in the ANM methodology. Unfortunately, the proposed new transverse leakage and diffusion coefficient approximations failed to provide a consistent improvement to the current methodology. However, improvement in the Super-Nodal solution is achieved by updating the homogenization parameters at several time points during a transient. The update is achieved by employing a refinement technique similar to pin-power reconstruction. A simple error analysis based on the relative
AdS-like spectrum of the asymptotically Goedel space-times
International Nuclear Information System (INIS)
Konoplya, R. A.; Zhidenko, A.
2011-01-01
A black hole immersed in a rotating universe, described by the Gimon-Hashimoto solution, is tested on stability against scalar field perturbations. Unlike the previous studies on perturbations of this solution, which dealt only with the limit of slow universe rotation j, we managed to separate variables in the perturbation equation for the general case of arbitrary rotation. This leads to qualitatively different dynamics of perturbations, because the exact effective potential does not allow for Schwarzschild-like asymptotic of the wave function in the form of purely outgoing waves. The Dirichlet boundary conditions are allowed instead, which result in a totally different spectrum of asymptotically Goedel black holes: the spectrum of quasinormal frequencies is similar to the one of asymptotically anti-de Sitter black holes. At large and intermediate overtones N, the spectrum is equidistant in N. In the limit of small black holes, quasinormal modes (QNMs) approach the normal modes of the empty Goedel space-time. There is no evidence of instability in the found frequencies, which supports the idea that the existence of closed timelike curves (CTCs) and the onset of instability correlate (if at all) not in a straightforward way.
Supersymmetric mechanics. Vol. 2. The attractor mechanism and space time singularities
International Nuclear Information System (INIS)
Bellucci, S.; Marrani, A.; Ferrara, S.
2006-01-01
This is the second volume in a series of books on the general theme of Supersymmetric Mechanics; the series is based on lectures and discussions held in 2005 and 2006 at the INFN-Laboratori Nazionali di Frascati. The first volume appears as Lect. Notes Physics, Vol. 698 ''Supersymmetric Mechanics, Vol.1: Supersymmetry, Noncommutativity and Matrix Models'' (2006) ISBN: 3-540-33313-4. The present extensive lecture supplies a pedagogical introduction, at the non-expert level, to the attractor mechanism in space-time singularities. In such a framework, supersymmetry seems to be related to dynamical systems with fixed points, describing the equilibrium state and the stability features of the thermodynamics of black holes. After a qualitative overview, explicit examples realizing the attractor mechanism are treated at some length; they include relevant cases of asymptotically flat, maximal and non-maximal, extended supergravities in 4 and 5 dimensions. A number of recent advances along various directions of research on the attractor mechanism are also given. (orig.)
International Nuclear Information System (INIS)
Beckwith, Andrew
2011-01-01
We make explicit an idea by Padmanabhan in DICE 2010, as to finding 'atoms of space-time' permitting a thermodynamic treatment of emergent structure similar to Gibbs treatment of statistical physics. That is, an ensemble of gravitons is used to give an 'atom' of space-time congruent with relic GW. The idea is to reduce the number of independent variables to get a simple emergent space-time structure of entropy. An electric field, based upon the cosmological Schwinger principle, is linked to relic heat flux, with entropy production tied in with candidates as to inflaton potentials. The effective electric field links with the Schwinger 1951s result of an E field leading to pairs of e + e - charges nucleated in space-time volume V · t. Note that in most inflationary models, the assumption is for a magnetic field, not an electric field. An electric field permits a kink-anti-kink construction of an emergent structure, which includes Glinka's recent pioneering approach to a Multiverse. Also an E field allows for an emergent relic particle frequency range between one and 100 GHz. The novel contribution is a relic E field, instead of a B field, in relic space-time 'atom' formation and vacuum nucleation of the same.
What have we learned from quantum field theory in curved space-time
International Nuclear Information System (INIS)
Fulling, S.A.
1984-01-01
The paper reviews the quantum field theory in curved space-time. Field quantization in gravitational backgrounds; particle creation by black holes; Hawking radiation; quantum field theory in curved space-time; covariant renormalization of the stress-energy-momentum tensor; quantum field theory and quantum gravity; are all discussed. (U.K.)
Exact solutions of space-time fractional EW and modified EW equations
International Nuclear Information System (INIS)
Korkmaz, Alper
2017-01-01
The bright soliton solutions and singular solutions are constructed for the space-time fractional EW and the space-time fractional modified EW (MEW) equations. Both equations are reduced to ordinary differential equations by the use of fractional complex transform (FCT) and properties of modified Riemann–Liouville derivative. Then, various ansatz method are implemented to construct the solutions for both equations.
Using adaptive antenna array in LTE with MIMO for space-time processing
Directory of Open Access Journals (Sweden)
Abdourahamane Ahmed Ali
2015-04-01
Full Text Available The actual methods of improvement the existent wireless transmission systems are proposed. Mathematical apparatus is considered and proved by models, graph of which are shown, using the adaptive array antenna in LTE with MIMO for space-time processing. The results show that improvements, which are joined with space-time processing, positively reflects on LTE cell size or on throughput
Quantum energy-momentum tensor in space-time with time-like killing vector
International Nuclear Information System (INIS)
Frolov, V.P.; Zel'nikov, A.I.
1987-01-01
An approximate expression for the vacuum and thermal average μν > ren of the stress-energy tensor of conformal massless fields in static Ricci-flat space-times is constructed. The application of this approximation to the space-time of a Schwarzschild black hole and its relation to the Page-Brown-Ottewill approximation are briefly discussed. (orig.)
Explicit Minkowski invariance and differential calculus in the quantum space-time
International Nuclear Information System (INIS)
Xu Zhan.
1991-11-01
In terms of the R-circumflex matrix of the quantum group SL q (2), the explicit Minkowski coordinate commutation relations in the four-dimensional quantum space-time are given, and the invariance of the Minkowski metric is shown. The differential calculus in this quantum space-time is discussed and the corresponding commutation relations are proposed. (author). 17 refs
On the electromagnetic field and the Teukolsky relations in arbitrary space-times
International Nuclear Information System (INIS)
Coll, B.; Ferrando, J.J.
1985-01-01
The relations on the electromagnetic field obtained by Teukolsky for type D, vacuum space-times are studied. The role played by the maxwellian geometry of the basic tetrad is shown. It is proved that Teukolsky relations are, generically, incomplete. Once completed, their generalization to arbitrary space-times is given [fr
Density perturbations due to the inhomogeneous discrete spatial structure of space-time
International Nuclear Information System (INIS)
Wolf, C.
1998-01-01
For the case that space-time permits an inhomogeneous discrete spatial structure due to varying gravitational fields or a foam-like structure of space-time, it is demonstrated that thermodynamic reasoning implies that matter-density perturbations will arise in the early universe
Energy in the Kantowski–Sachs space-time using teleparallel ...
Indian Academy of Sciences (India)
Energy in the Kantowski–Sachs space-time using teleparallel geometry ... Kantowski–Sachs metric; teleparallelism; gravitational energy. Abstract. The purpose of this paper is to examine the energy content of the inflationary Universe described by Kantowski–Sachs space-time in quasilocal approach of teleparallel gravity ...
On scattering of scalar waves in static space-times, particularly Schwarzschild
International Nuclear Information System (INIS)
Beig, R.
1982-01-01
This paper aims at laying foundations of a rigorous scattering theory for scalar waves in a static space-time. The treatment includes geometries which can be thought of as representing the exterior of a black hole. Schwarzschild space-time, as a particular example, is studied in more detail. (Auth.)
Is the shell-focusing singularity of Szekeres space-time visible?
International Nuclear Information System (INIS)
Nolan, Brien C; Debnath, Ujjal
2007-01-01
The visibility of the shell-focusing singularity in Szekeres space-time--which represents quasispherical dust collapse--has been studied on numerous occasions in the context of the cosmic censorship conjecture. The various results derived have assumed that there exist radial null geodesics in the space-time. We show that such geodesics do not exist in general, and so previous results on the visibility of the singularity are not generally valid. More precisely, we show that the existence of a radial geodesic in Szekeres space-time implies that the space-time is axially symmetric, with the geodesic along the polar direction (i.e. along the axis of symmetry). If there is a second nonparallel radial geodesic, then the space-time is spherically symmetric, and so is a Lemaitre-Tolman-Bondi space-time. For the case of the polar geodesic in an axially symmetric Szekeres space-time, we give conditions on the free functions (i.e. initial data) of the space-time which lead to visibility of the singularity along this direction. Likewise, we give a sufficient condition for censorship of the singularity. We point out the complications involved in addressing the question of visibility of the singularity both for nonradial null geodesics in the axially symmetric case and in the general (nonaxially symmetric) case, and suggest a possible approach
Theorizing Space-Time Relations in Education: The Concept of Chronotope
Ritella, Giuseppe; Ligorio, Maria Beatrice; Hakkarainen, Kai
2016-01-01
Due to ongoing cultural-historical transformations, the space-time of learning is radically changing, and theoretical conceptualizations are needed to investigate how such evolving space-time frames can function as a ground for learning. In this article, we argue that the concept of chronotope--from Greek chronos and topos, meaning time and…
Pseudo-Newtonian Equations for Evolution of Particles and Fluids in Stationary Space-times
Energy Technology Data Exchange (ETDEWEB)
Witzany, Vojtěch; Lämmerzahl, Claus, E-mail: vojtech.witzany@zarm.uni-bremen.de, E-mail: claus.laemmerzahl@zarm.uni-bremen.de [ZARM, Universität Bremen, Am Fallturm, D-28359 Bremen (Germany)
2017-06-01
Pseudo-Newtonian potentials are a tool often used in theoretical astrophysics to capture some key features of a black hole space-time in a Newtonian framework. As a result, one can use Newtonian numerical codes, and Newtonian formalism, in general, in an effective description of important astrophysical processes such as accretion onto black holes. In this paper, we develop a general pseudo-Newtonian formalism, which pertains to the motion of particles, light, and fluids in stationary space-times. In return, we are able to assess the applicability of the pseudo-Newtonian scheme. The simplest and most elegant formulas are obtained in space-times without gravitomagnetic effects, such as the Schwarzschild rather than the Kerr space-time; the quantitative errors are smallest for motion with low binding energy. Included is a ready-to-use set of fluid equations in Schwarzschild space-time in Cartesian and radial coordinates.
Natural world physical, brain operational, and mind phenomenal space-time
Fingelkurts, Andrew A.; Fingelkurts, Alexander A.; Neves, Carlos F. H.
2010-06-01
Concepts of space and time are widely developed in physics. However, there is a considerable lack of biologically plausible theoretical frameworks that can demonstrate how space and time dimensions are implemented in the activity of the most complex life-system - the brain with a mind. Brain activity is organized both temporally and spatially, thus representing space-time in the brain. Critical analysis of recent research on the space-time organization of the brain's activity pointed to the existence of so-called operational space-time in the brain. This space-time is limited to the execution of brain operations of differing complexity. During each such brain operation a particular short-term spatio-temporal pattern of integrated activity of different brain areas emerges within related operational space-time. At the same time, to have a fully functional human brain one needs to have a subjective mental experience. Current research on the subjective mental experience offers detailed analysis of space-time organization of the mind. According to this research, subjective mental experience (subjective virtual world) has definitive spatial and temporal properties similar to many physical phenomena. Based on systematic review of the propositions and tenets of brain and mind space-time descriptions, our aim in this review essay is to explore the relations between the two. To be precise, we would like to discuss the hypothesis that via the brain operational space-time the mind subjective space-time is connected to otherwise distant physical space-time reality.
Computation of the stability derivatives via CFD and the sensitivity equations
Lei, Guo-Dong; Ren, Yu-Xin
2011-04-01
The method to calculate the aerodynamic stability derivates of aircrafts by using the sensitivity equations is extended to flows with shock waves in this paper. Using the newly developed second-order cell-centered finite volume scheme on the unstructured-grid, the unsteady Euler equations and sensitivity equations are solved simultaneously in a non-inertial frame of reference, so that the aerodynamic stability derivatives can be calculated for aircrafts with complex geometries. Based on the numerical results, behavior of the aerodynamic sensitivity parameters near the shock wave is discussed. Furthermore, the stability derivatives are analyzed for supersonic and hypersonic flows. The numerical results of the stability derivatives are found in good agreement with theoretical results for supersonic flows, and variations of the aerodynamic force and moment predicted by the stability derivatives are very close to those obtained by CFD simulation for both supersonic and hypersonic flows.
Hsu, Jong-Ping
2013-01-01
Yang-Mills gravity is a new theory, consistent with experiments, that brings gravity back to the arena of gauge field theory and quantum mechanics in flat space-time. It provides solutions to long-standing difficulties in physics, such as the incompatibility between Einstein's principle of general coordinate invariance and modern schemes for a quantum mechanical description of nature, and Noether's 'Theorem II' which showed that the principle of general coordinate invariance in general relativity leads to the failure of the law of conservation of energy. Yang-Mills gravity in flat space-time a
International Nuclear Information System (INIS)
Sun, Wenjuan; Brown, Stephen; Flay, Nadia; McCarthy, Michael; McBride, John
2016-01-01
The use of x-ray computed tomography for dimensional measurements associated with engineering applications has flourished in recent years. However, error sources associated with the technology are not well understood. In this paper, a novel two-sphere reference sample has been developed and used to investigate the stability of the imaging system that consists of an x-ray tube and a detector. In contrast with other research work reported, this work considered relative positional variation along the x -, y - and z -axes. This sample is a significant improvement over the one sphere sample proposed previously, which can only be used to observe the stability of the imaging system along x - and y -axes. Temperature variations of different parts of the system have been monitored and the relationship between temperature variations and x-ray image stability has been studied. Other effects that may also influence the stability of the imaging system have been discussed. The proposed reference sample and testing method are transferable to other types of x-ray computed tomography systems, for example, systems with transmission targets and systems with sub-micrometre focal spots. (paper)
International Nuclear Information System (INIS)
Aboanber, A.E.; Hamada, Y.M.
2008-01-01
An extensive knowledge of the spatial power distribution is required for the design and analysis of different types of current-generation reactors, and that requires the development of more sophisticated theoretical methods. Therefore, the need to develop new methods for multidimensional transient reactor analysis still exists. The objective of this paper is to develop a computationally efficient numerical method for solving the multigroup, multidimensional, static and transient neutron diffusion kinetics equations. A generalized Runge-Kutta method has been developed for the numerical integration of the stiff space-time diffusion equations. The method is fourth-order accurate, using an embedded third-order solution to arrive at an estimate of the truncation error for automatic time step control. In addition, the A(α)-stability properties of the method are investigated. The analyses of two- and three-dimensional benchmark problems as well as static and transient problems, demonstrate that very accurate solutions can be obtained with assembly-sized spatial meshes. Preliminary numerical evaluations using two- and three-dimensional finite difference codes showed that the presented generalized Runge-Kutta method is highly accurate and efficient when compared with other optimized iterative numerical and conventional finite difference methods
Directory of Open Access Journals (Sweden)
Si-hao Tan
2012-01-01
Full Text Available We present an automatic framework combined space-time signal processing with Time Reversal electromagnetic (EM inversion for subsurface and through-wall multitarget imaging using electromagnetic waves. This framework is composed of a frequency-wavenumber (FK filter to suppress direct wave and medium bounce, a FK migration algorithm to automatically estimate the number of targets and identify target regions, which can be used to reduce the computational complexity of the following imaging algorithm, and a EM inversion algorithm using Time Reversal Multiple Signal Classification (TR-MUSIC to reconstruct hidden objects. The feasibility of the framework is demonstrated with simulated data generated by GPRMAX.
2015-11-01
diffusive tracer fluxes, directed normal to the tracer gradient [64], are generally equivalent to antisymmetric components in the effective diffusivity...tensor D∗, while the symmetric part of D∗ represents irreversible diffusive effects [83, 87, 39] directed down the tracer gradient . The mixing of eddy...provides an operational calculus in Hilbert space which yields powerful integral representations involving the Stieltjes measures displayed in equation
Space-Time Coded MC-CDMA: Blind Channel Estimation, Identifiability, and Receiver Design
Directory of Open Access Journals (Sweden)
Li Hongbin
2002-01-01
Full Text Available Integrating the strengths of multicarrier (MC modulation and code division multiple access (CDMA, MC-CDMA systems are of great interest for future broadband transmissions. This paper considers the problem of channel identification and signal combining/detection schemes for MC-CDMA systems equipped with multiple transmit antennas and space-time (ST coding. In particular, a subspace based blind channel identification algorithm is presented. Identifiability conditions are examined and specified which guarantee unique and perfect (up to a scalar channel estimation when knowledge of the noise subspace is available. Several popular single-user based signal combining schemes, namely the maximum ratio combining (MRC and the equal gain combining (EGC, which are often utilized in conventional single-transmit-antenna based MC-CDMA systems, are extended to the current ST-coded MC-CDMA (STC-MC-CDMA system to perform joint combining and decoding. In addition, a linear multiuser minimum mean-squared error (MMSE detection scheme is also presented, which is shown to outperform the MRC and EGC at some increased computational complexity. Numerical examples are presented to evaluate and compare the proposed channel identification and signal detection/combining techniques.
International Nuclear Information System (INIS)
Das, S.R.; Mukherji, S.
1994-01-01
We study black hole formation in a model of two dimensional dilaton gravity and 24 massless scalar fields with a boundary. We find the most general boundary condition consistent with perfect reflection of matter and the constraints. We show that in the semiclassical approximation and for the generic value of a parameter which characterizes the boundary conditions, the boundary starts receding to infinity at the speed of light whenever the total energy of the incoming matter flux exceeds a certain critical value. This is also the critical energy which marks the onset of black hole formation. We then compute the quantum fluctuations of the boundary and of the rescaled scalar curvature and show that as soon as the incoming energy exceeds this critical value, and asymptotic observer using normal time resolutions will always measure large quantum fluctuations of space-time near the horizon, even though the freely falling observer does not. This is an aspect of black hole complementarity relating directly to quantum gravity effects. (author). 30 refs, 4 figs
Fast Maximum-Likelihood Decoder for Quasi-Orthogonal Space-Time Block Code
Directory of Open Access Journals (Sweden)
Adel Ahmadi
2015-01-01
Full Text Available Motivated by the decompositions of sphere and QR-based methods, in this paper we present an extremely fast maximum-likelihood (ML detection approach for quasi-orthogonal space-time block code (QOSTBC. The proposed algorithm with a relatively simple design exploits structure of quadrature amplitude modulation (QAM constellations to achieve its goal and can be extended to any arbitrary constellation. Our decoder utilizes a new decomposition technique for ML metric which divides the metric into independent positive parts and a positive interference part. Search spaces of symbols are substantially reduced by employing the independent parts and statistics of noise. Symbols within the search spaces are successively evaluated until the metric is minimized. Simulation results confirm that the proposed decoder’s performance is superior to many of the recently published state-of-the-art solutions in terms of complexity level. More specifically, it was possible to verify that application of the new algorithms with 1024-QAM would decrease the computational complexity compared to state-of-the-art solution with 16-QAM.
OFDM Radar Space-Time Adaptive Processing by Exploiting Spatio-Temporal Sparsity
Energy Technology Data Exchange (ETDEWEB)
Sen, Satyabrata [ORNL
2013-01-01
We propose a sparsity-based space-time adaptive processing (STAP) algorithm to detect a slowly-moving target using an orthogonal frequency division multiplexing (OFDM) radar. We observe that the target and interference spectra are inherently sparse in the spatio-temporal domain. Hence, we exploit that sparsity to develop an efficient STAP technique that utilizes considerably lesser number of secondary data and produces an equivalent performance as the other existing STAP techniques. In addition, the use of an OFDM signal increases the frequency diversity of our system, as different scattering centers of a target resonate at different frequencies, and thus improves the target detectability. First, we formulate a realistic sparse-measurement model for an OFDM radar considering both the clutter and jammer as the interfering sources. Then, we apply a residual sparse-recovery technique based on the LASSO estimator to estimate the target and interference covariance matrices, and subsequently compute the optimal STAP-filter weights. Our numerical results demonstrate a comparative performance analysis of the proposed sparse-STAP algorithm with four other existing STAP methods. Furthermore, we discover that the OFDM-STAP filter-weights are adaptable to the frequency-variabilities of the target and interference responses, in addition to the spatio-temporal variabilities. Hence, by better utilizing the frequency variabilities, we propose an adaptive OFDM-waveform design technique, and consequently gain a significant amount of STAP-performance improvement.
Space-time statistics of the turbulence in the PRETEXT and TEXT tokamak edge plasmas
International Nuclear Information System (INIS)
Levinson, S.J.
1986-01-01
A study of the statistical space-time properties of the turbulence observed in the edge regions of the PRETEXT and the TEXT tokamaks are reported. Computer estimates of the particle-transport spectrum T(omega), and of the local wavenumber-frequency spectra S(K,omega) for poloidal (k/sub y/) and toroidal (k/sub z/) wavenumbers was determined. A conventional fast-Fourier-transform technique is used initially for the analyses of the potential and density fluctuations obtained from spatially fixed Langmuir-probe pairs. Measurements of the fluctuation-induced particle transport revealed that the particle flux is outward for both PRETEXT and TEXT, and it results primarily from the low-frequency, long-wavelength components of the turbulence. The S(K/sub y/, omega) spectra are dominated by low frequencies ( -1 ) and appear broadened about an approximately linear statistical dispersion relation, anti k(omega). The broadening is characterized by a spectral width sigma/sub k/(omega) (rms deviation about anti k(omega)). In PRETEXT, sigma/sub k/(omega) is of the order of anti k(omega), and the turbulence appears to propagate poloidally with an apparent mean phase velocity of 1-2 x 10 5 cm/s in the ion diamagnetic drift direction. In TEXT, a reversal in the phase velocity of the turbulence in the edge plasma was observed
Blind cooperative diversity using distributed space-time coding in block fading channels
Tourki, Kamel
2010-08-01
Mobile users with single antennas can still take advantage of spatial diversity through cooperative space-time encoded transmission. In this paper, we consider a scheme in which a relay chooses to cooperate only if its source-relay channel is of an acceptable quality and we evaluate the usefulness of relaying when the source acts blindly and ignores the decision of the relays whether they may cooperate or not. In our study, we consider the regenerative relays in which the decisions to cooperate are based on a signal-to-noise ratio (SNR) threshold and consider the impact of the possible erroneously detected and transmitted data at the relays. We derive the end-to-end bit-error rate (BER) expression and its approximation for binary phase-shift keying modulation and look at two power allocation strategies between the source and the relays in order to minimize the end-to-end BER at the destination for high SNR. Some selected performance results show that computer simulations based results coincide well with our analytical results. © 2010 IEEE.
Super-Orthogonal Space-Time Turbo Transmit Diversity for CDMA
Directory of Open Access Journals (Sweden)
Pieter G. W. van Rooyen
2005-05-01
Full Text Available Studies have shown that transmit and receive diversity employing a combination of multiple transmit-receive antennas (given ideal channel state information (CSI and independent fading between antenna pairs will potentially yield maximum achievable system capacity. In this paper, the concept of a layered super-orthogonal turbo transmit diversity (SOTTD for downlink direct-sequence code-division multiple-access (CDMA systems is explored. This open-loop transmit diversity technique improves the downlink performance by using a small number of antenna elements at the base station and a single antenna at the handset. In the proposed technique, low-rate super-orthogonal code-spread CDMA is married with code-division transmit diversity (CDTD. At the mobile receiver, space-time (ST RAKE CDTD processing is combined with iterative turbo code-spread decoding to yield large ST gains. The performance of the SOTTD system is compared with single- and multiantenna turbo-coded (TC CDTD systems evaluated over a frequency-selective Rayleigh fading channel. The evaluation is done both by means of analysis and computer simulations. The performance results illustrate the superior performance of SOTTD compared to TC CDTD systems over practically the complete useful capacity range of CDMA. It is shown that the performance degradation characteristic of TC CDTD at low system loads (due to the inherent TC error floor is alleviated by the SOTTD system.
Time-Resolved PIV for Space-Time Correlations in Hot Jets
Wernet, Mark P.
2007-01-01
Temporally Resolved Particle Image Velocimetry (TR-PIV) is being used to characterize the decay of turbulence in jet flows a critical element for understanding the acoustic properties of the flow. A TR-PIV system, developed in-house at the NASA Glenn Research Center, is capable of acquiring planar PIV image frame pairs at up to 10 kHz. The data reported here were collected at Mach numbers of 0.5 and 0.9 and at temperature ratios of 0.89 and 1.76. The field of view of the TR-PIV system covered 6 nozzle diameters along the lip line of the 50.8 mm diameter jet. The cold flow data at Mach 0.5 were compared with hotwire anemometry measurements in order to validate the new TR-PIV technique. The axial turbulence profiles measured across the shear layer using TR-PIV were thinner than those measured using hotwire anemometry and remained centered along the nozzle lip line. The collected TR-PIV data illustrate the differences in the single point statistical flow properties of cold and hot jet flows. The planar, time-resolved velocity records were then used to compute two-point space-time correlations of the flow at the Mach 0.9 flow condition. The TR-PIV results show that there are differences in the convective velocity and growth rate of the turbulent structures between cold and hot flows at the same Mach number.
2009-07-01
"Considerable data exists for soils that were tested and documented, both for native properties and : properties with pozzolan stabilization. While the data exists there was no database for the Nebraska : Department of Roads to retrieve this data for...
Computing Fault-Containment Times of Self-Stabilizing Algorithms Using Lumped Markov Chains
Directory of Open Access Journals (Sweden)
Volker Turau
2018-05-01
Full Text Available The analysis of self-stabilizing algorithms is often limited to the worst case stabilization time starting from an arbitrary state, i.e., a state resulting from a sequence of faults. Considering the fact that these algorithms are intended to provide fault tolerance in the long run, this is not the most relevant metric. A common situation is that a running system is an a legitimate state when hit by a single fault. This event has a much higher probability than multiple concurrent faults. Therefore, the worst case time to recover from a single fault is more relevant than the recovery time from a large number of faults. This paper presents techniques to derive upper bounds for the mean time to recover from a single fault for self-stabilizing algorithms based on Markov chains in combination with lumping. To illustrate the applicability of the techniques they are applied to a new self-stabilizing coloring algorithm.
We live in the quantum 4-dimensional Minkowski space-time
Hwang, W-Y. Pauchy
2015-01-01
We try to define "our world" by stating that "we live in the quantum 4-dimensional Minkowski space-time with the force-fields gauge group $SU_c(3) \\times SU_L(2) \\times U(1) \\times SU_f(3)$ built-in from the outset". We begin by explaining what "space" and "time" are meaning for us - the 4-dimensional Minkowski space-time, then proceeding to the quantum 4-dimensional Minkowski space-time. In our world, there are fields, or, point-like particles. Particle physics is described by the so-called ...
Thermodynamics in Curved Space-Time and Its Application to Holography
Directory of Open Access Journals (Sweden)
Yong Xiao
2015-03-01
Full Text Available The thermodynamic behaviors of a system living in a curved space-time are different from those of a system in a flat space-time. We have investigated the thermodynamics for a system consisting of relativistic massless bosons. We show that a strongly curved metric will produce a large enhancement of the degrees of freedom in the formulae of energy and entropy of the system, as a comparison to the case in a flat space-time. We are mainly concerned with its implications to holography, including the derivations of holographic entropy and holographic screen.
Hopper, Richard A; Sandercoe, Gavin; Woo, Albert; Watts, Robyn; Kelley, Patrick; Ettinger, Russell E; Saltzman, Babette
2010-11-01
Le Fort III distraction requires generation of bone in the pterygomaxillary region. The authors performed retrospective digital analysis on temporal fine-cut computed tomographic images to quantify both radiographic evidence of pterygomaxillary region bone formation and relative maxillary stability. Fifteen patients with syndromic midface hypoplasia were included in the study. The average age of the patients was 8.7 years; 11 had either Crouzon or Apert syndrome. The average displacement of the maxilla during distraction was 16.2 mm (range, 7 to 31 mm). Digital analysis was performed on fine-cut computed tomographic scans before surgery, at device removal, and at annual follow-up. Seven patients also had mid-consolidation computed tomographic scans. Relative maxillary stability and density of radiographic bone in the pterygomaxillary region were calculated between each scan. There was no evidence of clinically significant maxillary relapse, rotation, or growth between the end of consolidation and 1-year follow-up, other than a relatively small 2-mm subnasal maxillary vertical growth. There was an average radiographic ossification of 0.5 mm/mm advancement at the time of device removal, with a 25th percentile value of 0.3 mm/mm. The time during consolidation that each patient reached the 25th percentile of pterygomaxillary region bone density observed in this series of clinically stable advancements ranged from 1.3 to 9.8 weeks (average, 3.7 weeks). There was high variability in the amount of bone formed in the pterygomaxillary region associated with clinical stability of the advanced Le Fort III segment. These data suggest that a subsection of patients generate the minimal amount of pterygomaxillary region bone formation associated with advancement stability as early as 4 weeks into consolidation.
Computational study of elements of stability of a four-helix bundle protein biosurfactant
Schaller, Andrea; Connors, Natalie K.; Dwyer, Mirjana Dimitrijev; Oelmeier, Stefan A.; Hubbuch, Jürgen; Middelberg, Anton P. J.
2015-01-01
Biosurfactants are surface-active molecules produced principally by microorganisms. They are a sustainable alternative to chemically-synthesized surfactants, having the advantages of being non-toxic, highly functional, eco-friendly and biodegradable. However they are currently only used in a few industrial products due to costs associated with production and purification, which exceed those for commodity chemical surfactants. DAMP4, a member of a four-helix bundle biosurfactant protein family, can be produced in soluble form and at high yield in Escherichia coli, and can be recovered using a facile thermal phase-separation approach. As such, it encompasses an interesting synergy of biomolecular and chemical engineering with prospects for low-cost production even for industrial sectors. DAMP4 is highly functional, and due to its extraordinary thermal stability it can be purified in a simple two-step process, in which the combination of high temperature and salt leads to denaturation of all contaminants, whereas DAMP4 stays stable in solution and can be recovered by filtration. This study aimed to characterize and understand the fundamental drivers of DAMP4 stability to guide further process and surfactant design studies. The complementary use of experiments and molecular dynamics simulation revealed a broad pH and temperature tolerance for DAMP4, with a melting point of 122.4 °C, suggesting the hydrophobic core as the major contributor to thermal stability. Simulation of systematically created in silico variants of DAMP4 showed an influence of number and location of hydrophilic mutations in the hydrophobic core on stability, demonstrating a tolerance of up to three mutations before a strong loss in stability occurred. The results suggest a consideration of a balance of stability, functionality and kinetics for new designs according to their application, aiming for maximal functionality but at adequate stability to allow for cost-efficient production using thermal
Masso, Majid; Vaisman, Iosif I
2008-09-15
Accurate predictive models for the impact of single amino acid substitutions on protein stability provide insight into protein structure and function. Such models are also valuable for the design and engineering of new proteins. Previously described methods have utilized properties of protein sequence or structure to predict the free energy change of mutants due to thermal (DeltaDeltaG) and denaturant (DeltaDeltaG(H2O)) denaturations, as well as mutant thermal stability (DeltaT(m)), through the application of either computational energy-based approaches or machine learning techniques. However, accuracy associated with applying these methods separately is frequently far from optimal. We detail a computational mutagenesis technique based on a four-body, knowledge-based, statistical contact potential. For any mutation due to a single amino acid replacement in a protein, the method provides an empirical normalized measure of the ensuing environmental perturbation occurring at every residue position. A feature vector is generated for the mutant by considering perturbations at the mutated position and it's ordered six nearest neighbors in the 3-dimensional (3D) protein structure. These predictors of stability change are evaluated by applying machine learning tools to large training sets of mutants derived from diverse proteins that have been experimentally studied and described. Predictive models based on our combined approach are either comparable to, or in many cases significantly outperform, previously published results. A web server with supporting documentation is available at http://proteins.gmu.edu/automute.
Worrich, Anja; König, Sara; Banitz, Thomas; Centler, Florian; Frank, Karin; Kästner, Matthias; Miltner, Anja; Thullner, Martin; Wick, Lukas
2015-04-01
Although bacterial degraders in soil are commonly exposed to fluctuating environmental conditions, the functional performance of the biodegradation processes can often be maintained by resistance and resilience mechanisms. However, there is still a gap in the mechanistic understanding of key factors contributing to the stability of such an ecosystem service. Therefore we developed an integrated approach combining microcosm experiments, simulation models and ecological theory to directly make use of the strengths of these disciplines. In a continuous interplay process, data, hypotheses, and central questions are exchanged between disciplines to initiate new experiments and models to ultimately identify buffer mechanisms and factors providing functional stability. We focus on drying and rewetting-cycles in soil ecosystems, which are a major abiotic driver for bacterial activity. Functional recovery of the system was found to depend on different spatial processes in the computational model. In particular, bacterial motility is a prerequisite for biodegradation if either bacteria or substrate are heterogeneously distributed. Hence, laboratory experiments focussing on bacterial dispersal processes were conducted and confirmed this finding also for functional resistance. Obtained results will be incorporated into the model in the next step. Overall, the combination of computational modelling and laboratory experiments identified spatial processes as the main driving force for functional stability in the considered system, and has proved a powerful methodological approach.
Fermi field and Dirac oscillator in a Som-Raychaudhuri space-time
de Montigny, Marc; Zare, Soroush; Hassanabadi, Hassan
2018-05-01
We investigate the relativistic dynamics of a Dirac field in the Som-Raychaudhuri space-time, which is described by a Gödel-type metric and a stationary cylindrical symmetric solution of Einstein field equations for a charged dust distribution in rigid rotation. In order to analyze the effect of various physical parameters of this space-time, we solve the Dirac equation in the Som-Raychaudhuri space-time and obtain the energy levels and eigenfunctions of the Dirac operator by using the Nikiforov-Uvarov method. We also examine the behaviour of the Dirac oscillator in the Som-Raychaudhuri space-time, in particular, the effect of its frequency and the vorticity parameter.
Blind cooperative diversity using distributed space-time coding in block fading channels
Tourki, Kamel; Alouini, Mohamed-Slim; Deneire, Luc
2010-01-01
Mobile users with single antennas can still take advantage of spatial diversity through cooperative space-time encoded transmission. In this paper, we consider a scheme in which a relay chooses to cooperate only if its source-relay channel
Adaptive Multi-Layered Space-Time Block Coded Systems in Wireless Environments
Al-Ghadhban, Samir
2014-01-01
© 2014, Springer Science+Business Media New York. Multi-layered space-time block coded systems (MLSTBC) strike a balance between spatial multiplexing and transmit diversity. In this paper, we analyze the block error rate performance of MLSTBC
Methods of computing steady-state voltage stability margins of power systems
Chow, Joe Hong; Ghiocel, Scott Gordon
2018-03-20
In steady-state voltage stability analysis, as load increases toward a maximum, conventional Newton-Raphson power flow Jacobian matrix becomes increasingly ill-conditioned so power flow fails to converge before reaching maximum loading. A method to directly eliminate this singularity reformulates the power flow problem by introducing an AQ bus with specified bus angle and reactive power consumption of a load bus. For steady-state voltage stability analysis, the angle separation between the swing bus and AQ bus can be varied to control power transfer to the load, rather than specifying the load power itself. For an AQ bus, the power flow formulation is only made up of a reactive power equation, thus reducing the size of the Jacobian matrix by one. This reduced Jacobian matrix is nonsingular at the critical voltage point, eliminating a major difficulty in voltage stability analysis for power system operations.
Stationary axisymmetric four dimensional space-time endowed with Einstein metric
International Nuclear Information System (INIS)
Hasanuddin; Azwar, A.; Gunara, B. E.
2015-01-01
In this paper, we construct Ernst equation from vacuum Einstein field equation for both zero and non-zero cosmological constant. In particular, we consider the case where the space-time admits axisymmetric using Boyer-Lindquist coordinates. This is called Kerr-Einstein solution describing a spinning black hole. Finally, we give a short discussion about the dynamics of photons on Kerr-Einstein space-time
International Nuclear Information System (INIS)
Hawking, S.W.; King, A.R.; McCarthy, P.J.
1976-01-01
A new topology is proposed for strongly causal space--times. Unlike the standard manifold topology (which merely characterizes continuity properties), the new topology determines the causal, differential, and conformal structures of space--time. The topology is more appealing, physical, and manageable than the topology previously proposed by Zeeman for Minkowski space. It thus seems that many calculations involving the above structures may be made purely topological
The separating topology for the space-times of general relativity
International Nuclear Information System (INIS)
Lindstroem, U.
1977-08-01
The separating topology, first suggested by Zeeman, is defined for the space-times of general relativity. It is defined by a basis. A number of properties are derived. The topology induces the ordinary Euclidean topology on space-like hypersurfaces as well as on timelike curves and the discrete topology on null-cones. The group of auto-homeomorphisms is found to be the group of smooth conformal diffeomorphisms if the space-time is strongly causal. (author)
Simple model of variation of the signature of a space-time metric
International Nuclear Information System (INIS)
Konstantinov, M.Yu.
2004-01-01
The problem on the changes in the space-time signature metrics is discussed. The simple model, wherein the space-time metrics signature is determined by the nonlinear scalar field, is proposed. It is shown that both classical and quantum description of changes in the metrics signature is possible within the frames of the considered model; the most characteristic peculiarities and variations of the classical and quantum descriptions are also briefly noted [ru
Entropy of space-time outcome in a movement speed-accuracy task.
Hsieh, Tsung-Yu; Pacheco, Matheus Maia; Newell, Karl M
2015-12-01
The experiment reported was set-up to investigate the space-time entropy of movement outcome as a function of a range of spatial (10, 20 and 30 cm) and temporal (250-2500 ms) criteria in a discrete aiming task. The variability and information entropy of the movement spatial and temporal errors considered separately increased and decreased on the respective dimension as a function of an increment of movement velocity. However, the joint space-time entropy was lowest when the relative contribution of spatial and temporal task criteria was comparable (i.e., mid-range of space-time constraints), and it increased with a greater trade-off between spatial or temporal task demands, revealing a U-shaped function across space-time task criteria. The traditional speed-accuracy functions of spatial error and temporal error considered independently mapped to this joint space-time U-shaped entropy function. The trade-off in movement tasks with joint space-time criteria is between spatial error and timing error, rather than movement speed and accuracy. Copyright © 2015 Elsevier B.V. All rights reserved.
A Note on the Problem of Proper Time in Weyl Space-Time
Avalos, R.; Dahia, F.; Romero, C.
2018-02-01
We discuss the question of whether or not a general Weyl structure is a suitable mathematical model of space-time. This is an issue that has been in debate since Weyl formulated his unified field theory for the first time. We do not present the discussion from the point of view of a particular unification theory, but instead from a more general standpoint, in which the viability of such a structure as a model of space-time is investigated. Our starting point is the well known axiomatic approach to space-time given by Elhers, Pirani and Schild (EPS). In this framework, we carry out an exhaustive analysis of what is required for a consistent definition for proper time and show that such a definition leads to the prediction of the so-called "second clock effect". We take the view that if, based on experience, we were to reject space-time models predicting this effect, this could be incorporated as the last axiom in the EPS approach. Finally, we provide a proof that, in this case, we are led to a Weyl integrable space-time as the most general structure that would be suitable to model space-time.
Some aspects of quantum field theory in non-Minkowskian space-times
International Nuclear Information System (INIS)
Toms, D.J.
1980-01-01
Several aspects of quantum field theory in space-times which are different from Minkowski space-time, either because of the presence of a non-zero curvature or as a consequence of the topology of the manifold, are discussed. The Casimir effect is a quantum field theory in a space-time which has a different topology. A short review of some of its popular derivations is presented with comments. Renormalization of interacting scalar field theories in a flat space-time with a non-Minkowskian topology is considered. The presence of a non-trivial topology can lead to additional non-local divergent terms in the Schwinger-Dyson equations for a general scalar field theory; however, the theory may be renormalized with the same choice of counterterms as in Minkowski space-time. Propagators can develop poles corresponding to the generation of a topological mass. Zeta-function regularization is shown to fit naturally into the functional approach to the effective potential. This formalism is used to calculate the effective potential for some scalar field theories in non-Minkowskian space-times. Topological mass generation is discussed, and it is shown how radiative corrections can lead to spontaneous symmetry breaking. One- and two-loop contributions to the vacuum energy density are obtained for both massless and massive fields. In the massive case the role of renormalization in removing non-local divergences is discussed
Jo, Byung Wan; Jo, Jun Ho; Khan, Rana Muhammad Asad; Kim, Jung Hoon; Lee, Yun Sung
2018-05-23
Structure Health Monitoring is a topic of great interest in port structures due to the ageing of structures and the limitations of evaluating structures. This paper presents a cloud computing-based stability evaluation platform for a pier type port structure using Fiber Bragg Grating (FBG) sensors in a system consisting of a FBG strain sensor, FBG displacement gauge, FBG angle meter, gateway, and cloud computing-based web server. The sensors were installed on core components of the structure and measurements were taken to evaluate the structures. The measurement values were transmitted to the web server via the gateway to analyze and visualize them. All data were analyzed and visualized in the web server to evaluate the structure based on the safety evaluation index (SEI). The stability evaluation platform for pier type port structures involves the efficient monitoring of the structures which can be carried out easily anytime and anywhere by converging new technologies such as cloud computing and FBG sensors. In addition, the platform has been successfully implemented at “Maryang Harbor” situated in Maryang-Meyon of Korea to test its durability.
International Nuclear Information System (INIS)
Rovere, Florian; Mayrhofer, Paul H; Music, Denis; Ershov, Sergey; Baben, Moritz to; Schneider, Jochen M; Fuss, Hans-Gerd
2010-01-01
The phase stability of Al-containing cubic transition metal (TM) nitrides, where Al substitutes for TM (i.e. TM 1-x Al x N), is studied as a function of the TM valence electron concentration (VEC). X-ray diffraction and thermal analyses data of magnetron sputtered Ti 1-x Al x N, V 1-x Al x N and Cr 1-x Al x N films indicate increasing phase stability of cubic TM 1-x Al x N at larger Al contents and higher temperatures with increasing TM VEC. These experimental findings can be understood based on first principle investigations of ternary cubic TM 1-x Al x N with TM = Sc, Ti, V, Cr, Y, Zr and Nb where the TM VEC and the lattice strain are systematically varied. However, our experimental data indicate that, in addition to the decomposition energetics (cubic TM 1-x Al x N → cubic TMN + hexagonal AlN), future stability models have to include nitrogen release as one of the mechanisms that critically determine the overall phase stability of TM 1-x Al x N.
Computationally Efficient Transient Stability Modeling of multi-terminal VSC-HVDC
DEFF Research Database (Denmark)
van der Meer, Arjen A; Rueda-Torres, José; Silva, Filipe Miguel Faria da
2016-01-01
This paper studies the inclusion of averaged VSC-based grid interfaces and HVDC networks into stability type simulations, and compares the accuracy and speed of three multi-terminal DC dynamic models: 1) a state-space based model, 2) a multi-rate improved model, and 3) a reduced-order model...
Bakshi, Neil K; Jameel, Omar F; Merrill, Zachary F; Debski, Richard E; Sekiya, Jon K
2016-08-01
This study compared the amount of glenohumeral abduction during arm abduction in the affected and unaffected shoulders of 3 groups of patients with shoulder instability: failed surgical stabilization, successful surgical stabilization, and unstable shoulder with no prior surgical intervention. All patients underwent bilateral shoulder computed tomography scans in 3 positions: 0° of abduction and 0° of external rotation (0-0 position), 30° of abduction and 30° of external rotation (30-30 position), and arms maximally abducted (overhead position). Three-dimensional computed tomography reconstruction was performed for both shoulders in all 3 positions. A specialized coordinate system marked specific points and directions on the humerus and glenoid of each model. These coordinates were used to calculate the glenohumeral abduction for the normal and affected sides in the 0-0, 30-30, and overhead positions. Thirty-nine patients with shoulder instability were included, of whom 14 had failed surgical repairs, 10 had successful surgical repairs, and 15 had unstable shoulders with no prior surgical intervention. In the overhead position, patients with failed surgical intervention had significantly less glenohumeral abduction in the failed shoulder (95.6° ± 12.7°) compared with the normal shoulder (101.5° ± 12.4°, P = .02). Patients with successfully stabilized shoulders had significantly less glenohumeral abduction in the successfully stabilized shoulder (93.6° ± 10.8°) compared with the normal shoulder (102.1° ± 12.5°, P = .03). Unstable shoulders with no prior surgical intervention (102.1° ± 10.3°) did not differ when compared with the normal shoulders (101.9° ± 10.9°, P = .95). Surgical intervention, regardless of its success, limits the amount of abduction at the glenohumeral joint. Level III, retrospective comparative study. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Gottlieb, I.; Agop, M.; Jarcau, M.
2004-01-01
One builds the vacuum metrics of the stationary electromagnetic field through the complex potential model. There are thus emphasized both a variational principle, independent on the Ricci tensor, and some internal symmetries of the vacuum solutions. One shows that similar results may be obtained using the Barbiliant's group. By analytical continuation of a Barbilian transformation the link between the fixed points of the modular groups of the vacuum and the golden mean PHI=(1/(1+PHI))=(√5-1)/2 of ε (∞) space-time is established. Finally, a Cantorian fractal axiomatic model of the space-time is presented. The model is explained using a set of coupled equations which may describe the self organizing processes at the solid-liquid, plasma-plasma, and superconductor-superconductor interfaces
Gonzalez-Mestres, Luis
2014-04-01
Planck and other recent data in Cosmology and Particle Physics can open the way to controversial analyses concerning the early Universe and its possible ultimate origin. Alternatives to standard cosmology include pre-Big Bang approaches, new space-time geometries and new ultimate constituents of matter. Basic issues related to a possible new cosmology along these lines clearly deserve further exploration. The Planck collaboration reports an age of the Universe t close to 13.8 Gyr and a present ratio H between relative speeds and distances at cosmic scale around 67.3 km/s/Mpc. The product of these two measured quantities is then slightly below 1 (about 0.95), while it can be exactly 1 in the absence of matter and cosmological constant in patterns based on the spinorial space-time we have considered in previous papers. In this description of space-time we first suggested in 1996-97, the cosmic time t is given by the modulus of a SU(2) spinor and the Lundmark-Lemaître-Hubble (LLH) expansion law turns out to be of purely geometric origin previous to any introduction of standard matter and relativity. Such a fundamental geometry, inspired by the role of half-integer spin in Particle Physics, may reflect an equilibrium between the dynamics of the ultimate constituents of matter and the deep structure of space and time. Taking into account the observed cosmic acceleration, the present situation suggests that the value of 1 can be a natural asymptotic limit for the product H t in the long-term evolution of our Universe up to possible small corrections. In the presence of a spinorial space-time geometry, no ad hoc combination of dark matter and dark energy would in any case be needed to get an acceptable value of H and an evolution of the Universe compatible with observation. The use of a spinorial space-time naturally leads to unconventional properties for the space curvature term in Friedmann-like equations. It therefore suggests a major modification of the standard
Current densities in a space-time-dependent and CP-violating Higgs background in the adiabatic limit
International Nuclear Information System (INIS)
Comelli, D.; Pietroni, M.; Riotto, A.
1996-01-01
Motivated by cosmological applications such as electroweak baryogenesis, we develop a field theoretic approach to the computation of particle currents on a space-time-dependent and CP-violating Higgs background in the adiabatic limit. We consider the standard model with two Higgs doublets and CP violation in the scalar sector, and compute both fermionic and Higgs currents by means of an expansion in the background fields describing the profile of the bubble wall. We discuss the gauge dependence of the results and the renormalization of the current operators, showing that in the limit of local equilibrium, no extra renormalization conditions are needed in order to specify the system completely. copyright 1996 The American Physical Society
International Nuclear Information System (INIS)
Chen, G.S.; Christenson, J.M.
1985-01-01
In this paper, the authors present some initial results from an investigation of the application of a locally one-dimensional (LOD) finite difference method to the solution of the two-dimensional, two-group reactor kinetics equations. Although the LOD method is relatively well known, it apparently has not been previously applied to the space-time kinetics equations. In this investigation, the LOD results were benchmarked against similar computational results (using the same computing environment, the same programming structure, and the same sample problems) obtained by the TWIGL program. For all of the problems considered, the LOD method provided accurate results in one-half to one-eight of the time required by the TWIGL program
Lag screw stabilization of a cervical vertebral fracture by use of computed tomography in a horse
International Nuclear Information System (INIS)
Barnes, H.G.; Tucker, R.L.; Grant, B.D.; Roberts, G.D.; Prades, M.
1995-01-01
A traumatic fracture of C2 was diagnosed radiographically in a 1-year-old German Warm-blood stallion. Fracture configuration was difficult to see on survey radiographs. Computed tomography yielded a more accurate assessment of the fracture and facilitated fracture repair with cortical lag screws. Precise screw placement, to avoid spinal cord damage, was obtained by use of computed tomography. Follow-up radiography revealed normal bone healing, and the horse was in dressage schooling 24 months after surgery
Time Resolved PIV for Space-Time Correlations in Hot Jets
Wernet, Mark P.
2007-01-01
Temporally Resolved Particle Image Velocimetry (TR-PIV) is the newest and most exciting tool recently developed to support our continuing efforts to characterize and improve our understanding of the decay of turbulence in jet flows -- a critical element for understanding the acoustic properties of the flow. A new TR-PIV system has been developed at the NASA Glenn Research Center which is capable of acquiring planar PIV image frame pairs at up to 25 kHz. The data reported here were collected at Mach numbers of 0.5 and 0.9 and at temperature ratios of 0.89 and 1.76. The field of view of the TR-PIV system covered 6 nozzle diameters along the lip line of the 50.8 mm diameter jet. The cold flow data at Mach 0.5 were compared with hotwire anemometry measurements in order to validate the new TR-PIV technique. The axial turbulence profiles measured across the shear layer using TR-PIV were thinner than those measured using hotwire anemometry and remained centered along the nozzle lip line. The collected TR-PIV data illustrate the differences in the single point statistical flow properties of cold and hot jet flows. The planar, time-resolved velocity records were then used to compute two-point space-time correlations of the flow at the Mach 0.9 flow condition. The TR-PIV results show that there are differences in the convective velocity and growth rate of the turbulent structures between cold and hot flows at the same Mach number
DEFF Research Database (Denmark)
Olesen, Solveig Gaarn; Hammerum, Steen
2009-01-01
It is generally expected that the hydrogen bond strength in a D-H-A adduct is predicted by the difference between the proton affinities of D and A, measured by the adduct stabilization, and demonstrated by the IR redshift of the D-H bond stretching vibrational frequency. These criteria do...... not always yield consistent predictions, as illustrated by the hydrogen bonds formed by the E and Z OH groups of protonated carboxylic acids. The delta-PA and the stabilization of a series of hydrogen bonded adducts indicate that the E OH group forms the stronger hydrogen bonds, whereas the bond length...... carboxylic acids are different. The OH bond length and IR redshift afford the better measure of hydrogen bond strength....
Tveito, Aslak; Skavhaug, Ola; Lines, Glenn T; Artebrant, Robert
2011-08-01
Instabilities in the electro-chemical resting state of the heart can generate ectopic waves that in turn can initiate arrhythmias. We derive methods for computing the resting state for mathematical models of the electro-chemical process underpinning a heartbeat, and we estimate the stability of the resting state by invoking the largest real part of the eigenvalues of a linearized model. The implementation of the methods is described and a number of numerical experiments illustrate the feasibility of the methods. In particular, we test the methods for problems where we can compare the solutions with analytical results, and problems where we have solutions computed by independent software. The software is also tested for a fairly realistic 3D model. Copyright © 2011 Elsevier Ltd. All rights reserved.
Computer Modeling of Radiative Transfer in Hybrid-Stabilized Argon–Water Electric Arc
Czech Academy of Sciences Publication Activity Database
Jeništa, Jiří; Takana, H.; Nishiyama, H.; Křenek, Petr; Bartlová, M.; Aubrecht, V.
2011-01-01
Roč. 39, č. 11 (2011), s. 2892-2893 ISSN 0093-3813 Institutional research plan: CEZ:AV0Z20430508 Keywords : Divergence of radiation flux * hybrid-stabilized electric arc * mass flow rate * partial characteristics * radiation flux Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.174, year: 2011 http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=27
Stability of Quantum Loops and Exchange Operations in the Construction of Quantum Computation Gates
International Nuclear Information System (INIS)
Bermúdez, D; Delgado, F
2017-01-01
Quantum information and quantum computation is a rapidly emergent field where quantum systems and their applications play a central role. In the gate version of quantum computation, the construction of universal quantum gates to manipulate quantum information is currently an intensive arena for quantum engineering. Specific properties of systems should be able to reproduce such idealized gates imitating the classically inspired computational gates. Recently, for magnetic systems driven by the bipartite Heisenberg-Ising model a universal set of gates has been realized, an alternative easy design for the Boykin set but using the Bell states as grammar. Exact control can be then used to construct specific prescriptions to achieve those gates. Physical parameters impose a challenge in the gate control. This work analyzes, based on the worst case quantum fidelity, the associated instability for the proposed set of gates. An strong performance is found in those gates for the most of quantum states involved. (paper)
McQuoid, Julia; Jowsey, Tanisha; Talaulikar, Girish
2017-06-01
Stable routines are key to successful illness self-management for the growing number of people living with chronic illness around the world. Yet, the influence of chronically ill individuals' everyday contexts in supporting routines is poorly understood. This paper takes a space-time geographical approach to explore the everyday space-time contexts and routines of individuals with chronic kidney disease (CKD). We ask: what is the relationship between renal patients' space-time contexts and their ability to establish and maintain stable routines, and, what role does health service access play in this regard? We draw from a qualitative case study of 26 individuals with CKD in Australia. Data comprised self-reported two day participant diaries and semi-structured interviews. Thematic analysis of interview transcripts was guided by an inductive-deductive approach. We examined the embeddedness of routines within the space-time contexts of participants' everyday lives. We found that participants' everyday space-time contexts were highly complex, especially for those receiving dialysis and/or employed, making routines difficult to establish and vulnerable to disruption. Health service access helped shape participants' everyday space-time contexts, meaning that incidences of unpredictability in accessing health services set-off 'ripple effects' within participants' space-time contexts, disrupting routines and making everyday life negotiation more difficult. The ability to absorb ripple effects from unpredictable health services without disrupting routines varied by space-time context. Implications of these findings for the deployment of the concept of routine in health research, the framing of patient success in self-managing illness, and health services design are discussed. In conclusion, efforts to understand and support individuals in establishing and maintaining routines that support health and wellbeing can benefit from approaches that contextualise and de
Computation of focal values and stability analysis of 4-dimensional systems
Directory of Open Access Journals (Sweden)
Bo Sang
2015-08-01
Full Text Available This article presents a recursive formula for computing the n-th singular point values of a class of 4-dimensional autonomous systems, and establishes the algebraic equivalence between focal values and singular point values. The formula is linear and then avoids complicated integrating operations, therefore the calculation can be carried out by computer algebra system such as Maple. As an application of the formula, bifurcation analysis is made for a quadratic system with a Hopf equilibrium, which can have three small limit cycles around an equilibrium point. The theory and methodology developed in this paper can be used for higher-dimensional systems.
Differential Space-Time Block Code Modulation for DS-CDMA Systems
Directory of Open Access Journals (Sweden)
Liu Jianhua
2002-01-01
Full Text Available A differential space-time block code (DSTBC modulation scheme is used to improve the performance of DS-CDMA systems in fast time-dispersive fading channels. The resulting scheme is referred to as the differential space-time block code modulation for DS-CDMA (DSTBC-CDMA systems. The new modulation and demodulation schemes are especially studied for the down-link transmission of DS-CDMA systems. We present three demodulation schemes, referred to as the differential space-time block code Rake (D-Rake receiver, differential space-time block code deterministic (D-Det receiver, and differential space-time block code deterministic de-prefix (D-Det-DP receiver, respectively. The D-Det receiver exploits the known information of the spreading sequences and their delayed paths deterministically besides the Rake type combination; consequently, it can outperform the D-Rake receiver, which employs the Rake type combination only. The D-Det-DP receiver avoids the effect of intersymbol interference and hence can offer better performance than the D-Det receiver.
Is space-time symmetry a suitable generalization of parity-time symmetry?
International Nuclear Information System (INIS)
Amore, Paolo; Fernández, Francisco M.; Garcia, Javier
2014-01-01
We discuss space-time symmetric Hamiltonian operators of the form H=H 0 +igH ′ , where H 0 is Hermitian and g real. H 0 is invariant under the unitary operations of a point group G while H ′ is invariant under transformation by elements of a subgroup G ′ of G. If G exhibits irreducible representations of dimension greater than unity, then it is possible that H has complex eigenvalues for sufficiently small nonzero values of g. In the particular case that H is parity-time symmetric then it appears to exhibit real eigenvalues for all 0
Mechanics and Newton-Cartan-like gravity on the Newton-Hooke space-time
International Nuclear Information System (INIS)
Tian Yu; Guo Hanying; Huang Chaoguang; Xu Zhan; Zhou Bin
2005-01-01
We focus on the dynamical aspects on Newton-Hooke space-time NH + mainly from the viewpoint of geometric contraction of the de Sitter spacetime with Beltrami metric. (The term spacetime is used to denote a space with non-degenerate metric, while the term space-time is used to denote a space with degenerate metric.) We first discuss the Newton-Hooke classical mechanics, especially the continuous medium mechanics, in this framework. Then, we establish a consistent theory of gravity on the Newton-Hooke space-time as a kind of Newton-Cartan-like theory, parallel to the Newton's gravity in the Galilei space-time. Finally, we give the Newton-Hooke invariant Schroedinger equation from the geometric contraction, where we can relate the conservative probability in some sense to the mass density in the Newton-Hooke continuous medium mechanics. Similar consideration may apply to the Newton-Hooke space-time NH - contracted from anti-de Sitter spacetime
Causal fermion systems: A quantum space-time emerging from an action principle
Energy Technology Data Exchange (ETDEWEB)
Finster, Felix [Mathematics Department, University of Regensburg (Germany)
2013-07-01
Causal fermion systems provide a general framework for the formulation of relativistic quantum theory. A particular feature is that space-time is a secondary object which emerges by minimizing an action. The aim of the talk is to give a simple introduction, with an emphasis on conceptual issues. We begin with Dirac spinors in Minkowski space and explain how to formulate the system as a causal fermion system. As an example in curved space-time, we then consider spinors on a globally hyperbolic space-time. An example on a space-time lattice illustrates that causal fermion systems also allow for the description of discrete space-times. These examples lead us to the general definition of causal fermion systems. The causal action principle is introduced. We outline how for a given minimizer, one has notions of causality, connection and curvature, which generalize the classical notions and give rise to a proposal for a ''quantum geometry''. In the last part of the talk, we outline how quantum field theory can be described in this framework and discuss the relation to other approaches.
Directory of Open Access Journals (Sweden)
Arnold eZiesche
2014-03-01
Full Text Available The understanding of the subjective experience of a visually stable world despite the occurrence of an observer's eye movements has been the focus of extensive research for over 20 years. These studies have revealed fundamental mechanisms such as anticipatory receptive field shifts and the saccadic suppression of stimulus displacements, yet there currently exists no single explanatory framework for these observations. We show that a previously presented neuro-computational model of peri-saccadic mislocalization accounts for the phenomenon of predictive remapping and for the observation of saccadic suppression of displacement (SSD. This converging evidence allows us to identify the potential ingredients of perceptual stability that generalize beyond different data sets in a formal physiology-based model. In particular we propose that predictive remapping stabilizes the visual world across saccades by introducing a feedback loop and, as an emergent result, small displacements of stimuli are not noticed by the visual system. The model provides a link from neural dynamics, to neural mechanism and finally to behavior, and thus offers a testable comprehensive framework of visual stability.
Directory of Open Access Journals (Sweden)
Chi-Wen Lee
Full Text Available Protein thermal stability is an important factor considered in medical and industrial applications. Many structural characteristics related to protein thermal stability have been elucidated, and increasing salt bridges is considered as one of the most efficient strategies to increase protein thermal stability. However, the accurate simulation of salt bridges remains difficult. In this study, a novel method for salt-bridge design was proposed based on the statistical analysis of 10,556 surface salt bridges on 6,493 X-ray protein structures. These salt bridges were first categorized based on pairing residues, secondary structure locations, and Cα-Cα distances. Pairing preferences generalized from statistical analysis were used to construct a salt-bridge pair index and utilized in a weighted electrostatic attraction model to find the effective pairings for designing salt bridges. The model was also coupled with B-factor, weighted contact number, relative solvent accessibility, and conservation prescreening to determine the residues appropriate for the thermal adaptive design of salt bridges. According to our method, eight putative salt-bridges were designed on a mesophilic β-glucosidase and 24 variants were constructed to verify the predictions. Six putative salt-bridges leaded to the increase of the enzyme thermal stability. A significant increase in melting temperature of 8.8, 4.8, 3.7, 1.3, 1.2, and 0.7°C of the putative salt-bridges N437K-D49, E96R-D28, E96K-D28, S440K-E70, T231K-D388, and Q277E-D282 was detected, respectively. Reversing the polarity of T231K-D388 to T231D-D388K resulted in a further increase in melting temperatures by 3.6°C, which may be caused by the transformation of an intra-subunit electrostatic interaction into an inter-subunit one depending on the local environment. The combination of the thermostable variants (N437K, E96R, T231D and D388K generated a melting temperature increase of 15.7°C. Thus, this study
Jia, Shouqing; La, Dongsheng; Ma, Xuelian
2018-04-01
The finite difference time domain (FDTD) algorithm and Green function algorithm are implemented into the numerical simulation of electromagnetic waves in Schwarzschild space-time. FDTD method in curved space-time is developed by filling the flat space-time with an equivalent medium. Green function in curved space-time is obtained by solving transport equations. Simulation results validate both the FDTD code and Green function code. The methods developed in this paper offer a tool to solve electromagnetic scattering problems.
Directory of Open Access Journals (Sweden)
Jisheng Zhang
2015-06-01
Full Text Available It is essential for transportation management centers to equip and manage a network of fixed and mobile sensors in order to quickly detect traffic incidents and further monitor the related impact areas, especially for high-impact accidents with dramatic traffic congestion propagation. As emerging small Unmanned Aerial Vehicles (UAVs start to have a more flexible regulation environment, it is critically important to fully explore the potential for of using UAVs for monitoring recurring and non-recurring traffic conditions and special events on transportation networks. This paper presents a space-time network- based modeling framework for integrated fixed and mobile sensor networks, in order to provide a rapid and systematic road traffic monitoring mechanism. By constructing a discretized space-time network to characterize not only the speed for UAVs but also the time-sensitive impact areas of traffic congestion, we formulate the problem as a linear integer programming model to minimize the detection delay cost and operational cost, subject to feasible flying route constraints. A Lagrangian relaxation solution framework is developed to decompose the original complex problem into a series of computationally efficient time-dependent and least cost path finding sub-problems. Several examples are used to demonstrate the results of proposed models in UAVs’ route planning for small and medium-scale networks.
Researching on Hawking Effect in a Kerr Space Time via Open Quantum System Approach
International Nuclear Information System (INIS)
Liu, Wen-Biao; Liu, Xian-Ming
2014-01-01
It has been proposed that Hawking radiation from a Schwarzschild or a de Sitter spacetime can be understood as the manifestation of thermalization phenomena in the framework of an open quantum system. Through examining the time evolution of a detector interacting with vacuum massless scalar fields, it is found that the detector would spontaneously excite with a probability the same as the thermal radiation at Hawking temperature. Following the proposals, the Hawking effect in a Kerr space time is investigated in the framework of an open quantum systems. It is shown that Hawking effect of the Kerr space time can also be understood as the the manifestation of thermalization phenomena via open quantum system approach. Furthermore, it is found that near horizon local conformal symmetry plays the key role in the quantum effect of the Kerr space time
Separation of massive field equation of arbitrary spin in Robertson-Walker space-time
International Nuclear Information System (INIS)
Zecca, A.
2006-01-01
The massive spin-(3/2) field equation is explicitly integrated in the Robertson-Walker space-time by the Newman Penrose formalism. The solution is obtained by extending a separation procedure previously used to solve the spin-1 equation. The separated time dependence results in two coupled equations depending on the cosmological background evolution. The separated angular equations are explicitly integrated and the eigenvalues determined. The separated radial equations are integrated in the flat space-time case. The separation method of solution is then generalized, by induction, to prove the main result, that is the separability of the massive field equations of arbitrary spin in the Robertson-Walker space-time
Turbo coding, turbo equalisation and space-time coding for transmission over fading channels
Hanzo, L; Yeap, B
2002-01-01
Against the backdrop of the emerging 3G wireless personal communications standards and broadband access network standard proposals, this volume covers a range of coding and transmission aspects for transmission over fading wireless channels. It presents the most important classic channel coding issues and also the exciting advances of the last decade, such as turbo coding, turbo equalisation and space-time coding. It endeavours to be the first book with explicit emphasis on channel coding for transmission over wireless channels. Divided into 4 parts: Part 1 - explains the necessary background for novices. It aims to be both an easy reading text book and a deep research monograph. Part 2 - provides detailed coverage of turbo conventional and turbo block coding considering the known decoding algorithms and their performance over Gaussian as well as narrowband and wideband fading channels. Part 3 - comprehensively discusses both space-time block and space-time trellis coding for the first time in literature. Par...
Structure of the Einstein tensor for class-1 embedded space time
Energy Technology Data Exchange (ETDEWEB)
Krause, J [Universidad Central de Venezuela, Caracas
1976-04-11
Continuing previous work, some features of the flat embedding theory of class-1 curved space-time are further discussed. In the two-metric formalism provided by the embedding approach the Gauss tensor obtains as the flat-covariant gradient of a fundamental vector potential. The Einstein tensor is then examined in terms of the Gauss tensor. It is proved that the Einstein tensor is divergence free in flat space-time, i.e. a true Lorentz-covariant conservation law for the Einstein tensor is shown to hold. The form of the Einstein tensor in flat space-time also appears as a canonical energy-momentum tensor of the vector potential. The corresponding Lagrangian density, however, does not provide us with a set of field equations for the fundamental vector potential; indeed, the Euler-Lagrange ''equations'' collapse to a useless identity, while the Lagrangian density has the form of a flat divergence.
Classical field theory in the space of reference frames. [Space-time manifold, action principle
Energy Technology Data Exchange (ETDEWEB)
Toller, M [Dipartimento di Matematica e Fisica, Libera Universita, Trento (Italy)
1978-03-11
The formalism of classical field theory is generalized by replacing the space-time manifold M by the ten-dimensional manifold S of all the local reference frames. The geometry of the manifold S is determined by ten vector fields corresponding to ten operationally defined infinitesimal transformations of the reference frames. The action principle is written in terms of a differential 4-form in the space S (the Lagrangian form). Densities and currents are represented by differential 3-forms in S. The field equations and the connection between symmetries and conservation laws (Noether's theorem) are derived from the action principle. Einstein's theory of gravitation and Maxwell's theory of electromagnetism are reformulated in this language. The general formalism can also be used to formulate theories in which charge, energy and momentum cannot be localized in space-time and even theories in which a space-time manifold cannot be defined exactly in any useful way.
Maximum Likelihood Blind Channel Estimation for Space-Time Coding Systems
Directory of Open Access Journals (Sweden)
Hakan A. Çırpan
2002-05-01
Full Text Available Sophisticated signal processing techniques have to be developed for capacity enhancement of future wireless communication systems. In recent years, space-time coding is proposed to provide significant capacity gains over the traditional communication systems in fading wireless channels. Space-time codes are obtained by combining channel coding, modulation, transmit diversity, and optional receive diversity in order to provide diversity at the receiver and coding gain without sacrificing the bandwidth. In this paper, we consider the problem of blind estimation of space-time coded signals along with the channel parameters. Both conditional and unconditional maximum likelihood approaches are developed and iterative solutions are proposed. The conditional maximum likelihood algorithm is based on iterative least squares with projection whereas the unconditional maximum likelihood approach is developed by means of finite state Markov process modelling. The performance analysis issues of the proposed methods are studied. Finally, some simulation results are presented.
The space-time cube revisited it potential to visualize mobile data
DEFF Research Database (Denmark)
Kveladze, Irma; Kraak, Menno-Jan
2010-01-01
and analyse the complex movement patterns (COST - MOVE, 2009; Keim et al., 2008). This results in the development of new visual analytical and exploratory tools, while existing solutions receive new attention (Andrienko et al., 2007). Among the last the Space Time Cube (STC) can be grouped. It has the ability...... to provide information about spatial and temporal relationships. The original idea of STC was introduced by Hägerstrand (1970). It represents an elegant framework to study spatio-temporal characteristics of human activity (Kraak and Koussoulakou, 2005). The vertical dimension of cube represents time (t......), while horizontal axes represent space (x, y). Basic elements represented in the cube are the Space-time Path (STP), Stations, and the Space Time Prism (STP). The STP represents the continuous activities of movements undertaken in space and time displayed as trajectory. It has been studied...
Quantum corrections in thermal states of fermions on anti-de Sitter space-time
Ambruş, Victor E.; Winstanley, Elizabeth
2017-12-01
We study the energy density and pressure of a relativistic thermal gas of massless fermions on four-dimensional Minkowski and anti-de Sitter space-times using relativistic kinetic theory. The corresponding quantum field theory quantities are given by components of the renormalized expectation value of the stress-energy tensor operator acting on a thermal state. On Minkowski space-time, the renormalized vacuum expectation value of the stress-energy tensor is by definition zero, while on anti-de Sitter space-time the vacuum contribution to this expectation value is in general nonzero. We compare the properties of the vacuum and thermal expectation values of the energy density and pressure for massless fermions and discuss the circumstances in which the thermal contribution dominates over the vacuum one.
Space-Time Foam in 2D and the Sum Over Topologies
International Nuclear Information System (INIS)
Loll, R.; Westra, W.
2003-01-01
It is well-known that the sum over topologies in quantum gravity is ill-defined, due to a super-exponential growth of the number of geometries as a function of the space-time volume, leading to a badly divergent gravitational path integral. Not even in dimension 2, where a non-perturbative quantum gravity theory can be constructed explicitly from a (regularized) path integral, has this problem found a satisfactory solution. In the present work, we extend a previous 2d Lorentzian path integral, regulated in terms of Lorentzian random triangulations, to include space-times with an arbitrary number of handles. We show that after the imposition of physically motivated causality constraints, the combined sum over geometries and topologies is well-defined and possesses a continuum limit which yields a concrete model of space-time foam in two dimensions. (author)
Efficient coding schemes with power allocation using space-time-frequency spreading
Institute of Scientific and Technical Information of China (English)
Jiang Haining; Luo Hanwen; Tian Jifeng; Song Wentao; Liu Xingzhao
2006-01-01
An efficient space-time-frequency (STF) coding strategy for multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is presented for high bit rate data transmission over frequency selective fading channels. The proposed scheme is a new approach to space-time-frequency coded OFDM (COFDM) that combines OFDM with space-time coding, linear precoding and adaptive power allocation to provide higher quality of transmission in terms of the bit error rate performance and power efficiency. In addition to exploiting the maximum diversity gain in frequency, time and space, the proposed scheme enjoys high coding advantages and low-complexity decoding. The significant performance improvement of our design is confirmed by corroborating numerical simulations.
Quantum field theory of the universe in the Kantowski-Sachs space-time
International Nuclear Information System (INIS)
Shen, Y.; Tan, Z.
1996-01-01
In this paper, the quantum field theory of the universe in the Kantowski-Sachs space-time is studied. An analogue of proceedings in quantum field theory is applied in curved space-time to the Kantowski-Sachs space-time, obtaining the wave function of the universe satisfied the Wheeler-DeWitt equation. Regarding the wave function as a universe field in the minisuperspace, the authors can not only overcome the difficulty of the probabilistic interpretation in quantum cosmology, but also come to the conclusion that there is multiple production of universes. The average number of the produced universes from nothing is calculated. The distribution of created universe is given. It is the Planckian distribution
From Discrete Space-Time to Minkowski Space: Basic Mechanisms, Methods and Perspectives
Finster, Felix
This survey article reviews recent results on fermion systems in discrete space-time and corresponding systems in Minkowski space. After a basic introduction to the discrete setting, we explain a mechanism of spontaneous symmetry breaking which leads to the emergence of a discrete causal structure. As methods to study the transition between discrete space-time and Minkowski space, we describe a lattice model for a static and isotropic space-time, outline the analysis of regularization tails of vacuum Dirac sea configurations, and introduce a Lorentz invariant action for the masses of the Dirac seas. We mention the method of the continuum limit, which allows to analyze interacting systems. Open problems are discussed.
Euclidean scalar Green function in a higher dimensional global monopole space-time
International Nuclear Information System (INIS)
Bezerra de Mello, E.R.
2002-01-01
We construct the explicit Euclidean scalar Green function associated with a massless field in a higher dimensional global monopole space-time, i.e., a (1+d)-space-time with d≥3 which presents a solid angle deficit. Our result is expressed in terms of an infinite sum of products of Legendre functions with Gegenbauer polynomials. Although this Green function cannot be expressed in a closed form, for the specific case where the solid angle deficit is very small, it is possible to develop the sum and obtain the Green function in a more workable expression. Having this expression it is possible to calculate the vacuum expectation value of some relevant operators. As an application of this formalism, we calculate the renormalized vacuum expectation value of the square of the scalar field, 2 (x)> Ren , and the energy-momentum tensor, μν (x)> Ren , for the global monopole space-time with spatial dimensions d=4 and d=5
Mathematical Formalism for an Experimental Test of Space-Time Anisotropy
International Nuclear Information System (INIS)
Voicu-Brinzei, Nicoleta; Siparov, Sergey
2010-01-01
Some specific astrophysical data collected during the last decade suggest the need of a modification of the expression for the Einstein-Hilbert action, and several attempts are known in this respect. The modification suggested in this paper stems from a possible anisotropy of space-time--which leads to a dependence on directional variables of the simplest scalar in the least action principle. In order to provide a testable support to this idea, the optic-metrical parametric resonance is regarded - an experiment on a galactic scale, based on the interaction between the electromagnetic radiation of cosmic masers and periodical gravitational waves emitted by close double systems or pulsars. Since the effect depends on the space-time metric, a possible anisotropy could be revealed through observations. We prove that if space-time is anisotropic, then the orientation of the astrophysical systems suitable for observations would show it.
Galashev, A. E.; Ivanichkina, K. A.; Vorob'ev, A. S.; Rakhmanova, O. R.
2017-06-01
The structure and stability of a two-layer defective silicene on Ag(001) and Ag(111) substrates have been investigated using the molecular dynamics method. The transformation of the radial distribution function of silicene due to the formation of monovacancies, divacancies, trivacancies, and hexavacancies is reduced primarily to a decrease in the intensity of the peaks and the disappearance of the "shoulder" in the second peak. With the passage of time, multivacancies can undergo coalescence with each other and the fragmentation into smaller vacancies, as well as form vacancy clusters. According to the geometric criterion, the Ag(001) substrate provides a higher stability of a perfect two-layer silicene. It has been found, however, that the defective silicene on this substrate has a lower energy only when it contains monovacancies and divacancies. A change in the size of defects leads to a change in the energy priority when choosing between the Ag(001) and Ag(111) substrates. The motion of a lithium ion inside an extended channel between two silicene sheets results in a further disordering of the defective structure of the silicene, during which the strongest stresses in the silicene are generated by forces directed perpendicular to the external electric field. These forces dominate in the silicene channel, the wall of which is supported by the Ag(001) or Ag(111) substrate.
International Nuclear Information System (INIS)
Hernández Valdés, Daniel; Rodríguez Riera, Zalua; Jáuregui Haza, Ulises; Díaz García, Alicia; Benoist, Eric
2016-01-01
The development of novel radiopharmaceuticals in nuclear medicine based on the M(CO)3 (M = Tc, Re) complexes has attracted great attention1. The versatility of this core and the easy production of the fac-[M(CO)3(H 2 O) 3 ]+ precursor could explain this interest2,3. The main characteristics of these tricarbonyl complexes are a high substitution stability of the three CO ligands and a corresponding lability of the coordinated water molecules, yielding, via easy exchange of a variety of mono-, bi-, and tridentate ligands, complexes of very high kinetic stability. A computational study of different tricarbonyl complexes for Re(I) and Tc(I) has been performed using density functional theory. The solvent effect was simulated using the polarizable continuum model. The fully optimized complexes show geometries that compare favorably with the X-ray data. These structures were used as a starting point to investigate the relative stability of tricarbonyl complexes with various tridentate ligands. They comprise an iminodiacetic acid unit for tridentate coordination to the fac-[M(CO) 3 ]+ moiety (M = Re, Tc), an aromatic ring system bearing a functional group (NO 2 -, NH 2 - and Cl-) as linking site model, and a tethering moiety (methylene, ethylene, propylene butylene or pentylene bridge) between the linking and coordinating sites. In general, Re complexes are more stables than the corresponding Tc complexes. Furthermore, the NH2 functional group, medium length in the carbon chain and meta substitution increase the stability of the complexes. The correlation of these results with the available experimental4 data on these systems allows bringing some understanding of the chemistry of tricarbonyl complexes. (author)
International Nuclear Information System (INIS)
Persides, S.
1980-01-01
A new formulation is established for the study of the asymptotic structure at spatial infinity of asymptotically Minkowskian space--times. First, the concept of an asymptotically simple space--time at spatial infinity is defined. This is a (physical) space--time (M,g) which can be imbedded in an unphysical space--time (M,g) with a boundary S, a C/sup infinity/ metric g and a C/sup infinity/ scalar field Ω such that Ω=0 on S, Ω>0 on M-S, and g/sup munu/ + g/sup mulambda/ g/sup nurho/ Ω/sub vertical-barlambda/ Ω/sub vertical-barrho/=Ω -2 g/sup murho/ +Ω -4 g/sup mulambda/ g/sup nurho/ Ω/sub ;/lambda Ω/sub ;/rho on M. Then an almost asymptotically flat space--time (AAFS) is defined as an asymptotically simple space--time for which S is isometric to the unit timelike hyperboloid and g/sup munu/ Ω/sub vertical-barmu/ Ω/sub vertical-barnu/ =Ω -4 g/sup munu/ Ω/sub ;/μΩ/sub ;/ν=-1 on S. Equivalent definitions are given in terms of the existence of coordinate systems in which g/sub munu/ or g/sub munu/ have simple explicitly given forms. The group of asymptotic symmetries of (M,g) is studied and is found to be isomorphic to the Lorentz group. The asymptotic behavior of an AAFS is studied. It is proven that the conformal metric g/sub munu/=Ω 2 g/sub munu/ gives C/sup lambdamurhonu/=0, Ω -1 C/sup lambdamurhonu/ Ω/sub ;/μ =0, Ω -2 C/sup lambdamurhonu/ Ω/sub ;/μ Ω/sub ;/ν=0 on S
Exploratory space-time analyses of Rift Valley Fever in South Africa in 2008-2011.
Directory of Open Access Journals (Sweden)
Raphaëlle Métras
Full Text Available Rift Valley fever (RVF is a zoonotic arbovirosis for which the primary hosts are domestic livestock (cattle, sheep and goats. RVF was first described in South Africa in 1950-1951. Mechanisms for short and long distance transmission have been hypothesised, but there is little supporting evidence. Here we describe RVF occurrence and spatial distribution in South Africa in 2008-11, and investigate the presence of a contagious process in order to generate hypotheses on the different mechanisms of transmission.A total of 658 cases were extracted from World Animal Health Information Database. Descriptive statistics, epidemic curves and maps were produced. The space-time K-function was used to test for evidence of space-time interaction. Five RVF outbreak waves (one in 2008, two in 2009, one in 2010 and one in 2011 of varying duration, location and size were reported. About 70% of cases (n = 471 occurred in 2010, when the epidemic was almost country-wide. No strong evidence of space-time interaction was found for 2008 or the second wave in 2009. In the first wave of 2009, a significant space-time interaction was detected for up to one month and over 40 km. In 2010 and 2011 a significant intense, short and localised space-time interaction (up to 3 days and 15 km was detected, followed by one of lower intensity (up to 2 weeks and 35 to 90 km.The description of the spatiotemporal patterns of RVF in South Africa between 2008 and 2011 supports the hypothesis that during an epidemic, disease spread may be supported by factors other than active vector dispersal. Limitations of under-reporting and space-time K-function properties are discussed. Further spatial analyses and data are required to explain factors and mechanisms driving RVF spread.
International Nuclear Information System (INIS)
Moreno, C.
1977-01-01
In stationary space--times V/sub n/ x R with compact space-section manifold without boundary V/sub n/, the Klein--Gordon equation is solved by the one-parameter group of unitary operators generated by the energy operator i -1 T -1 in the Sobolev spaces H/sup l/(V/sub n/) x H/sup l/(V/sub n/). The canonical symplectic and complex structures of the associated dynamical system are calculated. The existence and the uniqueness of the Lichnerowicz kernel are established. The Hilbert spaces of positive and negative frequency-part solutions defined by means of this kernel are constructed
Feshchenko, R. M.
Recently a new exact transparent boundary condition (TBC) for the 3D parabolic wave equation (PWE) in rectangular computational domain was derived. However in the obtained form it does not appear to be unconditionally stable when used with, for instance, the Crank-Nicolson finite-difference scheme. In this paper two new formulations of the TBC for the 3D PWE in rectangular computational domain are reported, which are likely to be unconditionally stable. They are based on an unconditionally stable fully discrete TBC for the Crank-Nicolson scheme for the 2D PWE. These new forms of the TBC can be used for numerical solution of the 3D PWE when a higher precision is required.
Unitals and ovals of symmetric block designs in LDPC and space-time coding
Andriamanalimanana, Bruno R.
2004-08-01
An approach to the design of LDPC (low density parity check) error-correction and space-time modulation codes involves starting with known mathematical and combinatorial structures, and deriving code properties from structure properties. This paper reports on an investigation of unital and oval configurations within generic symmetric combinatorial designs, not just classical projective planes, as the underlying structure for classes of space-time LDPC outer codes. Of particular interest are the encoding and iterative (sum-product) decoding gains that these codes may provide. Various small-length cases have been numerically implemented in Java and Matlab for a number of channel models.
Fermion Fields in BTZ Black Hole Space-Time and Entanglement Entropy
Directory of Open Access Journals (Sweden)
Dharm Veer Singh
2015-01-01
Full Text Available We study the entanglement entropy of fermion fields in BTZ black hole space-time and calculate prefactor of the leading and subleading terms and logarithmic divergence term of the entropy using the discretized model. The leading term is the standard Bekenstein-Hawking area law and subleading term corresponds to first quantum corrections in black hole entropy. We also investigate the corrections to entanglement entropy for massive fermion fields in BTZ space-time. The mass term does not affect the area law.
Unification of gauge and gravity Chern-Simons theories in 3-D space-time
Energy Technology Data Exchange (ETDEWEB)
Saghir, Chireen A.; Shamseddine, Laurence W. [American University of Beirut, Physics Department, Beirut (Lebanon)
2017-11-15
Chamseddine and Mukhanov showed that gravity and gauge theories could be unified in one geometric construction provided that a metricity condition is imposed on the vielbein. In this paper we are going to show that by enlarging the gauge group we are able to unify Chern-Simons gauge theory and Chern-Simons gravity in 3-D space-time. Such a unification leads to the quantization of the coefficients for both Chern-Simons terms for compact groups but not for non-compact groups. Moreover, it leads to a topological invariant quantity of the 3-dimensional space-time manifold on which they are defined. (orig.)
DEFF Research Database (Denmark)
Tastu, Julija; Pinson, Pierre; Madsen, Henrik
2015-01-01
-correlations. Estimation is performed in a maximum likelihood framework. Based on a test case application in Denmark, with spatial dependencies over 15 areas and temporal ones for 43 hourly lead times (hence, for a dimension of n = 645), it is shown that accounting for space-time effects is crucial for generating skilful......Emphasis is placed on generating space-time trajectories of wind power generation, consisting of paths sampled from high-dimensional joint predictive densities, describing wind power generation at a number of contiguous locations and successive lead times. A modelling approach taking advantage...
Space-time uncertainty and approaches to D-brane field theory
International Nuclear Information System (INIS)
Yoneya, Tamiaki
2008-01-01
In connection with the space-time uncertainty principle which gives a simple qualitative characterization of non-local or non-commutative nature of short-distance space-time structure in string theory, the author's recent approaches toward field theories for D-branes are briefly outlined, putting emphasis on some key ideas lying in the background. The final section of the present report is devoted partially to a tribute to Yukawa on the occasion of the centennial of his birth. (author)
A multi-element cosmological model with a complex space-time topology
Kardashev, N. S.; Lipatova, L. N.; Novikov, I. D.; Shatskiy, A. A.
2015-02-01
Wormhole models with a complex topology having one entrance and two exits into the same space-time of another universe are considered, as well as models with two entrances from the same space-time and one exit to another universe. These models are used to build a model of a multi-sheeted universe (a multi-element model of the "Multiverse") with a complex topology. Spherical symmetry is assumed in all the models. A Reissner-Norström black-hole model having no singularity beyond the horizon is constructed. The strength of the central singularity of the black hole is analyzed.
Nonextreme and ultraextreme domain walls and their global space-times
International Nuclear Information System (INIS)
Cvetic, M.; Griffies, S.; Soleng, H.H.
1993-01-01
Nonextreme walls (bubbles with two insides) and ultraextreme walls (bubbles of false vacuum decay) are discussed. Their respective energy densities are higher and lower than that of the corresponding extreme (supersymmetric), planar domain wall. These singularity free space-times exhibit nontrivial causal structure analogous to certain nonextreme black holes. We focus on anti--de Sitter--Minkowski walls and comment on Minkowski-Minkowski walls with trivial extreme limit, as well as walls adjacent to de Sitter space-times with no extreme limit
Optical isolation based on space-time engineered asymmetric photonic band gaps
Chamanara, Nima; Taravati, Sajjad; Deck-Léger, Zoé-Lise; Caloz, Christophe
2017-10-01
Nonreciprocal electromagnetic devices play a crucial role in modern microwave and optical technologies. Conventional methods for realizing such systems are incompatible with integrated circuits. With recent advances in integrated photonics, the need for efficient on-chip magnetless nonreciprocal devices has become more pressing than ever. This paper leverages space-time engineered asymmetric photonic band gaps to generate optical isolation. It shows that a properly designed space-time modulated slab is highly reflective/transparent for opposite directions of propagation. The corresponding design is magnetless, accommodates low modulation frequencies, and can achieve very high isolation levels. An experimental proof of concept at microwave frequencies is provided.
Lorentz covariant tempered distributions in two-dimensional space-time
International Nuclear Information System (INIS)
Zinov'ev, Yu.M.
1989-01-01
The problem of describing Lorentz covariant distributions without any spectral condition has hitherto remained unsolved even for two-dimensional space-time. Attempts to solve this problem have already been made. Zharinov obtained an integral representation for the Laplace transform of Lorentz invariant distributions with support in the product of two-dimensional future light cones. However, this integral representation does not make it possible to obtain a complete description of the corresponding Lorentz invariant distributions. In this paper the author gives a complete description of Lorentz covariant distributions for two-dimensional space-time. No spectral conditions is assumed
New Li-Yau-Hamilton Inequalities for the Ricci Flow via the Space-Time Approach
Chow, Bennett; Knopf, Dan
2002-01-01
We generalize Hamilton's matrix Li-Yau-type Harnack estimate for the Ricci flow by considering the space of all LYH (Li-Yau-Hamilton) quadratics that arise as curvature tensors of space-time connections satisfying the Ricci flow with respect to the natural space-time degenerate metric. As a special case, we employ scaling arguments to derive a linear-type matrix LYH estimate. The new LYH quadratics obtained in this way are associated to the system of the Ricci flow coupled to a 1-form and a 2...
Matthias Kasemann
Overview The main focus during the summer was to handle data coming from the detector and to perform Monte Carlo production. The lessons learned during the CCRC and CSA08 challenges in May were addressed by dedicated PADA campaigns lead by the Integration team. Big improvements were achieved in the stability and reliability of the CMS Tier1 and Tier2 centres by regular and systematic follow-up of faults and errors with the help of the Savannah bug tracking system. In preparation for data taking the roles of a Computing Run Coordinator and regular computing shifts monitoring the services and infrastructure as well as interfacing to the data operations tasks are being defined. The shift plan until the end of 2008 is being put together. User support worked on documentation and organized several training sessions. The ECoM task force delivered the report on “Use Cases for Start-up of pp Data-Taking” with recommendations and a set of tests to be performed for trigger rates much higher than the ...
Self-calibration for lab-μCT using space-time regularized projection-based DVC and model reduction
Jailin, C.; Buljac, A.; Bouterf, A.; Poncelet, M.; Hild, F.; Roux, S.
2018-02-01
An online calibration procedure for x-ray lab-CT is developed using projection-based digital volume correlation. An initial reconstruction of the sample is positioned in the 3D space for every angle so that its projection matches the initial one. This procedure allows a space-time displacement field to be estimated for the scanned sample, which is regularized with (i) rigid body motions in space and (ii) modal time shape functions computed using model reduction techniques (i.e. proper generalized decomposition). The result is an accurate identification of the position of the sample adapted for each angle, which may deviate from the desired perfect rotation required for standard reconstructions. An application of this procedure to a 4D in situ mechanical test is shown. The proposed correction leads to a much improved tomographic reconstruction quality.
Coproduct and star product in field theories on Lie-algebra noncommutative space-times
International Nuclear Information System (INIS)
Amelino-Camelia, Giovanni; Arzano, Michele
2002-01-01
We propose a new approach to field theory on κ-Minkowski noncommutative space-time, a popular example of Lie-algebra space-time. Our proposal is essentially based on the introduction of a star product, a technique which is proving to be very fruitful in analogous studies of canonical noncommutative space-times, such as the ones recently found to play a role in the description of certain string-theory backgrounds. We find to be incorrect the expectation, previously reported in the literature, that the lack of symmetry of the κ-Poincare coproduct should lead to interaction vertices that are not symmetric under exchanges of the momenta of identical particles entering the relevant processes. We show that in κ-Minkowski the coproduct and the star product must indeed treat momenta in a nonsymmetric way, but the overall structure of interaction vertices is symmetric under exchange of identical particles. We also show that in κ-Minkowski field theories it is convenient to introduce the concepts of 'planar' and 'nonplanar' Feynman loop diagrams, again in close analogy with the corresponding concepts previously introduced in the study of field theories in canonical noncommutative space-times
Estimating space-time mean concentrations of nutrients in surface waters of variable depth
Knotters, M.; Brus, D.J.
2010-01-01
A monitoring scheme has been designed to test whether the space-time mean concentration total Nitrogen (N-total) in the surface water in the Northern Frisian Woodlands (NFW, The Netherlands) complies with standards of the European Water Framework directive. Since in statistical testing for
Conformally invariant amplitudes and field theory in a space-time of constant curvature
International Nuclear Information System (INIS)
Drummond, I.T.
1977-02-01
The problem of calculating the ultra violet divergences of a field theory in a spherical space-time is reduced to analysing the pole structure of conformally invariant integrals which are analogous to amplitudes which occur in the theory of dual models. The calculations are illustrated with phi 3 -theory in six-dimensions. (author)
A bootstrap based space-time surveillance model with an application to crime occurrences
Kim, Youngho; O'Kelly, Morton
2008-06-01
This study proposes a bootstrap-based space-time surveillance model. Designed to find emerging hotspots in near-real time, the bootstrap based model is characterized by its use of past occurrence information and bootstrap permutations. Many existing space-time surveillance methods, using population at risk data to generate expected values, have resulting hotspots bounded by administrative area units and are of limited use for near-real time applications because of the population data needed. However, this study generates expected values for local hotspots from past occurrences rather than population at risk. Also, bootstrap permutations of previous occurrences are used for significant tests. Consequently, the bootstrap-based model, without the requirement of population at risk data, (1) is free from administrative area restriction, (2) enables more frequent surveillance for continuously updated registry database, and (3) is readily applicable to criminology and epidemiology surveillance. The bootstrap-based model performs better for space-time surveillance than the space-time scan statistic. This is shown by means of simulations and an application to residential crime occurrences in Columbus, OH, year 2000.
Riccion from higher-dimensional space-time with D-dimensional ...
Indian Academy of Sciences (India)
suggest that space-time above 3 05¢1016 GeV should be fractal. .... Here VD is the volume of SD, g´4·Dµ is the determinant of the metric tensor gMN (M ...... means that above 3.05x1016 GeV, SD is not a smooth surface whereas M4 is smooth.
Space-time supersymmetry of extended fermionic strings in 2 + 2 dimensions
International Nuclear Information System (INIS)
Ketov, S.V.
1993-04-01
The N = 2 fermionic string theory is revisited in light of its recently proposed equivalence to the non-compact N = 4 fermionic string model. The issues of space-time Lorentz covariance and supersymmetry for the BRST quantized N = 2 strings living in uncompactified 2 + 2 dimensions are discussed. The equivalent local quantum supersymmetric field theory appears to be the most transparent way to represent the space-time symmetries of the extended fermionic strings and their interactions. Our considerations support the Siegel's ideas about the presence of SO(2,2) Lorentz symmetry as well as at least two self-dual space-time supersymmetries in the theory of the N = 2(4) fermionic strings, though we do not have a compelling reason to argue about the necessity of the maximal space-time supersymmetry. The world-sheet arguments about the absence of all string massive modes in the physical spectrum, and the vanishing of all string-loop amplitudes in the Polyakov approach, are given on the basis of general consistency of the theory. (orig.)
On the study of quantum properties of space-time with interferometers and resonant bars
International Nuclear Information System (INIS)
Amelino-Camelia, G.
2001-01-01
The expectation that it should not be possible to gain experimental insight on the structure of space-time at Planckian distance scales has been recently challenged by several studies which have shown that there are a few classes of experiments with sensitivity sufficient for setting significant limits on certain candidate Planckian pictures of space-time. With respect to quantum space-time fluctuations, one of the most popular predictions of various Quantum-Gravity approaches, the experiments that have the best sensitivity are the same experiments which are used in searches of the classical-physics phenomenon of gravity waves. In experiments searching for classical gravity waves the presence of quantum space-time fluctuations would introduce a source of noise just like the ordinary (non-gravitational) quantum properties of the photons composing the laser beam used in interferometry introduce a source of noise. The sensitivity to distance fluctuations achieved (or being achieved) by modern interferometers and resonant-bar detectors is here described in terms of the Planck length, hoping that this characterization may prove useful for theorists attempting to gain some intuition for these sensitivity levels. While theory work on Quantum Gravity is not yet ready to provide definite noise models, there are some general characteristics of Quantum-Gravity-induced noise that could be used in experimental studies. (author)
How to defeat Wüthrich's abysmal embarrassment argument against space-time structuralism
F.A. Muller (Archibald)
2011-01-01
textabstractIn his award-winning contribution to the biannual PSA conference at Pittsburgh in 2008, Christian Wüthrich mounted an argument against structuralism about spacetime in the context of the general theory of relativity (GTR), to the effect that structuralists cannot discern space-time
Fundamental group of dual graphs and applications to quantum space time
International Nuclear Information System (INIS)
Nada, S.I.; Hamouda, E.H.
2009-01-01
Let G be a connected planar graph with n vertices and m edges. It is known that the fundamental group of G has 1 -(n - m) generators. In this paper, we show that if G is a self-dual graph, then its fundamental group has (n - 1) generators. We indicate that these results are relevant to quantum space time.
Christoffel symbols and inertia in flat space-time theory. [Curvilinear coordinate systems
Energy Technology Data Exchange (ETDEWEB)
Krause, J [Universidad Central de Venezuela, Caracas
1976-11-01
A necessary and sufficient criterion of inertia is presented, for the flat space-time theory of general frames of reference, in terms of the vanishing of some typical components of the affine connection pertaining to curvilinear coordinate systems. The physical identification of inertial forces thus arises in the context of the special theory of relativity.
On the Possibility of Instant Displacements in the Space-Time of General Relativity
Directory of Open Access Journals (Sweden)
Borissova L.
2005-04-01
Full Text Available Employing the mathematical apparatus of chronometric invariants (physical observable quantities, this study finds a theoretical possibility for the instant displacement of particles in the space-time of the General Theory of Relativity. This is to date the sole theoretical explanation of the well-known phenomenon of photon teleportation, given by the purely geometrical methods of Einstein’s theory.