Operational Resource Theory of Coherence
Winter, Andreas; Yang, Dong
2016-03-01
We establish an operational theory of coherence (or of superposition) in quantum systems, by focusing on the optimal rate of performance of certain tasks. Namely, we introduce the two basic concepts—"coherence distillation" and "coherence cost"—in the processing quantum states under so-called incoherent operations [Baumgratz, Cramer, and Plenio, Phys. Rev. Lett. 113, 140401 (2014)]. We, then, show that, in the asymptotic limit of many copies of a state, both are given by simple single-letter formulas: the distillable coherence is given by the relative entropy of coherence (in other words, we give the relative entropy of coherence its operational interpretation), and the coherence cost by the coherence of formation, which is an optimization over convex decompositions of the state. An immediate corollary is that there exists no bound coherent state in the sense that one would need to consume coherence to create the state, but no coherence could be distilled from it. Further, we demonstrate that the coherence theory is generically an irreversible theory by a simple criterion that completely characterizes all reversible states.
Operational Resource Theory of Coherence.
Winter, Andreas; Yang, Dong
2016-03-25
We establish an operational theory of coherence (or of superposition) in quantum systems, by focusing on the optimal rate of performance of certain tasks. Namely, we introduce the two basic concepts-"coherence distillation" and "coherence cost"-in the processing quantum states under so-called incoherent operations [Baumgratz, Cramer, and Plenio, Phys. Rev. Lett. 113, 140401 (2014)]. We, then, show that, in the asymptotic limit of many copies of a state, both are given by simple single-letter formulas: the distillable coherence is given by the relative entropy of coherence (in other words, we give the relative entropy of coherence its operational interpretation), and the coherence cost by the coherence of formation, which is an optimization over convex decompositions of the state. An immediate corollary is that there exists no bound coherent state in the sense that one would need to consume coherence to create the state, but no coherence could be distilled from it. Further, we demonstrate that the coherence theory is generically an irreversible theory by a simple criterion that completely characterizes all reversible states. PMID:27058063
Homotopy coherent nerve in Deformation theory
Hinich, V.
2007-01-01
In this note we explain that homotopy coherent simplicial nerve has to used intead of the standard definition in the author's papers on formal deformation theory. A convenient version of the notion of fibered category is presented which is useful once one works with simplicial categories.
Towards a coherent theory of animal equality
Bruers, Stijn
2014-01-01
In this article I want to construct in a simple and systematic way an ethical theory of animal equality. The goal is a consistent theory, containing a set of clear and coherent universalized ethical principles that best fits our strongest moral intuitions in all possible morally relevant situations that we can think of, without too many arbitrary elements. I demonstrate that impartiality with a level of risk aversion and empathy with a need for efficiency are two different approaches that bot...
Lopez, Beatriz; Leekam, Susan R.; Arts, Gerda R. J.
2008-01-01
This study aimed to test the assumption drawn from weak central coherence theory that a central cognitive mechanism is responsible for integrating information at both conceptual and perceptual levels. A visual semantic memory task and a face recognition task measuring use of holistic information were administered to 15 children with autism and 16…
Ergodic Theory, Open Dynamics, and Coherent Structures
Bose, Christopher; Froyland, Gary
2014-01-01
This book is comprised of selected research articles developed from a workshop on Ergodic Theory, Probabilistic Methods and Applications, held in April 2012 at the Banff International Research Station. It contains contributions from world leading experts in ergodic theory, dynamical systems, numerical analysis, fluid dynamics, and networks. The volume will serve as a valuable reference for mathematicians, physicists, engineers, physical oceanographers, atmospheric scientists, biologists, and climate scientists, who currently use, or wish to learn how to use, probabilistic techniques to cope with dynamical models that display open, coherent, or non-equilibrium behavior.
van Lang, NDJ; Bouma, A; Sytema, S; Kraijer, DW; Minderaa, RB; Van Lang, J.D.; Kraijer, S.W
2006-01-01
Central coherence theory hypothesizes individuals with autism process information in a detail-focused fashion. The present study examined whether adolescents with an intellectual disability and comorbid autism spectrum disorder showed a weaker central coherence than age- and IQ-matched controls. The
Weak central coherence in patients with Alzheimer's disease
Institute of Scientific and Technical Information of China (English)
Selina M(a)rdh
2013-01-01
Central coherence refers to the ability to interpret details of information into a whole. To date, the concept of central coherence is mainly used in research of autism, Asperger's syndrome and recently in the research on eating disorders. The main purpose of the present study was to examine central coherence in patients with Alzheimer's disease. Nine Alzheimer's disease patients and ten age- and gender-matched control subjects, who differed significantly in neurological assessment, were shown a picture of a fire. Compared to control subjects, the Alzheimer's disease patients described the picture in a fragmented way by mentioning details and separate objects without perceiving the context of the fire. In conclusion, patients with Alzheimer's disease are at the weak end of central coherence, and hence suffer from a fragmented view of their surroundings. The findings have important clinical implications for the understanding of patients with Alzheimer's diseaseand also for the possibility of caregivers to meet the Alzheimer's disease individual in an appropriate way in the everyday care.
Study on connectivity between coherent central rhythm and electromyographic activities.
Meng, Fei; Tong, Kai-yu; Chan, Suk-tak; Wong, Wan-wa; Lui, Ka-him; Tang, Kwok-wing; Gao, Xiaorong; Gao, Shangkai
2008-09-01
Whether afferent feedback contributes to the generation of cortico-muscular coherence (CMCoh) remains an open question. In the present study, a multivariate autoregressive (MVAR) model and partial directed coherence (PDC) were applied to investigate the causal influences between the central rhythm and electromyographic (EMG) signals in the process of CMCoh. The system modeling included activities from the contralateral and ipsilateral primary sensorimotor cortex (M1/S1), supplementary motor area (SMA) and the time series from extensor carpi radialis (ECR) muscles. The results showed that afferent sensory feedback could also play an important role for the generation of CMCoh. Meanwhile, significant coherence between the EMG signals and the activities in the SMA was found in two subjects out of five. Connectivity analysis revealed a significant descending information flow which possibly reflected direct recruitment on the motoneurons from the SMA to facilitate motor control. PMID:18756033
Torday, John S.
2015-01-01
The history of physiologic cellular–molecular interrelationships can be traced all the way back to the unicellular state by following the pathway formed by lipids ubiquitously accommodating calcium homeostasis, and its consequent adaptive effects on oxygen uptake by cells, tissues and organs. As a result, a cohesive, mechanistically integrated view of physiology can be formulated by recognizing the continuum comprising conception, development, physiologic homeostasis and death mediated by soluble growth factor signaling. Seeing such seemingly disparate processes as embryogenesis, chronic disease and dying as the gain and subsequent loss of cell–cell signaling provides a novel perspective for physiology and medicine. It is emblematic of the self-organizing, self-referential nature of life, starting from its origins. Such organizing principles obviate the pitfalls of teleologic evolution, conversely providing a way of resolving such seeming dichotomies as holism and reductionism, genotype and phenotype, emergence and contingence, proximate and ultimate causation in evolution, cells and organisms. The proposed approach is scale-free and predictive, offering a Central Theory of Biology. PMID:25911556
Coherent optical OFDM: theory and design.
Shieh, W; Bao, H; Tang, Y
2008-01-21
Coherent optical OFDM (CO-OFDM) has recently been proposed and the proof-of-concept transmission experiments have shown its extreme robustness against chromatic dispersion and polarization mode dispersion. In this paper, we first review the theoretical fundamentals for CO-OFDM and its channel model in a 2x2 MIMO-OFDM representation. We then present various design choices for CO-OFDM systems and perform the nonlinearity analysis for RF-to-optical up-converter. We also show the receiver-based digital signal processing to mitigate self-phase-modulation (SPM) and Gordon-Mollenauer phase noise, which is equivalent to the midspan phase conjugation. PMID:18542158
Theory and phenomenology of coherent neutrino-nucleus scattering
International Nuclear Information System (INIS)
We review the theory and phenomenology of coherent elastic neutrino-nucleus scattering (CEνNS). After a brief introduction, we summarize the places where CEνNS is already in use and then turn to future physics opportunities from CEνNS. CEνNS has been proposed as a way to limit or discover beyond the standard model physics, measure the nuclear-neutron radius and constrain the Weinberg angle
Aljunied, Mariam; Frederickson, Norah
2013-03-01
Central coherence refers to an in-built propensity to form meaningful links over a wide range of stimuli and to generalize over as wide a range of contexts as possible. In children with autism this ability is diminished, and the impact of central coherence deficits in children with autism have previously been observed using static measures of learning, such as reading comprehension test performance. In this study, the relationship between central coherence and more dynamic indicators of learning are investigated. The responses of 52 children with autism (mean age 9:10 years) on a test of central coherence and a dynamic assessment task were analysed. All the children showed significant improvements in dynamic assessment test scores after mediation; however, among those with below average nonverbal intelligence scores, weak central coherence was significantly associated with smaller gains in performance after teaching. Implications for the validity of dynamic assessments for children with autism are discussed. PMID:21715547
Directory of Open Access Journals (Sweden)
Pina Filippello
2013-05-01
Full Text Available The central coherence involves the processes of perceptual coding and attention mechanisms, highly deficient in children with ADHD (Booth & Happé, 2010. According to this theory, also children with autism are overly focused on details to the expense of a global perspective, and this negatively affects their ability to integrate environmental stimuli into a coherent whole (Happé, Booth, Charlton, Hughes, 2006. The aim of this study was to determine differences in central coherence of children with high functioning autism (ASD; n=10, children with attention-deficit hyperactivity disorder (ADHD; n=10 and typically developing peers (n=10. Individuals with ADHD exhibit significant deficits in perceptual skills and problem solving, failing also in mental states understanding tasks. While the children with autism spectrum disorder show impairments in making pragmatic inferences. Future research should therefore concentrate on the investigation of the cognitive and psychological mechanisms underlying these effects.
Theory of coherent phenomena and fundamentals in nuclear resonant scattering
International Nuclear Information System (INIS)
We discuss the general theory of coherent phenomena in nuclear resonant interaction of γ-quanta with crystals. The coherence is realized in collective excitation of the ensemble of nuclei (nuclear exciton) with the conservation of phase memory and in the transformation of a γ-quantum into a quasi-particle of Bloch type in a crystal. The collective character of excitations causes a change in the resonant nuclear parameters and in the lifetime of the excited state. This manifests itself in a speed-up of the decay in the forward direction in a thin crystal and, on the contrary, a strong reduction of elastic scattering in a thick crystal. The reconstruction of the wavefunction of an individual γ-quantum in scattering under Laue or Bragg conditions leads to the suppression effect of inelastic incoherent channels. This effect is discussed in detail. The analysis is based on a derived general system of equations describing the resonant diffraction of γ-quanta in a crystal with an arbitrary relation between the coherent and incoherent channels. This system is used to deduce the equations describing the time-dependent nuclear resonant scattering of synchrotron radiation. We discuss the most instructive experiments with revealing coherent phenomena
Theory of superconductors in coherent longitudinal phonon field
International Nuclear Information System (INIS)
The effect of injection of coherent longitudinal phonons into superconductors is investigated on the basis of the theory of nonequilibrium superconductors developed by Eliashberg. The two basic experiments about this effect, which were explained from different points of view, are explained for a unified point of view. They are (i) the change in the I-V characteristics of S-I-S tunnel junctions due to coherent phonon injection, i.e., phonon-induced tunneling, which was observed by Lax and Vernon, and Abeles and Goldstein, and (ii) an increase in the critical current I/sub c/ in bridge and point-contact junctions, which was observed by Tredwell and Jacobsen. The phonon-induced tunneling was explained in terms of the theory by Tien and Gordon for the photon-induced tunneling. The increase in I/sub c/ was attributed to an enhanced superconductivity, a theory which was first discussed by Eliashberg for superconductors in an electromagnetic field. We found that the Eliashberg effect always exists, but the phonon-induced tunneling is observed only when the space average of the phonon field, i.e., the deformation potential phi (r, t), is nonzero in the superconductor. The tunneling current is given by the superposition of both the effects. We have computed the excess tunneling current due to the Eliashberg effect. If we inject coherent longitudinal phonons parallel to the tunnel junction, they induce a space- and time-varying scalar (deformation) potential propagating with the phonons. We investigated whether we can extend the Josephson equation for the phase difference phi, i.e., phi-dot = 2eV/h, to the space- and time-varying potential difference V due to the phonons. We found that this type of extension is not justified, contrary to the photon-field case
Theory of coherent Raman superradiance imaging of condensed Bose gases
International Nuclear Information System (INIS)
We describe theoretically the dynamics of the off-resonant superradiant Raman scattering of light in a prolate atomic Bose-Einstein condensate, from the initial stages governed by quantum fluctuations to the subsequent semiclassical regime, and within a multimode theory that fully accounts for propagation effects. Our results are in good agreement with recent experimental results that exploit Raman superradiance as an imaging technique to probe the long-range coherence of condensates, including the observed time-dependent spatial features, and account properly for the macroscopic shot-to-shot fluctuations resulting from the quantum noise that initiates the superradiance process
Theory of coherent Raman superradiance imaging of condensed Bose gases
Uys, H.; Meystre, P.
2007-03-01
We describe theoretically the dynamics of the off-resonant superradiant Raman scattering of light in a prolate atomic Bose-Einstein condensate, from the initial stages governed by quantum fluctuations to the subsequent semiclassical regime, and within a multimode theory that fully accounts for propagation effects. Our results are in good agreement with recent experimental results that exploit Raman superradiance as an imaging technique to probe the long-range coherence of condensates, including the observed time-dependent spatial features, and account properly for the macroscopic shot-to-shot fluctuations resulting from the quantum noise that initiates the superradiance process.
Paths to policy coherence to create market economies in Central and Eastern Europe
DEFF Research Database (Denmark)
Careja, Romana
2011-01-01
centralized economies of Central and Eastern Europe into market-driven ones. It shows that government characteristics with likely impact on the quality of policy-making, such as accountability and institutional constraints, are associated with coherent policies only in a limited number of cases. It also shows...... that governments that are not constrained and accountable, formulate coherent policies if they find themselves in contexts that do not pose constraints, or that offer strong incentives. © The Author(s) 2011....
The Theory and Measurement of Macroeconomic Disequilibrium in Centrally Planned Economies
Richard Portes
1986-01-01
The paper considers issues in recent research on macroeconomic equilibrium in centrally planned economies. I defend the explicit aggregative, macroeconomic approach in theory, institutional relationships and measurement. It has offered a fresh, coherent framework for the analysis of many Centrally Planned Economies phenomena, opened up a range of possibilities for empirical investigation, and generated several important spinoffs: work on planners' behaviour; insights into CPE policy problems ...
Viola, Lorenza; Tannor, David
2011-08-01
tomography, which is a necessary 'primitive' for inferring the target quantum state and thereby diagnosing the control performance. Next, the impact of realistic control and system imperfections in continuous-time Markovian feedback strategies for rapid state preparation is analyzed by Combes and Wiseman. A prominent role is played in the special issue by optimal control (OC) approaches, reflecting their central importance for quantum control and QIP. The OC contributions have been divided into two separate sections, depending on whether the target dynamics is modeled as Hamiltonian (section 3) or dissipative (section 4), respectively. The contribution by Beltrani et al deals with `control landscapes', which provide a foundation for analyzing the performance of numerical OC algorithms and their robustness against control errors. Specifically, this paper characterizes geometric properties of the control landscape, relevant to the optimal control of state-to-state transitions. Application of OC theory to the problem of population transfer and coherence enhancement in Λ-systems is studied by Kumar et al, whereas Goerz et al report on the OC-design of a high-fidelity controlled phase-gate in atomic qubits. The robustness of an OC solution is specifically addressed by Negretti et al, along with an approach for identifying easily implementable while still 'close-to-optimal' control pulses. Powerful relaxation-optimized OC schemes (based on so-called opengrape algorithms) for generating unitary target gates in the presence of known dissipation parameters are discussed by Schulte-Herbrüggen et al. Next, Lapert et al report on the problem of time-optimal control of spin-1/2 systems undergoing Bloch relaxation dynamics, highlighting the crucial role played by singular extremals in the control synthesis. Alternative approaches for optimized control of qubits exposed to various decoherence processes are developed by Esher et al and Xue et al, based on a perturbative 'bath
Effective field theory for coherent optical pulse propagation
Park, Q H; Park, Q Han
1996-01-01
Hidden nonabelian symmetries in nonlinear interactions of radiation with matter are clarified. In terms of a nonabelian potential variable, we construct an effective field theory of self-induced transparency, a phenomenon of lossless coherent pulse propagation, in association with Hermitian symmetric spaces G/H. Various new properties of self-induced transparency, e.g. soliton numbers, effective potential energy, gauge symmetry and discrete symmetries, modified pulse area, conserved U(1)-charge etc. are addressed and elaborated in the nondegenerate two-level case where G/H = SU(2)/U(1). Using the U(1)-charge conservation, a new type of analysis on pulse stability is given which agrees with earlier numerical results.
Super-effective-field theory and coherent-anomaly method in cooperative phenomena
International Nuclear Information System (INIS)
Conceptual arguments on the coherent-anomaly method (CAM) and on the super-effective-field theory are presented to explain the basic ideas of these theories. Some possible applications are also suggested
Liouville theory with a central charge less than one
Ribault, Sylvain; Santachiara, Raoul
2015-01-01
We determine the spectrum and correlation functions of Liouville theory with a central charge less than (or equal) one. This completes the definition of Liouville theory for all complex values of the central charge. The spectrum is always spacelike, and there is no consistent timelike Liouville theory. We also study the non-analytic conformal field theories that exist at rational values of the central charge. Our claims are supported by numerical checks of crossing symmetry. We provide Python...
Nonperturbative Formulas for Central Functions of Supersymmetric Gauge Theories
Anselmi, D.; Freedman, D. Z.; Grisaru, M. T.; Johansen, A. A.
1997-01-01
For quantum field theories that flow between ultraviolet and infrared fixed points, central functions, defined from two-point correlators of the stress tensor and conserved currents, interpolate between central charges of the UV and IR critical theories. We develop techniques that allow one to calculate the flows of the central charges and that of the Euler trace anomaly coefficient in a general N=1 supersymmetric gauge theory. Exact, explicit formulas for $SU(N_c)$ gauge theories in the conf...
Theory of the central ion trajectory in the spiral inflector
International Nuclear Information System (INIS)
This paper presents the analytical and numerical theory of the central ion trajectory through the spiral inflector. Analytical expressions for the equations which describe the central ion trajectory are derived
Kocatürk, Tolga; Erkan, Erol; Çakmak, Harun; Kurt Ömürlü, İmran; Dayanır, Volkan
2015-01-01
AbstractObjective: The aim is to compare the central corneal thickness measurements by optical low-coherence reflectometry and contact ultrasonic pachymeter in patients with pseudoexfoliation syndrome, pseudoexfoliation glaucoma, primary open-angle glaucoma as well as healthy subjects.Materials and Methods: We have made a survey of the data of the patients with glaucoma who had been followed for ten years at the Department of Ophthalmology. 148 eyes of 76 patients who had central corneal thic...
Liouville theory with a central charge less than one
Ribault, Sylvain; Santachiara, Raoul
2015-08-01
We determine the spectrum and correlation functions of Liouville theory with a central charge less than (or equal) one. This completes the definition of Liouville theory for all complex values of the central charge. The spectrum is always spacelike, and there is no consistent timelike Liouville theory. We also study the non-analytic conformal field theories that exist at rational values of the central charge. Our claims are supported by numerical checks of crossing symmetry. We provide Python code for computing Virasoro conformal blocks, and correlation functions in Liouville theory and (generalized) minimal models.
Liouville theory with a central charge less than one
Ribault, Sylvain
2015-01-01
We determine the spectrum and correlation functions of Liouville theory with a central charge less than (or equal) one. This completes the definition of Liouville theory for all complex values of the central charge. The spectrum is always spacelike, and there is no consistent timelike Liouville theory. We also study the non-analytic conformal field theories that exist at rational values of the central charge. Our claims are supported by numerical checks of crossing symmetry. We provide Python code for computing Virasoro conformal blocks, and correlation functions in Liouville theory and (generalized) minimal models.
Transport theory: Spatial coherence of random laser emission
Frank, Regine
2012-01-01
Recently random laser reached the stage of technologi- cal applicability. They have already been engineered as coherent microscope light sources in combination with light transport based disordered lenses. The big issue for all kinds of applications is the degree of coherence of the emitted radiation. The lasing spot sizes in dif- ferent regimes may provide different degrees of spatial and temporal coherence and as a consequence they can be perfectly tunable light sources for the case that the modal behavior can be controlled easily. In this letter we investigate the spatial coherence lengths of different random laser samples theoretically. The samples only vary in their filling with spherical ZnO Mie scatterers. Beyond we show, that the scattering mean free paths of random lasers are not only a material characteristics and dependent to the filling, instead the mean free paths change in depth of the sample and therefor depend on the nonlinear self-consistent gain of the random lasing principle.
Chitambar, Eric; Gour, Gilad
2016-07-01
Considerable work has recently been directed toward developing resource theories of quantum coherence. In this Letter, we establish a criterion of physical consistency for any resource theory. This criterion requires that all free operations in a given resource theory be implementable by a unitary evolution and projective measurement that are both free operations in an extended resource theory. We show that all currently proposed basis-dependent theories of coherence fail to satisfy this criterion. We further characterize the physically consistent resource theory of coherence and find its operational power to be quite limited. After relaxing the condition of physical consistency, we introduce the class of dephasing-covariant incoherent operations as a natural generalization of the physically consistent operations. Necessary and sufficient conditions are derived for the convertibility of qubit states using dephasing-covariant operations, and we show that these conditions also hold for other well-known classes of incoherent operations.
Chitambar, Eric; Gour, Gilad
2016-07-15
Considerable work has recently been directed toward developing resource theories of quantum coherence. In this Letter, we establish a criterion of physical consistency for any resource theory. This criterion requires that all free operations in a given resource theory be implementable by a unitary evolution and projective measurement that are both free operations in an extended resource theory. We show that all currently proposed basis-dependent theories of coherence fail to satisfy this criterion. We further characterize the physically consistent resource theory of coherence and find its operational power to be quite limited. After relaxing the condition of physical consistency, we introduce the class of dephasing-covariant incoherent operations as a natural generalization of the physically consistent operations. Necessary and sufficient conditions are derived for the convertibility of qubit states using dephasing-covariant operations, and we show that these conditions also hold for other well-known classes of incoherent operations. PMID:27472102
Glauber theory and the quantum coherence of curvature inhomogeneities
Giovannini, Massimo
2016-01-01
The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose-Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.
Kastlunger, Georg; Stadler, Robert
2015-03-01
To define the conductance of single-molecule junctions with a redox functionality in an electrochemical cell, two conceptually different electron transport mechanisms, namely, coherent tunneling and vibrationally induced hopping, compete with each other, where implicit parameters of the setup such as the length of the molecule and the applied gate voltage decide which mechanism is the dominant one. Although coherent tunneling is most efficiently described within Landauer theory and the common theoretical treatment of electron hopping is based on Marcus theory, both theories are adequate for the processes they describe without introducing accuracy-limiting approximations. For a direct comparison, however, it has to be ensured that the crucial quantities obtained from electronic structure calculations, i.e., the transmission function T (E ) in Landauer theory and the transfer integral V , the reorganization energy λ , and the driving force Δ G0 in Marcus theory, are derived from similar grounds, as pointed out by Nitzan and coworkers in a series of publications. In this paper our framework is a single-particle picture, for which we perform density functional theory calculations for the conductance corresponding to both transport mechanisms for junctions with the central molecule containing one, two, or three Ruthenium centers, from which we extrapolate our results in order to define the critical length of the transition point of the two regimes which we identify at 5.76nm for this type of molecular wire. We also discuss trends in the dependence on an electrochemically induced gate potential.
Coherent backscattering of light by cold atoms: theory meets experiment
Labeyrie, Guillaume; Delande, Dominique; Mueller, Cord A.; Miniatura, Christian; Kaiser, Robin
2002-01-01
Coherent backscattering (CBS) of quasi-resonant light by cold atoms presents some specific features due to the internal structure of the atomic scatterers. We present the first quantitative comparison between the experimentally observed CBS cones and Monte-Carlo calculations which take into account the shape of the atomic cloud as well as the internal atomic structure.
Coherent backscattering of light by cold atoms: theory meets experiment
International Nuclear Information System (INIS)
Coherent backscattering (CBS) of quasi-resonant light by cold atoms presents some specific features due to the internal structure of the atomic scatterers. We present the first quantitative comparison between the experimentally observed CBS cones and Monte Carlo calculations which take into account the shape of the atomic cloud as well as the internal atomic structure. (authors)
Visual processing of coherent rotation in the central visual field: an fMRI study.
Könönen, Mervi; Pääkkönen, Ari; Pihlajamäki, Maija; Partanen, Kaarina; Karjalainen, Pasi A; Soimakallio, Seppo; Aronen, Hannu J
2003-01-01
Functional magnetic resonance imaging was used to determine the brain areas that process coherent motion. To reduce the activity related to eye-movement planning and self-motion perception, rotation was used as coherent motion and the stimulus was restricted to the central visual field. Coherent rotation relative to incoherent random-dot motion resulted in consistent activation in the superior parietal lobule (SPL), in the lateral occipital gyrus (presumptive kinetic occipital region, KO), and in the fusiform gyrus (FG). The main novel finding in present study is the bilateral SPL activation, which has not been found in any previous study contrasting coherent and incoherent motion. It is suggested that the SPL activation is related to form-from-motion processing. The stimulus modification that prevented abrupt appearances of dots at the borders of the stimulus field increased the strength of rolling disk-like percept of the coherent stimulus. This perception of form may also be at least partly responsible for the activation in KO and FG. With this explanation, our three consistent activation areas are in line with previous findings. Furthermore, these results demonstrate that even delicate changes in some stimulus aspects can lead to significant changes in the activation of the brain. PMID:14700259
Simplifying Central Place Theory Using GIS and GPS
Theo, Lisa
2011-01-01
A constant struggle for teachers at all levels is finding ways to successfully teach students complex theories and concepts. Student comprehension is often enhanced by applying these theories and concepts to real world situations. This project demonstrates central place theory by examining highway billboard signs along major Wisconsin highways. In…
G. Ertuğrul Mirza
2014-01-01
Objectives: The aim of this study was to determine if there is a difference in central corneal thickness (CCT) measurements obtained by Cirrus spectral domain optical coherence tomography (SD-OCT) and ultrasonic pachymetry in healthy individuals. Materials and Methods: The study included 50 healthy consecutively selected individuals without ocular or systemic disease. CCT was first measured using OCT, and then using ultrasonic pachymetry. Results: Mean age of the participants was ...
Theory, developments and applications of optical coherence tomography
International Nuclear Information System (INIS)
In this paper, we review the developments in optical coherence tomography (OCT) for three-dimensional non-invasive imaging. A number of different OCT techniques are discussed in some detail including time-domain, frequency-domain, full-field, quantum and Doppler OCT. A theoretical treatment is given and some relevant comparisons made between various implementations. The current and potential applications of OCT are discussed, with close attention paid to biomedical imaging and its metrological issues
Theory, developments and applications of optical coherence tomography
Tomlins, P. H.; Wang, R. K.
2005-08-01
In this paper, we review the developments in optical coherence tomography (OCT) for three-dimensional non-invasive imaging. A number of different OCT techniques are discussed in some detail including time-domain, frequency-domain, full-field, quantum and Doppler OCT. A theoretical treatment is given and some relevant comparisons made between various implementations. The current and potential applications of OCT are discussed, with close attention paid to biomedical imaging and its metrological issues.
Stimulus control topography coherence theory: Foundations and extensions
McIlvane, William J.; Dube, William V.
2003-01-01
Stimulus control topography refers to qualitative differences among members of a functional stimulus class. Stimulus control topography coherence refers to the degree of concordance between the stimulus properties specified as relevant by the individual arranging a reinforcement contingency (behavior analyst, experimenter, teacher, etc.) and the stimulus properties that come to control the behavior of the organism (experimental subject, student, etc.) that experiences those contingencies. Thi...
Theory and practice of dressed coherent states in circuit QED
Wilhelm, Frank; Govia, Luke C. G.
In the dispersive regime of qubit-cavity coupling, classical cavity drive populates the cavity, but leaves the qubit state unaffected. However, the dispersive Hamiltonian is derived after both a frame transformation and an approximation. Therefore, to connect to external experimental devices, the inverse frame transformation from the dispersive frame back to the lab frame is necessary. We show that in the lab frame the system is best described by an entangled state known as the dressed coherent state, and thus even in the dispersive regime, entanglement is generated between the qubit and the cavity. Also, we show that further qubit evolution depends on both the amplitude and phase of the dressed coherent state. This provides a limitation to readout in the dispersive regime. We show that only in the limit of infinite measurement time is this protocol QND, as the formation of a dressed coherent state in the qubit-cavity system applies an effective rotation to the qubit state. We show how this rotation can be corrected by a unitary operation, leading to improved qubit initialization by measurement and unitary feedback.] L.C.G. Govia and F.K. Wllhelm Phys. Rev. Applied 4, 054001 (2015) LC.G. Govia and F.K. Wilhelm, arXiv:1506.04997 Supported by the ARO under contract W911NF-14-1-0080 and the European Union through ScaleQIT. LCGG acknowledges support from NSERC through an NSERC PGS-D.
Maruo, Daiki; Utsunomiya, Shoko; Yamamoto, Yoshihisa
2016-01-01
We present the quantum theory of coherent Ising machines based on networks of degenerate optical parametric oscillators (DOPOs). In a simple model consisting of two coupled DOPOs, both positive-$P$ representation and truncated Wigner representation predict quantum correlation and inseparability between the two DOPOs in spite of the open-dissipative nature of the system. Here, we apply the truncated Wigner representation method to coherent Ising machines with thermal, vacuum, and squeezed rese...
Søren Ventegodt; Trine Flensborg-Madsen; Niels Jørgen Andersen; Joav Merrick
2005-01-01
A theoretical framework of existential coherence is presented, explaining how health, quality of life (QOL), and the ability to function were originally created and developed to rehabilitate human life from an existential perspective. The theory is inspired by the work of Aaron Antonovsky and explains our surprising recent empirical findings—that QOL, health, and ability primarily are determined by our consciousness. The theory is a matrix of nine key elements in five layers: (1) coherence; (...
To the theory of coherent resonance tunneling of interacting electrons
International Nuclear Information System (INIS)
In terms of the model of coherent tunneling of interacting electrons one determined analytical solutions for the Schroedinger equation for a two-barrier structure (a resonance and tunnel diode) with the open boundary conditions. One derived simple expressions for resonance current enabling to analyze the volt-ampere characteristics, hysteresis occurrence conditions and its peculiarities depending on the parameters of a resonance-tunnel diode. Hysteresis is shown to be realized if current is higher than a certain critical value proportional to resonance level width square
A coherent modified Redfield theory for excitation energy transfer in molecular aggregates
Energy Technology Data Exchange (ETDEWEB)
Hwang-Fu, Yu-Hsien; Chen, Wei; Cheng, Yuan-Chung, E-mail: yuanchung@ntu.edu.tw
2015-02-02
Highlights: • A CMRT method for coherent energy transfer in molecular aggregates was developed. • Applicability of the method was verified in two-site systems with various parameters. • CMRT accurately describes population dynamics in the FMO-complex. • The method is accurate in a large parameter space and computationally efficient. - Abstract: Excitation energy transfer (EET) is crucial in photosynthetic light harvesting, and quantum coherence has been recently proven to be a ubiquitous phenomenon in photosynthetic EET. In this work, we derive a coherent modified Redfield theory (CMRT) that generalizes the modified Redfield theory to treat coherence dynamics. We apply the CMRT method to simulate the EET in a dimer system and compare the results with those obtained from numerically exact path integral calculations. The comparison shows that CMRT provides excellent computational efficiency and accuracy within a large EET parameter space. Furthermore, we simulate the EET dynamics in the FMO complex at 77 K using CMRT. The results show pronounced non-Markovian effects and long-lasting coherences in the ultrafast EET, in excellent agreement with calculations using the hierarchy equation of motion approach. In summary, we have successfully developed a simple yet powerful framework for coherent EET dynamics in photosynthetic systems and organic materials.
A coherent modified Redfield theory for excitation energy transfer in molecular aggregates
International Nuclear Information System (INIS)
Highlights: • A CMRT method for coherent energy transfer in molecular aggregates was developed. • Applicability of the method was verified in two-site systems with various parameters. • CMRT accurately describes population dynamics in the FMO-complex. • The method is accurate in a large parameter space and computationally efficient. - Abstract: Excitation energy transfer (EET) is crucial in photosynthetic light harvesting, and quantum coherence has been recently proven to be a ubiquitous phenomenon in photosynthetic EET. In this work, we derive a coherent modified Redfield theory (CMRT) that generalizes the modified Redfield theory to treat coherence dynamics. We apply the CMRT method to simulate the EET in a dimer system and compare the results with those obtained from numerically exact path integral calculations. The comparison shows that CMRT provides excellent computational efficiency and accuracy within a large EET parameter space. Furthermore, we simulate the EET dynamics in the FMO complex at 77 K using CMRT. The results show pronounced non-Markovian effects and long-lasting coherences in the ultrafast EET, in excellent agreement with calculations using the hierarchy equation of motion approach. In summary, we have successfully developed a simple yet powerful framework for coherent EET dynamics in photosynthetic systems and organic materials
Theory of nonlinear phononics for coherent light control of solids
A. Subedi; A. Cavalleri; Georges, A.
2014-01-01
We present a microscopic theory for ultrafast control of solids with high-intensity terahertz frequency optical pulses. When resonant with selected infrared-active vibrations, these pulses transiently modify the crystal structure and lead to new collective electronic properties. The theory predicts the dynamical path taken by the crystal lattice using first-principles calculations of the energy surface and classical equations of motion, as well as symmetry considerations. Two classes of dynam...
Quantum Optics Theory of Electronic Noise in Coherent Conductors.
Grimsmo, Arne L; Qassemi, Farzad; Reulet, Bertrand; Blais, Alexandre
2016-01-29
We consider the electromagnetic field generated by a coherent conductor in which electron transport is described quantum mechanically. We obtain an input-output relation linking the quantum current in the conductor to the measured electromagnetic field. This allows us to compute the outcome of measurements on the field in terms of the statistical properties of the current. We moreover show how under ac bias the conductor acts as a tunable medium for the field, allowing for the generation of single- and two-mode squeezing through fermionic reservoir engineering. These results explain the recently observed squeezing using normal tunnel junctions [G. Gasse et al., Phys. Rev. Lett. 111, 136601 (2013); J.-C. Forgues et al., Phys. Rev. Lett. 114, 130403 (2015)]. PMID:26871330
Automatic theory generation from analyst text files using coherence networks
Shaffer, Steven C.
2014-05-01
This paper describes a three-phase process of extracting knowledge from analyst textual reports. Phase 1 involves performing natural language processing on the source text to extract subject-predicate-object triples. In phase 2, these triples are then fed into a coherence network analysis process, using a genetic algorithm optimization. Finally, the highest-value sub networks are processed into a semantic network graph for display. Initial work on a well- known data set (a Wikipedia article on Abraham Lincoln) has shown excellent results without any specific tuning. Next, we ran the process on the SYNthetic Counter-INsurgency (SYNCOIN) data set, developed at Penn State, yielding interesting and potentially useful results.
Quantum Optics Theory of Electronic Noise in Coherent Conductors
Grimsmo, Arne L.; Qassemi, Farzad; Reulet, Bertrand; Blais, Alexandre
2016-01-01
We consider the electromagnetic field generated by a coherent conductor in which electron transport is described quantum mechanically. We obtain an input-output relation linking the quantum current in the conductor to the measured electromagnetic field. This allows us to compute the outcome of measurements on the field in terms of the statistical properties of the current. We moreover show how under ac bias the conductor acts as a tunable medium for the field, allowing for the generation of single- and two-mode squeezing through fermionic reservoir engineering. These results explain the recently observed squeezing using normal tunnel junctions [G. Gasse et al., Phys. Rev. Lett. 111, 136601 (2013); J.-C. Forgues et al., Phys. Rev. Lett. 114, 130403 (2015)].
Correct Path-Integral Formulation of Quantum Thermal Field Theory in Coherent State Representation
Institute of Scientific and Technical Information of China (English)
SU Jun-Chen; ZHENG Fu-Hou
2005-01-01
The path-integral quantization of thermal scalar, vector, and spinor fields is performed newly in the coherent-state representation. In doing this, we choose the thermal electrodynamics and ψ4 theory as examples. By this quantization, correct expressions of the partition functions and the generating functionals for the quantum thermal electrodynamics and ψ4 theory are obtained in the coherent-state representation. These expressions allow us to perform analytical calculations of the partition functions and generating functionals and therefore are useful in practical applications. Especially, the perturbative expansions of the generating functionals are derived specifically by virtue of the stationary-phase method. The generating functionals formulated in the position space are re-derived from the ones given in the coherent-state representation.
The Development of a Comprehensive and Coherent Theory of Learning
Illeris, Knud
2015-01-01
This article is an account of how the author developed a comprehensive understanding of human learning over a period of almost 50 years. The learning theory includes the structure of learning, different types of learning, barriers of learning as well as how individual dispositions, age, the learning environment and general social and societal…
Coherent States and Spontaneous Symmetry Breaking in Light Front Scalar Field Theory
Energy Technology Data Exchange (ETDEWEB)
Vary, J.P.; /Iowa State U. /LLNL, Livermore /SLAC; Chakrabarti, D.; /Florida U.; Harindranath, A.; /Saha Inst.; Lloyd, R.; /Arkansas State U.; Martinovic, L.; /Bratislava,; Spence, J.R.; /Iowa State U.
2005-12-14
Recently developed nuclear many-body techniques provide novel results when applied to constituent quark models and to light-front scalar field theory. We show how spontaneous symmetry breaking arises and is consistent with a coherent state ansatz in a variational treatment. The kink and the kink-antikink topological features are identified and the onset of symmetry restoration is demonstrated.
Theory of nonlinear phononics for coherent light control of solids
Subedi, Alaska; Cavalleri, Andrea; Georges, Antoine
2014-06-01
We present a microscopic theory for ultrafast control of solids with high-intensity terahertz frequency optical pulses. When resonant with selected infrared-active vibrations, these pulses transiently modify the crystal structure and lead to new collective electronic properties. The theory predicts the dynamical path taken by the crystal lattice using first-principles calculations of the energy surface and classical equations of motion, as well as symmetry considerations. Two classes of dynamics are identified. In the perturbative regime, displacements along the normal mode coordinate of symmetry-preserving Raman active modes can be achieved by cubic anharmonicities. This explains the light-induced insulator-to-metal transition reported experimentally in manganites. We predict a regime in which ultrafast instabilities that break crystal symmetry can be induced. This nonperturbative effect involves a quartic anharmonic coupling and occurs above a critical threshold, below which the nonlinear dynamics of the driven mode displays softening and dynamical stabilization.
Breaking the coherence barrier: A new theory for compressed sensing
Adcock, Ben; Hansen, Anders C.; Poon, Clarice; Roman, Bogdan
2013-01-01
This paper provides an extension of compressed sensing which bridges a substantial gap between existing theory and its current use in real-world applications. It introduces a mathematical framework that generalizes the three standard pillars of compressed sensing - namely, sparsity, incoherence and uniform random subsampling - to three new concepts: asymptotic sparsity, asymptotic incoherence and multilevel random sampling. The new theorems show that compressed sensing is also possible, and r...
The AdS3 central charge in string theory
International Nuclear Information System (INIS)
We evaluate the vacuum expectation value of the central charge operator in string theory in an AdS3 vacuum. Our calculation provides a rare non-zero one-point function on a spherical worldsheet. The evaluation involves the regularization both of a worldsheet ultraviolet divergence (associated to the infinite volume of the conformal Killing group), and a space-time infrared divergence (corresponding to the infinite volume of space-time). The two divergences conspire to give a finite result, which is the classical general relativity value for the central charge, corrected in bosonic string theory by an infinite series of tree level higher derivative terms.
Analytic function theory of several variables elements of Oka’s coherence
Noguchi, Junjiro
2016-01-01
The purpose of this book is to present the classical analytic function theory of several variables as a standard subject in a course of mathematics after learning the elementary materials (sets, general topology, algebra, one complex variable). This includes the essential parts of Grauert–Remmert's two volumes, GL227(236) (Theory of Stein spaces) and GL265 (Coherent analytic sheaves) with a lowering of the level for novice graduate students (here, Grauert's direct image theorem is limited to the case of finite maps). The core of the theory is "Oka's Coherence", found and proved by Kiyoshi Oka. It is indispensable, not only in the study of complex analysis and complex geometry, but also in a large area of modern mathematics. In this book, just after an introductory chapter on holomorphic functions (Chap. 1), we prove Oka's First Coherence Theorem for holomorphic functions in Chap. 2. This defines a unique character of the book compared with other books on this subject, in which the notion of coherence appear...
Hahn, Noemi; Snedeker, Jesse; Rabagliati, Hugh
2015-12-01
Individuals with autism spectrum disorders (ASD) have often been reported to have difficulty integrating information into its broader context, which has motivated the Weak Central Coherence theory of ASD. In the linguistic domain, evidence for this difficulty comes from reports of impaired use of linguistic context to resolve ambiguous words. However, recent work has suggested that impaired use of linguistic context may not be characteristic of ASD, and is instead better explained by co-occurring language impairments. Here, we provide a strong test of these claims, using the visual world eye tracking paradigm to examine the online mechanisms by which children with autism resolve linguistic ambiguity. To address concerns about both language impairments and compensatory strategies, we used a sample whose verbal skills were strong and whose average age (7; 6) was lower than previous work on lexical ambiguity resolution in ASD. Participants (40 with autism and 40 controls) heard sentences with ambiguous words in contexts that either strongly supported one reading or were consistent with both (John fed/saw the bat). We measured activation of the unintended meaning through implicit semantic priming of an associate (looks to a depicted baseball glove). Contrary to the predictions of weak central coherence, children with ASD, like controls, quickly used context to resolve ambiguity, selecting appropriate meanings within a second. We discuss how these results constrain the generality of weak central coherence. PMID:25820816
A feasible central limit theory for realised volatility under leverage
DEFF Research Database (Denmark)
Barndorff-Nielsen, Ole Eiler; Shephard, Neil
In this note we show that the feasible central limit theory for realised volatility and realised covariation recently developed by Barndor-Nielsen and Shephard applies under arbitrary diusion based leverage eects. Results from a simulation experiment suggest that the feasible version of the limit...
Centrality of the collision and random matrix theory
Institute of Scientific and Technical Information of China (English)
Z.Wazir
2010-01-01
I discuss the results from a study of the central 12CC collisions at 4.2 A GeV/c.The data have been analyzed using a new method based on the Random Matrix Theory.The simulation data coming from the Ultra Relativistic Quantum Molecular Dynamics code were used in the analyses.I found that the behavior of the nearest neighbor spacing distribution for the protons,neutrons and neutral pions depends critically on the multiplicity of secondary particles for simulated data.I conclude that the obtained results offer the possibility of fixing the centrality using the critical values of the multiplicity.
Danner, Unna N.; Sanders, Nicole; Smeets, Paul A. M.; van Meer, Floor; Adan, Roger A. H.; Hoek, Hans W.; van Elburg, Annemarie A.
2012-01-01
Objective: The purpose of this study is to examine set-shifting, central coherence, and decision making in women currently ill with anorexia nervosa (AN), women recovered from AN, and healthy control women. We aim to test whether these neuropsychological weaknesses persist after recovery, and explor
Czech Academy of Sciences Publication Activity Database
Zuchova, S.; Kuběna, Aleš Antonín; Erler, Theodore; Papežová, H.
2013-01-01
Roč. 18, č. 4 (2013), s. 421-428. ISSN 1124-4909 Institutional support: RVO:67985556 Keywords : visuospatial memory, * central coherence * Rey Complex Figure Test, * Anorexia nervosa, * neuropsychology Subject RIV: FL - Psychiatry, Sexuology Impact factor: 0.680, year: 2013
Riches, N. G.; Loucas, T.; Baird, G.; Charman, T.; Simonoff, E.
2016-01-01
According to the weak central coherence (CC) account individuals with autism spectrum disorders (ASD) exhibit enhanced local processing and weak part-whole integration. CC was investigated in the verbal domain. Adolescents, recruited using a 2 (ASD status) by 2 (language impairment status) design, completed an aural forced choice comprehension…
Maruo, Daiki; Utsunomiya, Shoko; Yamamoto, Yoshihisa
2016-08-01
We present the quantum theory of coherent Ising machines based on networks of degenerate optical parametric oscillators (DOPOs). In a simple model consisting of two coupled DOPOs, both positive-P representation and truncated Wigner representation predict quantum correlation and inseparability between the two DOPOs in spite of the open-dissipative nature of the system. Here, we apply the truncated Wigner representation method to coherent Ising machines with thermal, vacuum, and squeezed reservoir fields. We find that the probability of finding the ground state of a one-dimensional Ising model increases substantially as a result of reducing excess thermal noise and squeezing the incident vacuum fluctuation on the out-coupling port.
Quasiclassical theory of coherent charge transport into multi-band superconductors
International Nuclear Information System (INIS)
We formulate a quasiclassical theory of coherent charge transport in junctions involving multi-band iron-based superconductors (FeBSs), explicitly taking into account the complex excitation spectrum and unconventional nature of superconducting pairing in FeBSs. We perform calculations assuming intraorbital superconducting pairing in FeBSs described by the s± model. Further, taking into account that the Fermi energy in FeBSs is much larger than the superconducting gaps, we formulate the quasiclassical approximation. This formulation makes our theory suitable for straightforward numerical calculations and more practical compared to previous approaches. Based on this quasiclassical theory, we calculated the conductance of a junction between a single band normal metal and an FeBS. (paper)
Photon wave functions, wave-packet quantization of light, and coherence theory
International Nuclear Information System (INIS)
The monochromatic Dirac and polychromatic Titulaer-Glauber quantized field theories (QFTs) of electromagnetism are derived from a photon-energy wave function in much the same way that one derives QFT for electrons, i.e., by quantization of a single-particle wave function. The photon wave function and its equation of motion are established from the Einstein energy-momentum-mass relation, assuming a local energy density. This yields a theory of photon wave mechanics (PWM). The proper Lorentz-invariant single-photon scalar product is found to be non-local in coordinate space, and is shown to correspond to orthogonalization of the Titulaer-Glauber wave-packet modes. The wave functions of PWM and mode functions of QFT are shown to be equivalent, evolving via identical equations of motion, and completely describe photonic states. We generalize PWM to two or more photons, and show how to switch between the PWM and QFT viewpoints. The second-order coherence tensors of classical coherence theory and the two-photon wave functions are shown to propagate equivalently. We give examples of beam-like states, which can be used as photon wave functions in PWM, or modes in QFT. We propose a practical mode converter based on spectral filtering to convert between wave packets and their corresponding biorthogonal dual wave packets
Directory of Open Access Journals (Sweden)
G. Ertuğrul Mirza
2014-08-01
Full Text Available Objectives: The aim of this study was to determine if there is a difference in central corneal thickness (CCT measurements obtained by Cirrus spectral domain optical coherence tomography (SD-OCT and ultrasonic pachymetry in healthy individuals. Materials and Methods: The study included 50 healthy consecutively selected individuals without ocular or systemic disease. CCT was first measured using OCT, and then using ultrasonic pachymetry. Results: Mean age of the participants was 31.44 years. Mean CCT measured using SD-OCT was 531.78 µm versus 535.15 µm by ultrasonic pachymetry. Mean CCT measurement obtained by Cirrus SD-OCT showed statistically significant difference by approximately 3.37 µm than the one obtained by ultrasonic pachymetry (t-test, p<0.05; however, Bland-Altman analysis proved that there was high concordance between the measurements. Conclusion: CCT measurements obtained by Cirrus SD-OCT were very similar to those obtained by ultrasonic pachymetry, and as such we think that Cirrus SD-OCT can be used in our present ophthalmology practice to measure OCT. (Turk J Ophthalmol 2014; 44: 259-62
International Nuclear Information System (INIS)
Objective: To assess the agreement of central corneal thickness (CCT) measured by anterior chamber-optical coherence tomography (AC-OCT) and ultrasonic pachymeter and provide an objective basis for clinical application of AC-OCT. Methods: CCT of 150 college student volunteers (300 eyes) measured by two devices were obtained. The data was analyzed by paired t test and Pearson correlation analysis. Bland-Altman plot and Mountain plot were used to assess the agreement. Results: The mean CCT values were (530.05 ± 33.611) μm measured by AC-OCT and (543.68 ± 35.088) μm measured by ultrasonic pachymeter. Regression analysis showed a high correlation between the values obtained by both devices (r=0.960, P<0.001). Compared with AC-OCT, ultrasonic pachymeter overestimated the CCT by a mean of 13.62 μm. The two modalities had incomparable results. Conclusion: It is important to be noted in clinical practice that the measurements acquired by these two modalities are not directly interchangeable. However, the CCT measurements by the AC-OCT and ultrasonic pachymeter are highly correlated. AC-OCT is an effective method to observe the changes of the corneal thickness in the long term. (authors)
Role of diffusional coherency strain theory in the discontinuous precipitation in Mg–Al alloy
Indian Academy of Sciences (India)
K T Kashyap; C Ramachandra; M Sujatha; B Chatterji
2000-02-01
Discontinuous precipitation (DP) occurs in many alloy systems under certain conditions. It is called discontinuous precipitation because precipitation occurs on prior matrix grain boundaries followed by grain boundary movement. The DP nodule consists of alternate lamellae of the precipitate and the matrix respectively. The chemical driving force for DP is one of solute supersaturation. Although solute supersaturation is responsible for precipitation, it has to be coupled with another driving force to explain grain boundary migration. This coupling driving force has been identified to be diffusional coherency strain which has been verified to be active in diffusion induced grain boundary migration and liquid film migration. To test diffusional coherency strain theory for discontinuous precipitation Mg–7Al and Mg–7Al–1Pb alloys were studied. While the fraction transformed was high at 6% in Mg–7Al alloy, it was significantly low at 2% in Mg–7Al–1Pb alloy. The velocity of DP nodules decreased by half in alloy with Pb as compared to the alloy without Pb. Theoretical calculations also predict that the misfit parameter th decreases with the addition of Pb. These observations are an evidence to the fact that diffusional coherency strain is the most active driving force for the movement of the grain boundaries of the DP nodules during discontinuous precipitation in Mg–Al alloy.
Nien, Benjamin Chih-Chien
2006-01-01
This paper attempts to analyze “central place theory” of spatial economics based on “supply and demand theory” in microeconomics and “field theory” in physics, and also discuss their relationship. Three most important research findings are described below. Firstly, the concept of market equilibrium could be expressed in the mathematical form of physics field theory under proper hypothesis. That is because the most important aspect of field theory model is that complex analysis is taken as a k...
Directory of Open Access Journals (Sweden)
Søren Ventegodt
2005-01-01
Full Text Available A theoretical framework of existential coherence is presented, explaining how health, quality of life (QOL, and the ability to function were originally created and developed to rehabilitate human life from an existential perspective. The theory is inspired by the work of Aaron Antonovsky and explains our surprising recent empirical findings—that QOL, health, and ability primarily are determined by our consciousness. The theory is a matrix of nine key elements in five layers: (1 coherence; (2 purpose and talent; (3 consciousness, love, and physicality/sexuality; (4 light and joy; and (5 QOL/meaning of life. The layer above causes the layer below, with the layer of QOL again feeding the fundamental layer of coherence. The model holds the person responsible for his or her own degree of reality, happiness, and being present. The model implies that when a person takes responsibility in all nine “dimensions” of life, he or she can improve and develop health, the ability to function, all aspects of QOL, and the meaning of life. The theory of existential coherence integrates a wide range of QOL theories from Jung and Maslow to Frankl and Wilber. It is a nine-ray theory in accordance with Gurjieff's enneagram and the old Indian chakra system. It can be used in the holistic medical clinic and in existential coaching. Love is in the center of the model and rehabilitation of love in its broadest sense is, accordingly, the essence of holistic medicine. To know yourself, your purpose of life (life mission and talents, and taking these into full use and becoming coherent with life inside and reality outside is what human life is essentially about. The new model has been developed to integrate the existing knowledge in the complex field of holistic medicine. Its strength is that it empowers the holistic physician to treat the patient with even severe diseases and can also be used for existential rehabilitation, holistic psychiatry, and sexology. Its major
Ventegodt, Søren; Flensborg-Madsen, Trine; Andersen, Niels Jørgen; Merrick, Joav
2005-05-01
A theoretical framework of existential coherence is presented, explaining how health, quality of life (QOL), and the ability to function were originally created and developed to rehabilitate human life from an existential perspective. The theory is inspired by the work of Aaron Antonovsky and explains our surprising recent empirical findings -- that QOL, health, and ability primarily are determined by our consciousness. The theory is a matrix of nine key elements in five layers: (1) coherence; (2) purpose and talent; (3) consciousness, love, and physicality/sexuality; (4) light and joy; and (5) QOL/meaning of life. The layer above causes the layer below, with the layer of QOL again feeding the fundamental layer of coherence. The model holds the person responsible for his or her own degree of reality, happiness, and being present. The model implies that when a person takes responsibility in all nine "dimensions" of life, he or she can improve and develop health, the ability to function, all aspects of QOL, and the meaning of life. The theory of existential coherence integrates a wide range of QOL theories from Jung and Maslow to Frankl and Wilber. It is a nine-ray theory in accordance with Gurjieff's enneagram and the old Indian chakra system. It can be used in the holistic medical clinic and in existential coaching. Love is in the center of the model and rehabilitation of love in its broadest sense is, accordingly, the essence of holistic medicine. To know yourself, your purpose of life (life mission) and talents, and taking these into full use and becoming coherent with life inside and reality outside is what human life is essentially about. The new model has been developed to integrate the existing knowledge in the complex field of holistic medicine. Its strength is that it empowers the holistic physician to treat the patient with even severe diseases and can also be used for existential rehabilitation, holistic psychiatry, and sexology. Its major weakness is
A Theory of Dynamic Imaging of Coherent Molecular Rotations by High Harmonic Generation
Faisal, F. H. M.; Abdurrouf, A.
A dynamic theory of mapping coherent molecular motions from high harmonic generation signals is presented. Application to mapping of coherent rotational motions of linear molecules is made. Results of concrete calculations for N2, O2 and CO2 are analyzed both in time and frequency domains. A "magic angle" for the polarization geometry is predicted at which the HHG signals for all pump-probe delay times become equal for linear molecules of σg orbital symmetry. In contrast only a "crossing neighborhood" near the magic angle is predicted for molecules with orbitals of π symmetry. They are expected to help in identifying the orbital symmetry in the inverse problem of orbital reconstruction from experimental data. Comparison with available experimental data show remarkable agreement with all the salient properties of dynamic HHG signals of linear diatomic molecules, N2 and O2, and some simple organic molecules. Additional results for the triatomic molecule CO2 are discussed that might help to test the theory further.
International Nuclear Information System (INIS)
In this study, we investigate the accuracy of a recently developed coherent modified Redfield theory (CMRT) in simulating excitation energy transfer (EET) dynamics. The CMRT is a secular non-Markovian quantum master equation that is derived by extending the modified Redfield theory to treat coherence dynamics in molecular excitonic systems. Herein, we systematically survey the applicability of the CMRT in a large EET parameter space through the comparisons of the CMRT EET dynamics in a dimer system with the numerically exact results. The results confirm that the CMRT exhibits a broad applicable range and allow us to locate the specific parameter regimes where CMRT fails to provide adequate results. Moreover, we propose an accuracy criterion based on the magnitude of second-order perturbation to characterize the applicability of CMRT and show that the criterion summarizes all the benchmark results and the physics described by CMRT. Finally, we employ the accuracy criterion to quantitatively compare the performance of CMRT to that of a small polaron quantum master equation approach. The comparison demonstrates the complementary nature of these two methods, and as a result, the combination of the two methods provides accurate simulations of EET dynamics for the full parameter space investigated in this study. Our results not only delicately evaluate the applicability of the CMRT but also reveal new physical insights for factors controlling the dynamics of EET that should be useful for developing more accurate and efficient methods for simulations of EET dynamics in molecular aggregate systems
Urbanek, Diana C.; Berg, Mark A.
2007-07-01
For coherent Raman spectroscopies, common femtosecond pulses often lie in an intermediate regime: their bandwidth is too wide for measurements in the frequency domain, but their temporal width is too broad for homodyne measurements in the time domain. A recent paper [S. Nath et al., Phys. Rev. Lett. 97, 267401 (2006)] showed that complete Raman spectra can be recovered from intermediate length pulses by using simultaneous time and frequency detection (TFD). Heterodyne detection and a phase-stable local oscillator at the anti-Stokes frequency are not needed with TFD. This paper examines the theory of TFD Raman in more detail; a companion paper tests the results on experimental data. Model calculations illustrate how information on the Raman spectrum is transferred from the frequency domain to the time domain as the pulse width shortens. When data are collected in both dimensions, the Raman spectrum is completely determined to high resolution, regardless of the probe pulse width. The loss of resolution in many femtosecond coherent Raman experiments is due to the restriction to one-dimensional data collection, rather than due to a fundamental restriction based on the pulse width.
Microscopic theory of coherent and incoherent optical properties of semiconductor heterostructures
Energy Technology Data Exchange (ETDEWEB)
Schaefer, Martin
2008-09-02
An important question is whether there is a regime in which lasing from indirect semiconductors is possible. Thus, we discuss this question in this thesis. It is shown that under incoherent emission conditions it is possible to create an exciton condensate in multiple-quantum-well (MQW) systems. The influence of a MQW structure on the exciton lifetime is investigated. For the description of the light-matter interaction of a QW in the coherent excitation regime, the semiconductor Bloch equation (SBE) are used. The incoherent regime is described by the semiconductor luminescence equations (SLE). In principle it is even possible to couple SBE and SLE. The resulting theory is able to describe interactions between coherent and incoherent processes we investigate both, the coherent and the incoherent light-emission regime. Thus we define the investigated system and introduce the many-body Hamiltonian that describes consistently the light-matter interaction in the classical and the quantum limit. We introduce the SBE that allow to compute the light-matter interaction in the coherent scenario. The extended scattering model is used to investigate the absorption of a Ge QW for different time delays after the excitations. In this context, we analyze whether there is a regime in which optical gain can be realized. Then we apply a transfer-matrix method to include into our calculations the influence of the dielectric environment on the optical response. Thereafter the SLE for a MQW system are introduced. We derive a scheme that allows for decoupling environmental effects from the pure PL-emission properties of the QW. The PL of the actual QW system is obtained by multiplying this filter function and the free-space PL that describes the quantum emission into a medium with spatially constant background-refractive index. It is studied how the MQW-Bragg structure influences the PL-emission properties compared to the emission of a single QW device. As a last feature, it is shown
Coherent-structure theory and bound-state formation in electrified falling films
Lin, Te-Sheng; Tseluiko, Dmitri; Blyth, Mark; Kalliadasis, Serafim
2015-11-01
We consider a perfectly conducting viscous liquid film flowing down an inclined wall and subjected to a normal electric filed. The electric field introduces a destabilizing non-local term in the long-wave evolution equation and the solutions may evolve into arrays of interacting pulses. We develop a weak-interaction theory for these pulses using elements from previous coherent-structure interaction theories we have developed. We show that the standard first-neighbor approximation is no longer valid and it is essential to take into account long-range interactions. We also develop numerical continuation techniques to explore bifurcation diagrams in systems possessing translational symmetry, including traveling waves and spatially varying time-periodic solutions. We find that each bound state bifurcates from the primary branch when continuing with respect to the domain size, and we then construct full bifurcation diagrams taking into account all the bound states. Finally, we compare the bound states for the long-wave evolution equation with the ones found in Stokes calculations and find excellent agreement.
Emre Hekimoglu; Muhammet Kazım Erol; Devrim Toslak; Deniz Turgut Coban; Berna Doğan; Ozgur Yucel
2015-01-01
Purpose. To evaluate the repeatability of measurement of central corneal thickness (CCT) by spectral domain optical coherence (SD-OCT) in premature infants and compare it to CCT measurement by ultrasonic pachymetry (USP). Methods. Three CCT measurements of the left eyes of 50 premature infants were obtained by SD-OCT using the iVue system. 10 CCT measurements of each 28 left eyes of 28 infants were obtained by USP using the Pacscan 300P system. Bland-Altman plots were developed and the limit ...
Directory of Open Access Journals (Sweden)
Otacílio de Oliveira Maia Júnior
2006-04-01
Full Text Available OBJETIVO: Avaliar a tomografia de coerência óptica como método objetivo de diagnóstico e de seguimento da coriorretinopatia serosa central. MÉTODOS: Estudo observacional descritivo de 16 (dezesseis olhos de portadores de coriorretinopatia serosa central unilateral, em fase aguda. Estes pacientes foram submetidos à medida da acuidade visual e a exame oftalmológico completo, incluindo biomicroscopia da mácula, angiofluoresceinografia e tomografia de coerência óptica. Nenhum dos pacientes foi submetido a qualquer tipo de tratamento. RESULTADO: Dos 16 casos consecutivos de coriorretinopatia serosa central, 12 pacientes completaram o seguimento até a resolução da doença. A idade variou entre 27 e 50 anos, com média de 38,9 anos. A predominância foi do sexo masculino. Na tomografia de coerência óptica, o descolamento da retina neurossensorial foi observado em todos os casos e 33,3% dos pacientes apresentaram descolamento do epitélio pigmentado da retina. Houve diferença significativa em todas as variáveis estudadas, constatando melhora na acuidade visual, diminuição na espessura e no volume macular na resolução da doença. CONCLUSÃO: Tomografia de coerência óptica mostrou boa eficácia para detectar e quantificar alterações maculares em olhos com coriorretinopatia serosa central, podendo ser útil em avaliações clínicas na fase aguda e na resolução da doença.PURPOSE: To evaluate optical coherence tomography as an objective diagnostic and follow-up method for central serous chorioretinopathy. METHODS: Observational descriptive study of 16 (sixteen eyes of 16 patients with unilateral acute central serous chorioretinopathy. These patients had their visual acuity measured and complete ophthalmological examination was performed, including macular slit lamp examination, angiofluoresceinography and optical coherence tomography. No treatment was given to any patient. RESULTS: Of the 16 central serous chorioretinopathy eyes
Coherent neutrinoproduction of photons and pions in a chiral effective field theory for nuclei
Zhang, Xilin; Serot, Brian D.
2012-09-01
Background: The neutrinoproduction of photons and pions from nucleons and nuclei is relevant to the background analysis in neutrino-oscillation experiments [for example, the MiniBooNE; MiniBooNE Collaboration, A. A. Aquilar-Arevalo , Phys. Rev. Lett.0031-900710.1103/PhysRevLett.100.032301 100, 032301 (2008)]. The production from nucleons and incoherent production with Eν⩽0.5GeV have been studied in B. D. Serot and X. Zhang, Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.86.015501 86, 015501 (2012); and X. Zhang and B. D. Serot, Phys. Rev. C1110-865710.1103/PhysRevC.86.035502 86, 035502 (2012).Purpose: Study coherent productions with Eν⩽0.5GeV. Also address the contributions of two contact terms in neutral current (NC) photon production that are partially related to the proposed anomalous ω(ρ), Z boson, and photon interactions.Methods: We work in the framework of a Lorentz-covariant effective field theory (EFT), which contains nucleons, pions, the Δ (1232) (Δs), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields, and incorporates a nonlinear realization of (approximate) SU(2)L⊗SU(2)R chiral symmetry. A revised version of the so-called “optimal approximation” is applied, where one-nucleon interaction amplitude is factorized out and the medium-modifications and pion wave function distortion are included. The calculation is tested against the coherent pion photoproduction data.Results: The computation shows an agreement with the pion photoproduction data, although precisely determining the Δ modification is entangled with one mentioned contact term. The uncertainty in the Δ modification leads to uncertainties in both pion and photon neutrinoproductions. In addition, the contact term plays a significant role in NC photon production.Conclusions: First, the contact term increases NC photon production by ˜10% assuming a reasonable range of the contact coupling, which however seems not significant enough to explain the Mini
Czech Academy of Sciences Publication Activity Database
Baruník, Jozef; Vácha, Lukáš; Krištoufek, Ladislav
2011-01-01
Roč. 2011, č. 22 (2011), s. 1-22 R&D Projects: GA ČR GD402/09/H045; GA ČR GA402/09/0965 Grant ostatní: GAUK(CZ) 118310 Institutional research plan: CEZ:AV0Z10750506 Keywords : comovement * stock market * wavelet analysis * wavelet coherence Subject RIV: AH - Economics http://library.utia.cas.cz/separaty/2011/E/barunik-0367060.pdf
Theory of charge transport in molecular junctions: From Coulomb blockade to coherent tunneling
Energy Technology Data Exchange (ETDEWEB)
Chang, Yao-Wen; Jin, Bih-Yaw, E-mail: byjin@ntu.edu.tw [Department of Chemistry and Center for Emerging Material and Advanced Devices and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)
2014-08-14
We study charge transport through molecular junctions in the presence of electron-electron interaction using the nonequilibrium Green's function techniques and the renormalized perturbation theory. In the perturbation treatment, the zeroth-order Hamiltonian of the molecular junction is composed of independent single-impurity Anderson's models, which act as the channels where charges come through or occupy, and the interactions between different channels are treated as the perturbation. Using this scheme, the effects of molecule-lead, electron-electron, and hopping interactions are included nonperturbatively, and the charge transport processes can thus be studied in the intermediate parameter range from the Coulomb blockade to the coherent tunneling regimes. The concept of quasi-particles is introduced to describe the kinetic process of charge transport, and then the electric current can be studied and calculated. As a test study, the Hubbard model is used as the molecular Hamiltonian to simulate dimeric and trimeric molecular junctions. Various nonlinear current-voltage characteristics, including Coulomb blockade, negative differential resistance, rectification, and current hysteresis, are shown in the calculations, and the mechanisms are elucidated.
Theory of charge transport in molecular junctions: From Coulomb blockade to coherent tunneling
International Nuclear Information System (INIS)
We study charge transport through molecular junctions in the presence of electron-electron interaction using the nonequilibrium Green's function techniques and the renormalized perturbation theory. In the perturbation treatment, the zeroth-order Hamiltonian of the molecular junction is composed of independent single-impurity Anderson's models, which act as the channels where charges come through or occupy, and the interactions between different channels are treated as the perturbation. Using this scheme, the effects of molecule-lead, electron-electron, and hopping interactions are included nonperturbatively, and the charge transport processes can thus be studied in the intermediate parameter range from the Coulomb blockade to the coherent tunneling regimes. The concept of quasi-particles is introduced to describe the kinetic process of charge transport, and then the electric current can be studied and calculated. As a test study, the Hubbard model is used as the molecular Hamiltonian to simulate dimeric and trimeric molecular junctions. Various nonlinear current-voltage characteristics, including Coulomb blockade, negative differential resistance, rectification, and current hysteresis, are shown in the calculations, and the mechanisms are elucidated
Yan, Jiawei; Ke, Youqi
2016-07-01
Electron transport properties of nanoelectronics can be significantly influenced by the inevitable and randomly distributed impurities/defects. For theoretical simulation of disordered nanoscale electronics, one is interested in both the configurationally averaged transport property and its statistical fluctuation that tells device-to-device variability induced by disorder. However, due to the lack of an effective method to do disorder averaging under the nonequilibrium condition, the important effects of disorders on electron transport remain largely unexplored or poorly understood. In this work, we report a general formalism of Green's function based nonequilibrium effective medium theory to calculate the disordered nanoelectronics. In this method, based on a generalized coherent potential approximation for the Keldysh nonequilibrium Green's function, we developed a generalized nonequilibrium vertex correction method to calculate the average of a two-Keldysh-Green's-function correlator. We obtain nine nonequilibrium vertex correction terms, as a complete family, to express the average of any two-Green's-function correlator and find they can be solved by a set of linear equations. As an important result, the averaged nonequilibrium density matrix, averaged current, disorder-induced current fluctuation, and averaged shot noise, which involve different two-Green's-function correlators, can all be derived and computed in an effective and unified way. To test the general applicability of this method, we applied it to compute the transmission coefficient and its fluctuation with a square-lattice tight-binding model and compared with the exact results and other previously proposed approximations. Our results show very good agreement with the exact results for a wide range of disorder concentrations and energies. In addition, to incorporate with density functional theory to realize first-principles quantum transport simulation, we have also derived a general form of
Limiting Central Bank Credit to the Government; Theory and Practice
Carlo Cottarelli
1993-01-01
This paper examines central bank independence with reference to the constraints on central bank credit to the government, focusing on how such credit should be regulated. It discusses why credit should be contsrained, and in which forms, and how to implement those constraints.
Czech Academy of Sciences Publication Activity Database
Baruník, Jozef; Vácha, Lukáš; Krištoufek, Ladislav
Vol. Part II. České Budějovice: University of South Bohemia in České Budějovice, Faculty of Economy, 2010 - (Houda, M.; Friebelová, J.), s. 12-17 ISBN 978-80-7394-218-2. [Mathematical Methods in Economics 2010. České Budějovice (CZ), 08.09.2010-10.09.2010] R&D Projects: GA ČR GA402/09/0965; GA ČR GD402/09/H045; GA ČR GP402/08/P207 Institutional research plan: CEZ:AV0Z10750506 Keywords : comovement * contagion * wavelet analysis * wavelet coherence Subject RIV: AH - Economics http://library.utia.cas.cz/separaty/2010/E/barunik-0347765.pdf
Theory of two-atom coherence in gases. II. Continuous-wave spectra
Ben-Reuven, Abraham
1980-12-01
General expressions are derived for the spectral line shapes of resonance absorption and scattering of coherent radiation in collision-broadened gases, taking into account effects of coherent excitation of two or more atoms (or molecules), as steady-state solutions of a hierarchy of master equations described in a previous publication (paper I). Coupling between the coherent motions of the atoms, provided by a Bethe-Salpeter-type effective interaction, in the binary-collision approximation, forms the essential mechanism for introducing cooperative coherent effects into the steady-state spectra. Explicit expressions are given for the effects of two-atom coherence in the binary-collision approximation, in which the Bloch-type dressed-atom self-energy superoperator is modified by the presence of collisions in which both atoms retain memory of their coherent propagation before the collision. The self-energies include the effects of resonance exchange symmetrization in self-broadening, and are renormalized by the coincidence of radiative transitions during the collisions. The impact (near-resonance) and the quasistatic (line-wing) limits of the applied-frequency detunings are discussed. In the quasistatic limit, coherent many-atom excitations become irrelevant; however, interactions of both collision partners with the radiation during the collision accounts for such phenomena as collision-induced absorption or radiative collisions. In the impact limit, the inclusion of the Bethe-Salpeter interactions allows for the appearance of two-atom resonances. Magnitude estimates of these effects are discussed. Effects of higher-rank (many-body) coherences are formally discussed with the help of a diagrammatic method, leading into implicit bootstrap equations that can be solved by iterative or other procedures.
Directory of Open Access Journals (Sweden)
Anthony Pak Hin Kong
2014-04-01
Our results seemed to suggest that speakers with anomic aphasia had reduced proportion of essential information content, lower degree of elaboration, simplified discourse structure, and more structural disruptions than their healthy counterparts. We argue that the above characteristics have contributed to the reduced overall coherence in their oral discourse. The use of RST to quantify discourse coherence provided more objective measurement on macro-linguistic characteristics in aphasia and, therefore, warrants further investigation.
Hassan, Bilal; Raja, Gulistan; Hassan, Taimur; Usman Akram, M
2016-04-01
Macular edema (ME) and central serous retinopathy (CSR) are two macular diseases that affect the central vision of a person if they are left untreated. Optical coherence tomography (OCT) imaging is the latest eye examination technique that shows a cross-sectional region of the retinal layers and that can be used to detect many retinal disorders in an early stage. Many researchers have done clinical studies on ME and CSR and reported significant findings in macular OCT scans. However, this paper proposes an automated method for the classification of ME and CSR from OCT images using a support vector machine (SVM) classifier. Five distinct features (three based on the thickness profiles of the sub-retinal layers and two based on cyst fluids within the sub-retinal layers) are extracted from 30 labeled images (10 ME, 10 CSR, and 10 healthy), and SVM is trained on these. We applied our proposed algorithm on 90 time-domain OCT (TD-OCT) images (30 ME, 30 CSR, 30 healthy) of 73 patients. Our algorithm correctly classified 88 out of 90 subjects with accuracy, sensitivity, and specificity of 97.77%, 100%, and 93.33%, respectively. PMID:27140751
On the Curvature of the Central Path of Linear Programming Theory
Dedieu, Jean-Pierre; Malajovich, Gregorio; Shub, Mike
2003-01-01
We prove a linear bound on the average total curvature of the central path of linear programming theory in terms on the number of independent variables of the primal problem, and independent on the number of constraints.
Stability of Spatial Structure of Urban Agglomeration in China Based on Central Place Theory
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
This paper brings forward the concept of stability of the spatial structure of urban agglomeration (UA) based on Central Place Theory by introducing centrality index and fractal theory. Before assessment, K=4 is selected as parameter to calculate centrality index and fractal dimension (K represents the quantitive relationship between city and the counties in Central Place Theory), and then found the number of nodes, the type of spatial structure, the spatial allocation of nodes with different hierarchy affecting the stability of spatial structure. According to spatial contact direction and the level of stability, UAs in China are classified into five types. Finally, it is posed as a further question that how to use hierarchical relation K=6 and K=7 in central place system to coordinate with the assessment of stability of spatial structure is brought forward.
International Nuclear Information System (INIS)
Based on a hybrid mapping, the vector coherent state theory is revisited. The hybrid mapping of a fermion state with N coherent (collective) fermion pairs and u unpaired (noncollective) fermions leads to a hybrid state with N bosons and u fermions. The hybrid mapping is exact by which the formidable problem of finding the matrix elements of a fermion operator for a (2N+u)-fermion system is reduced to that for a u-fermion system. The Pauli effects are totally taken into account by the overlap matrix (the K matrix) for the fermion states. The application to a fermion system with the Sp(6)contains U(3) dynamical symmetry is discussed where it is vividly seen that the occurrence of the dynamical Pauli factors is related to the fermion pair↔boson transformation. The intricate properties of the intrinsic operators and the K operator are discussed in detail
Jaime, Mark; McMahon, Camilla M.; Davidson, Bridget C.; Newell, Lisa C.; Mundy, Peter C.; Henderson, Heather A.
2016-01-01
Although prior studies have demonstrated reduced resting state EEG coherence in adults with autism spectrum disorder (ASD), no studies have explored the nature of EEG coherence during joint attention. We examined the EEG coherence of the joint attention network in adolescents with and without ASD during congruent and incongruent joint attention…
Coherence properties of third and fourth generation X-ray sources. Theory and experiment
Energy Technology Data Exchange (ETDEWEB)
Singer, Andrej
2013-06-15
Interference effects are among the most fascinating optical phenomena. For instance, the butterflies and soap bubbles owe their beautiful colors to interference effects. They appear as a result of the superposition principle, valid in electrodynamics due to the linearity of the wave equation. If two waves interfere, the total radiation field is a sum of these two fields and depends strongly on the relative phases between these fields. While the oscillation frequency of individual fields is typically too large to be observed by a human eye or other detection systems, the phase differences between these fields manifest themselves as relatively slowly varying field strength modulations. These modulations can be detected, provided the oscillating frequencies of the superposed fields are similar. As such, the interference provides a superb measure of the phase differences of optical light, which may carry detailed information about a source or a scattering object. The ability of waves to interfere depends strongly on the degree of correlation between these waves, i.e. their mutual coherence. Until the middle of the 20th century, the coherence of light available to experimentalists was poor. A significant effort had to be made to extend the degree of coherence, which made the electromagnetic field determination using of the interference principle very challenging. Coherence is the defining feature of a laser, whose invention initiated a revolutionary development of experimental techniques based on interference, such as holography. Important contributions to this development were also provided by astronomists, as due to enormous intergalactic distances the radiation from stars has a high transverse coherence length at earth. With the construction of third generation synchrotron sources, partially coherent X-ray sources have become feasible. New areas of research utilizing highly coherent X-ray beams have emerged, including X-ray photon correlation spectroscopy (XPCS), X
Coherence properties of third and fourth generation X-ray sources. Theory and experiment
International Nuclear Information System (INIS)
Interference effects are among the most fascinating optical phenomena. For instance, the butterflies and soap bubbles owe their beautiful colors to interference effects. They appear as a result of the superposition principle, valid in electrodynamics due to the linearity of the wave equation. If two waves interfere, the total radiation field is a sum of these two fields and depends strongly on the relative phases between these fields. While the oscillation frequency of individual fields is typically too large to be observed by a human eye or other detection systems, the phase differences between these fields manifest themselves as relatively slowly varying field strength modulations. These modulations can be detected, provided the oscillating frequencies of the superposed fields are similar. As such, the interference provides a superb measure of the phase differences of optical light, which may carry detailed information about a source or a scattering object. The ability of waves to interfere depends strongly on the degree of correlation between these waves, i.e. their mutual coherence. Until the middle of the 20th century, the coherence of light available to experimentalists was poor. A significant effort had to be made to extend the degree of coherence, which made the electromagnetic field determination using of the interference principle very challenging. Coherence is the defining feature of a laser, whose invention initiated a revolutionary development of experimental techniques based on interference, such as holography. Important contributions to this development were also provided by astronomists, as due to enormous intergalactic distances the radiation from stars has a high transverse coherence length at earth. With the construction of third generation synchrotron sources, partially coherent X-ray sources have become feasible. New areas of research utilizing highly coherent X-ray beams have emerged, including X-ray photon correlation spectroscopy (XPCS), X
The solar cycle - A central-source wave theory
Bracewell, R. N.
1989-01-01
Studies stimulated by the interpretation of the Elatina formation in South Australia as a fossil record of solar activity have led to discoveries of previously unnoticed features of the sunspot cycle record and to a theory of origin of the sunspot cycle that postulates a solar core in torsional motion and a magnetomechanical wave that couples to the photosphere. The considerations supporting the solar interpretation of the Elatina formation are gathered together.
Tierz, Miguel
2016-01-01
We give explicit analytical expressions for the partition function of $% U(N)_{k}\\times U(N+M)_{-k}$ ABJ theory at weak coupling ($k\\rightarrow \\infty )$ for finite and arbitrary values of $N$ and $M$ (including the ABJM case and its mass-deformed generalization). We obtain the expressions by identifying the one-matrix model formulation with a Meixner-Pollaczek ensemble and using the corresponding orthogonal polynomials, which are also eigenfunctions of a $su(1,1)$ quantum oscillator. Wilson loops in mass-deformed ABJM are also studied in the same limit and interpreted in terms of $su(1,1)$ coherent states.
The coherent scattering function of the reptation model: simulations compared to theory
Baumgärtner, A.; Ebert, U.; Schäfer, L.
2003-01-01
We present results of Monte Carlo simulations measuring the coherent structure function of a chain moving through an ordered lattice of fixed topological obstacles. Our computer experiments use chains up to 320 beads and cover a large range of wave vectors and a time range exceeding the reptation ti
International Nuclear Information System (INIS)
Using the model of a generalized Van der Pol oscillator in the regime of subcritical Hopf bifurcation, we investigate the influence of time delay on noise-induced oscillations. It is shown that for appropriate choices of time delay, either suppression or enhancement of coherence resonance can be achieved. Analytical calculations are combined with numerical simulations and experiments on an electronic circuit
Energy Technology Data Exchange (ETDEWEB)
Manjaly, Z.M.
2007-10-15
The contribution covers the following chapters: 1. In search of the hidden: an FMRI study with implications for the study of patients with autism and with acquired brain injury. 2. Context-dependent interactions of left posterior inferior frontal gyrus in a local visual search task unrelated to language. 3. Neurophysiological correlates of relatively enhanced local visual search in autistic adolescents.
International Nuclear Information System (INIS)
The contribution covers the following chapters: 1. In search of the hidden: an FMRI study with implications for the study of patients with autism and with acquired brain injury. 2. Context-dependent interactions of left posterior inferior frontal gyrus in a local visual search task unrelated to language. 3. Neurophysiological correlates of relatively enhanced local visual search in autistic adolescents
Allegra, Michele; Giorda, Paolo; Lloyd, Seth
2016-04-01
Assessing the role of interference in natural and artificial quantum dynamical processes is a crucial task in quantum information theory. To this aim, an appropriate formalism is provided by the decoherent histories framework. While this approach has been deeply explored from different theoretical perspectives, it still lacks of a comprehensive set of tools able to concisely quantify the amount of coherence developed by a given dynamics. In this paper, we introduce and test different measures of the (average) coherence present in dissipative (Markovian) quantum evolutions, at various time scales and for different levels of environmentally induced decoherence. In order to show the effectiveness of the introduced tools, we apply them to a paradigmatic quantum process where the role of coherence is being hotly debated: exciton transport in photosynthetic complexes. To spot out the essential features that may determine the performance of the transport, we focus on a relevant trimeric subunit of the Fenna-Matthews-Olson complex and we use a simplified (Haken-Strobl) model for the system-bath interaction. Our analysis illustrates how the high efficiency of environmentally assisted transport can be traced back to a quantum recoil avoiding effect on the exciton dynamics, that preserves and sustains the benefits of the initial fast quantum delocalization of the exciton over the network. Indeed, for intermediate levels of decoherence, the bath is seen to selectively kill the negative interference between different exciton pathways, while retaining the initial positive one. The concepts and tools here developed show how the decoherent histories approach can be used to quantify the relation between coherence and efficiency in quantum dynamical processes.
Directory of Open Access Journals (Sweden)
Emre Hekimoglu
2015-01-01
Full Text Available Purpose. To evaluate the repeatability of measurement of central corneal thickness (CCT by spectral domain optical coherence (SD-OCT in premature infants and compare it to CCT measurement by ultrasonic pachymetry (USP. Methods. Three CCT measurements of the left eyes of 50 premature infants were obtained by SD-OCT using the iVue system. 10 CCT measurements of each 28 left eyes of 28 infants were obtained by USP using the Pacscan 300P system. Bland-Altman plots were developed and the limit of agreement (LoA was determined to compare the mean of the SD-OCT and USP measurements. Results. No statistically significant difference was found among the 3 CCT measurements by SD-OCT. Both USP and SD-OCT have been performed for only left eyes of 28 of the 50 babies. Those results have been compared with each other. A statistically significant difference was found between the mean CCT measurements by SD-OCT and USP (p<0.05. The LoA between the SD-OCT and USP measurements ranged from 11.4 to −64.1. Conclusions. CCT can be measured using the iVue SD-OCT system with a high level of repeatability. Although measurement of CCT by SD-OCT and USP is highly correlated, the 2 systems cannot be used interchangeably in premature infants.
Theory of spontaneous radiation by electrons in a trajectory-coherent approximation
International Nuclear Information System (INIS)
The first-order quantum correction for the characterization of spontaneous radiation is calculated by means of electron quasi-classical trajectory-coherent states in an arbitrary electromagnetic field. Well known expressions for the characterization of spontaneous radiation are obtained using quasi-classical approximation. The first-order quantum correction is derived as a function from a classical trajectory (among which is a classical spin vector). Transitions with spin flip and without spin flip are distinguished. Those elements connected with photon kick and quantum motion characteristics are selected for first-order quantum correction. It is shown that, using an ultra-relativistic approximation, the latter may be ignored, but when using a non-relativistic approximation their contributions are approximately equal. A special trajectory-coherent representation that significantly simplifies the investigation of spontaneous radiation is proposed. (author)
Dynamical diffraction theory for the parametric X-rays and coherent bremsstrahlung
Feranchuk, Ilya D.; Lugovskaya, O.; Ulyanenkov, A.
2005-01-01
The various mechanisms of X-ray radiation from relativistically charged particles in a crystal are analyzed from a common point of view, based on quantum electrodynamics in a medium. Parametric X-rays (PXR), diffraction radiation (DR) and coherent bremsstrahlung (CB) lead to different contributions to the amplitude of the radiation process but because of their interference they cannot be considered separately in the radiation intensity. The role of the dynamical diffraction effect...
EEG slow-wave coherence changes in propofol-induced general anesthesia: Experiment and theory
Directory of Open Access Journals (Sweden)
Kaier eWang
2014-10-01
Full Text Available The electroencephalogram (EEG patterns recorded during general anesthetic-induced coma are closely similar to those seen during slow-wave sleep, the deepest stage of natural sleep; both states show patterns dominated by large amplitude slow waves. Slow oscillations are believed to be important for memory consolidation during natural sleep. Tracking the emergence of slow-wave oscillations during transition to unconsciousness may help us to identify drug-induced alterations of the underlying brain state, and provide insight into the mechanisms of general anesthesia. Although cellular-based mechanisms have been proposed, the origin of the slow oscillation has not yet been unambiguously established. A recent theoretical study by Steyn-Ross et al. [Physical Review X 3(2, 021005 (2013] proposes that the slow oscillation is a network, rather than cellular phenomenon. Modeling anesthesia as a moderate reduction in gap-junction interneuronal coupling, they predict an unconscious state signposted by emergent low-frequency oscillations with chaotic dynamics in space and time. They suggest that anesthetic slow-waves arise from a competitive interaction between symmetry-breaking instabilities in space (Turing and time (Hopf, modulated by gap-junction coupling strength. A significant prediction of their model is that EEG phase coherence will decrease as the cortex transits from Turing--Hopf balance (wake to Hopf-dominated chaotic slow-waves (unconsciousness. Here, we investigate changes in phase coherence during induction of general anesthesia. After examining 128-channel EEG traces recorded from five volunteers undergoing propofol anesthesia, we report a significant drop in sub-delta band (0.05--1.5 Hz slow-wave coherence between frontal, occipital, and frontal-occipital electrode pairs, with the most pronounced wake-versus-unconscious coherence changes occurring at the frontal cortex.
EEG slow-wave coherence changes in propofol-induced general anesthesia: experiment and theory.
Wang, Kaier; Steyn-Ross, Moira L; Steyn-Ross, D A; Wilson, Marcus T; Sleigh, Jamie W
2014-01-01
The electroencephalogram (EEG) patterns recorded during general anesthetic-induced coma are closely similar to those seen during slow-wave sleep, the deepest stage of natural sleep; both states show patterns dominated by large amplitude slow waves. Slow oscillations are believed to be important for memory consolidation during natural sleep. Tracking the emergence of slow-wave oscillations during transition to unconsciousness may help us to identify drug-induced alterations of the underlying brain state, and provide insight into the mechanisms of general anesthesia. Although cellular-based mechanisms have been proposed, the origin of the slow oscillation has not yet been unambiguously established. A recent theoretical study by Steyn-Ross et al. (2013) proposes that the slow oscillation is a network, rather than cellular phenomenon. Modeling anesthesia as a moderate reduction in gap-junction interneuronal coupling, they predict an unconscious state signposted by emergent low-frequency oscillations with chaotic dynamics in space and time. They suggest that anesthetic slow-waves arise from a competitive interaction between symmetry-breaking instabilities in space (Turing) and time (Hopf), modulated by gap-junction coupling strength. A significant prediction of their model is that EEG phase coherence will decrease as the cortex transits from Turing-Hopf balance (wake) to Hopf-dominated chaotic slow-waves (unconsciousness). Here, we investigate changes in phase coherence during induction of general anesthesia. After examining 128-channel EEG traces recorded from five volunteers undergoing propofol anesthesia, we report a significant drop in sub-delta band (0.05-1.5 Hz) slow-wave coherence between frontal, occipital, and frontal-occipital electrode pairs, with the most pronounced wake-vs.-unconscious coherence changes occurring at the frontal cortex. PMID:25400558
DEFF Research Database (Denmark)
Happel, Christoph M.; Thommes, Jan; Thrane, Lars;
2011-01-01
We introduce a new method of rotational image acquisition for four-dimensional (4D) optical coherence tomography (OCT) of beating embryonic chick hearts. The rotational axis and the central A-scan of the OCT are identical. An out-of-phase image sequence covering multiple heartbeats is acquired at.......We demonstrate this approach and provide a video of a beating Hamburger and Hamilton stage 16 embryonic chick heart generated from a 4D OCT data set using rotational image acquisition....
Theory of coherent molecule to surface electron injection: An analytical model
Indian Academy of Sciences (India)
S Ramakrishna; T Seideman; F Willig; V May
2009-09-01
Electron transfer from a molecular level to empty continuum levels of a substrate is described theoretically. Using a quasicontinuum approach to model the substrate, analytical expressions pertaining to the time-dependent probability among the various levels of the substrate is presented along with its extension to coherently excited molecular vibrational modes. Hidden time scales and dynamics are revealed in the analysis and possible experiments to observe the new results are suggested. We note the applicability of the model to the description of a variety of other phenomena that are formally similar to the electron injection problem, although pertaining to different physics.
Stupakov, Gennady; Zhou, Demin
2016-04-01
We develop a general model of coherent synchrotron radiation (CSR) impedance with shielding provided by two parallel conducting plates. This model allows us to easily reproduce all previously known analytical CSR wakes and to expand the analysis to situations not explored before. It reduces calculations of the impedance to taking integrals along the trajectory of the beam. New analytical results are derived for the radiation impedance with shielding for the following orbits: a kink, a bending magnet, a wiggler of finite length, and an infinitely long wiggler. All our formulas are benchmarked against numerical simulations with the CSRZ computer code.
To the theory of coherent generation of resonance-tunnel diode
International Nuclear Information System (INIS)
The strict quantum-mechanical description of coherent generation of a resonance-tunnel diode is given for the simple model of the two-barrier structure. The exact analytical solutions of the Schroedinger equation for electrons in the presence of a weak electromagnetic field are found. Active and reactive polarization currents are calculated un the wide frequency range. These expressions satisfy Kramers-Kronig correlations. The analysis of threshold conditions of the generation is carried out. It is shown that the generation is possible at superhigh frequency above the inverse lifetime of electrons in a quantum well
Stupakov, Gennady
2016-01-01
We develop a general model of coherent synchrotron radiation (CSR) impedance with shielding provided by two parallel conducting plates. This model allows us to easily reproduce all previously known analytical CSR wakes and to expand the analysis to the situations not explored before. It reduces calculations of the impedance to taking integrals along the trajectory of the beam. New analytical results are derived for the radiation impedance with shielding for the following orbits: a kink, a bending magnet, a wiggler of finite length, and an infinitely long wiggler. All our formulas are benchmarked agains numerical simulations with the CSRZ computer code.
How research on marketing in Central and Eastern Europe can advance international marketing theory
Arnold Schuh
2010-01-01
This paper deals with the question of how research on marketing issues in Central and Eastern Europe (CEE) can contribute to the international marketing theory. Regional studies provide valuable insights into business environments, marketing systems and practices in specific countries and geographical areas, which explain their high appeal among marketing practitioners. While contributing to the general body of knowledge in marketing, they often lack a strong role in theory development. Two a...
Yan, Jiawei; Ke, Youqi
In realistic nanoelectronics, disordered impurities/defects are inevitable and play important roles in electron transport. However, due to the lack of effective quantum transport method, the important effects of disorders remain poorly understood. Here, we report a generalized non-equilibrium vertex correction (NVC) method with coherent potential approximation to treat the disorder effects in quantum transport simulation. With this generalized NVC method, any averaged product of two single-particle Green's functions can be obtained by solving a set of simple linear equations. As a result, the averaged non-equilibrium density matrix and various important transport properties, including averaged current, disordered induced current fluctuation and the averaged shot noise, can all be efficiently computed in a unified scheme. Moreover, a generalized form of conditionally averaged non-equilibrium Green's function is derived to incorporate with density functional theory to enable first-principles simulation. We prove the non-equilibrium coherent potential equals the non-equilibrium vertex correction. Our approach provides a unified, efficient and self-consistent method for simulating non-equilibrium quantum transport through disorder nanoelectronics. Shanghaitech start-up fund.
Theory of nonlinear phononics for coherent light-control of solids
Subedi, Alaska; Cavalleri, Andrea; Georges, Antoine
2013-01-01
We present a microscopic theory for ultrafast control of solids with high-intensity terahertz frequency optical pulses. When resonant with selected infrared-active vibrations, these pulses transiently modify the crystal structure and lead to new collective electronic properties. The theory predicts the dynamical path taken by the crystal lattice using first-principles calculations of the energy surface and classical equations of motion, as well as symmetry considerations. Two classes of dynam...
Theory of coherent transition radiation generated at a plasma-vacuum interface
Energy Technology Data Exchange (ETDEWEB)
Schroeder, Carl B.; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim P.
2003-06-26
Transition radiation generated by an electron beam, produced by a laser wakefield accelerator operating in the self-modulated regime, crossing the plasma-vacuum boundary is considered. The angular distributions and spectra are calculated for both the incoherent and coherent radiation. The effects of the longitudinal and transverse momentum distributions on the differential energy spectra are examined. Diffraction radiation from the finite transverse extent of the plasma is considered and shown to strongly modify the spectra and energy radiated for long wavelength radiation. This method of transition radiation generation has the capability of producing high peak power THz radiation, of order 100 (mu)J/pulse at the plasma-vacuum interface, which is several orders of magnitude beyond current state-of-the-art THz sources.
Theory of coherent transition radiation generated at a plasma-vacuum interface
International Nuclear Information System (INIS)
Transition radiation generated by an electron beam, produced by a laser wakefield accelerator operating in the self-modulated regime, crossing the plasma-vacuum boundary is considered. The angular distributions and spectra are calculated for both the incoherent and coherent radiation. The effects of the longitudinal and transverse momentum distributions on the differential energy spectra are examined. Diffraction radiation from the finite transverse extent of the plasma is considered and shown to strongly modify the spectra and energy radiated for long wavelength radiation. This method of transition radiation generation has the capability of producing high peak power THz radiation, of order 100 (mu)J/pulse at the plasma-vacuum interface, which is several orders of magnitude beyond current state-of-the-art THz sources
Amador, Filomena; Martinho, Ana Paula; Bacelar-Nicolau, Paula; Caeiro, Sandra; Oliveira, Carla Padrel
2015-01-01
Universities are an important part of the process of change taking place in society. However, this is often overshadowed by these institutions giving priority to technocratic models in the relationship between science and society. In this context, according to Habermas, theories can serve to clarify practical questions and guide praxis into the…
Fluid models for kinetic effects on coherent nonlinear Alfvacute en waves. I. Fundamental theory
International Nuclear Information System (INIS)
Collisionless regime kinetic models for coherent nonlinear Alfvacute en wave dynamics are studied using fluid moment equations with an approximate closure anzatz. Resonant particle effects are modeled by incorporating an additional term representing dissipation akin to parallel heat conduction. Unlike collisional dissipation, parallel heat conduction is presented by an integral operator. The modified derivative nonlinear Schroedinger equation thus has a spatially nonlocal nonlinear term describing the long-time evolution of the envelope of parallel-propagating Alfvacute en waves, as well. Coefficients in the nonlinear terms are free of the (1-β)-1 singularity usually encountered in previous analyses, and have a very simple form that clarifies the physical processes governing the large-amplitude Alfvacute enic nonlinear dynamics. The nonlinearity appears via coupling of an Alfvacute enic mode to a kinetic ion-acoustic mode. Damping of the nonlinear Alfvacute en wave appears via strong Landau damping of the ion-acoustic wave when the electron-to-ion temperature ratio is close to unity. For a (slightly) obliquely propagating wave, there are finite Larmor radius corrections in the dynamical equation. This effect depends on the angle of wave propagation relative to B0 and vanishes for the limit of strictly parallel propagation. Explicit magnetic perturbation envelope equations amenable to further analysis and numerical solution are obtained. Implications of these models for collisionless shock dynamics are discussed. copyright 1996 American Institute of Physics
International Nuclear Information System (INIS)
We develop a first principles theoretical description of femtosecond double-pump single-molecule signals of molecular aggregates. We incorporate all singly excited electronic states and vibrational modes with significant exciton-phonon coupling into a system Hamiltonian and treat the ensuing system dynamics within the Davydov D1 Ansatz. The remaining intra- and inter-molecular vibrational modes are treated as a heat bath and their effect is accounted for through lineshape functions. We apply our theory to simulate single-molecule signals of the light harvesting complex II. The calculated signals exhibit pronounced oscillations of mixed electron-vibrational (vibronic) origin. Their periods decrease with decreasing exciton-phonon coupling
Space-time dependent couplings In N = 1 SUSY gauge theories: Anomalies and central functions
International Nuclear Information System (INIS)
We consider N = 1 supersymmetric gauge theories in which the couplings are allowed to be space-time dependent functions. Both the gauge and the superpotential couplings become chiral superfields. As has recently been shown, a new topological anomaly appears in models with space-time dependent gauge coupling. Here we show how this anomaly may be used to derive the NSVZ β-function in a particular, well-determined renormalisation scheme, both without and with chiral matter. Moreover we extend the topological anomaly analysis to theories coupled to a classical curved superspace background, and use it to derive an all-order expression for the central charge c, the coefficient of the Weyl tensor squared contribution to the conformal anomaly. We also comment on the implications of our results for the central charge a expected to be of relevance for a four-dimensional C-theorem. (author)
Energy Technology Data Exchange (ETDEWEB)
Chen, Lipeng; Zhao, Yang, E-mail: YZhao@ntu.edu.sg [Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Gelin, Maxim F.; Domcke, Wolfgang [Department of Chemistry, Technische Universität München, Garching D-85747 (Germany)
2015-04-28
We develop a first principles theoretical description of femtosecond double-pump single-molecule signals of molecular aggregates. We incorporate all singly excited electronic states and vibrational modes with significant exciton-phonon coupling into a system Hamiltonian and treat the ensuing system dynamics within the Davydov D{sub 1} Ansatz. The remaining intra- and inter-molecular vibrational modes are treated as a heat bath and their effect is accounted for through lineshape functions. We apply our theory to simulate single-molecule signals of the light harvesting complex II. The calculated signals exhibit pronounced oscillations of mixed electron-vibrational (vibronic) origin. Their periods decrease with decreasing exciton-phonon coupling.
DEFF Research Database (Denmark)
Happel, C. M.; Thommes, J.; Thrane, Lars;
2011-01-01
We introduce a new method of rotational image acquisition for four dimensional (4D) optical coherence tomography (OCT) of beating embryonic chick hearts. The rotational axis and the central A-scan of the OCT are identical. An out-of-phase image sequence covering multiple heartbeats is acquired at...... every angle of an incremental rotation of the deflection mirrors of the OCT system. Image acquisition is accomplished after a rotation of 180. Comparison of a displayed live M-mode of the central A-scan with a reference M-mode allows instant detection of translational movements of the embryo. For....... We demonstrate this approach and provide a video of a beating HH stage 16 embryonic chick heart generated from a 4D OCT data set using rotational image acquisition. The result is validated by comparison of calculated and orignal B-scan sequences (see Figure)....
Aspects of the theory of atoms and coherent matter and their interaction with electromagnetic fields
Energy Technology Data Exchange (ETDEWEB)
Nilsen, Halvor Moell
2002-07-01
In the present work I have outlined and contributed to the time-dependent theory of the interaction between atoms and electromagnetic fields and the theory of Bose-Einstein condensates. New numerical methods and algorithms have been developed and applied in practice. Calculations have exhibited certain new dynamical features. All these calculations are in a regime where the applied field is of the same magnitude as the atomic field. In the case of BEC we have investigated the use of time-dependent methods to calculate the excitation frequencies. We also investigated the possibility of nonlinear coupling for a scissors mode and found no such contributions to damping which is consistent with other studies . Special emphasis has also been paid to the gyroscopic motion of rotating BEC where several models were investigated. Briefly, the main conclusions are: (1) Rydberg wave packets appear for direct excitations of Rydberg atoms for long pulses. (2) The survival of just a few states is decided by symmetry of the Hamiltonian. (3) For few cycle intense pulses classical and quantum mechanics show remarkable similarity. (4) Time-dependent methods for finding excitation frequencies have been shown to be very efficient. (5) New dynamical features is shown in gyroscopic motion of BEC. (6) It was shown that no nonlinear mixing of scissors modes occur in the standard Gross-Pitaevskii regime. As mentioned in the introduction, this work is a part of very active research fields and new progress is constantly reported. Thus, the present work cannot be concluded as a closed loop. The fast development of grid based numerical solutions for atoms in intense fields will surely make great contribution to solve many of today's problems. It is a very important area of research to understand both nonperturbative atomic response and highly nonlinear optics. In the field of Bose-Einstein condensation the new experimental achievements constantly drive the field forward. The new
Eidi, Mohammadreza; Niknam, Ali Reza; Morshedian, Nader
2015-01-01
We report a new version of fermion coupled coherent states (FCCS-II) method to simulate two-electron systems based on a self-symmetrized six-dimensional (6D) coherent states grid. Unlike the older fermion coupled coherent states (FCCS-I) method, FCCS-II does not need any new equations in comparison with the coupled coherent states method. FCCS-II uses a simpler and more efficient approach for symmetrizing the spatial wave function in the simulation of fermionic systems. This method, has significantly increased the speed of computations and give us capability to simulate the quantum systems with the larger CS grids. We apply FCCS-II to simulate the Helium atom and the Hydrogen molecule based on grids with a large numbers of coherent states. Moreover, we have derived all the important equations of the FCCS-I by an exact attitude.
Reščič, J; Kalyuzhnyi, Y V; Cummings, P T
2016-10-19
The approach developed earlier to describe the dimerizing shielded attractive shell (SAS) primitive model of chemical association due to Cummings and Stell is generalized and extended to include a description of a polymerizing SAS model. Our extension is based on the combination of the resummed thermodynamic perturbation theory for central force (RTPT-CF) associating potential and self consistent scheme, which takes into account the changes in the system free volume due to association. Theoretical results for thermodynamical properties of the model at different bonding length, density and temperature are compared against newly generated computer simulation results. The theory gives very accurate predictions for the model with bonding length L (*) from the range 0 < L (*) < 0.6 at all values of the density and temperature studied, including the limit of infinitely large temperature. PMID:27545613
Yukalov, V. I.; E. P. Yukalova
2004-01-01
The main part of this review is devoted to the comprehensive description of coherent radiation by nuclear spins. The theory of nuclear spin superradiance is developed and the experimental observations of this phenomenon are considered. The intriguing problem of how coherence develops from initially incoherent quantum fluctuations is analysed. All main types of coherent radiation by nuclear spins are discussed, which are: free nuclear induction, collective induction, maser generation, pure sup...
Institute of Scientific and Technical Information of China (English)
Yuchuan BAI; Andreas MALCHEREK; Changbo JIANG
2001-01-01
The formation of sand wave is such a process in which the roughness and discontinuity of the original bed surface cause the disturbance of the bottom laminar flow in an open channel,and the development of the disturbance in turn leads to instability of the flow and the appearance of the coherent structure. The evolution and development of the coherent structure further promote the undulations of bed surface and sand waves rise finally. The sand wave is explained as a result of action that the bed sediment particles are disturbed by the coherent structure. This study shows that the sand wave formation is the result of disturbance action of neutral coherent structure, and the sand wave shape obtained in computations is identical to the practical one.
Coherence in electron transfer pathways.
Skourtis, Spiros S; Beratan, David N; Waldeck, David H
2011-01-01
Central to the view of electron-transfer reactions is the idea that nuclear motion generates a transition state geometry at which the electron/hole amplitude propagates coherently from the electron donor to the electron acceptor. In the weakly coupled or nonadiabatic regime, the electron amplitude tunnels through an electronic barrier between the donor and acceptor. The structure of the barrier is determined by the covalent and noncovalent interactions of the bridge. Because the tunneling barrier depends on the nuclear coordinates of the reactants (and on the surrounding medium), the tunneling barrier is highly anisotropic, and it is useful to identify particular routes, or pathways, along which the transmission amplitude propagates. Moreover, when more than one such pathway exists, and the paths give rise to comparable transmission amplitude magnitudes, one may expect to observe quantum interferences among pathways if the propagation remains coherent. Given that the effective tunneling barrier height and width are affected by the nuclear positions, the modulation of the nuclear coordinates will lead to a modulation of the tunneling barrier and hence of the electron flow. For long distance electron transfer in biological and biomimetic systems, nuclear fluctuations, arising from flexible protein moieties and mobile water bridges, can become quite significant. We discuss experimental and theoretical results that explore the quantum interferences among coupling pathways in electron-transfer kinetics; we emphasize recent data and theories associated with the signatures of chirality and inelastic processes, which are manifested in the tunneling pathway coherence (or absence of coherence). PMID:23833692
Sroufe, L. Alan
1979-01-01
Based on research on patterns of infant-caregiver attachment, a theory of individual development is proposed. Principles of the theory include a focus on adaptation, a view of the person as a coherent whole, a central role for affective constructs and emotion, and a focus on individual differences. (GC)
Electromagnetic spatial coherence wavelets
International Nuclear Information System (INIS)
The recently introduced concept of spatial coherence wavelets is generalized for describing the propagation of electromagnetic fields in the free space. For this aim, the spatial coherence wavelet tensor is introduced as an elementary amount, in terms of which the formerly known quantities for this domain can be expressed. It allows analyzing the relationship between the spatial coherence properties and the polarization state of the electromagnetic wave. This approach is completely consistent with the recently introduced unified theory of coherence and polarization for random electromagnetic beams, but it provides a further insight about the causal relationship between the polarization states at different planes along the propagation path. (author)
Directory of Open Access Journals (Sweden)
Ali Riza Cenk Celebi
2016-01-01
Full Text Available Purpose. To compare central corneal thickness (CCT values via Spectral Domain-Optical Coherence Tomography (SD-OCT and ultrasonic pachymetry in patients with severe dry eye disease (DED to determine the level of agreement between these 2 methods. Methods. The paired samples t-test was used to compare CCT values in severe DED patients. Matching analysis between methods was performed using intraclass correlation coefficient (ICC. Intrasession reliability of the measurement methods was calculated via the concordance correlation coefficient (CCC, variation equivalent, and Pearson’s correlation coefficient. The Bland-Altman procedure was used to graphically represent the differences between CCT values. Results. The study included 56 eyes of 24 female and 4 male patients. Mean age of the patients was 50.9±11.3 years. Mean CCT via Cirrus SD-OCT was 523.82±30.98 μm versus 530.050±31.85 μm via ultrasonic pachymetry (paired samples t-test, P<0.001. The Bland-Altman plot showed good agreement between the examiners. The ICC for repeatability was 0.974. The CCC between the 2 methods’ CCT values was 0.973. The variation equivalent was 0.976 and Pearson’s correlation coefficient was 99.3%, which also indicated high correlation between the 2 methods’ measurements. Conclusions. The present findings show that in patients with severe DED Cirrus SD-OCT provides reliable intraobserver CCT values.
Conformal field theory at central charge c=0: A measure of the indecomposability (b) parameters
International Nuclear Information System (INIS)
A good understanding of conformal field theory (CFT) at c=0 is vital to the physics of disordered systems, as well as geometrical problems such as polymers and percolation. Steady progress has shown that these CFTs should be logarithmic, with indecomposable operator product expansions, and indecomposable representations of the Virasoro algebra. In one of the earliest papers on the subject, V. Gurarie introduced a single parameter b to quantify this indecomposability in terms of the logarithmic partner t of the stress-energy tensor T. He and A. Ludwig conjectured further that b=-5/8 for polymers and b=5/6 for percolation. While a lot of physics may be hidden behind this parameter - which has also given rise to a lot of discussions - it had remained very elusive up to now, due to the lack of available methods to measure it experimentally or numerically, in contrast say with the central charge. We show in this paper how to overcome the many difficulties in trying to measure b. This requires control of a lattice scalar product, lattice Jordan cells, together with a precise construction of the state L-2|0>. The final result is that b=5/6 for polymers. For percolation, we find that b=-5/8 within an XXZ or supersymmetric representation. In the geometrical representation, we do not find a Jordan cell for L0 at level two (finite-size Hamiltonian and transfer matrices are fully diagonalizable), so there is no b in this case.
International Nuclear Information System (INIS)
Photoassociation of ultracold rubidium atoms with femtosecond laser pulses is studied theoretically. The spectrum of the pulses is cut off in order to suppress pulse amplitude at and close to the atomic resonance frequency. This leads to long tails of the laser pulse as a function of time giving rise to coherent transients in the photoassociation dynamics. They are studied as a function of cut-off position and chirp of the pulse. Molecule formation in the electronically excited state is attributed to off-resonant excitation in the strong-field regime.
International Nuclear Information System (INIS)
Numerical solution to the Schroedinger equation with open boundary conditions is found out, which makes it possible to describe coherent generation in resonant-tunneling diodes in a broad interval of frequencies and field amplitudes. Within the linear field area approximation results obtained coincide with a high degree of accuracy with analytical results. The power of generation is calculated as a function of the current and other parameters of the resonant-tunneling diode. It is demonstrated that the high-power generation is possible in the quantum regime at frequencies exceeding the level width, i. e. within the THz range
Thomas I. Palley
2011-01-01
The financial crisis and Great Recession have prompted a rethink of monetary policy and central banking. The status quo insider rethink focuses on the role of monetary policy in dealing with asset bubbles; making the central bank the banking system supervisor; and how to deal with the problem of the zero lower bound to nominal interest rates. This paper presents an outsider reform program that focuses on central bank governance and independence; reshaping the economic philosophy of central ba...
Converting Coherence to Quantum Correlations
Ma, Jiajun; Yadin, Benjamin; Girolami, Davide; Vedral, Vlatko; Gu, Mile
2016-04-01
Recent results in quantum information theory characterize quantum coherence in the context of resource theories. Here, we study the relation between quantum coherence and quantum discord, a kind of quantum correlation which appears even in nonentangled states. We prove that the creation of quantum discord with multipartite incoherent operations is bounded by the amount of quantum coherence consumed in its subsystems during the process. We show how the interplay between quantum coherence consumption and creation of quantum discord works in the preparation of multipartite quantum correlated states and in the model of deterministic quantum computation with one qubit.
Directory of Open Access Journals (Sweden)
Jinhai Huang
2016-01-01
Full Text Available Purpose. To compare between a new optical biometer (AL-Scan, Nidek Co., Aichi, Japan and an anterior segment optical coherence tomographer (Visante AS-OCT, Carl Zeiss Meditec, Dublin, USA for measuring central corneal thickness (CCT, anterior chamber depth (ACD, and aqueous depth (AD. Methods. Sixty-three eyes of 63 normal subjects were examined with AL-Scan and Visante AS-OCT in this prospective study. One eye per subject was measured three times with both devices to record their CCT, ACD, and AD. All procedures were performed by the same operator. Agreement between the two devices was assessed using paired t-tests, Bland-Altman plots, and 95% limits of agreement (LoA. Results. The mean CCT, ACD, and AD measured by AL-Scan were 538.59±27.37 μm, 3.70±0.30 mm, and 3.16±0.30 mm, respectively. The mean values obtained by the Visante OCT were 536.14±26.61 μm for CCT, 3.71±0.29 mm for ACD, and 3.17±0.29 mm for AD. The mean CCT by the AL-Scan was higher than that obtained by the Visante AS-OCT (difference = 2.45±6.07 μm, P<0.05. The differences in ACD and AD measurements were not statistically significant. The 95% LoA of CCT, ACD, and AD were between −9.44 and 14.35 μm, −0.15 and 0.12 mm, and −0.15 and 0.12 mm, respectively. Conclusions. Since these two devices were comparable for measuring CCT, ACD, and AD, their results can be interchangeably used in the clinic.
Huang, Jinhai; Lu, Weicong; Savini, Giacomo; Chen, Hao; Wang, Chengfang; Yu, Xinxin; Bao, Fangjun; Wang, Qinmei
2016-01-01
Purpose. To compare between a new optical biometer (AL-Scan, Nidek Co., Aichi, Japan) and an anterior segment optical coherence tomographer (Visante AS-OCT, Carl Zeiss Meditec, Dublin, USA) for measuring central corneal thickness (CCT), anterior chamber depth (ACD), and aqueous depth (AD). Methods. Sixty-three eyes of 63 normal subjects were examined with AL-Scan and Visante AS-OCT in this prospective study. One eye per subject was measured three times with both devices to record their CCT, ACD, and AD. All procedures were performed by the same operator. Agreement between the two devices was assessed using paired t-tests, Bland-Altman plots, and 95% limits of agreement (LoA). Results. The mean CCT, ACD, and AD measured by AL-Scan were 538.59 ± 27.37 μm, 3.70 ± 0.30 mm, and 3.16 ± 0.30 mm, respectively. The mean values obtained by the Visante OCT were 536.14 ± 26.61 μm for CCT, 3.71 ± 0.29 mm for ACD, and 3.17 ± 0.29 mm for AD. The mean CCT by the AL-Scan was higher than that obtained by the Visante AS-OCT (difference = 2.45 ± 6.07 μm, P LoA of CCT, ACD, and AD were between -9.44 and 14.35 μm, -0.15 and 0.12 mm, and -0.15 and 0.12 mm, respectively. Conclusions. Since these two devices were comparable for measuring CCT, ACD, and AD, their results can be interchangeably used in the clinic. PMID:27403339
International Nuclear Information System (INIS)
Laser cooling of molecules employing broadband optical pumping involves a timescale separation between laser excitation and spontaneous emission. Here, we optimize the optical pumping step using shaped laser pulses. We derive two optimization functionals to drive population into those excited state levels that have the largest spontaneous emission rates to the target state. We show that, when using optimal control, laser cooling of molecules works even if the Franck–Condon map governing the transitions is preferential to heating rather than cooling. Our optimization functional is also applicable to the laser cooling of other degrees of freedom provided the cooling cycle consists of coherent excitation and dissipative de-excitation steps whose timescales are separated. (paper)
Maximally coherent mixed states: Complementarity between maximal coherence and mixedness
Singh, Uttam; Bera, Manabendra Nath; Dhar, Himadri Shekhar; Pati, Arun Kumar
2015-05-01
Quantum coherence is a key element in topical research on quantum resource theories and a primary facilitator for design and implementation of quantum technologies. However, the resourcefulness of quantum coherence is severely restricted by environmental noise, which is indicated by the loss of information in a quantum system, measured in terms of its purity. In this work, we derive the limits imposed by the mixedness of a quantum system on the amount of quantum coherence that it can possess. We obtain an analytical trade-off between the two quantities that upperbound the maximum quantum coherence for fixed mixedness in a system. This gives rise to a class of quantum states, "maximally coherent mixed states," whose coherence cannot be increased further under any purity-preserving operation. For the above class of states, quantum coherence and mixedness satisfy a complementarity relation, which is crucial to understand the interplay between a resource and noise in open quantum systems.
Barrow, W. M.; Fairhurst, R. J.; Metcalf, R. V.
2007-12-01
Recent exhumation models for eclogite terranes have focused on the exhumation of sialic rocks. Exhumed high pressure terranes are typically > 85% - 90% sialic material with only minor amounts of mafic and ultramafic rock. Most known metabasitic eclogites are blocks in mélange rather than large coherent bodies. The Central Metamorphic terrane (CMt) is a large (~300 km3) coherent, fault-bounded package of metabasites thought to represent a remnant of a downing plate subducted in an intra-oceanic convergent margin. Thermochronology indicates that the CMt was metamorphosed and later accreted to the base of the Trinity ophiolite along the Trinity fault during Early Permian extension (Hbl and Musc 40Ar/39Ar ages of 275 Ma - 294 Ma). Previous work suggested that the peak metamorphic temperatures and pressures were ~650°C and 0.4 to 0.8 GPa (Peacock and Norris, 1989) which is consistent with the amphibolite facies mineral assemblage. Trace element data confirm the NMORB-like composition of CMt metabasite protoliths. Newly discovered relict textures, however, suggest that CMt amphibolites record much deeper subduction burial with subsequent decompression exhumation. A decompression sequence consisting of rutile cores within ilmenite crystals mantled by titanite is observed in CMt amphibolite samples. Zr-in-rutile thermometry (Watson et al., 2006) combined with experimental data for rutile stability in metabasites (Ernst and Lui, 1998) suggests that relict rutile crystals preserve early P-T conditions of ~600°C and > 1.3 GPa consistent with eclogite facies metamorphism. Transition from eclogite facies is further supported by ilmenite-plagioclase-amphibole symplectites suggesting replacement of garnet (Bhowmik and Roy, 2003) during decompression. Amphibole compositions vary significantly and reflect lower grade (low Na, Al, Ti actinolite) overprint of earlier amphibolite facies compositions (high Na, Al, Ti magnesio- hornblende). Application of the Al-Ti hornblende
International Nuclear Information System (INIS)
A long standing unsolved puzzle is the very small rate of surface diffusion of ad-sorbates in the low temperature STM in the regime of quantum diffusion, differing by orders of magnitude from the results of modern quantum theories of surface diffusion (QTSD) based on ab initio potential energy surfaces. We investigate whether decoherence mechanisms, neglected in QTSD, can shed some light on these discrepancies. A quantum-mechanical theory is presented treating the entanglement of adsorbates with their environment (phonons, electron-hole pairs, gravitons). Time dependent wave packet evolution including the environmental modes indicates possible paths towards an explanation of the observed discrepancies and gives an insight into phenomenological descriptions like adsorbate localization, quantum Zeno effect (permenant 'measurement' by specific environmental excitations) and wave function collapse.
Development of coherent x-ray lasers
International Nuclear Information System (INIS)
Proposed x-ray laser applications such as interferometry and holography require coherent radiation. The fact that x-ray laser media are short-lived high-temperature plasmas leads to very different coherence properties from those of ordinary lasers. Research aimed at developing theoretical models and experimentally characterizing and improving x-ray laser coherence is discussed. Longitudinal coherence is already sufficient for several applications due to the narrow linewidths. However, transverse coherence is estimated to be poor for most current x-ray lasers. To quantify these estimates and to design better lasers, both wave and geometric optics propagation and coherence theories have been developed. These theories and resulting predictions of the coherence length are presented and compared. Measurements of x-ray laser beam patterns and coherence lengths are presented and compared to detailed theoretical simulations. Designs for more coherent lasers are given
Coherent states, wavelets, and their generalizations
Ali, Syed Twareque; Gazeau, Jean-Pierre
2014-01-01
This second edition is fully updated, covering in particular new types of coherent states (the so-called Gazeau-Klauder coherent states, nonlinear coherent states, squeezed states, as used now routinely in quantum optics) and various generalizations of wavelets (wavelets on manifolds, curvelets, shearlets, etc.). In addition, it contains a new chapter on coherent state quantization and the related probabilistic aspects. As a survey of the theory of coherent states, wavelets, and some of their generalizations, it emphasizes mathematical principles, subsuming the theories of both wavelets and coherent states into a single analytic structure. The approach allows the user to take a classical-like view of quantum states in physics. Starting from the standard theory of coherent states over Lie groups, the authors generalize the formalism by associating coherent states to group representations that are square integrable over a homogeneous space; a further step allows one to dispense with the group context altoget...
Central Bank Communication and Monetary Policy: A Survey of Theory and Evidence
Alan S. Blinder; Michael Ehrmann; Marcel Fratzscher; Jakob de Haan; David-Jan Jansen
2008-01-01
Over the last two decades, communication has become an increasingly important aspect of monetary policy. These real-world developments have spawned a huge new scholarly literature on central bank communication —mostly empirical, and almost all of it written in this decade. We survey this evergrowing literature. The evidence suggests that communication can be an important and powerful part of the central bank’s toolkit since it has the ability to move financial markets, to enhance the predicta...
Centralization and accountability: Theory and evidence from the Clear Air Act
Federico Boffa; Giacomo A. M. Ponzetto; Amedeo Piolatto
2013-01-01
This paper studies fiscal federalism when voter information varies across regions. We develop a model of political agency with heterogeneously informed voters. Rent-seeking politicians provide public goods to win the votes of the informed. As a result, rent extraction is lower in regions with higher information. In equilibrium, electoral discipline has decreasing returns. Thus, political centralization reduces aggregate rent extraction. When the central government provides public goods unifor...
Dental Optical Coherence Tomography
Kun-Feng Lin; Jui-che Tsai; Ching-Cheng Chuang; Shyh-Yuan Lee; Yi-Ching Ho; Yao-Sheng Hsieh; Chia-Wei Sun
2013-01-01
This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed.
Symmetric, coherent, Choquet capacities
Kadane, Joseph B.; Wasserman, Larry
1996-01-01
Choquet capacities are a generalization of probability measures that arise in robustness, decision theory and game theory. Many capacities that arise in robustness are symmetric or can be transformed into symmetric capacities. We characterize the extreme points of the set of upper distribution functions corresponding to coherent, symmetric Choquet capacities on [0, 1]. We also show that the set of 2-alternating capacities is a simplex and we give a Choquet representation of this set.
Capuzzi, Pablo; Chitra, R.; Menotti, Chiara; Minguzz, Anna; Vignolo, Patrizia
2006-05-01
opportunity to thank all the participants of ICOMP-X, and in particular the contributors to this issue, for the high quality of science presented at the conference and in this journal. The success of the conference would not have been possible without the program committee which included D Charalambidis, L Cocke, R Freeman, Y Fujimura, S Goreslavsky, A L'Huillier, F Krausz, R Levis, S H Lin, A Maquet, J Marangos, K Midorikawa, G Mourou, P Salieres, W Sandner, K Schafer, A Scrinzi, A M Sergeev, H Stapelfeldt, A Starace, J Ullrich, M Vrakking, and K Yamanouchi. A particularly lively atmosphere in the discussions was ensured by many students who were able to participate in the conference, in part due to generous support of the Canadian Institute for Photonic Innovations (CIPI) to the Canadian, and of the US Department of Energy Office of Basic Energy Sciences to the American students. Additional support to the conference was provided by the Natural Sciences and Engineering Research Council (NSERC), the National Research Council of Canada (NRC), Pfeiffer Vacuum, Femtolasers Produktions GmbH, Roentdek Handels GmbH, Coherent Laser Products, and Amplitude Technologies. Last but not least, the guest editors of this special issue would like to acknowledge the tremendous amount of work done by the staff of J. Phys. B in handling all aspects of the publication process. In particular, we would like to thank Isabelle Auffret-Babak, Alice Malhador and Joanna Dingley from the editorial team, Katie Gerrard in production and the Editor-in-Chief, Professor J-M Rost.
On Radar Resolution in Coherent Change Detection.
Energy Technology Data Exchange (ETDEWEB)
Bickel, Douglas L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-11-01
It is commonly observed that resolution plays a role in coherent change detection. Although this is the case, the relationship of the resolution in coherent change detection is not yet defined . In this document, we present an analytical method of evaluating this relationship using detection theory. Specifically we examine the effect of resolution on receiver operating characteristic curves for coherent change detection.
On the Central Charge of Spacetime Current Algebras and Correlators in String Theory on AdS3
Kim, Jihun; Porrati, Massimo
2015-01-01
Spacetime Virasoro and affine Lie algebras for strings propagating in AdS3 are known to all orders in $\\alpha'$. The central extension of such algebras is a string vertex, whose expectation value can depend on the number of long strings present in the background but should be otherwise state-independent. In hep-th/0106004, on the other hand, a state-dependent expectation value was found. Another puzzling feature of the theory is lack of cluster decomposition property in certain connected corr...
Quantum Coherence as a Resource
Streltsov, Alexander; Plenio, Martin B
2016-01-01
The coherent superposition of states, in combination with energy quantization, represents one of the most fundamental features that mark the departure of quantum mechanics from the classical realm. Quantum coherence in many-body systems embodies the essence of entanglement and is an essential ingredient for a plethora of physical phenomena in quantum optics, quantum information, solid state physics, and nanoscale thermodynamics. In recent years, research on the presence and functional role of quantum coherence in biological systems has also attracted a considerable interest. Despite the fundamental importance of quantum coherence, the development of a rigorous theory of quantum coherence as a physical resource has only been initiated recently. In this Colloquium we discuss and review the development of this rapidly growing research field that encompasses the characterization, quantification, manipulation, dynamical evolution, and operational application of quantum coherence.
Chowdhury, Suban Kumar; Hel Kafi, Abdullah
2015-01-01
"The paper examines the foreign policy of the United States and Russia towards Central Asia by reviewing selective foreign policy discourses in the context of the Heartland theory. In effect, the central formulation of the study rests on this research question: to what extent is the Heartland theory influential in the foreign policy of the United States and Russia? The analysis is therefore organized by first conducting a comparative/contrast approach of USA and Russian policies via each othe...
Marcotte, Ronald E.
2005-01-01
This physical chemistry lecture demonstration is designed to aid the understanding of intramolecular energy transfer processes as part of the presentation of the theory of unimolecular reaction rates. Coupled pendulums are used to show the rate of migration of energy between oscillators under resonant and nonresonant conditions with varying…
World-Economic Theories and Problems: Quigley vs. Wallerstein vs Central Civilization
David Wilkinson
2015-01-01
This is one in a series of papers on civilizational issues. Its predecessors have argued for the existence of a world system/civilization, "Central Civilization," born regionally in the Middle East about 1500 B.C. in the collision of two smaller, expanding local civilizations, expanded throughout the globe, engulfing all competing civilizations to become the unique global social system in the last 100-150 years. If continuing social struggles both are and imply continuing social entities, the...
Mkasiwa, Tausi
2011-01-01
This research investigates the phenomenon of budgeting practices in the Tanzanian Central Government. It seeks to understand how budgeting systems under the New Public Management (NPM), World Bank- and IMF-exhorted systems were adopted and implemented. There were several motives for this research: the significance of budgeting in financial management, the sparsity of empirical studies on NPM in developing countries, and a call for an understanding of the local contexts of the country and an e...
Education in a Period or Social Upheaval. Educational Theories and Concepts in Central East Europe
1994-01-01
The volume contains contributions from nine different Central- and East-European countries which give a total impression of the upheaval in the field of educational science in those countries. The contributions comprise three different focuses. "The first group is occupied with a review of history and the position of educational science in specific countries, in order in this way to gain prerequisites and perspectives for new pedagogical points of departure... The second group of contributors...
Centralization and Accountability: Theory and Evidence from the Clean Air Act
BOFFA, F.; Piolatto, A.; Ponzetto, G.A.M.
2012-01-01
This paper studies fiscal federalism when regions differ in voters’ ability to monitor public officials. We develop a model of political agency in which rent-seeking politicians provide public goods to win support from heterogeneously informed voters. In equilibrium, voter information increases government accountability but displays decreasing returns. Therefore, political centralization reduces aggregate rent extraction when voter information varies across regions. It increases welfare as lo...
World-Economic Theories and Problems: Quigley vs. Wallerstein vs Central Civilization
Directory of Open Access Journals (Sweden)
David Wilkinson
2015-08-01
Full Text Available This is one in a series of papers on civilizational issues. Its predecessors have argued for the existence of a world system/civilization, "Central Civilization," born regionally in the Middle East about 1500 B.C. in the collision of two smaller, expanding local civilizations, expanded throughout the globe, engulfing all competing civilizations to become the unique global social system in the last 100-150 years. If continuing social struggles both are and imply continuing social entities, there is social continuity-stabilities, trends and cycles--in the struggles forming and maintaining Central Civilization.ill A consequence of accepting Central Civilization as a genuine entity, or a reason for treating it as a fruitful heuristic, is, in particular, the finding that it possesses a political cycle (states system--univcesal empire characteristic of other entities commonly treated as civilizations (Wilkinson, 1986; 1987, 53-56; 1988 as well as a political evolution (from multistate anarchy to balance-of-power incipient but never successfully established in other world systems (Wilkinson, 1985.
World-Economic Theories and Problems: Quigley vs. Wallerstein vs Central Civilization
Directory of Open Access Journals (Sweden)
David Wilkinson
2015-08-01
Full Text Available This is one in a series of papers on civilizational issues. Its predecessors have argued for the existence of a world system/civilization, "Central Civilization," born regionally in the Middle East about 1500 B.C. in the collision of two smaller, expanding local civilizations, expanded throughout the globe, engulfing all competing civilizations to become the unique global social system in the last 100-150 years. If continuing social struggles both are and imply continuing social entities, there is social continuity-stabilities, trends and cycles--in the struggles forming and maintaining Central Civilizations. A consequence of accepting Central Civilization as a genuine entity, or a reason for treating it as a fruitful heuristic, is, in particular, the finding that it possesses a political cycle (states system--universal empire characteristic of other entities commonly treated as civilizations (Wilkinson, 1986; 1987, 53-56; 1988 as well as a political evolution (from multistate anarchy to balance-of-power incipient but never successfully established in other world systems (Wilkinson, 1985.
Witnessing multipartite entanglement by detecting coherence
Girolami, Davide
2015-01-01
The characterization of quantum coherence in the context of quantum information theory and its interplay with quantum correlations is currently subject of intense study. Several theoretical quantifiers of coherence have been proposed, and links to quantum correlation measures have been provided. We here propose an experimental strategy to witness the presence of entanglement in multipartite systems by evaluating coherence. We test our scheme by simulating coherence and entanglement detection in a three-qubit GHZ-diagonal state.
Blanka Kesic; Pavao Komadina; Dragan Cisic
2000-01-01
A number of methods are available for determining the limits of port gravitational areas, geographic, geometrical, mainland-tariff method or total transport cost method. The basic drawback of this methods is that they take in the account either cost or geographical elements Unified theory of the port gravitational areas, under development at Maritime faculty Rijeka, takes into account other logistic elements which in today's transport conditions can be crucial in choosing the direction of the...
Operator properties of generalized coherent state systems
Indian Academy of Sciences (India)
N Mukunda
2001-02-01
The main properties of standard quantum mechanical coherent states and the two generalizations of Klauder and of Perelomov are reviewed. For a system of generalized coherent states in the latter sense, necessary and sufﬁcient conditions for existence of a diagonal coherent stable representation for all Hilbert-Schmidt operators are obtained. The main ingredients are Clebsch-Gordan theory and induced representation theory.
Quantum speed limits, coherence and asymmetry
Marvian, Iman; Spekkens, Robert W.; Zanardi, Paolo
2015-01-01
The resource theory of asymmetry is a framework for classifying and quantifying the symmetry-breaking properties of both states and operations relative to a given symmetry. In the special case where the symmetry is the set of translations generated by a fixed observable, asymmetry can be interpreted as coherence relative to the observable eigenbasis, and the resource theory of asymmetry provides a framework to study this notion of coherence. We here show that this notion of coherence naturall...
Low Coherence Optic Source Characterization
International Nuclear Information System (INIS)
This work presents the results of characterization of the coherence length of an optic source using interferometric techniques and digital signal processing. Optic sources are not ideal because of random behavior in the emission process and spectral dispersion. Optical coherence is the ability of light to generate interference, either temporal or spatial. In time domain, coherence is expressed by the autocorrelation function. In case of monochromatic laser, it has larger coherence length, in the order of tenths to hundredth of meters, rather than a superluminiscent diode (SLD), which is shorter, in the orders of millimeters. This work presents a method for measuring coherence length using an automated Michelson interferometer and a SLD with central wavelength λ0 = 1302.4 nm and acquisition system.by means of a soundcard in a personal computer
Channels that do not generate coherence
Hu, Xueyuan
2016-07-01
We define the non-coherence-generating channel as the completely positive trace-preserving map which does not generate quantum coherence from an incoherent state. The incoherent operations are the strict subset of the non-coherence-generating channels. Although the relative entropy of coherence is monotonically decreasing under the non-coherence-generating channels, we prove that the coherence of formation may increase under such channels. Interestingly, by building a mathematical relation between the coherence of formation and the entanglement of formation, we show that the coherence of formation of a single-qubit state is never increased by a non-coherence-generating channel. This leads to the superadditivity property for the coherence increasing power of quantum channels, namely, while two channels cannot increase coherence individually, they may increase the quantum coherence of a composed system. Further, we derive the general form of the rank-2 non-coherence-generating qubit channels. Our results contribute to the resource theory of quantum coherence.
Thommes, Jan; Happel, Christoph M.; Thrane, Lars; Yelbuz, T. Mesud
2010-01-01
In vivo analysis of cardiac physiology and non-invasive imaging of the beating early embryonic heart in 2 and 3D remain a challenge in cardiovascular development research. 3D-imaging of the beating heart relies on gating of the acquired images according to the cardiac cycle. Mostly ECG triggering is used for this purpose, e.g. in MRT or CT of human hearts. For visualization of embryonic chick hearts with high-resolution optical coherence tomography (OCT), a gating trigger generated by laser D...
You, Yi-Jing; Wang, Chengming; Lin, Yi-Lun; Zaytsev, Alexey; Xue, Ping; Pan, Ci-Ling
2016-02-01
We report on the ultrahigh-resolution optical coherence tomography (OCT) with a novel high-power supercontinuum (SC) light source generated by noise-like pulses from an Yb-doped fiber laser. The SC spectrum is flat with a bandwidth of 420 nm centered around ~1.3 μm. The light source is successfully employed in a time-domain OCT (TD-OCT), achieving an axial resolution of 2.3 μm. High resolution fiber-based spectral-domain OCT (SD-OCT) imaging of bio-tissue was also demonstrated.
Grillo, Lola M.; Wang, Diane L.; Ramachandran, Rithambara; Ehrlich, Alyssa C.; De Moraes, Carlos Gustavo; Ritch, Robert; Hood, Donald C.
2016-01-01
Purpose To determine the extent to which the 24-2 visual field (VF) misses macular damage confirmed with both 10-2 VF and optical coherence tomography (OCT) tests and to evaluate the patterns of damage missed. Methods One hundred forty-one eyes of 141 glaucoma patients or suspects underwent 24-2 VF (mean deviation [MD] better than −6 dB), 10-2 VF, and OCT testing. Retinal nerve fiber layer (RNFL) and retinal ganglion cell plus inner plexiform (RGC+) probability plots were combined with 10-2 V...
Coherence and correspondence in medicine
Directory of Open Access Journals (Sweden)
Thomas G. Tape
2009-03-01
Full Text Available Many controversies in medical science can be framed as tension between a coherence approach (which seeks logic and explanation and a correspondence approach (which emphasizes empirical correctness. In many instances, a coherence-based theory leads to an understanding of disease that is not supported by empirical evidence. Physicians and patients alike tend to favor the coherence approach even in the face of strong, contradictory correspondence evidence. Examples include the management of atrial fibrillation, treatment of acute bronchitis, and the use of Vitamin E to prevent heart disease. Despite the frequent occurrence of controversy stemming from coherence-correspondence conflicts, medical professionals are generally unaware of these terms and the philosophical traditions that underlie them. Learning about the coherence-correspondence distinction and using the best of both approaches could not only help reconcile controversy but also lead to striking advances in medical science.
Robustness of Coherence: An Operational and Observable Measure of Quantum Coherence
Napoli, Carmine; Bromley, Thomas R.; Cianciaruso, Marco; Piani, Marco; Johnston, Nathaniel; Adesso, Gerardo
2016-04-01
Quantifying coherence is an essential endeavor for both quantum foundations and quantum technologies. Here, the robustness of coherence is defined and proven to be a full monotone in the context of the recently introduced resource theories of quantum coherence. The measure is shown to be observable, as it can be recast as the expectation value of a coherence witness operator for any quantum state. The robustness of coherence is evaluated analytically on relevant classes of states, and an efficient semidefinite program that computes it on general states is given. An operational interpretation is finally provided: the robustness of coherence quantifies the advantage enabled by a quantum state in a phase discrimination task.
Robustness of coherence: An operational and observable measure of quantum coherence
Napoli, Carmine; Cianciaruso, Marco; Piani, Marco; Johnston, Nathaniel; Adesso, Gerardo
2016-01-01
Quantifying coherence is an essential endeavour for both quantum foundations and quantum technologies. Here the robustness of coherence is defined and proven a full monotone in the context of the recently introduced resource theories of quantum coherence. The measure is shown to be observable, as it can be recast as the expectation value of a coherence witness operator for any quantum state. The robustness of coherence is evaluated analytically on relevant classes of states, and an efficient semidefinite program that computes it on general states is given. An operational interpretation is finally provided: the robustness of coherence quantifies the advantage enabled by a quantum state in a phase-discrimination task.
Gauge field theory of horizontal symmetry generated by a central extension of the pauli algebra
International Nuclear Information System (INIS)
The standard model of particle physics is generalized so as to be furnished with a horizontal symmetry generated by an intermediate algebra between simple Lie algebras su(2) and su(3). Above a certain high-energy scale Λ, the horizontal gauge symmetry is postulated to hold so that the basic fermions, i.e., quarks and leptons, form its fundamental triplets, and a triplet and singlet of the horizontal gauge fields distinguish generational degrees of freedom. A horizontal scalar triplet is introduced to make the gauge fields supermassive by breaking the horizontal symmetry at Λ. From this scalar triplet, real scalar fields emerge that do not interact with fermions except for neutrino species and may have a substantial influence on the evolution of the universe. Another horizontal scalar triplet that breaks the electroweak symmetry at a low-energy scale Λ≅2 x 102 GeV reproduces all of the results of the Weinberg-Salam theory, produces hierarchical mass matrices with fewer unknown parameters in a unified way and predicts six massive scalar particles, some of which might be observed in future LHC experiments. (author)
Coherent Communication of Classical Messages
Harrow, Aram W.
2003-01-01
We define "coherent communication" in terms of a simple primitive, show it is equivalent to the ability to send a classical message with a unitary or isometric operation, and use it to relate other resources in quantum information theory. Using coherent communication, we are able to generalize super-dense coding to prepare arbitrary quantum states instead of only classical messages. We also derive single-letter formulae for the classical and quantum capacities of a bipartite unitary gate assi...
A Method for Ultrashort Electron Pulse Shape-Measurement Using Coherent Synchrotron Radiation
Geloni, G A; Schneidmiller, E A; Yurkov, M V
2003-01-01
In this paper we discuss a method for nondestructive measurements of the longitudinal profile of sub-picosecond electron bunches for X-Ray Free Electron Lasers (XFELs). The method is based on the detection of the Coherent Synchrotron Radiation (CSR) spectrum produced by a bunch passing a dipole magnet system. This work also contains a systematic treatment of synchrotron radiation theory which lies at the basis of CSR. Standard theory of synchrotron radiation uses several approximations whose applicability limits are often forgotten: here we present a systematic discussion about these assumptions. Properties of coherent synchrotron radiation from an electron moving along an arc of a circle are then derived and discussed. We describe also an effective and practical diagnostic technique based on the utilization of an electromagnetic undulator to record the energy of the coherent radiation pulse into the central cone. This measurement must be repeated many times with different undulator resonant frequencies in or...
Quantum coherence of steered states
Hu, Xueyuan; Milne, Antony; Zhang, Boyang; Fan, Heng
2016-01-01
Lying at the heart of quantum mechanics, coherence has recently been studied as a key resource in quantum information theory. Quantum steering, a fundamental notion originally considered by Schödinger, has also recently received much attention. When Alice and Bob share a correlated quantum system, Alice can perform a local measurement to ‘steer’ Bob’s reduced state. We introduce the maximal steered coherence as a measure describing the extent to which steering can remotely create coherence; more precisely, we find the maximal coherence of Bob’s steered state in the eigenbasis of his original reduced state, where maximization is performed over all positive-operator valued measurements for Alice. We prove that maximal steered coherence vanishes for quantum-classical states whilst reaching a maximum for pure entangled states with full Schmidt rank. Although invariant under local unitary operations, maximal steered coherence may be increased when Bob performs a channel. For a two-qubit state we find that Bob’s channel can increase maximal steered coherence if and only if it is neither unital nor semi-classical, which coincides with the condition for increasing discord. Our results show that the power of steering for coherence generation, though related to discord, is distinct from existing measures of quantum correlation.
Quantum coherence of steered states.
Hu, Xueyuan; Milne, Antony; Zhang, Boyang; Fan, Heng
2016-01-01
Lying at the heart of quantum mechanics, coherence has recently been studied as a key resource in quantum information theory. Quantum steering, a fundamental notion originally considered by Schödinger, has also recently received much attention. When Alice and Bob share a correlated quantum system, Alice can perform a local measurement to 'steer' Bob's reduced state. We introduce the maximal steered coherence as a measure describing the extent to which steering can remotely create coherence; more precisely, we find the maximal coherence of Bob's steered state in the eigenbasis of his original reduced state, where maximization is performed over all positive-operator valued measurements for Alice. We prove that maximal steered coherence vanishes for quantum-classical states whilst reaching a maximum for pure entangled states with full Schmidt rank. Although invariant under local unitary operations, maximal steered coherence may be increased when Bob performs a channel. For a two-qubit state we find that Bob's channel can increase maximal steered coherence if and only if it is neither unital nor semi-classical, which coincides with the condition for increasing discord. Our results show that the power of steering for coherence generation, though related to discord, is distinct from existing measures of quantum correlation. PMID:26781214
Electroencephalograpic coherence
Directory of Open Access Journals (Sweden)
Simon Brežan
2004-08-01
Full Text Available Different brain areas process various aspects of information in parallel as well as segregated way. It is not known, how is this information integrated into a unitary percept or action. The binding problem is one of the key problems in understanding brain function. Synchronized oscillatory activity of neurons is one possible mechanism of the functional integration of different communicating brain areas. The binding has been well-studied in the visual system, but it could also serve as a mechanism in visuomotor integration or functional coupling present with other brain processes and behavioural modes (perception, complex motor behaviour, selective attention, learning, working memory, etc.. Interregional synchronization of the electroencephalographic (EEG signal can be determined by EEG coherence analysis. In the article we present a research example of coherence changes in a visuomotor task. During this task, coherence between visual and motor brain areas increased. This might reflect functional coupling between those areas, but it could also be influenced by other cognitive processes (e.g. selective attention. Coherence analysis is suitable for studying integrative brain function. Because it measures only one of the possible mechanisms of integration, it offers promise especially when combined with other electrophysiological and functional imaging methods.
Coherence, Pseudo-Coherence, and Non-Coherence.
Enkvist, Nils Erik
Analysis of the factors that make a text coherent or non-coherent suggests that total coherence requires cohesion not only on the textual surface but on the semantic level as well. Syntactic evidence of non-coherence includes lack of formal agreement blocking a potential cross-reference, anaphoric and cataphoric references that do not follow their…
Coherence and Sense of Coherence
DEFF Research Database (Denmark)
Dau, Susanne
2014-01-01
that sense of coherence is both related to conditional matters as learning environments, structure, clarity and linkage but also preconditioned matters and prerequisites among participants related to experiences and convenience. It is stressed that this calls for continuous assessment and reflections...
Coherence and Sense of Coherence
DEFF Research Database (Denmark)
Dau, Susanne
2014-01-01
that sense of coherence is both related to conditional matters as learning environments, structure, clarity and linkage but also preconditioned matters and prerequisites among participants related to experiences and convenience. It is stressed that this calls for continuous assessment and reflections...... upon these terms and conditions if the student shall be able acquire the necessary competencies....
Is laser light coherent: Photon statistics in coherently driven resonators
International Nuclear Information System (INIS)
It is well known that lasers and masers far above threshold produce coherent radiation, just like a harmonic oscillator excited by a classical force remains in a coherent state. On the other hand, the dipole interaction of light with matter is described in the simplest case of a single two-level atom interacting with a single mode of the electromagnetic field by the Jaynes-Cummings Hamiltonian. At this level, the field does not evolve towards a coherent state. A standard model of a laser or maser consists of a lossy resonator in which inverted two-level atoms are injected at random times. Paradoxically, it appears then that the incoherent nature of the pumping mechanism and losses must be responsible for the coherent output of lasers. In this paper, the authors investigate at which point precisely in laser theory the output becomes coherent. What they find is that indeed, coherence is due to incoherent processes: averages over fluctuations and noise smear out the discreteness of phases in the quantum-mechanical Jaynes-Cummings model (JCM), so that the electrons in the atoms act much more like a classical current. They also show that there are many more possible regimes of operation of lasers and masers than generally recognized. Depending upon noise and damping, the field can evolve towards a variety of states, such as e.g. coherent, sub-Poissonian, or even number state
Hsu, Liang-Yan; Rabitz, Herschel
2015-07-01
We introduce a tunneling effect by a driving field, referred to as coherent revival of tunneling (CRT), corresponding to complete tunneling (transmission coefficient =1 ) that is revived from the circumstance of total reflection (transmission coefficient ≈0 ) through application of an appropriate perpendicular high-frequency ac field. To illustrate CRT, we simulate electron transport through fish-bone-like quantum-dot arrays by using single-particle Green's functions along with Floquet theory, and we explore the corresponding current-field amplitude characteristics as well as current-polarization characteristics. In regard to the two characteristics, we show that CRT exhibits entirely different features than coherent destruction of tunneling and photon-assisted tunneling. We also discuss two practical conditions for experimental realization of CRT.
Emotion Regulation and Emotion Coherence: Evidence for Strategy-Specific Effects
Dan-Glauser, Elise S.; Gross, James J.
2013-01-01
One of the central tenets of emotion theory is that emotions involve coordinated changes across experiential, behavioral, and physiological response domains. Surprisingly little is known, however, on how the strength of this emotion coherence is altered when people try to regulate their emotions. To address this issue, we recorded experiential, behavioral, and physiological responses while participants watched negative and positive pictures. Cross-correlations were used to quantify emotion co...
Jones, Dean P
2016-04-01
When Rafael Radi and I wrote about Helmut Sies for the Redox Pioneer series, I was disappointed that the Editor restricted us to the use of "Pioneer" in the title. My view is that Helmut was always ahead of the pioneers: He was a scout discovering paths for exploration and a trailblazer developing strategies and methods for discovery. I have known him for nearly 40 years and greatly enjoyed his collegiality as well as brilliance in scientific scholarship. He made monumental contributions to 20th century physiological chemistry beginning with his first measurement of H2O2 in rat liver. While continuous H2O2 production is dogma today, the concept of H2O2 production in mammalian tissues was largely buried for half a century. He continued this leadership in research on oxidative stress, GSH, selenium, and singlet oxygen, during the timeframe when physiological chemistry and biochemistry transitioned to contemporary 21st century systems biology. His impact has been extensive in medical and health sciences, especially in nutrition, aging, toxicology and cancer. I briefly summarize my interactions with Helmut, stressing our work together on the redox code, a set of principles to link mitochondrial respiration, bioenergetics, H2O2 metabolism, redox signaling and redox proteomics into central redox theory. PMID:27095208
Energy cost of creating quantum coherence
Misra, Avijit; Singh, Uttam; Bhattacharya, Samyadeb; Pati, Arun Kumar
2016-05-01
We consider physical situations where the resource theories of coherence and thermodynamics play competing roles. In particular, we study the creation of quantum coherence using unitary operations with limited thermodynamic resources. We find the maximal coherence that can be created under unitary operations starting from a thermal state and find explicitly the unitary transformation that creates the maximal coherence. Since coherence is created by unitary operations starting from a thermal state, it requires some amount of energy. This motivates us to explore the trade-off between the amount of coherence that can be created and the energy cost of the unitary process. We also find the maximal achievable coherence under the constraint on the available energy. Additionally, we compare the maximal coherence and the maximal total correlation that can be created under unitary transformations with the same available energy at our disposal. We find that when maximal coherence is created with limited energy, the total correlation created in the process is upper bounded by the maximal coherence, and vice versa. For two-qubit systems we show that no unitary transformation exists that creates the maximal coherence and maximal total correlation simultaneously with a limited energy cost.
Directory of Open Access Journals (Sweden)
Raymond Trevor Bradley
2009-12-01
Full Text Available This article presents theory and research on the scientific study of emotion thatemphasizes the importance of coherence as an optimal psychophysiological state. Adynamic systems view of the interrelations between psychological, cognitive andemotional systems and neural communication networks in the human organism providesa foundation for the view presented. These communication networks are examined froman information processing perspective and reveal a fundamental order in heart-braininteractions and a harmonious synchronization of physiological systems associated withpositive emotions. The concept of coherence is drawn on to understand optimalfunctioning which is naturally reflected in the heart’s rhythmic patterns. Research ispresented identifying various psychophysiological states linked to these patterns, withneurocardiological coherence emerging as having significant impacts on well being.These include psychophysiological as well as improved cognitive performance. Fromthis, the central role of the heart is explored in terms of biochemical, biophysical andenergetic interactions. Appendices provide further details and research on;psychophysiological functioning, reference previous research in this area, details onresearch linking coherence with optimal cognitive performance, heart brainsynchronization and the energetic signature of the various psychophysiological modes.
Algebraic Theories and (Infinity,1)-Categories
Cranch, James
2010-11-01
We adapt the classical framework of algebraic theories to work in the setting of (infinity,1)-categories developed by Joyal and Lurie. This gives a suitable approach for describing highly structured objects from homotopy theory. A central example, treated at length, is the theory of E_infinity spaces: this has a tidy combinatorial description in terms of span diagrams of finite sets. We introduce a theory of distributive laws, allowing us to describe objects with two distributing E_infinity stuctures. From this we produce a theory of E_infinity ring spaces. We also study grouplike objects, and produce theories modelling infinite loop spaces (or connective spectra), and infinite loop spaces with coherent multiplicative structure (or connective ring spectra). We use this to construct the units of a grouplike E_infinity ring space in a natural manner. Lastly we provide a speculative pleasant description of the K-theory of monoidal quasicategories and quasicategories with ring-like structures.
Photoacoustics with coherent light
Directory of Open Access Journals (Sweden)
Emmanuel Bossy
2016-03-01
Full Text Available Since its introduction in the mid-nineties, photoacoustic imaging of biological tissue has been one of the fastest growing biomedical imaging modality, and its basic principles are now considered as well established. In particular, light propagation in photoacoustic imaging is generally considered from the perspective of transport theory. However, recent breakthroughs in optics have shown that coherent light propagating through optically scattering medium could be manipulated towards novel imaging approaches. In this article, we first provide an introduction to the relevant concepts in the field, and then review the recent works showing that it is possible to exploit the coherence of light in conjunction with photoacoustics. We illustrate how the photoacoustic effect can be used as a powerful feedback mechanism for optical wavefront shaping in complex media, and conversely show how the coherence of light can be exploited to enhance photoacoustic imaging, for instance in terms of spatial resolution or for designing minimally invasive endoscopic devices. Finally, we discuss the current challenges and perspectives down the road towards practical applications in the field of photoacoustic imaging.
Photoacoustics with coherent light.
Bossy, Emmanuel; Gigan, Sylvain
2016-03-01
Since its introduction in the mid-nineties, photoacoustic imaging of biological tissue has been one of the fastest growing biomedical imaging modality, and its basic principles are now considered as well established. In particular, light propagation in photoacoustic imaging is generally considered from the perspective of transport theory. However, recent breakthroughs in optics have shown that coherent light propagating through optically scattering medium could be manipulated towards novel imaging approaches. In this article, we first provide an introduction to the relevant concepts in the field, and then review the recent works showing that it is possible to exploit the coherence of light in conjunction with photoacoustics. We illustrate how the photoacoustic effect can be used as a powerful feedback mechanism for optical wavefront shaping in complex media, and conversely show how the coherence of light can be exploited to enhance photoacoustic imaging, for instance in terms of spatial resolution or for designing minimally invasive endoscopic devices. Finally, we discuss the current challenges and perspectives down the road towards practical applications in the field of photoacoustic imaging. PMID:27069874
Institute of Scientific and Technical Information of China (English)
何明烈; 戢焕奇
2008-01-01
Based on the investigation of the origin and definition of topic as well as the classification of textual coherence, this paper ana-lyzes the function of topic to non-coherence, imphcit coherence and explicit coherence, and concludes that topic relevance is the primary cri-terion for textual coherence.
Coherent states, pseudodifferential analysis and arithmetic
International Nuclear Information System (INIS)
Basic questions regarding families of coherent states include describing some constructions of such and the way they can be applied to operator theory or partial differential equations. In both questions, pseudodifferential analysis is important. Recent developments indicate that they can contribute to methods in arithmetic, especially modular form theory. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)
Revealing Hidden Coherence in Partially Coherent Light
Svozilík, Jiří; Peřina, Jan; Torres, Juan P
2015-01-01
The coherence of a system can be ultimately related to the nature of its correlations with the surroundings (outside world). The system can be, for instance, the polarization of a photon, which forms part of a polarization-entangled two-photon state, or the spatial shape of a coherent beam, where each spatial mode bears different polarizations. Whereas a local unitary transformation of the system do not affect its coherence, global unitary transformations modifying both the system and its surroundings can enhance its coherence transforming mutual correlations into coherence. The question naturally arises of what is the best measure that quantifies the correlations that can be turned into coherence, and how much coherence can be extracted. We answer both questions, and illustrate its application for some typical simple systems, with the aim at illuminating the general concept of enhancing coherence by modifying correlations.
Ledenyov, Dimitri O.; Ledenyov, Viktor O.
2013-01-01
The investment economy is a main characteristic of prosperous society. The investment portfolio management is a main financial problem, which has to be solved by the investment, commercial and central banks with the application of modern portfolio theory in the investment economy. We use the learning analytics together with the integrative creative imperative intelligent conceptual co-lateral adaptive thinking with the purpose to advance our scientific knowledge on the diversified investment ...
Negative Binomial and Multinomial States: probability distributions and coherent states
Fu, Hong-Chen; Sasaki, Ryu
1996-01-01
Following the relationship between probability distribution and coherent states, for example the well known Poisson distribution and the ordinary coherent states and relatively less known one of the binomial distribution and the $su(2)$ coherent states, we propose ``interpretation'' of $su(1,1)$ and $su(r,1)$ coherent states ``in terms of probability theory''. They will be called the ``negative binomial'' (``multinomial'') ``states'' which correspond to the ``negative'' binomial (multinomial)...
Asher, D. J.; Clube, S. V. M.; Napier, W. M.; Steel, D. I.
We review the theoretical and observational evidence that, on timescales relevant to mankind, the prime collision hazard is posed by temporally correlated impacts (coherent catastrophism, Δt ˜ 10 2-10 4 yr) rather than random ones (stochastic catastrophism, Δt ˜ 10 5-10 8 yr). The mechanism whereby coherent incursions into and through the terrestrial atmosphere occur is described as being the result of giant cometary bodies arriving in orbits with perihelia in the inner solar system. Hierarchical fragmentation of such large (100 km-plus) bodies — due to thermal stresses near perihelion, collisions in the asteroid belt, or passages through the Jovian Roche radius — results in numerous ˜kilometre-sized objects being left in short-period orbits, and appearing in telescopic searches as Apollo-type asteroids. Many more smaller objects, in the 10-100 metre size range and only recently observed, by the Spacewatch team, are expected to be in replenished clusters in particular orbits as a result of continuing disintegrations of large, differentiated, cometary objects. Gravitational perturbations by Jupiter bring these clusters around to have a node at 1 AU in a cyclic fashion, leading to impacts at certain times of year every few years during active periods lasting a few centuries, such periods being separated by intervals of a few millennia. Furthermore, fragmentations within the hierarchy result in significant bombardment commensurabilities ( Δt ˜ 10-10 2 yr) during active periods occurring at random intervals ( Δt ˜ 10 2-10 3 yr). It appears that the Earth has been subject to such impacts since the break-up of such a comet ˜2×10 4 years ago; currently we are not passing through a high-risk epoch, although some phenomena originating in the products of this break-up have been observed in the 20th century. This most recent hierarchical disintegration, associated with four well-known meteor showers and termed the Taurid Complex, is now recognized as resulting
Coherent manipulation of mesoscopic devices
Lucignano, Procolo
2005-01-01
The manipulation of quantum states of solid state coherent devices is the central goal of this thesis. The problems studied concern both the superconductors and the semiconductors physics. They are reported in three chapters; each chapter has its own appendixes, a bibliography, and a detailed discussion in the end, so that the reader could read whatever chapter independently of the others. In what follows I briefly summarize the topics developed in this work describing them as they appear ...
Coherence in electron transfer pathways
Skourtis, Spiros S.; Beratan, David N.; Waldeck, David H.
2011-01-01
Central to the view of electron-transfer reactions is the idea that nuclear motion generates a transition state geometry at which the electron/hole amplitude propagates coherently from the electron donor to the electron acceptor. In the weakly coupled or nonadiabatic regime, the electron amplitude tunnels through an electronic barrier between the donor and acceptor. The structure of the barrier is determined by the covalent and noncovalent interactions of the bridge. Because the tunneling bar...
Coherent states on Hilbert modules
International Nuclear Information System (INIS)
We generalize the concept of coherent states, traditionally defined as special families of vectors on Hilbert spaces, to Hilbert modules. We show that Hilbert modules over C*-algebras are the natural settings for a generalization of coherent states defined on Hilbert spaces. We consider those Hilbert C*-modules which have a natural left action from another C*-algebra, say A. The coherent states are well defined in this case and they behave well with respect to the left action by A. Certain classical objects like the Cuntz algebra are related to specific examples of coherent states. Finally we show that coherent states on modules give rise to a completely positive definite kernel between two C*-algebras, in complete analogy to the Hilbert space situation. Related to this, there is a dilation result for positive operator-valued measures, in the sense of Naimark. A number of examples are worked out to illustrate the theory. Some possible physical applications are also mentioned.
Coherent orthogonal polynomials
International Nuclear Information System (INIS)
We discuss a fundamental characteristic of orthogonal polynomials, like the existence of a Lie algebra behind them, which can be added to their other relevant aspects. At the basis of the complete framework for orthogonal polynomials we include thus–in addition to differential equations, recurrence relations, Hilbert spaces and square integrable functions–Lie algebra theory. We start here from the square integrable functions on the open connected subset of the real line whose bases are related to orthogonal polynomials. All these one-dimensional continuous spaces allow, besides the standard uncountable basis (|x〉), for an alternative countable basis (|n〉). The matrix elements that relate these two bases are essentially the orthogonal polynomials: Hermite polynomials for the line and Laguerre and Legendre polynomials for the half-line and the line interval, respectively. Differential recurrence relations of orthogonal polynomials allow us to realize that they determine an infinite-dimensional irreducible representation of a non-compact Lie algebra, whose second order Casimir C gives rise to the second order differential equation that defines the corresponding family of orthogonal polynomials. Thus, the Weyl–Heisenberg algebra h(1) with C=0 for Hermite polynomials and su(1,1) with C=−1/4 for Laguerre and Legendre polynomials are obtained. Starting from the orthogonal polynomials the Lie algebra is extended both to the whole space of the L2 functions and to the corresponding Universal Enveloping Algebra and transformation group. Generalized coherent states from each vector in the space L2 and, in particular, generalized coherent polynomials are thus obtained. -- Highlights: •Fundamental characteristic of orthogonal polynomials (OP): existence of a Lie algebra. •Differential recurrence relations of OP determine a unitary representation of a non-compact Lie group. •2nd order Casimir originates a 2nd order differential equation that defines the
GÜLER, O.; Roos, C; Terlaky, T.; J.-Ph. Vial
1995-01-01
The literature in the field of interior point methods for Linear Programming has been almost exclusively algorithmic oriented. Very few contributions have been made towards the theory of Linear Programming itself. In particular none of them offer a simple, self-contained introduction to the theory of Linear Programming and linear inequalities. The purpose of this paper is to show that the interior point methodology can be used to introduce the field of Linear Programming. Starting from scratc...
Subramanian Rangan; Metin Sengul
2009-01-01
Reflecting amplified hazards in cross-border exchange and imperfections in markets for intangibles, internalization has been central in multinational enterprise (MNE) theory. This centrality notwithstanding, the fact is that internalization coheres with lower-powered incentives and carries an implicit drawback, namely, higher realized production costs. With the emergence and deployment of information and communication technology (ICT), modern MNEs are reshaping their transnational governance ...
Coherence in Energy Transfer and Photosynthesis
Chenu, Aurélia; Scholes, Gregory D.
2015-04-01
Ultrafast energy transfer is used to transmit electronic excitation among the many molecules in photosynthetic antenna complexes. Recent experiments and theories have highlighted the role of coherent transfer in femtosecond studies of these proteins, suggesting the need for accurate dynamical models to capture the subtle characteristics of energy transfer mechanisms. Here we discuss how to think about coherence in light harvesting and electronic energy transfer. We review the various fundamental concepts of coherence, spanning from classical phenomena to the quantum superposition, and define coherence in electronic energy transfer. We describe the current status of experimental studies on light-harvesting complexes. Insights into the microscopic process are presented to highlight how and why this is a challenging problem to elucidate. We present an overview of the applicable dynamical theories to model energy transfer in the intermediate coupling regime.
Morsanyi, Kinga; Primi, Caterina; Handley, Simon J; Chiesi, Francesca; Galli, Silvia
2012-11-01
In two experiments, we tested some of the central claims of the empathizing-systemizing (E-S) theory. Experiment 1 showed that the systemizing quotient (SQ) was unrelated to performance on a mathematics test, although it was correlated with statistics-related attitudes, self-efficacy, and anxiety. In Experiment 2, systemizing skills, and gender differences in these skills, were more strongly related to spatial thinking styles than to SQ. In fact, when we partialled the effect of spatial thinking styles, SQ was no longer related to systemizing skills. Additionally, there was no relationship between the Autism Spectrum Quotient (AQ) and the SQ, or skills and interest in mathematics and mechanical reasoning. We discuss the implications of our findings for the E-S theory, and for understanding the autistic cognitive profile. PMID:23034108
Organizational closure and conceptual coherence
Scott
2000-01-01
This paper reviews ideas developed by the late Gordon Pask as part of this conversation theory (CT). CT uses theories of the dynamics of complex, self-organizing systems, in conjunction with models of conceptual structures, in order to give an account of conceptual coherence (for example, of a theory or a belief system) as a form of organizational closure. In Pask's own terms, CT is concerned both with the kinematics of knowledge structures and the kinetics of knowing and coming to know. The main features of modelling conceptual structures and processes used by Pask are presented. We continue by presenting a summary two-cycle model of learning, aimed to capture some of Pask's key insights with respect to conceptual coherence and the organizational closure of conceptual systems. Parallels are drawn with other work in epistemology, classic cybernetic studies of self-organization, and the concept of autopoiesis. The two-cycle model is then applied recursively to generate learning cycles and conceptual structures at different levels of abstraction, as a contribution to the work of Pask on the topology of thought. Finally, the model is applied reflexively. That is, its own form is considered as a topic for conversation and conceptualization. Carrying out such a reflection provides a coherent way of characterizing epistemological limits, while retaining a clear sense of there being an (in principle) unlimited praxeology of awareness. PMID:10818581
Gould, Victoria; Hartmann, Miklos; Ruskuc, Nik
2014-01-01
A monoid $S$ is said to be right coherent if every finitely generated subact of every finitely presented right $S$-act is finitely presented. Left coherency is defined dually and $S$ is coherent if it is both right and left coherent. These notions are analogous to those for a ring $R$ (where, of course, $S$-acts are replaced by $R$-modules). Choo, Lam and Luft have shown that free rings are coherent. In this note we prove that, correspondingly, any free monoid is coherent, thus answering a qu...
Coherent States Expectation Values as Semiclassical Trajectories
Dias, N. C.; Mikovic, A.; Prata, J. N.
2005-01-01
We study the time evolution of the expectation value of the anharmonic oscillator coordinate in a coherent state as a toy model for understanding the semiclassical solutions in quantum field theory. By using the deformation quantization techniques, we show that the coherent state expectation value can be expanded in powers of $\\hbar$ such that the zeroth-order term is a classical solution while the first-order correction is given as a phase-space Laplacian acting on the classical solution. Th...
Does left-libertarianism have coherent foundations?
Mathias Risse
2004-01-01
Left-libertarian theories of justice hold that agents are full self-owners and that natural resources are owned in some egalitarian manner. Some philosophers find left-libertarianism promising because it seems that it coherently underwrites both some demands of material equality and some limits on the permissible means of promoting such equality. However, the main goal of this article is to argue that, as far as coherence is concerned, at least one formulation of left-libertarianism is in tro...
Coherence and correspondence in engineering design
Directory of Open Access Journals (Sweden)
Konstantinos V. Katsikopoulos
2009-03-01
Full Text Available I show how the coherence/correspondence distinction can inform the conversation about decision methods for engineering design. Some engineers argue for the application of multi-attribute utility theory while others argue for what they call heuristics. To clarify the differences among methods, I first ask whether each method aims at achieving coherence or correspondence. By analyzing statements in the design literature, I argue that utility theory aims at achieving coherence and heuristics aim at achieving correspondence. Second, I ask if achieving coherence always implies achieving correspondence. It is important to provide an answer because while in design the objective is correspondence, it is difficult to assess it, and coherence that is easier to assess is used as a surrogate. I argue that coherence does not always imply correspondence in design and that this is also the case in problems studied in judgment and decision-making research. Uncovering the conditions under which coherence implies, or does not imply, correspondence is a topic where engineering design and judgment and decision-making research might connect.
Institute of Scientific and Technical Information of China (English)
胡晓明
2007-01-01
The ideological trend of "counter-West centralism" is becomingmore and more obvious in the academic circle of Chinese literary theory fromthe 1980s to the beginning of this century.This article regards a certain numberof phenomena as surveying targets,and analyzes that this ideological trendis embodied not only in evident purposes,slogans and views,but also in there-thinking of education history and in the work of literary material and thereestablishing of criticism history.This article holds that the combination of twokinds of opposed learning trends for study and application respectively would behelpful in breaking through the barriers of single-sided logic,emphasizing nativeliterary tradition,participating in contemporary literature practice and definingChinese literary theory in the 21 st century.
Partially coherent imaging and spatial coherence wavelets
International Nuclear Information System (INIS)
A description of spatially partially coherent imaging based on the propagation of second order spatial coherence wavelets and marginal power spectra (Wigner distribution functions) is presented. In this dynamics, the spatial coherence wavelets will be affected by the system through its elementary transfer function. The consistency of the model with the both extreme cases of full coherent and incoherent imaging was proved. In the last case we obtained the classical concept of optical transfer function as a simple integral of the elementary transfer function. Furthermore, the elementary incoherent response function was introduced as the Fourier transform of the elementary transfer function. It describes the propagation of spatial coherence wavelets form each object point to each image point through a specific point on the pupil planes. The point spread function of the system was obtained by a simple integral of the elementary incoherent response function. (author)
Sandow, M J; Fisher, T J; Howard, C Q; Papas, S
2014-05-01
This study was part of a larger project to develop a (kinetic) theory of carpal motion based on computationally derived isometric constraints. Three-dimensional models were created from computed tomography scans of the wrists of ten normal subjects and carpal spatial relationships at physiological motion extremes were assessed. Specific points on the surface of the various carpal bones and the radius that remained isometric through range of movement were identified. Analysis of the isometric constraints and intercarpal motion suggests that the carpus functions as a stable central column (lunate-capitate-hamate-trapezoid-trapezium) with a supporting lateral column (scaphoid), which behaves as a 'two gear four bar linkage'. The triquetrum functions as an ulnar translation restraint, as well as controlling lunate flexion. The 'trapezoid'-shaped trapezoid places the trapezium anterior to the transverse plane of the radius and ulna, and thus rotates the principal axis of the central column to correspond to that used in the 'dart thrower's motion'. This study presents a forward kinematic analysis of the carpus that provides the basis for the development of a unifying kinetic theory of wrist motion based on isometric constraints and rules-based motion. PMID:24072199
Electron microdiffraction and channeling: Theory and applications
International Nuclear Information System (INIS)
Three related topics in the theory of dynamical kilovolt electron diffraction are treated, and one practical application of the theory is provided. The first topic concerns the theory of coherent electron microdiffraction for atomic clusters and precipitates. The visibility of High Order Laue Zone (HOLZ) lines within the central-beam disk of coherent electron-microdiffraction patterns was studied using dynamical electron-diffraction theory. The electron source size is also shown to affect HOLZ line visibility. Coherent electron-microdiffraction patterns were obtained from a new crystalline precipitate found in silicon wafers annealed at 635 degree C for 256 h. The most likely structure is that of keatite (SiO2, tetragonal). The implications for the study of oxygen precipitation in silicon are discussed. The second theoretical topic concerns the possibilities for determining the sites of adatoms on surfaces by measurements of the x-ray or Auger electron yield as a function of diffraction conditions in the RHEED geometry. Finally, the effects of wave-function dimensionality and inelastic localization on ALCHEMI (Atom Location by Channeling Enhanced Microanalysis) has been studied. The original ALCHEMI equations are shown to hold for certain conditions
Tymoigne, Éric
2014-01-01
One of the main contributions of Modern Money Theory (MMT) has been to explain why monetarily sovereign governments have a very flexible policy space that is unconstrained by hard financial limits. Not only can they issue their own currency to pay public debt denominated in their own currency, but they can also easily bypass any self-imposed constraint on budgetary operations. Through a detailed analysis of the institutions and practices surrounding the fiscal and monetary operations of the t...
On Longitudinal Spectral Coherence
DEFF Research Database (Denmark)
Kristensen, Leif
1979-01-01
It is demonstrated that the longitudinal spectral coherence differs significantly from the transversal spectral coherence in its dependence on displacement and frequency. An expression for the longitudinal coherence is derived and it is shown how the scale of turbulence, the displacement between ...
Coherent and diffractive pion production
International Nuclear Information System (INIS)
Scattering interactions can be classified using two variables which are Lorentz invariant: Q2, negative the square of the four-momentum transferred, and ν, the energy transferred from the leptons to the target in it's rest frame. In weak interactions most regions of the Q2 ν plane have been studied extensively. For one region in particular, the low Q2 high ν region, experimental data has only become available in the last 10 years. Coherent and diffractive pion production occurs in this region and provides tests for low Q2 theories. The majority of data on this reaction has come from large bubble chambers exposed to high energy neutrino beams. Only in the past few years has the potential of counter experiments in neutrino interactions been utilised. This talk focuses on the coherent production of single charged pions in NOMAD, a counter experiment exposed to a νμ beam
Tenth Biennial Coherent Laser Radar Technology and Applications Conference
Kavaya, Michael J. (Compiler)
1999-01-01
The tenth conference on coherent laser radar technology and applications is the latest in a series beginning in 1980 which provides a forum for exchange of information on recent events current status, and future directions of coherent laser radar (or lidar or lader) technology and applications. This conference emphasizes the latest advancement in the coherent laser radar field, including theory, modeling, components, systems, instrumentation, measurements, calibration, data processing techniques, operational uses, and comparisons with other remote sensing technologies.
Coherent dynamics on hierarchical systems
Blumen, Alexander; Bierbaum, Veronika; Mülken, Oliver
2006-11-01
We study the coherent transport modeled by continuous-time quantum walks, focussing on hierarchical structures. For these we use Husimi cacti, lattices dual to the dendrimers. We find that the transport depends strongly on the initial site of the excitation. For systems of sizes N⩽21, we find that processes which start at central sites are nearly recurrent. Furthermore, we compare the classical limiting probability distribution to the long time average of the quantum mechanical transition probability which shows characteristic patterns. We succeed in finding a good lower bound for the (space) average of the quantum mechanical probability to be still or again at the initial site.
Shimony-Wolf states and hidden coherences in classical light
Eberly, J. H.
2015-10-01
The classical theory of polarisation coherence is briefly summarised and then extended. The extension is motivated by the recognition that the traditional theory of two-point coherence provides only what we identify as 'diagonal' correlation functions and their associated two-point coherence matrices. It is pointed out that a wider focus is possible when taking account of the three-sector vector space underlying all two-point coherences in classical optics. This reveals the possibility of observing a new type of 'off-diagonal' correlations that arise when the correlation functions under investigation are associated with points in two distinct vector spaces, pairs of points that are not analogous to the pairs of space points or time points that underlie traditional measures of spatial and temporal coherence. Quantum theory has experience with correlations engaging such 'cross-sector' coherences, for example in tests of Bell inequalities, and the quantum formulations are shown to be easily adopted by classical theory without incorporating quantum features in the optical signals. The familiar theory of classical coherence that is associated with the pioneering work of Emil Wolf is extended in conformance with three criteria advanced by Abner Shimony to obtain formulas for correlation functions and for the Bell measure ? of coherence. Values of ? greater than the standard upper limit ? are predicted for certain classical Shimony-Wolf fields, indicating strong cross-sector coherence, but only when standard measures of coherence such as degree of polarisation ? are minimised. Experimental results confirming the predictions for cross-sector coherence are exhibited.
Multinary systems and reliability models from coherence to some kind of non-coherence
International Nuclear Information System (INIS)
First restricted to models for binary systems, reliability theory is being generalized for multinary systems, of multinary components. After a general viewpoint on reliability models for multinary systems, coherence generalizations are examined. First studied in terms of structure functions, the binary coherent systems can be fully characterized in terms of their minimal path (cut) sets as well as in terms of their life functions. Various fundamental notions such as minimal path (cut) sets and relevance first are introduced in terms of structure functions. The binary decompositions are studied and used for characterizing the broad-sense coherence in terms of sets. The binary-type coherence, the homogenous coherence and the various types of strict-sense coherence are reviewed and fully characterized in various ways. Life functions lead to some model useful for reliability calculations. Methods for determining, in a exact or approximated way, reliability characteristics of multinary coherent systems are studied from both of the fundamental models of reliability, then possible. Futhermore, some kind of non-coherent multinary system is suggested. This analysis may be interesting in the nuclear field
On coherent structure in wall turbulence
Sharma, A S
2013-01-01
A new theory of coherent structure in wall turbulence is presented. The theory is the first to predict packets of hairpin vortices and other structure in turbulence, and their dynamics, based on an analysis of the Navier-Stokes equations, under an assumption of a turbulent mean profile. The assumption of the turbulent mean acts as a restriction on the class of possible structures. It is shown that the coherent structure is a manifestation of essentially low-dimensional flow dynamics, arising from a critical layer mechanism. Using the decomposition presented in McKeon & Sharma (J. Fluid Mech, 658, 2010), complex coherent structure is recreated from minimal superpositions of response modes predicted by the analysis, which take the form of radially-varying travelling waves. By way of example, simple combinations of these modes are offered that predicts hairpins and modulated hairpin packets. The phase interaction also predicts important skewness and correlation results known in the literature. It is also sho...
Application Coherency Manager Project
National Aeronautics and Space Administration — This proposal describes an Application Coherency Manager that implements and manages the interdependencies of simulation, data, and platform information. It will...
Eesley, G L
1981-01-01
Coherent Raman Spectroscopy provides a unified and general account of the fundamental aspects of nonlinear Raman spectroscopy, also known as coherent Raman spectroscopy. The theoretical basis from which coherent Raman spectroscopy developed is described, along with its applications, utility, and implementation as well as advantages and disadvantages. Experimental data which typifies each technique is presented. This book is comprised of four chapters and opens with an overview of nonlinear optics and coherent Raman spectroscopy, followed by a discussion on nonlinear transfer function of matter
On -Coherent Endomorphism Rings
Indian Academy of Sciences (India)
Li-Xin Mao
2008-11-01
A ring is called right -coherent if every principal right ideal is finitely presented. Let $M_R$ be a right -module. We study the -coherence of the endomorphism ring of $M_R$. It is shown that is a right -coherent ring if and only if every endomorphism of $M_R$ has a pseudokernel in add $M_R; S$ is a left -coherent ring if and only if every endomorphism of $M_R$ has a pseudocokernel in add $M_R$. Some applications are given.
Huang, Hung-Jin; Mandelbaum, Rachel; Freeman, Peter E.; Chen, Yen-Chi; Rozo, Eduardo; Rykoff, Eli; Baxter, Eric J.
2016-08-01
The shapes of cluster central galaxies are not randomly oriented, but rather exhibit coherent alignments with the shapes of their parent clusters as well as with the surrounding large-scale structures. In this work, we aim to identify the galaxy and cluster quantities that most strongly predict the central galaxy alignment phenomenon among a large parameter space with a sample of 8237 clusters and 94817 members within 0.1 theories of central galaxy alignments, the impact of primordial alignments with tidal fields, and the importance of anisotropic accretion.
Ordering states with coherence measures
Liu, C. L.; Yu, Xiao-Dong; Xu, G. F.; Tong, D. M.
2016-07-01
The quantification of quantum coherence has attracted a growing attention, and based on various physical contexts, several coherence measures have been put forward. An interesting question is whether these coherence measures give the same ordering when they are used to quantify the coherence of quantum states. In this paper, we consider the two well-known coherence measures, the l_1 norm of coherence and the relative entropy of coherence, to show that there are the states for which the two measures give a different ordering. Our analysis can be extended to other coherence measures, and as an illustration of the extension we further consider the formation of coherence to show that the l_1 norm of coherence and the formation of coherence, as well as the relative entropy of coherence and the coherence of formation, do not give the same ordering too.
Nuclear halo and the coherent nuclear interaction
Alzetta, R.; Liberti, G.; Zaffino, R. L.
2004-01-01
The unusual structure of Li11, the first halo nucleus found, is analyzed by the Preparata model of nuclear structure. By applying Coherent Nucleus Theory, we obtain an interaction potential for the halo-neutrons that rightly reproduces the fundamental state of the system.
Neuronal avalanches and coherence potentials
Plenz, D.
2012-05-01
The mammalian cortex consists of a vast network of weakly interacting excitable cells called neurons. Neurons must synchronize their activities in order to trigger activity in neighboring neurons. Moreover, interactions must be carefully regulated to remain weak (but not too weak) such that cascades of active neuronal groups avoid explosive growth yet allow for activity propagation over long-distances. Such a balance is robustly realized for neuronal avalanches, which are defined as cortical activity cascades that follow precise power laws. In experiments, scale-invariant neuronal avalanche dynamics have been observed during spontaneous cortical activity in isolated preparations in vitro as well as in the ongoing cortical activity of awake animals and in humans. Theory, models, and experiments suggest that neuronal avalanches are the signature of brain function near criticality at which the cortex optimally responds to inputs and maximizes its information capacity. Importantly, avalanche dynamics allow for the emergence of a subset of avalanches, the coherence potentials. They emerge when the synchronization of a local neuronal group exceeds a local threshold, at which the system spawns replicas of the local group activity at distant network sites. The functional importance of coherence potentials will be discussed in the context of propagating structures, such as gliders in balanced cellular automata. Gliders constitute local population dynamics that replicate in space after a finite number of generations and are thought to provide cellular automata with universal computation. Avalanches and coherence potentials are proposed to constitute a modern framework of cortical synchronization dynamics that underlies brain function.
Coherence, Abstraction, and Personal Involvement: Albert Einstein, Physicist and Humanist.
Ne'eman, Yuval
1979-01-01
Reviews Einstein's main contributions to physics, and analyzes the importance of a coherent body of theory. Einstein's involvement in nonscientific issues such as nuclear disarmament is also included. (HM)
Complex sine-Gordon Equation in Coherent Optical Pulse Propagation
Park, Q H
1999-01-01
It is shown that the McCall-Hahn theory of self-induced transparency in coherent optical pulse propagation can be identified with the complex sine-Gordon theory in the sharp line limit. We reformulate the theory in terms of the deformed gauged Wess-Zumino-Witten sigma model and address various new aspects of self-induced transparency.
Stationary quantum coherence and transport in disordered networks
International Nuclear Information System (INIS)
We examine the excitation transport across quantum networks that are continuously driven by a constant and incoherent source. In particular we investigate the coherence properties of incoherently driven networks by employing recent tools from entanglement theory that enable a rigorous interpretation of coherence in the site basis. With these tools at hand we identify coherent delocalization of excitations over several sites to be a crucial prerequisite for highly efficient transport across networks driven by an incoherent source. These results are set into context with the latest discussion of the occurrence of coherence in molecular complexes that are driven by incoherent sun light. (paper)
International Nuclear Information System (INIS)
An experimental study is carried out to investigate the effect of coherence and polarization on the polychromatic partially coherent dark hollow beam (PCDHB). The experimental results show that the spatial coherence and source polarization affect the dark region of the generated hollow beam. The study shows that by varying the source degree of polarization (DOP), we get a tunable dark region. We find that the longer the spatial coherence length of the input beam, the larger the central dark size of the resultant PCDHB. Further, it is shown that polychromatic PCDHB with low spatial coherence travel a longer distance without being distorted than a beam with a high spatial coherence. These kinds of polychromatic beams may find potential application in the field of polychromatic light based free-space optical (FSO) communications. (papers)
Quantum speed limits, coherence, and asymmetry
Marvian, Iman; Spekkens, Robert W.; Zanardi, Paolo
2016-05-01
The resource theory of asymmetry is a framework for classifying and quantifying the symmetry-breaking properties of both states and operations relative to a given symmetry. In the special case where the symmetry is the set of translations generated by a fixed observable, asymmetry can be interpreted as coherence relative to the observable eigenbasis, and the resource theory of asymmetry provides a framework to study this notion of coherence. We here show that this notion of coherence naturally arises in the context of quantum speed limits. Indeed, the very concept of speed of evolution, i.e., the inverse of the minimum time it takes the system to evolve to another (partially) distinguishable state, is a measure of asymmetry relative to the time translations generated by the system Hamiltonian. Furthermore, the celebrated Mandelstam-Tamm and Margolus-Levitin speed limits can be interpreted as upper bounds on this measure of asymmetry by functions which are themselves measures of asymmetry in the special case of pure states. Using measures of asymmetry that are not restricted to pure states, such as the Wigner-Yanase skew information, we obtain extensions of the Mandelstam-Tamm bound which are significantly tighter in the case of mixed states. We also clarify some confusions in the literature about coherence and asymmetry, and show that measures of coherence are a proper subset of measures of asymmetry.
Catalytic coherence transformations
Bu, Kaifeng; Singh, Uttam; Wu, Junde
2016-04-01
Catalytic coherence transformations allow the otherwise impossible state transformations using only incoherent operations with the aid of an auxiliary system with finite coherence that is not being consumed in any way. Here we find the necessary and sufficient conditions for the deterministic and stochastic catalytic coherence transformations between a pair of pure quantum states. In particular, we show that the simultaneous decrease of a family of Rényi entropies of the diagonal parts of the states under consideration is a necessary and sufficient condition for the deterministic catalytic coherence transformations. Similarly, for stochastic catalytic coherence transformations we find the necessary and sufficient conditions for achieving a higher optimal probability of conversion. We thus completely characterize the coherence transformations among pure quantum states under incoherent operations. We give numerous examples to elaborate our results. We also explore the possibility of the same system acting as a catalyst for itself and find that indeed self-catalysis is possible. Further, for the cases where no catalytic coherence transformation is possible we provide entanglement-assisted coherence transformations and find the necessary and sufficient conditions for such transformations.
García-Patrón, Raúl; Pirandola, Stefano; Lloyd, Seth; Shapiro, Jeffrey H.
2009-05-01
In this Letter we define a family of entanglement distribution protocols assisted by feedback classical communication that gives an operational interpretation to reverse coherent information, i.e., the symmetric counterpart of the well-known coherent information. This leads to the definition of a new entanglement distribution capacity that exceeds the unassisted capacity for some interesting channels.
Zheng, Yanping
2009-01-01
In the thesis a coherent text is defined as a continuity of senses of the outcome of combining concepts and relations into a network composed of knowledge space centered around main topics. And the author maintains that in order to obtain the coherence of a target language text from a source text during the process of translation, a translator can…
International Nuclear Information System (INIS)
Properties of the system of generalized coherent states for the simpliest Lie groups are reviewed. Coherent states for the group of rotations of the three-dimensional space SO(3) and the structure of the group are considered. Irreducible unitary representations of the SU(2) group are plotted, as well as a contineous series of concepts of the SU(1, 1) group
García-Patrón, Raúl; Pirandola, Stefano; Lloyd, Seth; Shapiro, Jeffrey H.
2008-01-01
In this letter we define a family of entanglement distribution protocols assisted by feedback classical communication that gives an operational interpretation to reverse coherent information, i.e., the symmetric counterpart of the well known coherent information. This lead to the definition of a new entanglement distribution capacity that exceeds the unassisted capacity for some interesting channels.
Partially coherent ultrafast spectrography
Bourassin-Bouchet, C.; Couprie, M.-E.
2015-01-01
Modern ultrafast metrology relies on the postulate that the pulse to be measured is fully coherent, that is, that it can be completely described by its spectrum and spectral phase. However, synthesizing fully coherent pulses is not always possible in practice, especially in the domain of emerging ultrashort X-ray sources where temporal metrology is strongly needed. Here we demonstrate how frequency-resolved optical gating (FROG), the first and one of the most widespread techniques for pulse characterization, can be adapted to measure partially coherent pulses even down to the attosecond timescale. No modification of experimental apparatuses is required; only the processing of the measurement changes. To do so, we take our inspiration from other branches of physics where partial coherence is routinely dealt with, such as quantum optics and coherent diffractive imaging. This will have important and immediate applications, such as enabling the measurement of X-ray free-electron laser pulses despite timing jitter. PMID:25744080
International Nuclear Information System (INIS)
The Scalable Coherent Interface (IEEE P1596) is establishing an interface standard for very high performance multiprocessors, supporting a cache-coherent-memory model scalable to systems with up to 64K nodes. This Scalable Coherent Interface (SCI) will supply a peak bandwidth per node of 1 GigaByte/second. The SCI standard should facilitate assembly of processor, memory, I/O and bus bridge cards from multiple vendors into massively parallel systems with throughput far above what is possible today. The SCI standard encompasses two levels of interface, a physical level and a logical level. The physical level specifies electrical, mechanical and thermal characteristics of connectors and cards that meet the standard. The logical level describes the address space, data transfer protocols, cache coherence mechanisms, synchronization primitives and error recovery. In this paper we address logical level issues such as packet formats, packet transmission, transaction handshake, flow control, and cache coherence. 11 refs., 10 figs
Field Theory for Coherent Optical Pulse Propagation
Park, Q H
1997-01-01
We introduce a new notion of "matrix potential" to nonlinear optical systems. In terms of a matrix potential $g$, we present a gauge field theoretic formulation of the Maxwell-Bloch equation that provides a semiclassical description of the propagation of optical pulses through resonant multi-level media. We show that the Bloch part of the equation can solved identically through $g$ and the remaining Maxwell equation becomes a second order differential equation with reduced set of variables due to the gauge invariance of the system. Our formulation clarifies the (nonabelian) symmetry structure of the Maxwell-Bloch equations for various multi-level media in association with symmetric spaces $G/H$. In particular, we associate nondegenerate two-level system for self-induced transparency with $G/H=SU(2)/U(1)$ and three-level $\\L $- or V-systems with $G/H = SU(3)/U(2)$. We give a detailed analysis for the two-level case in the matrix potential formalism, and address various new properties of the system including so...
Directory of Open Access Journals (Sweden)
Sven Hassler
2014-12-01
Full Text Available In order to increase the understanding on what determines health among immigrants, ethnic minorities and indigenous people concepts as acculturation, identity and sense of coherence (SOC have become central for the analysis. The process of acculturation and the associated concepts of integration, assimilation, marginalization and separation have often been referred to when describing the health of immigrants and indigenous, of which integration has been considered to provide the better conditions for good health. The aim of this study is to explore the mutual relations between the concepts of acculturation, SOC and identity by an abductive reasoning based on an investigation on a group of Sami regarding their cultural and ethnic self-identification. By this explorative approach the study also seek to touch upon some of the relevant neighboring concepts such as cultural memory and position them among the more established social determinants of health. The study demonstrates that coherence as a psychosocial characteristic is appearing in different concepts and models in the area of acculturation and cognitive development as well as in cultural memory. It has an intra-individual dimension expressed in the theories of cognitive development and cultural memory and inter-individual, social dimension noticeable in SOC and the process of acculturation. The mutual correspondence of these structures of thought, values and perspectives have yet to be clarified and understood, especially in relation to health.
Coherent states and covariant semi-spectral measures
International Nuclear Information System (INIS)
The close connection between Mackey's theory of imprimitivity systems and the so called generalized coherent states introduced by Perelomov is established. Coherent states give a covariant description of the ''localization'' of a quantum system in the phase space in a similar way as the imprimitivity systems give a covariant description of the localization of a quantum system in the configuration space. The observation that for any system of coherent states one can define a covariant semi-spectral measure made possible a rigurous formulation of this idea. A generalization of the notion of coherent states is given. Covariant semi-spectral measures associated with systems of coherent states are defined and characterized. Necessary and sufficient conditions for a unitary representation of a Lie group to be i) a subrepresentation of an induced one and ii) a representation with coherent states are given (author)
Asymptotic coherence of gluons and of q-bosons
Energy Technology Data Exchange (ETDEWEB)
Nelson, C.A.
1993-12-31
In theoretical physics one of the most important aspects of coherent states is that they can often be simply and reliably used to investigate the quantum coherence and correlation properties of new dynamical, quantum field theories. First, this paper reviews the coherent/degenerate state treatment of the infra-red dynamics of perturbative QCD. This based on the asymptotic behavior of the Hamiltonian operator as {vert_bar}t{vert_bar} {yields} {infinity} in the interaction representation. Second, the paper reviews the usage of q-analogue coherent states {vert_bar}z>{sub q} to deduce coherence and uncertainty properties of the q-analogue quantized radiation field in the {vert_bar}z>{sub q} ``classical limit`` where {vert_bar}z{vert_bar} is large. Third, for future applications, a new ``projector`` definition of the usual coherent states and of the squeezed states is reported.
How to quantify coherence: distinguishing speakable and unspeakable notions
Marvian, Iman
2016-01-01
Quantum coherence is a critical resource for many operational tasks. Understanding how to quantify and manipulate it also promises to have applications for a diverse set of problems in theoretical physics. For certain applications, however, one requires coherence between the eigenspaces of specific physical observables, such as energy, angular momentum, or photon number, and it makes a difference which eigenspaces appear in the superposition. For others, there is a preferred set of subspaces relative to which coherence is deemed a resource, but it is irrelevant which of the subspaces appear in the superposition. We term these two types of coherence unspeakable and speakable respectively. We argue that a useful approach to quantifying and characterizing unspeakable coherence is provided by the resource theory of asymmetry when the symmetry group is a group of translations, and we translate a number of prior results on asymmetry into the language of coherence. We also highlight some of the applications of this ...
A covariant approach to the analysis of coherent processes
Karasev, V. P.; Shelepin, L. A.
A general group-theory approach to the study of coherent phenomena in many-particle multilevel systems interacting with boson fields is formulated on the basis of the dynamic symmetry theory and the formalism of group representations. Algebraic models of the systems under study are proposed using this approach which yield generalized Dicke models with allowance for both radiation and collisional processes and also consider systems with a varying number of particles. By using Glauber coherent states and generalized coherent states of SU (n) groups, covariant methods are developed for calculating various characteristics of cooperative phenomena and processes on the basis of the models proposed here.
Coherent dynamics in semiconductors
DEFF Research Database (Denmark)
Hvam, Jørn Märcher
1998-01-01
Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... enhanced in quantum confined lower-dimensional systems, where exciton and biexciton effects dominate the spectra even at room temperature. The coherent dynamics of excitons are at modest densities well described by the optical Bloch equations and a number of the dynamical effects known from atomic and...... as a tool to study the coherent exciton dynamics, and the importance of performing transform limited spectroscopy is demonstrated throughout....
Coherent diffractive ρ production
International Nuclear Information System (INIS)
Coherent diffractive ρ production by neutrinos occurs at low four-momentum transfer and high energy transfer. These interactions are generally understood to occur via the coupling of the weak charged current to the vector meson, which scatters diffractively from the target nucleus. Since coherent events are those in which the nucleus interacts as a whole, ie without breakup, and with small recoil energy, these events have a very sharp |t|-distribution. This presentation deals mostly with the Monte Carlo simulation of the coherent diffractive production of the ρ production and in particular with the reconstruction algorithm (description and efficiency) and the |t| distribution
Institute of Scientific and Technical Information of China (English)
Michael Thomas
2005-01-01
@@ What makes a coherent EFL curriculum? How can curriculum planners avoid a mismatch between policy and pragmatics to produce an effective decision-making process? In The Second Language Curriculum, Johnson describes the coherent curriculum as one in which decision outcomes from the various stages of development are mutually consistent and complementary,and learning outcomes reflect curriculum aims.The achievement of coherence is said to depend crucially in most educational contexts upon the formalisation of decision-making processes and products. This formalisation facilitates consensus among those involved and is a prerequisite for effective evaluation and subsequent renewal (1994: xiii)
Coherent state description of extended objects
International Nuclear Information System (INIS)
A convenient method of describing an extended object in quantum field theory, which is regarded as a hadron, is presented. We describe the extended object by a coherent state and treat it on the basis of a variational approximation. The stability and orthogonality problems which are crucial in any attempt to render a physical significance to such a coherent state are investigated. From the stability condition, it is shown that only the models which induce the spontaneous breakdown of symmetry have a stable coherent state. We also show that several topological conservation laws can be understood as a reflection of the orthogonality properties of the Hilbert space. As simple examples, we discuss a self-coupled neutral scalar model, a charged scalar model, the Higgs model and the O(3) iso-triplet scalar model. (auth.)
Coherence in Industrial Transformation
DEFF Research Database (Denmark)
Jørgensen, Ulrik; Lauridsen, Erik Hagelskjær
2003-01-01
The notion of coherence is used to illustrate the general finding, that the impact of environmental management systems and environmental policy is highly dependent of the context and interrelatedness of the systems, procedures and regimes established in society....
Bromley, Thomas R; Adesso, Gerardo
2014-01-01
We analyse under which dynamical conditions the coherence of an open quantum system is totally unaffected by noise. For a single qubit, specific measures of coherence are found to freeze under different conditions, with no general agreement between them. Conversely, for an N-qubit system with even N, we identify universal conditions in terms of initial states and local incoherent channels such that all bona fide distance-based coherence monotones are left invariant during the entire evolution. This finding also provides an insightful physical interpretation for the freezing phenomenon of quantum correlations beyond entanglement. We further obtain analytical results for distance-based measures of coherence in two-qubit states with maximally mixed marginals.
... Cardiac Magnetic Resonance Imaging (MRI and MRA) Computed Tomography (CT) Scan Diagnostic Tests and Procedures Echocardiography Electrocardiogram ... Ultrasound Nuclear Stress Test Nuclear Ventriculography Positron Emission Tomography (PET) Stress ... Optical Coherence Tomography | ...
Thomson, D. J.; Maclennan, C. G.; Lanzerotti, L. J.
2006-12-01
The EPAM charged particle instrument on ACE is the backup for the HISCALE instrument on Ulysses making the two ideally suited for spatial coherence studies over large heliosphere distances. Fluxes of low-energy ( ~50 - 200 keV) electrons are detected in eight spatial sectors on both spacecraft. A spherical harmonic description of the particle flux as a function of time using only the l=0 and l=1 degree coefficients describes most of the observed flux. Here we concentrate on the three l=1 coefficients for the 60--100 kev electrons.Between the two spacecraft these result in nine coherence estimates that are all typically moderately coherent, but the fact that the different coefficients at each spacecraft are also coherent with each other makes interpretation difficult. To avoid this difficulty we estimated the canonical coherences between the two groups of three series. This, in effect, chooses an optimum coordinate system at each spacecraft and for each frequency and estimates the coherence in this frame. Using one--minute data, we find that the canonical coherences are generally larger at high frequencies (3 mHz and above) than they are at low frequencies. This appears to be generally true and does not depend particularly on time, range, etc. However, if the data segment is chosen too long, say > 30 days with 1--minute sampling, the coherence at high frequencies drops. This may be because the spatial and temporal features of the mode are confounded, or possibly because the solar modes p--modes are known to change frequency with solar activity, so do not appear coherent on long blocks.The coherences are not smooth functions of frequency, but have a bimodal distribution particularly in the 100 μHz to 5 mHz range. Classifying the data at frequencies where the canonical coherences are high in terms of apparent polarization and orientation, we note two major families of modes that appear to be organized by the Parker spiral. The magnetic field data on the two
Partially coherent ultrafast spectrography
Bourassin-Bouchet, C.; Couprie, M.-E.
2015-01-01
Modern ultrafast metrology relies on the postulate that the pulse to be measured is fully coherent, that is, that it can be completely described by its spectrum and spectral phase. However, synthesizing fully coherent pulses is not always possible in practice, especially in the domain of emerging ultrashort X-ray sources where temporal metrology is strongly needed. Here we demonstrate how frequency-resolved optical gating (FROG), the first and one of the most widespread techniques for pulse c...
International Nuclear Information System (INIS)
We have carried out high-resolution single-pulse coherent diffractive imaging at the FLASH free-electron laser. The intense focused FEL pulse gives a high-resolution low-noise coherent diffraction pattern of an object before that object turns into a plasma and explodes. In particular we are developing imaging of biological specimens beyond conventional radiation damage resolution limits, developing imaging of ultrafast processes, and testing methods to characterize and perform single-particle imaging.
Spohn, Wolfgang
1999-01-01
The paper proposes two principles of coherence (thus taking up work started in Spohn (1991) "A Reason for Explanation: Explanations Provide Stable Reasons"). The latter indeed serves as a weak, but precise explication of the notion of coherence as it is used in the current epistemological discussion. After discussing their epistemological setting, the paper considers four ways of establishing these principles. They may be inferred neither from enumerative induction, nor from the nature of pro...
A J Seeds; Fice, M. J.; Balakier, K; M Natrella; Mitrofanov, O.; Pepper, M.; Renaud, C.C.; M. Lamponi; M Chtioui; Van Dijk, F.; Aeppli, G.; A G Davies; Dean, P.; Linfield, E
2013-01-01
We present a review of recent developments in THz coherent systems based on photonic local oscillators. We show that such techniques can enable the creation of highly coherent, thus highly sensitive, systems for frequencies ranging from 100 GHz to 5 THz, within an energy efficient integrated platform. We suggest that such systems could enable the THz spectrum to realize its full applications potential. To demonstrate how photonics-enabled THz systems can be realized, we review the performance...
Yanping Zheng
2009-01-01
In the thesis a coherent text is defined as a continuity of senses of the outcome of combining concepts and relations into a network composed of knowledge space centered around main topics. And the author maintains that in order to obtain the coherence of a target language text from a source text during the process of translation, a translator can utilize the following approaches: retention of the continuity of senses of a text; reconstruction of the target text for the purpose of continuity;...
Saorín, Manuel
2016-01-01
We show that, under particular conditions, if a t-structure in the unbounded derived category of a locally coherent Grothendieck category restricts to the bounded derived category of its category of finitely presented objects, then its heart is itself a locally coherent Grothendieck category. Those particular conditions are always satisfied when the Grothendieck category is arbitrary and one considers the t-structure associated to a torsion pair in the category of finitely presented objects. ...
Coherence vortices of partially coherent beams in the far field
Institute of Scientific and Technical Information of China (English)
Liu Pu-Sheng; Lü Bai-da
2007-01-01
Based on the propagation law of cross-spectral density function, studied in this paper are the coherence vortices of partially coherent, quasi-monochromatic singular beams with Gaussian envelope and Schell-model correlator in the far field, where our main attention is paid to the evolution of far-field coherence vortices into intensity vortices of fully coherent beams. The results show that, although there are usually no zeros of intensity in partially coherent beams with Gaussian envelope and Schell-model correlator, zeros of spectral degree of coherence exist. The coherence vortices of spectral degree of coherence depend on the relative coherence length, mode index and positions of pairs of points.If a point and mode index are kept fixed, the position of coherence vortices changes with the increase of the relative coherence length. For the low coherent case there is a circular phase dislocation. In the coherent limit coherence vortices become intensity vortices of fully coherent Laguerre-Gaussian beams.
Central Serous Chorioretinopathy after Solar Eclipse Viewing
Allie Lee; Timothy Lai
2010-01-01
Purpose: To report a case of central serous chorioretinopathy after solar eclipse viewing. Case Report: A middle-age man developed a sudden-onset unilateral scotoma after viewing a partial solar eclipse in Hong Kong. Fundus examination, fluorescein angiography, and optical coherence tomography showed features compatible with central serous chorioretinopathy. The patient was managed conservatively and reevaluated periodically. Serial optical coherence tomographic evaluations demonstrated a...
Preparing attosecond coherences by strong-field ionization
Pabst, Stefan; Lein, Manfred; Wörner, Hans Jakob
2016-01-01
Strong-field ionization (SFI) has been shown to prepare wave packets with few-femtosecond periods. Here, we explore whether this technique can be extended to the attosecond time scale. We introduce an intuitive model, which is based on the Fourier transform of the subcycle SFI rate, for predicting the bandwidth of ionic states that can be coherently prepared by SFI. The coherent bandwidth decreases considerably with increasing central wavelength of the ionizing pulse but it is much less sensi...
Transfer information remotely via noise entangled coherent channels
Allati, A El; Hassouni, Y
2010-01-01
In this contribution, a generalized protocol of quantum teleportation is suggested to investigate the possibility of remotely transfer unknown multiparities entangled coherent state. A theoretical technique is introduced to generate maximum entangled coherent states which are used as quantum channels. We show that the mean photon number plays a central role on the fidelity of the transferred information. The noise parameter can be considered as a control parameter only for small values of the mean photon number.
Stimulated coherent transition radiation
International Nuclear Information System (INIS)
Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed
Benatti, Fabio; Floreanini, Roberto; Scholes, Greg
2012-08-01
The last years have witnessed fast growing developments in the use of quantum mechanics in technology-oriented and information-related fields, especially in metrology, in the developments of nano-devices and in understanding highly efficient transport processes. The consequent theoretical and experimental outcomes are now driving new experimental tests of quantum mechanical effects with unprecedented accuracies that carry with themselves the concrete possibility of novel technological spin-offs. Indeed, the manifold advances in quantum optics, atom and ion manipulations, spintronics and nano-technologies are allowing direct experimental verifications of new ideas and their applications to a large variety of fields. All of these activities have revitalized interest in quantum mechanics and created a unique framework in which theoretical and experimental physics have become fruitfully tangled with information theory, computer, material and life sciences. This special issue aims to provide an overview of what is currently being pursued in the field and of what kind of theoretical reference frame is being developed together with the experimental and theoretical results. It consists of three sections: 1. Memory effects in quantum dynamics and quantum channels 2. Driven open quantum systems 3. Experiments concerning quantum coherence and/or decoherence The first two sections are theoretical and concerned with open quantum systems. In all of the above mentioned topics, the presence of an external environment needs to be taken into account, possibly in the presence of external controls and/or forcing, leading to driven open quantum systems. The open system paradigm has proven to be central in the analysis and understanding of many basic issues of quantum mechanics, such as the measurement problem, quantum communication and coherence, as well as for an ever growing number of applications. The theory is, however, well-settled only when the so-called Markovian or memoryless
Enhanced delegated computing using coherence
Barz, Stefanie; Dunjko, Vedran; Schlederer, Florian; Moore, Merritt; Kashefi, Elham; Walmsley, Ian A.
2016-03-01
A longstanding question is whether it is possible to delegate computational tasks securely—such that neither the computation nor the data is revealed to the server. Recently, both a classical and a quantum solution to this problem were found [C. Gentry, in Proceedings of the 41st Annual ACM Symposium on the Theory of Computing (Association for Computing Machinery, New York, 2009), pp. 167-178; A. Broadbent, J. Fitzsimons, and E. Kashefi, in Proceedings of the 50th Annual Symposium on Foundations of Computer Science (IEEE Computer Society, Los Alamitos, CA, 2009), pp. 517-526]. Here, we study the first step towards the interplay between classical and quantum approaches and show how coherence can be used as a tool for secure delegated classical computation. We show that a client with limited computational capacity—restricted to an XOR gate—can perform universal classical computation by manipulating information carriers that may occupy superpositions of two states. Using single photonic qubits or coherent light, we experimentally implement secure delegated classical computations between an independent client and a server, which are installed in two different laboratories and separated by 50 m . The server has access to the light sources and measurement devices, whereas the client may use only a restricted set of passive optical devices to manipulate the information-carrying light beams. Thus, our work highlights how minimal quantum and classical resources can be combined and exploited for classical computing.
Coherent topological phenomena in protein folding
DEFF Research Database (Denmark)
Bohr, Henrik; Brunak, Søren; Bohr, Jakob
1997-01-01
A theory is presented for coherent topological phenomena in protein dynamics with implications for protein folding and stability. We discuss the relationship to the writhing number used in knot diagrams of DNA. The winding state defines a long-range order along the backbone of a protein with long......-range excitations, `wring' modes, that play an important role in protein denaturation and stability. Energy can be pumped into these excitations, either thermally or by an external force.......A theory is presented for coherent topological phenomena in protein dynamics with implications for protein folding and stability. We discuss the relationship to the writhing number used in knot diagrams of DNA. The winding state defines a long-range order along the backbone of a protein with long...
SAR image effects on coherence and coherence estimation.
Energy Technology Data Exchange (ETDEWEB)
Bickel, Douglas Lloyd
2014-01-01
Radar coherence is an important concept for imaging radar systems such as synthetic aperture radar (SAR). This document quantifies some of the effects in SAR which modify the coherence. Although these effects can disrupt the coherence within a single SAR image, this report will focus on the coherence between separate images, such as for coherent change detection (CCD) processing. There have been other presentations on aspects of this material in the past. The intent of this report is to bring various issues that affect the coherence together in a single report to support radar engineers in making decisions about these matters.
Coherent Photoproduction from Nuclei
Frankfurt, L L; Zhalov, M B
2003-01-01
We argue that study of the cross section of coherent photo(electro) production of vector mesons off nuclear targets provides an effective method to probe the leading twist hard QCD regimes of color transparency and perturbative color opacity as well as the onset of black body limit (BBL) in the soft and hard QCD interactions. In the case of intermediate energies we use the Generalized Vector Dominance Model to take into account coherence effects for two distinctive limits - the soft interactions for production of $\\rho$ and $\\rho'$-mesons and the color transparency regime for production of charmonium states. We demonstrate that GVDM describes very well $\\rho$-meson coherent photoproduction at $6 \\leq E_{\\gamma} \\leq 10$ GeV and predict an oscillating energy dependence for the coherent charmonium production. In the limit of small $x$ we find that hard QCD leads to onset of the perturbative color opacity even for production of very small onium states, like $\\Upsilon$. The advantages of the process of coherent d...
Optical forces on small particles from partially coherent light
Auñón, Juan Miguel
2012-01-01
We put forward a theory on the optical force exerted upon a dipolar particle by a stationary and ergodic partially coherent light ?eld. We show through a rigorous analysis that the ensemble averaged electromagnetic force is given in terms of a partial gradient of the space variable diagonal elements of the coherence tensor. Further, by following this result we characterize the conservative and non-conservative components of this force. In addition, we establish the propagation law for the optical force in terms of the coherence function of light at a di?raction plane. This permits us to evaluate the e?ect of the degree of coherence on the force components by using the archetypical con?guration of Young's two apertures di?raction pattern, so often employed to characterize coherence of waves.
Coherent and incoherent nonparaxial self-accelerating Weber beams
Zhang, Yiqi; Wen, Feng; Li, Changbiao; Zhang, Zhaoyang; Zhang, Yanpeng; Belić, Milivoj R
2016-01-01
We investigate the coherent and incoherent nonparaxial Weber beams, theoretically and numerically. We show that the superposition of coherent self-accelerating Weber beams with transverse displacement cannot display the nonparaxial accelerating Talbot effect. The reason is that their lobes do not accelerate in unison, which is a requirement for the appearance of the effect. While for the incoherent Weber beams, they naturally cannot display the accelerating Talbot effect but can display the nonparaxial accelerating properties, although the transverse coherence length is smaller than the beam width, based on the second-order coherence theory. Our research method directly applies to the nonparaxial Mathieu beams as well, and one will obtain similar conclusions as for the Weber beams, although this is not discussed in the paper. Our investigation identifies families of nonparaxial accelerating beams that do not exhibit the accelerating Talbot effect, and in addition broadens the understanding of coherence proper...
Cox, David A
2012-01-01
Praise for the First Edition ". . .will certainly fascinate anyone interested in abstract algebra: a remarkable book!"—Monatshefte fur Mathematik Galois theory is one of the most established topics in mathematics, with historical roots that led to the development of many central concepts in modern algebra, including groups and fields. Covering classic applications of the theory, such as solvability by radicals, geometric constructions, and finite fields, Galois Theory, Second Edition delves into novel topics like Abel’s theory of Abelian equations, casus irreducibili, and the Galo
Jardine, John F
2015-01-01
This monograph on the homotopy theory of topologized diagrams of spaces and spectra gives an expert account of a subject at the foundation of motivic homotopy theory and the theory of topological modular forms in stable homotopy theory. Beginning with an introduction to the homotopy theory of simplicial sets and topos theory, the book covers core topics such as the unstable homotopy theory of simplicial presheaves and sheaves, localized theories, cocycles, descent theory, non-abelian cohomology, stacks, and local stable homotopy theory. A detailed treatment of the formalism of the subject is interwoven with explanations of the motivation, development, and nuances of ideas and results. The coherence of the abstract theory is elucidated through the use of widely applicable tools, such as Barr's theorem on Boolean localization, model structures on the category of simplicial presheaves on a site, and cocycle categories. A wealth of concrete examples convey the vitality and importance of the subject in topology, n...
Coherent topological phenomena in protein folding
DEFF Research Database (Denmark)
Bohr, Henrik; Brunak, Søren; Bohr, Jakob
1997-01-01
A theory is presented for coherent topological phenomena in protein dynamics with implications for protein folding and stability. We discuss the relationship to the writhing number used in knot diagrams of DNA. The winding state defines a long-range order along the backbone of a protein with long......-range excitations, `wring' modes, that play an important role in protein denaturation and stability. Energy can be pumped into these excitations, either thermally or by an external force....
Quantum Coherence in Photosynthesis for Efficient Solar Energy Conversion
Romero, Elisabet; Augulis, Ramunas; Novoderezhkin, Vladimir I.; Ferretti, Marco; Thieme, Jos; Zigmantas, Donatas; van Grondelle, Rienk
2014-01-01
The crucial step in the conversion of solar to chemical energy in Photosynthesis takes place in the reaction center where the absorbed excitation energy is converted into a stable charge separated state by ultrafast electron transfer events. However, the fundamental mechanism responsible for the near unity quantum efficiency of this process is unknown. Here we elucidate the role of coherence in determining the efficiency of charge separation in the plant photosystem II reaction centre (PSII RC) by comprehensively combining experiment (two-dimensional electronic spectroscopy) and theory (Redfield theory). We reveal the presence of electronic coherence between excitons as well as between exciton and charge transfer states which we argue to be maintained by vibrational modes. Furthermore, we present evidence for the strong correlation between the degree of electronic coherence and efficient and ultrafast charge separation. We propose that this coherent mechanism will inspire the development of new energy technologies. PMID:26870153
Dynamic coherent backscattering mirror
Energy Technology Data Exchange (ETDEWEB)
Zeylikovich, I.; Xu, M., E-mail: mxu@fairfield.edu [Physics Department, Fairfield University, Fairfield, CT 06824 (United States)
2016-02-15
The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.
Maximal privacy without coherence.
Leung, Debbie; Li, Ke; Smith, Graeme; Smolin, John A
2014-07-18
Privacy is a fundamental feature of quantum mechanics. A coherently transmitted quantum state is inherently private. Remarkably, coherent quantum communication is not a prerequisite for privacy: there are quantum channels that are too noisy to transmit any quantum information reliably that can nevertheless send private classical information. Here, we ask how much private classical information a channel can transmit if it has little quantum capacity. We present a class of channels N(d) with input dimension d(2), quantum capacity Q(N(d)) ≤ 1, and private capacity P(N(d)) = log d. These channels asymptotically saturate an interesting inequality P(N) ≤ (1/2)[log d(A) + Q(N)] for any channel N with input dimension d(A) and capture the essence of privacy stripped of the confounding influence of coherence. PMID:25083622
DEFF Research Database (Denmark)
Carroll, Joseph; Clasen, Mathias; Jonsson, Emelie;
2015-01-01
Biocultural theory is an integrative research program designed to investigate the causal interactions between biological adaptations and cultural constructions. From the biocultural perspective, cultural processes are rooted in the biological necessities of the human life cycle: specifically human...... ideological beliefs, and artistic practices such as music, dance, painting, and storytelling. Establishing biocultural theory as a program that self-consciously encompasses the different particular forms of human evolutionary research could help scholars and scientists envision their own specialized areas of...... research as contributions to a coherent, collective research program. This article argues that a mature biocultural paradigm needs to be informed by at least 7 major research clusters: (a) gene-culture coevolution; (b) human life history theory; (c) evolutionary social psychology; (d) anthropological...
Maintaining Web Cache Coherency
Directory of Open Access Journals (Sweden)
2000-01-01
Full Text Available Document coherency is a challenging problem for Web caching. Once the documents are cached throughout the Internet, it is often difficult to keep them coherent with the origin document without generating a new traffic that could increase the traffic on the international backbone and overload the popular servers. Several solutions have been proposed to solve this problem, among them two categories have been widely discussed: the strong document coherency and the weak document coherency. The cost and the efficiency of the two categories are still a controversial issue, while in some studies the strong coherency is far too expensive to be used in the Web context, in other studies it could be maintained at a low cost. The accuracy of these analysis is depending very much on how the document updating process is approximated. In this study, we compare some of the coherence methods proposed for Web caching. Among other points, we study the side effects of these methods on the Internet traffic. The ultimate goal is to study the cache behavior under several conditions, which will cover some of the factors that play an important role in the Web cache performance evaluation and quantify their impact on the simulation accuracy. The results presented in this study show indeed some differences in the outcome of the simulation of a Web cache depending on the workload being used, and the probability distribution used to approximate updates on the cached documents. Each experiment shows two case studies that outline the impact of the considered parameter on the performance of the cache.
Coherent soliton communication lines
Energy Technology Data Exchange (ETDEWEB)
Yushko, O. V., E-mail: olesya.yushko@gmail.com; Redyuk, A. A.; Fedoruk, M. P.; Turitsyn, S. K. [Novosibirsk State University (Russian Federation)
2014-11-15
The data transmission in coherent fiber-optical communication lines using solitons with a variable phase is studied. It is shown that nonlinear coherent structures (solitons) can be applied for effective signal transmission over a long distance using amplitude and optical-phase keying of information. The optimum ratio of the pulse width to the bit slot at which the spectral efficiency (transmitted bits per second and hertz) is maximal is determined. It is shown that soliton fiber-optical communication lines can ensure data transmission at a higher spectral efficiency as compared to traditional communication lines and at a high signal-to-noise ratio.
International Nuclear Information System (INIS)
Recollections are reported about the attitude of N.G. Basov to the problem of coherence of stimulated transitions at the very beginning of studies devoted the creation of masers and lasers. It is shown that the problem of coherence of stimulated transitions can be solved in a multiparticle system. The role of stimulated transitions in a variety of processes proceeding in the nature is discussed. The contribution of N.G. Basov and his school to the development of quantum electronics and laser physics is briefly discussed. (special issue devoted to the 80th anniversary of academician n g basov's birth)
Ferraro, Pietro; Zalevsky, Zeev
2011-01-01
This book deals with the latest achievements in the field of optical coherent microscopy. While many other books exist on microscopy and imaging, this book provides a unique resource dedicated solely to this subject. Similarly, many books describe applications of holography, interferometry and speckle to metrology but do not focus on their use for microscopy. The coherent light microscopy reference provided here does not focus on the experimental mechanics of such techniques but instead is meant to provide a users manual to illustrate the strengths and capabilities of developing techniques. Th
Cherny, Alexander S.
2006-01-01
This paper deals with applications of coherent risk measures to pricing in incomplete markets. Namely, we study the No Good Deals pricing technique based on coherent risk. Two forms of this technique are presented: one defines a good deal as a trade with negative risk; the other one defines a good deal as a trade with unusually high RAROC. For each technique, the fundamental theorem of asset pricing and the form of the fair price interval are presented. The model considered includes static as...
Atomic Coherent Trapping and Properties of Trapped Atom
Institute of Scientific and Technical Information of China (English)
YANG Guo-Jian; XIA Li-Xin; XIE Min
2006-01-01
Based on the theory of velocity-selective coherent population trapping, we investigate an atom-laser system where a pair of counterpropagating laser fields interact with a three-level atom. The influence of the parametric condition on the properties of the system such as velocity at which the atom is selected to be trapped, time needed for finishing the coherent trapping process, and possible electromagnetically induced transparency of an altrocold atomic medium,etc., is studied.
Coherent polarization radiation from crystals irradiated with relativistic charged particles
International Nuclear Information System (INIS)
When polarization radiation (polarization bremsstrahlung) occurs in a crystal, the radiation becomes coherent in X-ray wavelengths. This radiation, called coherent polarization radiation (CPR) in this paper, is considered as a possible compact X-ray source because CPR is intense, monochromatic, tunable, small background, and easy to extract. We present a simple theory of CPR with emphasis on its relation to Cherenkov radiation and transition radiation. Various properties of CPR are also discussed
Higher order coherence of exciton-polariton condensates
Horikiri, Tomoyuki; Schwendimann, Paolo; Quattropani, Antonio; Hofling, Sven; Forchel, Alfred; Yamamoto, Yoshihisa
2009-01-01
The second and third order coherence functions $g^{(n)}(0) (n=2 {\\rm and} 3)$ of an exciton-polariton condensate is measured and compared to the theory. Contrary to an ideal photon laser, deviation from unity in the second and third order coherence functions is observed, thus showing a bunching effect, but not the characteristics of a standard thermal state with $g^{(n)}(0)=n!$. The increase of bunching with the order of the coherence function, $g^{(3)}(0) > g^{(2)}(0)>1$, indicates that the ...
Spectral coherence along a lidar-anemometer beam
Energy Technology Data Exchange (ETDEWEB)
Kristensen, Leif; Kirkegaard, P.; Mann, J.; Mikkelsen, Torben; Nielsen, Morten; Sjoeholm, M.
2010-10-15
The theory of measuring the spectral coherence by means of a lidar anemometer has been outlined. It is based on the assumption that the turbulent velocity field can be considered statistically locally isotropic and on the validity of Taylor's hypothesis. This implies that the longitudinal coherence cannot be predicted realistically. Special emphasis has been placed on the effect of line average along the beam. One section has been devoted to the effect of spectral aliasing, which may cause severe problems in the interpretation of measured data. This work is considered the theoretical background for the understanding of the coherences calculated on basis of real date. (Author)
General framework for quantum macroscopicity in terms of coherence
Yadin, Benjamin; Vedral, Vlatko
2016-02-01
We propose a universal language to assess macroscopic quantumness in terms of coherence, with a set of conditions that should be satisfied by any measure of macroscopic coherence. We link the framework to the resource theory of asymmetry. We show that the quantum Fisher information gives a good measure of macroscopic coherence, enabling a rigorous justification of a previously proposed measure of macroscopicity. This picture lets us draw connections between different measures of macroscopicity and evaluate them; we show that another widely studied measure fails one of our criteria.
Coherence Constraints and the Last Hidden Optical Coherence
Qian, Xiao-Feng; Malhotra, Tanya; Vamivakas, A. Nick; Eberly, Joseph H.
2016-01-01
We have discovered a new domain of optical coherence, and show that it is the third and last member of a previously unreported fundamental triad of coherences. These are unified by our derivation of a parallel triad of coherence constraints that take the form of complementarity relations. We have been able to enter this new coherence domain experimentally and we describe the novel tomographic approach devised for that purpose.
On Discourse Coherence of The Dumb Waiter from the Perspective of the Principle of Goal
Institute of Scientific and Technical Information of China (English)
马文
2012-01-01
The principle of goal is a new theory which can be used to analyze discourse coherence.However,so far,none of the previous scholars has ever used this principle to analyze the coherence of dialogues in drama.Therefore,this essay will try to analyze the dialogue coherence in Harold Pinter's The Dumb Waiter by the principle of goal in order to reveal the implication and themes underneath the coherent or incoherent dialogues,and present the significance of discourse coherence and incoherence in literary discourse which are quite different from court discourse.
Evolution properties of partially coherent flat-topped vortex hollow beam in oceanic turbulence.
Liu, Dajun; Wang, Yaochuan; Yin, Hongming
2015-12-10
Employing the theory of coherence, the partially coherent flat-topped vortex hollow beam is first introduced. The analytical propagation equation for a partially coherent flat-topped vortex hollow beam in oceanic turbulence is derived by using the extended Huygens-Fresnel diffraction integral and the spectrum of oceanic turbulence. The influences of coherence length, beam order N, the topological charge M, and the parameters of oceanic turbulence on evolution properties of partially coherent flat-topped vortex hollow beams propagating in oceanic turbulence are obtained by using the numerical examples. PMID:26836879
Deformation of coherent structures
Fledderus, E.R.; Groesen, van E.
1996-01-01
In this review we investigate the mathematical description of the distortion of clearly recognisable structures in phenomenological physics. The coherent structures we will explicitly deal with are surface waves on a layer of fluid, kink transitions in magnetic material, plane vortices, swirling flo
DEFF Research Database (Denmark)
Andersen, Anne Bendix; Frederiksen, Kirsten; Beedholm, Kirsten;
2016-01-01
During the past decade, politicians and health care providers have strived to create a coherent health care system across primary and secondary health care systems in Denmark. Nevertheless, elderly patients with chronic diseases (EPCD) continue to report experiences of poor-quality care and lack ...
Measuring a coherent superposition
Vitanov, N V; Unanyan, R G; Bergmann, K
1999-01-01
We propose a simple method for measuring the populations and the relative phase in a coherent superposition of two atomic states. The method is based on coupling the two states to a third common (excited) state by means of two laser pulses, and measuring the total fluorescence from the third state for several choices of the excitation pulses.
Hobson, R. Peter
2014-01-01
There is a growing body of opinion that we should view autism as fractionable into different, largely independent sets of clinical features. The alternative view is that autism is a coherent syndrome in which principal features of the disorder stand in intimate developmental relationship with each other. Studies of congenitally blind children…
Coherence in multilevel systems
International Nuclear Information System (INIS)
Mathematical descriptions of an excited state multilevel system are developed to include progressively the effects of coherent coupling, feeding, decay and relaxation, and the expressions are illustrated with several pulse coherence experiments utilizing zero field optically detected magnetic resonance of excited triplet states. A new method is described in which the time development of the coherent components in a multilevel system is monitored by using an observable that can measure only relative populations between the levels. The method is illustrated. By treating a coherently driven excited state system as two levels in contact with a population reservoir, exact expressions are obtained for both transient and steady-state behavior in the presence of transverse and spin lattice relaxation, constant incoherent pumping, spontaneous emission between the two levels, and also decay back into the reservoir. The general mathematical development is applied specifically to zero field microwave phosphorescence double resonance. Experimental methods and apparatus are discussed in detail and results of optically detected transient mutations, spin echoes, and Fourier transform spectroscopy are presented. (26 figs, 220 refs)
Coherent detection spectroscopy
Bueren, H.G. van
1969-01-01
Various methods of optical spectroscopy are compared, with special emphasis on resolution and acceptance of the systems. It is shown that coherent detection with a laser as a local oscillator has important advantages for specific applications in astronomical spectroscopy and interferometry, especial
DEFF Research Database (Denmark)
Mogensen, Mette; Themstrup, Lotte; Banzhaf, Christina;
2014-01-01
Optical coherence tomography (OCT) has developed rapidly since its first realisation in medicine and is currently an emerging technology in the diagnosis of skin disease. OCT is an interferometric technique that detects reflected and backscattered light from tissue and is often described as the...
Institute of Scientific and Technical Information of China (English)
王雪玲
2014-01-01
Cohesion and coherence in discourse analysis are two important terms .This article is mainly built on the basis of previous research on discourse analysis and translation ,and makes an exploratory study on cohesion and co-herence in translating classical poetry by comparing different versions of the same poem from the perspective of dis -course analysis .The main purpose is to learn how to grasp the discourse as a whole ,clarifying the inherent logic in the classical poetry ,the proper use of various cohesive devices to maintain the natural and coherent translation .%衔接和连贯是语篇分析中的两个重要术语。文章主要以前人对语篇分析与翻译的研究为基础，通过对比李白《送友人》的不同译本，从语篇分析的角度对古诗翻译中的衔接与连贯进行分析。同时指出在翻译古诗时，要理清古诗内在的逻辑关系，恰当运用各种语篇衔接手段，使译文保持自然和连贯。
Superpower monochromatic coherent synchrotron radiation
International Nuclear Information System (INIS)
Here a special case of coherent synchrotron radiation from relativistic electron bunches distributed uniformly on a circular orbit is investigated. The possibility to obtain a monochromatic intense coherent radiation in the long-wavelength region is shown
Coherent states in quantum mechanics
International Nuclear Information System (INIS)
We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out. (author)
Coherent states in quantum mechanics
Rodrigues, R D L; Fernandes, D
2001-01-01
We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out.
Coherent hybrid electromagnetic field imaging
Cooke, Bradly J.; Guenther, David C.
2008-08-26
An apparatus and corresponding method for coherent hybrid electromagnetic field imaging of a target, where an energy source is used to generate a propagating electromagnetic beam, an electromagnetic beam splitting means to split the beam into two or more coherently matched beams of about equal amplitude, and where the spatial and temporal self-coherence between each two or more coherently matched beams is preserved. Two or more differential modulation means are employed to modulate each two or more coherently matched beams with a time-varying polarization, frequency, phase, and amplitude signal. An electromagnetic beam combining means is used to coherently combine said two or more coherently matched beams into a coherent electromagnetic beam. One or more electromagnetic beam controlling means are used for collimating, guiding, or focusing the coherent electromagnetic beam. One or more apertures are used for transmitting and receiving the coherent electromagnetic beam to and from the target. A receiver is used that is capable of square-law detection of the coherent electromagnetic beam. A waveform generator is used that is capable of generation and control of time-varying polarization, frequency, phase, or amplitude modulation waveforms and sequences. A means of synchronizing time varying waveform is used between the energy source and the receiver. Finally, a means of displaying the images created by the interaction of the coherent electromagnetic beam with target is employed.
Vector coherent state representations and their inner products
International Nuclear Information System (INIS)
Several advances have extended the power and versatility of coherent state theory to the extent that it has become a vital tool in the representation theory of Lie groups and their Lie algebras. Representative applications are reviewed and some new developments are introduced. The examples given are chosen to illustrate special features of the scalar and vector coherent state constructions and how they work in practical situations. Comparisons are made with Mackey's theory of induced representations. For simplicity, we focus on square integrable (discrete series) unitary representations although many of the techniques apply more generally, with minor adjustment. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (review)
Generalized Grassmannian Coherent States For Pseudo-Hermitian $n$ Level Systems
Najarbashi, G.; Fasihi, M. A.; H. Fakhri
2010-01-01
The purpose of this paper is to generalize fermionic coherent states for two-level systems described by pseudo-Hermitian Hamiltonian \\cite{Trifonov}, to n-level systems. Central to this task is the expression of the coherent states in terms of generalized Grassmann variables. These kind of Grassmann coherent states satisfy bi-overcompleteness condition instead of over-completeness one, as it is reasonably expected because of the biorthonormality of the system. Choosing an appropriate Grassman...
On deformations and quantization in topological string theory
Energy Technology Data Exchange (ETDEWEB)
Kay, Michael
2014-04-30
The study of moduli spaces of N=(2,2) superconformal field theories and more generally of N=(2,2) supersymmetric quantum field theories, has been a longstanding, multifaceted area of research. In this thesis we focus on certain selected general aspects of this study and develop general techniques within the framework of topological string theory. This work is naturally divided into two parts. The first is concerned with aspects of closed topological string theory, and culminates with a theory, where the geometrical structure of the topological anti-topological moduli spaces of N=(2,2) superconformal field theories with central charge c=9 is rediscovered in the light of quantization, within a general framework. The second part is concerned with aspects of the study of the open and closed moduli space of topological conformal field theories at genus zero. In particular, it contains an exposition of a paper, where general results on the classification and computation of bulk-induced deformations of open topological conformal field theories were obtained from a coherent algebraic approach, drawing from the defining L{sub ∞} and A{sub ∞} structures involved. In part, the latter investigation is restricted to arbitrary affine B-twisted Landau Ginzburg models. Subsequently, further original work is presented that completes the topological string field theory structure of B-twisted Landau Ginzburg models.
On deformations and quantization in topological string theory
International Nuclear Information System (INIS)
The study of moduli spaces of N=(2,2) superconformal field theories and more generally of N=(2,2) supersymmetric quantum field theories, has been a longstanding, multifaceted area of research. In this thesis we focus on certain selected general aspects of this study and develop general techniques within the framework of topological string theory. This work is naturally divided into two parts. The first is concerned with aspects of closed topological string theory, and culminates with a theory, where the geometrical structure of the topological anti-topological moduli spaces of N=(2,2) superconformal field theories with central charge c=9 is rediscovered in the light of quantization, within a general framework. The second part is concerned with aspects of the study of the open and closed moduli space of topological conformal field theories at genus zero. In particular, it contains an exposition of a paper, where general results on the classification and computation of bulk-induced deformations of open topological conformal field theories were obtained from a coherent algebraic approach, drawing from the defining L∞ and A∞ structures involved. In part, the latter investigation is restricted to arbitrary affine B-twisted Landau Ginzburg models. Subsequently, further original work is presented that completes the topological string field theory structure of B-twisted Landau Ginzburg models.
A resistance formula for coherent multi-barrier structures
Institute of Scientific and Technical Information of China (English)
Zhang Zhi-Chen; Yang Jian-Hong
2007-01-01
Using the Landauer formula and the quantum S-matrix scattering theory, we derive a resistance formula for multi-barrier structure under phase coherent transmission condition. This formula shows that when the transport is coherent, the potential wells of the structure are just like conductors contributing to the overall resistance. And because the resistance formula is derived based on the scattering theory, the barrier resistance will change with the number of scattering centres (i.e. the number of barriers) in the structure.
A method for ultrashort electron pulse-shape measurement using coherent synchrotron radiation
International Nuclear Information System (INIS)
In this paper we discuss a method for nondestructive measurements of the longitudinal profile of sub-picosecond electron bunches for X-ray free electron lasers (XFELs). The method is based on the detection of the coherent synchrotron radiation (CSR) spectrum produced by a bunch passing a dipole magnet system. This work also contains a systematic treatment of synchrotron radiation theory which lies at the basis of CSR. Standard theory of synchrotron radiation uses several approximations whose applicability limits are often forgotten: here we present a systematic discussion about these assumptions. Properties of coherent synchrotron radiation from an electron moving along an arc of a circle are then derived and discussed. We describe also an effective and practical diagnostic technique based on the utilization of an electromagnetic undulator to record the energy of the coherent radiation pulse into the central cone. This measurement must be repeated many times with different undulator resonant frequencies in order to reconstruct the modulus of the bunch form-factor. The retrieval of the bunch profile function from these data is performed by means of deconvolution techniques: for the present work we take advantage of a constrained deconvolution method. We illustrate with numerical examples the potential of the proposed method for electron beam diagnostics at the TESLA test facility (TTF) accelerator. Here we choose, for emphasis, experiments aimed at the measure of the strongly non-Gaussian electron bunch profile in the TTF femtosecond-mode operation. We demonstrate that a tandem combination of a picosecond streak camera and a CSR spectrometer can be used to extract shape information from electron bunches with a narrow leading peak and a long tail. (orig.)
Coherent OCDMA communication systems
Wang, Xu
2012-01-01
Coherent optical code division multiple access (OCDMA) technique, where encoding and decoding are based on the phase and amplitude of optical field instead of its intensity, is receiving much attention for the overall superior performance over incoherent OCDMA and the development of compact and reliable en/decoders (E/D) such as spatial light phase modulator (SLPM), superstructured fiber Bragg grating (SSFBG) and multi-port array waveguide grating (AWG)-type E/D. In this paper, we will discuss several recent progresses in coherent OCDMA: a. Novel coding technology such as multi-phase-level SSFBG encoder, 50x50 multiport en/decoder and reconfigurable time domain spectral phase en/decoding; b. New signal modulation formats in OCDMA including DPSK, DQPSK, CSK and M-ary CSK; and c. Field trials of high capacity WDM/OCDMA systems.
Acoustic coherent perfect absorbers
International Nuclear Information System (INIS)
In this paper, we explore the possibility of achieving acoustic coherent perfect absorbers. Through numerical simulations in two dimensions, we demonstrate that the energy of coherent acoustic waves can be totally absorbed by a fluid absorber with specific complex mass density or bulk modulus. The robustness of such absorbing systems is investigated under small perturbations of the absorber parameters. We find that when the resonance order is the lowest and the size of the absorber is comparable to the wavelength in the background, the phenomenon of perfect absorption is most stable. When the wavelength inside both the background and the absorber is much larger than the size of the absorber, perfect absorption is possible when the mass density of the absorber approaches the negative value of the background mass density. Finally, we show that by using suitable dispersive acoustic metamaterials, broadband acoustic perfect absorption may be achieved. (papers)
Spectral coherence in windturbine wakes
Energy Technology Data Exchange (ETDEWEB)
Hojstrup, J. [Riso National Lab., Roskilde (Denmark)
1996-12-31
This paper describes an experiment at a Danish wind farm to investigate the lateral and vertical coherences in the nonequilibrium turbulence of a wind turbine wake. Two meteorological masts were instrumented for measuring profiles of mean speed, turbulence, and temperature. Results are provided graphically for turbulence intensities, velocity spectra, lateral coherence, and vertical coherence. The turbulence was somewhat influenced by the wake, or possibly from aggregated wakes further upstream, even at 14.5 diameters. Lateral coherence (separation 5m) seemed to be unaffected by the wake at 7.5 diameters, but the flow was less coherent in the near wake. The wake appeared to have little influence on vertical coherence (separation 13m). Simple, conventional models for coherence appeared to be adequate descriptions for wake turbulence except for the near wake situation. 3 refs., 7 figs., 1 tab.
Institute of Scientific and Technical Information of China (English)
LU Baida; PAN Liuzhan
2004-01-01
Based on the propagation theory of partially coherent light in the space-frequency domain, the anomalous spectral behavior and spectral switches in the far field of partially coherent and polychromatic light diffracted at an aperture are studied. It is shown that, as compared with spatially fully coherent and polychromatic light whose spectral anomalies are induced only by aperture diffraction, the spectral anomalies and spectral switches of partially coherent and polychromatic light depend on the aperture diffraction, spatial correlation βand bandwidth of the original spectrum. Detailed numerical calculations are made to illustrate the behavior of spectral switches of partially coherent and polychromatic light, and the results for spatially fully coherent and polychromatic light are treated as a special case of β=1 and included in our theory.
Bidirectional coherent classical communication
Harrow, Aram W.; Leung, Debbie W.
2005-01-01
A unitary interaction coupling two parties enables quantum or classical communication in both the forward and backward directions. Each communication capacity can be thought of as a tradeoff between the achievable rates of specific types of forward and backward communication. Our first result shows that for any bipartite unitary gate, bidirectional coherent classical communication is no more difficult than bidirectional classical communication — they have the same achievable rate regions. ...
Interleaved optical coherence tomography.
Lee, Hee Yoon; Sudkamp, Helge; Marvdashti, Tahereh; Ellerbee, Audrey K
2013-11-01
We present a novel and cost-effective technique--interleaved optical coherence tomography (iOCT)--to enhance the imaging speed of swept source OCT systems by acquiring data from multiple lateral positions simultaneously during a single wavelength sweep, using a single detector and a virtually imaged phase array (VIPA) as a multi-band demultiplexer. This technique uses spectral encoding to convert coherence length into higher imaging speed; the speed enhancement factor is independent of the source speed or center wavelength, and the effective A-scan rate scales linearly with sweep speed. The optical configuration requires only a change in the sample arm of a traditional OCT system and preserves the axial resolution and fall-off characteristic of a traditional SS-OCT using the same light source. Using 10 kHz, 20 kHz and 100 kHz sources we provide a first demonstration of image speed enhancement factors of up to 12, 6 and 10, respectively, which yield effective A-scan rates of 120 kHz, 120 kHz and 1 MHz for B-scan imaging, with a sensitivity of up to 82.5 dB. We also show that iOCT can image faster dynamics than traditional OCT B-scan imaging and is capable of 3D biological imaging. The iOCT concept suggests a new route to high-speed OCT imaging for laser developers: that is, by focusing on improving the coherence length and linewidth of existing and emerging sources. Hence, iOCT is a nice complement to ongoing research and commercial efforts to enable faster imaging through development of lasers with faster sweep rates, and offers new hope for existing sources with slow sweep rates and potential for enhancement of coherence length to compete with faster sources to achieve high-speed OCT. PMID:24216876
Energy Technology Data Exchange (ETDEWEB)
Litvinenko,V.
2009-05-04
Cooling intense high-energy hadron beams remains a major challenge in modern accelerator physics. Synchrotron radiation is still too feeble, while the efficiency of two other cooling methods, stochastic and electron, falls rapidly either at high bunch intensities (i.e. stochastic of protons) or at high energies (e-cooling). In this talk a specific scheme of a unique cooling technique, Coherent Electron Cooling, will be discussed. The idea of coherent electron cooling using electron beam instabilities was suggested by Derbenev in the early 1980s, but the scheme presented in this talk, with cooling times under an hour for 7 TeV protons in the LHC, would be possible only with present-day accelerator technology. This talk will discuss the principles and the main limitations of the Coherent Electron Cooling process. The talk will describe the main system components, based on a high-gain free electron laser driven by an energy recovery linac, and will present some numerical examples for ions and protons in RHIC and the LHC and for electron-hadron options for these colliders. BNL plans a demonstration of the idea in the near future.
Energy Technology Data Exchange (ETDEWEB)
Sebastion, R.L. [Coleman Research Corp., Springfield, VA (United States)
1995-10-01
The Coherent Laser Vision System (CLVS) is being developed to provide precision real-time 3D world views to support site characterization and robotic operations and during facilities Decontamination and Decommissioning. Autonomous or semiautonomous robotic operations requires an accurate, up-to-date 3D world view. Existing technologies for real-time 3D imaging, such as AM laser radar, have limited accuracy at significant ranges and have variability in range estimates caused by lighting or surface shading. Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no-moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic to coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system.
Korman, Simon; Avidan, Shai
2016-06-01
Coherency Sensitive Hashing (CSH) extends Locality Sensitivity Hashing (LSH) and PatchMatch to quickly find matching patches between two images. LSH relies on hashing, which maps similar patches to the same bin, in order to find matching patches. PatchMatch, on the other hand, relies on the observation that images are coherent, to propagate good matches to their neighbors in the image plane, using random patch assignment to seed the initial matching. CSH relies on hashing to seed the initial patch matching and on image coherence to propagate good matches. In addition, hashing lets it propagate information between patches with similar appearance (i.e., map to the same bin). This way, information is propagated much faster because it can use similarity in appearance space or neighborhood in the image plane. As a result, CSH is at least three to four times faster than PatchMatch and more accurate, especially in textured regions, where reconstruction artifacts are most noticeable to the human eye. We verified CSH on a new, large scale, data set of 133 image pairs and experimented on several extensions, including: k nearest neighbor search, the addition of rotation and matching three dimensional patches in videos. PMID:26372204
International Nuclear Information System (INIS)
In this paper we discuss a proposal of coherent states for loop quantum gravity. These states are labeled by a point in the phase space of general relativity as captured by a spin-network graph. They are defined as the gauge-invariant projection of a product over links of Hall's heat kernels for the cotangent bundle of SU(2). The labels of the state are written in terms of two unit vectors, a spin and an angle for each link of the graph. The heat-kernel time is chosen to be a function of the spin. These labels are the ones used in the spin-foam setting and admit a clear geometric interpretation. Moreover, the set of labels per link can be written as an element of SL(2,C). These states coincide with Thiemann's coherent states with the area operator as complexifier. We study the properties of semiclassicality of these states and show that, for large spins, they reproduce a superposition over spins of spin-networks with nodes labeled by Livine-Speziale coherent intertwiners. Moreover, the weight associated to spins on links turns out to be given by a Gaussian times a phase as originally proposed by Rovelli.
International Nuclear Information System (INIS)
The Coherent Laser Vision System (CLVS) is being developed to provide precision real-time 3D world views to support site characterization and robotic operations and during facilities Decontamination and Decommissioning. Autonomous or semiautonomous robotic operations requires an accurate, up-to-date 3D world view. Existing technologies for real-time 3D imaging, such as AM laser radar, have limited accuracy at significant ranges and have variability in range estimates caused by lighting or surface shading. Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no-moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic to coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system
Coherence in Turbulence: New Perspective
Levich, Eugene
2009-07-01
It is claimed that turbulence in fluids is inherently coherent phenomenon. The coherence shows up clearly as strongly correlated helicity fluctuations of opposite sign. The helicity fluctuations have cellular structure forming clusters that are actually observed as vorticity bands and coherent structures in laboratory turbulence, direct numerical simulations and most obviously in atmospheric turbulence. The clusters are named BCC - Beltrami Cellular Clusters - because of the observed nearly total alignment of the velocity and vorticity fields in each particular cell, and hence nearly maximal possible helicity in each cell; although when averaged over all the cells the residual mean helicity in general is small and does not play active dynamical role. The Beltrami like fluctuations are short-lived and stabilize only in small and generally contiguous sub-domains that are tending to a (multi)fractal in the asymptotic limit of large Reynolds numbers, Re → ∞. For the model of homogeneous isotropic turbulence the theory predicts the leading fractal dimension of BCC to be: DF = 2.5. This particular BCC is responsible for generating the Kolmogorov -5/3 power law energy spectrum. The most obvious role that BCC play dynamically is that the nonlinear interactions in them are relatively reduced, due to strong spatial alignment between the velocity field v(r, t) and the vorticity field ω(r, t) = curlv(r, t), while the physical quantities typically best characterizing turbulence intermittency, such as entrophy, vorticity stretching and generation, and energy dissipation are maximized in and near them. The theory quantitatively relates the reduction of nonlinear inter-actions to the BCC fractal dimension DF and subsequent turbulence intermittency. It is further asserted that BCC is a fundamental feature of all turbulent flows, e.g., wall bounded turbulent flows, atmospheric and oceanic flows, and their leading fractal dimension remains invariant and universal in these flows
Institute of Scientific and Technical Information of China (English)
S. Salimi; A. Mohammadzadet
2011-01-01
Pair coherent state, is a state of a two-mode radiation field that is known as a state with non-gaussian wave function. In this paper, study on the pair coherent state, we notice that with superposition of two first terms of this states, one two-qubits formed. Because of the importance of two-qubits in theory of quantum entanglement, with two different measures with the title of concurrence and D-concurrence, we have studied the amount of entanglement and discussed its details. At the end, we describe these measures for pair coherent states as a function of the amplitude of the SU（2） coherent states.
Noncommutative Coherent States and Quantum Cosmology
Juárez, Román
2014-01-01
The set of coherent states for a noncommutative quantum Bianchi I anisotropic cosmology were built to circumvent the absence of a simultaneous set of configuration observables. By extending known methods of path integrals with coherent states to their noncommutative analogues allowed us to obtain the formal expression of the propagator of the theory in terms of the covariant Husimi Q-symbol of the quantum constraint. The analysis of the equations of motion resulting from a steepest descent procedure showed the existence of solutions displaying a minimum value of the volume scaling function which are, in turn, compatible with a physically inspired definition for a bounce. More importantly, a lower bound for the volume at the bounce which incorporates quantum mechanical and noncommutativite contributions was established. The asymptotic analysis of the solutions in the vicinity of the bounce was performed by implementing techniques used in boundary-layer problems. The numerical simulations that confirm our resul...
Coherent water transport across the South Atlantic
Wang, Y; Beron-Vera, F J
2015-01-01
The role of mesoscale eddies in transporting Agulhas leakage is investigated using a recent technique from nonlinear dynamical systems theory applied on geostrophic currents inferred from the over two-decade-long satellite altimetry record. Eddies are found to acquire material coherence away from the Agulhas retroflection, near the Walvis Ridge in the South Atlantic. Yearly, 1 to 4 coherent material eddies are detected with diameters ranging from 40 to 280 km. A total of 23 eddy cores of about 50 km in diameter and with at least 30% of their contents traceable into the Indian Ocean were found to travel across the subtropical gyre with minor filamentation. No more than 5\\% of such cores pour their contents on the North Brazil Current. While ability of eddies to carry Agulhas leakage northwestward across the South Atlantic is supported by our analysis, this is more restricted than suggested by earlier ring transport assessments.
Quantum-coherent mixtures of causal relations
MacLean, Jean-Philippe W; Spekkens, Robert W; Resch, Kevin J
2016-01-01
Understanding the causal influences that hold among the parts of a system is critical both to explaining that system's natural behaviour and to controlling it through targeted interventions. In a quantum world, understanding causal relations is equally important, but the set of possibilities is far richer. The two basic ways in which a pair of time-ordered quantum systems may be causally related are by a cause-effect mechanism or by a common cause acting on both. Here, we show that it is possible to have a coherent mixture of these two possibilities. We realize such a nonclassical causal relation in a quantum optics experiment and derive a set of criteria for witnessing the coherence based on a quantum version of Berkson's paradox. The interplay of causality and quantum theory lies at the heart of challenging foundational puzzles, such as Bell's theorem and the search for quantum gravity, but could also provide a resource for novel quantum technologies.
Entanglement and coherence in quantum state merging
Streltsov, A; Rana, S; Bera, M N; Winter, A; Lewenstein, M
2016-01-01
Understanding the resource consumption in distributed scenarios is one of the main goals of quantum information theory. A prominent example for such a scenario is the task of quantum state merging where two parties aim to merge their parts of a tripartite quantum state. In standard quantum state merging, entanglement is considered as an expensive resource, while local quantum operations can be performed at no additional cost. However, recent developments show that some local operations could be more expensive than others: it is reasonable to distinguish between local incoherent operations and local operations which can create coherence. This idea leads us to the task of incoherent quantum state merging, where one of the parties has free access to local incoherent operations only. In this case the resources of the process are quantified by pairs of entanglement and coherence. Here, we develop tools for studying this process, and apply them to several relevant scenarios. While quantum state merging can lead to ...
Elucidation of the timescales and origins of quantum electronic coherence in LHCII
Schlau-Cohen, Gabriela S.; Ishizaki, Akihito; Calhoun, Tessa R.; Ginsberg, Naomi S.; Ballottari, Matteo; Bassi, Roberto; Fleming, Graham R.
2012-05-01
Photosynthetic organisms harvest sunlight with near unity quantum efficiency. The complexity of the electronic structure and energy transfer pathways within networks of photosynthetic pigment-protein complexes often obscures the mechanisms behind the efficient light-absorption-to-charge conversion process. Recent experiments, particularly using two-dimensional spectroscopy, have detected long-lived quantum coherence, which theory suggests may contribute to the effectiveness of photosynthetic energy transfer. Here, we present a new, direct method to access coherence signals: a coherence-specific polarization sequence, which isolates the excitonic coherence features from the population signals that usually dominate two-dimensional spectra. With this polarization sequence, we elucidate coherent dynamics and determine the overall measurable lifetime of excitonic coherence in the major light-harvesting complex of photosystem II. Coherence decays on two distinct timescales of 47 fs and ~800 fs. We present theoretical calculations to show that these two timescales are from weakly and moderately strongly coupled pigments, respectively.
Amplitude-Nth-power squeezing of PB phase coherent states
Institute of Scientific and Technical Information of China (English)
马志民; 马爱群; 陈国恒; 刘树田; 冯立峰
2004-01-01
PB Phase Coherent States are very important quantum states in quantum optics. In order to investigate the amplitude- Nth -power squeezing of PB Phase Coherent States, we introduce the algebraic properties of the PB phase operator and the PB Phase Coherent States which are constructed by PB phase theory. We applied amplitude- Nth -power squeezing theory to define the Amplitude- Nth -Power Squeezing of PB Phase Coherent States and investigate the characteristic of the amplitude- Nth -power squeezing of PB Phase Coherent States.Phase Coherent State), the results show that when Z is a real number there only exists amplitude- Nth -power squeezing of X component; when Z is a complex number, there exists amplitude- Nth -power squeezing ofX component and Y component; when Z is a pure imaginary number, if N is odd, then there does not exist amplitudeNth -power squeezing of X component, but there exists amplitude- Nth -power squeezing of Ycomponent and ifN is even, then there exists amplitude-Nth -power squeezing of X component, but there does not exist amplitudeNth -power squeezing of Y component.
Frobenius-norm-based measures of quantum coherence and asymmetry.
Yao, Yao; Dong, G H; Xiao, Xing; Sun, C P
2016-01-01
We formulate the Frobenius-norm-based measures for quantum coherence and asymmetry respectively. In contrast to the resource theory of coherence and asymmetry, we construct a natural measure of quantum coherence inspired from optical coherence theory while the group theoretical approach is employed to quantify the asymmetry of quantum states. Besides their simple structures and explicit physical meanings, we observe that these quantities are intimately related to the purity (or linear entropy) of the corresponding quantum states. Remarkably, we demonstrate that the proposed coherence quantifier is not only a measure of mixedness, but also an intrinsic (basis-independent) quantification of quantum coherence contained in quantum states, which can also be viewed as a normalized version of Brukner-Zeilinger invariant information. In our context, the asymmetry of N-qubit quantum systems is considered under local independent and collective transformations. In- triguingly, it is illustrated that the collective effect has a significant impact on the asymmetry measure, and quantum correlation between subsystems plays a non-negligible role in this circumstance. PMID:27558009
On the coherent behavior of pancreatic beta cell clusters
Energy Technology Data Exchange (ETDEWEB)
Loppini, Alessandro, E-mail: a.loppini@unicampus.it [Nonlinear Physics and Mathematical Modeling Lab, University Campus Bio-Medico, Via A. del Portillo 21, I-00128 Rome (Italy); Capolupo, Antonio, E-mail: capolupo@sa.infn.it [Physics Department, University of Salerno, Fisciano, 84084 (Italy); Cherubini, Christian, E-mail: c.cherubini@unicampus.it [Nonlinear Physics and Mathematical Modeling Lab, University Campus Bio-Medico, Via A. del Portillo 21, I-00128 Rome (Italy); International Center for Relativistic Astrophysics, University Campus Bio-Medico, Via A. del Portillo 21, I-00128, Rome (Italy); Gizzi, Alessio, E-mail: a.gizzi@unicampus.it [Nonlinear Physics and Mathematical Modeling Lab, University Campus Bio-Medico, Via A. del Portillo 21, I-00128 Rome (Italy); Bertolaso, Marta, E-mail: m.bertolaso@unicampus.it [Faculty of Engineering and Institute of Philosophy of Scientific and Technological Practice, University Campus Bio-Medico, Via A. del Portillo 21, I-00128 Rome (Italy); Filippi, Simonetta, E-mail: s.filippi@unicampus.it [Nonlinear Physics and Mathematical Modeling Lab, University Campus Bio-Medico, Via A. del Portillo 21, I-00128 Rome (Italy); International Center for Relativistic Astrophysics, University Campus Bio-Medico, Via A. del Portillo 21, I-00128, Rome (Italy); Vitiello, Giuseppe, E-mail: vitiello@sa.infn.it [Physics Department, University of Salerno, Fisciano, 84084 (Italy)
2014-09-12
Beta cells in pancreas represent an example of coupled biological oscillators which via communication pathways, are able to synchronize their electrical activity, giving rise to pulsatile insulin release. In this work we numerically analyze scale free self-similarity features of membrane voltage signal power density spectrum, through a stochastic dynamical model for beta cells in the islets of Langerhans fine tuned on mouse experimental data. Adopting the algebraic approach of coherent state formalism, we show how coherent molecular domains can arise from proper functional conditions leading to a parallelism with “phase transition” phenomena of field theory. - Highlights: • Beta cells in pancreas are coupled oscillators able to synchronize their activity. • We analyze scale free self-similarity features for beta cells. • We adopt the algebraic approach of coherent state formalism. • We show that coherent molecular domains arise from functional conditions.
On the coherent behavior of pancreatic beta cell clusters
International Nuclear Information System (INIS)
Beta cells in pancreas represent an example of coupled biological oscillators which via communication pathways, are able to synchronize their electrical activity, giving rise to pulsatile insulin release. In this work we numerically analyze scale free self-similarity features of membrane voltage signal power density spectrum, through a stochastic dynamical model for beta cells in the islets of Langerhans fine tuned on mouse experimental data. Adopting the algebraic approach of coherent state formalism, we show how coherent molecular domains can arise from proper functional conditions leading to a parallelism with “phase transition” phenomena of field theory. - Highlights: • Beta cells in pancreas are coupled oscillators able to synchronize their activity. • We analyze scale free self-similarity features for beta cells. • We adopt the algebraic approach of coherent state formalism. • We show that coherent molecular domains arise from functional conditions
Wigner time delay and related concepts: Application to transport in coherent conductors
Texier, Christophe
2016-08-01
The concepts of Wigner time delay and Wigner-Smith matrix allow us to characterise temporal aspects of a quantum scattering process. The paper reviews the statistical properties of the Wigner time delay for disordered systems; the case of disorder in 1D with a chiral symmetry is discussed and the relation with exponential functionals of the Brownian motion is underlined. Another approach for the analysis of time delay statistics is the random matrix approach, from which we review few results. As a practical illustration, we briefly outline a theory of non-linear transport and AC transport developed by Büttiker and coworkers, where the concept of Wigner-Smith time delay matrix is a central piece allowing us to describe screening properties in out-of-equilibrium coherent conductors.
S. Kern
2005-01-01
textabstractThe preceding analysis investigated private interest groups’ behaviour towards monetary policy makers and central banks, exploring the extent to which they seek to influence monetary policy and their motivations for doing so or not. Where evidence of interest group activity with respe
Propagation of some coherent and partially coherent laser beams
Cai, Yangjian
2006-01-01
In this thesis, we investigate the propagation of some coherent and partially coherent laser beams, including a dark hollow beam (DHB), an elliptical Gaussian beam (EGB), a flat-topped beam and a twisted anisotropic Gaussian Schell-model (TAGSM) beam, through a paraxial optical system or a turbulent atmosphere. Several theoretical models are proposed to describe a DHB of circular or non-circular symmetry. Approximate analytical formulas for a DHB and a partially coherent TAGSM beam propagatin...
Relatedness, Coherence, and Coherence Dynamics Empirical Evidence from Italian Manufacturing
Stefano Valvano; Davide Vannoni
2001-01-01
This paper investigates the determinants of coherence and coherence change using a sample of Italian leading firms in the period 1993-1996. Following a methodology developed by Teece et al (1994), the observed diversification patterns of our sample firms provide the information required to construct an index of relatedness between pair of sectors, which is in turn used to obtain a measure of firm’s coherence. The econometric analysis highlights that relatedness is higher when sectors share si...
Bartlett, S D; Repka, J; Bartlett, Stephen D.; Rowe, David J.; Repka, Joe
2002-01-01
It is shown here and in the preceeding paper that vector coherent state theory, the theory of induced representations, and geometric quantization provide alternative but equivalent quantizations of an algebraic model. The relationships are useful because some constructions are simpler and more natural from one perspective than another. More importantly, each approach suggests ways of generalizing its counterparts. In this paper, we focus on the construction of quantum models for algebraic systems with intrinsic degrees of freedom. Semi-classical partial quantizations, for which only the intrinsic degrees of freedom are quantized, arise naturally out of this construction. The quantization of the SU(3) and rigid rotor models are considered as examples.
Generalized Grassmannian Coherent States For Pseudo-Hermitian $n$ Level Systems
Fakhri, G Najarbashi' M A Fasihi' H
2010-01-01
The purpose of this paper is to generalize fermionic coherent states for two-level systems described by pseudo-Hermitian Hamiltonian \\cite{Trifonov}, to n-level systems. Central to this task is the expression of the coherent states in terms of generalized Grassmann variables. These kind of Grassmann coherent states satisfy bi-overcompleteness condition instead of over-completeness one, as it is reasonably expected because of the biorthonormality of the system. Choosing an appropriate Grassmann weight function resolution of identity is examined. Moreover Grassmannian coherent and squeezed states of deformed group $SU_{q}(2)$ for three level pseudo-Hermitian system are presented.
X-ray Coherent diffraction interpreted through the fractional Fourier transform
Bolloc'h, David Le; Sadoc, Jean-Francois
2011-01-01
Diffraction of coherent x-ray beams is treated through the Fractionnal Fourier transform. The transformation allow us to deal with coherent diffraction experiments from the Fresnel to the Fraunhofer regime. The analogy with the Huygens-Fresnel theory is first discussed and a generalized uncertainty principle is introduced.
Relations Between Characteristic Function, Positive P-Representation and Coherent Thermal State
Institute of Scientific and Technical Information of China (English)
FAN Hong-Yi; XU Xing-Lei
2007-01-01
We employ the coherent thermal states (a kind of entangled states) in thermal field dynamics to establish a complete entangled state formalism expressing pseudo-classical representations of density operator for light field.Especially, the relationship between the coherent thermal state and the characteristic function and the positive P representation in quantum optics theory are obtained.
Dimensioning BCH codes for coherent DQPSK systems with laser phase noise and cycle slips
DEFF Research Database (Denmark)
Leong, Miu Yoong; Larsen, Knud J.; Jacobsen, Gunnar;
2014-01-01
Forward error correction (FEC) plays a vital role in coherent optical systems employing multi-level modulation. However, much of coding theory assumes that additive white Gaussian noise (AWGN) is dominant, whereas coherent optical systems have significant phase noise (PN) in addition to AWGN. Thi...
Assisted Distillation of Quantum Coherence
Chitambar, E.; Streltsov, A.; Rana, S.; Bera, M. N.; Adesso, G.; Lewenstein, M.
2016-02-01
We introduce and study the task of assisted coherence distillation. This task arises naturally in bipartite systems where both parties work together to generate the maximal possible coherence on one of the subsystems. Only incoherent operations are allowed on the target system, while general local quantum operations are permitted on the other; this is an operational paradigm that we call local quantum-incoherent operations and classical communication. We show that the asymptotic rate of assisted coherence distillation for pure states is equal to the coherence of assistance, an analog of the entanglement of assistance, whose properties we characterize. Our findings imply a novel interpretation of the von Neumann entropy: it quantifies the maximum amount of extra quantum coherence a system can gain when receiving assistance from a collaborative party. Our results are generalized to coherence localization in a multipartite setting and possible applications are discussed.
Assisted Distillation of Quantum Coherence.
Chitambar, E; Streltsov, A; Rana, S; Bera, M N; Adesso, G; Lewenstein, M
2016-02-19
We introduce and study the task of assisted coherence distillation. This task arises naturally in bipartite systems where both parties work together to generate the maximal possible coherence on one of the subsystems. Only incoherent operations are allowed on the target system, while general local quantum operations are permitted on the other; this is an operational paradigm that we call local quantum-incoherent operations and classical communication. We show that the asymptotic rate of assisted coherence distillation for pure states is equal to the coherence of assistance, an analog of the entanglement of assistance, whose properties we characterize. Our findings imply a novel interpretation of the von Neumann entropy: it quantifies the maximum amount of extra quantum coherence a system can gain when receiving assistance from a collaborative party. Our results are generalized to coherence localization in a multipartite setting and possible applications are discussed. PMID:26943512
Volitional Control of Neuromagnetic Coherence
Directory of Open Access Journals (Sweden)
Matthew D Sacchet
2012-12-01
Full Text Available Coherence of neural activity between circumscribed brain regions has been implicated as an indicator of intracerebral communication in various cognitive processes. While neural activity can be volitionally controlled with neurofeedback, the volitional control of coherence has not yet been explored. Learned volitional control of coherence could elucidate mechanisms of associations between cortical areas and its cognitive correlates and may have clinical implications. Neural coherence may also provide a signal for brain-computer interfaces (BCI. In the present study we used the Weighted Overlapping Segment Averaging (WOSA method to assess coherence between bilateral magnetoencephalograph (MEG sensors during voluntary digit movement as a basis for BCI control. Participants controlled an onscreen cursor, with a success rate of 124 of 180 (68.9%, sign-test p < 0.001 and 84 out of 100 (84%, sign-test p < 0.001. The present findings suggest that neural coherence may be volitionally controlled and may have specific behavioral correlates.
DEFF Research Database (Denmark)
Mogensen, Mette; Themstrup, Lotte; Banzhaf, Christina;
2014-01-01
Optical coherence tomography (OCT) has developed rapidly since its first realisation in medicine and is currently an emerging technology in the diagnosis of skin disease. OCT is an interferometric technique that detects reflected and backscattered light from tissue and is often described as the...... optical analogue to ultrasound. The inherent safety of the technology allows for in vivo use of OCT in patients. The main strength of OCT is the depth resolution. In dermatology, most OCT research has turned on non-melanoma skin cancer (NMSC) and non-invasive monitoring of morphological changes in a...
DEFF Research Database (Denmark)
Andersen, Peter E.
2015-01-01
Optical coherence tomography (OCT) is a noninvasive imaging technique that provides real-time two- and three-dimensional images of scattering samples with micrometer resolution. Mapping the local reflectivity, OCT visualizes the morphology of the sample, in real time or at video rate. In addition......-rate imaging is feasible, which has enabled optical microangiography, i.e., visualization of retinal and chorodial blood flow. Such label-free optical microangiography might be feasible as an adjunct modality to fluorescence-based angiography. In this review, the fundamental principles of OCT imaging and its...
Brignon, Arnaud
2013-01-01
Recently, the improvement of diode pumping in solid state lasers and the development of double clad fiber lasers have allowed to maintain excellent laser beam quality with single mode fibers. However, the fiber output power if often limited below a power damage threshold. Coherent laser beam combining (CLBC) brings a solution to these limitations by identifying the most efficient architectures and allowing for excellent spectral and spatial quality. This knowledge will become critical for the design of the next generation high-power lasers and is of major interest to many industrial, environme
Coherent dynamics in semiconductors
DEFF Research Database (Denmark)
Hvam, Jørn Märcher
1998-01-01
Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...
Objective Eulerian coherent structures
Serra, Mattia; Haller, George
2016-05-01
We define objective Eulerian Coherent Structures (OECSs) in two-dimensional, non-autonomous dynamical systems as the instantaneously most influential material curves. Specifically, OECSs are stationary curves of the averaged instantaneous material stretching-rate or material shearing-rate functionals. From these objective (frame-invariant) variational principles, we obtain explicit differential equations for hyperbolic, elliptic, and parabolic OECSs. As an illustration, we compute OECSs in an unsteady ocean velocity data set. In comparison to structures suggested by other common Eulerian diagnostic tools, we find OECSs to be the correct short-term cores of observed trajectory deformation patterns.
Objective Eulerian Coherent Structures
Serra, M
2015-01-01
We define objective Eulerian Coherent Structures (OECSs) in two-dimensional, non-autonomous dynamical systems as instantaneously most influential material curves. Specifically, OECSs are stationary curves of the averaged instantaneous material stretching-rate or material shearing-rate functionals. From these objective (frame-invariant) variational principles, we obtain explicit differential equations for hyperbolic, elliptic and parabolic OECSs. As illustration, we compute OECSs in an unsteady ocean velocity data set. In comparison to structures suggested by other common Eulerian diagnostic tools, we find OECSs to be the correct short-term cores of observed trajectory deformation patterns.
Diffraction coherence in optics
Françon, M; Green, L L
2013-01-01
Diffraction: Coherence in Optics presents a detailed account of the course on Fraunhofer diffraction phenomena, studied at the Faculty of Science in Paris. The publication first elaborates on Huygens' principle and diffraction phenomena for a monochromatic point source and diffraction by an aperture of simple form. Discussions focus on diffraction at infinity and at a finite distance, simplified expressions for the field, calculation of the path difference, diffraction by a rectangular aperture, narrow slit, and circular aperture, and distribution of luminous flux in the airy spot. The book th
Uniformly hyperbolic control theory
Kawan, Christoph
2015-01-01
This paper gives a summary of a body of work at the intersection of control theory and smooth nonlinear dynamics. The main idea is to transfer the concept of uniform hyperbolicity, central to the theory of smooth dynamical systems, to control-affine systems. Combining the strength of geometric control theory and the hyperbolic theory of dynamical systems, it is possible to deduce control-theoretic results of non-local nature that reveal remarkable analogies to the classical hyperbolic theory ...
Review of Entangled Coherent States
Sanders, Barry C
2011-01-01
We review entangled coherent state research since its first implicit use in 1967 to the present. Entangled coherent states are important to quantum superselection principles, quantum information processing, quantum optics, and mathematical physics. Despite their inherent fragility they have produced in a conditional propagating-wave quantum optics realization. Fundamentally the states are intriguing because they are entanglements of the coherent states, which are in a sense the most classical of all states of a dynamical system.
Quantum correlation via quantum coherence
Yu, Chang-shui; Zhang, Yang; Zhao, Haiqing
2014-01-01
Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition--------quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes ...
International Nuclear Information System (INIS)
The aim was to give advanced students of philosophy with interest for physics an actual and solid introduction to the quantum theory. Simultaneously the book confronts also physicists with the philosophical questions of their field. After clearance of the foundations the second chapters introduces to the minimal interpretation and the ''Copenhagen interpretation''. In the third chapter many-particle systems are introduced and their pecularities discussed. The fourth chapter deals with the theme-circle ''entangled states'' and ''nonlocality''. In the first parter of the fifth chapter the De-Broglie-Bohm theory and in the second part the many-world interpretation of the quantum theory are presented. In the sixth chapter the bow is spanned to (relativistic) quantum field theories. Finally the seventh chapter rounds the book off in the framework of a small chronology of important development steps in physical-mathematical as also interpretatorical view.
On Nonlinear Bosonic Coherent States
Genovese, Marco; Rasetti, Mario
2009-01-01
Nonlinear coherent states are an interesting resource for quantum technologies. Here we investigate some critical features of the single-boson nonlinear coherent states, which are theoretically constructed as eigenstates of the annihilation operator and experimentally realized as stationary states of a trapped laser-driven ion. We show that the coherence and the minimum-uncertainty properties of such states are broken for values of the Lamb-Dicke parameter corresponding to the roots of the Laguerre polynomials, which enter their explicit expression. The case of the multiboson nonlinear coherent states is also discussed.
Emittance growth from transient coherent synchrotron radiation
International Nuclear Information System (INIS)
If the energies of individual particles in a bunch change as the bunch traverses a bending system, even if it is achromatic, betatron oscillations can be excited. Consequently, the transverse emittance of the bunch will grow as it moves downstream. Short bunches may be particularly susceptible to emission of coherent synchrotron radiation which can act back on the particles to change their energies and trajectories. Because a bend spans a well-defined length and angle, the bunch-excited wakefield and its effect back on the bunch are inherently transient. We outline a recently developed theory of this effect and apply it to example bending systems
Discourse Coherence:Receiver’s Context Selection
Institute of Scientific and Technical Information of China (English)
董淑新
2012-01-01
Discourse is a kind of ostensive-inferential communication. Discourse as a communication always occurs in certain context which helps us interpret an utterance. Obviously, context or contextual assumptions play a crucial role in answering these questions. Therefore, the crucial point to solve the problem of discourse coherence is how to select the contexts. Con⁃text selection is not random but limited by the language users’cognitive environment. According to Relevance Theory, con⁃text selection is achieved through seeking for relevance.
Coherent pion production in electroweak processes
International Nuclear Information System (INIS)
We report a relativistic calculation for photon, electron and neutrino induced coherent pion production on spin zero nuclei. The matrix elements for these reactions are written by using effective Lagrangian formalism in field theory. The dominant Feynman diagrams contributing to this process are taken into account. The cross-section calculations are done in local density approximation and the nuclear medium effects are incorporated in terms of the delta self energy in the nuclear medium. The final state interactions of the outgoing pions are taken into account using Eikonal approximation for the distortion of the pion. (author)
The origins of macroscopic quantum coherence in high temperature superconductivity
International Nuclear Information System (INIS)
Highlights: • We propose a new theoretical approach to superconductivity in p-type cuprates. • Electron pairing mechanisms in the superconducting and pseudogap phases are proposed. • A scale free network of dopants is key to macroscopic quantum coherence. - Abstract: A new, theoretical approach to macroscopic quantum coherence and superconductivity in the p-type (hole doped) cuprates is proposed. The theory includes mechanisms to account for e-pair coupling in the superconducting and pseudogap phases and their inter relations observed in these materials. Electron pair coupling in the superconducting phase is facilitated by local quantum potentials created by static dopants in a mechanism which explains experimentally observed optimal doping levels and the associated peak in critical temperature. By contrast, evidence suggests that electrons contributing to the pseudogap are predominantly coupled by fractal spin waves (fractons) induced by the fractal arrangement of dopants. On another level, the theory offers new insights into the emergence of a macroscopic quantum potential generated by a fractal distribution of dopants. This, in turn, leads to the emergence of coherent, macroscopic spin waves and a second associated macroscopic quantum potential, possibly supported by charge order. These quantum potentials play two key roles. The first involves the transition of an expected diffusive process (normally associated with Anderson localization) in fractal networks, into e-pair coherence. The second involves the facilitation of tunnelling between localized e-pairs. These combined effects lead to the merger of the super conducting and pseudo gap phases into a single coherent condensate at optimal doping. The underlying theory relating to the diffusion to quantum transition is supported by Coherent Random Lasing, which can be explained using an analogous approach. As a final step, an experimental program is outlined to validate the theory and suggests a new
International Nuclear Information System (INIS)
The transverse focusing properties at the ‘pseudo-focal’ plane of coherent Bessel beams with angular momentum are analyzed in detail. The transverse magnification of the central dark region of Bessel beams at this pseudo-focal plane is derived for the first time by calculating the ratio of the magnitude of the transverse components of the corresponding wave vectors before and after the focusing lens. We test our results experimentally with coherent laser Bessel beams and excellent agreement is observed. Then, an LED light source is used to generate Bessel beams. By modifying the coherence of the LED light source, we observe that by reducing coherence a smaller and shallower central dark region of Bessel beams with angular momentum is produced at the pseudo-focal plane. This technique can be used as a method to characterize the degree of coherence of vortex beams. (paper)
He, Xi; Wu, Fengtie; Chen, Ziyang; Pu, Jixiong; Chavez-Cerda, Sabino
2016-05-01
The transverse focusing properties at the ‘pseudo-focal’ plane of coherent Bessel beams with angular momentum are analyzed in detail. The transverse magnification of the central dark region of Bessel beams at this pseudo-focal plane is derived for the first time by calculating the ratio of the magnitude of the transverse components of the corresponding wave vectors before and after the focusing lens. We test our results experimentally with coherent laser Bessel beams and excellent agreement is observed. Then, an LED light source is used to generate Bessel beams. By modifying the coherence of the LED light source, we observe that by reducing coherence a smaller and shallower central dark region of Bessel beams with angular momentum is produced at the pseudo-focal plane. This technique can be used as a method to characterize the degree of coherence of vortex beams.
Nel, Louis
2016-01-01
This book presents a detailed, self-contained theory of continuous mappings. It is mainly addressed to students who have already studied these mappings in the setting of metric spaces, as well as multidimensional differential calculus. The needed background facts about sets, metric spaces and linear algebra are developed in detail, so as to provide a seamless transition between students' previous studies and new material. In view of its many novel features, this book will be of interest also to mature readers who have studied continuous mappings from the subject's classical texts and wish to become acquainted with a new approach. The theory of continuous mappings serves as infrastructure for more specialized mathematical theories like differential equations, integral equations, operator theory, dynamical systems, global analysis, topological groups, topological rings and many more. In light of the centrality of the topic, a book of this kind fits a variety of applications, especially those that contribute to ...
Coherent Quantum Optics Phenomena in Carbon Low-Dimensional Systems
Dovlatova, Alla; Yerchuck, Dmitri
2011-01-01
Brief review of the theoretical and experimental results, based mainly on the works of authors, in the application of quantum field theory to the study of carbon low-dimensional systems - quasi-1D carbon nanotubes, carbynes and graphene with emphasis on formation of longlived coherent states of joint photon-electron and joint resonance phonon-electron systems of given materials is presented.
A Cohesive and Coherent Analysis of The Purloined Letter
Institute of Scientific and Technical Information of China (English)
杜娟娟; 郭鸿雁
2013-01-01
The thesis aims to do a research on the cohesion and coherence in The Purloined Letter written by Edgar Allan Poe based on the theories of Halliday and Hasan as well as the Chinese scholars Zhang Delu and Liu Rushan. By the means of them, Poe’s ingenious composition and vivid characters emerge in the mind of the readers.
Narrow coherent effects in πNN-dynamics
International Nuclear Information System (INIS)
Coherent effect production is considered in πNN-dynamics with resonant pion-nucleon interaction via Brueckner theory and Faddev equations. It is shown that the narrow energy and final momentum dependence can arise in the inelastic S-wave πd-scattering. The energy dependence peculiarities can have a width an order magnitude less than πN-resonance one
Educating the design stance:issues of coherence and transgression
Freeman, Norman H.; Allen, Melissa L
2013-01-01
Bullot & Reber (B&R) put forth a design stance to fuse psychological and art historical accounts of visual thinking into a single theory. We argue that this aspect of their proposal needs further fine-tuning. Issues of transgression and coherence are necessary to provide stability to the design stance. We advocate looking to Art Education for such fundamentals of picture understanding.
Coherent backscattering of light by resonant atomic dipole transitions
International Nuclear Information System (INIS)
We study coherent backscattering (CBS) of resonant light by cold atomic vapors, both experimentally and theoretically. The theory predicts a drastic reduction of the CBS enhancement factor when a degenerate internal structure is present in the ground state. We test this prediction in experiments using different atoms and various transitions
Highly coherent modeless broadband semiconductor laser.
Sellahi, M; Myara, M; Beaudoin, G; Sagnes, I; Garnache, A
2015-09-15
We report on the highly coherent modeless broadband continuous wave operation of a semiconductor vertical-external-cavity-surface-emitting laser. The laser design is based on a frequency-shifted-feedback scheme provided by an acousto-optic frequency shifter inserted in a linear or a ring traveling wave cavity. The gain mirror is a GaAs-based multiple quantum well structure providing large gain at 1.07 μm. This laser exhibits a coherent optical spectrum over 1.27 nm (330 GHz) bandwidth, with 70 mW output power and a high beam quality. The light polarization is linear (>30 dB extinction ratio). The laser dynamics exhibits a low intensity noise close to class A regime, with a ∼1.5 MHz cutoff frequency. The frequency noise spectral density shows a first-order low-pass like shape (130 kHz cutoff) leading to a Gaussian shape for homodyne interferometric signals. The measured beat width is ≃54 kHz and the coherence time of ∼19 μs. No nonlinear effects are observed, showing dynamics very close to theory. PMID:26371921
Institute of Scientific and Technical Information of China (English)
崔振宇; 王铁
2014-01-01
本文以中心地理论为基础，建立了山东省城市旅游中心性的评价指标体系。使用因子分析法与加权求和法，确定了山东省三级旅游中心地体系，即青岛、济南为一级旅游中心地，烟台、威海、日照、泰安、济宁、临沂、潍坊为二级旅游中心地，淄博、莱芜、东营、滨州、德州、聊城、菏泽、枣庄为三级旅游中心地。在此基础上，结合空间位置、交通连接等要素，本研究将山东省划分为以两个一级旅游中心地为辐射源的旅游区，又在以济南为辐射源的旅游区内划分出三个次级旅游区，并提出了山东省旅游空间结构的优化和提升建议。%Based on the central place theory, an index system used to evaluate central tourism ability of Shan-dong Province was constructed. Using factor analysis and the weighted summation method, three grades of Shandong Province tourism central places were established as follow:Qingdao and Jinan are Grade A toursim central places;Yantai,Weihai,Rizhao,Taian,Jining,Linyi and Weifang are Grade B tourism central places;Zi-bo,Binzhou,Dongying, Dezhou, Liaocheng, Heze, Laiwu and Zaozhuang are Grade C tourism central places. Based on the above research combined with spatial location, tourism resources,transportation links and other factors,this paper divided Shandong Province into two tourism areas which were radiated by the two Grade A tourism central places. And three secondary toursim areas were divided from the tourism area radiated by Jinan. And then some suggestions were put forward.
International Nuclear Information System (INIS)
It is shown that the rational power law potentials in the two-body radial Schrodinger equations admit a systematic treatment available from the classical theory of ordinary linear differential equations of the second order. The resulting potentials come into families evolved from equations having a fixed number of elementary regular singularities. As a consequence, relations are found and discussed among the several potentials in a family. (Author)
International Nuclear Information System (INIS)
It is shown that the rational power law potentials in the two-body radial Schoedinger equation admit a systematic treatment available from the classical theory of ordinary linear differential equations of the second order. The admissible potentials come into families evolved from equations having a fixed number of elementary singularities. As a consequence, relations are found and discussed among the several potentials in a family. (Author)
Stewart, Ian
2003-01-01
Ian Stewart's Galois Theory has been in print for 30 years. Resoundingly popular, it still serves its purpose exceedingly well. Yet mathematics education has changed considerably since 1973, when theory took precedence over examples, and the time has come to bring this presentation in line with more modern approaches.To this end, the story now begins with polynomials over the complex numbers, and the central quest is to understand when such polynomials have solutions that can be expressed by radicals. Reorganization of the material places the concrete before the abstract, thus motivating the g
OPTICAL COHERENCE TOMOGRAPHY IN JUVENILE NEURONAL CEROID LIPOFUSCINOSIS
DEFF Research Database (Denmark)
Hansen, Michael S; Hove, Marianne Nørgaard; Jensen, Hanne;
2016-01-01
PURPOSE: To report optical coherence tomography findings obtained in two patients with juvenile neuronal ceroid lipofuscinosis. METHODS: Two case reports. RESULTS: Two 7-year-old girls presented with decreased visual acuity, clumsiness, night blindness, and behavioral problems. Optical coherence...... tomography showed an overall reduction in thickness of the central retina, as well as the outer and the inner retinal layers. The degenerative retinal changes were the same, despite different mutations in the CLN3 gene. CONCLUSION: In these rare cases of juvenile neuronal ceroid lipofuscinosis, optical...
Dymanics of Generalized Coherent States
Martino, S; De Siena, S.; Illuminati, F.
1995-01-01
We show that generalized coherent states follow Schr\\"{o}dinger dynamics in time-dependent potentials. The normalized wave-packets follow a classical evolution without spreading; in turn, the Schr\\"{o}dinger potential depends on the state through the classical trajectory. This feedback mechanism with continuous dynamical re-adjustement allows the packets to remain coherent indefinetely.
Dynamics of generalized coherent states
De Martino, S; Illuminati, F; De Martino, S; De Siena, S; Illuminati, F
1995-01-01
We show that generalized coherent states follow Schr\\"{o}dinger dynamics in time-dependent potentials. The normalized wave-packets follow a classical evolution without spreading; in turn, the Schr\\"{o}dinger potential depends on the state through the classical trajectory. This feedback mechanism with continuous dynamical re-adjustement allows the packets to remain coherent indefinetely.
International Nuclear Information System (INIS)
Researchers are suggesting unipolar affective disorders may be related to an abnormality in biogenic amine receptor-sensitivity. This abnormality may be a result of a dysfunction in central serotonin (5-HT) release mechanisms. 5-HT neurotransmission is modulated by presynaptic autoreceptors, which are members of the 5-HT1 receptor subtype. The autoreceptor is thought to play an important role in the homeostasis of the central 5-HT synapse and could be a site at which some antidepressants mediate their therapeutic effect. The number of 5-HT1 type receptor binding sites are reduced and behavior mediated by this receptor is abolished following repeated injections of monoamine oxidase inhibitor type antidepressants. These changes did not occur following a single injection. It was hypothesized that repeated treatment with a monoamine oxidase inhibitor would reduce the sensitivity of 5-HT autoreceptors and enhance 5-HT release. Rats were pretreated with single or repeated (twice daily for 7 days) intraperitoneal injections of nialamide (40 mg/kg) or chlorimipramine (10 mg/kg) and the ability of the autoreceptor agonist to inhibit potassium-induced 3H-5-HT release was evaluated using an in vitro superfusion system. These changes in 5-HT autoreceptor activity are consistent with other reports evaluating monoamine oxidase inhibitors on 5-HT1 type receptors. It is hypothesized that the changes in 5-HT neurotransmission are related to the antidepressant mechanism of monoamine oxidase inhibitors
Gurr, Henry
2014-03-01
Princeton Physicist J. J. Hopfield's Mathematical Model of the Mammalian Brain, (Similar To Ising Glass Model of a crystal of magnetic spin particles) says our Brain-Work for Memory, Perception, Language, Thinking, etc, (Even the AHA-EUREKA-Flash Of Insight Type Problem Solving), is achieved by our massively inter-connected CNS Neurons ... working together ... MINIMIZING an analog of physical energy ... thus yielding Optimal Solutions: These ``best'' answers, correspond to highest mental coherence, for most facets organism response, beit mental (eg: perception, memory, ideas, thinking, etc) or physical-muscular-actions (eg speaking, tool using, trail following, etc). Our brain is this way, because living creature, MUST be evolved, so they will find & use the best actions, for survival!!! Our human heritage, is to instantly compute near optimal future plans, (mental & physical-muscular), and be able to accomplish plans reliably & efficiently. If you know of book or articles in these topic areas, please email to HenryG--USCA.edu How to work well, with your own ``self'', called mind-body, will follow!! Conjectures: Who is the ``I'' that appears to make decisions? Am ``I'' the master of my domain? Is there an ``I'' or am ``I'' merely an illusion of reality.
Studies in quantum field theory
International Nuclear Information System (INIS)
Washington University is currently conducting research in many areas of high energy theoretical and mathematical physics. These areas include: strong-coupling approximation; classical solutions of non-Abelian gauge theories; mean-field approximation in quantum field theory; path integral and coherent state representations in quantum field theory; lattice gauge calculations; the nature of perturbation theory in large orders; quark condensation in QCD; chiral symmetry breaking; the l/N expansion in quantum field theory; effective potential and action in quantum field theories, including QCD
Coherent imaging without phases
Moscoso, Miguel; Papanicolaou, George
2015-01-01
In this paper we consider narrow band, active array imaging of weak localized scatterers when only the intensities are recorded at an array with N transducers. We consider that the medium is homogeneous and, hence, wave propagation is fully coherent. This work is an extension of our previous paper, where we showed that using linear combinations of intensity-only measurements imaging of localized scatterers can be carried out efficiently using MUSIC or sparsity promoting optimization. Here we show the same strategy can be accomplished with only 3N-2 illuminations, therefore reducing enormously the data acquisition process. Furthermore, we show that in the paraxial regime one can form the images by using six illuminations only. In particular, this paraxial regime includes Fresnel and Fraunhofer diffraction. The key point of this work is that if one controls the illuminations, imaging with intensity-only can be easily reduced to a imaging with phases and, therefore, one can apply standard imaging techniques. Det...
Coherent Scatter Imaging Measurements
Ur Rehman, Mahboob
In conventional radiography, anatomical information of the patients can be obtained, distinguishing different tissue types, e.g. bone and soft tissue. However, it is difficult to obtain appreciable contrast between two different types of soft tissues. Instead, coherent x-ray scattering can be utilized to obtain images which can differentiate between normal and cancerous cells of breast. An x-ray system using a conventional source and simple slot apertures was tested. Materials with scatter signatures that mimic breast cancer were buried in layers of fat of increasing thickness and imaged. The result showed that the contrast and signal to noise ratio (SNR) remained high even with added fat layers and short scan times.
DEFF Research Database (Denmark)
Andersen, Anne Bendix; Frederiksen, Kirsten; Beedholm, Kirsten;
2016-01-01
Background During the past decade, politicians and healthcare providers have strived to create a coherent healthcare system across primary and secondary healthcare sectors in Denmark. Nevertheless, elderly patients with chronic diseases (EPCD) continue to report experiences of poor-quality care and...... an acute care ward to discharge and later in meetings with healthcare providers in general practice, outpatient clinics, home care and physiotherapy. Furthermore, field observations were conducted in general practice, home care and rehabilitation settings. Research design An explorative design based...... on an interactionistic approach was used. As a consequence, the focus of data collection is the production of meaning happening between human beings in social interaction in the field of cross-sectorial collaboration. Research questions The research questions reflect the interactionistic approach as...
Quantum information and coherence
Öhberg, Patrik
2014-01-01
This book offers an introduction to ten key topics in quantum information science and quantum coherent phenomena, aimed at graduate-student level. The chapters cover some of the most recent developments in this dynamic research field where theoretical and experimental physics, combined with computer science, provide a fascinating arena for groundbreaking new concepts in information processing. The book addresses both the theoretical and experimental aspects of the subject, and clearly demonstrates how progress in experimental techniques has stimulated a great deal of theoretical effort and vice versa. Experiments are shifting from simply preparing and measuring quantum states to controlling and manipulating them, and the book outlines how the first real applications, notably quantum key distribution for secure communication, are starting to emerge. The chapters cover quantum retrodiction, ultracold quantum gases in optical lattices, optomechanics, quantum algorithms, quantum key distribution, quantum cont...
Integrated coherent matter wave circuits
International Nuclear Information System (INIS)
An integrated coherent matter wave circuit is a single device, analogous to an integrated optical circuit, in which coherent de Broglie waves are created and then launched into waveguides where they can be switched, divided, recombined, and detected as they propagate. Applications of such circuits include guided atom interferometers, atomtronic circuits, and precisely controlled delivery of atoms. We report experiments demonstrating integrated circuits for guided coherent matter waves. The circuit elements are created with the painted potential technique, a form of time-averaged optical dipole potential in which a rapidly moving, tightly focused laser beam exerts forces on atoms through their electric polarizability. Moreover, the source of coherent matter waves is a Bose-Einstein condensate (BEC). Finally, we launch BECs into painted waveguides that guide them around bends and form switches, phase coherent beamsplitters, and closed circuits. These are the basic elements that are needed to engineer arbitrarily complex matter wave circuitry
Bennis, Driss
2010-01-01
This paper unifies several generalizations of coherent rings in one notion. Namely, we introduce $n$-$\\mathscr{X}$-coherent rings, where $\\mathscr{X}$ is a class of modules and $n$ is a positive integer, as those rings for which the subclass $\\mathscr{X}_n$ of $n$-presented modules of $\\mathscr{X}$ is not empty, and every module in $\\mathscr{X}_n$ is $n+1$-presented. Then, for each particular class $\\mathscr{X}$ of modules, we find correspondent relative coherent rings. Our main aim is to show that the well-known Chase's, Cheatham and Stone's, Enochs', and Stenstrom's characterizations of coherent rings hold true for any $n$-$\\mathscr{X}$-coherent rings.
Experimental evidence of coherent transport.
Flores-Olmedo, E; Martínez-Argüello, A M; Martínez-Mares, M; Báez, G; Franco-Villafañe, J A; Méndez-Sánchez, R A
2016-01-01
Coherent transport phenomena are difficult to observe due to several sources of decoherence. For instance, in the electronic transport through quantum devices the thermal smearing and dephasing, the latter induced by inelastic scattering by phonons or impurities, destroy phase coherence. In other wave systems, the temperature and dephasing may not destroy the coherence and can then be used to observe the underlying wave behaviour of the coherent phenomena. Here, we observe coherent transmission of mechanical waves through a two-dimensional elastic Sinai billiard with two waveguides. The flexural-wave transmission, performed by non-contact means, shows the quantization when a new mode becomes open. These measurements agree with the theoretical predictions of the simplest model highlighting the universal character of the transmission fluctuations. PMID:27121226
Experimental evidence of coherent transport
Flores-Olmedo, E.; Martínez-Argüello, A. M.; Martínez-Mares, M.; Báez, G.; Franco-Villafañe, J. A.; Méndez-Sánchez, R. A.
2016-01-01
Coherent transport phenomena are difficult to observe due to several sources of decoherence. For instance, in the electronic transport through quantum devices the thermal smearing and dephasing, the latter induced by inelastic scattering by phonons or impurities, destroy phase coherence. In other wave systems, the temperature and dephasing may not destroy the coherence and can then be used to observe the underlying wave behaviour of the coherent phenomena. Here, we observe coherent transmission of mechanical waves through a two-dimensional elastic Sinai billiard with two waveguides. The flexural-wave transmission, performed by non-contact means, shows the quantization when a new mode becomes open. These measurements agree with the theoretical predictions of the simplest model highlighting the universal character of the transmission fluctuations. PMID:27121226
Ultrabroadband coherent supercontinuum frequency comb
Energy Technology Data Exchange (ETDEWEB)
Ruehl, Axel; McKay, Hugh; Thomas, Brian; Dong, Liang; Fermann, Martin E.; Hartl, Ingmar [IMRA America Inc., 1044 Woodridge Avenue, Ann Arbor, Michigan 48105 (United States); Martin, Michael J.; Cossel, Kevin C.; Chen Lisheng; Benko, Craig; Ye Jun [JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, 440 UCB, Boulder, Colorado 80309 (United States); Dudley, John M. [Institute FEMTO-ST, CNRS-University of Franche-Comte UMR 6174, Besancon (France)
2011-07-15
We present detailed studies of the coherence properties of an ultrabroadband supercontinuum, enabled by a comprehensive approach involving continuous-wave laser sources to independently probe both the amplitude and phase noise quadratures across the entire spectrum. The continuum coherently spans more than 1.5 octaves, supporting Hz-level comparison of ultrastable lasers at 698 nm and 1.54 {mu}m. We present a complete numerical simulation of the accumulated comb coherence in the limit of many pulses, in contrast to the single-pulse level, with systematic experimental verification. The experiment and numerical simulations reveal the presence of quantum-seeded broadband amplitude noise without phase coherence degradation, including the discovery of a dependence of the supercontinuum coherence on the fiber fractional Raman gain.
Seismic coherent states and ray geometrical spreading
Thomson, C. J.
2001-02-01
The coherent-state transform (CST) is essentially a Gaussian-windowed Fourier transform and it yields a combined slowness-position (p,x) domain representation of seismic wavefields. Several forms of the inverse CST exist and the set of `coherent states' form an overcomplete basis for wave analysis, in many ways similar to modern wavelets. The asymptotic or `ray' solution to the CST of the seismic wave equation involves a phase function S(p,x) that is complex due to the Gaussian decay. Hence one must consider complex rays, as well as a higher-dimensional phase space (p,x,∂pS,∂xS) corresponding to the extended configuration or base space (p,x). The initial conditions and geometrical spreading of these rays involve generalizations of standard procedures, exemplified by analysis of the coherent states excited by a ray theory incident wavefield. Surfaces of constant S are `tangential' to the standard ray theory wavefront T(x) and the Maslov phase fronts given by the Legendre transformation of T. Hence the real rays of T (and the Maslov phase) are particular rays of S. The geometrical spreading of an individual coherent-state (CS) wavefield requires careful consideration. Although the transport equation involves divergence in the higher-dimensional base space (p,x), Smirnov's Lemma applied in this space still gives the solution. The incorporation of initial conditions is correspondingly intricate, but the final spreading function is better behaved (`smoother') than either a standard ray or Maslov theory amplitude. This provides a solution to the problem of pseudo-caustics. The task of finding a `KMAH index' for each ray contributing to the inverse CST is simplified to choosing a complex square root that is smoothly connected between these rays (i.e. it does not fork). It is suggested that in practice only real rays are needed and then the method can be reduced to a smoothed form of the Maslov Snell wave sum representation. This is achieved by approximating the
Origin of long-lived coherence and excitation dynamics in pigment-protein complexes
Zhang, Zhedong
2015-01-01
We uncover the mechanism of long-lived coherence that the discrete vibrational modes effectively weaken the exciton-environment interaction. This subsequently demonstrates the role of vibrational coherence which greatly contributes to long-lived feature of the excitonic coherence that has been observed in femtosecond experiments. To test the validity of our effective theory, we study the pigment-protein complex in details by exploring the energy transfer and coherence dynamics. The ground-state coherence generated by incoherent radiations is demonstrated to be significant to promote the excitation energy transfer. This on the other hand, seems to be natural from the point of view of nonequilibriumness, which funnels the downhill immigration of excitons. Moreover we also confirm that the considerable improvement of energy transfer is always accompanied by the long-lived oscillation of coherence.
International Nuclear Information System (INIS)
Graphical abstract: Temporal behaviors due to quantum mechanical interferences between the nonadiabatically coupled quasi-degenerate excited states (b and c) after a coherent excitation. Highlights: ► A nonadiabatic theory of quasi-degenerate π-electronic states in aromatic molecules. ► Quantum interferences between the nonadiabatically-coupled π-electronic states. ► Analysis of time-dependent vibrational coherence transfer via nonadiabatic couplings. - Abstract: Results of a theoretical study of ultrafast coherent dynamics of nonadiabatically coupled quasi-degenerate π-electronic excited states of molecules were presented. Analytical expressions for temporal behaviors of population and vibrational coherence were derived using a simplified model to clarify the quantum mechanical interferences between the two coherently excited electronic states, which appeared in the nuclear wavepacket simulations [M. Kanno, H. Kono, Y. Fujimura, S.H. Lin, Phys. Rev. Lett 104 (2010) 108302]. The photon-polarization direction of the linearly polarized laser, which controls the populations of the two quasi-degenerate electronic states, determines constructive or destructive interference. Features of the vibrational coherence transfer between the two coupled quasi-electronic states through nonadiabatic couplings are also presented. Information on both the transition frequency and nonadiabatic coupling matrix element between the two states can be obtained by analyzing signals of two kinds of quantum beats before and after transfer through nonadiabatic coupling.
On gl((⌒)2｜2)(2)k Current Superalgebra and Twisted Conformal Field Theory
Institute of Scientific and Technical Information of China (English)
DING Xiang-Mao; WANG Gui-Dong; WANG Shi-Kun
2007-01-01
Motivated by the recently discovered hidden symmetry of the type ∏B Green-Schwarz superstring on certain background, the non-semisimple Kac-Moody twisted superalgebra gl((⌒)2|2)(2)k is investigated by means of the vector coherent state method and boson-fermion realization. The free field realization of the twisted current superalgebra at general level k is constructed. The corresponding Conformal Field Theory (CFT) has zero central charge. According to the classification theory, this CFT is a nonunitary field theory. After projecting out a U(1) factor and an outer automorphism operator, we get the free field representation of psl((⌒)2|2)(2)k, which is the algebra of gl((⌒)2|2)(2)k modulo the Z4-outer automorphism, the CFT has central charge -2.
Set shifting, central coherence and starvation in eating disorders
McConnellogue, D. M.
2012-01-01
Aims: This review aims to evaluate and synthesise previous research on set shifting in eating disorders in order to determine whether individuals with eating disorders have impaired set shifting. It also aims to determine whether set shifting difficulties are a risk factor for eating disorders or a consequence of starvation. Method: A summary and critique of the 13 papers specifically exploring set shifting in eating disorders is presented and followed by a synthesis of the results. Results: ...
Coherent quantum trasport in ferromagnet-superconductor-ferromagnet graphene junctions
Directory of Open Access Journals (Sweden)
M Salehi
2010-09-01
Full Text Available In this paper, we investigate the coherent quantum transport in grapheme-based ferromagnet-superconductor-ferromagent junctions within the framework of BCS theory using DBdG quasiparticles equation .The coherency with the finite size of superconductor region has two characteristic features subgap electron transport and oscillations of differential conductance. we show that periodic vanishing of the Andreev reflection at the energies called geometrical resonances above the superconducting gap is a striking consequence of quasiparticles interference. We suggest to make devices that produce polarized spin-current with possible applications in spintronics.
Two-pion interferometry for a partially coherent evolution source
Institute of Scientific and Technical Information of China (English)
LI Jian-Wei; YU Li-Li; ZHANG Wei-Ning
2008-01-01
We give the formulas of two-pion Hanbury-Brown-Twiss (HBT) correlation function for a partially coherent evolution pion-emitting source,using quantum probability amplitudes in a path-integral formalism.The multiple scattering of the particles in the source is taken into consideration based on Glauber scattering theory.Two-pion interferometry with effects of the multiple scattering and source collective expansion is examined for a partially coherent source of hadronic gas with a finite baryon density and evolving hydrodynamically.We do not find observable effect of either the multiple scattering or the source collective expansion on HBT chaotic parameter.
Institute of Scientific and Technical Information of China (English)
洪明; 徐艳霞
2015-01-01
语篇局部注意焦点保持与更新及其指称形式的选择是影响语篇局部连贯性的两个重要方面。本文运用基于向心理论的四项原则分析法，对中国高校英语专业四级、八级考试的作文语料进行对比分析，从局部注意焦点及其指称形式等两个方面分析不同年级作文的局部连贯特征差异，从而分析不同年级学生局部连贯能力的发展性特征。研究发现，随着整体语言能力的提升，学生的局部注意焦点的保持能力有所增长，并且正确运用代词和定冠词的能力也随之提高。%Retaining or shifting of the local focus of attention in a discourse and its choice of referring ex-pressions are two important factors which may affect the local coherence in that discourse .By making a com-parative analysis of the two factors mentioned above between TEM 4 and TEM8 compositions of Chinese univer-sity English majors and by applying Four Principle Model based on Centering Theory , the study tends to ex-plore differences in local coherence features between the compositions at different levels , which helps find out the developmental features of students ’ ability in achieving local coherence .Results show that as students ’ language proficiency improves , their ability of retaining the local focus of attention develops , and their ability of using properly pronouns and definite articles improves as well .
International workshop on phase retrieval and coherent scattering. Coherence 2005
International Nuclear Information System (INIS)
The contributions of the participants have been organized into 3 topics: 1) phase retrieval methods, 2) X-ray photon correlation spectroscopy, and 3) coherent diffraction imaging. This document gathers the abstracts of the presentations and of the posters
International workshop on phase retrieval and coherent scattering. Coherence 2005
Energy Technology Data Exchange (ETDEWEB)
Nugent, K.A.; Fienup, J.R.; Van Dyck, D.; Van Aert, S.; Weitkamp, T.; Diaz, A.; Pfeiffer, F.; Cloetens, P.; Stampanoni, M.; Bunk, O.; David, C.; Bronnikov, A.V.; Shen, Q.; Xiao, X.; Gureyev, T.E.; Nesterets, Ya.I.; Paganin, D.M.; Wilkins, S.W.; Mokso, R.; Cloetens, P.; Ludwig, W.; Hignette, O.; Maire, E.; Faulkner, H.M.L.; Rodenburg, J.M.; Wu, X.; Liu, H.; Grubel, G.; Ludwig, K.F.; Livet, F.; Bley, F.; Simon, J.P.; Caudron, R.; Le Bolloc' h, D.; Moussaid, A.; Gutt, C.; Sprung, M.; Madsen, A.; Tolan, M.; Sinha, S.K.; Scheffold, F.; Schurtenberger, P.; Robert, A.; Madsen, A.; Falus, P.; Borthwick, M.A.; Mochrie, S.G.J.; Livet, F.; Sutton, M.D.; Ehrburger-Dolle, F.; Bley, F.; Geissler, E.; Sikharulidze, I.; Jeu, W.H. de; Lurio, L.B.; Hu, X.; Jiao, X.; Jiang, Z.; Lurio, L.B.; Hu, X.; Jiao, X.; Jiang, Z.; Naryanan, S.; Sinha, S.K.; Lal, J.; Naryanan, S.; Sinha, S.K.; Lal, J.; Robinson, I.K.; Chapman, H.N.; Barty, A.; Beetz, T.; Cui, C.; Hajdu, J.; Hau-Riege, S.P.; He, H.; Stadler, L.M.; Sepiol, B.; Harder, R.; Robinson, I.K.; Zontone, F.; Vogl, G.; Howells, M.; London, R.; Marchesini, S.; Shapiro, D.; Spence, J.C.H.; Weierstall, U.; Eisebitt, S.; Shapiro, D.; Lima, E.; Elser, V.; Howells, M.R.; Huang, X.; Jacobsen, C.; Kirz, J.; Miao, H.; Neiman, A.; Sayre, D.; Thibault, P.; Vartanyants, I.A.; Robinson, I.K.; Onken, J.D.; Pfeifer, M.A.; Williams, G.J.; Pfeiffer, F.; Metzger, H.; Zhong, Z.; Bauer, G.; Nishino, Y.; Miao, J.; Kohmura, Y.; Yamamoto, M.; Takahashi, Y.; Koike, K.; Ebisuzaki, T.; Ishikawa, T.; Spence, J.C.H.; Doak, B
2005-07-01
The contributions of the participants have been organized into 3 topics: 1) phase retrieval methods, 2) X-ray photon correlation spectroscopy, and 3) coherent diffraction imaging. This document gathers the abstracts of the presentations and of the posters.
The linac coherent light source
International Nuclear Information System (INIS)
The Linac Coherent Light Source is a self-amplified spontaneous emission based free electron laser to be built at the Stanford Linear Accelerator Centre by a multi-laboratory collaboration. This facility will provide ultra-short pulses of coherent X-ray radiation with the fundamental harmonic energy tuneable over the energy range of 0.82 to 8.2 keV. In addition to the coherent X-ray radiation, which will have an extremely high peak and average brightness, a continuous spectrum of spontaneous synchrotron radiation (SR) of high brightness will also be produced. The characteristics of the LCLS and its associated radiological issues are discussed. (authors)
Coherent control of quantum dots
DEFF Research Database (Denmark)
Johansen, Jeppe; Lodahl, Peter; Hvam, Jørn Märcher
In recent years much effort has been devoted to the use of semiconductor quantum dotsystems as building blocks for solid-state-based quantum logic devices. One importantparameter for such devices is the coherence time, which determines the number ofpossible quantum operations. From earlier...... measurements the coherence time of the selfassembledquantum dots (QDs) has been reported to be limited by the spontaneousemission rate at cryogenic temperatures1.In this project we propose to alter the coherence time of QDs by taking advantage of arecent technique on modifying spontaneous emission rates with...
Photoelectric devices with quantum coherence
Shanhe, Su
A phtotoelectric device consisting of a three-level system contacted with two fermionic baths and a photon bath is built. Making the Born-Markov approximation, the equation of motion for the density operator in a Lindblad-like form is derived. We obtain the coherence and the efficiency of the system under the steady-state condition. Results show that quantum coherence can enhance the photoelectric conversion efficiency. The efficiency at maximum power can be larger than the CA efficiency bound with the existence of coherence.
Second harmonic optical coherence tomography
Jiang, Y; Wang, Y; Chen, Z; Jiang, Yi; Tomov, Ivan; Wang, Yimin; Chen, Zhongping
2004-01-01
Second harmonic optical coherence tomography, which uses coherence gating of second-order nonlinear optical response of biological tissues for imaging, is described and demonstrated. Femtosecond laser pulses were used to excite second harmonic waves from collagen harvested from rat tail tendon and a reference nonlinear crystal. Second harmonic interference fringe signals were detected and used for image construction. Because of the strong dependence of second harmonic generation on molecular and tissue structures, this technique offers contrast and resolution enhancement to conventional optical coherence tomography.
Coherent-mode decomposition of partially polarized, partially coherent sources
Gori, Franco; Santarsiero, Massimo; Simon, Raja; Piquero, Gemma; Borghi, Riccardo; Guattari, Giorgio
2003-01-01
It is shown that any partially polarized, partially coherent source can be expressed in terms of a suitable superposition of transverse coherent modes with orthogonal polarization states. Such modes are determined through the solution of a system of two coupled integral equations. An example, for which the modal decomposition is obtained in closed form in terms of fully linearly polarized Hermite Gaussian modes, is given.
Directory of Open Access Journals (Sweden)
Marcin Overgaard Ptaszynski
2011-10-01
Full Text Available
Abstract: The aim of this article is to contribute to the development of the modern theory of lexi-cographical functions by offering a critical examination of the following concepts associated with it: primary needs, primary data, secondary needs, secondary data, function-related needs, and function-related data. By way of introduction, a presentation of the basic tenets of the theory is offered, followed by a description of the gen-eral characteristics of secondary needs and data. Next, on the basis of both a critical analysis of the theory and an examination of selected data types in existing lexicographical products, it is argued that all user needs and all data that satisfy those needs are function-related. The distinction between the concepts function-related and usage-related is thus rejected. Since this has serious implications for the relation between secondary needs and data on the one hand and primary needs and data on the other, this relation is subsequently reconsid-ered. This leads to a redefinition of all the concepts examined. It is also explained why an ideal state of lexico-graphy, where secondary needs and data do not exist, cannot be achieved in the real world.
Keywords: DICTIONARY, LEXICOGRAPHY, LEXICOGRAPHICAL FUNCTION, PRIMARY NEED, PRIMARY DATA, SECONDARY NEED, SECONDARY DATA, FUNCTION-RELATED NEED, FUNCTION-RELATED DATA, EXTRA-LEXICOGRAPHICAL SITUATION, INTRA-LEXICOGRAPHICAL SITUATION, COMMUNICATIVE FUNCTION, COGNITIVE FUNCTION, OPERATIVE FUNCTION, TEXT RECEPTION, TEXT PRODUCTION, TRANSLATION
Opsomming: Funksieverwante sekondêre gebruikersbehoeftes en sekon-dêre data? 'n Kritiese ondersoek na 'n aantal kernbegrippe in die moderne teorie van leksikografiese funksies. Die doel van hierdie artikel is om by te dra tot die ontwikkeling van die moderne teorie van leksikografiese funksies deur 'n kritiese ondersoek aan te bied van die volgende begrippe wat daarmee verbind word: primêre behoeftes, primêre data
Transient quantum coherent response to a partially coherent radiation field
Energy Technology Data Exchange (ETDEWEB)
Sadeq, Zaheen S.; Brumer, Paul, E-mail: pbrumer@chem.utoronto.ca [Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)
2014-02-21
The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turn-on and pulsed turn-on effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal “toy” model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.
[Optical coherence tomography].
von Braunmühl, T
2015-07-01
Optical coherence tomography (OCT) was introduced in the 1990s in dermatology and is nowadays established as a noninvasive high-resolution technique for the in vivo evaluation of the skin. To date several studies have been successfully demonstrated the application of OCT for various dermatological questions. The main indication for OCT in the daily practice is the noninvasive diagnosis of nonmelanoma skin cancer such as actinic keratosis and basal cell carcinoma. OCT has also been shown to be a valuable tool in treatment monitoring and evaluation of therapeutic success of noninvasive treatment strategies like topical immune modulators or photodynamic treatment. Other potential applications for OCT include inflammatory diseases, microbial or parasitic infestations of the skin, e.g. scabies mites or onychomycosis. In recent years high-definition OCT devices have been developed that can potentially be used for the evaluation of melanocytic lesions and, due to the higher resolution, for the visualization of intrafollicular demodex mites. Furthermore different commercially available devices offer-in addition to the cross-sectional images-a fast-generated horizontal (en face) imaging mode. With respect to resolution and penetration depth the OCT technique is taking a middle position in comparison to other noninvasive imaging devices in dermatology such as sonography and reflectance confocal microscopy. PMID:25809459
Theory for upconversion of incoherent images
DEFF Research Database (Denmark)
Dam, Jeppe Seidelin; Pedersen, Christian; Tidemand-Lichtenberg, Peter
2012-01-01
Upconversion of images is a generic method for shifting the spectral content of entire images. A comprehensive theory for upconversion of incoherent light images is presented and compared against experiments. In particular we consider the important case for upconversion of infinity corrected light....... We show that the spatial resolution for upconversion of incoherent light images is better than for the corresponding coherent image upconversion case. The fundamental differences between upconversion of coherent and incoherent images are investigated theoretically and experimentally. The theory...
Land Reform and Land Consolidation in Central and Eastern Europe after 1989
DEFF Research Database (Denmark)
Hartvigsen, Morten B.
The countries in Central and Eastern Europe began a remarkable transition in 1989. Land reforms were high on the political agenda in most of the countries. In many countries in the region, land reforms have resulted in farm structures dominated by small and fragmented farms, which are not...... competitive in the globalized economy. Drawing on the classical theory on land fragmentation, this PhD study explores the coherence between the land reform approaches applied in 25 study countries and the outcome in form of farm structures and land fragmentation. Most of the Central and Eastern European...... countries have introduced land consolidation instruments to address the structural problems in agriculture. The PhD study analyses the experiences from introduction of land consolidation and land banking instruments and provides the first full overview of the experiences achieved. While land consolidation...
The density matrix picture of laser coherent control current
Institute of Scientific and Technical Information of China (English)
SHOU Qian; ZHANG Haichao; LIU Luning; LIN Weizhu
2004-01-01
The physical substance of the coherent control current and the optical rectification have been analyzed based on density matrix perturbation theory. The analytical results demonstrate that they arise from the real and virtual manifestations of the same nonlinear process associated with diagonal and non-diagonal density matrix.And in terms of polarization, they respectively arise from the intraband and interband polarizations. Both the evolution of the coherent control current exited by ultrafast laser pulse and its dependence on frequency have been studied in time and frequency domains. In order to get an explicit knowledge of intraband polarization and the origination of the coherent control current, we have investigated the initial photo-carriers momentum distribution. The ultrafast decay of the polar momentum population in order of tens of femtosends is given to illustrate its instantaneous optical response.
Novelty, coherence, and Mendeleev's periodic table.
Schindler, Samuel
2014-03-01
Predictivism is the view that successful predictions of "novel" evidence carry more confirmational weight than accommodations of already known evidence. Novelty, in this context, has traditionally been conceived of as temporal novelty. However temporal predictivism has been criticized for lacking a rationale: why should the time order of theory and evidence matter? Instead, it has been proposed, novelty should be construed in terms of use-novelty, according to which evidence is novel if it was not used in the construction of a theory. Only if evidence is use-novel can it fully support the theory entailing it. As I point out in this paper, the writings of the most influential proponent of use-novelty contain a weaker and a stronger version of use-novelty. However both versions, I argue, are problematic. With regard to the appraisal of Mendeleev' periodic table, the most contentious historical case in the predictivism debate, I argue that temporal predictivism is indeed supported, although in ways not previously appreciated. On the basis of this case, I argue for a form of so-called symptomatic predictivism according to which temporally novel predictions carry more confirmational weight only insofar as they reveal the theory's presumed coherence of facts as real. PMID:24984451
Coherent control of plasma dynamics
He, Z -H; Lebailly, V; Nees, J A; Krushelnick, K; Thomas, A G R
2015-01-01
Coherent control of a system involves steering an interaction to a final coherent state by controlling the phase of an applied field. Plasmas support coherent wave structures that can be generated by intense laser fields. Here, we demonstrate the coherent control of plasma dynamics in a laser wakefield electron acceleration experiment. A genetic algorithm is implemented using a deformable mirror with the electron beam signal as feedback, which allows a heuristic search for the optimal wavefront under laser-plasma conditions that is not known a priori. We are able to improve both the electron beam charge and angular distribution by an order of magnitude. These improvements do not simply correlate with having the `best' focal spot, since the highest quality vacuum focal spot produces a greatly inferior electron beam, but instead correspond to the particular laser phase that steers the plasma wave to a final state with optimal accelerating fields.
Coherent Control of Bond Making
Levin, Liat; Rybak, Leonid; Kosloff, Ronnie; Koch, Christiane P; Amitay, Zohar
2014-01-01
We demonstrate for the first time coherent control of bond making, a milestone on the way to coherent control of photo-induced bimolecular chemical reactions. In strong-field multiphoton femtosecond photoassociation experiments, we find the yield of detected magnesium dimer molecules to be enhanced for positively chirped pulses and suppressed for negatively chirped pulses. Our ab initio model shows that control is achieved by purification via Franck-Condon filtering combined with chirp-dependent Raman transitions. Experimental closed-loop phase optimization using a learning algorithm yields an improved pulse that utilizes vibrational coherent dynamics in addition to chirp-dependent Raman transitions. Our results show that coherent control of binary photo-reactions is feasible even under thermal conditions.
Superposed Coherent and Squeezed Light
Kassahun, Fesseha
2012-01-01
We first calculate the mean photon number and quadrature variance of superposed coherent and squeezed light, following a procedure of analysis based on combining the Hamiltonians and using the usual definition for the quadrature variance of superposed light beams. This procedure of analysis leads to physically unjustifiable mean photon number of the coherent light and quadrature variance of the superposed light. We then determine both of these properties employing a procedure of analysis base...
Does Measurement Necessarily Destroy Coherence?
Ghose, Partha
2011-01-01
It has been proposed that measurement in quantum mechanics results from spontaneous breaking of a symmetry of the measuring apparatus and could be a unitary process that preserves coherence. Viewed in this manner, it is argued, null result measurements should exhibit this coherence. The principle of a class of experiments that can be performed to test whether or not this is the case is proposed.
Diffusion Processes and Coherent States
Martino, S; De Siena, S.; Illuminati, F.; Vitiello, G.
1994-01-01
It is shown that stochastic processes of diffusion type possess, in all generality, a structure of uncertainty relations and of coherent and squeezed states. This fact is used to obtain, via Nelson stochastic formulation of quantum mechanics, the harmonic-oscillator coherent and squeezed states. The method allows to derive new minimum uncertainty states in time-dependent oscillator potentials and for the Caldirola-Kanai model of quantum damped oscillator.
Pseudo-Fermionic Coherent States
Cherbal, Omar; Drir, Mahrez
2009-01-01
We have generalized the fermionic coherent states to pseudo-fermion oscillator system. The system of coherent states constructed consist of two subsets, which are bi-normalized and bi-overcomplete. The two subsets are built up as eigenstates of two annihilation operators $b$ and $\\tilde{b} = \\eta b \\eta^{-1}$ of respectively $H$ and $H^+$ where $\\eta$ is the Hermitian and invertible operator that ensures the pseudo-Hermiticity of the Hamiltonian $H = \\eta^{-1} H^+ \\eta$
Unified theory of effective interaction
Takayanagi, Kazuo
2016-09-01
We present a unified description of effective interaction theories in both algebraic and graphic representations. In our previous work, we have presented the Rayleigh-Schrödinger and Bloch perturbation theories in a unified fashion by introducing the main frame expansion of the effective interaction. In this work, we start also from the main frame expansion, and present various nonperturbative theories in a coherent manner, which include generalizations of the Brandow, Brillouin-Wigner, and Bloch-Horowitz theories on the formal side, and the extended Krenciglowa-Kuo and the extended Lee-Suzuki methods on the practical side. We thus establish a coherent and comprehensive description of both perturbative and nonperturbative theories on the basis of the main frame expansion.
Coherent communication with continuous quantum variables
International Nuclear Information System (INIS)
The coherent bit (cobit) channel is a resource intermediate between classical and quantum communication. It produces coherent versions of teleportation and superdense coding. We extend the cobit channel to continuous variables by providing a definition of the coherent nat (conat) channel. We construct several coherent protocols that use both a position-quadrature and a momentum-quadrature conat channel with finite squeezing. Finally, we show that the quality of squeezing diminishes through successive compositions of coherent teleportation and superdense coding
Ronconi, Luca; Gori, Simone; Ruffino, Milena; Franceschini, Sandro; Urbani, Barbara; Molteni, Massimo; Facoetti, Andrea
2012-01-01
Autism spectrum disorder (ASD) has been associated with decreased coherent dot motion (CDM) performance, a task that measures magnocellular sensitivity as well as fronto-parietal attentional integration processing. In order to clarify the role of spatial attention in CDM tasks, we measured the perception of coherently moving dots displayed in the central or peripheral visual field in ASD and typically developing children. A dorsal-stream deficit in children with ASD should predict a generally...
Control of Coherent Instabilities by Linear Coupling
Cappi, R; Möhl, D
2001-01-01
One of the main challenges in the design of high-energy colliders is the very high luminosity necessary to provide significant event rates. This imposes strong constraints to achieve and preserve beams of high brightness, i.e. intensity to emittance ratio, all along the injector chain. Amongst the phenomena that can blow up and even destroy the beam are transverse coherent instabilities. Two methods are widely used to damp these instabilities. The first one is Landau damping by non-linearities. The second consists in using an electronic feedback system. However, non-linearities are harmful to single-particle motion due to resonance phenomena, and powerful wideband feedback systems are expensive. It is shown in this paper that linear coupling is a further method that can be used to damp transverse coherent instabilities. The theory of collective motion is outlined, including the coupling of instability rise and damping rates, chromaticity and Landau damping. Experimental results obtained at the CERN PS are rep...
Lagrangian based methods for coherent structure detection
International Nuclear Information System (INIS)
There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We present a review of four approaches and demonstrate the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other two approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also present a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows
Lagrangian based methods for coherent structure detection
Energy Technology Data Exchange (ETDEWEB)
Allshouse, Michael R., E-mail: mallshouse@chaos.utexas.edu [Center for Nonlinear Dynamics and Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); Peacock, Thomas, E-mail: tomp@mit.edu [Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
2015-09-15
There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We present a review of four approaches and demonstrate the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other two approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also present a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows.
Directory of Open Access Journals (Sweden)
Peter Karlsudd
2008-09-01
Full Text Available This article describes a learning system constructed to facilitate teaching and learning by creating a functional web-based contact between schools and organisations which in cooperation with the school contribute to pupils’/students’ cognitive development. Examples of such organisations include science centres, museums, art and music workshops and teacher education internships. With the support of the “Web Coherence Learning” IT application (abbreviated in Swedish to Webbhang developed by the University of Kalmar, the aim is to reinforce learning processes in the encounter with organisations outside school. In close cooperation with potential users a system was developed which can be described as consisting of three modules. The first module, “the organisation page” supports the organisation in simply setting up a homepage, where overarching information on organisation operations can be published and where functions like calendar, guestbook, registration and newsletter can be included. In the second module, “the activity page” the activities offered by the organisation are described. Here pictures and information may prepare and inspire pupils/students to their own activities before future visits. The third part, “the participant page” is a communication module linked to the activity page enabling school classes to introduce themselves and their work as well as documenting the work and communicating with the educators responsible for external activities. When the project is finished, the work will be available to further school classes, parents and other interested parties. System development and testing have been performed in a small pilot study where two creativity educators at an art museum have worked together with pupils and teachers from a compulsory school class. The system was used to establish, prior to the visit of the class, a deeper contact and to maintain a more qualitative continuous dialogue during and after
Purposeful Program Theory: Effective Use of Theories of Change and Logic Models
Funnell, Sue C.; Rogers, Patricia J.
2011-01-01
Between good intentions and great results lies a program theory--not just a list of tasks but a vision of what needs to happen, and how. Now widely used in government and not-for-profit organizations, program theory provides a coherent picture of how change occurs and how to improve performance. "Purposeful Program Theory" shows how to develop,…
Coherent Patterns in Nuclei and in Financial Markets
Drozdz, S; Speth, J
2010-01-01
In the area of traditional physics the atomic nucleus belongs to the most complex systems. It involves essentially all elements that characterize complexity including the most distinctive one whose essence is a permanent coexistence of coherent patterns and of randomness. From a more interdisciplinary perspective, these are the financial markets that represent an extreme complexity. Here, based on the matrix formalism, we set some parallels between several characteristics of complexity in the above two systems. We, in particular, refer to the concept - historically originating from nuclear physics considerations - of the random matrix theory and demonstrate its utility in quantifying characteristics of the coexistence of chaos and collectivity also for the financial markets. In this later case we show examples that illustrate mapping of the matrix formulation into the concepts originating from the graph theory. Finally, attention is drawn to some novel aspects of the financial coherence which opens room for s...
DEFF Research Database (Denmark)
Wang, W.; Duan, Z.H.; Hanson, Steen Grüner;
2006-01-01
By controlling the irradiance of an extended quasimonochromatic, spatially incoherent source, an optical field is generated that exhibits spatial coherence with phase singularities, called coherence vortices. A simple optical geometry for direct visualization of coherence vortices is proposed, and...
Central simple Poisson algebras
Institute of Scientific and Technical Information of China (English)
SU; Yucai; XU; Xiaoping
2004-01-01
Poisson algebras are fundamental algebraic structures in physics and symplectic geometry. However, the structure theory of Poisson algebras has not been well developed. In this paper, we determine the structure of the central simple Poisson algebras related to locally finite derivations, over an algebraically closed field of characteristic zero.The Lie algebra structures of these Poisson algebras are in general not finitely-graded.
Coherent distributions for the rigid rotator
Grigorescu, Marius
2016-06-01
Coherent solutions of the classical Liouville equation for the rigid rotator are presented as positive phase-space distributions localized on the Lagrangian submanifolds of Hamilton-Jacobi theory. These solutions become Wigner-type quasiprobability distributions by a formal discretization of the left-invariant vector fields from their Fourier transform in angular momentum. The results are consistent with the usual quantization of the anisotropic rotator, but the expected value of the Hamiltonian contains a finite "zero point" energy term. It is shown that during the time when a quasiprobability distribution evolves according to the Liouville equation, the related quantum wave function should satisfy the time-dependent Schrödinger equation.
Enhanced coherent Raman emission from uniform plasmas
International Nuclear Information System (INIS)
A mechanism for the coherent emission of radio and microwaves from a warm uniform plasma is proposed. The output power from this mechanism appears to have the characteristics of a classical parametric amplification process. An earlier kinetic theory model for radiation by the scattering of plasma waves in a homogeneous plasma is revamped and modified to incorporate the dominant role of longitudinal Rayleigh scattered waves which stimulate the emission of transverse combination radiation (sum and difference of impressed and natural frequencies) by the resonant Raman scattering process in the plasma. This results in intense radio or microwave radiation at approximately twice the plasma frequency, the intensity depending upon plasma parameters. This intensity, its angular pattern, and the threshold condition for its enhanced emission are calculated. Comparisons of the computed results with the laboratory observation of the radiation output from dc discharges in argon gas, and from a helium theta-pinch plasma are made. Both qualitative and quantitative agreement are found
Spatial coherences of the sound pressure and the particle velocity in underwater ambient noise
Institute of Scientific and Technical Information of China (English)
YAN Jin; LUO Xianzhi; HOU Chaohuan
2007-01-01
The spatial coherences were investigated between the sound pressure and the three orthogonal components of the particle velocity in underwater ambient noise. Based on the ray theory, integral expression was derived for the spatial coherence matrix of the sound pressure and the particle velocity in a stratified ocean with dipole noise sources homogenously distributed on the surface. The integrand includes a multiplying factor of the vertical directivity of the noise intensity, and the layered ocean environment affects the spatial coherences via this directivity factor. For a shallow water environment and a semi-infinite homogenous medium, the coherence calculation results were given. It was showed that the sound speed profile and the sea bottom could not be neglected in determining the spatial coherences of the ambient noise vector field.
Coherence and measurement in quantum thermodynamics.
Kammerlander, P; Anders, J
2016-01-01
Thermodynamics is a highly successful macroscopic theory widely used across the natural sciences and for the construction of everyday devices, from car engines to solar cells. With thermodynamics predating quantum theory, research now aims to uncover the thermodynamic laws that govern finite size systems which may in addition host quantum effects. Recent theoretical breakthroughs include the characterisation of the efficiency of quantum thermal engines, the extension of classical non-equilibrium fluctuation theorems to the quantum regime and a new thermodynamic resource theory has led to the discovery of a set of second laws for finite size systems. These results have substantially advanced our understanding of nanoscale thermodynamics, however putting a finger on what is genuinely quantum in quantum thermodynamics has remained a challenge. Here we identify information processing tasks, the so-called projections, that can only be formulated within the framework of quantum mechanics. We show that the physical realisation of such projections can come with a non-trivial thermodynamic work only for quantum states with coherences. This contrasts with information erasure, first investigated by Landauer, for which a thermodynamic work cost applies for classical and quantum erasure alike. Repercussions on quantum work fluctuation relations and thermodynamic single-shot approaches are also discussed. PMID:26916503
Coherence and measurement in quantum thermodynamics
Kammerlander, P.; Anders, J.
2016-02-01
Thermodynamics is a highly successful macroscopic theory widely used across the natural sciences and for the construction of everyday devices, from car engines to solar cells. With thermodynamics predating quantum theory, research now aims to uncover the thermodynamic laws that govern finite size systems which may in addition host quantum effects. Recent theoretical breakthroughs include the characterisation of the efficiency of quantum thermal engines, the extension of classical non-equilibrium fluctuation theorems to the quantum regime and a new thermodynamic resource theory has led to the discovery of a set of second laws for finite size systems. These results have substantially advanced our understanding of nanoscale thermodynamics, however putting a finger on what is genuinely quantum in quantum thermodynamics has remained a challenge. Here we identify information processing tasks, the so-called projections, that can only be formulated within the framework of quantum mechanics. We show that the physical realisation of such projections can come with a non-trivial thermodynamic work only for quantum states with coherences. This contrasts with information erasure, first investigated by Landauer, for which a thermodynamic work cost applies for classical and quantum erasure alike. Repercussions on quantum work fluctuation relations and thermodynamic single-shot approaches are also discussed.
Institute of Scientific and Technical Information of China (English)
曾阳发; 李彬彬; 黄国富; 李月桃; 何明光
2009-01-01
目的 探讨眼前段光学相干断层扫描技术(anteriorsegment optical coherence tomography,AS-OCT)和A型超声波生物测量技术(A超)测量,中央角膜厚度(central corneal thickness,CCT)和前房深度(anterior chamber depth,ACD)的异同.方法 分别采用AS-OCT和A超测量33名(54只眼)正常人的CCT和ACD,分别采用配对t检验、Pearson相关和Bland-Altman方法,分析两种仪器的测量值的差异、相关性和一致性.结果 A超与AS-OCT的CCT值分别为(524.41±23.24)μm、(513.37±22.71)μm,之间的差异有统计学意义(t=15.906,P=0.000),差值均数为(11.04±5.10)μm.两种仪器的CCT值正相关(r=0.976,P=0.000).95%LoA(95% Limts of Agreement)为(-21.03,-1.04)μm,95%LoA的区间范围为19.99μm,为A超CCT平均值的3.81%.A超与AS-OCT的ACD值分别为(2.89±0.29)mm、(3.18±0.26)mm,之间的差异有统计学意义(f=-12.052,P=0.000),差值的均数为(-0.29±0.17)mm.两种仪器的ACD值相关(r=0.803,P=0.000).95%LoA为(-0.63,-0.06)mm,95%LoA的区间范围为0.57mm,为A超ACD平均值的19.72%.结论 AS-OCT的CCT值和ACD值与A超的测量值相关.与A超相比,AS-OCT的CCT测量值更小,而ACD值更大.两种仪器测量CCT的一致性比ACD高.%Objective To assess central corneal thickness(CCT)and anterior chamber depth (ACD) measurements with anterior segment optical coherence tomography (AS-OCT)comparing with A-scan ultrasonography (A-scan US).Methods 54 eyes of 33 normal subjects were enrolled in the study.CCT and ACD were measured using AS-OCT and A-scan US.The measurements of two instruments were analyzed using paired t test,Pearson correlation and Bland-Altman plot,respectively.Results The CCT of AS-OCT and A-scan US were 524.41± 23.24 microm and 513.37± 22.7 microm,respectively.The CCT values measured by A-scan US were significantly greater than AS-OCT, paired difference was 11.04± 5.10 microm (t =15.906, P =0.000).There were a significantly correlation between CCTs value of two instruments (r =0
Coherent optical control of polarization with a critical metasurface
Kang, Ming; Y. D. Chong
2015-01-01
We describe the mechanism by which a metamaterial surface can act as an ideal phase-controlled rotatable linear polarizer. With equal-power linearly polarized beams incident on each side of the surface, varying the relative phase rotates the polarization angles of the output beams, while keeping the polarization exactly linear. The explanation is based on coupled-mode theory and the idea of coherent perfect absorption into auxiliary polarization channels. The polarization-rotating behavior oc...
Solar axion experiments using coherent Primakoff conversion in single crystals
International Nuclear Information System (INIS)
The results of a 1.94 kg · y pilot search for solar axions with an ultralow background Ge detector are reviewed. The detection method is based on Bragg-coherent Primakoff conversion of axions into photons when the momentum vectors of the axion and photon satisfy the Bragg condition. The theory of the experiment are presented for Ge and Te02 crystals. Future prospects of large volume experiments are discussed
Coherent propagation of waves in random media with weak nonlinearity
Wellens, Thomas; Gremaud, Benoit
2009-01-01
We develop a diagrammatic theory for transport of waves in disordered media with weak nonlinearity. We first represent the solution of the nonlinear wave equation as a nonlinear Born series. From this, we construct nonlinear ladder and crossed diagrams for the average wave intensity. Then, we sum up the diagrammatic series completely, i.e. nonperturbatively in the strength of the nonlinearity, and thereby obtain integral equations describing both nonlinear diffusive transport and coherent bac...
Many-Body Aspects of Coherent Atom-Molecule Oscillations
Duine, R. A.; Stoof, H. T. C.
2003-01-01
We study the many-body effects on coherent atom-molecule oscillations by means of an effective quantum field theory that describes Feshbach-resonant interactions in Bose gases in terms of an atom-molecule hamiltonian. We determine numerically the many-body corrections to the oscillation frequency for various densities of the atomic condensate. We also derive an analytic expression that approximately describes both the density and magnetic-field dependence of this frequency near the resonance....
On the Dual Representation of Coherent Risk Measures
Ang, Marcus; Sun, Jie; Yao, Qiang
2015-01-01
A classical result in risk measure theory states that every coherent risk measure has a dual representation as the supremum of certain expected value over a risk envelope. We study this topic in more detail. The related issues include: 1. Set operations of risk envelopes and how they change the risk measures, 2. The structure of risk envelopes of popular risk measures, 3. Aversity of risk measures and its impact to risk envelopes, and 4. A connection between risk measures in stochastic optimi...
Flux tubes and coherence length in the SU(3) vacuum
Cea, Paolo; Cosmai, Leonardo; Cuteri, Francesca; Papa, Alessandro
2013-01-01
An estimate of the London penetration and coherence lengths in the vacuum of the SU(3) pure gauge theory is given downstream an analysis of the transverse profile of the chromoelectric flux tubes. Within ordinary superconductivity, a simple variational model for the magnitude of the normalized order parameter of an isolated vortex produces an analytic expression for magnetic field and supercurrent density. In the picture of SU(3) vacuum as dual superconductor, this expression provides us with...
Coherence measures for heralded single-photon sources
Bocquillon, E.; Couteau, C.; Razavi, M.; Laflamme, R.; Weihs, G.
2008-01-01
Single-photon sources (SPSs) are mainly characterized by the minimum value of their second-order coherence function, viz. their $g^{(2)}$ function. A precise measurement of $g^{(2)}$ may, however, require high time-resolution devices, in whose absence, only time-averaged measurements are accessible. These time-averaged measures, standing alone, do not carry sufficient information for proper characterization of SPSs. Here, we develop a theory, corroborated by an experiment, that allows us to s...
Physics-Based Predictions for Coherent Change Detection Using X-Band Synthetic Aperture Radar
Directory of Open Access Journals (Sweden)
Mark Preiss
2005-12-01
Full Text Available A theoretical model is developed to describe the interferometric coherency between pairs of SAR images of rough soil surfaces. The model is derived using a dyadic form for surface reflectivity in the Kirchhoff approximation. This permits the combination of Kirchhoff theory and spotlight synthetic aperture radar (SAR image formation theory. The resulting model is used to describe the interferometric coherency between pairs of SAR images of rough soil surfaces. The theoretical model is applied to SAR images formed before and after surface changes observed by a repeat-pass SAR system. The change in surface associated with a tyre track following vehicle passage is modelled and SAR coherency estimates are obtained. Predicted coherency distributions for both the change and no-change scenarios are used to estimate receiver operator curves for the detection of the changes using a high-resolution, X-band SAR system.
Coherent Waves in Seismic Researches
Emanov, A.; Seleznev, V. S.
2013-05-01
Development of digital processing algorithms of seismic wave fields for the purpose of useful event picking to study environment and other objects is the basis for the establishment of new seismic techniques. In the submitted paper a fundamental property of seismic wave field coherence is used. The authors extended conception of coherence types of observed wave fields and devised a technique of coherent component selection from observed wave field. Time coherence and space coherence are widely known. In this paper conception "parameter coherence" has been added. The parameter by which wave field is coherent can be the most manifold. The reason is that the wave field is a multivariate process described by a set of parameters. Coherence in the first place means independence of linear connection in wave field of parameter. In seismic wave fields, recorded in confined space, in building-blocks and stratified mediums time coherent standing waves are formed. In prospecting seismology at observation systems with multiple overlapping head waves are coherent by parallel correlation course or, in other words, by one measurement on generalized plane of observation system. For detail prospecting seismology at observation systems with multiple overlapping on basis of coherence property by one measurement of area algorithms have been developed, permitting seismic records to be converted to head wave time sections which have neither reflected nor other types of waves. Conversion in time section is executed on any specified observation base. Energy storage of head waves relative to noise on basis of multiplicity of observation system is realized within area of head wave recording. Conversion on base below the area of wave tracking is performed with lack of signal/noise ratio relative to maximum of this ratio, fit to observation system. Construction of head wave time section and dynamic plots a basis of automatic processing have been developed, similar to CDP procedure in method of
Supergravity for Effective Theories
Daniel Baumann; Daniel Green(Stanford Institute for Theoretical Physics, Stanford University, 382 Via Pueblo Mall, Stanford, CA 94305, U.S.A.)
2011-01-01
Higher-derivative operators are central elements of any effective field theory. In supersymmetric theories, these operators include terms with derivatives in the K\\"ahler potential. We develop a toolkit for coupling such supersymmetric effective field theories to supergravity. We explain how to write the action for minimal supergravity coupled to chiral superfields with arbitrary numbers of derivatives and curvature couplings. We discuss two examples in detail, showing how the component actio...
Coherent states for quadratic Hamiltonians
Contreras-Astorga, Alonso; Velazquez, Mercedes
2010-01-01
The coherent states for a set of quadratic Hamiltonians in the trap regime are constructed. A matrix technique which allows to identify directly the creation and annihilation operators will be presented. Then, the coherent states as simultaneous eigenstates of the annihilation operators will be derived, and they are going to be compared with those attained through the displacement operator method. The corresponding wave function will be found, and a general procedure for obtaining several expected values involving the canonical operators in these states will be described. The results will be illustrated through the asymmetric Penning trap.
Coherent states for quadratic Hamiltonians
Energy Technology Data Exchange (ETDEWEB)
Contreras-Astorga, Alonso; Fernandez C, David J; Velazquez, Mercedes, E-mail: david@fis.cinvestav.mx [Departamento de Fisica, Cinvestav, AP 14-740, 07000 Mexico DF (Mexico)
2011-01-21
The coherent states for a set of quadratic Hamiltonians in the trap regime are constructed. A matrix technique which allows us to directly identify the creation and annihilation operators will be presented. Then, the coherent states as simultaneous eigenstates of the annihilation operators will be derived, and will be compared with those attained through the displacement operator method. The corresponding wavefunction will be found, and a general procedure for obtaining several mean values involving the canonical operators in these states will be described. The results will be illustrated through the asymmetric Penning trap.
Interference due to coherence swapping
Indian Academy of Sciences (India)
Arun Kumar Pati; Marek Zukowski
2001-02-01
We propose a method called ‘coherence swapping’ which enables us to create superposition of a particle in two distinct paths, which is fed with initially incoherent, independent radiation. This phenomenon is also present for the charged particles, and can be used to swap the effect of ﬂux line due to the Aharonov–Bohm effect. We propose an optical version of experimental set-up to test the coherence swapping. The phenomenon, which is simpler than entanglement swapping or teleportation, raises some fundamental questions about the true nature of wave-particle duality, and also opens up the possibility of studying the quantum erasure from a new angle.
Harary, Frank
2015-01-01
Presented in 1962-63 by experts at University College, London, these lectures offer a variety of perspectives on graph theory. Although the opening chapters form a coherent body of graph theoretic concepts, this volume is not a text on the subject but rather an introduction to the extensive literature of graph theory. The seminar's topics are geared toward advanced undergraduate students of mathematics.Lectures by this volume's editor, Frank Harary, include ""Some Theorems and Concepts of Graph Theory,"" ""Topological Concepts in Graph Theory,"" ""Graphical Reconstruction,"" and other introduc
Meta-Structures: The Search of Coherence in Collective Behaviours (without Physics)
Eliano Pessa; Ignazio Licata; Gianfranco Minati
2013-01-01
This contribution shortly outlines and reviews a theoretical and computational approach for a theory of change concerning systems where it is not possible to apply the laws of motion ab initio. The concept of meta-structure relates to the emergence of forms of spatiotemporal coherences in collective behaviours intended as coherent sequences of multiple structures. The essential difference compared with traditional methods is the role of the cognitive design by the observer when identifying mu...
Fifth-Order Harmonic Generation using a Coherent Controlled Two-Pulsed Optical Field
Institute of Scientific and Technical Information of China (English)
刘婷婷; 王大威; 陆伟新; 孙泉; 杨宏; 蒋红兵; 龚旗煌
2002-01-01
We have experimentally studied the characteristics of fifth-order harmonic radiation produced by two coherent femtosecond laser pulses with a changeable relative phase. The intensities of harmonic generation are found to increase vith the coherent degree. In one optical period, the temporal variation of harmonics exhibits an asymmetric characteristic, vhich is interpreted in terms of ionization theory and the deformation of the wave packets of fundamental field contribution to harmonic generation.
Institute of Scientific and Technical Information of China (English)
林隆清
2007-01-01
In the process of college English intensive reading teaching,the analysis of textual cohesion and coherence is of great significance in that it can help students better understand the structure and contents of the teaching mterials,improve their ability in commnding and applying the language,thus improving the quality of college English teaching.This paper tries to analyze how to apply the theory of textual cohesion and coherence to the teaching of college English intensive reading.
Controlling quantum coherence of atom laser by light with strong strength
Institute of Scientific and Technical Information of China (English)
景辉; 葛墨林
2002-01-01
A new method for controlling the quantum coherence of atom laser by applying input light with strong strength is presented within the framework of quantum dynamical theory. Unlike the case of rotating wave approximation(RWA), we show that the non-classical properties, such as sub-Poisson distribution and quadrature squeezed effect, can appear in the output atom laser beam with time. By choosing suitable initial RF phase, a steady and brighter output of squeezed coherent atom laser is also available.
X-ray coherent diffraction interpreted through the fractional Fourier transform
Energy Technology Data Exchange (ETDEWEB)
Le Bolloc' h, D., E-mail: lebolloch@lps.u-psud.fr [Laboratoire de Physique des Solides (CNRS-UMR 8502), Bat. 510, Universite Paris-sud, 91405 Orsay Cedex (France); Pinsolle, E.; Sadoc, J.F. [Laboratoire de Physique des Solides (CNRS-UMR 8502), Bat. 510, Universite Paris-sud, 91405 Orsay Cedex (France)
2012-06-01
We propose to use the fractional Fourier transform to deal with diffraction of coherent X-ray beams from the Fresnel to the Fraunhofer regime. We will illustrate the benefits of the approach compared to the Fresnel wave propagation theory from situations commonly encountered in diffraction experiments: the successive diffraction of two objects and coherent diffraction of a periodic modulation as a charge density wave, containing or not a phase shift.
X-ray coherent diffraction interpreted through the fractional Fourier transform
International Nuclear Information System (INIS)
We propose to use the fractional Fourier transform to deal with diffraction of coherent X-ray beams from the Fresnel to the Fraunhofer regime. We will illustrate the benefits of the approach compared to the Fresnel wave propagation theory from situations commonly encountered in diffraction experiments: the successive diffraction of two objects and coherent diffraction of a periodic modulation as a charge density wave, containing or not a phase shift.
Optimal control of population and coherence in three-level Λ systems
International Nuclear Information System (INIS)
Optimal control theory (OCT) implementations for an efficient population transfer and creation of maximum coherence in a three-level system are considered. We demonstrate that the half-stimulated Raman adiabatic passage scheme for creation of the maximum Raman coherence is the optimal solution according to the OCT. We also present a comparative study of several implementations of OCT applied to the complete population transfer and creation of the maximum coherence. Performance of the conjugate gradient method, the Zhu-Rabitz method and the Krotov method has been analysed.
Baby universes in string theory
R.H. Dijkgraaf; R. Gopakumar; H. Ooguri; C. Vafa
2006-01-01
We argue that the holographic description of four-dimensional Bogomol'nyi-Prasad-Sommerfield black holes naturally includes multicenter solutions. This suggests that the holographic dual to the gauge theory is not a single AdS(2) x S-2 but a coherent ensemble of them. We verify this in a particular
Coherent optical control of polarization with a critical metasurface
Kang, Ming
2015-01-01
We describe the mechanism by which a metamaterial surface can act as an ideal phase-controlled rotatable linear polarizer. With equal-power linearly polarized beams incident on each side of the surface, varying the relative phase rotates the polarization angles of the output beams, while keeping the polarization exactly linear. The explanation is based on coupled-mode theory and the idea of coherent perfect absorption into auxiliary polarization channels. The polarization-rotating behavior occurs at a critical point of the coupled-mode theory, which can be associated with the exceptional point of a parity-time (PT) symmetric effective Hamiltonian.
Tolerance on tilt error for coherent combining of fiber lasers
Institute of Scientific and Technical Information of China (English)
Pu Zhou; Zilun Chen; Xiaolin Wang; Xiao Li; Zejin Liu; Xiaojun Xu
2009-01-01
Limited by the precision of optical machining and assembling, the optical axes of lasers in an array cannot be strictly parallel to each other, which will result in the beam quality degradation of the combined beam. The tolerance on tilt error for coherent combining of fiber lasers is studied in detail. The complex amplitude distribution in the far field for the Gaussian beam with tilt angle is obtained by a novel coordinate transform method. Effect of tilt error on coherent combining is modelled analytically. Beam propagation factor is used to evaluate the effect of coherent combining. Numerical results show that for ring-distributed fiber laser array with central wavelength 位 and geometry size D, if the root-mean-square (RMS) value of the tilt error is smaller than 0.72位/D, the energy encircled in the diffraction-limited bucket can be ensured to be more than 50% of the value when there is no tilt error. The results are helpful to the designing and manufacturing of fiber array for coherent combining.
Central Limit Theory Based Approach to Analyze the Performance of ATM Buffers%基于中心极限定理的ATM缓存性能分析方法
Institute of Scientific and Technical Information of China (English)
施建俊; 薛质; 朱康辛
2001-01-01
A new analytical technique to determine the tail of queue length distribution at an ATM multiplexer was developed. The ATM multiplexer was modeled as a fluid queue serving a large number of independent sources. The method is mainly based on the central limit theory, and can avoid the state explosion problem. The approach is quite general, as it has little to do with the types of sources.%提出了一种基于中心极限定理的，并能避免其他分析方法中遇到的状态空间剧增的分析ATM复用器缓存队长发布的方法．其网络流量采用大量独立信源复用后的液体流模型．该分析方法和具体的信源类型无关，具有相当大的适用范围．
Coherent states: a contemporary panorama Coherent states: a contemporary panorama
Twareque Ali, S.; Antoine, Jean-Pierre; Bagarello, Fabio; Gazeau, Jean-Pierre
2012-06-01
Coherent states (CS) of the harmonic oscillator (also called canonical CS) were introduced in 1926 by Schrödinger in answer to a remark by Lorentz on the classical interpretation of the wave function. They were rediscovered in the early 1960s, first (somewhat implicitly) by Klauder in the context of a novel representation of quantum states, then by Glauber and Sudarshan for the description of coherence in lasers. Since then, CS have grown into an extremely rich domain that pervades almost every corner of physics and have also led to the development of several flourishing topics in mathematics. Along the way, a number of review articles have appeared in the literature, devoted to CS, notably the 1985 reprint volume of Klauder and Skagerstam [1], the 1990 review paper by Zhang et al [2], the 1993 Oak Ridge Conference [3] and the 1995 review paper by Ali et al [4]. Textbooks also have been published, among which one might mention the ground breaking text of Perelomov [5] focusing on the group-theoretical aspects, that of Ali et al [6]1 analyzing systematically the mathematical structure beyond the group-theoretical approach and also the relation to wavelet analysis, that of Dodonov and Man'ko [7] mostly devoted to quantum optics, that of Gazeau [8] more oriented towards the physical, probabilistic and quantization aspects, and finally the very recent one by Combescure and Robert [9]. In retrospect, one can see that the development of CS has gone through a two-phase transition. First, the (simultaneous) discovery in 1972 by Gilmore and Perelomov that CS were rooted in group theory, then the realization that CS can be defined in a purely algebraic way, as an eigenvalue problem or by a series expansion (Malkin and Man'ko 1969, Barut and Girardello 1971, Gazeau and Klauder 1999; references to the original articles may be found in the textbooks quoted above). Both facts resulted in an explosive expansion of the CS literature. We thought, therefore, that the time was ripe
Coherent state quantization of quaternions
International Nuclear Information System (INIS)
Parallel to the quantization of the complex plane, using the canonical coherent states of a right quaternionic Hilbert space, quaternion field of quaternionic quantum mechanics is quantized. Associated upper symbols, lower symbols, and related quantities are analyzed. Quaternionic version of the harmonic oscillator and Weyl-Heisenberg algebra are also obtained
Coherent control of quantum dots
DEFF Research Database (Denmark)
Johansen, Jeppe; Lodahl, Peter; Hvam, Jørn Märcher
In recent years much effort has been devoted to the use of semiconductor quantum dotsystems as building blocks for solid-state-based quantum logic devices. One importantparameter for such devices is the coherence time, which determines the number ofpossible quantum operations. From earlier...
Optical coherent control in semiconductors
DEFF Research Database (Denmark)
Østergaard, John Erland; Vadim, Lyssenko; Hvam, Jørn Märcher
2001-01-01
of quantum control including the recent applications to semiconductors and nanostructures. We study the influence of inhomogeneous broadening in semiconductors on CC results. Photoluminescence (PL) and the coherent emission in four-wave mixing (FWM) is recorded after resonant excitation with phase...
Coherence matrix of plasmonic beams
DEFF Research Database (Denmark)
Novitsky, Andrey; Lavrinenko, Andrei
2013-01-01
We consider monochromatic electromagnetic beams of surface plasmon-polaritons created at interfaces between dielectric media and metals. We theoretically study non-coherent superpositions of elementary surface waves and discuss their spectral degree of polarization, Stokes parameters, and the form...
Optical Coherence Tomography: Advanced Modeling
DEFF Research Database (Denmark)
Andersen, Peter E.; Thrane, Lars; Yura, Harold T.;
2013-01-01
Analytical and numerical models for describing and understanding the light propagation in samples imaged by optical coherence tomography (OCT) systems are presented. An analytical model for calculating the OCT signal based on the extended Huygens-Fresnel principle valid both for the single- and...
Coherent state quantization of quaternions
Energy Technology Data Exchange (ETDEWEB)
Muraleetharan, B., E-mail: bbmuraleetharan@jfn.ac.lk, E-mail: santhar@gmail.com [Department of Mathematics and Statistics, University of Jaffna, Thirunelveli (Sri Lanka); Thirulogasanthar, K., E-mail: bbmuraleetharan@jfn.ac.lk, E-mail: santhar@gmail.com [Department of Computer Science and Software Engineering, Concordia University, 1455 De Maisonneuve Blvd. West, Montreal, Quebec H3G 1M8 (Canada)
2015-08-15
Parallel to the quantization of the complex plane, using the canonical coherent states of a right quaternionic Hilbert space, quaternion field of quaternionic quantum mechanics is quantized. Associated upper symbols, lower symbols, and related quantities are analyzed. Quaternionic version of the harmonic oscillator and Weyl-Heisenberg algebra are also obtained.
Coherent state quantization of quaternions
Muraleetharan, B.; Thirulogasanthar, K.
2015-08-01
Parallel to the quantization of the complex plane, using the canonical coherent states of a right quaternionic Hilbert space, quaternion field of quaternionic quantum mechanics is quantized. Associated upper symbols, lower symbols, and related quantities are analyzed. Quaternionic version of the harmonic oscillator and Weyl-Heisenberg algebra are also obtained.
Optimal switching using coherent control
DEFF Research Database (Denmark)
Kristensen, Philip Trøst; Heuck, Mikkel; Mørk, Jesper
2013-01-01
We introduce a general framework for the analysis of coherent control in coupled optical cavity-waveguide systems. Within this framework, we use an analytically solvable model, which is validated by independent numerical calculations, to investigate switching in a micro cavity and demonstrate that...
Measurement of spin coherence using Raman scattering
Sun, Z.; Delteil, A.; Faelt, S.; Imamoǧlu, A.
2016-06-01
Ramsey interferometry provides a natural way to determine the coherence time of most qubit systems. Recent experiments on quantum dots, however, demonstrated that dynamical nuclear spin polarization can strongly influence the measurement process, making it difficult to extract the T2* coherence time using standard optical Ramsey pulses. Here, we demonstrate an alternative method for spin coherence measurement that is based on first-order coherence of photons generated in spin-flip Raman scattering. We show that if a quantum emitter is driven by a weak monochromatic laser, Raman coherence is determined exclusively by spin coherence, allowing for a direct determination of spin T2* time. When combined with coherence measurements on Rayleigh scattered photons, our technique enables us to identify coherent and incoherent contributions to resonance fluorescence, and to minimize the latter. We verify the validity of our technique by comparing our results to those determined from Ramsey interferometry for electron and heavy-hole spins.
Neutrino production coherence and oscillation experiments
Akhmedov, Evgeny; Smirnov, Alexei
2012-01-01
Neutrino oscillations are only observable when the neutrino production, propagation and detection coherence conditions are satisfied. In this paper we consider in detail neutrino production coherence, taking \\pi\\to \\mu \
Directory of Open Access Journals (Sweden)
Valter Alnis Bezerra
2003-06-01
theories in the early 70s. The success of renormalization was such that, from its beginnings as a mere ad hoc theoretical device, it gradually earned the condition of a criterion for the construction and appraisal of theories in field physics. One of the aims of this article is to show that this change in the methodological status of renormalization can be understood in the context of Larry Laudan's reticulational model of rationality. In spite of the extraordinary theoretical and empirical progress achieved, however, there were always polemics regarding the place that renormalization should occupy within the conceptual structure of the discipline. These polemics revolve around the fact that renormalization apparently goes against a cognitive value that is regarded as fundamental, namely, consistency. The second aim of this paper is to show how the reticulational model helps to throw light upon this question as well. We attempt to show in which sense it was rational to accept renormalization in particle and field physics despite the problem of inconsistency. To this end we make use of the theses of the reticulational model, supplemented with theses from Putnam and Quine, and from the coherence theory of justification.
The Systems Theory Framework of Career Development
McMahon, Mary
2011-01-01
The Systems Theory Framework (STF; McMahon & Patton, 1995; Patton & McMahon, 2006) of career development was proposed as a metatheoretical framework that accommodates the contribution of all theories and offers an integrative and coherent framework of career influences. In this article, the author provides an overview of the STF, outlines its…
Coherent Communication with Continuous Quantum Variables
Wilde, Mark M.; Krovi, Hari; Brun, Todd A.
2006-01-01
The coherent bit (cobit) channel is a resource intermediate between classical and quantum communication. It produces coherent versions of teleportation and superdense coding. We extend the cobit channel to continuous variables by providing a definition of the coherent nat (conat) channel. We construct several coherent protocols that use both a position-quadrature and a momentum-quadrature conat channel with finite squeezing. Finally, we show that the quality of squeezing diminishes through su...
Electron beam instrumentation techniques using coherent radiation
International Nuclear Information System (INIS)
Much progress has been made on coherent radiation research since coherent synchrotron radiation was first observed in 1989. The use of coherent radiation as a bunch length diagnostic tool has been studied by several groups. In this paper, brief introductions to coherent radiation and far-infrared measurement are given, the progress and status of their beam diagnostic application are reviewed, different techniques are described, and their advantages and limitations are discussed
Can Natural Sunlight Induce Coherent Exciton Dynamics?
Olšina, Jan; Dijkstra, Arend G.; Wang, Chen; Cao, Jianshu
2014-01-01
Excitation of a model photosynthetic molecular aggregate by incoherent sunlight is systematically examined. For a closed system, the excited state coherence induced by the sunlight oscillates with an average amplitude that is inversely proportional to the excitonic gap, and reaches a stationary amplitude that depends on the temperature and coherence time of the radiation field. For an open system, the light-induced dynamical coherence relaxes to a static coherence determined by the non-canoni...
Energy minimization mechanisms of semi-coherent interfaces
Energy Technology Data Exchange (ETDEWEB)
Shao, Shuai; Wang, J., E-mail: wangj6@lanl.gov [MST-8, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Misra, Amit [MPA-CINT, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2014-07-14
In this article, we discussed energy minimization mechanisms of semi-coherent interfaces based on atomistic simulations and dislocation theory. For example, of (111) interfaces between two face centered cubic (FCC) crystals, interface comprises of two stable structures (normal FCC stacking structure and intrinsic stacking fault structure), misfit dislocations, and misfit dislocation intersections or nodes (corresponding to the high energy stacking fault (HESF) structure). According to atomistic simulations of four interfaces, we found that (1) greater spacing between misfit dislocations and/or larger slopes of generalized stacking fault energy at the stable interface structures leads to a narrower dislocation core and a higher state of coherency in the stable interfaces; (2) the HESF region is relaxed by the relative rotation and dilation/compression of the two crystals at the node. The crystal rotation is responsible for the spiral feature at the vicinity of a node and the dilation/compression is responsible for the creation of the free volume at a node; (3) the spiral feature is gradually frail and the free volume decreases with decreasing misfit dislocation spacing, which corresponds to an increase in lattice mismatch and/or a decrease in lattice rotation. Finally, the analysis method and energy minimization mechanisms explored in FCC (111) semi-coherent interfaces are also applicable for other semi-coherent interfaces.
Quantum probabilistic teleportation via entangled coherent states
Energy Technology Data Exchange (ETDEWEB)
Li Shangbin; Xu Jingbo
2003-03-31
We study the entanglement of entangled coherent states in vacuum environment by employing the entanglement of formation and propose a scheme to probabilistically teleport a coherent superposition state via entangled coherent states. The mean fidelity of the scheme is then investigated and the optimal amplitude of the teleported state found.
Report on single beam stability - coherent effects
International Nuclear Information System (INIS)
Group 1A was concerned with single beam stability, coherent effects. Theory is available. Most of the material for this work was drawn from F.J. Sacherer theory which has been left in reasonably good shape in the sense that given any coupling impedance, its effect on the beam can be estimated. The EBI computer program was extensively used in this respect. We still lack thorough knowledge of the SPS coupling impedance. Accordingly our results rest on a model. This model should be too unrealistic since it originates from various data of the SPS and other machines. Nevertheless any complementary information about the SPS impedance would be welcome. Broad-band impedance and parasitic effects on transverse and longitudinal motions will be reviewed. We shall mainly focus on the 270 GeV case with six equidistant bunches and 1011 particles per bunch. For other schemes results can be obtained in a similar fashion. Some relevant figures will be given for the situation at injection. (orig.)
Measuring finite quantum geometries via quasi-coherent states
Schneiderbauer, Lukas; Steinacker, Harold C.
2016-07-01
We develop a systematic approach to determine and measure numerically the geometry of generic quantum or ‘fuzzy’ geometries realized by a set of finite-dimensional Hermitian matrices. The method is designed to recover the semi-classical limit of quantized symplectic spaces embedded in {{{R}}}d including the well-known examples of fuzzy spaces, but it applies much more generally. The central tool is provided by quasi-coherent states, which are defined as ground states of Laplace- or Dirac operators corresponding to localized point branes in target space. The displacement energy of these quasi-coherent states is used to extract the local dimension and tangent space of the semi-classical geometry, and provides a measure for the quality and self-consistency of the semi-classical approximation. The method is discussed and tested with various examples, and implemented in an open-source Mathematica package.
Influence of coherent adiabatic excitation on femtosecond transient signals
Conde, A Peralta; Longarte, A
2016-01-01
The transient signals derived from femtosecond pump-probe experiments are analyzed in terms of the coherent evolution of the energy levels perturbed by the excitation pulse. The model system is treated as the sum of independent two-level subsystems that evolve adiabatically or are permanently excited, depending on the detuning from the central wavelength of the excitation laser. This approach will allow us to explain numerically and analytically the convergence between the coherent and incoherent (rate equations) treatments for complex multi-level systems. It will be also shown that the parameter that determines the validity of the incoherent treatment is the distribution of states outside and inside the laser bandwidth, rather than the density of states as it is commonly accepted.
Measuring finite Quantum Geometries via Quasi-Coherent States
Schneiderbauer, Lukas
2016-01-01
We develop a systematic approach to determine and measure numerically the geometry of generic quantum or "fuzzy" geometries realized by a set of finite-dimensional hermitian matrices. The method is designed to recover the semi-classical limit of quantized symplectic spaces embedded in $\\mathbb{R}^d$ including the well-known examples of fuzzy spaces, but it applies much more generally. The central tool is provided by quasi-coherent states, which are defined as ground states of Laplace- or Dirac operators corresponding to localized point branes in target space. The displacement energy of these quasi-coherent states is used to extract the local dimension and tangent space of the semi-classical geometry, and provides a measure for the quality and self-consistency of the semi-classical approximation. The method is discussed and tested with various examples, and implemented in an open-source Mathematica package.
Institute of Scientific and Technical Information of China (English)
杨世琳; 杜改萍; 郝玉华
2013-01-01
目的 对Vogt-小柳-原田病患者黄斑中心凹处频域OCT图像特点进行分析,探讨影响患者视力预后因素.方法 经荧光素眼底血管造影确诊的13例(26眼)Vogt-小柳-原田病患者,皮质激素治疗前和治疗后1周、1个月、3个月、6个月进行频域OCT检查,对黄斑中心凹处OCT图像特点进行分析,并对治疗前后视力、眼底进行观察.结果 糖皮质激素治疗后1周42.3％的患眼视力≥0.4,治疗后3个月、6个月≥0.4者分别为73.1％、80.8％.治疗后1个月,大部分荧光素眼底血管造影正常,仅3眼有轻度视盘渗漏.治疗后3个月、6个月,荧光素眼底血管造影23眼未见异常,3眼出现色素紊乱.在皮质激素治疗前,26眼中有25眼(96.1％)黄斑中心凹处存在浆液性视网膜脱离,高度为(341±123) μm.有10眼(38.5％)视网膜层间有囊样间隙的存在,在囊样间隙的底部可见一连续单一的膜样结构平铺于视网膜色素上皮之上,此膜样结构和周围的IS/OS相连续.治疗l周后,25眼中有24眼(96.0％)浆液性视网膜脱离仍然存在,但是视网膜下液明显吸收,其高度为(118±56) μm,比治疗前平均下降65.4％,治疗前后差异有显著统计学意义(P＜0.01).8眼视网膜层间囊样间隙完全消失.治疗后1个月,26眼浆液性视网膜脱离和视网膜层间囊样间隙全部消失.治疗后3个月及6个月,黄斑中心凹OCT图像基本正常.结论 浆液性视网膜脱离是Vogt-小柳-原田病频域OCT图像的共有特点,部分患者视网膜出现层间囊样间隙,此囊样间隙好发于视网膜内外层之间.通过皮质激素治疗,浆液性视网膜脱离和视网膜层间囊样间隙均可吸收消失,但视网膜层间囊样间隙的消失要快于浆液性视网膜脱离.%Objective To explore factors that could affect prognosis of visual acuity by analyzing spectral-domain optical coherence tomography(OCT) image features of central fovea of macula in patients with
Reduced central blood volume in cirrhosis
DEFF Research Database (Denmark)
Bendtsen, F; Henriksen, Jens Henrik Sahl; Sørensen, T I; Stadeager, C; Ring-Larsen, H
1989-01-01
The pathogenesis of ascites formation in cirrhosis is uncertain. It is still under debate whether the effective blood volume is reduced (underfilling theory) or whether the intravascular compartment is expanded (overflow theory). This problem has not yet been solved because of insufficient tools...... for measuring the central blood volume. We have developed a method that enables us to determine directly the central blood volume, i.e., the blood volume in the heart cavities, lungs, and central arterial tree. In 60 patients with cirrhosis and 16 control subjects the central blood volume was assessed...... according to the kinetic theory as the product of cardiac output and mean transit time of the central vascular bed. Central blood volume was significantly smaller in patients with cirrhosis than in controls (mean 21 vs. 27 ml/kg estimated ideal body weight, p less than 0.001; 25% vs. 33% of the total blood...
Computational invariant theory
Derksen, Harm
2015-01-01
This book is about the computational aspects of invariant theory. Of central interest is the question how the invariant ring of a given group action can be calculated. Algorithms for this purpose form the main pillars around which the book is built. There are two introductory chapters, one on Gröbner basis methods and one on the basic concepts of invariant theory, which prepare the ground for the algorithms. Then algorithms for computing invariants of finite and reductive groups are discussed. Particular emphasis lies on interrelations between structural properties of invariant rings and computational methods. Finally, the book contains a chapter on applications of invariant theory, covering fields as disparate as graph theory, coding theory, dynamical systems, and computer vision. The book is intended for postgraduate students as well as researchers in geometry, computer algebra, and, of course, invariant theory. The text is enriched with numerous explicit examples which illustrate the theory and should be ...
Coherent transport through interacting quantum dots
Energy Technology Data Exchange (ETDEWEB)
Hiltscher, Bastian
2012-10-05
The present thesis is composed of four different works. All deal with coherent transport through interacting quantum dots, which are tunnel-coupled to external leads. There a two main motivations for the use of quantum dots. First, they are an ideal device to study the influence of strong Coulomb repulsion, and second, their discrete energy levels can easily be tuned by external gate electrodes to create different transport regimes. The expression of coherence includes a very wide range of physical correlations and, therefore, the four works are basically independent of each other. Before motivating and introducing the different works in more detail, we remark that in all works a diagrammatic real-time perturbation theory is used. The fermionic degrees of freedom of the leads are traced out and the elements of the resulting reduced density matrix can be treated explicitly by means of a generalized master equation. How this equation is solved, depends on the details of the problem under consideration. In the first of the four works adiabatic pumping through an Aharonov-Bohm interferometer with a quantum dot embedded in each of the two arms is studied. In adiabatic pumping transport is generated by varying two system parameters periodically in time. We consider the two dot levels to be these two pumping parameters. Since they are located in different arms of the interferometer, pumping is a quantum mechanical effect purely relying on coherent superpositions of the dot states. It is very challenging to identify a quantum pumping mechanism in experiments, because a capacitive coupling of the gate electrodes to the leads may yield an undesired AC bias voltage, which is rectified by a time dependent conductance. Therefore, distinguishing features of these two transport mechanisms are required. We find that the dependence on the magnetic field is the key feature. While the pumped charge is an odd function of the magnetic flux, the rectified current is even, at least in
Coherent transport through interacting quantum dots
International Nuclear Information System (INIS)
The present thesis is composed of four different works. All deal with coherent transport through interacting quantum dots, which are tunnel-coupled to external leads. There a two main motivations for the use of quantum dots. First, they are an ideal device to study the influence of strong Coulomb repulsion, and second, their discrete energy levels can easily be tuned by external gate electrodes to create different transport regimes. The expression of coherence includes a very wide range of physical correlations and, therefore, the four works are basically independent of each other. Before motivating and introducing the different works in more detail, we remark that in all works a diagrammatic real-time perturbation theory is used. The fermionic degrees of freedom of the leads are traced out and the elements of the resulting reduced density matrix can be treated explicitly by means of a generalized master equation. How this equation is solved, depends on the details of the problem under consideration. In the first of the four works adiabatic pumping through an Aharonov-Bohm interferometer with a quantum dot embedded in each of the two arms is studied. In adiabatic pumping transport is generated by varying two system parameters periodically in time. We consider the two dot levels to be these two pumping parameters. Since they are located in different arms of the interferometer, pumping is a quantum mechanical effect purely relying on coherent superpositions of the dot states. It is very challenging to identify a quantum pumping mechanism in experiments, because a capacitive coupling of the gate electrodes to the leads may yield an undesired AC bias voltage, which is rectified by a time dependent conductance. Therefore, distinguishing features of these two transport mechanisms are required. We find that the dependence on the magnetic field is the key feature. While the pumped charge is an odd function of the magnetic flux, the rectified current is even, at least in
Theory of coherent dynamic nuclear polarization in quantum dots
DEFF Research Database (Denmark)
Neder, Izhar; Rudner, Mark Spencer; Halperin, Bertrand
2014-01-01
We consider the production of dynamic nuclear spin polarization (DNP) in a two-electron double quantum dot, in which the electronic levels are repeatedly swept through a singlet-triplet avoided crossing. Our analysis helps to elucidate the intriguing interplay between electron-nuclear hyperfine...
Wideband Radar Target Detection Theory in Coherent K Distributed Clutter
Directory of Open Access Journals (Sweden)
Xiandong Meng
2013-02-01
Full Text Available The aim of this study is to analyze the influence of neglecting K distributed clutter texture on wideband radar distributed targets detection. At first, the texture and the speckle of K clutter are researched and the Probability Density Function (PDF of K clutter and its texture are derived, then the optimal detector by Neyman-Pearson (NP is proposed, by contrast, another detector-Suboptimum Generalized Likelihood Ratio Test (GLRT neglecting the clutter texture is given. Next, the estimation of covariance matrix is introduced. Finally, the numerical results are presented by means of Monte Carlo simulation strategy and the simulation results highlight that the performance loss of the 2 detectors in different shaping parameter, the result shows that the performance loss of the detector in K distributed clutter less than 1 db due to the texture is neglected and adaptively estimating the covariance matrix and the K clutter texture can be neglected on wideband radar targets detection.
Characterisation of dispersive systems using a coherer
Directory of Open Access Journals (Sweden)
Nikolić Pantelija M.
2002-01-01
Full Text Available The possibility of characterization of aluminium powders using a horizontal coherer has been considered. Al powders of known dimension were treated with a high frequency electromagnetic field or with a DC electric field, which were increased until a dielectric breakdown occurred. Using a multifunctional card PC-428 Electronic Design and a suitable interface between the coherer and PC, the activation time of the coherer was measured as a function of powder dimension and the distance between the coherer electrodes. It was also shown that the average dimension of powders of unknown size could be determined using the coherer.
Effect of Ambient and Oxygen Temperature on Flow Field Characteristics of Coherent Jet
Liu, Fuhai; Zhu, Rong; Dong, Kai; Hu, Shaoyan
2016-02-01
The coherent jets are now used widely in electric arc furnace steelmaking process to increase the stirring ability, reaction rates, and energy efficiency. However, there has been limited research on the basic physics of the coherent jets. In the present study, the characteristics of flow field of supersonic coherent jet in hot and cold condition were studied. The total temperature and axial velocity were measured by combustion experiment. Flow field characteristics of supersonic coherent jet were simulated by Fluent software. The detailed chemical kinetic mechanism is presently used for the modeling of reactions. It consists of 53 species, plus Ar and N2, for a total of 325 reversible reactions. The present study showed that the shrouding flame decreases the entrainment of the ambient gas to the central supersonic jet, which results in a low expansion rate for the coherent supersonic jet. The higher ambient temperature can prolong the potential core of coherent jet and conventional jet. However, the potential core of coherent jet reduces with oxygen temperature increasing, which is opposite to conventional jet.
Generalized Grassmannian coherent states for pseudo-Hermitian n-level systems
International Nuclear Information System (INIS)
The purpose of this paper is to generalize fermionic coherent states for two-level systems described by pseudo-Hermitian Hamiltonian (Cherbal et al 2007 J. Phys. A: Math. Theor. 40 1835) to n-level systems. Central to this task is the expression of the coherent states in terms of generalized Grassmann variables. These kinds of Grassmann coherent states satisfy the bi-overcompleteness condition instead of the overcompleteness one, as it is reasonably expected because of the biorthonormality of the system. Choosing an appropriate Grassmann weight function, the resolution of identity is examined. Moreover Grassmannian coherent and squeezed states of the deformed group SUq(2) for the three-level pseudo-Hermitian system are presented.
Generalized Grassmannian coherent states for pseudo-Hermitian n-level systems
Najarbashi, G.; Fasihi, M. A.; Fakhri, H.
2010-08-01
The purpose of this paper is to generalize fermionic coherent states for two-level systems described by pseudo-Hermitian Hamiltonian (Cherbal et al 2007 J. Phys. A: Math. Theor. 40 1835) to n-level systems. Central to this task is the expression of the coherent states in terms of generalized Grassmann variables. These kinds of Grassmann coherent states satisfy the bi-overcompleteness condition instead of the overcompleteness one, as it is reasonably expected because of the biorthonormality of the system. Choosing an appropriate Grassmann weight function, the resolution of identity is examined. Moreover Grassmannian coherent and squeezed states of the deformed group SUq(2) for the three-level pseudo-Hermitian system are presented.
Generalized Grassmannian coherent states for pseudo-Hermitian n-level systems
Energy Technology Data Exchange (ETDEWEB)
Najarbashi, G [Department of Physics, University of Mohaghegh Ardabili, Ardabil 179 (Iran, Islamic Republic of); Fasihi, M A [Research Center for Quantum Computing, Interdisciplinary Graduate School of Science and Engineering, Kinki University, Higashi-Osaka, Osaka 577-8502 (Japan); Fakhri, H, E-mail: najarbashi@uma.ac.i, E-mail: fasihi@alice.math.kindai.ac.j, E-mail: hfakhri@tabrizu.ac.i [Department of Theoretical Physics and Astrophysics, Tabriz University, Tabriz 51664 (Iran, Islamic Republic of)
2010-08-13
The purpose of this paper is to generalize fermionic coherent states for two-level systems described by pseudo-Hermitian Hamiltonian (Cherbal et al 2007 J. Phys. A: Math. Theor. 40 1835) to n-level systems. Central to this task is the expression of the coherent states in terms of generalized Grassmann variables. These kinds of Grassmann coherent states satisfy the bi-overcompleteness condition instead of the overcompleteness one, as it is reasonably expected because of the biorthonormality of the system. Choosing an appropriate Grassmann weight function, the resolution of identity is examined. Moreover Grassmannian coherent and squeezed states of the deformed group SU{sub q}(2) for the three-level pseudo-Hermitian system are presented.
The global coherence initiative: creating a coherent planetary standing wave.
McCraty, Rollin; Deyhle, Annette; Childre, Doc
2012-03-01
The much anticipated year of 2012 is now here. Amidst the predictions and cosmic alignments that many are aware of, one thing is for sure: it will be an interesting and exciting year as the speed of change continues to increase, bringing both chaos and great opportunity. One benchmark of these times is a shift in many people from a paradigm of competition to one of greater cooperation. All across the planet, increasing numbers of people are practicing heart-based living, and more groups are forming activities that support positive change and creative solutions for manifesting a better world. The Global Coherence Initiative (GCI) is a science-based, co-creative project to unite people in heart-focused care and intention. GCI is working in concert with other initiatives to realize the increased power of collective intention and consciousness. The convergence of several independent lines of evidence provides strong support for the existence of a global information field that connects all living systems and consciousness. Every cell in our bodies is bathed in an external and internal environment of fluctuating invisible magnetic forces that can affect virtually every cell and circuit in biological systems. Therefore, it should not be surprising that numerous physiological rhythms in humans and global collective behaviors are not only synchronized with solar and geomagnetic activity, but disruptions in these fields can create adverse effects on human health and behavior. The most likely mechanism for explaining how solar and geomagnetic influences affect human health and behavior are a coupling between the human nervous system and resonating geomagnetic frequencies, called Schumann resonances, which occur in the earth-ionosphere resonant cavity and Alfvén waves. It is well established that these resonant frequencies directly overlap with those of the human brain and cardiovascular system. If all living systems are indeed interconnected and communicate with each other
Wavefront sensing reveals optical coherence
Stoklasa, B; Rehacek, J; Hradil, Z; Sanchez-Soto, L L
2014-01-01
Wavefront sensing is a set of techniques providing efficient means to ascertain the shape of an optical wavefront or its deviation from an ideal reference. Due to its wide dynamical range and high optical efficiency, the Shack-Hartmann is nowadays the most widely used of these sensors. Here, we show that it actually performs a simultaneous measurement of position and angular spectrum of the incident radiation and, therefore, when combined with tomographic techniques previously developed for quantum information processing, the Shack-Hartmann can be instrumental in reconstructing the complete coherence properties of the signal. We confirm these predictions with an experimental characterization of partially coherent vortex beams, a case that cannot be treated with the standard tools. This seems to indicate that classical methods employed hitherto do not fully exploit the potential of the registered data.
Coherent-state-induced transparency
Gogyan, A.; Malakyan, Yu.
2016-04-01
We examine electromagnetically induced transparency (EIT) in an ensemble of cold Λ -type atoms induced by a quantum control field in multimode coherent states and compare it with the transparency created by the classical light of the same intensity. We show that the perfect coincidence is achieved only in the case of a single-mode coherent state, whereas the transparency sharply decreases, when the number of the modes exceeds the mean number of control photons in the medium. The origin of the effect is the modification of photon statistics in the control field with increasing the number of the modes that weakens its interaction with atoms resulting in a strong probe absorption. For the same reason, the probe pulse transforms from EIT-based slow light into superluminal propagation caused by the absorption.
How coherent are Josephson junctions?
Paik, Hanhee; Bishop, Lev S; Kirchmair, G; Catelani, G; Sears, A P; Johnson, B R; Reagor, M J; Frunzio, L; Glazman, L; Schoelkopf, R J
2011-01-01
Attaining sufficient coherence is a requirement for realizing a large-scale quantum computer. We present a new implementation of a superconducting transmon qubit that is strongly coupled to a three-dimensional superconducting cavity. We observe a reproducible increase in the coherence times of qubit (both $T_1$ and $T_2$ > 10 microseconds) and cavity ($T_{cav}$ ~ 50 microseconds) by more than an order of magnitude compared to the current state-of-art superconducting qubits. This enables the study of the stability and quality of Josephson junctions at precisions exceeding one part per million. Surprisingly, we see no evidence for $1/f$ critical current noise. At elevated temperatures, we observe the dissipation due to a small density (< 1 - 10 ppm) of thermally-excited quasiparticles. The results suggest that the overall quality of Josephson junctions will allow error rates of a few $10^{-4}$, approaching the error correction threshold.
Photoelectric converters with quantum coherence
Su, Shan-He; Sun, Chang-Pu; Li, Sheng-Wen; Chen, Jin-Can
2016-05-01
Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency ηCA. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to ηCA through manipulation of carefully controlled quantum coherences.