Covariant Hamiltonian field theory
Giachetta, G; Sardanashvily, G
1999-01-01
We study the relationship between the equations of first order Lagrangian field theory on fiber bundles and the covariant Hamilton equations on the finite-dimensional polysymplectic phase space of covariant Hamiltonian field theory. The main peculiarity of these Hamilton equations lies in the fact that, for degenerate systems, they contain additional gauge fixing conditions. We develop the BRST extension of the covariant Hamiltonian formalism, characterized by a Lie superalgebra of BRST and anti-BRST symmetries.
Tian, Wei; Cai, Li; Thissen, David; Xin, Tao
2013-01-01
In item response theory (IRT) modeling, the item parameter error covariance matrix plays a critical role in statistical inference procedures. When item parameters are estimated using the EM algorithm, the parameter error covariance matrix is not an automatic by-product of item calibration. Cai proposed the use of Supplemented EM algorithm for…
Generally Covariant Maxwell Theory for Media with a Local Response: Progress since 2000
Hehl, Friedrich W; Obukhov, Yuri N
2016-01-01
In the recent decades, it became more and more popular for engineers, physicists, and mathematicians alike to put the Maxwell equations into a generally covariant form. This is particularly useful for understanding the fundamental structure of electrodynamics (conservation of electric charge and magnetic flux). Moreover, it is ideally suited for applying it to media with local (and mainly linear) response behavior. We try to collect the new knowledge that grew out of this development. We would like to ask the participants of EMTS 2016 to inform us of work that we may have overlooked in our review.
Covariant Formulations of Superstring Theories.
Mikovic, Aleksandar Radomir
1990-01-01
Chapter 1 contains a brief introduction to the subject of string theory, and tries to motivate the study of superstrings and covariant formulations. Chapter 2 describes the Green-Schwarz formulation of the superstrings. The Hamiltonian and BRST structure of the theory is analysed in the case of the superparticle. Implications for the superstring case are discussed. Chapter 3 describes the Siegel's formulation of the superstring, which contains only the first class constraints. It is shown that the physical spectrum coincides with that of the Green-Schwarz formulation. In chapter 4 we analyse the BRST structure of the Siegel's formulation. We show that the BRST charge has the wrong cohomology, and propose a modification, called first ilk, which gives the right cohomology. We also propose another superparticle model, called second ilk, which has infinitely many coordinates and constraints. We construct the complete BRST charge for it, and show that it gives the correct cohomology. In chapter 5 we analyse the properties of the covariant vertex operators and the corresponding S-matrix elements by using the Siegel's formulation. We conclude that the knowledge of the ghosts is necessary, even at the tree level, in order to obtain the correct S-matrix. In chapter 6 we attempt to calculate the superstring loops, in a covariant gauge. We calculate the vacuum-to -vacuum amplitude, which is also the cosmological constant. We show that it vanishes to all loop orders, under the assumption that the free covariant gauge-fixed action exists. In chapter 7 we present our conclusions, and briefly discuss the random lattice approach to the string theory, as a possible way of resolving the problem of the covariant quantization and the nonperturbative definition of the superstrings.
Tay, Louis; Huang, Qiming; Vermunt, Jeroen K.
2016-01-01
In large-scale testing, the use of multigroup approaches is limited for assessing differential item functioning (DIF) across multiple variables as DIF is examined for each variable separately. In contrast, the item response theory with covariate (IRT-C) procedure can be used to examine DIF across multiple variables (covariates) simultaneously. To…
Covariant Hamilton equations for field theory
Energy Technology Data Exchange (ETDEWEB)
Giachetta, Giovanni [Department of Mathematics and Physics, University of Camerino, Camerino (Italy); Mangiarotti, Luigi [Department of Mathematics and Physics, University of Camerino, Camerino (Italy)]. E-mail: mangiaro@camserv.unicam.it; Sardanashvily, Gennadi [Department of Theoretical Physics, Physics Faculty, Moscow State University, Moscow (Russian Federation)]. E-mail: sard@grav.phys.msu.su
1999-09-24
We study the relations between the equations of first-order Lagrangian field theory on fibre bundles and the covariant Hamilton equations on the finite-dimensional polysymplectic phase space of covariant Hamiltonian field theory. If a Lagrangian is hyperregular, these equations are equivalent. A degenerate Lagrangian requires a set of associated Hamiltonian forms in order to exhaust all solutions of the Euler-Lagrange equations. The case of quadratic degenerate Lagrangians is studied in detail. (author)
Covariant Calculus for Effective String Theories
Dass, N. D. Hari; Matlock, Peter
2007-01-01
A covariant calculus for the construction of effective string theories is developed. Effective string theory, describing quantum string-like excitations in arbitrary dimension, has in the past been constructed using the principles of conformal field theory, but not in a systematic way. Using the freedom of choice of field definition, a particular field definition is made in a systematic way to allow an explicit construction of effective string theories with manifest exact conformal symmetry. ...
Manifest Covariant Hamiltonian Theory of General Relativity
Cremaschini, Claudio
2016-01-01
The problem of formulating a manifest covariant Hamiltonian theory of General Relativity in the presence of source fields is addressed, by extending the so-called "DeDonder-Weyl" formalism to the treatment of classical fields in curved space-time. The theory is based on a synchronous variational principle for the Einstein equation, formulated in terms of superabundant variables. The technique permits one to determine the continuum covariant Hamiltonian structure associated with the Einstein equation. The corresponding continuum Poisson bracket representation is also determined. The theory relies on first-principles, in the sense that the conclusions are reached in the framework of a non-perturbative covariant approach, which allows one to preserve both the 4-scalar nature of Lagrangian and Hamiltonian densities as well as the gauge invariance property of the theory.
Supergeometry in locally covariant quantum field theory
Hack, Thomas-Paul; Schenkel, Alexander
2015-01-01
In this paper we analyze supergeometric locally covariant quantum field theories. We develop suitable categories SLoc of super-Cartan supermanifolds, which generalize Lorentz manifolds in ordinary quantum field theory, and show that, starting from a few representation theoretic and geometric data, one can construct a functor A : SLoc --> S*Alg to the category of super-*-algebras which can be interpreted as a non-interacting super-quantum field theory. This construction turns out to disregard supersymmetry transformations as the morphism sets in the above categories are too small. We then solve this problem by using techniques from enriched category theory, which allows us to replace the morphism sets by suitable morphism supersets that contain supersymmetry transformations as their higher superpoints. We construct super-quantum field theories in terms of enriched functors eA : eSLoc --> eS*Alg between the enriched categories and show that supersymmetry transformations are appropriately described within the en...
Energy Technology Data Exchange (ETDEWEB)
Alfred Stadler, Franz Gross
2010-10-01
We provide a short overview of the Covariant Spectator Theory and its applications. The basic ideas are introduced through the example of a {phi}{sup 4}-type theory. High-precision models of the two-nucleon interaction are presented and the results of their use in calculations of properties of the two- and three-nucleon systems are discussed. A short summary of applications of this framework to other few-body systems is also presented.
New covariant Lagrange formulation for field theories
Ootsuka, T
2012-01-01
A novel approach for Lagrange formulation for field theories is proposed in terms of Kawaguchi geometry (areal metric space). On the extended configuration space M for classical field theory composed of spacetime and field configuration space, one can define a geometrical structure called Kawaguchi areal metric K from the field Lagrangian and (M,K) can be regarded as Kawaguchi manifold. The geometrical action functional is given by K and the dynamics of field is determined by covariant Euler-Lagrange equation derived from the variational principle of the action. The solution to the equation becomes a minimal hypersurface on (M,K) which has the same dimension as spacetime. We propose that this hypersurface is what we should regard as our real spacetime manifold, while the usual way to understand spacetime is to consider it as the parameter spacetime (base manifold) of a fibre bundle. In this way, the dynamics of field and spacetime structure is unified by Kawaguchi geometry. The theory has the property of stro...
Particle vibrational coupling in covariant density functional theory
Ring, P; 10.1134/S1063778809080055
2009-01-01
A consistent combination of covariant density functional theory (CDFT) and Landau-Migdal Theory of Finite Fermi Systems (TFFS) is presented. Both methods are in principle exact, but Landau-Migdal theory cannot describe ground state properties and density functional theory does not take into account the energy dependence of the self-energy and therefore fails to yield proper single-% particle spectra as well as the coupling to complex configurations in the width of giant resonances. Starting from an energy functional, phonons and their vertices are calculated without any further parameters. They form the basis of particle-vibrational coupling leading to an energy dependence of the self-energy and an induced energy-dependent interaction in the response equation. A subtraction procedure avoids double counting. Applications in doubly magic nuclei and in a chain of superfluid nuclei show excellent agreement with experimental data.
Optimal covariate designs theory and applications
Das, Premadhis; Mandal, Nripes Kumar; Sinha, Bikas Kumar
2015-01-01
This book primarily addresses the optimality aspects of covariate designs. A covariate model is a combination of ANOVA and regression models. Optimal estimation of the parameters of the model using a suitable choice of designs is of great importance; as such choices allow experimenters to extract maximum information for the unknown model parameters. The main emphasis of this monograph is to start with an assumed covariate model in combination with some standard ANOVA set-ups such as CRD, RBD, BIBD, GDD, BTIBD, BPEBD, cross-over, multi-factor, split-plot and strip-plot designs, treatment control designs, etc. and discuss the nature and availability of optimal covariate designs. In some situations, optimal estimations of both ANOVA and the regression parameters are provided. Global optimality and D-optimality criteria are mainly used in selecting the design. The standard optimality results of both discrete and continuous set-ups have been adapted, and several novel combinatorial techniques have been applied for...
Leitão, Sofia; Stadler, Alfred; Peña, M. T.; Biernat, Elmar P.
2017-01-01
The Covariant Spectator Theory (CST) is used to calculate the mass spectrum and vertex functions of heavy-light and heavy mesons in Minkowski space. The covariant kernel contains Lorentz scalar, pseudoscalar, and vector contributions. The numerical calculations are performed in momentum space, where special care is taken to treat the strong singularities present in the confining kernel. The observed meson spectrum is very well reproduced after fitting a small number of model parameters. Remarkably, a fit to a few pseudoscalar meson states only, which are insensitive to spin-orbit and tensor forces and do not allow to separate the spin-spin from the central interaction, leads to essentially the same model parameters as a more general fit. This demonstrates that the covariance of the chosen interaction kernel is responsible for the very accurate prediction of the spin-dependent quark-antiquark interactions.
Leitão, Sofia; Peña, M T; Biernat, Elmar P
2016-01-01
The Covariant Spectator Theory (CST) is used to calculate the mass spectrum and vertex functions of heavy-light and heavy mesons in Minkowski space. The covariant kernel contains Lorentz scalar, pseudoscalar, and vector contributions. The numerical calculations are performed in momentum space, where special care is taken to treat the strong singularities present in the confining kernel. The observed meson spectrum is very well reproduced after fitting a small number of model parameters. Remarkably, a fit to a few pseudoscalar meson states only, which are insensitive to spin-orbit and tensor forces and do not allow to separate the spin-spin from the central interaction, leads to essentially the same model parameters as a more general fit. This demonstrates that the covariance of the chosen interaction kernel is responsible for the very accurate prediction of the spin-dependent quark-antiquark interactions.
Duality Covariant Solutions in Extended Field Theories
Rudolph, Felix J
2016-01-01
Double field theory and exceptional field theory are formulations of supergravity that make certain dualities manifest symmetries of the action. To achieve this, the geometry is extended by including dual coordinates corresponding to winding modes of the fundamental objects. This geometrically unifies the spacetime metric and the gauge fields (and their local symmetries) in a generalized geometry. Solutions to these extended field theories take the simple form of waves and monopoles in the extended space. From a supergravity point of view they appear as 1/2 BPS objects such as the string, the membrane and the fivebrane in ordinary spacetime. In this thesis double field theory and exceptional field theory are introduced, solutions to their equations of motion are constructed and their properties are analyzed. Further it is established how isometries in the extended space give rise to duality relations between the supergravity solutions. Extensions to these core ideas include studying Goldstone modes, probing s...
Covariant density functional theory for nuclear matter
Energy Technology Data Exchange (ETDEWEB)
Badarch, U.
2007-07-01
The present thesis is organized as follows. In Chapter 2 we study the Nucleon-Nucleon (NN) interaction in Dirac-Brueckner (DB) approach. We start by considering the NN interaction in free-space in terms of the Bethe-Salpeter (BS) equation to the meson exchange potential model. Then we present the DB approach for nuclear matter by extending the BS equation for the in-medium NN interaction. From the solution of the three-dimensional in-medium BS equation, we derive the DB self-energies and total binding energy which are the main results of the DB approach, which we later incorporate in the field theoretical calculation of the nuclear equation of state. In Chapter 3, we introduce the basic concepts of density functional theory in the context of Quantum Hadrodynamics (QHD-I). We reach the main point of this work in Chapter 4 where we introduce the DDRH approach. In the DDRH theory, the medium dependence of the meson-nucleon vertices is expressed as functionals of the baryon field operators. Because of the complexities of the operator-valued functionals we decide to use the mean-field approximation. In Chapter 5, we contrast microscopic and phenomenological approaches to extracting density dependent meson-baryon vertices. Chapter 6 gives the results of our studies of the EOS of infinite nuclear matter in detail. Using formulas derived in Chapters 4 and 5 we calculate the properties of symmetric and asymmetric nuclear matter and pure neutron matter. (orig.)
Batalin-Vilkovisky formalism in locally covariant field theory
Rejzner, Katarzyna
2011-01-01
The present work contains a complete formulation of the Batalin-Vilkovisky (BV) formalism in the framework of locally covariant field theory. In the first part of the thesis the classical theory is investigated with a particular focus on the infinite dimensional character of the underlying structures. It is shown that the use of infinite dimensional differential geometry allows for a conceptually clear and elegant formulation. The construction of the BV complex is performed in a fully covariant way and we also generalize the BV framework to a more abstract level, using functors and natural transformations. In this setting we construct the BV complex for classical gravity. This allows us to give a homological interpretation to the notion of diffeomorphism invariant physical quantities in general relativity. The second part of the thesis concerns the quantum theory. We provide a framework for the BV quantization that doesn't rely on the path integral formalism, but is completely formulated within perturbative a...
Batalin-Vilkovisky formalism in locally covariant field theory
Energy Technology Data Exchange (ETDEWEB)
Rejzner, Katarzyna Anna
2011-12-15
The present work contains a complete formulation of the Batalin-Vilkovisky (BV) formalism in the framework of locally covariant field theory. In the first part of the thesis the classical theory is investigated with a particular focus on the infinite dimensional character of the underlying structures. It is shown that the use of infinite dimensional differential geometry allows for a conceptually clear and elegant formulation. The construction of the BV complex is performed in a fully covariant way and we also generalize the BV framework to a more abstract level, using functors and natural transformations. In this setting we construct the BV complex for classical gravity. This allows us to give a homological interpretation to the notion of diffeomorphism invariant physical quantities in general relativity. The second part of the thesis concerns the quantum theory. We provide a framework for the BV quantization that doesn't rely on the path integral formalism, but is completely formulated within perturbative algebraic quantum field theory. To make such a formulation possible we first prove that the renormalized time-ordered product can be understood as a binary operation on a suitable domain. Using this result we prove the associativity of this product and provide a consistent framework for the renormalized BV structures. In particular the renormalized quantum master equation and the renormalized quantum BV operator are defined. To give a precise meaning to theses objects we make a use of the master Ward identity, which is an important structure in causal perturbation theory. (orig.)
Covariant density functional theory: Reexamining the structure of superheavy nuclei
Agbemava, S E; Nakatsukasa, T; Ring, P
2015-01-01
A systematic investigation of even-even superheavy elements in the region of proton numbers $100 \\leq Z \\leq 130$ and in the region of neutron numbers from the proton-drip line up to neutron number $N=196$ is presented. For this study we use five most up-to-date covariant energy density functionals of different types, with a non-linear meson coupling, with density dependent meson couplings, and with density-dependent zero-range interactions. Pairing correlations are treated within relativistic Hartree-Bogoliubov (RHB) theory based on an effective separable particle-particle interaction of finite range and deformation effects are taken into account. This allows us to assess the spread of theoretical predictions within the present covariant models for the binding energies, deformation parameters, shell structures and $\\alpha$-decay half-lives. Contrary to the previous studies in covariant density functional theory, it was found that the impact of $N=172$ spherical shell gap on the structure of superheavy elemen...
Khoury, Justin; Tolley, Andrew J
2014-01-01
Traditional derivations of general relativity from the graviton degrees of freedom assume space-time Lorentz covariance as an axiom. In this essay, we survey recent evidence that general relativity is the unique spatially-covariant effective field theory of the transverse, traceless graviton degrees of freedom. The Lorentz covariance of general relativity, having not been assumed in our analysis, is thus plausibly interpreted as an accidental or emergent symmetry of the gravitational sector. From this point of view, Lorentz covariance is a necessary feature of low-energy graviton dynamics, not a property of space-time. This result has revolutionary implications for fundamental physics.
Lorentz covariant field theory on noncommutative spacetime based on DFR algebra
Okumura, Y
2003-01-01
Lorentz covariance is the fundamental principle of every relativistic field theory which insures consistent physical descriptions. Even if the space-time is noncommutative, field theories on it should keep Lorentz covariance. In this letter, it is shown that the field theory on noncommutative spacetime is Lorentz covariant if the noncommutativity emerges from the algebra of spacetime operators described by Doplicher, Fredenhagen and Roberts.
Second central extension in Galilean covariant field theory
Hagen, C R
2002-01-01
The second central extension of the planar Galilei group has been alleged to have its origin in the spin variable. This idea is explored here by considering local Galilean covariant field theory for free fields of arbitrary spin. It is shown that such systems generally display only a trivial realization of the second central extension. While it is possible to realize any desired value of the extension parameter by suitable redefinition of the boost operator, such an approach has no necessary connection to the spin of the basic underlying field.
Covariant theory of gravitation in the framework of special relativity
Vieira, R S
2016-01-01
Purely from covariance requirements regarding the special theory of relativity, we show that a moving body necessarily generates a gravitational magnetic field. Then, from the Lorentz transformations, we deduce the exact formul{\\ae} describing these gravitomagnetic fields in a flat spacetime. We also show that the gravitational mass should be regarded as an invariant quantity in the same foot as the electric charge. Thus, the differential equations satisfied by the gravitomagnetic fields are deduced, which proved to be similar to the Maxwell equations. This allowed us to show that gravitational waves indeed spread out with the speed of light, confirming a result that usually is only guessed. We also show that the gravitational vector potential can be associated to the momentum of interaction between the matter and the gravitomagnetic fields. The energy and momentum stored in the gravitomagnetic fields are also discussed. We highlight that nothing is assumed from the electromagnetic theory in our approach, nev...
Covariant Spectator Theory of np scattering: Isoscalar interaction currents
Gross, Franz
2014-01-01
Using the Covariant Spectator Theory (CST), one boson exchange (OBE) models have been found that give precision fits to low energy np scattering and the deuteron binding energy. The boson-nucleon vertices used in these models contain a momentum dependence that requires a new class of interaction currents for use with electromagnetic interactions. Current conservation requires that these new interaction currents satisfy a two-body Ward-Takahashi identity, and using principals of simplicity and picture independence, these currents can be uniquely determined. The results lead to general formulae for a two-body current that can be expressed in terms of relativistic np wave functions, Psi, and two convenient truncated wave functions, ${\\it \\Psi}^{(2)}$ and $\\widehat {\\it \\Psi}$, which contain all of the information needed for the explicit evaluation of the contributions from the interaction current. These three wave functions can be calculated from the CST bound or scattering state equations (and their off-shell e...
Quantum Gravity from the Point of View of Locally Covariant Quantum Field Theory
Brunetti, Romeo; Fredenhagen, Klaus; Rejzner, Katarzyna
2016-08-01
We construct perturbative quantum gravity in a generally covariant way. In particular our construction is background independent. It is based on the locally covariant approach to quantum field theory and the renormalized Batalin-Vilkovisky formalism. We do not touch the problem of nonrenormalizability and interpret the theory as an effective theory at large length scales.
Spinorial Reduction of the Superdimensional Dual-covariant Field Theory
Derbenev, Yaroslav
2015-01-01
In this paper we produce further specification of the geometric and algebraic properties of the earlier introduced superdimensional dual-covariant field theory (SFT) in a N-dimensional manifold [1] as an approach to a unified field theory (UFT). Considerations in the present paper are directed by a requirement of transformational invariance of connections of derivatives of dual state vector (DSV) and unified gauge field (UGF matrices) to these objects themselves established by mean of N split metric matrices of a rank {\\mu} (SM, an extended analog of Dirac matrices) in frame of the related Euler-Lagrange equations for DSV, UGF and SM derived in [1]. This requirement is posed on SFT as one of the aspects of the general demand of irreducibility claimed to UFT; it leads to rotational invariance of SM and grand metric tensor (GM) as being structured on SM. Study in this work has led to explication of geometrical nature of SM and DSV as spin-affinors (variable in space of the unified manifold) and dual spin-field,...
Covariant Spectator Theory of np scattering: Isoscalar interaction currents
Energy Technology Data Exchange (ETDEWEB)
Gross, Franz L. [JLAB
2014-06-01
Using the Covariant Spectator Theory (CST), one boson exchange (OBE) models have been found that give precision fits to low energy $np$ scattering and the deuteron binding energy. The boson-nucleon vertices used in these models contain a momentum dependence that requires a new class of interaction currents for use with electromagnetic interactions. Current conservation requires that these new interaction currents satisfy a two-body Ward-Takahashi (WT), and using principals of {\\it simplicity\\/} and {\\it picture independence\\/}, these currents can be uniquely determined. The results lead to general formulae for a two-body current that can be expressed in terms of relativistic $np$ wave functions, ${\\it \\Psi}$, and two convenient truncated wave functions, ${\\it \\Psi}^{(2)}$ and $\\widehat {\\it \\Psi}$, which contain all of the information needed for the explicit evaluation of the contributions from the interaction current. These three wave functions can be calculated from the CST bound or scattering state equations (and their off-shell extrapolations). A companion paper uses this formalism to evaluate the deuteron magnetic moment.
Worldline construction of a covariant chiral kinetic theory
Mueller, Niklas; Venugopalan, Raju
2017-07-01
We discuss a novel worldline framework for computations of the chiral magnetic effect (CME) in ultrarelativistic heavy-ion collisions. Starting from the fermion determinant in the QCD effective action, we show explicitly how its real part can be expressed as a supersymmetric worldline action of spinning, colored, Grassmannian particles in background fields. Restricting ourselves for simplicity to spinning particles, we demonstrate how their constrained Hamiltonian dynamics arises for both massless and massive particles. In a semiclassical limit, this gives rise to the covariant generalization of the Bargmann-Michel-Telegdi equation; the derivation of the corresponding Wong equations for colored particles is straightforward. In a previous paper [N. Mueller and R. Venugopalan, arXiv:1701.03331.], we outlined how Berry's phase arises in a nonrelativistic adiabatic limit for massive particles. We extend the discussion here to systems with a finite chemical potential. We discuss a path integral formulation of the relative phase in the fermion determinant that places it on the same footing as the real part. We construct the corresponding anomalous worldline axial-vector current and show in detail how the chiral anomaly appears. Our work provides a systematic framework for a relativistic kinetic theory of chiral fermions in the fluctuating topological backgrounds that generate the CME in a deconfined quark-gluon plasma. We outline some further applications of this framework in many-body systems.
Theory of Covariance Equivalent ARMAV Models of Civil Engineering Structures
DEFF Research Database (Denmark)
Andersen, P.; Brincker, Rune; Kirkegaard, Poul Henning
1996-01-01
In this paper the theoretical background for using covariance equivalent ARMAV models in modal analysis is discussed. It is shown how to obtain a covariance equivalent ARMA model for a univariate linear second order continous-time system excited by Gaussian white noise. This result is generalized...
Theory of Covariance Equivalent ARMAV Models of Civil Engineering Structures
DEFF Research Database (Denmark)
Andersen, P.; Brincker, Rune; Kirkegaard, Poul Henning
In this paper the theoretical background for using covariance equivalent ARMAV models in modal analysis is discussed. It is shown how to obtain a covariance equivalent ARMA model for a univariate linear second order continuous-time system excited by Gaussian white noise. This result is generalize...
Theory of Covariance Equivalent ARMAV Models of Civil Engineering Structures
DEFF Research Database (Denmark)
Andersen, P.; Brincker, Rune; Kirkegaard, Poul Henning
1996-01-01
In this paper the theoretical background for using covariance equivalent ARMAV models in modal analysis is discussed. It is shown how to obtain a covariance equivalent ARMA model for a univariate linear second order continous-time system excited by Gaussian white noise. This result is generalized...
Osp(1,2)-covariant Lagrangian quantization of general gauge theories
Energy Technology Data Exchange (ETDEWEB)
Geyer, B.; Lavrov, P.M. [Universitat Leipzig, Naturwissenschaftlich-Theoretisches Zentrum, Leipzig (Germany); Muelsch, D. [Wissenschaftszentrum Leipzig e.V., Leipzig (Germany)
1998-10-01
An osp(1, 2)-covariant Lagrangian quantization of general gauge theories is introduced which also applies to massive fields. It generalizes the Batalin-Vilkovisky and the Sp(2)-covariant field-antifield approach and guarantees symplectic invariance of the quantized action. Massive gauge theories with closed algebra are considered as an example. (author)
Accuracy of Pseudo-Inverse Covariance Learning--A Random Matrix Theory Analysis.
Hoyle, David C
2011-07-01
For many learning problems, estimates of the inverse population covariance are required and often obtained by inverting the sample covariance matrix. Increasingly for modern scientific data sets, the number of sample points is less than the number of features and so the sample covariance is not invertible. In such circumstances, the Moore-Penrose pseudo-inverse sample covariance matrix, constructed from the eigenvectors corresponding to nonzero sample covariance eigenvalues, is often used as an approximation to the inverse population covariance matrix. The reconstruction error of the pseudo-inverse sample covariance matrix in estimating the true inverse covariance can be quantified via the Frobenius norm of the difference between the two. The reconstruction error is dominated by the smallest nonzero sample covariance eigenvalues and diverges as the sample size becomes comparable to the number of features. For high-dimensional data, we use random matrix theory techniques and results to study the reconstruction error for a wide class of population covariance matrices. We also show how bagging and random subspace methods can result in a reduction in the reconstruction error and can be combined to improve the accuracy of classifiers that utilize the pseudo-inverse sample covariance matrix. We test our analysis on both simulated and benchmark data sets.
Hamiltonian approach to GR - Part 1: covariant theory of classical gravity
Cremaschini, Claudio
2016-01-01
A challenging issue in General Relativity concerns the determination of the manifestly-covariant continuum Hamiltonian structure underlying the Einstein field equations and the related formulation of the corresponding covariant Hamilton-Jacobi theory. The task is achieved by adopting a synchronous variational principle requiring distinction between the prescribed deterministic metric tensor $\\hat{g}(r)\\equiv \\left\\{ \\hat{g}_{\\mu \
Spatially Covariant Theories of a Transverse, Traceless Graviton, Part I: Formalism
Khoury, Justin; Tolley, Andrew J
2011-01-01
General relativity is a covariant theory of two transverse, traceless graviton degrees of freedom. According to a theorem of Hojman, Kuchar, and Teitelboim, modifications of general relativity must either introduce new degrees of freedom or violate the principle of general covariance. In this paper, we explore modifications of general relativity that retain the same number of gravitational degrees of freedom, and therefore explicitly break general covariance. Motivated by cosmology, the modifications of interest maintain spatial covariance. Demanding consistency of the theory forces the physical Hamiltonian density to obey an analogue of the renormalization group equation. In this context, the equation encodes the invariance of the theory under flow through the space of conformally equivalent spatial metrics. This paper is dedicated to setting up the formalism of our approach and applying it to a realistic class of theories. Forthcoming work will apply the formalism more generally.
Perales, José C; Catena, Andrés; Shanks, David R; González, José A
2005-09-01
A number of studies using trial-by-trial learning tasks have shown that judgments of covariation between a cue c and an outcome o deviate from normative metrics. Parameters based on trial-by-trial predictions were estimated from signal detection theory (SDT) in a standard causal learning task. Results showed that manipulations of P(c) when contingency (deltaP) was held constant did not affect participants' ability to predict the appearance of the outcome (d') but had a significant effect on response criterion (c) and numerical causal judgments. The association between criterion c and judgment was further demonstrated in 2 experiments in which the criterion was directly manipulated by linking payoffs to the predictive responses made by learners. In all cases, the more liberal the criterion c was, the higher judgments were. The results imply that the mechanisms underlying the elaboration of judgments and those involved in the elaboration of predictive responses are partially dissociable.
Coincidence and covariance data acquisition in photoelectron and -ion spectroscopy. I. Formal theory
Mikosch, Jochen; Patchkovskii, Serguei
2013-10-01
We derive a formal theory of noisy Poisson processes with multiple outcomes. We obtain simple, compact expressions for the probability distribution function of arbitrarily complex composite events and its moments. We illustrate the utility of the theory by analyzing properties of coincidence and covariance photoelectron-photoion detection involving single-ionization events. The results and techniques introduced in this work are directly applicable to more general coincidence and covariance experiments, including multiple ionization and multiple-ion fragmentation pathways.
Hydrographic responses to regional covariates across the Kara Sea
Mäkinen, Jussi; Vanhatalo, Jarno
2016-12-01
The Kara Sea is a shelf sea in the Arctic Ocean which has a strong spatiotemporal hydrographic variation driven by river discharge, air pressure, and sea ice. There is a lack of information about the effects of environmental variables on surface hydrography in different regions of the Kara Sea. We use a hierarchical spatially varying coefficient model to study the variation of sea surface temperature (SST) and salinity (SSS) in the Kara Sea between years 1980 and 2000. The model allows us to study the effects of climatic (Arctic oscillation index (AO)) and seasonal (river discharge and ice concentration) environmental covariates on hydrography. The hydrographic responses to covariates vary considerably between different regions of the Kara Sea. River discharge decreases SSS in the shallow shelf area and has a neutral effect in the northern Kara Sea. The responses of SST and SSS to AO show the effects of different wind and air pressure conditions on water circulation and hence on hydrography. Ice concentration has a constant effect across the Kara Sea. We estimated the average SST and SSS in the Kara Sea in 1980-2000. The average August SST over the Kara Sea in 1995-2000 was higher than the respective average in 1980-1984 with 99.9% probability and August SSS decreased with 77% probability between these time periods. We found a support that the winter season AO has an impact on the summer season hydrography, and temporal trends may be related to the varying level of winter season AO index.
Covariant gauges without Gribov ambiguities in Yang-Mills theories
Serreau, Julien; Tresmontant, Andréas
2013-01-01
We propose a formulation of a certain class of nonlinear covariant gauges as an extremization procedure that can be implemented on the lattice. At high energies, where the Gribov ambiguities can be ignored, this reduces to the Curci-Ferrari-Delbourgo-Jarvis gauges. We further propose a continuum formulation in terms of a local action which is free of Gribov ambiguities and avoids the Neuberger zero problem of the standard Faddeev-Popov construction. This involves an averaging over Gribov copies with a nonuniform weight, which introduces a new gauge-fixing parameter. We show that the proposed gauge-fixed action is perturbatively renormalizable in four dimensions and we provide explicit expressions of the renormalization factors at one loop. We discuss the possible implications of the present proposal for the calculation of Yang-Mills correlators.
Covariant gauges without Gribov ambiguities in Yang-Mills theories
Serreau, J.; Tissier, M.; Tresmontant, A.
2014-06-01
We propose a one-parameter family of nonlinear covariant gauges which can be formulated as an extremization procedure that may be amenable to lattice implementation. At high energies, where the Gribov ambiguities can be ignored, this reduces to the Curci-Ferrari-Delbourgo-Jarvis gauges. We further propose a continuum formulation in terms of a local action which is free of Gribov ambiguities and avoids the Neuberger zero problem of the standard Faddeev-Popov construction. This involves an averaging over Gribov copies with a nonuniform weight, which introduces a new gauge-fixing parameter. We show that the proposed gauge-fixed action is perturbatively renormalizable in four dimensions and we provide explicit expressions of the renormalization factors at one loop. We discuss the possible implications of the present proposal for the calculation of Yang-Mills correlators.
Masses and magnetic moments of ground-state baryons in covariant baryon chiral perturbation theory
Geng, L S; Alvarez-Ruso, L; Vicente-Vacas, M J
2012-01-01
We report on some recent developments in our understanding of the light-quark mass dependence and the SU(3) flavor symmetry breaking corrections to the magnetic moments of the ground-state baryons in a covariant formulation of baryon chiral perturbation theory, the so-called EOMS formulation. We show that this covariant ChPT exhibits some promising features compared to its heavy-baryon and infrared counterparts.
Locally covariant quantum field theory with external sources
Fewster, Christopher J
2014-01-01
We provide a detailed analysis of the classical and quantized theory of a multiplet of inhomogeneous Klein-Gordon fields, which couple to the spacetime metric and also to an external source term; thus the solutions form an affine space. Following the formulation of affine field theories in terms of presymplectic vector spaces as proposed in [Annales Henri Poincare 15, 171 (2014)], we determine the relative Cauchy evolution induced by metric as well as source term perturbations and compute the automorphism group of natural isomorphisms of the presymplectic vector space functor. Two pathological features of this formulation are revealed: the automorphism group contains elements that cannot be interpreted as global gauge transformations of the theory; moreover, the presymplectic formulation does not respect a natural requirement on composition of subsystems. We therefore propose a systematic strategy to improve the original description of affine field theories at the classical and quantized level, first passing ...
Hamiltonian approach to GR - Part 2: covariant theory of quantum gravity
Cremaschini, Claudio
2016-01-01
A non-perturbative quantum field theory of General Relativity is presented which leads to a new realization of the theory of Covariant Quantum-Gravity (CQG-theory). The treatment is founded on the recently-identified Hamiltonian structure associated with the classical space-time, i.e., the corresponding manifestly-covariant Hamilton equations and the related Hamilton-Jacobi theory. As shown here the connection with CQG-theory is achieved via the classical GR Hamilton-Jacobi equation, leading to the realization of the CQG-wave equation in 4-scalar form for the corresponding CQG-state and wave-function. The new quantum wave equation exhibits well-known formal properties characteristic of quantum mechanics, including the validity of quantum hydrodynamic equations and suitably-generalized Heisenberg inequalities. In addition, it recovers the classical GR equations in the semiclassical limit, while admitting the possibility of developing further perturbative approximation schemes. Applications of the theory are po...
Quasi-local conserved charges in Lorenz-diffeomorphism covariant theory of gravity
Energy Technology Data Exchange (ETDEWEB)
Adami, H.; Setare, M.R. [University of Kurdistan, Department of Science, Sanandaj (Iran, Islamic Republic of)
2016-04-15
In this paper, using the combined Lorenz-diffeomorphism symmetry, we find a general formula for the quasi-local conserved charge of the covariant gravity theories in a first order formalism of gravity. We simplify the general formula for the Lovelock theory of gravity. Afterwards, we apply the obtained formula on BHT gravity to obtain the energy and angular momentum of the rotating OTT black hole solution in the context of this theory. (orig.)
OSp(1,2)-covariant Lagrangian quantization of irreducible massive gauge theories
Geyer, B; Mülsch, D
1997-01-01
The OSp(1,2)-covariant Lagrangian quantization of general gauge theories is formulated which applies also to massive gauge fields. The formalism generalizes the Sp(2)-covariant BLT approach and guarantees symplectic invariance of the quantized action. The dependence of the generating functional of Green's functions on the choice of gauge in the massive case disappears in the limit m = 0. Ward identities related to OSp(1,2) symmetry are derived. Massive gauge theories with closed algebra are studied as an example.
Manifestly Covariant Gauge-invariant Cosmological Perturbation Theory
Miedema, P G
2010-01-01
It is shown that a first-order cosmological perturbation theory for the open, flat and closed Friedmann-Lemaitre-Robertson-Walker universes admits one, and only one, gauge-invariant variable which describes the perturbation to the energy density and which becomes equal to the usual Newtonian energy density in the non-relativistic limit. The same holds true for the perturbation to the particle number density. Using these two new variables, a new manifestly gauge-invariant cosmological perturbation theory has been developed. Density perturbations evolve diabatically. Perturbations in the total energy density are gravitationally coupled to perturbations in the particle number density, irrespective of the nature of the particles. There is, in first-order, no back-reaction of perturbations to the global expansion of the universe. Small-scale perturbations in the radiation-dominated era oscillate with an increasing amplitude, whereas in older, less precise treatments, oscillating perturbations are found with a decr...
Generally covariant vs. gauge structure for conformal field theories
Energy Technology Data Exchange (ETDEWEB)
Campigotto, M., E-mail: martacostanza.campigotto@to.infn.it [Dipartimento di Fisica, University of Torino, Via P. Giuria 1, 10125, Torino (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Via P. Giuria 1, 10125, Torino (Italy); Fatibene, L. [Dipartimento di Matematica, University of Torino, Via C. Alberto 10, 10123, Torino (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Via P. Giuria 1, 10125, Torino (Italy)
2015-11-15
We introduce the natural lift of spacetime diffeomorphisms for conformal gravity and discuss the physical equivalence between the natural and gauge natural structure of the theory. Accordingly, we argue that conformal transformations must be introduced as gauge transformations (affecting fields but not spacetime point) and then discuss special structures implied by the splitting of the conformal group. -- Highlights: •Both a natural and a gauge natural structure for conformal gravity are defined. •Global properties and natural lift of spacetime transformations are described. •The possible definitions of physical state are considered and discussed. •The gauge natural theory has less physical states than the corresponding natural one. •The dynamics forces to prefer the gauge natural structure over the natural one.
Covariance of dynamic strain responses for structural damage detection
Li, X. Y.; Wang, L. X.; Law, S. S.; Nie, Z. H.
2017-10-01
A new approach to address the practical problems with condition evaluation/damage detection of structures is proposed based on the distinct features of a new damage index. The covariance of strain response function (CoS) is a function of modal parameters of the structure. A local stiffness reduction in structure would cause monotonous increase in the CoS. Its sensitivity matrix with respect to local damages of structure is negative and narrow-banded. The damage extent can be estimated with an approximation to the sensitivity matrix to decouple the identification equations. The CoS sensitivity can be calibrated in practice from two previous states of measurements to estimate approximately the damage extent of a structure. A seven-storey plane frame structure is numerically studied to illustrate the features of the CoS index and the proposed method. A steel circular arch in the laboratory is tested. Natural frequencies changed due to damage in the arch and the damage occurrence can be judged. However, the proposed CoS method can identify not only damage happening but also location, even damage extent without need of an analytical model. It is promising for structural condition evaluation of selected components.
Lompay, Robert R
2013-01-01
Arbitrary diffeomorphically invariant metric-torsion theories of gravity are considered. It is assumed that Lagrangians of such theories contain derivatives of field variables (tensor densities of arbitrary ranks and weights) up to a second order only. The generalized Klein-Noether methods for constructing manifestly covariant identities and conserved quantities are developed. Manifestly covariant expressions are constructed without including auxiliary structures like a background metric. In the Riemann-Cartan space, the following \\emph{manifestly generally covariant results} are presented: (a) The complete generalized system of differential identities (the Klein-Noether identities) is obtained. (b) The generalized currents of three types depending on an arbitrary vector field displacements are constructed: they are the canonical Noether current, symmetrized Belinfante current and identically conserved Hilbert-Bergmann current. In particular, it is stated that the symmetrized Belinfante current does not depen...
Systematic of Nuclear Ground State Properties in Sr Isotope by Covariant Density Functional Theory
Institute of Scientific and Technical Information of China (English)
TIAN; Yuan
2012-01-01
<正>The hyperfine structure and isotope shifts of Sr-isotopes, both even-even and odd-even nuclei, are studied in the covariant density functional theory (DFT) with the new parameter set DD-PC1. Pairing correlation is treated by using the Bogoliubov with a separable form of the pairing interaction. Spin-parity,
Irreducible gauge theories in the framework of the Sp(2)-covariant quantization method
Lavrov, P M; Reshetnyak, A A; Lavrov, P M; Moshin, P Yu; Reshetnyak, A A
1995-01-01
Irreducible gauge theories in both the Lagrangian and Hamiltonian versions of the Sp(2)-covariant quantization method are studied. Solutions to generating equations are obtained in the form of expansions in power series of ghost and auxiliary variables up to the 3d order inclusively.
DEFF Research Database (Denmark)
Codello, Alessandro; Jain, Rajeev Kumar
2017-01-01
Following our previous work wherein the leading order effective action was computed in the covariant effective field theory of gravity, here we specialize the effective action to the FRW spacetime and obtain the effective Friedmann equations. In particular, we focus our attention on studying...
Horwitz, L P; Horwitz, Lawrence P.; Oron, Ori
2004-01-01
We discuss in this Chapter a series of theoretical developments which motivate the introduction of a quantum evolution equation for which the eikonal approximation results in the geodesics of a four dimensional manifold. This geodesic motion can be put into correspondence with general relativity. One obtains in this way a quantum theory on a flat spacetime, obeying the rules of the standard quantum theory in Lorentz covariant form, with a spacetime dependent Lorentz tensor $g_{\\mu\
A new family of covariate-adjusted response adaptive designs and their properties
Institute of Scientific and Technical Information of China (English)
ZHANG Li-Xin; HU Fei-fang
2009-01-01
It is often important to incorporate covariate information in the design of clinical trials. In literature there are many designs of using stratification and covariate-adaptive randomization to balance certain known covaxiate. Recently, some covariate-adjusted response-adaptive (CARA) designs have been proposed and their asymptotic properties have been studied (Ann.Statist. 2007). However, these CARA designs usually have high variabilities. In this paper, a new family of covariate-adjusted response-adaptive (CARA) designs is presented. It is shown that the new designs have less variables and therefore are more efficient.
osp(1,2)-covariant Lagrangian quantization of reducible massive gauge theories
Geyer, B; Mülsch, D
1999-01-01
The osp(1,2)-covariant Lagrangian quantization of irreducible gauge theories [hep-th/9712204] is generalized to L-stage reducible theories. The dependence of the generating functional of Green's functions on the choice of gauge in the massive case is dicussed and Ward identities related to osp(1,2) symmetry are given. Massive first stage theories with closed gauge algebra are studied in detail. The generalization of the Chapline-Manton model and topological Yang-Mills theory to the case of massive fields is consedered as examples.
Conformal generally covariant quantum field theory. The scalar field and its Wick products
Energy Technology Data Exchange (ETDEWEB)
Pinamonti, N. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2008-06-15
In this paper we generalize the construction of generally covariant quantum theories given in [R. Brunetti, K. Fredenhagen, R. Verch, Commun. Math. Phys. 237, 31 (2003)] to encompass the conformal covariant case. After introducing the abstract framework, we discuss the massless conformally coupled Klein Gordon field theory, showing that its quantization corresponds to a functor between two certain categories. At the abstract level, the ordinary fields, could be thought as natural transformations in the sense of category theory. We show that, the Wick monomials without derivatives (Wick powers), can be interpreted as fields in this generalized sense, provided a non trivial choice of the renormalization constants is given. A careful analysis shows that the transformation law of Wick powers is characterized by a weight, and it turns out that the sum of fields with different weights breaks the conformal covariance. At this point there is a difference between the previously given picture due to the presence of a bigger group of covariance. It is furthermore shown that the construction does not depend upon the scale {mu} appearing in the Hadamard parametrix, used to regularize the fields. Finally, we briefly discuss some further examples of more involved fields. (orig.)
Chen, Baojiang; Zhou, Xiao-Hua
2011-09-01
Longitudinal studies often feature incomplete response and covariate data. Likelihood-based methods such as the expectation-maximization algorithm give consistent estimators for model parameters when data are missing at random (MAR) provided that the response model and the missing covariate model are correctly specified; however, we do not need to specify the missing data mechanism. An alternative method is the weighted estimating equation, which gives consistent estimators if the missing data and response models are correctly specified; however, we do not need to specify the distribution of the covariates that have missing values. In this article, we develop a doubly robust estimation method for longitudinal data with missing response and missing covariate when data are MAR. This method is appealing in that it can provide consistent estimators if either the missing data model or the missing covariate model is correctly specified. Simulation studies demonstrate that this method performs well in a variety of situations.
Covariant Renormalizable Anisotropic Theories and Off-Diagonal Einstein-Yang-Mills-Higgs Solutions
Vacaru, Sergiu I
2011-01-01
We use an important decoupling property of gravitational field equations in the general relativity theory and modifications, written with respect to nonholonomic frames with 2+2 spacetime decomposition. This allows us to integrate the Einstein equations in very general forms with generic off--diagonal metrics depending on all spacetime coordinates via generating and integration functions containing (broken and un-broken) symmetry parameters. We associate families of off-diagonal Einstein manifolds to certain classes of covariant gravity theories which have a nice ultraviolet behavior and seem to be (super) renormalizable in a sense of covariant modifications of Ho\\v{r}ava-Lifshits gravity. The apparent breaking of Lorentz invariance is present in some "partner" anisotropically induced theories due to nonlinear coupling with effective parametric interactions determined by nonholonomic constraints and generic off-diagonal gravitational and matter fields configurations. Finally, we show how the constructions can...
Allouba, Hassan
2010-01-01
In a 2006 article (\\cite{A1}), Allouba gave his quadratic covariation differentiation theory for It\\^o's integral calculus. He defined the derivative of a semimartingale with respect to a Brownian motion as the time derivative of their quadratic covariation and a generalization thereof. He then obtained a systematic differentiation theory containing a fundamental theorem of stochastic calculus relating this derivative to It\\^o's integral, a differential stochastic chain rule, a differential stochastic mean value theorem, and other differentiation rules. Here, we use this differentiation theory to obtain variants of the Clark-Ocone and Stroock formulas, with and without change of measure. We prove our variants of the Clark-Ocone formula under $L^{2}$-type conditions; with no Malliavin calculus, without the use of weak distributional or Radon-Nikodym type derivatives, and without the significant machinery of the Hida-Malliavin calculus. Unlike Malliavin or Hida-Malliavin calculi, the form of our variant of the ...
Struckmeier, Jürgen; Vasak, David
2016-01-01
We present the derivation of the Yang-Mills gauge theory based on the covariant Hamiltonian representation of Noether's theorem. As the starting point, we re-formulate our previous presentation of the canonical Hamiltonian derivation of Noether's theorem. The formalism is then applied to derive the Yang-Mills gauge theory. The Noether currents of U(1) and SU(N) gauge theories are derived from the respective infinitesimal generating functions of the pertinent symmetry transformations which maintain the form of the Hamiltonian.
Electromagnetic structure of the low-lying baryons in covariant chiral perturbation theory
Camalich, J Martin; Geng, L S; Vacas, M J Vicente
2009-01-01
We report a calculation of the low-lying baryon magnetic moments using covariant chiral perturbation theory within the extended-on-mass-shell renormalization scheme including intermediate octet and decuplet contributions. For the case of the baryon octet, we succeed to improve the Coleman-Glashow description by including the leading SU(3)$_F$-breaking effects coming from the lowest-order loops. We compare with previous attempts at the same order using heavy-baryon and covariant infrared chiral perturbation theory, and discuss the source of the differences. For the case of the decuplet-baryons we fix the only unknown LEC with the well measured magnetic dipole moment of the $\\Omega^-$ and predict the corresponding ones of the $\\Delta(1232)$ isospin multiplet. In particular we obtain $\\mu_{\\Delta^{++}}=6.0(6) \\mu_N$ and $\\mu_{\\Delta^{+}}=2.84(34) \\mu_N$ that compare well with the current experimental information.
The lowest-lying baryon masses in covariant SU(3)-flavor chiral perturbation theory
Martin-Camalich, J; Vacas, M J Vicente
2010-01-01
We present an analysis of the baryon-octet and -decuplet masses using covariant SU(3)-flavor chiral perturbation theory up to next-to-leading order. Besides the description of the physical masses we address the problem of the lattice QCD extrapolation. Using the PACS-CS collaboration data we show that a good description of the lattice points can be achieved at next-to-leading order with the covariant loop amplitudes and phenomenologically determined values for the meson-baryon couplings. Moreover, the extrapolation to the physical point up to this order is found to be better than the linear one given at leading-order by the Gell-Mann-Okubo approach. The importance that a reliable combination of lattice QCD and chiral perturbation theory may have for hadron phenomenology is emphasized with the prediction of the pion-baryon and strange-baryon sigma terms.
O(D,D) covariant Noether currents and global charges in double field theory
Energy Technology Data Exchange (ETDEWEB)
Park, Jeong-Hyuck [Department of Physics, Sogang University,Seoul, 04107 (Korea, Republic of); Rey, Soo-Jong [School of Physics and Astronomy, Seoul National University,Seoul, 08862 (Korea, Republic of); Fields, Gravity & Strings, Center for Theoretical Physics of the Universe,Institute for Basic Sciences, Daejeon, 34047 (Korea, Republic of); Rim, Woohyun; Sakatani, Yuho [School of Physics and Astronomy, Seoul National University,Seoul, 08862 (Korea, Republic of)
2015-11-20
Double field theory is an approach for massless modes of string theory, unifying and geometrizing all gauge invariance in manifest O(D,D) covariant manner. In this approach, we derive off-shell conserved Noether current and corresponding Noether potential associated with unified gauge invariance. We add Wald-type counter two-form to the Noether potential and define conserved global charges as surface integral. We check our O(D,D) covariant formula against various string backgrounds, both geometric and non-geometric. In all cases we examined, we find perfect agreements with previous results. Our formula facilitates to evaluate momenta along not only ordinary spacetime directions but also dual spacetime directions on equal footing. From this, we confirm recent assertion that null wave in doubled spacetime is the same as macroscopic fundamental string in ordinary spacetime.
Institute of Scientific and Technical Information of China (English)
QIAN Shang-Wu; GU Zhi-Yu
2003-01-01
This article discusses the covariance correlation tensor (CCT) in quantum network theory for four Bell bases in detail. Furthermore, it gives the expression of the density operator in terms of CCT for a quantum network of three nodes, thus gives the criterion of entanglement for this case, i.e. the conditions of complete separability and partial separability for a given quantum state of three bodies. Finally it discusses the general case for the quantum network of m≥3 nodes.
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
Energy Technology Data Exchange (ETDEWEB)
Biernat, Elmer P. [CFTP, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Pena, Maria Teresa [CFTP, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Departamento de FÃsica, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Ribiero, Jose' Emilio F. [CeFEMA, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Stadler, Alfred [Departamento de FÃsica, Universidade de Ãvora, 7000-671 Ãvora, Portugal; Gross, Franz L. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-03-01
We propose a model for the quark-antiquark interaction in Minkowski space using the Covariant Spectator Theory. We show that with an equal-weighted scalar-pseudoscalar structure for the confining part of our interaction kernel the axial-vector Ward-Takahashi identity is preserved and our model complies with the Adler-zero constraint for pi-pi-scattering imposed by chiral symmetry.
Hamiltonian approach to GR. Pt. 1. Covariant theory of classical gravity
Energy Technology Data Exchange (ETDEWEB)
Cremaschini, Claudio [Silesian University in Opava, Faculty of Philosophy and Science, Institute of Physics and Research Center for Theoretical Physics and Astrophysics, Opava (Czech Republic); Tessarotto, Massimo [University of Trieste, Department of Mathematics and Geosciences, Trieste (Italy); Silesian University in Opava, Faculty of Philosophy and Science, Institute of Physics, Opava (Czech Republic)
2017-05-15
A challenging issue in General Relativity concerns the determination of the manifestly covariant continuum Hamiltonian structure underlying the Einstein field equations and the related formulation of the corresponding covariant Hamilton-Jacobi theory. The task is achieved by adopting a synchronous variational principle requiring distinction between the prescribed deterministic metric tensor g(r) ≡ {g_μ_ν(r)} solution of the Einstein field equations which determines the geometry of the background space-time and suitable variational fields x ≡ {g,π} obeying an appropriate set of continuum Hamilton equations, referred to here as GR-Hamilton equations. It is shown that a prerequisite for reaching such a goal is that of casting the same equations in evolutionary form by means of a Lagrangian parametrization for a suitably reduced canonical state. As a result, the corresponding Hamilton-Jacobi theory is established in manifestly covariant form. Physical implications of the theory are discussed. These include the investigation of the structural stability of the GR-Hamilton equations with respect to vacuum solutions of the Einstein equations, assuming that wave-like perturbations are governed by the canonical evolution equations. (orig.)
The 5D Fully-Covariant Theory of Gravitation and Its Astrophysical Applications
Directory of Open Access Journals (Sweden)
Tianxi Zhang
2014-12-01
Full Text Available In this paper, we comprehensively review the five-dimensional (5D fully-covariant theory of gravitation developed by Zhang two decades ago and its recent applications in astrophysics and cosmology. This 5D gravity describes not only the fields, but also the matter and its motion in a 5D spacetime. The greatest advantage of this theory is that there does not exist any unknown parameter, so that we can apply it to explain astrophysical and cosmological issues by quantitatively comparing the results obtained from it with observations and to predict new effects that could not be derived from any other gravitational theories. First, the 5D covariant description of matter and its motion enabled Zhang to analytically derive the fifteenth component of the 5D energy-momentum tensor of matter ( T - 44 , which significantly distinguishes this 5D gravity from other 5D gravitational theories that usually assumed a T - 44 with an unknown parameter, called the scalar charge s, and, thus, to split the 5D covariant field equation into (4 + 1 splitting form as the gravitational, electromagnetic, and scalar field equations. The gravitational field equation turns into the 4D Einstein’s field equation of general relativity if the scalar field is equal to unity. Then, Zhang solved the field equations and obtained an exact static spherically-symmetric external solution of the gravitational, electromagnetic and scalar fields, in which all integral constants were completely determined with a perfect set of simple numbers and parameters that only depend on the mass and electric charge of the matter, by comparing with the obtained weak internal solution of the fields at a large radial distance. In the Einstein frame, the exact field solution obtained from the 5D fully-covariant theory of gravitation reduces to the Schwarzschild solution when the matter is electrically neutral and the fields are weak in strength. This guarantees that the four fundamental tests (light
Chen, Baojiang; Zhou, Xiao-Hua
2011-01-01
Longitudinal studies often feature incomplete response and covariate data. Likelihood-based methods such as the expectation–maximization algorithm give consistent estimators for model parameters when data are missing at random (MAR) provided that the response model and the missing covariate model are correctly specified; however, we do not need to specify the missing data mechanism. An alternative method is the weighted estimating equation, which gives consistent estimators if the missing dat...
Hamiltonian approach to GR. Pt. 2. Covariant theory of quantum gravity
Energy Technology Data Exchange (ETDEWEB)
Cremaschini, Claudio [Faculty of Philosophy and Science, Silesian University in Opava, Institute of Physics and Research Center for Theoretical Physics and Astrophysics, Opava (Czech Republic); Tessarotto, Massimo [University of Trieste, Department of Mathematics and Geosciences, Trieste (Italy); Faculty of Philosophy and Science, Silesian University in Opava, Institute of Physics, Opava (Czech Republic)
2017-05-15
A non-perturbative quantum field theory of General Relativity is presented which leads to a new realization of the theory of covariant quantum gravity (CQG-theory). The treatment is founded on the recently identified Hamiltonian structure associated with the classical space-time, i.e., the corresponding manifestly covariant Hamilton equations and the related Hamilton-Jacobi theory. The quantum Hamiltonian operator and the CQG-wave equation for the corresponding CQG-state and wave function are realized in 4-scalar form. The new quantum wave equation is shown to be equivalent to a set of quantum hydrodynamic equations which warrant the consistency with the classical GR Hamilton-Jacobi equation in the semiclassical limit. A perturbative approximation scheme is developed, which permits the adoption of the harmonic oscillator approximation for the treatment of the Hamiltonian potential. As an application of the theory, the stationary vacuum CQG-wave equation is studied, yielding a stationary equation for the CQG-state in terms of the 4-scalar invariant-energy eigenvalue associated with the corresponding approximate quantum Hamiltonian operator. The conditions for the existence of a discrete invariant-energy spectrum are pointed out. This yields a possible estimate for the graviton mass together with a new interpretation about the quantum origin of the cosmological constant. (orig.)
Spherically symmetric vacuum in covariant F (T )=T +α/2 T2+O (Tγ) gravity theory
DeBenedictis, Andrew; Ilijić, Saša
2016-12-01
Recently, a fully covariant version of the theory of F (T ) torsion gravity has been introduced by M. Kršśák and E. Saridakis [Classical Quantum Gravity 33, 115009 (2016)]. In covariant F (T ) gravity, the Schwarzschild solution is not a vacuum solution for F (T )≠T , and therefore determining the spherically symmetric vacuum is an important open problem. Within the covariant framework, we perturbatively solve the spherically symmetric vacuum gravitational equations around the Schwarzschild solution for the scenario with F (T )=T +(α /2 )T2 , representing the dominant terms in theories governed by Lagrangians analytic in the torsion scalar. From this, we compute the perihelion shift correction to solar system planetary orbits as well as perturbative gravitational effects near neutron stars. This allows us to set an upper bound on the magnitude of the coupling constant, α , which governs deviations from general relativity. We find the bound on this nonlinear torsion coupling constant by specifically considering the uncertainty in the perihelion shift of Mercury. We also analyze a bound from a similar comparison with the periastron orbit of the binary pulsar PSR J0045-7319 as an independent check for consistency. Setting bounds on the dominant nonlinear coupling is important in determining if other effects in the Solar System or greater universe could be attributable to nonlinear torsion.
Covariant Effective Field Theory of Gravity I: Formalism and Curvature expansion
Codello, Alessandro
2015-01-01
We construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime.
Random matrix theory and robust covariance matrix estimation for financial data
Frahm, G; Frahm, Gabriel; Jaekel, Uwe
2005-01-01
The traditional class of elliptical distributions is extended to allow for asymmetries. A completely robust dispersion matrix estimator (the `spectral estimator') for the new class of `generalized elliptical distributions' is presented. It is shown that the spectral estimator corresponds to an M-estimator proposed by Tyler (1983) in the context of elliptical distributions. Both the generalization of elliptical distributions and the development of a robust dispersion matrix estimator are motivated by the stylized facts of empirical finance. Random matrix theory is used for analyzing the linear dependence structure of high-dimensional data. It is shown that the Marcenko-Pastur law fails if the sample covariance matrix is considered as a random matrix in the context of elliptically distributed and heavy tailed data. But substituting the sample covariance matrix by the spectral estimator resolves the problem and the Marcenko-Pastur law remains valid.
Dynamical Relativistic Systems and the Generalized Gauge Fields of Manifestly Covariant Theories
Horwitz, L P
1998-01-01
The problem of the classical non-relativistic electromagnetically kicked oscillator can be cast into the form of an iterative map on phase space. The original work of Zaslovskii et al showed that the resulting evolution contains a stochastic flow in phase space to unbounded energy. Subsequent studies have formulated the problem in terms of a relativistically charged particle in interaction with the electromagnetic field. We review the standard derivation of the covariant Lorentz force, and review the structure of the relativistic equations used to study this problem. We show that the Lorentz force equation can be derived as well from the manifestly covariant mechanics of Stueckelberg in the presence of a standard Maxwell field. We show how this agreement is achieved, and criticize some of the fundamental assumptions underlying these derivations. We argue that a more complete theory, involving ``off-shell'' electromagnetic fields should be utilized. We then discuss the formulation of the off-shell electromagne...
On the covariant formalism of the effective field theory of gravity and leading order corrections
DEFF Research Database (Denmark)
Codello, Alessandro; Jain, Rajeev Kumar
2016-01-01
We construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well...... as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology...... on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime....
On the covariant formalism of the effective field theory of gravity and leading order corrections
Codello, Alessandro; Jain, Rajeev Kumar
2016-11-01
We construct the covariant effective field theory of gravity as an expansion in inverse powers of the Planck mass, identifying the leading and next-to-leading quantum corrections. We determine the form of the effective action for the cases of pure gravity with cosmological constant as well as gravity coupled to matter. By means of heat kernel methods we renormalize and compute the leading quantum corrections to quadratic order in a curvature expansion. The final effective action in our covariant formalism is generally non-local and can be readily used to understand the phenomenology on different spacetimes. In particular, we point out that on curved backgrounds the observable leading quantum gravitational effects are less suppressed than on Minkowski spacetime.
Hyperon effects in covariant density functional theory with recent astrophysical observations
Long, W H; Hagino, K; Sagawa, H; Tamura, H
2011-01-01
Motivated by recent observational data, the equations of state with the inclusion of strangeness-bearing $\\Lambda$-hyperons and the corresponding properties of neutron stars are studied, based on the covariant density functional (CDF) theory. To this end, we specifically employ the density dependent relativistic Hartree-Fock (DDRHF) theory and the relativistic mean field theory (RMF). The inclusion of $\\Lambda$-hyperons in neutron stars shows substantial effects in softening the equation of state. Because of the extra suppression effect originated from the Fock channel, large reductions on both the star mass and radius are predicted by the DDRHF calculations. It is also found that the mass-radius relations of neutron stars with $\\Lambda$-hyperons determined by DDRHF with the PKA1 parameter set are in fairly good agreement with the observational data where a relatively small neutron stars radius is required. Therefore, it is expected that the exotic degrees of freedom such as the strangeness-bearing structure ...
Generalizability theory and item response theory
Glas, Cornelis A.W.; Eggen, T.J.H.M.; Veldkamp, B.P.
2012-01-01
Item response theory is usually applied to items with a selected-response format, such as multiple choice items, whereas generalizability theory is usually applied to constructed-response tasks assessed by raters. However, in many situations, raters may use rating scales consisting of items with a
Generalizability theory and item response theory
Glas, C.A.W.; Eggen, T.J.H.M.; Veldkamp, B.P.
2012-01-01
Item response theory is usually applied to items with a selected-response format, such as multiple choice items, whereas generalizability theory is usually applied to constructed-response tasks assessed by raters. However, in many situations, raters may use rating scales consisting of items with a s
Tanaka, S
2004-01-01
Noncommutative field theory on Yang's quantized space-time algebra (YSTA) is studied. It gives a theoretical framework to reformulate the matrix model as quantum mechanics of $D_0$ branes in a Lorentz-covariant form. The so-called kinetic term ($\\sim {\\hat{P_i}}^2)$ and potential term ($\\sim {[\\hat{X_i},\\hat{X_j}]}^2)$ of $D_0$ branes in the matrix model are described now in terms of Casimir operator of $SO(D,1)$, a subalgebra of the primary algebra $SO(D+1,1)$ which underlies YSTA with two contraction- parameters, $\\lambda$ and $R$. $D$-dimensional noncommutative space-time and momentum operators $\\hat{X_\\mu}$ and $\\hat{P_\\mu}$ in YSTA show a distinctive spectral structure, that is, space-components $\\hat{X_i}$ and $\\hat{P_i}$ have discrete eigenvalues, and time-components $\\hat{X_0}$ and $\\hat{P_0}$ continuous eigenvalues, consistently with Lorentz-covariance. According to the method of Lorentz-covariant Moyal star product proper to YSTA, the field equation of $D_0$ brane on YSTA is derived in a nontrivial ...
Ristorcelli, J. R.
1995-01-01
The mathematical consequences of a few simple scaling assumptions about the effects of compressibility are explored using a simple singular perturbation idea and the methods of statistical fluid mechanics. Representations for the pressure-dilation and dilatational dissipation covariances appearing in single-point moment closures for compressible turbulence are obtained. While the results are expressed in the context of a second-order statistical closure they provide some interesting and very clear physical metaphors for the effects of compressibility that have not been seen using more traditional linear stability methods. In the limit of homogeneous turbulence with quasi-normal large-scales the expressions derived are - in the low turbulent Mach number limit - asymptotically exact. The expressions obtained are functions of the rate of change of the turbulence energy, its correlation length scale, and the relative time scale of the cascade rate. The expressions for the dilatational covariances contain constants which have a precise and definite physical significance; they are related to various integrals of the longitudinal velocity correlation. The pressure-dilation covariance is found to be a nonequilibrium phenomena related to the time rate of change of the internal energy and the kinetic energy of the turbulence. Also of interest is the fact that the representation for the dilatational dissipation in turbulence, with or without shear, features a dependence on the Reynolds number. This article is a documentation of an analytical investigation of the implications of a pseudo-sound theory for the effects of compressibility.
Spatially Homogeneous Bianchi Type V Cosmological Model in the Scale-Covariant Theory of Gravitation
Institute of Scientific and Technical Information of China (English)
Shri Ram; M.K.Verma; Mohd.Zeyauddin
2009-01-01
We discuss spatially homogeneous and anisotropic Bianchi type-V spacetime filled with a perfect fluid in the framework of the scaie-covariant theory of gravitation proposed by Canuto et al.By applying the law of variation for Hubble's parameter,exact solutions of the field equations are obtained,which correspond to the model of the universe having a big-bang type singularity at the initial time t=0.The cosmological model,evolving from the initial singularity,expands with power-law expansion and gives essentially an empty space for a large time.The physical and dynamical properties of the model are also discussed.
Electromagnetic structure of the Delta baryon within the covariant spectator theory
Energy Technology Data Exchange (ETDEWEB)
M. T. Pena, G. Ramalho, Franz Gross
2010-12-01
We calculated all the electromagnetic observables for the nucleon and its lowest-lying Delta(1232) excitation within a constituent quark model for those two baryons based on the covariant spectator theory. Once the reactions gamma N \\to N and gamma N \\to Delta were described, we predicted without further adjusting of parameters the four electromagnetic Delta form factors: the electric charge G_{E0}, the magnetic dpole G_{M1}, the electric quadrupole G_{E2} and the magnetic octupole G_{M3}. The results are compatible with the available experimental data and recent lattice QCD data.
On analyzing ordinal data when responses and covariates are both missing at random.
Rana, Subrata; Roy, Surupa; Das, Kalyan
2016-08-01
In many occasions, particularly in biomedical studies, data are unavailable for some responses and covariates. This leads to biased inference in the analysis when a substantial proportion of responses or a covariate or both are missing. Except a few situations, methods for missing data have earlier been considered either for missing response or for missing covariates, but comparatively little attention has been directed to account for both missing responses and missing covariates, which is partly attributable to complexity in modeling and computation. This seems to be important as the precise impact of substantial missing data depends on the association between two missing data processes as well. The real difficulty arises when the responses are ordinal by nature. We develop a joint model to take into account simultaneously the association between the ordinal response variable and covariates and also that between the missing data indicators. Such a complex model has been analyzed here by using the Markov chain Monte Carlo approach and also by the Monte Carlo relative likelihood approach. Their performance on estimating the model parameters in finite samples have been looked into. We illustrate the application of these two methods using data from an orthodontic study. Analysis of such data provides some interesting information on human habit.
Perceived freedom-responsibility covariation among Cypriot adolescents.
Frangou, Georgia; Wilkerson, Keith; McGahan, Joseph R
2008-04-01
Participants were 67 Cypriot adolescents who responded to propositions regarding positive, negative, and noncontingent relations between freedom and responsibility. The authors framed items so that half dealt with freedom given responsibility, and the other half dealt with responsibility given freedom. Results indicated participants were more likely to endorse positive-contingency items than they were negative and noncontingency items when items were framed around freedom given responsibility. However, when items were framed around responsibility given freedom, no such differences emerged. The authors discuss results relative to cultural and sociopolitical differences and similarities between children in Cypress and participants in the United States and implications concerning the present study and previous studies regarding these constructs.
Analysis Of Covariance Structure Tests Of A Criterial Referents Theory Of Attitudes.
Kerlinger, F N
1980-10-01
To test a criterial referents theory of social attitudes, data obtained in the 1960's and 1970's from factor analyses of social attitudes scales administered to students in the U. S. and Europe and to a random sample of Dutch citizens were reanalyzed using an analysis of covariance structure approach. The two-factor model of the basic hypothesis of the theory -- two relatively orthogonal second-order factors, liberalism (L) and conservatism (C), underlie social attitudes -- was tested against the one-factor model of the assumption of attitude bipolarity -- attitudes have positive and negative poles (L versus C). Although the results of the separate tests of the fit of the two models were mixed, contrast tests of the two models favored the two-factor (dualistic) hypothesis.
Frame-Covariant Formulation of Inflation in Scalar-Curvature Theories
Burns, Daniel; Pilaftsis, Apostolos
2016-01-01
We develop a frame-covariant formulation of inflation in the slow-roll approximation by generalizing the inflationary attractor solution for scalar-curvature theories. Our formulation gives rise to new generalized forms for the potential slow-roll parameters, which enable us to examine the effect of conformal transformations and inflaton reparameterizations in scalar-curvature theories. We find that cosmological observables, such as the power spectrum, the spectral indices and their runnings, can be expressed in a concise manner in terms of the generalized potential slow-roll parameters which depend on the scalar-curvature coupling function, the inflaton wavefunction, and the inflaton potential. We show how the cosmological observables of inflation are frame-invariant in this generalized potential slow-roll formalism, as long as the end-of-inflation condition is appropriately extended to become frame-invariant as well. We then apply our formalism to specific scenarios, such as the induced gravity inflation, H...
Lee, Wonyul; Liu, Yufeng
2012-10-01
Multivariate regression is a common statistical tool for practical problems. Many multivariate regression techniques are designed for univariate response cases. For problems with multiple response variables available, one common approach is to apply the univariate response regression technique separately on each response variable. Although it is simple and popular, the univariate response approach ignores the joint information among response variables. In this paper, we propose three new methods for utilizing joint information among response variables. All methods are in a penalized likelihood framework with weighted L(1) regularization. The proposed methods provide sparse estimators of conditional inverse co-variance matrix of response vector given explanatory variables as well as sparse estimators of regression parameters. Our first approach is to estimate the regression coefficients with plug-in estimated inverse covariance matrices, and our second approach is to estimate the inverse covariance matrix with plug-in estimated regression parameters. Our third approach is to estimate both simultaneously. Asymptotic properties of these methods are explored. Our numerical examples demonstrate that the proposed methods perform competitively in terms of prediction, variable selection, as well as inverse covariance matrix estimation.
Evolutionary response when selection and genetic variation covary across environments.
Wood, Corlett W; Brodie, Edmund D
2016-10-01
Although models of evolution usually assume that the strength of selection on a trait and the expression of genetic variation in that trait are independent, whenever the same ecological factor impacts both parameters, a correlation between the two may arise that accelerates trait evolution in some environments and slows it in others. Here, we address the evolutionary consequences and ecological causes of a correlation between selection and expressed genetic variation. Using a simple analytical model, we show that the correlation has a modest effect on the mean evolutionary response and a large effect on its variance, increasing among-population or among-generation variation in the response when positive, and diminishing variation when negative. We performed a literature review to identify the ecological factors that influence selection and expressed genetic variation across traits. We found that some factors - temperature and competition - are unlikely to generate the correlation because they affected one parameter more than the other, and identified others - most notably, environmental novelty - that merit further investigation because little is known about their impact on one of the two parameters. We argue that the correlation between selection and genetic variation deserves attention alongside other factors that promote or constrain evolution in heterogeneous landscapes.
Localized form of Fock terms in nuclear covariant density functional theory
Liang, Haozhao; Ring, Peter; Roca-Maza, Xavier; Meng, Jie
2012-01-01
In most of the successful versions of covariant density functional theory in nuclei, the Fock terms are not included explicitly, which leads to local functionals and forms the basis of their widespread applicability at present. However, it has serious consequences for the description of Gamow-Teller resonances (GTR) and spin-dipole resonances (SDR) which can only be cured by adding further phenomenological parameters. Relativistic Hartree-Fock models do not suffer from these problems. They can successfully describe the GTR and SDR as well as the isovector part of the Dirac effective mass without any additional parameters. However, they are non-local and require considerable numerical efforts. By the zero-range reduction and the Fierz transformation, a new method is proposed to take into account the Fock terms in local functionals, which retains the simplicity of conventional models and provides proper descriptions of the spin-isospin channels and the Dirac masses.
Pinto, Sérgio Alexandre; Gross, Franz
2009-01-01
We present the first calculations of the electromagnetic form factors of $^3$He and $^3$H within the framework of the Covariant Spectator Theory (CST). This first exploratory study concentrates on the sensitivity of the form factors to the strength of the scalar meson-nucleon off-shell coupling, known from previous studies to have a strong influence on the three-body binding energy. Results presented here were obtained using the complete impulse approximation (CIA), which includes contributions of relativistic origin that appear as two-body corrections in a non-relativistic framework, such as "Z-graphs", but omits other two and three-body currents. We compare our results to non-relativistic calculations augmented by relativistic corrections of ${\\cal O}(v/c)^2$.
Suleymanov, Michael; Horwitz, Lawrence; Yahalom, Asher
2017-06-01
A relativistic 4D string is described in the framework of the covariant quantum theory first introduced by Stueckelberg [ Helv. Phys. Acta 14, 588 (1941)], and further developed by Horwitz and Piron [ Helv. Phys. Acta 46, 316 (1973)], and discussed at length in the book of Horwitz [Relativistic Quantum Mechanics, Springer (2015)]. We describe the space-time string using the solutions of relativistic harmonic oscillator [ J. Math. Phys. 30, 66 (1989)]. We first study the problem of the discrete string, both classically and quantum mechanically, and then turn to a study of the continuum limit, which contains a basically new formalism for the quantization of an extended system. The mass and energy spectrum are derived. Some comparison is made with known string models.
Time-odd mean fields in covariant density functional theory: Rotating systems
Afanasjev, A V; 10.1103/PhysRev.82.034329
2010-01-01
Time-odd mean fields (nuclear magnetism) and their impact on physical observables in rotating nuclei are studied in the framework of covariant density functional theory (CDFT). It is shown that they have profound effect on the dynamic and kinematic moments of inertia. Particle number, configuration and rotational frequency dependences of their impact on the moments of inertia have been analysed in a systematic way. Nuclear magnetism can also considerably modify the band crossing features such as crossing frequencies and the properties of the kinematic and dynamic moments of inertia in the band crossing region. The impact of time-odd mean fields on the moments of inertia in the regions away from band crossing only weakly depends on the relativistic mean field parametrization, reflecting good localization of the properties of time-odd mean fields in CDFT. The moments of inertia of normal-deformed nuclei considerably deviate from the rigid body value. On the contrary, superdeformed and hyperdeformed nuclei have ...
Finite temperature and the Polyakov loop in the covariant variational approach to Yang-Mills Theory
Quandt, Markus; Reinhardt, Hugo
2017-03-01
We extend the covariant variational approach for Yang-Mills theory in Landau gauge to non-zero temperatures. Numerical solutions for the thermal propagators are presented and compared to high-precision lattice data. To study the deconfinement phase transition, we adapt the formalism to background gauge and compute the effective action of the Polyakov loop for the colour groups SU(2) and SU(3). Using the zero-temperature propagators as input, all parameters are fixed at T = 0 and we find a clear signal for a deconfinement phase transition at finite temperatures, which is second order for SU(2) and first order for SU(3). The critical temperatures obtained are in reasonable agreement with lattice data.
Covariant variational approach to Yang-Mills theory: Effective potential of the Polyakov loop
Quandt, M.; Reinhardt, H.
2016-09-01
We compute the effective action of the Polyakov loop in S U (2 ) and S U (3 ) Yang-Mills theory using a previously developed covariant variational approach. The formalism is extended to background gauge and it is shown how to relate the low-order Green's functions to the ones in Landau gauge studied earlier. The renormalization procedure is discussed. The self-consistent effective action is derived and evaluated using the numerical solution of the gap equation. We find a clear signal for a deconfinement phase transition at finite temperatures, which is second order for S U (2 ) and first order for S U (3 ). The critical temperatures obtained are in reasonable agreement with high-precision lattice data.
Covariant variational approach to Yang-Mills Theory: effective potential of the Polyakov loop
Quandt, Markus
2016-01-01
We compute the effective action of the Polyakov loop in SU(2) and SU(3) Yang-Mills theory using a previously developed covariant variational approach. The formalism is extended to background gauge and it is shown how to relate the low order Green's functions to the ones in Landau gauge studied earlier. The renormalization procedure is discussed. The self-consistent effective action is derived and evaluated using the numerical solution of the gap equation. We find a clear signal for a deconfinement phase transition at finite temperatures, which is second order for SU(2) and first order for SU(3). The critical temperatures obtained are in reasonable agreement with high precision lattice data.
Chiral symmetry and pi-pi scattering in the Covariant Spectator Theory
Biernat, Elmar P; Ribeiro, J E; Stadler, Alfred; Gross, Franz
2014-01-01
The pi-pi scattering amplitude calculated with a model for the quark-antiquark interaction in the framework of the Covariant Spectator Theory (CST) is shown to satisfy the Adler zero constraint imposed by chiral symmetry. The CST formalism is established in Minkowski space and our calculations are performed in momentum space. We prove that the axial-vector Ward-Takahashi identity is satisfied by our model. Then we show that, similarly to what happens within the Bethe-Salpeter formalism, application of the axial-vector Ward-Takahashi identity to the CST pi-pi scattering amplitude allows us to sum the intermediate quark-quark interactions to all orders. The Adler self-consistency zero for pi-pi scattering in the chiral limit emerges as the result for this sum.
Zhou, Shan-Gui
2016-01-01
The intrinsic nuclear shapes deviating from a sphere not only manifest themselves in nuclear collective states but also play important roles in determining nuclear potential energy surfaces (PES's) and fission barriers. In order to describe microscopically and self-consistently nuclear shapes and PES's with as many shape degrees of freedom as possible included, we developed multidimensionally-constrained covariant density functional theories (MDC-CDFTs). In MDC-CDFTs, the axial symmetry and the reflection symmetry are both broken and all deformations characterized by $\\beta_{\\lambda\\mu}$ with even $\\mu$ are considered. We have used the MDC-CDFTs to study PES's and fission barriers of actinides, the non-axial octupole $Y_{32}$ correlations in $N = 150$ isotones and shapes of hypernuclei. In this Review we will give briefly the formalism of MDC-CDFTs and present the applications to normal nuclei.
Energy Technology Data Exchange (ETDEWEB)
Pinto, Sérgio Alexandre; Stadler, Alfred; Gross, Franz
2009-05-01
We present the first calculations of the electromagnetic form factors of ^{3}He and ^{3}H within the framework of the Covariant Spectator Theory (CST). This first exploratory study concentrates on the sensitivity of the form factors to the strength of the scalar meson-nucleon off-shell coupling, known from previous studies to have a strong influence on the three-body binding energy. Results presented here were obtained using the complete impulse approximation (CIA), which includes contributions of relativistic origin that appear as two-body corrections in a non-relativistic framework, such as "Z-graphs," but omits other two and three-body currents. Finally, we compare our results to non-relativistic calculations augmented by relativistic corrections of O(v/c)^{2}.
Fewster, Christopher J
2015-08-06
The framework of locally covariant quantum field theory is discussed, motivated in part using 'ignorance principles'. It is shown how theories can be represented by suitable functors, so that physical equivalence of theories may be expressed via natural isomorphisms between the corresponding functors. The inhomogeneous scalar field is used to illustrate the ideas. It is argued that there are two reasonable definitions of the local physical content associated with a locally covariant theory; when these coincide, the theory is said to be dynamically local. The status of the dynamical locality condition is reviewed, as are its applications in relation to (i) the foundational question of what it means for a theory to represent the same physics in different space-times and (ii) a no-go result on the existence of natural states.
Directory of Open Access Journals (Sweden)
John M Murray
Full Text Available The poor response to the combined antiviral therapy of pegylated alfa-interferon and ribavarin for hepatitis C virus (HCV infection may be linked to mutations in the viral envelope gene E1E2 (env, which can result in escape from the immune response and higher efficacy of viral entry. Mutations that result in failure of therapy most likely require compensatory mutations to achieve sufficient change in envelope structure and function. Compensatory mutations were investigated by determining positions in the E1E2 gene where amino acids (aa covaried across groups of individuals. We assessed networks of covarying positions in E1E2 sequences that differentiated sustained virological response (SVR from non-response (NR in 43 genotype 1a (17 SVR, and 49 genotype 1b (25 SVR chronically HCV-infected individuals. Binary integer programming over covariance networks was used to extract aa combinations that differed between response groups. Genotype 1a E1E2 sequences exhibited higher degrees of covariance and clustered into 3 main groups while 1b sequences exhibited no clustering. Between 5 and 9 aa pairs were required to separate SVR from NR in each genotype. aa in hypervariable region 1 were 6 times more likely than chance to occur in the optimal networks. The pair 531-626 (EI appeared frequently in the optimal networks and was present in 6 of 9 NR in one of the 1a clusters. The most frequent pairs representing SVR were 431-481 (EE, 500-522 (QA in 1a, and 407-434 (AQ in 1b. Optimal networks based on covarying aa pairs in HCV envelope can indicate features that are associated with failure or success to antiviral therapy.
A preliminary evaluation of an O2/CO2 based eddy covariance theory at Missouri AmeriFlux site
Yan, B.; Gu, L.
2013-12-01
The eddy covariance (EC) technique has been widely used at flux sites on every continent, across most ecosystem types and climates to monitor exchanges of momentum, mass and energy between land surface and atmosphere. In an attempt to develop a self-consistent theory for the EC technique, Gu et al. (2012) reformulated the fundamental equations for EC by introducing the concept of constraining gas that has no net ecosystem sink/source. Gu (2013) expanded the theory of Gu et al. (2012) to include paired gases whose ecosystem exchange ratios are stable over an averaging period (e.g. 30 min) and therefore can be used to constrain EC flux measurements of any gases. He proposed that O2 and CO2 are an ideal pair of gases as their biological processes are coupled and their ecosystem exchange ratio (also known as oxidative ratio) is close to 1. Advantages of this new O2/CO2 based EC theory include: 1) avoidance of covariance loss in calculating dry air density induced by spatial separation of measuring instruments and use of multiple indirectly derived variables, 2) the minimum number of assumptions adopted for the derivation of the equation, and 3) avoidance of errors related to linearization of ideal gas law. In this study, we conducted a preliminary evaluation for the basic principle of Gu (2013) EC theory. We crosschecked net ecosystem exchange (NEE) estimations from different, independent methods by using CO2 and H2O as paired constraining gases. Using CO2 and H2O instead of CO2 and O2 as paired constraining gases is not ideal in the framework of Gu (2013); however, no fast response O2 analyzer is currently available. CO2 and H2O are both transported between the inside of plants and canopy air through stomata on leaves in the processes of photosynthesis and transpiration which are known to be closely coupled. However, this close coupling is contaminated by other ecosystem sinks/sources, e.g. respiration of plants and soil for CO2 and evaporation of intercepted and soil
Avramidi, I G
1994-01-01
We continue the development of the effective covariant methods for calculating the heat kernel and the one-loop effective action in quantum field theory and quantum gravity. The status of the low-energy approximation in quantum gauge theories and quantum gravity is discussed in detail on the basis of analyzing the local Schwinger - De Witt expansion. It is argued that the low-energy limit, when defined in a covariant way, should be related to background fields with covariantly constant curvature, gauge field strength and potential. Some new approaches for calculating the low-energy heat kernel assuming a covariantly constant background are proposed. The one-loop low-energy effective action in Yang-Mills theory in flat space with arbitrary compact simple gauge group and arbitrary matter on a covariantly constant background is calculated. The stability problem of the chromomagnetic (Savvidy-type) vacuum is analyzed. It is shown, that this type of vacuum structure can be stable only in the case when more than on...
Geng, L S; Vacas, M J Vicente
2009-01-01
We present a calculation of the leading SU(3)-breaking $\\mathcal{O}(p^3)$-corrections to the electromagnetic moments and charge radius (CR) of the lowest-lying decuplet resonances in covariant chiral perturbation theory. In particular, the magnetic dipole moment (MDM) of the members of the decuplet is predicted fixing the only low-energy constant (LEC) present up to this order with the well measured MDM of the $\\Omega^-$. We predict $\\mu_\\Delta^{++}=6.04(13)$ and $\\mu_\\Delta^+=2.84(2)$ which agree well with the current experimental information. For the electric quadrupole moment (EQM) and the CR we use state-of-the-art lattice QCD results to determine the corresponding LECs, whereas for the magnetic octupole moment (MOM) there is no unknown LEC up to the order considered here and we obtain a pure prediction. We compare our results with those reported in large $N_c$, lattice QCD, heavy-baryon chiral perturbation theory and other models.
Consistency between SU(3) and SU(2) covariant baryon chiral perturbation theory for the nucleon mass
Ren, Xiu-Lei; Alvarez-Ruso, L.; Geng, Li-Sheng; Ledwig, Tim; Meng, Jie; Vicente Vacas, M. J.
2017-03-01
Treating the strange quark mass as a heavy scale compared to the light quark mass, we perform a matching of the nucleon mass in the SU(3) sector to the two-flavor case in covariant baryon chiral perturbation theory. The validity of the 19 low-energy constants appearing in the octet baryon masses up to next-to-next-to-next-to-leading order [1] is supported by comparing the effective parameters (the combinations of the 19 couplings) with the corresponding low-energy constants in the SU(2) sector [2]. In addition, it is shown that the dependence of the effective parameters and the pion-nucleon sigma term on the strange quark mass is relatively weak around its physical value, thus providing support to the assumption made in Ref. [2] that the SU(2) baryon chiral perturbation theory can be applied to study nf = 2 + 1 lattice QCD simulations as long as the strange quark mass is close to its physical value.
A covariate adjusted two-stage allocation design for binary responses in randomized clinical trials.
Bandyopadhyay, Uttam; Biswas, Atanu; Bhattacharya, Rahul
2007-10-30
In the present work, we develop a two-stage allocation rule for binary response using the log-odds ratio within the Bayesian framework allowing the current allocation to depend on the covariate value of the current subject. We study, both numerically and theoretically, several exact and limiting properties of this design. The applicability of the proposed methodology is illustrated by using some data set. We compare this rule with some of the existing rules by computing various performance measures.
Gravitational Energy for GR and Poincare Gauge Theories: a Covariant Hamiltonian Approach
Chen, Chiang-Mei; Tung, Roh-Suan
2015-01-01
Our topic concerns a long standing puzzle: the energy of gravitating systems. More precisely we want to consider, for gravitating systems, how to best describe energy-momentum and angular momentum/center-of-mass momentum (CoMM). It is known that these quantities cannot be given by a local density. The modern understanding is that (i) they are quasi-local (associated with a closed 2-surface), (ii) they have no unique formula, (iii) they have no reference frame independent description. In the first part of this work we review some early history, much of it not so well known, on the subject of gravitational energy in Einstein's general relativity (GR), noting especially Noether's contribution. In the second part we review (including some new results) much of our covariant Hamiltonian formalism and apply it to Poincar\\'e gauge theories (GR is a special case). The key point is that the Hamiltonian boundary term has two roles, it determines the quasi-local quantities, and, furthermore it determines the boundary con...
Wiesendanger, C
2011-01-01
Viewing gravitational energy-momentum $p_G^\\mu$ as equal by observation, but different in essence from inertial energy-momentum $p_I^\\mu$ naturally leads to the gauge theory of volume-preserving diffeormorphisms of an inner Minkowski space ${\\bf M}^{\\sl 4}$. To extract its physical content the full gauge group is reduced to its Poincar\\'e subgroup. The respective Poincar\\'e gauge fields, field strengths and Poincar\\'e-covariant field equations are obtained and point-particle source currents are derived. The resulting set of non-linear field equations coupled to point matter is solved in first order resulting in Lienard-Wiechert-like potentials for the Poincar\\'e fields. After numerical identification of gravitational and inertial energy-momentum Newton's inverse square law for gravity in the static non-relativistic limit is recovered. The Weak Equivalence Principle in this approximation is proven to be valid and spacetime geometry in the presence of Poincar\\'e fields is shown to be curved. Finally, the gravit...
Covariant and locally Lorentz-invariant varying speed of light theories
Magueijo, J
2000-01-01
We propose definitions for covariance and local Lorentz invariance applicable when the speed of light $c$ is allowed to vary. They have the merit of retaining only those aspects of the usual definitions which are invariant under unit transformations, and which can therefore legitimately represent the outcome of an experiment. We then discuss some possibilities for invariant actions governing the dynamics of such theories. We consider first the classical action for matter fields and the effects of a changing $c$ upon quantization. We discover a peculiar form of quantum particle creation due to a varying $c$. We then study actions governing the dynamics of gravitation and the speed of light. We find the free, empty-space, no-gravity solution, to be interpreted as the counterpart of Minkowksi space-time, and highlight its similarities with Fock-Lorentz space-time. We also find flat-space string-type solutions, in which near the string core $c$ is much higher. We label them fast-tracks and compare them with gravi...
Shape evolutions of $^{72,74}$Kr with temperature in the covariant density functional theory
Zhang, Wei
2016-01-01
The rich phenomena of deformations in neutron-deficient krypton isotopes such as the shape evolution with neutron number and the shape coexistence attract the interests of nuclear physicists for decades. It will be interesting to study such shape phenomena using a novel way, i.e., by thermally exciting the nucleus. So in this work, we study the shape evolutions in $^{72,74}$Kr with increasing temperatures within the covariant density functional theory with parameter set PC-PK1. While $^{72}$Kr displays simple oblate to spherical transition at $T$=3.35 MeV, $^{74}$Kr displays three shape transitions, namely, 0.6 MeV from oblate to prolate, 1.65 MeV from prolate to oblate, and 2.95 MeV from oblate to spherical. Together with the shape transitions, two shape coexistence ranges are obtained for $^{74}$Kr, namely, from 0 MeV to 0.75 MeV, and from 1.45 to 1.8 MeV. Such shape transitions can be understood by disintegrating the total energy into particle energy and field energy.
Shape evolution of 72,74Kr with temperature in covariant density functional theory
Zhang, Wei; Niu, Yi-Fei
2017-09-01
The rich phenomena of deformations in neutron-deficient krypton isotopes, such as shape evolution with neutron number and shape coexistence, have attracted the interest of nuclear physicists for decades. It is interesting to study such shape phenomena using a novel way, e.g. by thermally exciting the nucleus. In this work, we develop the finite temperature covariant density functional theory for axially deformed nuclei with the treatment of pairing correlations by the BCS approach, and apply this approach for the study of shape evolution in 72,74Kr with increasing temperature. For 72Kr, with temperature increasing, the nucleus firstly experiences a relatively quick weakening in oblate deformation at temperature T ∼0.9 MeV, and then changes from oblate to spherical at T ∼2.1 MeV. For 74Kr, its global minimum is at quadrupole deformation β2 ∼ ‑0.14 and abruptly changes to spherical at T∼ 1.7 MeV. The proton pairing transition occurs at critical temperature 0.6 MeV following the rule Tc=0.6Δp(0), where Δp(0) is the proton pairing gap at zero temperature. The signatures of the above pairing transition and shape changes can be found in the specific heat curve. The single-particle level evolutions with temperature are presented. Supported by National Natural Science Foundation of China (11105042, 11305161, 11505157), Open Fund of Key Laboratory of Time and Frequency Primary Standards, CAS, and Support from Henan Administration of Foreign Experts Affairs
Unphysical divergences in response theory
Parker, Shane M.; Roy, Saswata; Furche, Filipp
2016-10-01
Transition densities between excited states are key for nonlinear theoretical spectroscopy and multi-state non-adiabatic molecular dynamics (NAMD) simulations. In the framework of response theory, these transition densities are accessible from poles of the quadratic response function. It was shown recently that the thus obtained transition densities within time-dependent Hartree-Fock (TDHF) and adiabatic time-dependent density functional theory (TDDFT) exhibit unphysical divergences when the difference in excitation energy of the two states of interest matches another excitation energy. This unphysical behavior is a consequence of spurious poles in the quadratic response function. We show that the incorrect pole structure of the quadratic response is not limited to TDHF and adiabatic TDDFT, but is also present in many other approximate many-electron response functions, including those from coupled cluster and multiconfigurational self-consistent field response theory. The divergences appear in regions of the potential energy surface where the ground state is perfectly well behaved, and they are frequently encountered in NAMD simulations of photochemical reactions. The origin of the divergences is traced to an incorrect instantaneous time-dependence of the effective Hamiltonian. The implications for computations of frequency-dependent response properties are considerable and call into question the validity of conventional approximate many-electron response theories beyond linear response.
Bernard, V; Meißner, Ulf G; Kubis, Bastian; Mei{\\ss}ner, Ulf-G.
2005-01-01
We analyze the Fubini-Furlan-Rosetti sum rule in the framework of covariant baryon chiral perturbation theory to leading one-loop accuracy and including next-to-leading order polynomial contributions. We discuss the relation between the subtraction constants in the invariant amplitudes and certain low-energy constants employed in earlier chiral perturbation theory studies of threshold neutral pion photoproduction off nucleons. In particular, we consider the corrections to the sum rule due to the finite pion mass and show that below the threshold they agree well with determinations based on fixed-t dispersion relations. We also discuss the energy dependence of the electric dipole amplitude E_{0+}.
Dowling, D K; Maklakov, A A; Friberg, U; Hailer, F
2009-04-01
Two genetic models exist to explain the evolution of ageing - mutation accumulation (MA) and antagonistic pleiotropy (AP). Under MA, a reduced intensity of selection with age results in accumulation of late-acting deleterious mutations. Under AP, late-acting deleterious mutations accumulate because they confer beneficial effects early in life. Recent studies suggest that the mitochondrial genome is a major player in ageing. It therefore seems plausible that the MA and AP models will be relevant to genomes within the cytoplasm. This possibility has not been considered previously. We explore whether patterns of covariation between fitness and ageing across 25 cytoplasmic lines, sampled from a population of Drosophila melanogaster, are consistent with the genetic associations predicted under MA or AP. We find negative covariation for fitness and the rate of ageing, and positive covariation for fitness and lifespan. Notably, the direction of these associations is opposite to that typically predicted under AP.
Contextualized Network Analysis: Theory and Methods for Networks with Node Covariates
Binkiewicz, Norbert M.
Biological and social systems consist of myriad interacting units. The interactions can be intuitively represented in the form of a graph or network. Measurements of these graphs can reveal the underlying structure of these interactions, which provides insight into the systems that generated the graphs. Moreover, in applications such as neuroconnectomics, social networks, and genomics, graph data is accompanied by contextualizing measures on each node. We leverage these node covariates to help uncover latent communities, using a modification of spectral clustering. Statistical guarantees are provided under a joint mixture model called the node contextualized stochastic blockmodel, including a bound on the mis-clustering rate. For most simulated conditions, covariate assisted spectral clustering yields superior results relative to both regularized spectral clustering without node covariates and an adaptation of canonical correlation analysis. We apply covariate assisted spectral clustering to large brain graphs derived from diffusion MRI, using the node locations or neurological regions as covariates. In both cases, covariate assisted spectral clustering yields clusters that are easier to interpret neurologically. A low rank update algorithm is developed to reduce the computational cost of determining the tuning parameter for covariate assisted spectral clustering. As simulations demonstrate, the low rank update algorithm increases the speed of covariate assisted spectral clustering up to ten-fold, while practically matching the clustering performance of the standard algorithm. Graphs with node attributes are sometimes accompanied by ground truth labels that align closely with the latent communities in the graph. We consider the example of a mouse retina neuron network accompanied by the neuron spatial location and neuronal cell types. In this example, the neuronal cell type is considered a ground truth label. Current approaches for defining neuronal cell type vary
DeBenedictis, Andrew
2016-01-01
Recently, a fully covariant version of the theory of $F(T)$ torsion gravity has been introduced (arXiv:1510.08432v2 [gr-qc]). In covariant $F(T)$ gravity the Schwarzschild solution is not a vacuum solution for $F(T)\
Directory of Open Access Journals (Sweden)
L.S. Ferreira
2016-02-01
Full Text Available Proton radioactivity from deformed nuclei is described for the first time by a self-consistent calculation based on covariant relativistic density functionals derived from meson exchange and point coupling models. The calculation provides an important new test to these interactions at the limits of stability, since the mixing of different angular momenta in the single particle wave functions is probed.
Asymptotic theory for the sample covariance matrix of a heavy-tailed multivariate time series
DEFF Research Database (Denmark)
Davis, Richard A.; Mikosch, Thomas Valentin; Pfaffel, Olivier
2016-01-01
particular, the time series has infinite fourth moment. We derive the limiting behavior for the largest eigenvalues of the sample covariance matrix and show point process convergence of the normalized eigenvalues. The limiting process has an explicit form involving points of a Poisson process and eigenvalues...
Energy Technology Data Exchange (ETDEWEB)
Ferreira, L.S., E-mail: flidia@tecnico.ulisboa.pt [Center of Physics and Engineering of Advanced Materials, CeFEMA, and Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, P1049-001 Lisbon (Portugal); Maglione, E. [Dipartimento di Fisica e Astronomia “G. Galilei”, Via Marzolo 8, I-35131 Padova (Italy); Istituto Nazionale di Fisica Nucleare, Padova (Italy); Ring, P. [Physik Department der Technischen Universität München, D-85748 Garching (Germany)
2016-02-10
Proton radioactivity from deformed nuclei is described for the first time by a self-consistent calculation based on covariant relativistic density functionals derived from meson exchange and point coupling models. The calculation provides an important new test to these interactions at the limits of stability, since the mixing of different angular momenta in the single particle wave functions is probed.
Geng, L S; Vacas, M J Vicente
2009-01-01
We report on a recent study of the SU(3)-breaking corrections to the hyperon vector coupling $f_1(0)$ up to $\\mathcal{O}(p^4)$ in covariant baryon chiral perturbation theory with dynamical octet and decuplet contributions. The decuplet contributions are taken into account for the first time in a covariant ChPT study and are found of similar or even larger size than the octet ones. We predict positive SU(3)-breaking corrections to all the four independent $f_1(0)$'s (assuming isospin symmetry), which are consistent, within uncertainties, with the latest results from large $N_c$ fits, chiral quark models, and quenched lattice QCD calculations. We also discuss briefly the implications of our results for the extraction of $V_{us}$ from hyperon decay data.
Diffusion theory of slow responses
Institute of Scientific and Technical Information of China (English)
李景德; 陈敏; 郑凤; 周镇宏
1997-01-01
When an action is applied to a macroscopic substance, there is a particular sort of slow response he sides the well-known fast response. Using diffusion theory, the characteristics of slow response in dielectric, elastic, piezoelectric, and pyroelectric relaxation may he explained A time domain spectroscopy method suitable for slow and fast responses in linear and nonlinear effects is given. Every relaxation mechanism contributes a peak in differential spectroscopy, and its position, height, and line shape show the dynamical properties of the mechanism The method of frequency domain spectroscopy is suitable only for linear fast response. Time domain spectroscopy is another nonequiv-alent powerful method. The theory is confirmed by a lot of experimental data
Bibinger, Markus
2011-01-01
The article is devoted to the nonparametric estimation of the quadratic covariation of non-synchronously observed It\\^o processes in an additive microstructure noise model. In a high-frequency setting, we aim at establishing an asymptotic distribution theory for a generalized multiscale estimator including a feasible central limit theorem with optimal convergence rate on convenient regularity assumptions. The inevitably remaining impact of asynchronous deterministic sampling schemes and noise corruption on the asymptotic distribution is precisely elucidated. A case study for various important examples, several generalizations of the model and an algorithm for the implementation warrant the utility of the estimation method in applications.
Geng, L S; Vacas, M J Vicente
2009-01-01
We calculate the SU(3)-breaking corrections to the hyperon vector coupling $f_1(0)$ up to $\\mathcal{O}(p^4)$ in covariant baryon chiral perturbation theory with dynamical octet and decuplet contributions. We find that the decuplet contributions are of similar or even larger size than the octet ones. Combining both, we predict positive SU(3)-breaking corrections to all the four independent $f_1(0)$'s (assuming isospin symmetry), which are consistent, within uncertainties, with the latest results form large $N_c$ fits, chiral quark models, and quenched lattice QCD calculations.
Lorentz covariant reduced-density-operator theory for relativistic quantum information processing
Ahn, D; Hwang, S W; Ahn, Doyeol; Lee, Hyuk-jae; Hwang, Sung Woo
2003-01-01
In this paper, we derived Lorentz covariant quantum Liouville equation for the density operator which describes the relativistic quantum information processing from Tomonaga-Schwinger equation and an exact formal solution for the reduced-density-operator is obtained using the projector operator technique and the functional calculus. When all the members of the family of the hypersurfaces become flat hyperplanes, it is shown that our results agree with those of non-relativistic case which is valid only in some specified reference frame. The formulation presented in this work is general and might be applied to related fields such as quantum electrodynamics and relativistic statistical mechanics.
Energy Technology Data Exchange (ETDEWEB)
Studnicki, M.; Mądry, W.; Noras, K.; Wójcik-Gront, E.; Gacek, E.
2016-11-01
The main objectives of multi-environmental trials (METs) are to assess cultivar adaptation patterns under different environmental conditions and to investigate genotype by environment (G×E) interactions. Linear mixed models (LMMs) with more complex variance-covariance structures have become recognized and widely used for analyzing METs data. Best practice in METs analysis is to carry out a comparison of competing models with different variance-covariance structures. Improperly chosen variance-covariance structures may lead to biased estimation of means resulting in incorrect conclusions. In this work we focused on adaptive response of cultivars on the environments modeled by the LMMs with different variance-covariance structures. We identified possible limitations of inference when using an inadequate variance-covariance structure. In the presented study we used the dataset on grain yield for 63 winter wheat cultivars, evaluated across 18 locations, during three growing seasons (2008/2009-2010/2011) from the Polish Post-registration Variety Testing System. For the evaluation of variance-covariance structures and the description of cultivars adaptation to environments, we calculated adjusted means for the combination of cultivar and location in models with different variance-covariance structures. We concluded that in order to fully describe cultivars adaptive patterns modelers should use the unrestricted variance-covariance structure. The restricted compound symmetry structure may interfere with proper interpretation of cultivars adaptive patterns. We found, that the factor-analytic structure is also a good tool to describe cultivars reaction on environments, and it can be successfully used in METs data after determining the optimal component number for each dataset. (Author)
Directory of Open Access Journals (Sweden)
Marcin Studnicki
2016-06-01
Full Text Available The main objectives of multi-environmental trials (METs are to assess cultivar adaptation patterns under different environmental conditions and to investigate genotype by environment (G×E interactions. Linear mixed models (LMMs with more complex variance-covariance structures have become recognized and widely used for analyzing METs data. Best practice in METs analysis is to carry out a comparison of competing models with different variance-covariance structures. Improperly chosen variance-covariance structures may lead to biased estimation of means resulting in incorrect conclusions. In this work we focused on adaptive response of cultivars on the environments modeled by the LMMs with different variance-covariance structures. We identified possible limitations of inference when using an inadequate variance-covariance structure. In the presented study we used the dataset on grain yield for 63 winter wheat cultivars, evaluated across 18 locations, during three growing seasons (2008/2009-2010/2011 from the Polish Post-registration Variety Testing System. For the evaluation of variance-covariance structures and the description of cultivars adaptation to environments, we calculated adjusted means for the combination of cultivar and location in models with different variance-covariance structures. We concluded that in order to fully describe cultivars adaptive patterns modelers should use the unrestricted variance-covariance structure. The restricted compound symmetry structure may interfere with proper interpretation of cultivars adaptive patterns. We found, that the factor-analytic structure is also a good tool to describe cultivars reaction on environments, and it can be successfully used in METs data after determining the optimal component number for each dataset.
Wolters, Sander A M
2010-01-01
The aim of this paper is to compare the two topos-theoretic approaches to quantum mechanics that may be found in the literature to date. The first approach, which we will call the contravariant approach, was proposed by Isham and Butterfield, and was later extended by Doering and Isham. The second approach, which we will call the covariant approach, was developed by Heunen, Landsman and Spitters. Motivated by coarse-graining and the Kochen-Specker theorem, the contravariant approach uses the topos of presheaves on a specific context category, defined as the poset of commutative von Neumann subalgebras of some given von Neumann algebra. The intuitionistic logic of this approach is presented by the (complete) Heyting algebra of closed open subobjects of the so-called spectral presheaf. We demonstrate that in a natural way, this Heyting algebra defines a locale, internal to the given presheaf topos. This locale is not regular, which is connected to undesirable properties of the Heyting negation. In the covariant...
Bertolini, Daniele; Solon, Mikhail P; Walsh, Jonathan R; Zurek, Kathryn M
2015-01-01
We compute the non-Gaussian contribution to the covariance of the matter power spectrum at one-loop order in Standard Perturbation Theory (SPT), and using the framework of the effective field theory (EFT) of large scale structure (LSS). The complete one-loop contributions are evaluated for the first time, including the leading EFT corrections that involve seven independent operators, of which four appear in the power spectrum and bispectrum. In the basis where the three new operators are maximally uncorrelated, we find that two of them are suppressed at the few percent level relative to other contributions, and may thus be neglected. We extract the single remaining coefficient from N-body simulations, and obtain robust predictions for the non-Gaussian part of the covariance $C(k_i, k_j)$ up to $k_i + k_j \\sim$ 0.3 h/Mpc. The one-parameter prediction from EFT improves over SPT, with the analytic reach in wavenumber more than doubled.
The renormalization of composite operators in Yang-Mills theories using general covariant gauge
Collins, J C; John C Collins; Randall J Scalise
1994-01-01
Essential to QCD applications of the operator product expansion, etc., is a knowledge of those operators that mix with gauge-invariant operators. A standard theorem asserts that the renormalization matrix is triangular: Gauge-invariant operators have "alien" gauge-variant operators among their counterterms, but, with a suitably chosen basis, the necessary alien operators have only themselves as counterterms. Moreover, the alien operators are supposed to vanish in physical matrix elements. A recent calculation by Hamberg and van Neerven apparently contradicts these results. By explicit calculations with the energy-momentum tensor, we show that the problems arise because of subtle infra-red singularities that appear when gluonic matrix elements are taken on-shell at zero momentum transfer. % Keywords: twist-two covariant gluon operator, mixing, non-abelian, anomalous dimension, Ward identity, BRST, LSZ reduction, Dixon, Taylor, Joglekar, Lee.
Scalar field theory on kappa-Minkowski spacetime and Lorentz covariance
Meljanac, Stjepan
2010-01-01
We investigate the properties of kappa-Minkowski spacetime by using representations of the corresponding deformed algebra in terms of undeformed Heisenberg-Weyl algebra. The deformed algebra consists of kappa-Poincare algebra extended with the generators of the deformed Weyl algebra. The part of deformed algebra, generated by rotation, boost and momentum generators, is described by the Hopf algebra structure. The approach used in our considerations is completely Lorentz covariant. We further use an adventages of this approach to consistently construct a star product which has a remarkable property that under integration sign it can be replaced by a standard pointwise multiplication, a property that was since known to hold for Moyal, but not also for kappa-Minkowski spacetime. This star product has also generalized trace and cyclic properties and the construction alone can be done in a simple and elegant way by considering a classical Dirac operator representation of the deformed algebra and by requiring it to...
Two-pion exchange and strong form-factors in covariant field theories
Ramalho, G; Peña, M T
1999-01-01
In this work improvements to the application of the Gross equation to nuclear systems are tested. In particular we evaluate the two pion exchange diagrams, including the crossed-box diagram, using models developed within the spectator-on-mass-shell covariant formalism. We found that the form factors used in these models induce spurious contributions that violate the unitary cut requirement. We tested then some alternative form-factors in order to preserve the unitarity condition. With this new choice, the difference between the exact and the spectator-on-mass-shell amplitudes is of the order of the one boson scalar exchange, supporting the idea that this difference may be parameterized by this type of terms.
Agbemava, S E; Ring, P
2016-01-01
A systematic investigation of octupole deformed nuclei is presented for even-even systems with $Z\\leq 106$ located between the two-proton and two-neutron drip lines. For this study we use five most up-to-date covariant energy density functionals of different types, with a non-linear meson coupling, with density dependent meson couplings, and with density-dependent zero-range interactions. Pairing correlations are treated within relativistic Hartree-Bogoliubov (RHB) theory based on an effective separable particle-particle interaction of finite range. This allows us to assess theoretical uncertainties within the present covariant models for the prediction of physical observables relevant for octupole deformed nuclei. In addition, a detailed comparison with the predictions of non-relativistic models is performed. A new region of octupole deformation, centered around $Z\\sim 98, N\\sim 196$ is predicted for the first time. In terms of its size in the $(Z,N)$ plane and the impact of octupole deformation on binding e...
Directory of Open Access Journals (Sweden)
J. B. A. Muller
2009-09-01
Full Text Available Eddy covariance ozone flux measurements are the most direct way to estimate ozone removal near the surface. Over vegetated surfaces, high quality ozone fluxes are required to probe the underlying processes for which it is necessary to separate the flux into the components of stomatal and non-stomatal deposition. Detailed knowledge of the processes that control non-stomatal deposition is limited and more accurate ozone flux measurements are needed to quantify this component of the deposited flux. We present a systematic intercomparison study of eddy covariance ozone flux measurements made using two fast response dry chemiluminescence analysers. Ozone deposition was measured over a well characterised managed grassland near Edinburgh, Scotland, during August 2007. A data quality control procedure specific to these analysers is introduced. Absolute ozone fluxes were calculated based on the relative signals of the dry chemiluminescence analysers using three different calibration methods and the results are compared for both analysers. It is shown that the error in the fitted parameters required for the flux calculations provides a substantial source of uncertainty in the fluxes. The choice of the calculation method itself can also constitute an uncertainty in the flux as the calculated fluxes by the three methods do not agree within error at all times. This finding highlights the need for a consistent and rigorous approach for comparable data-sets, such as e.g. in flux networks. Ozone fluxes calculated by one of the methods were then used to compare the two analysers in more detail. This systematic analyser comparison reveals half-hourly flux values differing by up to a factor of two at times with the difference in mean hourly flux ranging from 0 to 23% with an error in the mean daily flux of ±12%. The comparison of analysers shows that the agreement in fluxes is excellent for some days but that there is an underlying uncertainty as a result of
Biernat, Elmar P; Peña, M T; Stadler, Alfred
2015-01-01
The pion form factor is calculated in the framework of the charge-conjugation invariant Covariant Spectator Theory. This formalism is established in Minkowski space and the calculation is set up in momentum space. In a previous calculation we included only the leading pole coming from the spectator quark (referred to as the relativistic impulse approximation). In this paper we also include the contributions from the poles of the quark which interacts with the photon and average over all poles in both the upper and lower half planes in order to preserve charge conjugation invariance (referred to as the $C$-symmetric complete impulse approximation). We find that for small pion mass these contributions are significant at all values of the four-momentum transfer, $Q^2$, but, surprisingly, do not alter the shape obtained from the spectator poles alone.
Effective action of composite fields for general gauge theories in BLT-covariant formalism
Lavrov, P M; Reshetnyak, A A
1996-01-01
The gauge dependence of the effective action of composite fields for general gauge theories in the framework of the quantization method by Batalin, Lavrov and Tyutin is studied. The corresponding Ward identites are obtained. The variation of composite fields effective action is found in terms of new set of generators depending on composite field. The theorem of the on-shell gauge fixing independence for the effective action of composite fields in such formalism is proven. Brief discussion of gravitational-vector induced interaction for Maxwell theory with composite fields is given.
Energy Technology Data Exchange (ETDEWEB)
Lavrov, P.M.; Odintsov, S.D. [Department of Mathematical Analysis, Tomsk State Pedagogical University, Tomsk 634041 (Russia)]|[Department ECM, Faculte de Fisica, Universidad de Barcelona, Diagonal 647, 08028 Barcelona (Spain); Reshetnyak, A.A. [Quantum Field Theory Department, Tomsk State University, Tomsk 634050 (Russia)
1997-07-01
The gauge dependence of the effective action of composite fields for general gauge theories in the framework of the quantization method by Batalin, Lavrov and Tyutin is studied. The corresponding Ward identities are obtained. The variation of composite fields effective action is found in terms of new set of generators depending on composite field. The theorem of the on-shell gauge fixing independence for the effective action of composite fields in such formalism is proven. A brief discussion of gravitational-vector induced interaction for Maxwell theory with composite fields is given. {copyright} {ital 1997 American Institute of Physics.}
CSIR Research Space (South Africa)
Kim, S
2009-01-01
Full Text Available 6.01 Difierent background 8.86 Pay satisfaction 1.25 Supervisor support 7.27 Employee development 1.86 Customer satisfaction 6.83 Innovation 2.94 Employee satisfaction 1.43 Manager goals 5.28 Quality 1.38 Respect 1.48 Retention 0.83 Con ict... for by the facility efiect variability, in the latter the variability is accounted for by the structural dependency as well as the facility efiect. The structural part of the ordinal response SEM is given by ·ij = ¡·ij + »ij; (3.7) where »ij » N (0; diag( 2·1...
Hyper(co)homology for exact left covariant functors and a homology theory for topological spaces
Sklyarenko, E. G.
1995-06-01
Contents Introduction §1. Strong cohomology of dual complexes §2. Hyperhomology §3. Examples §4. Typical limit relations for Steenrod-Sitnikov homology §5. The strong homology of topological spaces §6. On the special position held by singular theory Bibliography
Reid, Jane M
2012-11-22
The evolutionary forces that underlie polyandry, including extra-pair reproduction (EPR) by socially monogamous females, remain unclear. Selection on EPR and resulting evolution have rarely been explicitly estimated or predicted in wild populations, and evolutionary predictions are vulnerable to bias due to environmental covariances and correlated selection through unmeasured traits. However, evolutionary responses to (correlated) selection on any trait can be directly predicted as additive genetic covariances (cov(A)) with appropriate components of relative fitness. I used comprehensive life-history, paternity and pedigree data from song sparrows (Melospiza melodia) to estimate cov(A) between a female's liability to produce extra-pair offspring and two specific fitness components: relative annual reproductive success (ARS) and survival to recruitment. All three traits showed non-zero additive genetic variance. Estimates of cov(A) were positive, predicting evolution towards increased EPR, but 95% credible intervals overlapped zero. There was therefore no conclusive prediction of evolutionary change in EPR due to (correlated) selection through female ARS or recruitment. Negative environmental covariance between EPR and ARS would have impeded evolutionary prediction from phenotypic selection differentials. These analyses demonstrate an explicit quantitative genetic approach to predicting evolutionary responses to components of (correlated) selection on EPR that should be unbiased by environmental covariances and unmeasured traits.
A Covariant Master Theory for Novel Galilean Invariant Models and Massive Gravity
Gabadadze, Gregory; Khoury, Justin; Pirtskhalava, David; Trodden, Mark
2012-01-01
Coupling the galileons to a curved background has been a tradeoff between maintaining second order equations of motion, maintaining the galilean shift symmetries, and allowing the background metric to be dynamical. We propose a construction which can achieve all three for a novel class of galilean invariant models, by coupling a scalar with the galilean symmetry to a massive graviton. This generalizes the brane construction for galileons, by adding to the brane a dynamical metric, (non-universally) interacting with the galileon field. Alternatively, it can be thought of as an extension of the ghost-free massive gravity, or as a massive graviton-galileon scalar-tensor theory. In the decoupling limit of these theories, new kinds of galileon invariant interactions arise between the scalar and the longitudinal mode of the graviton. These have higher order equations of motion and infinite powers of the field, yet are ghost-free.
Yao, De-Liang; Siemens, D.; Bernard, V.; Epelbaum, E.; Gasparyan, A. M.; Gegelia, J.; Krebs, H.; Meißner, Ulf-G.
2016-05-01
We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the S- and P -partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the D and F waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in order to determine the strangeness content of the nucleon, we calculate the octet baryon masses in the presence of decuplet resonances up to next-to-next-to-leading order in SU(3) baryon chiral perturbation theory. The octet baryon sigma terms are predicted as a byproduct of this calculation.
Directory of Open Access Journals (Sweden)
Alarcón Jose Manuel
2014-06-01
Full Text Available We highlight some of the recent advances in the application of chiral effective field theory (chiral EFT with baryons to the πN scattering process. We recall some problems that cast doubt on the applicability of chiral EFT to πN and show how the relativistic formalism, once the Δ(1232-resonance is included as an explicit degree of freedom, solves these issues. Finally it is shown how this approach can be used to extract the σ-terms from phenomenological information.
Quasienergy formulation of damped response theory.
Kristensen, Kasper; Kauczor, Joanna; Kjaergaard, Thomas; Jørgensen, Poul
2009-07-28
We present a quasienergy-based formulation of damped response theory where a common effective lifetime parameter has been introduced for all excited states in terms of complex excitation energies. The introduction of finite excited state lifetimes leads to a set of (complex) damped response equations, which have the same form to all orders in the perturbation. An algorithm is presented for solving the damped response equations in Hartree-Fock theory and Kohn-Sham density functional theory. The use of the quasienergy formulation allows us to obtain directly the computationally simplest expressions for damped response functions by applying a set of response parameter elimination rules, which minimize the total number of damped response equations to be solved. In standard response theory broadened absorption spectra are obtained by ad hoc superimposing lineshape functions onto the absorption stick spectra, whereas an empirical lineshape function common to all excitations is an integrated part of damped response theory. By superimposing the lineshape functions inherent in damped response theory onto the stick spectra of standard response theory, we show that the absorption spectra obtained in standard and damped response theory calculations are identical. We demonstrate that damped response theory may be applied to obtain absorption spectra in all frequency ranges, also those that are not readily addressed using standard response theory. This makes damped response theory an effective tool, e.g., for determining absorption spectra for large molecules, where the density of the excited states may be very high, and where standard response theory therefore is not applicable in practice. A thorough comparison is given between our formulation of damped response theory and the formulation by Norman et al. [J. Chem. Phys. 123, 194103 (2005)].
Yao, De-Liang; Bernard, V; Epelbaum, E; Gasparyan, A M; Gegelia, J; Krebs, H; Meißner, Ulf-G
2016-01-01
We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the $S$- and $P$-partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the $D$ and $F$ waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in ...
Levy Matrices and Financial Covariances
Burda, Zdzislaw; Jurkiewicz, Jerzy; Nowak, Maciej A.; Papp, Gabor; Zahed, Ismail
2003-10-01
In a given market, financial covariances capture the intra-stock correlations and can be used to address statistically the bulk nature of the market as a complex system. We provide a statistical analysis of three SP500 covariances with evidence for raw tail distributions. We study the stability of these tails against reshuffling for the SP500 data and show that the covariance with the strongest tails is robust, with a spectral density in remarkable agreement with random Lévy matrix theory. We study the inverse participation ratio for the three covariances. The strong localization observed at both ends of the spectral density is analogous to the localization exhibited in the random Lévy matrix ensemble. We discuss two competitive mechanisms responsible for the occurrence of an extensive and delocalized eigenvalue at the edge of the spectrum: (a) the Lévy character of the entries of the correlation matrix and (b) a sort of off-diagonal order induced by underlying inter-stock correlations. (b) can be destroyed by reshuffling, while (a) cannot. We show that the stocks with the largest scattering are the least susceptible to correlations, and likely candidates for the localized states. We introduce a simple model for price fluctuations which captures behavior of the SP500 covariances. It may be of importance for assets diversification.
Intersubjectivity, relativistic covariance, and conditionals: response to C. I. J. M. Stuart
de Beauregard, O. Costa
1992-06-01
A misunderstanding persists between Stuart and me, which I do my best to clarify. Bayesian “inverse subjectivities” versus relativistic covariance and “physical intersubjectivity” are discussed. A “joint number of chances” formalism taking care of the propagation of the “probability of causes” is proposed.
The effects of stress and sex on selection, genetic covariance, and the evolutionary response.
Holman, L; Jacomb, F
2017-08-01
The capacity of a population to adapt to selection (evolvability) depends on whether the structure of genetic variation permits the evolution of fitter trait combinations. Selection, genetic variance and genetic covariance can change under environmental stress, and males and females are not genetically independent, yet the combined effects of stress and dioecy on evolvability are not well understood. Here, we estimate selection, genetic (co)variance and evolvability in both sexes of Tribolium castaneum flour beetles under stressful and benign conditions, using a half-sib breeding design. Although stress uncovered substantial latent heritability, stress also affected genetic covariance, such that evolvability remained low under stress. Sexual selection on males and natural selection on females favoured a similar phenotype, and there was positive intersex genetic covariance. Consequently, sexual selection on males augmented adaptation in females, and intralocus sexual conflict was weak or absent. This study highlights that increased heritability does not necessarily increase evolvability, suggests that selection can deplete genetic variance for multivariate trait combinations with strong effects on fitness, and tests the recent hypothesis that sexual conflict is weaker in stressful or novel environments. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.
Energy Technology Data Exchange (ETDEWEB)
Dappiaggi, Claudio [Erwin Schroedinger Institut fuer Mathematische Physik, Wien (Austria); Pinamonti, Nicola [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Porrmann, Martin [KwaZulu-Natal Univ. (South Africa). Quantum Research Group, School of Physics; National Institute for Theoretical Physics, Durban (South Africa)
2010-01-15
In the framework of the algebraic formulation, we discuss and analyse some new features of the local structure of a real scalar quantum field theory in a strongly causal spacetime. In particular we use the properties of the exponential map to set up a local version of a bulk-to-boundary correspondence. The bulk is a suitable subset of a geodesic neighbourhood of any but fixed point p of the underlying background, while the boundary is a part of the future light cone having p as its own tip. In this regime, we provide a novel notion for the extended *-algebra of Wick polynomials on the said cone and, on the one hand, we prove that it contains the information of the bulk counterpart via an injective *-homomorphism while, on the other hand, we associate to it a distinguished state whose pull-back in the bulk is of Hadamard form. The main advantage of this point of view arises if one uses the universal properties of the exponential map and of the light cone in order to show that, for any two given backgrounds M and M{sup '} and for any two subsets of geodesic neighbourhoods of two arbitrary points, it is possible to engineer the above procedure such that the boundary extended algebras are related via a restriction homomorphism. This allows for the pull-back of boundary states in both spacetimes and, thus, to set up a machinery which permits the comparison of expectation values of local field observables in M and M{sup '}. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Dappiaggi, Claudio [Erwin Schroedinger Institut fuer Mathematische Physik, Wien (Austria); Pinamonti, Nicola [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Porrmann, Martin [KwaZulu-Natal Univ. (South Africa). Quantum Research Group, School of Physics; National Institute for Theoretical Physics, Durban (South Africa)
2010-01-15
In the framework of the algebraic formulation, we discuss and analyse some new features of the local structure of a real scalar quantum field theory in a strongly causal spacetime. In particular we use the properties of the exponential map to set up a local version of a bulk-to-boundary correspondence. The bulk is a suitable subset of a geodesic neighbourhood of any but fixed point p of the underlying background, while the boundary is a part of the future light cone having p as its own tip. In this regime, we provide a novel notion for the extended *-algebra of Wick polynomials on the said cone and, on the one hand, we prove that it contains the information of the bulk counterpart via an injective *-homomorphism while, on the other hand, we associate to it a distinguished state whose pull-back in the bulk is of Hadamard form. The main advantage of this point of view arises if one uses the universal properties of the exponential map and of the light cone in order to show that, for any two given backgrounds M and M{sup '} and for any two subsets of geodesic neighbourhoods of two arbitrary points, it is possible to engineer the above procedure such that the boundary extended algebras are related via a restriction homomorphism. This allows for the pull-back of boundary states in both spacetimes and, thus, to set up a machinery which permits the comparison of expectation values of local field observables in M and M{sup '}. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Lensky, Vadim, E-mail: lensky@itep.ru [Institut für Kernphysik and PRISMA Cluster of Excellence, Johannes Gutenberg Universität Mainz, 55128, Mainz (Germany); Institute for Theoretical and Experimental Physics, 117218, Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Moscow (Russian Federation); Theoretical Physics Group, School of Physics and Astronomy, University of Manchester, M13 9PL, Manchester (United Kingdom); McGovern, Judith A. [Theoretical Physics Group, School of Physics and Astronomy, University of Manchester, M13 9PL, Manchester (United Kingdom); Pascalutsa, Vladimir [Institut für Kernphysik and PRISMA Cluster of Excellence, Johannes Gutenberg Universität Mainz, 55128, Mainz (Germany)
2015-12-19
We update the predictions of the SU(2) baryon chiral perturbation theory for the dipole polarisabilities of the proton, {α_E_1, β_M_1}{sub p}={11.2(0.7), 3.9(0.7)}×10{sup -4} fm{sup 3}, and obtain the corresponding predictions for the quadrupole, dispersive, and spin polarisabilities: {α_E_2, β_M_2}{sub p}={17.3(3.9), -15.5(3.5)}×10{sup -4} fm{sup 5}, {α_E_1_ν, β_M_1_ν}{sub p}={-1.3(1.0), 7.1(2.5)}×10{sup -4} fm{sup 5}, and {γ_E_1_E_1, γ_M_1_M_1,γ_E_1_M_2, γ_M_1_E_2}{sub p}={-3.3(0.8), 2.9(1.5), 0.2(0.2),1.1(0.3)}×10{sup -4} fm{sup 4}. The results for the scalar polarisabilities are in significant disagreement with semi-empirical analyses based on dispersion relations; however, the results for the spin polarisabilities agree remarkably well. Results for proton Compton-scattering multipoles and polarised observables up to the Delta(1232) resonance region are presented too. The asymmetries Σ{sub 3} and Σ{sub 2x} reproduce the experimental data from LEGS and MAMI. Results for Σ{sub 2z} agree with a recent sum rule evaluation in the forward kinematics. The asymmetry Σ{sub 1z} near the pion production threshold shows a large sensitivity to chiral dynamics, but no data is available for this observable. We also provide the predictions for the polarisabilities of the neutron, the numerical values being {α_E_1, β_M_1}{sub n}={13.7(3.1), 4.6(2.7)}×10{sup -4} fm{sup 3}, {α_E_2, β_M_2}{sub n}={16.2(3.7), -15.8(3.6)}×10{sup -4} fm{sup 5}, {α_E_1_ν, β_M_1_ν}{sub n}={0.1(1.0), 7.2(2.5)}×10{sup -4} fm{sup 5}, and {γ_E_1_E_1, γ_M_1_M_1, γ_E_1_M_2, γ_M_1_E_2}{sub n}={-4.7(1.1),2.9(1.5), 0.2(0.2), 1.6(0.4)}×10{sup -4} fm{sup 4}. The neutron dynamical polarisabilities and multipoles are examined too. We also discuss subtleties related to matching the dynamical and static polarisabilities.
Energy Technology Data Exchange (ETDEWEB)
Lensky, Vadim [Johannes Gutenberg Universitaet Mainz, Institut fuer Kernphysik and PRISMA Cluster of Excellence, Mainz (Germany); Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); University of Manchester, Theoretical Physics Group, School of Physics and Astronomy, Manchester (United Kingdom); McGovern, Judith A. [University of Manchester, Theoretical Physics Group, School of Physics and Astronomy, Manchester (United Kingdom); Pascalutsa, Vladimir [Johannes Gutenberg Universitaet Mainz, Institut fuer Kernphysik and PRISMA Cluster of Excellence, Mainz (Germany)
2015-12-15
We update the predictions of the SU(2) baryon chiral perturbation theory for the dipole polarisabilities of the proton, {α_E_1, β_M_1}{sub p} = {11.2(0.7), 3.9(0.7)} x 10{sup -4} fm{sup 3}, and obtain the corresponding predictions for the quadrupole, dispersive, and spin polarisabilities: {α_E_2, β_M_2}{sub p} = {17.3(3.9),.15.5(3.5)} x 10{sup -4} fm{sup 5}, {α_E_1_ν, β_M_1_ν}{sub p} = {-1.3(1.0), 7.1(2.5)} x 10{sup -4} fm{sup 5}, and {γ_E_1_E_1, γ_M_1_M_1, γ_E_1_M_2, γ_M_1_E_2}{sub p} = {-3.3(0.8), 2.9(1.5), 0.2(0.2), 1.1 (0.3)} x 10{sup -4} fm{sup 4}. The results for the scalar polarisabilities are in significant disagreement with semi-empirical analyses based on dispersion relations; however, the results for the spin polarisabilities agree remarkably well. Results for proton Compton-scattering multipoles and polarised observables up to the Delta(1232) resonance region are presented too. The asymmetries Σ{sub 3} and Σ{sub 2x} reproduce the experimental data from LEGS and MAMI. Results for Σ{sub 2z} agree with a recent sum rule evaluation in the forward kinematics. The asymmetry Σ{sub 1z} near the pion production threshold shows a large sensitivity to chiral dynamics, but no data is available for this observable. We also provide the predictions for the polarisabilities of the neutron, the numerical values being {α_E_1, β_M_1}{sub n} = {13.7(3.1), 4.6(2.7)} x 10{sup -4} fm{sup 3}, {α_E_2, β_M_2}{sub n} = {16.2(3.7),.15.8(3.6)} x 10{sup -4} fm{sup 5}, {α_E_1_ν, β_M_1_ν}{sub n} = {0.1(1.0), 7.2(2.5)} x 10{sup -4} fm{sup 5}, and {γ_E_1_E_1, γ_M_1_M_1, γ_E_1_M_2, γ_M_1_E_2}{sub n} = {-4.7(1.1), 2.9(1.5), 0.2(0.2), 1.6(0.4)} x 10{sup -4} fm{sup 4}. The neutron dynamical polarisabilities and multipoles are examined too. We also discuss subtleties related to matching the dynamical and static polarisabilities. (orig.)
Simon, Richard; Simon, Noah Robin
2011-07-01
We demonstrate that clinical trials using response adaptive randomized treatment assignment rules are subject to substantial bias if there are time trends in unknown prognostic factors and standard methods of analysis are used. We develop a general class of randomization tests based on generating the null distribution of a general test statistic by repeating the adaptive randomized treatment assignment rule holding fixed the sequence of outcome values and covariate vectors actually observed in the trial. We develop broad conditions on the adaptive randomization method and the stochastic mechanism by which outcomes and covariate vectors are sampled that ensure that the type I error is controlled at the level of the randomization test. These conditions ensure that the use of the randomization test protects the type I error against time trends that are independent of the treatment assignments. Under some conditions in which the prognosis of future patients is determined by knowledge of the current randomization weights, the type I error is not strictly protected. We show that response-adaptive randomization can result in substantial reduction in statistical power when the type I error is preserved. Our results also ensure that type I error is controlled at the level of the randomization test for adaptive stratification designs used for balancing covariates.
Reader Response Theory and Classroom Practices.
Bush, Harold K., Jr.
1994-01-01
Presents annotations of nine journal articles, monographs, and "learning packages" (published between 1989 and 1993) that examine teaching approaches founded upon the insights of reader response theory. (RS)
Energy Technology Data Exchange (ETDEWEB)
Franz Gross; Alfred Stadler
2008-02-11
Using the covariant spectator theory (CST), we present two one boson exchange kernels that have been successfully adjusted to fit the 2007 world $np$ data (containing 3788 data) below 350 MeV. One model (which we designate WJC-1) has 27 parameters and fits with a chi2/N = 1.06. The other model (designated WJC-2) has only 15 parameters and fits with a chi2/N = 1.12. Both of these models also reproduce the experimental triton binding energy without introducing additional irreducible three-nucleon forces. One result of this work is a new phase shift analysis, updated for all data until 2006, which is useful even if one does not work within the CST. In carrying out these fits we have reviewed the entire data base, adding new data not previously used in other high precision fits and restoring some data omitted in previous fits. A full discussion and evaluation of the 2007 data base is presented.
Linear response theory for quantum open systems
Wei, J. H.; Yan, YiJing
2011-01-01
Basing on the theory of Feynman's influence functional and its hierarchical equations of motion, we develop a linear response theory for quantum open systems. Our theory provides an effective way to calculate dynamical observables of a quantum open system at its steady-state, which can be applied to various fields of non-equilibrium condensed matter physics.
Energy Technology Data Exchange (ETDEWEB)
Pang, Yang [Columbia Univ., New York, NY (United States)]|[Brookhaven National Labs., Upton, NY (United States)
1997-09-22
Many phenomenological models for relativistic heavy ion collisions share a common framework - the relativistic Boltzmann equations. Within this framework, a nucleus-nucleus collision is described by the evolution of phase-space distributions of several species of particles. The equations can be effectively solved with the cascade algorithm by sampling each phase-space distribution with points, i.e. {delta}-functions, and by treating the interaction terms as collisions of these points. In between collisions, each point travels on a straight line trajectory. In most implementations of the cascade algorithm, each physical particle, e.g. a hadron or a quark, is often represented by one point. Thus, the cross-section for a collision of two points is just the cross-section of the physical particles, which can be quite large compared to the local density of the system. For an ultra-relativistic nucleus-nucleus collision, this could lead to a large violation of the Lorentz invariance. By using the invariance property of the Boltzmann equation under a scale transformation, a Lorentz invariant cascade algorithm can be obtained. The General Cascade Program - GCP - is a tool for solving the relativistic Boltzmann equation with any number of particle species and very general interactions with the cascade algorithm.
An Overview of Reader-Response Theory
Institute of Scientific and Technical Information of China (English)
高扬
2008-01-01
This paper aims to give a brief introduction to reader-response theory.including its origin,main concepts and general classification. with the following conclusion drawn in the end: reader-response theory. in spite of its subjectivity,has provided a broader horizon for literary criticism due to its variety and openness.
Directory of Open Access Journals (Sweden)
Geoffrey D Findlay
2014-01-01
Full Text Available Seminal fluid proteins transferred from males to females during copulation are required for full fertility and can exert dramatic effects on female physiology and behavior. In Drosophila melanogaster, the seminal protein sex peptide (SP affects mated females by increasing egg production and decreasing receptivity to courtship. These behavioral changes persist for several days because SP binds to sperm that are stored in the female. SP is then gradually released, allowing it to interact with its female-expressed receptor. The binding of SP to sperm requires five additional seminal proteins, which act together in a network. Hundreds of uncharacterized male and female proteins have been identified in this species, but individually screening each protein for network function would present a logistical challenge. To prioritize the screening of these proteins for involvement in the SP network, we used a comparative genomic method to identify candidate proteins whose evolutionary rates across the Drosophila phylogeny co-vary with those of the SP network proteins. Subsequent functional testing of 18 co-varying candidates by RNA interference identified three male seminal proteins and three female reproductive tract proteins that are each required for the long-term persistence of SP responses in females. Molecular genetic analysis showed the three new male proteins are required for the transfer of other network proteins to females and for SP to become bound to sperm that are stored in mated females. The three female proteins, in contrast, act downstream of SP binding and sperm storage. These findings expand the number of seminal proteins required for SP's actions in the female and show that multiple female proteins are necessary for the SP response. Furthermore, our functional analyses demonstrate that evolutionary rate covariation is a valuable predictive tool for identifying candidate members of interacting protein networks.
Towards a Culturally Situated Reader Response Theory
Brooks, Wanda; Browne, Susan
2012-01-01
This article describes a theory of how culture enables literary interpretations of texts. We begin with a brief overview of the reader response field. From there, we introduce the theory and provide illustrative participant data examples. These data examples illustrate the four cultural positions middle grade students in our research assumed when…
Asymptotic Theory for the QMLE in GARCH-X Models with Stationary and Non-Stationary Covariates
DEFF Research Database (Denmark)
Han, Heejoon; Kristensen, Dennis
This paper investigates the asymptotic properties of the Gaussian quasi-maximum-likelihood estimators (QMLE’s) of the GARCH model augmented by including an additional explanatory variable - the so-called GARCH-X model. The additional covariate is allowed to exhibit any degree of persistence as ca...
Transcending Bias through Reader-Response Theory
Soublis, Theoni; Winkler, Erik
2004-01-01
The preservice teachers from all disciplines will be benefited if they incorporate reading in their classes according to Dr. Louise Rosenblatt's reader-response theory. A teacher's experience with her students while reading Chris Crutcher's "Staying Fat for Sarah Byanes" in the Secondary Content Area and a student's response on the novel are…
Item response theory - A first approach
Nunes, Sandra; Oliveira, Teresa; Oliveira, Amílcar
2017-07-01
The Item Response Theory (IRT) has become one of the most popular scoring frameworks for measurement data, frequently used in computerized adaptive testing, cognitively diagnostic assessment and test equating. According to Andrade et al. (2000), IRT can be defined as a set of mathematical models (Item Response Models - IRM) constructed to represent the probability of an individual giving the right answer to an item of a particular test. The number of Item Responsible Models available to measurement analysis has increased considerably in the last fifteen years due to increasing computer power and due to a demand for accuracy and more meaningful inferences grounded in complex data. The developments in modeling with Item Response Theory were related with developments in estimation theory, most remarkably Bayesian estimation with Markov chain Monte Carlo algorithms (Patz & Junker, 1999). The popularity of Item Response Theory has also implied numerous overviews in books and journals, and many connections between IRT and other statistical estimation procedures, such as factor analysis and structural equation modeling, have been made repeatedly (Van der Lindem & Hambleton, 1997). As stated before the Item Response Theory covers a variety of measurement models, ranging from basic one-dimensional models for dichotomously and polytomously scored items and their multidimensional analogues to models that incorporate information about cognitive sub-processes which influence the overall item response process. The aim of this work is to introduce the main concepts associated with one-dimensional models of Item Response Theory, to specify the logistic models with one, two and three parameters, to discuss some properties of these models and to present the main estimation procedures.
CSIR Research Space (South Africa)
Kim, S
2008-03-01
Full Text Available Motivated by a large multilevel survey conducted by the US Veterans Health Administration (VHA), we propose a structural equations model which involves a set of latent variables to capture dependence between different responses, a set of facility...
Covariant Projective Extensions
Institute of Scientific and Technical Information of China (English)
许天周; 梁洁
2003-01-01
@@ The theory of crossed products of C*-algebras by groups of automorphisms is a well-developed area of the theory of operator algebras. Given the importance and the success ofthat theory, it is natural to attempt to extend it to a more general situation by, for example,developing a theory of crossed products of C*-algebras by semigroups of automorphisms, or evenof endomorphisms. Indeed, in recent years a number of papers have appeared that are concernedwith such non-classicaltheories of covariance algebras, see, for instance [1-3].
Ibort, A
2012-01-01
In these three lectures we will discuss some fundamental aspects of the theory of self-adjoint extensions of the covariant Laplace-Beltrami and Dirac operators on compact Riemannian manifolds with smooth boundary emphasizing the relation with the theory of global boundary conditions. Self-adjoint extensions of symmetric operators, specially of the Laplace-Beltrami and Dirac operators, are fundamental in Quantum Physics as they determine either the energy of quantum systems and/or their unitary evolution. The well-known von Neumann's theory of self-adjoint extensions of symmetric operators is not always easily applicable to differential operators, while the description of extensions in terms of boundary conditions constitutes a more natural approach. Thus an effort is done in offering a description of self-adjoint extensions in terms of global boundary conditions showing how an important family of self-adjoint extensions for the Laplace-Beltrami and Dirac operators are easily describable in this way. Moreover ...
Paek, Insu; Cai, Li
2014-01-01
The present study was motivated by the recognition that standard errors (SEs) of item response theory (IRT) model parameters are often of immediate interest to practitioners and that there is currently a lack of comparative research on different SE (or error variance-covariance matrix) estimation procedures. The present study investigated item…
Paek, Insu; Cai, Li
2014-01-01
The present study was motivated by the recognition that standard errors (SEs) of item response theory (IRT) model parameters are often of immediate interest to practitioners and that there is currently a lack of comparative research on different SE (or error variance-covariance matrix) estimation procedures. The present study investigated item…
Determining the continuous family of quantum Fisher information from linear-response theory
Shitara, Tomohiro; Ueda, Masahito
2016-12-01
The quantum Fisher information represents a continuous family of metrics on the space of quantum states and places the fundamental limit on the accuracy of quantum state estimation. We show that the entire family of quantum Fisher information can be determined from linear-response theory through generalized covariances. We derive the generalized fluctuation-dissipation theorem that relates linear-response functions to generalized covariances and hence allows us to determine the quantum Fisher information from linear-response functions, which are experimentally measurable quantities. As an application, we examine the skew information, which is a quantum Fisher information, of a harmonic oscillator in thermal equilibrium, and show that the equality of the skew-information-based uncertainty relation holds.
Covariant canonical quantization
Energy Technology Data Exchange (ETDEWEB)
Hippel, G.M. von [University of Regina, Department of Physics, Regina, Saskatchewan (Canada); Wohlfarth, M.N.R. [Universitaet Hamburg, Institut fuer Theoretische Physik, Hamburg (Germany)
2006-09-15
We present a manifestly covariant quantization procedure based on the de Donder-Weyl Hamiltonian formulation of classical field theory. This procedure agrees with conventional canonical quantization only if the parameter space is d=1 dimensional time. In d>1 quantization requires a fundamental length scale, and any bosonic field generates a spinorial wave function, leading to the purely quantum-theoretical emergence of spinors as a byproduct. We provide a probabilistic interpretation of the wave functions for the fields, and we apply the formalism to a number of simple examples. These show that covariant canonical quantization produces both the Klein-Gordon and the Dirac equation, while also predicting the existence of discrete towers of identically charged fermions with different masses. Covariant canonical quantization can thus be understood as a ''first'' or pre-quantization within the framework of conventional QFT. (orig.)
Covariant canonical quantization
Von Hippel, G M; Hippel, Georg M. von; Wohlfarth, Mattias N.R.
2006-01-01
We present a manifestly covariant quantization procedure based on the de Donder-Weyl Hamiltonian formulation of classical field theory. Covariant canonical quantization agrees with conventional canonical quantization only if the parameter space is d=1 dimensional time. In d>1 quantization requires a fundamental length scale, and any bosonic field generates a spinorial wave function, leading to the purely quantum-theoretical emergence of spinors as a byproduct. We provide a probabilistic interpretation of the wave functions for the fields, and apply the formalism to a number of simple examples. These show that covariant canonical quantization produces both the Klein-Gordon and the Dirac equation, while also predicting the existence of discrete towers of identically charged fermions with different masses.
Beyond Text Theory: Understanding Literary Response
Miall, David S.; Kuiken, Don
1994-01-01
Approaches to text comprehension that focus on propositional, inferential, and elaborative processes have often been considered capable of extension in principle to literary texts, such as stories or poems. However, we argue that literary response is influenced by stylistic features that result in defamiliarization; that defamiliarization invokes feeling which calls on personal perspectives and meanings; and that these aspects of literary response are not addressed by current text theories. T...
A modular approach for item response theory modeling with the R package flirt.
Jeon, Minjeong; Rijmen, Frank
2016-06-01
The new R package flirt is introduced for flexible item response theory (IRT) modeling of psychological, educational, and behavior assessment data. flirt integrates a generalized linear and nonlinear mixed modeling framework with graphical model theory. The graphical model framework allows for efficient maximum likelihood estimation. The key feature of flirt is its modular approach to facilitate convenient and flexible model specifications. Researchers can construct customized IRT models by simply selecting various modeling modules, such as parametric forms, number of dimensions, item and person covariates, person groups, link functions, etc. In this paper, we describe major features of flirt and provide examples to illustrate how flirt works in practice.
Lee, Taejin
2016-01-01
We construct a covariant open bosonic string field theory on multiple D-branes, which reduces to a non-Abelian group Yang-Mills gauge theory in the zero-slope limit. Making use of the first quantized open bosonic string in the proper time gauge, we convert the string amplitudes given by the Polyakov path integrals on string world sheets into those of the second quantized theory. On multiple D-branes, the string field takes values in the Lie-algebra of $U(N)$ group and the three-string vertex function must be invariant under the global $U(N)$ transformation. This requirement together with the condition that the string field theory reduces to the non-Abelian gauge field theory in the zero-slope limit, uniquely determines the three-string vertex function. We also examine the effective four-string vertex diagrams generated perturbatively by the three-string vertex at tree level. In the zero-slope limit they reduce to the tree diagrams with four external gauge fields with an intermediate massless gauge field propa...
Liu, Yang; Magnus, Brooke E; Thissen, David
2016-06-01
Differential item functioning (DIF), referring to between-group variation in item characteristics above and beyond the group-level disparity in the latent variable of interest, has long been regarded as an important item-level diagnostic. The presence of DIF impairs the fit of the single-group item response model being used, and calls for either model modification or item deletion in practice, depending on the mode of analysis. Methods for testing DIF with continuous covariates, rather than categorical grouping variables, have been developed; however, they are restrictive in parametric forms, and thus are not sufficiently flexible to describe complex interaction among latent variables and covariates. In the current study, we formulate the probability of endorsing each test item as a general bivariate function of a unidimensional latent trait and a single covariate, which is then approximated by a two-dimensional smoothing spline. The accuracy and precision of the proposed procedure is evaluated via Monte Carlo simulations. If anchor items are available, we proposed an extended model that simultaneously estimates item characteristic functions (ICFs) for anchor items, ICFs conditional on the covariate for non-anchor items, and the latent variable density conditional on the covariate-all using regression splines. A permutation DIF test is developed, and its performance is compared to the conventional parametric approach in a simulation study. We also illustrate the proposed semiparametric DIF testing procedure with an empirical example.
Messina, Paula V; Besada-Porto, Jose Miguel; González-Díaz, Humberto; Ruso, Juan M
2015-11-10
Studies of the self-aggregation of binary systems are of both theoretical and practical importance. They provide an opportunity to investigate the influence of the molecular structure of the hydrophobe on the nonideality of mixing. On the other hand, linear free energy relationship (LFER) models, such as Hansch's equations, may be used to predict the properties of chemical compounds such as drugs or surfactants. However, the task becomes more difficult once we want to predict simultaneaously the effect over multiple output properties of binary systems of perturbations under multiple input experimental boundary conditions (b(j)). As a consequence, we need computational chemistry or chemoinformatics models that may help us to predict different properties of the autoaggregation process of mixed surfactants under multiple conditions. In this work, we have developed the first model that combines perturbation theory (PT) and LFER ideas. The model uses as input covariance PT operators (CPTOs). CPTOs are calculated as the difference between covariance ΔCov((i)μ(k)) functions before and after multiple perturbations in the binary system. In turn, covariances calculated as the product of two Box-Jenkins operators (BJO) operators. BJOs are used to measure the deviation of the structure of different chemical compounds from a set of molecules measured under a given subset of experimental conditions. The best CPT-LFER model found predicted the effects of 25,000 perturbations over 9 different properties of binary systems. We also reported experimental studies of different experimental properties of the binary system formed by sodium glycodeoxycholate and didodecyldimethylammonium bromide (NaGDC-DDAB). Last, we used our CPT-LFER model to carry out a 1000 data point simulation of the properties of the NaGDC-DDAB system under different conditions not studied experimentally.
Lu, K Q; Li, Z P; Yao, J M; Meng, J
2015-01-01
We report the first global study of dynamic correlation energies (DCEs) associated with rotational motion and quadrupole shape vibrational motion in a covariant energy density functional (CEDF) for 575 even-even nuclei with proton numbers ranging from $Z=8$ to $Z=108$ by solving a five-dimensional collective Hamiltonian, the collective parameters of which are determined from triaxial relativistic mean-field plus BCS calculation using the PC-PK1 force. After taking into account these beyond mean-field DCEs, the root-mean-square (rms) deviation with respect to nuclear masses is reduced significantly down to 1.14 MeV, which is smaller than those of other successful CEDFs: NL3* (2.96 MeV), DD-ME2 (2.39 MeV), DD-ME$\\delta$ (2.29 MeV) and DD-PC1 (2.01 MeV). Moreover, the rms deviation for two-nucleon separation energies is reduced by $\\sim34\\%$ in comparison with cranking prescription.
Yao, J M
2016-01-01
We discuss anharmonicity of the multi-octupole-phonon states in $^{208}$Pb based on a covariant density functional theory, by fully taking into account the interplay between the quadrupole and the octupole degrees of freedom. Our results indicate the existence of a large anharmonicity in the transition strengths, even though the excitation energies are similar to those in the harmonic limit. We also show that the quadrupole-shape fluctuation significantly enhances the fragmentation of the two-octupole-phonon states in $^{208}$Pb. Using those transition strengths as inputs to coupled channels calculations, we then discuss the fusion reaction of $^{16}$O+$^{208}$Pb at energies around the Coulomb barrier. We show that the anharmonicity of the octupole vibrational excitation considerably improves previous coupled-channels calculations in the harmonic oscillator limit, significantly reducing the height of the main peak in the fusion barrier distribution.
Xu, K.; Metzger, S.; Kljun, N.; Taylor, J. R.; Desai, A. R.
2013-12-01
Tower-based eddy-covariance (EC) measurements are suited to continuously monitor the exchange of heat, water vapor, CO2 and other surface fluxes above selected sites. However, these results represent only the immediate surrounding of a measurement location, unless all areas around the flux tower are biophysically identical. This is hardly the case for research sites in somewhat heterogeneous and structured terrain, as typical for most EC measurement locations. For remote sensing and numerical model applications, it is desirable to improve the spatial representativeness of tower flux measurements. The objective of this study is to provide a consistent flux time-series for a selected region, rather than for a spatio-temporally variable patch of surface close to the measurement location. Environmental response functions (ERFs) are capable of explicitly relating flux observations (responses) to meteorological forcing and biophysical surface properties (drivers). However, thus far ERF have been developed with and utilized for aircraft-based measurements in the spatial domain (Metzger et al., 2013). The present study explores the potential for applying ERF to ';rectify' the spatial representativeness of tower-based EC measurements to pre-defined regions. The underlying principle is to extract the relationship between biophysical drivers and ecological responses from measurements in the time-domain under varying environmental conditions. Provided sufficiently good calibration, the resulting ERF can then be used for extrapolating the surface-atmosphere exchange into areas adjacent to the immediate airshed of the tower measurement. The subsequent steps of the ERF methodology are: (i) time-frequency decomposition of 10Hz tower EC data, providing high temporal resolution of the flux observations without neglecting long-wavelength contributions, (ii) quantification of continuous and biophysically relevant land cover properties in the flux footprint of each observation, (iii
Saltas, Ippocratis D
2016-01-01
We derive the 1-loop effective action of the cubic Galileon coupled to quantum-gravitational fluctuations in a background and gauge-independent manner, employing the covariant framework of DeWitt and Vilkovisky. Although the bare action respects shift symmetry, the coupling to gravity induces an effective mass to the scalar, of the order of the cosmological constant, as a direct result of the non-flat field-space metric, the latter ensuring the field-reparametrization invariance of the formalism. Within a gauge-invariant regularization scheme, we discover novel, gravitationally induced non-Galileon higher-derivative interactions in the effective action. These terms, previously unnoticed within standard, non-covariant frameworks, are not Planck suppressed. Unless tuned to be sub-dominant, their presence could have important implications for the classical and quantum phenomenology of the theory.
Capri, M A L; Pereira, A D; Fiorentini, D; Guimaraes, M S; Mintz, B W; Palhares, L F; Sorella, S P
2016-01-01
In order to construct a gauge invariant two-point function in a Yang-Mills theory, we propose the use of the all-order gauge invariant transverse configurations A^h. Such configurations can be obtained through the minimization of the functional A^2_{min} along the gauge orbit within the BRST invariant formulation of the Gribov-Zwanziger framework recently put forward in [1,2] for the class of the linear covariant gauges. This correlator turns out to provide a characterization of non-perturbative aspects of the theory in a BRST invariant and gauge parameter independent way. In particular, it turns out that the poles of are the same as those of the transverse part of the gluon propagator, which are also formally shown to be independent of the gauge parameter entering the gauge condition through the Nielsen identities. The latter follow from the new exact BRST invariant formulation introduced before. Moreover, the correlator enables us to attach a BRST invariant meaning to the possible positivity violation of ...
Deriving covariant holographic entanglement
Dong, Xi; Lewkowycz, Aitor; Rangamani, Mukund
2016-11-01
We provide a gravitational argument in favour of the covariant holographic entanglement entropy proposal. In general time-dependent states, the proposal asserts that the entanglement entropy of a region in the boundary field theory is given by a quarter of the area of a bulk extremal surface in Planck units. The main element of our discussion is an implementation of an appropriate Schwinger-Keldysh contour to obtain the reduced density matrix (and its powers) of a given region, as is relevant for the replica construction. We map this contour into the bulk gravitational theory, and argue that the saddle point solutions of these replica geometries lead to a consistent prescription for computing the field theory Rényi entropies. In the limiting case where the replica index is taken to unity, a local analysis suffices to show that these saddles lead to the extremal surfaces of interest. We also comment on various properties of holographic entanglement that follow from this construction.
Deriving covariant holographic entanglement
Dong, Xi; Rangamani, Mukund
2016-01-01
We provide a gravitational argument in favour of the covariant holographic entanglement entropy proposal. In general time-dependent states, the proposal asserts that the entanglement entropy of a region in the boundary field theory is given by a quarter of the area of a bulk extremal surface in Planck units. The main element of our discussion is an implementation of an appropriate Schwinger-Keldysh contour to obtain the reduced density matrix (and its powers) of a given region, as is relevant for the replica construction. We map this contour into the bulk gravitational theory, and argue that the saddle point solutions of these replica geometries lead to a consistent prescription for computing the field theory Renyi entropies. In the limiting case where the replica index is taken to unity, a local analysis suffices to show that these saddles lead to the extremal surfaces of interest. We also comment on various properties of holographic entanglement that follow from this construction.
Covariant holographic entanglement negativity
Chaturvedi, Pankaj; Sengupta, Gautam
2016-01-01
We conjecture a holographic prescription for the covariant entanglement negativity of $d$-dimensional conformal field theories dual to non static bulk $AdS_{d+1}$ gravitational configurations in the framework of the $AdS/CFT$ correspondence. Application of our conjecture to a $AdS_3/CFT_2$ scenario involving bulk rotating BTZ black holes exactly reproduces the entanglement negativity of the corresponding $(1+1)$ dimensional conformal field theories and precisely captures the distillable quantum entanglement. Interestingly our conjecture for the scenario involving dual bulk extremal rotating BTZ black holes also accurately leads to the entanglement negativity for the chiral half of the corresponding $(1+1)$ dimensional conformal field theory at zero temperature.
Estimating Cosmological Parameter Covariance
Taylor, Andy
2014-01-01
We investigate the bias and error in estimates of the cosmological parameter covariance matrix, due to sampling or modelling the data covariance matrix, for likelihood width and peak scatter estimators. We show that these estimators do not coincide unless the data covariance is exactly known. For sampled data covariances, with Gaussian distributed data and parameters, the parameter covariance matrix estimated from the width of the likelihood has a Wishart distribution, from which we derive the mean and covariance. This mean is biased and we propose an unbiased estimator of the parameter covariance matrix. Comparing our analytic results to a numerical Wishart sampler of the data covariance matrix we find excellent agreement. An accurate ansatz for the mean parameter covariance for the peak scatter estimator is found, and we fit its covariance to our numerical analysis. The mean is again biased and we propose an unbiased estimator for the peak parameter covariance. For sampled data covariances the width estimat...
Nevala, James D; Gray, Nicholas J; McGahan, Joseph R; Minchew, Teresa
2006-03-01
The authors replicated and extended a test of Epstein's cognitive-experiential self-theory (CEST; S. Epstein, 1973, 1980, 1985, 1994, 2003) regarding subjective estimates of the relationship between freedom and responsibility. CEST predicts that information in the form of sexually provocative images is likely to be processed by the experiential system. The authors' hypothesis was that such experiential processing would cause an increase in the likelihood of participants endorsing as true a statement that proposed a negative correlation between freedom and responsibility. University students (N = 97) in introductory psychology classes viewed 25 images of either men or women in provocative clothing, or a control consisting of academic journal covers, after which they responded to 24 statements proposing either a positive, negative, or noncontingent relationship between freedom and responsibility. Judgments were analyzed according to perceiver gender and target gender, as well as the framing of the proposition and its contingency category. The hypothesis was supported for the men and to a lesser extent for the women. Although priming the experiential system by exposing participants to sexually provocative images did not change endorsement rates of positive contingencies, it did lead to an increase in the likelihood of simultaneously endorsing negative contingencies.
Measuring student learning with item response theory
Directory of Open Access Journals (Sweden)
Young-Jin Lee
2008-01-01
Full Text Available We investigate short-term learning from hints and feedback in a Web-based physics tutoring system. Both the skill of students and the difficulty and discrimination of items were determined by applying item response theory (IRT to the first answers of students who are working on for-credit homework items in an introductory Newtonian physics course. We show that after tutoring a shifted logistic item response function with lower discrimination fits the students’ second responses to an item previously answered incorrectly. Student skill decreased by 1.0 standard deviation when students used no tutoring between their (incorrect first and second attempts, which we attribute to “item-wrong bias.” On average, using hints or feedback increased students’ skill by 0.8 standard deviation. A skill increase of 1.9 standard deviation was observed when hints were requested after viewing, but prior to attempting to answer, a particular item. The skill changes measured in this way will enable the use of IRT to assess students based on their second attempt in a tutoring environment.
Extending Item Response Theory to Online Homework
Kortemeyer, Gerd
2014-01-01
Item Response Theory becomes an increasingly important tool when analyzing ``Big Data'' gathered from online educational venues. However, the mechanism was originally developed in traditional exam settings, and several of its assumptions are infringed upon when deployed in the online realm. For a large enrollment physics course for scientists and engineers, the study compares outcomes from IRT analyses of exam and homework data, and then proceeds to investigate the effects of each confounding factor introduced in the online realm. It is found that IRT yields the correct trends for learner ability and meaningful item parameters, yet overall agreement with exam data is moderate. It is also found that learner ability and item discrimination is over wide ranges robust with respect to model assumptions and introduced noise, less so than item difficulty.
Pryor, P L; McGahan, J R; Hutto, C W; Williamson, J D
2000-11-01
The authors evaluated subjective estimates of the relationship between freedom and responsibility under predictions made in accordance with cognitive-experiential self-theory (CEST; V. Denes-Raj & S. Epstein, 1994; S. Epstein, A. Lipson, C. Holstein, & E. Huh, 1992; S. Epstein, R. Pacini, V. Denes-Raj, & H. Meier, 1996; L. A. Kirkpatrick & S. Epstein, 1992). Half of the participants viewed sexually stimulating primes before making judgments. The other participants viewed neutral stimuli before making judgments. Two dependent measures were used: A set of alternate-forms propositions measured perceived relationships between the variables, and response latencies were used to evaluate the hypothesis that persons operating experientially would make judgments faster than persons operating rationally. Results indicated a significant effect for the priming condition with respect to the within-subject dependent variable. In accordance with predictions, further analysis indicated that positive contingency items were endorsed less often by primed participants, and negative contingency items were endorsed more often by primed participants. Results are in line with predictions afforded by the CEST model. Implications are discussed.
Item response theory for measurement validity.
Yang, Frances M; Kao, Solon T
2014-06-01
Item response theory (IRT) is an important method of assessing the validity of measurement scales that is underutilized in the field of psychiatry. IRT describes the relationship between a latent trait (e.g., the construct that the scale proposes to assess), the properties of the items in the scale, and respondents' answers to the individual items. This paper introduces the basic premise, assumptions, and methods of IRT. To help explain these concepts we generate a hypothetical scale using three items from a modified, binary (yes/no) response version of the Center for Epidemiological Studies-Depression scale that was administered to 19,399 respondents. We first conducted a factor analysis to confirm the unidimensionality of the three items and then proceeded with Mplus software to construct the 2-Parameter Logic (2-PL) IRT model of the data, a method which allows for estimates of both item discrimination and item difficulty. The utility of this information both for clinical purposes and for scale construction purposes is discussed.
Land, M C
2001-01-01
This paper examines the Stark effect, as a first order perturbation of manifestly covariant hydrogen-like bound states. These bound states are solutions to a relativistic Schr\\"odinger equation with invariant evolution parameter, and represent mass eigenstates whose eigenvalues correspond to the well-known energy spectrum of the non-relativistic theory. In analogy to the nonrelativistic case, the off-diagonal perturbation leads to a lifting of the degeneracy in the mass spectrum. In the covariant case, not only do the spectral lines split, but they acquire an imaginary part which is lnear in the applied electric field, thus revealing induced bound state decay in first order perturbation theory. This imaginary part results from the coupling of the external field to the non-compact boost generator. In order to recover the conventional first order Stark splitting, we must include a scalar potential term. This term may be understood as a fifth gauge potential, which compensates for dependence of gauge transformat...
Covariant diagrams for one-loop matching
Zhang, Zhengkang
2016-01-01
We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gauge-covariant quantities and are thus dubbed "covariant diagrams." The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.
Linear response theory for symmetry improved two particle irreducible effective actions
Brown, Michael J.; Whittingham, Ian B.; Kosov, Daniel S.
2016-05-01
We investigate the linear response of an O (N ) scalar quantum field theory subject to external perturbations using the symmetry-improved two-particle irreducible effective action (SI-2PIEA) formalism [A. Pilaftsis and D. Teresi, Nucl. Phys. B874, 594 (2013)]. Despite satisfactory equilibrium behavior, we find a number of unphysical effects at the linear response level. Goldstone boson field fluctuations are overdetermined, with the only consistent solution being to set the fluctuations and their driving sources to zero, except for momentum modes where the Higgs and Goldstone self-energies obey a particular relationship. Also Higgs field fluctuations propagate masslessly, despite the Higgs propagator having the correct mass. These pathologies are independent of any truncation of the effective action and still exist even if we relax the overdetermining Ward identities, so long as the constraint is formulated O (N ) covariantly. We discuss possible reasons for the apparent incompatibility of the constraints and linear response approximation and possible ways forward.
Covariate-free and Covariate-dependent Reliability.
Bentler, Peter M
2016-12-01
Classical test theory reliability coefficients are said to be population specific. Reliability generalization, a meta-analysis method, is the main procedure for evaluating the stability of reliability coefficients across populations. A new approach is developed to evaluate the degree of invariance of reliability coefficients to population characteristics. Factor or common variance of a reliability measure is partitioned into parts that are, and are not, influenced by control variables, resulting in a partition of reliability into a covariate-dependent and a covariate-free part. The approach can be implemented in a single sample and can be applied to a variety of reliability coefficients.
Discrete Symmetries in Covariant LQG
Rovelli, Carlo
2012-01-01
We study time-reversal and parity ---on the physical manifold and in internal space--- in covariant loop gravity. We consider a minor modification of the Holst action which makes it transform coherently under such transformations. The classical theory is not affected but the quantum theory is slightly different. In particular, the simplicity constraints are slightly modified and this restricts orientation flips in a spinfoam to occur only across degenerate regions, thus reducing the sources of potential divergences.
The basics of item response theory using R
Baker, Frank B
2017-01-01
This graduate-level textbook is a tutorial for item response theory that covers both the basics of item response theory and the use of R for preparing graphical presentation in writings about the theory. Item response theory has become one of the most powerful tools used in test construction, yet one of the barriers to learning and applying it is the considerable amount of sophisticated computational effort required to illustrate even the simplest concepts. This text provides the reader access to the basic concepts of item response theory freed of the tedious underlying calculations. It is intended for those who possess limited knowledge of educational measurement and psychometrics. Rather than presenting the full scope of item response theory, this textbook is concise and practical and presents basic concepts without becoming enmeshed in underlying mathematical and computational complexities. Clearly written text and succinct R code allow anyone familiar with statistical concepts to explore and apply item re...
Institute of Scientific and Technical Information of China (English)
Ye Qinghua; Yao Tandong; Chen Feng; Kang Shichang; Zhang Xueqin; Wang Yi
2008-01-01
The study of spatial and temporal covariances of glaciers and lakes would help us to understand the impact of climate change within a basin in Tibet. This study focuses on glacier and lake variations in the Mapam Yumco(玛旁雍错)Basin (covering 7 786.44 km2)by Integrationg series of spatial data from topographic maps and digital satellite images at four different times: 1974, 1990, 1999,and 2003. The results indicate that: (1) decreased lakes, retreated glaciers, enlarged lakes and advanced glaciers co-exist in the basin during the last 30 years; (2) glacier recession was accelerated in recent years due to the warmer climate; (3) lake areas in the basin are both reduced and enlarged by an accelerated speed with more water supplies from speeding melt glaciers or frozen ground in the last three decades.
Fukushima, Kimichika; Sato, Hikaru
2017-07-01
This paper is a review by the authors concerning the construction of a Poincaré covariant (owing to space-time continuum) field-theoretic formalism in terms of step-function-type basis functions without ultraviolet divergences. This formalism analytically derives confinement/deconfinement, mass-gap and Regge trajectory for non-Abelian gauge fields, and gives solutions for self-interacting scalar fields. Fields propagate in space-time continuum and fields with finite degrees of freedom toward continuum limit have no ultraviolet divergence. Basis functions defined in a parameter space-time are mapped to real space-time. The authors derive a new solution comprised of classical fields as vacuum and quantum fluctuations, leading to the linear potential between the particle and antiparticle from the Wilson loop. The Polyakov line gives finite binding energies and reveals the deconfining property at high temperatures. The quantum action yields positive mass from the classical fields and quantum fluctuations produce the Coulomb potential. Pure Yang-Mills fields show the same mass-gap owing to the particle-antiparticle pair creation. The Dirac equation under linear potential is analytically solved in this formalism, reproducing the principal properties of Regge trajectories at a quantum level. Further outlook mentions a possibility of the difference between conventional continuum and present wave functions responsible for the cosmological constant.
On the Origin of Gravitational Lorentz Covariance
Khoury, Justin; Tolley, Andrew J
2013-01-01
We provide evidence that general relativity is the unique spatially covariant effective field theory of the transverse, traceless graviton degrees of freedom. The Lorentz covariance of general relativity, having not been assumed in our analysis, is thus plausibly interpreted as an accidental or emergent symmetry of the gravitational sector.
Multivariate covariance generalized linear models
DEFF Research Database (Denmark)
Bonat, W. H.; Jørgensen, Bent
2016-01-01
We propose a general framework for non-normal multivariate data analysis called multivariate covariance generalized linear models, designed to handle multivariate response variables, along with a wide range of temporal and spatial correlation structures defined in terms of a covariance link...... function combined with a matrix linear predictor involving known matrices. The method is motivated by three data examples that are not easily handled by existing methods. The first example concerns multivariate count data, the second involves response variables of mixed types, combined with repeated...... are fitted by using an efficient Newton scoring algorithm based on quasi-likelihood and Pearson estimating functions, using only second-moment assumptions. This provides a unified approach to a wide variety of types of response variables and covariance structures, including multivariate extensions...
Covariant Macroscopic Quantum Geometry
Hogan, Craig J
2012-01-01
A covariant noncommutative algebra of position operators is presented, and interpreted as the macroscopic limit of a geometry that describes a collective quantum behavior of the positions of massive bodies in a flat emergent space-time. The commutator defines a quantum-geometrical relationship between world lines that depends on their separation and relative velocity, but on no other property of the bodies, and leads to a transverse uncertainty of the geometrical wave function that increases with separation. The number of geometrical degrees of freedom in a space-time volume scales holographically, as the surface area in Planck units. Ongoing branching of the wave function causes fluctuations in transverse position, shared coherently among bodies with similar trajectories. The theory can be tested using appropriately configured Michelson interferometers.
Saltas, Ippocratis D.; Vitagliano, Vincenzo
2017-05-01
We derive the 1-loop effective action of the cubic Galileon coupled to quantum-gravitational fluctuations in a background and gauge-independent manner, employing the covariant framework of DeWitt and Vilkovisky. Although the bare action respects shift symmetry, the coupling to gravity induces an effective mass to the scalar, of the order of the cosmological constant, as a direct result of the nonflat field-space metric, the latter ensuring the field-reparametrization invariance of the formalism. Within a gauge-invariant regularization scheme, we discover novel, gravitationally induced non-Galileon higher-derivative interactions in the effective action. These terms, previously unnoticed within standard, noncovariant frameworks, are not Planck suppressed. Unless tuned to be subdominant, their presence could have important implications for the classical and quantum phenomenology of the theory.
Linear Response Theory for Symmetry Improved Two Particle Irreducible Effective Actions
Brown, Michael J; Kosov, Daniel S
2016-01-01
We investigate the linear response of an O(N) scalar quantum field theory subject to external perturbations using the symmetry improved two particle irreducible effective action formalism [A. Pilaftsis and D. Teresi, Nucl. Phys. B874, 594 (2013)]. Despite satisfactory equilibrium behavior, we find a number of unphysical effects at the linear response level. Goldstone boson field fluctuations are over-determined, with the only consistent solution being to set the fluctuations and their driving sources to zero, except for momentum modes where the Higgs and Goldstone self-energies obey a particular relationship. Also Higgs field fluctuations propagate masslessly, despite the Higgs propagator having the correct mass. These pathologies are independent of any truncation of the effective action and still exist even if we relax the over-determining Ward identities, so long as the constraint is formulated O(N)-covariantly. We discuss possible reasons for the apparent incompatibility of the constraints and linear respo...
debating toynbee's theory of challenge and response
African Journals Online (AJOL)
His interpretation incorporated the “challenge and response” theory of suc- cessive civilisations ... audience to take a more critical view of their legacy of imperialism and ...... rabbi in Bingen, Berlin, and Frankfurt an der Oder during the 1920s.
Reader Response Theory in the High School English Classroom.
Shelton, Karen Yvonne
A study examined the theory concerning reader response and the rationale and practice of reader response in the high school English curriculum. Formal experimental studies existed that explored reader response practices in the high school setting, but no formal studies existed on the questioning practices of potential reader response teachers. A…
Covariant electromagnetic field lines
Hadad, Y.; Cohen, E.; Kaminer, I.; Elitzur, A. C.
2017-08-01
Faraday introduced electric field lines as a powerful tool for understanding the electric force, and these field lines are still used today in classrooms and textbooks teaching the basics of electromagnetism within the electrostatic limit. However, despite attempts at generalizing this concept beyond the electrostatic limit, such a fully relativistic field line theory still appears to be missing. In this work, we propose such a theory and define covariant electromagnetic field lines that naturally extend electric field lines to relativistic systems and general electromagnetic fields. We derive a closed-form formula for the field lines curvature in the vicinity of a charge, and show that it is related to the world line of the charge. This demonstrates how the kinematics of a charge can be derived from the geometry of the electromagnetic field lines. Such a theory may also provide new tools in modeling and analyzing electromagnetic phenomena, and may entail new insights regarding long-standing problems such as radiation-reaction and self-force. In particular, the electromagnetic field lines curvature has the attractive property of being non-singular everywhere, thus eliminating all self-field singularities without using renormalization techniques.
Manifestly covariant electromagnetism
Energy Technology Data Exchange (ETDEWEB)
Hillion, P. [Institut Henri Poincare' , Le Vesinet (France)
1999-03-01
The conventional relativistic formulation of electromagnetism is covariant under the full Lorentz group. But relativity requires covariance only under the proper Lorentz group and the authors present here the formalism covariant under the complex rotation group isomorphic to the proper Lorentz group. The authors discuss successively Maxwell's equations, constitutive relations and potential functions. A comparison is made with the usual formulation.
Covariant diagrams for one-loop matching
Energy Technology Data Exchange (ETDEWEB)
Zhang, Zhengkang [Michigan Univ., Ann Arbor, MI (United States). Michigan Center for Theoretical Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2016-10-15
We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gaugecovariant quantities and are thus dubbed ''covariant diagrams.'' The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.
Quantum energy inequalities and local covariance II: categorical formulation
Fewster, Christopher J.
2007-11-01
We formulate quantum energy inequalities (QEIs) in the framework of locally covariant quantum field theory developed by Brunetti, Fredenhagen and Verch, which is based on notions taken from category theory. This leads to a new viewpoint on the QEIs, and also to the identification of a new structural property of locally covariant quantum field theory, which we call local physical equivalence. Covariant formulations of the numerical range and spectrum of locally covariant fields are given and investigated, and a new algebra of fields is identified, in which fields are treated independently of their realisation on particular spacetimes and manifestly covariant versions of the functional calculus may be formulated.
Reyes, J. J.; Tague, N.; Kruger, C. E.; Johnson, K.; Adam, J. C.
2015-12-01
Grasses in rangeland ecosystems cover a large portion of the contiguous United States and are used to support the production of livestock. These grasslands experience a wide range of precipitation and temperature regimes, as well as management activities like grazing. Assessing the coupled response of biomass to both climatic change and human activities is important to decision makers to ensure the sustainable management of their lands. The objective of this study is to examine the sensitivity of biomass under co-varying conditions of climate and grazing management. For this, we used the Regional Hydro-ecologic Simulation System (RHESSys), a physically-based model that simulates coupled water and biogeochemical processes. We selected representative grassland sites using the Köppen-Geiger climate classification system and information on major grass species. Historical data on precipitation, temperature, and grazing patterns (intensity, frequency, duration) were incrementally perturbed to simulate climatic change and possible changes in management. To visualize this multi-dimensional parameter space, we created surface response plots of varying climate and grazing factors for the mean and variance of both aboveground and belowground biomass, as well as the ratio between the two. Mean biomass generally increased with warmer temperatures and decreased with more intense grazing. The sensitivity of biomass (i.e. variance) increased with more extreme perturbations in climate and intense types of grazing management. However, co-varying climate conditions with either grazing intensity, frequency, or duration revealed different biomass responses and tradeoffs. For example, some changes in grazing duration could be reversed by changes in climate. Effects of high intensity grazing could be buffered depending on the timing of grazing (i.e. start/end date). Using simple perturbations with process-based modeling provides useful information for land managers for future planning.
Genres and Genre Theory: A Response to Michael Rosen
Christie, Frances
2013-01-01
This paper responds to Michael Rosen's blog entries, "How Genre Theory Saved the World", arguing that genre theory in the tradition of systemic functional linguistics (SFL) has made an important contribution to language and literacy pedagogy. It emerged in the Australian context in about 1980 and was initially developed in response to…
Behavioral Theory and Culture Special Issue: Authors' Response to Commentaries
Pasick, Rena J.; Burke, Nancy J.; Joseph, Galen
2009-01-01
This article presents the authors' response to commentaries that focus on the "Behavioral Constructs and Culture in Cancer Screening" (3Cs) study. The 3Cs study had an unremarkable beginning, with two colleagues discussing their frustration over the narrow range of behavioral theories and the limited guidance the theories offered for a study…
Application of multidimensional item response theory models to longitudinal data
Marvelde, te Janneke M.; Glas, Cees A.W.; Van Landeghem, Georges; Van Damme, Jan
2006-01-01
The application of multidimensional item response theory (IRT) models to longitudinal educational surveys where students are repeatedly measured is discussed and exemplified. A marginal maximum likelihood (MML) method to estimate the parameters of a multidimensional generalized partial credit model
Rights and Responsibilities in the Light of Social Contract Theory
La Morte, Michael W.
1977-01-01
Discusses the influence of the social contract on American institutions, due process when liberty and property are involved, the nature of an individual's responsibility to the government, and the application of social contract theory to education. (Author/IRT)
Item response theory modeling with nonignorable missing data
Pimentel, Jonald L.
2005-01-01
This thesis discusses methods to detect nonignorable missing data and methods to adjust for the bias caused by nonignorable missing data, both by introducing a model for the missing data indicator using item response theory (IRT) models.
Culturally Responsive Computing: A Theory Revisited
Scott, Kimberly A.; Sheridan, Kimberly M.; Clark, Kevin
2015-01-01
Despite multiple efforts and considerable funding, historically marginalized groups (e.g., racial minorities and women) continue not to enter or persist in the most lucrative of fields--technology. Understanding the potency of culturally responsive teaching (CRT), some technology-enrichment programs modified CRP principles to establish a…
Holwerda, F.; Alvarado-Barrientos, M. S.
2014-12-01
Field data on evapotranspiration are of crucial importance for ecohydrological and hydrometeorological studies in the tropics. Probably the most direct way to measure evapotranspiration is with the eddy covariance method, in which the latent heat flux (λE) is calculated from turbulent fluctuations of vertical wind velocity and humidity. The humidity fluctuations are typically measured with some type of fast-response infrared hygrometer. However, these sensors are expensive, which can be problematic if research budgets are limited. Turbulent fluctuations of humidity can also be measured with fast-response dry- and wet-bulb thermocouples, which can be constructed easily and at a fraction of the price of infrared sensors. The idea of using dry- and wet-bulb thermocouples for measuring λE with the eddy covariance method is not new, but hasn't been tested recently, possibly because experiments in the late seventies showed that this approach is not without problems due to the slow response of the wet-bulb thermocouple. In the present study, values of λE derived from dry- and wet-bulb thermocouple measurements were compared with those obtained using a fast-response KH20 hygrometer. Measurements were made above a shaded coffee plantation and a sugarcane crop in central Veracruz, Mexico. The agreement between λE obtained with the thermocouples (y) and the hygrometer (x) was very good for both vegetation covers: y = 0.98x + 5.0 (W m-2), r2 = 0.93 (coffee plantation); y = 0.99x - 13.3 (W m-2), r2 = 0.88 (sugarcane). However, the correction factor (CF) for high frequency loss in the wet-bulb temperature signal was considerably higher for the low-statured sugarcane crop (CF = 1.33) as compared to the taller shaded coffee plantation (CF = 1.09). Nevertheless, as long as care is taken in the derivation of this correction factor, reliable λE data can be obtained using the dry- and wet-bulb thermocouples, offering a cheap alternative to infrared hygrometers.
Weir, Kirsty F.; Jose, Paul E.
2008-01-01
This study compares predictions from the Hopelessness Theory of depression (Abramson, Metalsky, & Alloy, 1989) with the Response Styles Theory of depression (RST; Nolen-Hoeksema, 1987) with data obtained from a preadolescent sample (ages 9 to 13 years). Three hundred ten preadolescents completed self-report measures of stress, sense of control,…
Kohli, Nidhi; Koran, Jennifer; Henn, Lisa
2015-01-01
There are well-defined theoretical differences between the classical test theory (CTT) and item response theory (IRT) frameworks. It is understood that in the CTT framework, person and item statistics are test- and sample-dependent. This is not the perception with IRT. For this reason, the IRT framework is considered to be theoretically superior…
Bergshoeff, E.; Pope, C.N.; Stelle, K.S.
1990-01-01
We discuss the notion of higher-spin covariance in w∞ gravity. We show how a recently proposed covariant w∞ gravity action can be obtained from non-chiral w∞ gravity by making field redefinitions that introduce new gauge-field components with corresponding new gauge transformations.
Covariant action for type IIB supergravity
Sen, Ashoke
2016-07-01
Taking clues from the recent construction of the covariant action for type II and heterotic string field theories, we construct a manifestly Lorentz covariant action for type IIB supergravity, and discuss its gauge fixing maintaining manifest Lorentz invariance. The action contains a (non-gravitating) free 4-form field besides the usual fields of type IIB supergravity. This free field, being completely decoupled from the interacting sector, has no physical consequence.
THE RESPONSIBILITY TO PROTECT. A JUST WAR THEORY BASED ANALYSIS
Directory of Open Access Journals (Sweden)
Andreea IANCU
2014-11-01
Full Text Available This paper analyzes the Responsibility to protect principle as the paradigm that reinforces the just war theory in the current international relations. The importance of this analysis is given by the fact that in the current change of source of international conflicts, the Responsibility to protect principle affirms the responsibility of the international community to protect all the citizens of the world. In this context we witness a translation toward a Post-Westphalian international system, which values the individual as a security referent. This article discusses the origins of the responsibility to protect principle and problematizes (discusses the legitimacy of use of violence and force in the current international system. Moreover, the paper analyzes the possible humanization of the current international relations and, simultaneously, the persistency of conflict and warfare in the international system. The conclusion of this research states that the Responsibility to protect principle revises the just war theory by centering it on the individual.
What Information Theory Says about Bounded Rational Best Response
Wolpert, David H.
2005-01-01
Probability Collectives (PC) provides the information-theoretic extension of conventional full-rationality game theory to bounded rational games. Here an explicit solution to the equations giving the bounded rationality equilibrium of a game is presented. Then PC is used to investigate games in which the players use bounded rational best-response strategies. Next it is shown that in the continuum-time limit, bounded rational best response games result in a variant of the replicator dynamics of evolutionary game theory. It is then shown that for team (shared-payoff) games, this variant of replicator dynamics is identical to Newton-Raphson iterative optimization of the shared utility function.
Sorensen, Patrick O.; Germino, Matthew J.; Feris, Kevin P.
2013-01-01
Precipitation amount and seasonal timing determine the duration and distribution of water available for plant and microbial activity in the cold desert sagebrush steppe. In this study, we sought to determine if a sustained shift in the amount and timing of precipitation would affect soil microbial diversity, community composition, and soil carbon (C) storage. Field plots were irrigated (+200 mm) during the dormant or growing-season for 17 years. Microbial community responses were assessed over the course of a year at two depths (15–20 cm, 95–100 cm) by terminal restriction fragment length polymorphism (T-RFLP), along with co-occurring changes in plant cover and edaphic properties. Bacterial richness, Shannon Weaver diversity, and composition in shallow soils (15–20 cm) as well as evenness in deep soils (95–100 cm) differed across irrigation treatments during July. Irrigation timing affected fungal community diversity and community composition during the dormant season and most strongly in deep soils (95–100 cm). Dormant-season irrigation increased the ratio of shrubs to forbs and reduced soil C in shallow soils by 16% relative to ambient conditions. It is unclear whether or not soil C will continue to decline with continued treatment application or if microbial adaptation could mitigate sustained soil C losses. Future changes in precipitation timing will affect soil microbes in a seasonally dependent manner and be coupled to co-varying effects of water content on vegetation and soil C.
Readers' Readings: Applications of Reader-Response Theory.
Steiner, Linda
In the interest of applying reader response theory to journalism this paper posits that readers of newspapers, like readers of literature, take an active role in making meaning from the articles they read, rather than passively accepting news as a finished, static product. Additionally, it proposes that journalism textbooks pay little attention to…
Reader-Response Theory and the English Curriculum.
Probst, Robert E.
1994-01-01
Describes the affinities between reader response theory and the proper objectives of English instruction. Describes students not as potential literary scholars but as curious people needing personal experiences with reading and writing. Outlines a model for teaching literature focused on this conception. (HB)
Multilevel Higher-Order Item Response Theory Models
Huang, Hung-Yu; Wang, Wen-Chung
2014-01-01
In the social sciences, latent traits often have a hierarchical structure, and data can be sampled from multiple levels. Both hierarchical latent traits and multilevel data can occur simultaneously. In this study, we developed a general class of item response theory models to accommodate both hierarchical latent traits and multilevel data. The…
Characterizing Sources of Uncertainty in Item Response Theory Scale Scores
Yang, Ji Seung; Hansen, Mark; Cai, Li
2012-01-01
Traditional estimators of item response theory scale scores ignore uncertainty carried over from the item calibration process, which can lead to incorrect estimates of the standard errors of measurement (SEMs). Here, the authors review a variety of approaches that have been applied to this problem and compare them on the basis of their statistical…
A short tutorial on item response theory in rheumatology
Siemons, L.; Krishnan, E.
2014-01-01
OBJECTIVES: The aim is to familiarise physicians and researchers with the most important concepts of item response theory (IRT) and with its usefulness for improving test administration and data collection in health care. Special attention is given to the versatility of its use within the rheumatic
Using SAS PROC MCMC for Item Response Theory Models
Ames, Allison J.; Samonte, Kelli
2015-01-01
Interest in using Bayesian methods for estimating item response theory models has grown at a remarkable rate in recent years. This attentiveness to Bayesian estimation has also inspired a growth in available software such as WinBUGS, R packages, BMIRT, MPLUS, and SAS PROC MCMC. This article intends to provide an accessible overview of Bayesian…
Linear-response thermal time-dependent density functional theory
Pribram-Jones, Aurora; Burke, Kieron
2015-01-01
The van Leeuwen proof of linear-response time-dependent density functional theory (TDDFT) is generalized to thermal ensembles. This allows generalization to finite temperatures of the Gross-Kohn relation, the exchange-correlation kernel of TDDFT, and fluctuation dissipation theorem for DFT. This produces a natural method for generating new thermal exchange-correlation (XC) approximations.
Linear response theory for magnon transport in ferromagnetic insulators
Murakami, Shuichi; Matsumoto, Ryo
2012-02-01
We study transverse response of magnons in ferromagnetic insulators within linear response theory. In analogy with the corresponding theory for electrons [1], magnon transverse response is described, including the Hall effect, Nernst effect, and thermal Hall effect. As is also the case for electrons [1], the response functions for magnons consist of the Kubo-formula term, and the term corresponding to the orbital angular momentum. We can rewrite the response functions in terms of the Berry curvature in momentum space [2]. We apply this theory to the (quantum-mechanical) magnons and to the classical magnetostatic waves. For the magnetostatic waves, the eigenmodes are given by a generalized eigenvalue problem, giving rise to the special form of the Berry curvature [2]. We explain various properties of this Berry curvature for the generalized eigenvalue problem, and discuss its implications for the physical properties of magnetostatic modes. [1] L. Smrcka and P. Streda, J. Phys. C, 10, 2153 (1977); H. Oji, P. Streda, Phys. Rev. B 31, 7291 (1985); [2] R. Matsumoto and S. Murakami, Phys. Rev. Lett. 106, 197202 (2011); Phys. Rev. B 84, 184406 (2011).
Open-ended response theory with polarizable embedding
DEFF Research Database (Denmark)
Steindal, Arnfinn Hykkerud; Beerepoot, Maarten T P; Ringholm, Magnus
2016-01-01
We present the theory and implementation of an open-ended framework for electric response properties at the level of Hartree-Fock and Kohn-Sham density functional theory that includes effects from the molecular environment modeled by the polarizable embedding (PE) model. With this new state......-of-the-art multiscale functionality, electric response properties to any order can be calculated for molecules embedded in polarizable atomistic molecular environments ranging from solvents to complex heterogeneous macromolecules such as proteins. In addition, environmental effects on multiphoton absorption (MPA......) properties can be studied by evaluating single residues of the response functions. The PE approach includes mutual polarization effects between the quantum and classical parts of the system through induced dipoles that are determined self-consistently with respect to the electronic density. The applicability...
Ranger, Jochen; Kuhn, Jörg-Tobias; Szardenings, Carsten
2016-05-01
Psychological tests are usually analysed with item response models. Recently, some alternative measurement models have been proposed that were derived from cognitive process models developed in experimental psychology. These models consider the responses but also the response times of the test takers. Two such models are the Q-diffusion model and the D-diffusion model. Both models can be calibrated with the diffIRT package of the R statistical environment via marginal maximum likelihood (MML) estimation. In this manuscript, an alternative approach to model calibration is proposed. The approach is based on weighted least squares estimation and parallels the standard estimation approach in structural equation modelling. Estimates are determined by minimizing the discrepancy between the observed and the implied covariance matrix. The estimator is simple to implement, consistent, and asymptotically normally distributed. Least squares estimation also provides a test of model fit by comparing the observed and implied covariance matrix. The estimator and the test of model fit are evaluated in a simulation study. Although parameter recovery is good, the estimator is less efficient than the MML estimator.
Newton law in covariant unimodular $F(R)$ gravity
Nojiri, S; Oikonomou, V K
2016-01-01
We propose a covariant ghost-free unimodular $F(R)$ gravity theory, which contains a three-form field and study its structure using the analogy of the proposed theory with a quantum system which describes a charged particle in uniform magnetic field. Newton's law in non-covariant unimodular $F(R)$ gravity as well as in unimodular Einstein gravity is derived and it is shown to be just the same as in General Relativity. The derivation of Newton's law in covariant unimodular $F(R)$ gravity shows that it is modified precisely in the same way as in the ordinary $F(R)$ theory. We also demonstrate that the cosmology of a Friedmann-Robertson-Walker background, is equivalent in the non-covariant and covariant formulations of unimodular $F(R)$ theory.
Frasinski, Leszek J.
2016-08-01
Recent technological advances in the generation of intense femtosecond pulses have made covariance mapping an attractive analytical technique. The laser pulses available are so intense that often thousands of ionisation and Coulomb explosion events will occur within each pulse. To understand the physics of these processes the photoelectrons and photoions need to be correlated, and covariance mapping is well suited for operating at the high counting rates of these laser sources. Partial covariance is particularly useful in experiments with x-ray free electron lasers, because it is capable of suppressing pulse fluctuation effects. A variety of covariance mapping methods is described: simple, partial (single- and multi-parameter), sliced, contingent and multi-dimensional. The relationship to coincidence techniques is discussed. Covariance mapping has been used in many areas of science and technology: inner-shell excitation and Auger decay, multiphoton and multielectron ionisation, time-of-flight and angle-resolved spectrometry, infrared spectroscopy, nuclear magnetic resonance imaging, stimulated Raman scattering, directional gamma ray sensing, welding diagnostics and brain connectivity studies (connectomics). This review gives practical advice for implementing the technique and interpreting the results, including its limitations and instrumental constraints. It also summarises recent theoretical studies, highlights unsolved problems and outlines a personal view on the most promising research directions.
Covariant Bardeen perturbation formalism
Vitenti, S. D. P.; Falciano, F. T.; Pinto-Neto, N.
2014-05-01
In a previous work we obtained a set of necessary conditions for the linear approximation in cosmology. Here we discuss the relations of this approach with the so-called covariant perturbations. It is often argued in the literature that one of the main advantages of the covariant approach to describe cosmological perturbations is that the Bardeen formalism is coordinate dependent. In this paper we will reformulate the Bardeen approach in a completely covariant manner. For that, we introduce the notion of pure and mixed tensors, which yields an adequate language to treat both perturbative approaches in a common framework. We then stress that in the referred covariant approach, one necessarily introduces an additional hypersurface choice to the problem. Using our mixed and pure tensors approach, we are able to construct a one-to-one map relating the usual gauge dependence of the Bardeen formalism with the hypersurface dependence inherent to the covariant approach. Finally, through the use of this map, we define full nonlinear tensors that at first order correspond to the three known gauge invariant variables Φ, Ψ and Ξ, which are simultaneously foliation and gauge invariant. We then stress that the use of the proposed mixed tensors allows one to construct simultaneously gauge and hypersurface invariant variables at any order.
Raykov, Tenko; Marcoulides, George A.
2016-01-01
The frequently neglected and often misunderstood relationship between classical test theory and item response theory is discussed for the unidimensional case with binary measures and no guessing. It is pointed out that popular item response models can be directly obtained from classical test theory-based models by accounting for the discrete…
DEFF Research Database (Denmark)
Barndorff-Nielsen, Ole Eiler; Shephard, N.
2004-01-01
This paper analyses multivariate high frequency financial data using realized covariation. We provide a new asymptotic distribution theory for standard methods such as regression, correlation analysis, and covariance. It will be based on a fixed interval of time (e.g., a day or week), allowing...... the number of high frequency returns during this period to go to infinity. Our analysis allows us to study how high frequency correlations, regressions, and covariances change through time. In particular we provide confidence intervals for each of these quantities....
Phenotypic covariance at species’ borders
2013-01-01
Background Understanding the evolution of species limits is important in ecology, evolution, and conservation biology. Despite its likely importance in the evolution of these limits, little is known about phenotypic covariance in geographically marginal populations, and the degree to which it constrains, or facilitates, responses to selection. We investigated phenotypic covariance in morphological traits at species’ borders by comparing phenotypic covariance matrices (P), including the degree of shared structure, the distribution of strengths of pair-wise correlations between traits, the degree of morphological integration of traits, and the ranks of matricies, between central and marginal populations of three species-pairs of coral reef fishes. Results Greater structural differences in P were observed between populations close to range margins and conspecific populations toward range centres, than between pairs of conspecific populations that were both more centrally located within their ranges. Approximately 80% of all pair-wise trait correlations within populations were greater in the north, but these differences were unrelated to the position of the sampled population with respect to the geographic range of the species. Conclusions Neither the degree of morphological integration, nor ranks of P, indicated greater evolutionary constraint at range edges. Characteristics of P observed here provide no support for constraint contributing to the formation of these species’ borders, but may instead reflect structural change in P caused by selection or drift, and their potential to evolve in the future. PMID:23714580
Covariance Applications with Kiwi
Mattoon, C. M.; Brown, D.; Elliott, J. B.
2012-05-01
The Computational Nuclear Physics group at Lawrence Livermore National Laboratory (LLNL) is developing a new tool, named `Kiwi', that is intended as an interface between the covariance data increasingly available in major nuclear reaction libraries (including ENDF and ENDL) and large-scale Uncertainty Quantification (UQ) studies. Kiwi is designed to integrate smoothly into large UQ studies, using the covariance matrix to generate multiple variations of nuclear data. The code has been tested using critical assemblies as a test case, and is being integrated into LLNL's quality assurance and benchmarking for nuclear data.
Covariance Applications with Kiwi
Directory of Open Access Journals (Sweden)
Elliott J.B.
2012-05-01
Full Text Available The Computational Nuclear Physics group at Lawrence Livermore National Laboratory (LLNL is developing a new tool, named ‘Kiwi’, that is intended as an interface between the covariance data increasingly available in major nuclear reaction libraries (including ENDF and ENDL and large-scale Uncertainty Quantification (UQ studies. Kiwi is designed to integrate smoothly into large UQ studies, using the covariance matrix to generate multiple variations of nuclear data. The code has been tested using critical assemblies as a test case, and is being integrated into LLNL's quality assurance and benchmarking for nuclear data.
Modeling size effect in the SMA response: a gradient theory
Tabesh, Majid; Boyd, James G.; Lagoudas, Dimitris C.
2014-03-01
Shape memory alloys (SMAs) show size effect in their response. The critical stresses, for instance, for the start of martensite and austenite transformations are reported to increase in some SMA wires for diameters below 100 μm. Simulation of such a behavior cannot be achieved using conventional theories that lack an intrinsic length scale in their constitutive modeling. To enable the size effect, a thermodynamically consistent constitutive model is developed, that in addition to conventional internal variables of martensitic volume fraction and transformation strain, contains the spatial gradient of martensitic volume fraction as an internal variable. The developed theory is simplified for 1D cases and analytical solutions for pure bending of SMA beams are presented. The gradient model captures the size effect in the response of the studied SMA structures.
Ramsay-Curve Item Response Theory for the Three-Parameter Logistic Item Response Model
Woods, Carol M.
2008-01-01
In Ramsay-curve item response theory (RC-IRT), the latent variable distribution is estimated simultaneously with the item parameters of a unidimensional item response model using marginal maximum likelihood estimation. This study evaluates RC-IRT for the three-parameter logistic (3PL) model with comparisons to the normal model and to the empirical…
The response set theory of hypnosis: expectancy and physiology.
Kirsch, I
2001-07-01
A recent exposition of the response set theory of hypnosis (Kirsch, 2000) contained incorrect and misleading figures. The correct figures illustrated a complementary relation between mental and physiological phenomena. The figures as published erroneously suggested that the author espoused epiphenomenalism. As shown in this corrected version, Kirsch proposes that mind states and body states be considered as two ways of viewing a single psychophysiological phenomenon.
Covariance of the selfdual vector model
2004-01-01
The Poisson algebra between the fields involved in the vectorial selfdual action is obtained by means of the reduced action. The conserved charges associated with the invariance under the inhomogeneous Lorentz group are obtained and its action on the fields. The covariance of the theory is proved using the Schwinger-Dirac algebra. The spin of the excitations is discussed.
Lucarini, Valerio
2010-05-01
We consider the general response theory recently proposed by Ruelle for describing the impact of small perturbations to the non-equilibrium steady states resulting from Axiom A dynamical systems. We show that the causality of the response functions entails the possibility of writing a set of Kramers-Kronig (K-K) relations for the corresponding susceptibilities at all orders of nonlinearity, and specific results are provided for the case of arbitrary order harmonic response. These results shed light on the very general impact of considering the principle of causality for testing self-consistency: the described dispersion relations constitute unavoidable benchmarks that any experimental and model generated dataset must obey. These results, taking into account the chaotic hypothesis by Gallavotti and Cohen, might be relevant in several fields, including climate research. In particular, whereas the fluctuation-dissipation theorem does not work for non-equilibrium systems, because of the non-equivalence between internal and external fluctuations, K-K relations might be robust tools for the definition of a self-consistent theory of climate change. Along these lines, we present here the first evidence of the validity of these integral relations for the linear and the second harmonic response for the perturbed Lorenz 63 system, by showing that numerical simulations agree up to high degree of accuracy with the theoretical predictions. The numerical results confirm the conceptual validity of the nonlinear response theory, suggest that the theory can be extended for more general non equilibrium steady state systems, and shed new light on the applicability of very general tools, based only upon the principle of causality, for diagnosing the behavior of perturbed chaotic systems and reconstructing their output signals.
Generalized Linear Covariance Analysis
Carpenter, James R.; Markley, F. Landis
2014-01-01
This talk presents a comprehensive approach to filter modeling for generalized covariance analysis of both batch least-squares and sequential estimators. We review and extend in two directions the results of prior work that allowed for partitioning of the state space into solve-for'' and consider'' parameters, accounted for differences between the formal values and the true values of the measurement noise, process noise, and textita priori solve-for and consider covariances, and explicitly partitioned the errors into subspaces containing only the influence of the measurement noise, process noise, and solve-for and consider covariances. In this work, we explicitly add sensitivity analysis to this prior work, and relax an implicit assumption that the batch estimator's epoch time occurs prior to the definitive span. We also apply the method to an integrated orbit and attitude problem, in which gyro and accelerometer errors, though not estimated, influence the orbit determination performance. We illustrate our results using two graphical presentations, which we call the variance sandpile'' and the sensitivity mosaic,'' and we compare the linear covariance results to confidence intervals associated with ensemble statistics from a Monte Carlo analysis.
Chi, Zhiyi
2010-01-01
Two extensions of generalized linear models are considered. In the first one, response variables depend on multiple linear combinations of covariates. In the second one, only response variables are observed while the linear covariates are missing. We derive stochastic Lipschitz continuity results for the loss functions involved in the regression problems and apply them to get bounds on estimation error for Lasso. Multivariate comparison results on Rademacher complexity are obtained as tools to establish the stochastic Lipschitz continuity results.
Hui, Yi; Law, Siu Seong; Ku, Chiu Jen
2017-02-01
Covariance of the auto/cross-covariance matrix based method is studied for the damage identification of a structure with illustrations on its advantages and limitations. The original method is extended for structures under direct white noise excitations. The auto/cross-covariance function of the measured acceleration and its corresponding derivatives are formulated analytically, and the method is modified in two new strategies to enable successful identification with much fewer sensors. Numerical examples are adopted to illustrate the improved method, and the effects of sampling frequency and sampling duration are discussed. Results show that the covariance of covariance calculated from responses of higher order modes of a structure play an important role to the accurate identification of local damage in a structure.
Differential sensitivity theory applied to movement of maxima responses. [LMFBR
Energy Technology Data Exchange (ETDEWEB)
Maudlin, P.J.; Parks, C.V.; Cacuci, D.G.
1981-01-01
Differential sensitivity theory (DST) is a recently developed methodology to evaluate response derivatives dR/d..cap alpha.. by using adjoint functions which correspond to the differentiated (with respect to an arbitrary parameter ..cap alpha..) linear or nonlinear physical system of equations. However, for many problems, where responses of importance are local maxima such as peak temperature, power, or heat flux, changes in the phase space location of the peak itself are of interest. This summary will present the DST procedure for predicting phase space shifts of maxima responses as applied to the MELT-III fast reactor safety code. An FFTF protected transient involving a $.23/s ramp reactivity insertion with scram on high power was selected for investigation.
Cultural Consensus Theory: Aggregating Continuous Responses in a Finite Interval
Batchelder, William H.; Strashny, Alex; Romney, A. Kimball
Cultural consensus theory (CCT) consists of cognitive models for aggregating responses of "informants" to test items about some domain of their shared cultural knowledge. This paper develops a CCT model for items requiring bounded numerical responses, e.g. probability estimates, confidence judgments, or similarity judgments. The model assumes that each item generates a latent random representation in each informant, with mean equal to the consensus answer and variance depending jointly on the informant and the location of the consensus answer. The manifest responses may reflect biases of the informants. Markov Chain Monte Carlo (MCMC) methods were used to estimate the model, and simulation studies validated the approach. The model was applied to an existing cross-cultural dataset involving native Japanese and English speakers judging the similarity of emotion terms. The results sharpened earlier studies that showed that both cultures appear to have very similar cognitive representations of emotion terms.
A pure S-wave covariant model for the nucleon
Gross, F; Peña, M T; Gross, Franz
2006-01-01
Using the manifestly covariant spectator theory, and modeling the nucleon as a system of three constituent quarks with their own electromagnetic structure, we show that all four nucleon electromagnetic form factors can be very well described by a manifestly covariant nucleon wave function with zero orbital angular momentum.
On the Validity of Covariate Adjustment for Estimating Causal Effects
Shpitser, Ilya; Robins, James M
2012-01-01
Identifying effects of actions (treatments) on outcome variables from observational data and causal assumptions is a fundamental problem in causal inference. This identification is made difficult by the presence of confounders which can be related to both treatment and outcome variables. Confounders are often handled, both in theory and in practice, by adjusting for covariates, in other words considering outcomes conditioned on treatment and covariate values, weighed by probability of observing those covariate values. In this paper, we give a complete graphical criterion for covariate adjustment, which we term the adjustment criterion, and derive some interesting corollaries of the completeness of this criterion.
Janes, Holly; Pepe, Margaret S
2009-06-01
Recent scientific and technological innovations have produced an abundance of potential markers that are being investigated for their use in disease screening and diagnosis. In evaluating these markers, it is often necessary to account for covariates associated with the marker of interest. Covariates may include subject characteristics, expertise of the test operator, test procedures or aspects of specimen handling. In this paper, we propose the covariate-adjusted receiver operating characteristic curve, a measure of covariate-adjusted classification accuracy. Nonparametric and semiparametric estimators are proposed, asymptotic distribution theory is provided and finite sample performance is investigated. For illustration we characterize the age-adjusted discriminatory accuracy of prostate-specific antigen as a biomarker for prostate cancer.
Covariant approximation averaging
Shintani, Eigo; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph
2014-01-01
We present a new class of statistical error reduction techniques for Monte-Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in $N_f=2+1$ lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte-Carlo calculations over conventional methods for the same cost.
Using Analysis of Covariance (ANCOVA) with Fallible Covariates
Culpepper, Steven Andrew; Aguinis, Herman
2011-01-01
Analysis of covariance (ANCOVA) is used widely in psychological research implementing nonexperimental designs. However, when covariates are fallible (i.e., measured with error), which is the norm, researchers must choose from among 3 inadequate courses of action: (a) know that the assumption that covariates are perfectly reliable is violated but…
Using Analysis of Covariance (ANCOVA) with Fallible Covariates
Culpepper, Steven Andrew; Aguinis, Herman
2011-01-01
Analysis of covariance (ANCOVA) is used widely in psychological research implementing nonexperimental designs. However, when covariates are fallible (i.e., measured with error), which is the norm, researchers must choose from among 3 inadequate courses of action: (a) know that the assumption that covariates are perfectly reliable is violated but…
Fiorentini, M A L Capri D; Mintz, B W; Palhares, L F; Sorella, S P
2016-01-01
We address the issue of the renormalizability of the gauge-invariant non-local dimension-two operator $A^2_{\\rm min}$, whose minimization is defined along the gauge orbit. Despite its non-local character, we show that the operator $A^2_{\\rm min}$ can be cast in local form through the introduction of an auxiliary Stueckelberg field. The localization procedure gives rise to an unconventional kind of Stueckelberg-type action which turns out to be renormalizable to all orders of perturbation theory. In particular, as a consequence of its gauge invariance, the anomalous dimension of the operator $A^2_{\\rm min}$ turns out to be independent from the gauge parameter $\\alpha$ entering the gauge-fixing condition, being thus given by the anomalous dimension of the operator $A^2$ in the Landau gauge.
PENGEMBANGAN TES BERPIKIR KRITIS DENGAN PENDEKATAN ITEM RESPONSE THEORY
Directory of Open Access Journals (Sweden)
Fajrianthi Fajrianthi
2016-06-01
Full Text Available Penelitian ini bertujuan untuk menghasilkan sebuah alat ukur (tes berpikir kritis yang valid dan reliabel untuk digunakan, baik dalam lingkup pendidikan maupun kerja di Indonesia. Tahapan penelitian dilakukan berdasarkan tahap pengembangan tes menurut Hambleton dan Jones (1993. Kisi-kisi dan pembuatan butir didasarkan pada konsep dalam tes Watson-Glaser Critical Thinking Appraisal (WGCTA. Pada WGCTA, berpikir kritis terdiri dari lima dimensi yaitu Inference, Recognition Assumption, Deduction, Interpretation dan Evaluation of arguments. Uji coba tes dilakukan pada 1.453 peserta tes seleksi karyawan di Surabaya, Gresik, Tuban, Bojonegoro, Rembang. Data dikotomi dianalisis dengan menggunakan model IRT dengan dua parameter yaitu daya beda dan tingkat kesulitan butir. Analisis dilakukan dengan menggunakan program statistik Mplus versi 6.11 Sebelum melakukan analisis dengan IRT, dilakukan pengujian asumsi yaitu uji unidimensionalitas, independensi lokal dan Item Characteristic Curve (ICC. Hasil analisis terhadap 68 butir menghasilkan 15 butir dengan daya beda yang cukup baik dan tingkat kesulitan butir yang berkisar antara –4 sampai dengan 2.448. Sedikitnya jumlah butir yang berkualitas baik disebabkan oleh kelemahan dalam menentukan subject matter experts di bidang berpikir kritis dan pemilihan metode skoring. Kata kunci: Pengembangan tes, berpikir kritis, item response theory DEVELOPING CRITICAL THINKING TEST UTILISING ITEM RESPONSE THEORY Abstract The present study was aimed to develop a valid and reliable instrument in assesing critical thinking which can be implemented both in educational and work settings in Indonesia. Following the Hambleton and Jones’s (1993 procedures on test development, the study developed the instrument by employing the concept of critical thinking from Watson-Glaser Critical Thinking Appraisal (WGCTA. The study included five dimensions of critical thinking as adopted from the WGCTA: Inference, Recognition
Many-Body Theory of the Electroweak Nuclear Response
Benhar, Omar
2008-01-01
After a brief review of the theoretical description of nuclei based on nonrelativistic many-body theory and realistic hamiltonians, these lectures focus on its application to the analysis of the electroweak response. Special emphasis is given to electron-nucleus scattering, whose experimental study has provided a wealth of information on nuclear structure and dynamics, exposing the limitations of the shell model. The extension of the formalism to the case of neutrino-nucleus interactions, whose quantitative understanding is required to reduce the systematic uncertainty of neutrino oscillation experiments, is also discussed.
An item response theory analysis of the narcissistic personality inventory.
Ackerman, Robert A; Donnellan, M Brent; Robins, Richard W
2012-01-01
This research uses item response theory methods to evaluate the Narcissistic Personality Inventory (NPI; Raskin & Terry, 1988). Analyses using the 2-parameter logistic model were conducted on the total score and the Corry, Merritt, Mrug, and Pamp (2008) and Ackerman et al. (2011) subscales for the NPI. In addition to offering precise information about the psychometric properties of the NPI item pool, these analyses generated insights that can be used to develop new measures of the personality constructs embedded within this frequently used inventory.
Covariant Quantum Gravity with Continuous Quantum Geometry I: Covariant Hamiltonian Framework
Pilc, Marián
2016-01-01
The first part of the series is devoted to the formulation of the Einstein-Cartan Theory within the covariant hamiltonian framework. In the first section the general multisymplectic approach is revised and the notion of the d-jet bundles is introduced. Since the whole Standard Model Lagrangian (including gravity) can be written as the functional of the forms, the structure of the d-jet bundles is more appropriate for the covariant hamiltonian analysis than the standard jet bundle approach. The definition of the local covariant Poisson bracket on the space of covariant observables is recalled. The main goal of the work is to show that the gauge group of the Einstein-Cartan theory is given by the semidirect product of the local Lorentz group and the group of spacetime diffeomorphisms. Vanishing of the integral generators of the gauge group is equivalent to equations of motion of the Einstein-Cartan theory and the local covariant algebra generated by Noether's currents is closed Lie algebra.
Analyzing Force Concept Inventory with Item Response Theory
Wang, Jing
2010-01-01
Item Response Theory (IRT) is a popular assessment method used in education measurement, which builds on an assumption of a probability framework connecting students' innate ability and their actual performances on test items. The model transforms students' raw test scores through a nonlinear regression process into a scaled proficiency rating, which can be used to compare results obtained with different test questions. IRT also provides a theoretical approach to address ceiling effect and guessing. We applied IRT to analyze the Force Concept Inventory (FCI). The data was collected from 2802 students taking intro level mechanics courses at The Ohio State University. The data was analyzed with a 3-parameter item response model for multiple choice questions. We describe the procedures of the analysis and discuss the results and the interpretations. The analysis outcomes are compiled to provide a detailed IRT measurement metric of the FCI, which can be easily referenced and used by teachers and researchers for a...
Linear response theory an analytic-algebraic approach
De Nittis, Giuseppe
2017-01-01
This book presents a modern and systematic approach to Linear Response Theory (LRT) by combining analytic and algebraic ideas. LRT is a tool to study systems that are driven out of equilibrium by external perturbations. In particular the reader is provided with a new and robust tool to implement LRT for a wide array of systems. The proposed formalism in fact applies to periodic and random systems in the discrete and the continuum. After a short introduction describing the structure of the book, its aim and motivation, the basic elements of the theory are presented in chapter 2. The mathematical framework of the theory is outlined in chapters 3–5: the relevant von Neumann algebras, noncommutative $L^p$- and Sobolev spaces are introduced; their construction is then made explicit for common physical systems; the notion of isopectral perturbations and the associated dynamics are studied. Chapter 6 is dedicated to the main results, proofs of the Kubo and Kubo-Streda formulas. The book closes with a chapter about...
Haberman, Shelby J; Sinharay, Sandip; Chon, Kyong Hee
2013-07-01
Residual analysis (e.g. Hambleton & Swaminathan, Item response theory: principles and applications, Kluwer Academic, Boston, 1985; Hambleton, Swaminathan, & Rogers, Fundamentals of item response theory, Sage, Newbury Park, 1991) is a popular method to assess fit of item response theory (IRT) models. We suggest a form of residual analysis that may be applied to assess item fit for unidimensional IRT models. The residual analysis consists of a comparison of the maximum-likelihood estimate of the item characteristic curve with an alternative ratio estimate of the item characteristic curve. The large sample distribution of the residual is proved to be standardized normal when the IRT model fits the data. We compare the performance of our suggested residual to the standardized residual of Hambleton et al. (Fundamentals of item response theory, Sage, Newbury Park, 1991) in a detailed simulation study. We then calculate our suggested residuals using data from an operational test. The residuals appear to be useful in assessing the item fit for unidimensional IRT models.
Boxer, Paul; Schappell, Ashley; Middlemass, Keesha; Mercado, Ignacio
2011-01-01
In this study, formerly incarcerated men (N = 123) were assessed for their experiences with violence in the community as well as their current behavioral and mental health status (antisocial behavior and emotional distress). Participants also completed measures of two constructs theorized to moderate relations between exposure to violence and outcomes: cognitive beliefs supporting aggressive responding and negative emotional reactivity to witnessed violence. Data on key social-demographic background factors affecting outcomes were also collected. Analyses showed that, after controlling the effects of background factors, relationships between experiences with violence in the community and behavioral/mental health were moderated by cognitive beliefs and emotional reactivity. At high levels of support for aggressive responding, significant positive links were observed between exposure to violence and antisocial behavior as well as emotional distress. At high levels of negative reactivity to violence, a significant positive link was observed between exposure to violence and emotional distress (but not antisocial behavior). Findings are discussed with respect to research and theory on the effects of exposure to violence in high-risk adult populations. © 2011 Wiley-Liss, Inc.
Dynamical theory of active cellular response to external stress
de, Rumi; Safran, Samuel A.
2008-09-01
We present a comprehensive, theoretical treatment of the orientational response to external stress of active, contractile cells embedded in a gel-like elastic medium. The theory includes both the forces that arise from the deformation of the matrix as well as forces due to the internal regulation of the stress fibers and focal adhesions of the cell. We calculate the time-dependent response of both the magnitude and the direction of the elastic dipole that characterizes the active forces exerted by the cell, for various situations. For static or quasistatic external stress, cells orient parallel to the stress while for high frequency dynamic external stress, cells orient nearly perpendicular. Both numerical and analytical calculations of these effects are presented. In addition we predict the relaxation time for the cellular response for both slowly and rapidly varying external stresses; several characteristic scaling regimes for the relaxation time as a function of applied frequency are predicted. We also treat the case of cells for which the regulation of the stress fibers and focal adhesions is controlled by strain (instead of stress) and show that the predicted dependence of the cellular orientation on the Poisson ratio of the matrix can differentiate strain vs stress regulation of cellular response.
Dynamical theory of active cellular response to external stress.
De, Rumi; Safran, Samuel A
2008-09-01
We present a comprehensive, theoretical treatment of the orientational response to external stress of active, contractile cells embedded in a gel-like elastic medium. The theory includes both the forces that arise from the deformation of the matrix as well as forces due to the internal regulation of the stress fibers and focal adhesions of the cell. We calculate the time-dependent response of both the magnitude and the direction of the elastic dipole that characterizes the active forces exerted by the cell, for various situations. For static or quasistatic external stress, cells orient parallel to the stress while for high frequency dynamic external stress, cells orient nearly perpendicular. Both numerical and analytical calculations of these effects are presented. In addition we predict the relaxation time for the cellular response for both slowly and rapidly varying external stresses; several characteristic scaling regimes for the relaxation time as a function of applied frequency are predicted. We also treat the case of cells for which the regulation of the stress fibers and focal adhesions is controlled by strain (instead of stress) and show that the predicted dependence of the cellular orientation on the Poisson ratio of the matrix can differentiate strain vs stress regulation of cellular response.
Covariant Magnetic Connection Hypersurfaces
Pegoraro, F
2016-01-01
In the single fluid, nonrelativistic, ideal-Magnetohydrodynamic (MHD) plasma description magnetic field lines play a fundamental role by defining dynamically preserved "magnetic connections" between plasma elements. Here we show how the concept of magnetic connection needs to be generalized in the case of a relativistic MHD description where we require covariance under arbitrary Lorentz transformations. This is performed by defining 2-D {\\it magnetic connection hypersurfaces} in the 4-D Minkowski space. This generalization accounts for the loss of simultaneity between spatially separated events in different frames and is expected to provide a powerful insight into the 4-D geometry of electromagnetic fields when ${\\bf E} \\cdot {\\bf B} = 0$.
Universality of Covariance Matrices
Pillai, Natesh S
2011-01-01
We prove the universality of covariance matrices of the form $H_{N \\times N} = {1 \\over N} \\tp{X}X$ where $[X]_{M \\times N}$ is a rectangular matrix with independent real valued entries $[x_{ij}]$ satisfying $\\E \\,x_{ij} = 0$ and $\\E \\,x^2_{ij} = {1 \\over M}$, $N, M\\to \\infty$. Furthermore it is assumed that these entries have sub-exponential tails. We will study the asymptotics in the regime $N/M = d_N \\in (0,\\infty), \\lim_{N\\to \\infty}d_N \
Earth Observing System Covariance Realism
Zaidi, Waqar H.; Hejduk, Matthew D.
2016-01-01
The purpose of covariance realism is to properly size a primary object's covariance in order to add validity to the calculation of the probability of collision. The covariance realism technique in this paper consists of three parts: collection/calculation of definitive state estimates through orbit determination, calculation of covariance realism test statistics at each covariance propagation point, and proper assessment of those test statistics. An empirical cumulative distribution function (ECDF) Goodness-of-Fit (GOF) method is employed to determine if a covariance is properly sized by comparing the empirical distribution of Mahalanobis distance calculations to the hypothesized parent 3-DoF chi-squared distribution. To realistically size a covariance for collision probability calculations, this study uses a state noise compensation algorithm that adds process noise to the definitive epoch covariance to account for uncertainty in the force model. Process noise is added until the GOF tests pass a group significance level threshold. The results of this study indicate that when outliers attributed to persistently high or extreme levels of solar activity are removed, the aforementioned covariance realism compensation method produces a tuned covariance with up to 80 to 90% of the covariance propagation timespan passing (against a 60% minimum passing threshold) the GOF tests-a quite satisfactory and useful result.
Introduction to bifactor polytomous item response theory analysis.
Toland, Michael D; Sulis, Isabella; Giambona, Francesca; Porcu, Mariano; Campbell, Jonathan M
2017-02-01
A bifactor item response theory model can be used to aid in the interpretation of the dimensionality of a multifaceted questionnaire that assumes continuous latent variables underlying the propensity to respond to items. This model can be used to describe the locations of people on a general continuous latent variable as well as on continuous orthogonal specific traits that characterize responses to groups of items. The bifactor graded response (bifac-GR) model is presented in contrast to a correlated traits (or multidimensional GR model) and unidimensional GR model. Bifac-GR model specification, assumptions, estimation, and interpretation are demonstrated with a reanalysis of data (Campbell, 2008) on the Shared Activities Questionnaire. We also show the importance of marginalizing the slopes for interpretation purposes and we extend the concept to the interpretation of the information function. To go along with the illustrative example analyses, we have made available supplementary files that include command file (syntax) examples and outputs from flexMIRT, IRTPRO, R, Mplus, and STATA. Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.jsp.2016.11.001. Data needed to reproduce analyses in this article are available as supplemental materials (online only) in the Appendix of this article. Copyright © 2016 Society for the Study of School Psychology. Published by Elsevier Ltd. All rights reserved.
MODERATING ABILITY OF ITEM RESPONSE THEORY THROUGH PRIOR GUESSING PARAMETER
Directory of Open Access Journals (Sweden)
Siow Hoo Leong
2013-01-01
Full Text Available A psycho-technology approach to discouraging guessing in multiple-choice formatted item can be done through reducing the a priori guessing probability of an item. This study proposes a psychometrics framework of Item Response Theory (IRT to model the effect of having various priori guessing probabilities across different items. A prior guessing parameter is proposed to serves as a moderator of the ability parameter in the two parameter logistic IRT. The results show that the proposed prior guessing parameter successfully moderates the ability parameters of the subjects with different degrees of guessing. However, the prior guessing parameter is insensitive when the performance pattern is mixed within the testlet but similar across testlet with different priori guessing probabilities.
Cognitive versus stimulus-response theories of learning.
Holland, Peter C
2008-08-01
In his 1948 address to the Division of Theoretical-Experimental Psychology of the American Psychological Association, Kenneth W. Spence discussed six distinctions between cognitive and stimulus-response (S-R) theories of learning. In this article, I first review these six distinctions and then focus on two of them in the context of my own research. This research concerns the specification of stimulus-stimulus associations in associative learning and the characterization of the neural systems underlying those associations. In the course of describing Spence's views and my research, I hope to communicate some of the richness of Spence's S-R psychology and its currency within modern scientific analyses of behavior.
Cross-covariance functions for multivariate geostatistics
Genton, Marc G.
2015-05-01
Continuously indexed datasets with multiple variables have become ubiquitous in the geophysical, ecological, environmental and climate sciences, and pose substantial analysis challenges to scientists and statisticians. For many years, scientists developed models that aimed at capturing the spatial behavior for an individual process; only within the last few decades has it become commonplace to model multiple processes jointly. The key difficulty is in specifying the cross-covariance function, that is, the function responsible for the relationship between distinct variables. Indeed, these cross-covariance functions must be chosen to be consistent with marginal covariance functions in such a way that the second-order structure always yields a nonnegative definite covariance matrix. We review the main approaches to building cross-covariance models, including the linear model of coregionalization, convolution methods, the multivariate Matérn and nonstationary and space-time extensions of these among others. We additionally cover specialized constructions, including those designed for asymmetry, compact support and spherical domains, with a review of physics-constrained models. We illustrate select models on a bivariate regional climate model output example for temperature and pressure, along with a bivariate minimum and maximum temperature observational dataset; we compare models by likelihood value as well as via cross-validation co-kriging studies. The article closes with a discussion of unsolved problems. © Institute of Mathematical Statistics, 2015.
Directory of Open Access Journals (Sweden)
Mr Nahadi
2011-10-01
Full Text Available This research is title “Test Development and Analysis of First Grade Senior High School Final Examination in chemistry Based on Classical Test Theory and Item Response Theory”. This research is conducted to develop a standard test instrument for final examination in senior high school at first grade using analysis based on classical test theory and item response theory. The test is a multiple choice test which consists of 75 items. Each item has five options. The research method is research and development method to get a product of test items which fulfill item criterion such as validity, reliability, item discrimination, item difficulty and distracting options quality based on classical test theory and validity, reliability, item discrimination, item difficulty and pseudo-guessing based on item response theory. The three parameter item response theory model is used in this research. Research and development method is conducted until preliminary field test to 102 first grade students in senior high school. Based on the research result, the test fulfills criterion as a good instrument based on classical test theory and item response theory. The final examination test items have vary of item quality so that some of them need a revision to make them better either for the stem and the options. From the total of 75 test items, 21 test items are declined and 54 test items are accepted.
Responses to Sex-Bias Criticism in Cognitive Moral Theory.
Socoski, Patrick M.
This paper explores the issue of sex bias in a contemporary major theory of moral development, cognitive moral theory. It explains critical reactions by Carol Gilligan and others questioning whether cognitive moral theory adequately accounts for female moral reasoning and behavior in its theory and research procedures. Several general…
Twisted Covariant Noncommutative Self-dual Gravity
Estrada-Jimenez, S; Obregón, O; Ramírez, C
2008-01-01
A twisted covariant formulation of noncommutative self-dual gravity is presented. The recent formulation introduced by J. Wess and coworkers for constructing twisted Yang-Mills fields is used. It is shown that the noncommutative torsion is solved at any order of the $\\theta$-expansion in terms of the tetrad and the extra fields of the theory. In the process the first order expansion in $\\theta$ for the Pleba\\'nski action is explicitly obtained.
Covariant quantization of the CBS superparticle
Energy Technology Data Exchange (ETDEWEB)
Grassi, P.A. E-mail: pag5@nyu.edu; Policastro, G.; Porrati, M
2001-07-09
The quantization of the Casalbuoni-Brink-Schwarz superparticle is performed in an explicitly covariant way using the antibracket formalism. Since an infinite number of ghost fields are required, within a suitable off-shell twistor-like formalism, we are able to fix the gauge of each ghost sector without modifying the physical content of the theory. The computation reveals that the antibracket cohomology contains only the physical degrees of freedom.
Superfield quantization in Sp(2) covariant formalism
Lavrov, P M
2001-01-01
The rules of the superfield Sp(2) covariant quantization of the arbitrary gauge theories for the case of the introduction of the gauging with the derivative equations for the gauge functional are generalized. The possibilities of realization of the expanded anti-brackets are considered and it is shown, that only one of the realizations is compatible with the transformations of the expanded BRST-symmetry in the form of super translations along the Grassmann superspace coordinates
Covariant quantization of the CBS superparticle
Grassi, P. A.; Policastro, G.; Porrati, M.
2001-07-01
The quantization of the Casalbuoni-Brink-Schwarz superparticle is performed in an explicitly covariant way using the antibracket formalism. Since an infinite number of ghost fields are required, within a suitable off-shell twistor-like formalism, we are able to fix the gauge of each ghost sector without modifying the physical content of the theory. The computation reveals that the antibracket cohomology contains only the physical degrees of freedom.
Unravelling Lorentz Covariance and the Spacetime Formalism
Directory of Open Access Journals (Sweden)
Cahill R. T.
2008-10-01
Full Text Available We report the discovery of an exact mapping from Galilean time and space coordinates to Minkowski spacetime coordinates, showing that Lorentz covariance and the space-time construct are consistent with the existence of a dynamical 3-space, and absolute motion. We illustrate this mapping first with the standard theory of sound, as vibrations of a medium, which itself may be undergoing fluid motion, and which is covariant under Galilean coordinate transformations. By introducing a different non-physical class of space and time coordinates it may be cast into a form that is covariant under Lorentz transformations wherein the speed of sound is now the invariant speed. If this latter formalism were taken as fundamental and complete we would be lead to the introduction of a pseudo-Riemannian spacetime description of sound, with a metric characterised by an invariant speed of sound. This analysis is an allegory for the development of 20th century physics, but where the Lorentz covariant Maxwell equations were constructed first, and the Galilean form was later constructed by Hertz, but ignored. It is shown that the Lorentz covariance of the Maxwell equations only occurs because of the use of non-physical space and time coordinates. The use of this class of coordinates has confounded 20th century physics, and resulted in the existence of a allowing dynamical 3-space being overlooked. The discovery of the dynamics of this 3-space has lead to the derivation of an extended gravity theory as a quantum effect, and confirmed by numerous experiments and observations
Unravelling Lorentz Covariance and the Spacetime Formalism
Directory of Open Access Journals (Sweden)
Cahill R. T.
2008-10-01
Full Text Available We report the discovery of an exact mapping from Galilean time and space coordinates to Minkowski spacetime coordinates, showing that Lorentz covariance and the space- time construct are consistent with the existence of a dynamical 3-space, and “absolute motion”. We illustrate this mapping first with the standard theory of sound, as vibra- tions of a medium, which itself may be undergoing fluid motion, and which is covari- ant under Galilean coordinate transformations. By introducing a different non-physical class of space and time coordinates it may be cast into a form that is covariant under “Lorentz transformations” wherein the speed of sound is now the “invariant speed”. If this latter formalism were taken as fundamental and complete we would be lead to the introduction of a pseudo-Riemannian “spacetime” description of sound, with a metric characterised by an “invariant speed of sound”. This analysis is an allegory for the development of 20th century physics, but where the Lorentz covariant Maxwell equa- tions were constructed first, and the Galilean form was later constructed by Hertz, but ignored. It is shown that the Lorentz covariance of the Maxwell equations only occurs because of the use of non-physical space and time coordinates. The use of this class of coordinates has confounded 20th century physics, and resulted in the existence of a “flowing” dynamical 3-space being overlooked. The discovery of the dynamics of this 3-space has lead to the derivation of an extended gravity theory as a quantum effect, and confirmed by numerous experiments and observations
A Teacher's Introduction to Reader-Response Theories. NCTE Teacher's Introduction Series.
Beach, Richard
This book offers teachers a convenient means of broadening their understanding of reader response theory and criticism and applying this theory to the teaching of literature in high school and college classrooms. The book is designed to arouse individual teachers' interest in reader response theory and encourage them to apply it to their teaching.…
Hubeny, Veronika E
2014-01-01
A recently explored interesting quantity in AdS/CFT, dubbed 'residual entropy', characterizes the amount of collective ignorance associated with either boundary observers restricted to finite time duration, or bulk observers who lack access to a certain spacetime region. However, the previously-proposed expression for this quantity involving variation of boundary entanglement entropy (subsequently renamed to 'differential entropy') works only in a severely restrictive context. We explain the key limitations, arguing that in general, differential entropy does not correspond to residual entropy. Given that the concept of residual entropy as collective ignorance transcends these limitations, we identify two correspondingly robust, covariantly-defined constructs: a 'strip wedge' associated with boundary observers and a 'rim wedge' associated with bulk observers. These causal sets are well-defined in arbitrary time-dependent asymptotically AdS spacetimes in any number of dimensions. We discuss their relation, spec...
Bayes linear covariance matrix adjustment
Wilkinson, Darren J
1995-01-01
In this thesis, a Bayes linear methodology for the adjustment of covariance matrices is presented and discussed. A geometric framework for quantifying uncertainties about covariance matrices is set up, and an inner-product for spaces of random matrices is motivated and constructed. The inner-product on this space captures aspects of our beliefs about the relationship between covariance matrices of interest to us, providing a structure rich enough for us to adjust beliefs about unknown matrices in the light of data such as sample covariance matrices, exploiting second-order exchangeability and related specifications to obtain representations allowing analysis. Adjustment is associated with orthogonal projection, and illustrated with examples of adjustments for some common problems. The problem of adjusting the covariance matrices underlying exchangeable random vectors is tackled and discussed. Learning about the covariance matrices associated with multivariate time series dynamic linear models is shown to be a...
Directory of Open Access Journals (Sweden)
Jesús García-de-Madariaga
2011-10-01
Full Text Available There has been a lot of discussion about corporate social responsibility (CSR during these last decades. Neoclassical authors support the idea that CSR is not compatible with the objective of profit maximization, and defenders of CSR argue that, in these times of globalization and network economies, the idea of a company managed just to meet shareholders’ interests does not support itself. However, beyond this discussion, how can CSR affect firms’ market value? If we found a positive relationship between these variables, we could conclude that the two theories are reconcilable and the objective of profit maximization, perhaps, should satisfy not only shareholders’ interests, but also stakeholders’. We review previous literature and propose a model to analyze how CSR affects firms’ market value.
HIGH DIMENSIONAL COVARIANCE MATRIX ESTIMATION IN APPROXIMATE FACTOR MODELS.
Fan, Jianqing; Liao, Yuan; Mincheva, Martina
2011-01-01
The variance covariance matrix plays a central role in the inferential theories of high dimensional factor models in finance and economics. Popular regularization methods of directly exploiting sparsity are not directly applicable to many financial problems. Classical methods of estimating the covariance matrices are based on the strict factor models, assuming independent idiosyncratic components. This assumption, however, is restrictive in practical applications. By assuming sparse error covariance matrix, we allow the presence of the cross-sectional correlation even after taking out common factors, and it enables us to combine the merits of both methods. We estimate the sparse covariance using the adaptive thresholding technique as in Cai and Liu (2011), taking into account the fact that direct observations of the idiosyncratic components are unavailable. The impact of high dimensionality on the covariance matrix estimation based on the factor structure is then studied.
High-dimensional covariance matrix estimation in approximate factor models
Fan, Jianqing; Mincheva, Martina; 10.1214/11-AOS944
2012-01-01
The variance--covariance matrix plays a central role in the inferential theories of high-dimensional factor models in finance and economics. Popular regularization methods of directly exploiting sparsity are not directly applicable to many financial problems. Classical methods of estimating the covariance matrices are based on the strict factor models, assuming independent idiosyncratic components. This assumption, however, is restrictive in practical applications. By assuming sparse error covariance matrix, we allow the presence of the cross-sectional correlation even after taking out common factors, and it enables us to combine the merits of both methods. We estimate the sparse covariance using the adaptive thresholding technique as in Cai and Liu [J. Amer. Statist. Assoc. 106 (2011) 672--684], taking into account the fact that direct observations of the idiosyncratic components are unavailable. The impact of high dimensionality on the covariance matrix estimation based on the factor structure is then studi...
A method of moments for calculating dynamic responses beyond linear response theory
Institute of Scientific and Technical Information of China (English)
Kang Yan-Mei; Xu Jian-Xue; Xie Yong
2005-01-01
A method of moments for calculating the dynamic response of periodically driven overdamped nonlinear stochastic systems in the general response sense is proposed, which is a modification of the method of moments confined within linear response theory. The calculating experience suggests that the proposed technique is simple and efficient in implementation, and the comparison with stochastic simulation shows that the first three orders of susceptibilities calculated by the proposed technique have high accuracy. The dependence of the spectral amplification parameters at the first three harmonics on the noise intensity is also investigated, and another observed phenomenon of stochastic resonance in the systems induced by the location of a single periodic orbit is disclosed and explained.
Bayesian item fit analysis for unidimensional item response theory models.
Sinharay, Sandip
2006-11-01
Assessing item fit for unidimensional item response theory models for dichotomous items has always been an issue of enormous interest, but there exists no unanimously agreed item fit diagnostic for these models, and hence there is room for further investigation of the area. This paper employs the posterior predictive model-checking method, a popular Bayesian model-checking tool, to examine item fit for the above-mentioned models. An item fit plot, comparing the observed and predicted proportion-correct scores of examinees with different raw scores, is suggested. This paper also suggests how to obtain posterior predictive p-values (which are natural Bayesian p-values) for the item fit statistics of Orlando and Thissen that summarize numerically the information in the above-mentioned item fit plots. A number of simulation studies and a real data application demonstrate the effectiveness of the suggested item fit diagnostics. The suggested techniques seem to have adequate power and reasonable Type I error rate, and psychometricians will find them promising.
Perturbative approach to covariance matrix of the matter power spectrum
Energy Technology Data Exchange (ETDEWEB)
Mohammed, Irshad [Fermilab; Seljak, Uros [UC, Berkeley, Astron. Dept.; Vlah, Zvonimir [Stanford U., ITP
2016-06-30
We evaluate the covariance matrix of the matter power spectrum using perturbation theory up to dominant terms at 1-loop order and compare it to numerical simulations. We decompose the covariance matrix into the disconnected (Gaussian) part, trispectrum from the modes outside the survey (beat coupling or super-sample variance), and trispectrum from the modes inside the survey, and show how the different components contribute to the overall covariance matrix. We find the agreement with the simulations is at a 10\\% level up to $k \\sim 1 h {\\rm Mpc^{-1}}$. We show that all the connected components are dominated by the large-scale modes ($k<0.1 h {\\rm Mpc^{-1}}$), regardless of the value of the wavevectors $k,\\, k'$ of the covariance matrix, suggesting that one must be careful in applying the jackknife or bootstrap methods to the covariance matrix. We perform an eigenmode decomposition of the connected part of the covariance matrix, showing that at higher $k$ it is dominated by a single eigenmode. The full covariance matrix can be approximated as the disconnected part only, with the connected part being treated as an external nuisance parameter with a known scale dependence, and a known prior on its variance for a given survey volume. Finally, we provide a prescription for how to evaluate the covariance matrix from small box simulations without the need to simulate large volumes.
Perturbative approach to covariance matrix of the matter power spectrum
Mohammed, Irshad; Seljak, Uroš; Vlah, Zvonimir
2017-04-01
We evaluate the covariance matrix of the matter power spectrum using perturbation theory up to dominant terms at 1-loop order and compare it to numerical simulations. We decompose the covariance matrix into the disconnected (Gaussian) part, trispectrum from the modes outside the survey (supersample variance) and trispectrum from the modes inside the survey, and show how the different components contribute to the overall covariance matrix. We find the agreement with the simulations is at a 10 per cent level up to k ˜ 1 h Mpc-1. We show that all the connected components are dominated by the large-scale modes (k covariance matrix, suggesting that one must be careful in applying the jackknife or bootstrap methods to the covariance matrix. We perform an eigenmode decomposition of the connected part of the covariance matrix, showing that at higher k, it is dominated by a single eigenmode. The full covariance matrix can be approximated as the disconnected part only, with the connected part being treated as an external nuisance parameter with a known scale dependence, and a known prior on its variance for a given survey volume. Finally, we provide a prescription for how to evaluate the covariance matrix from small box simulations without the need to simulate large volumes.
Covariant Quantization of CPT-violating Photons
Colladay, D; Noordmans, J P; Potting, R
2016-01-01
We perform the covariant canonical quantization of the CPT- and Lorentz-symmetry-violating photon sector of the minimal Standard-Model Extension, which contains a general (timelike, lightlike, or spacelike) fixed background tensor $k_{AF}^\\mu$. Well-known stability issues, arising from complex-valued energy states, are solved by introducing a small photon mass, orders of magnitude below current experimental bounds. We explicitly construct a covariant basis of polarization vectors, in which the photon field can be expanded. We proceed to derive the Feynman propagator and show that the theory is microcausal. Despite the occurrence of negative energies and vacuum-Cherenkov radiation, we do not find any runaway stability issues, because the energy remains bounded from below. An important observation is that the ordering of the roots of the dispersion relations is the same in any observer frame, which allows for a frame-independent condition that selects the correct branch of the dispersion relation. This turns ou...
On covariance structure in noisy, big data
Paffenroth, Randy C.; Nong, Ryan; Du Toit, Philip C.
2013-09-01
Herein we describe theory and algorithms for detecting covariance structures in large, noisy data sets. Our work uses ideas from matrix completion and robust principal component analysis to detect the presence of low-rank covariance matrices, even when the data is noisy, distorted by large corruptions, and only partially observed. In fact, the ability to handle partial observations combined with ideas from randomized algorithms for matrix decomposition enables us to produce asymptotically fast algorithms. Herein we will provide numerical demonstrations of the methods and their convergence properties. While such methods have applicability to many problems, including mathematical finance, crime analysis, and other large-scale sensor fusion problems, our inspiration arises from applying these methods in the context of cyber network intrusion detection.
Covariant holography of a tachyonic accelerating universe
Rozas-Fernández, Alberto
2014-01-01
We apply the holographic principle to a flat dark energy dominated Friedmann-Robertson-Walker spacetime filled with a tachyon scalar field with constant equation of state $w=p/\\rho$, both for $w>-1$ and $w<-1$. By using a geometrical covariant procedure, which allows the construction of holographic hypersurfaces, we have obtained for each case the position of the preferred screen and have then compared these with those obtained by using the holographic dark energy model with the future event horizon as the infrared cutoff. In the phantom scenario, one of the two obtained holographic screens is placed on the big rip hypersurface, both for the covariant holographic formalism and the holographic phantom model. It is also analysed whether the existence of these preferred screens allows a mathematically consistent formulation of fundamental theories based on the existence of a S matrix at infinite distances.
Covariant holography of a tachyonic accelerating universe
Energy Technology Data Exchange (ETDEWEB)
Rozas-Fernandez, Alberto [Consejo Superior de Investigaciones Cientificas, Instituto de Fisica Fundamental, Madrid (Spain); University of Portsmouth, Institute of Cosmology and Gravitation, Portsmouth (United Kingdom)
2014-08-15
We apply the holographic principle to a flat dark energy dominated Friedmann-Robertson-Walker spacetime filled with a tachyon scalar field with constant equation of state w = p/ρ, both for w > -1 and w < -1. By using a geometrical covariant procedure, which allows the construction of holographic hypersurfaces, we have obtained for each case the position of the preferred screen and have then compared these with those obtained by using the holographic dark energy model with the future event horizon as the infrared cutoff. In the phantom scenario, one of the two obtained holographic screens is placed on the big rip hypersurface, both for the covariant holographic formalism and the holographic phantom model. It is also analyzed whether the existence of these preferred screens allows a mathematically consistent formulation of fundamental theories based on the existence of an S-matrix at infinite distances. (orig.)
Chiral Four-Dimensional Heterotic Covariant Lattices
Beye, Florian
2014-01-01
In the covariant lattice formalism, chiral four-dimensional heterotic string vacua are obtained from certain even self-dual lattices which completely decompose into a left-mover and a right-mover lattice. The main purpose of this work is to classify all right-mover lattices that can appear in such a chiral model, and to study the corresponding left-mover lattices using the theory of lattice genera. In particular, the Smith-Minkowski-Siegel mass formula is employed to calculate a lower bound on the number of left-mover lattices. Also, the known relationship between asymmetric orbifolds and covariant lattices is considered in the context of our classification.
Reflections on Yvonne Rydin's response to 'Theorizing practice and practising theory'.
Boelens, L.
2010-01-01
I am most grateful to Yvonne Rydin for her response on my modest contribution to planning theory from a practitioner’s point of view. Her response includes a host of new insights reflecting on the key issues of concern...
Adult Attachment Ratings (AAR): an item response theory analysis.
Pilkonis, Paul A; Kim, Yookyung; Yu, Lan; Morse, Jennifer Q
2014-01-01
The Adult Attachment Ratings (AAR) include 3 scales for anxious, ambivalent attachment (excessive dependency, interpersonal ambivalence, and compulsive care-giving), 3 for avoidant attachment (rigid self-control, defensive separation, and emotional detachment), and 1 for secure attachment. The scales include items (ranging from 6-16 in their original form) scored by raters using a 3-point format (0 = absent, 1 = present, and 2 = strongly present) and summed to produce a total score. Item response theory (IRT) analyses were conducted with data from 414 participants recruited from psychiatric outpatient, medical, and community settings to identify the most informative items from each scale. The IRT results allowed us to shorten the scales to 5-item versions that are more precise and easier to rate because of their brevity. In general, the effective range of measurement for the scales was 0 to +2 SDs for each of the attachment constructs; that is, from average to high levels of attachment problems. Evidence for convergent and discriminant validity of the scales was investigated by comparing them with the Experiences of Close Relationships-Revised (ECR-R) scale and the Kobak Attachment Q-sort. The best consensus among self-reports on the ECR-R, informant ratings on the ECR-R, and expert judgments on the Q-sort and the AAR emerged for anxious, ambivalent attachment. Given the good psychometric characteristics of the scale for secure attachment, however, this measure alone might provide a simple alternative to more elaborate procedures for some measurement purposes. Conversion tables are provided for the 7 scales to facilitate transformation from raw scores to IRT-calibrated (theta) scores.
Non-Linear Wave Loads and Ship responses by a time-domain Strip Theory
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui; Jensen, Jørgen Juncher
1998-01-01
A non-linear time-domain strip theory for vertical wave loads and ship responses is presented. The theory is generalized from a rigorous linear time-domain strip theory representaton. The hydrodynamic memory effect due to the free surface is approximated by a higher order differential equation...
The Value of Item Response Theory in Clinical Assessment: A Review
Thomas, Michael L.
2011-01-01
Item response theory (IRT) and related latent variable models represent modern psychometric theory, the successor to classical test theory in psychological assessment. Although IRT has become prevalent in the measurement of ability and achievement, its contributions to clinical domains have been less extensive. Applications of IRT to clinical…
Response to Patrick Love's "Informal Theory": A Rejoinder
Evans, Nancy J.; Guido, Florence M.
2012-01-01
This rejoinder to Patrick Love's article, "Informal Theory: The Ignored Link in Theory-to-Practice," which appears earlier in this issue of the "Journal of College Student Development", was written at the invitation of the Editor. In the critique, we point out the weaknesses of many of Love's arguments and propositions. We provide an alternative…
The Expansion of the Responsibility Theory of the Economic Law
Institute of Scientific and Technical Information of China (English)
ZhangShouwen,; ZhuShida; DavidKelly
2004-01-01
Liability theory is a troublesome area in the theory of economic law. While objectively existing, there is controversy about whether there is a unique liability form. This has to be studied with both contradiction and relation analysis. There are gaps in the conventional distinction of ""sectoral"" (i.e.,economic) law and liability. A theoretical
Inquiring Minds, Meaningful Responses: Children's Interests, Inquiries, and Working Theories
Hedges, Helen; Cooper, Maria
2014-01-01
This project/report partnered researchers with teachers from two centres to explore and theorise understandings of children's inquiries and working theories. This project investigated the following questions: (1) What is the nature and content of infants', toddlers' and young children's inquiries and working theories in relation to their everyday…
DEFF Research Database (Denmark)
Yan, Wei
2015-01-01
We investigate the hydrodynamic theory of metals, offering systematic studies of the linear-response dynamics for an inhomogeneous electron gas. We include the quantum functional terms of the Thomas-Fermi kinetic energy, the von Weizsa¨cker kinetic energy, and the exchange-correlation Coulomb...... response of complex metallic nanostructures, including quantum effects, by adjusting theory parameters appropriately....... energies under the local density approximation. The advantages, limitations, and possible improvements of the hydrodynamic theory are transparently demonstrated. The roles of various parameters in the theory are identified. We anticipate that the hydrodynamic theory can be applied to investigate the linear...
Queiroz,Odoisa Antunes de; Primi,Ricardo; Carvalho,Lucas de Francisco; Enumo,Sônia Regina Fiorim
2013-01-01
Dynamic testing, with an intermediate phase of assistance, measures changes between pretest and post-test assuming a common metric between them. To test this assumption we applied the Item Response Theory in the responses of 69 children to dynamic cognitive testing Children's Analogical Thinking Modifiability Test adapted, with 12 items, totaling 828 responses, with the purpose of verifying if the original scale yields the same results as the equalized scale obtained by Item Response Theory i...
Covariant Thermodynamics and Relativity
Lopez-Monsalvo, C S
2011-01-01
This thesis deals with the dynamics of irreversible processes within the context of the general theory of relativity. In particular, we address the problem of the 'infinite' speed of propagation of thermal disturbances in a dissipative fluid. The present work builds on the multi-fluid variational approach to relativistic dissipation, pioneered by Carter, and provides a dynamical theory of heat conduction. The novel property of such approach is the thermodynamic interpretation associated with a two-fluid system whose constituents are matter and entropy. The dynamics of this model leads to a relativistic generalisation of the Cattaneo equation; the constitutive relation for causal heat transport. A comparison with the Israel and Stewart model is presented and its equivalence is shown. This discussion provides new insights into the not-well understood definition of a non-equilibrium temperature. The variational approach to heat conduction presented in this thesis constitutes a mathematically promising formalism ...
Covariant representations of subproduct systems
Viselter, Ami
2010-01-01
A celebrated theorem of Pimsner states that a covariant representation $T$ of a $C^*$-correspondence $E$ extends to a $C^*$-representation of the Toeplitz algebra of $E$ if and only if $T$ is isometric. This paper is mainly concerned with finding conditions for a covariant representation of a \\emph{subproduct system} to extend to a $C^*$-representation of the Toeplitz algebra. This framework is much more general than the former. We are able to find sufficient conditions, and show that in important special cases, they are also necessary. Further results include the universality of the tensor algebra, dilations of completely contractive covariant representations, Wold decompositions and von Neumann inequalities.
Schilling, Stephen G.
2007-01-01
In this paper the author examines the role of item response theory (IRT), particularly multidimensional item response theory (MIRT) in test validation from a validity argument perspective. The author provides justification for several structural assumptions and interpretations, taking care to describe the role he believes they should play in any…
Hospers, J. Mirjam Boeschen; Smits, Niels; Smits, Cas; Stam, Mariska; Terwee, Caroline B.; Kramer, Sophia E.
2016-01-01
Purpose: We reevaluated the psychometric properties of the Amsterdam Inventory for Auditory Disability and Handicap (AIADH; Kramer, Kapteyn, Festen, & Tobi, 1995) using item response theory. Item response theory describes item functioning along an ability continuum. Method: Cross-sectional data from 2,352 adults with and without hearing…
Reading Logs: An Application of Reader-Response Theory in ELT.
Carlisle, Anthony
2000-01-01
Introduces the activity of student-written reading logs as a practical application of reader-response theory in English-as-Foreign-Language literature teaching. Because reader-response theory stresses the synthesis between reader and text, it is proposed that practical applications should be based on the interaction. (Author/VWL)
Using Reader-Response Theory to Study Poetry about the Holocaust with High School Students.
Totten, Samuel
1998-01-01
Focuses on a lesson plan that uses reader-response theory to engage students in a study of a short poem about the holocaust. Reader response theory maintains that each reader brings valuable insight and experience to the interpretation of a work. Includes an annotated bibliography on Holocaust poetry. (MJP)
Hospers, J. Mirjam Boeschen; Smits, Niels; Smits, Cas; Stam, Mariska; Terwee, Caroline B.; Kramer, Sophia E.
2016-01-01
Purpose: We reevaluated the psychometric properties of the Amsterdam Inventory for Auditory Disability and Handicap (AIADH; Kramer, Kapteyn, Festen, & Tobi, 1995) using item response theory. Item response theory describes item functioning along an ability continuum. Method: Cross-sectional data from 2,352 adults with and without hearing…
General covariance in computational electrodynamics
DEFF Research Database (Denmark)
Shyroki, Dzmitry; Lægsgaard, Jesper; Bang, Ole;
2007-01-01
We advocate the generally covariant formulation of Maxwell equations as underpinning some recent advances in computational electrodynamics—in the dimensionality reduction for separable structures; in mesh truncation for finite-difference computations; and in adaptive coordinate mapping as opposed...
Zhu, Wei; Mitchell, Deborah A.
2012-01-01
This article reports a case study that examined English as a Second Language students' peer response stances from an activity theory perspective. More specifically, the study was guided by the constructs of activity and motive/object in Leont'ev's theory. Multiple sources of data were collected from two native Spanish-speaking students enrolled in…
How covariant is the galaxy luminosity function?
Smith, Robert E
2012-01-01
We investigate the error properties of certain galaxy luminosity function (GLF) estimators. Using a cluster expansion of the density field, we show how, for both volume and flux limited samples, the GLF estimates are covariant. The covariance matrix can be decomposed into three pieces: a diagonal term arising from Poisson noise; a sample variance term arising from large-scale structure in the survey volume; an occupancy covariance term arising due to galaxies of different luminosities inhabiting the same cluster. To evaluate the theory one needs: the mass function and bias of clusters, and the conditional luminosity function (CLF). We use a semi-analytic model (SAM) galaxy catalogue from the Millennium run N-body simulation and the CLF of Yang et al. (2003) to explore these effects. The GLF estimates from the SAM and the CLF qualitatively reproduce results from the 2dFGRS. We also measure the luminosity dependence of clustering in the SAM and find reasonable agreement with 2dFGRS results for bright galaxies. ...
Trouble shooting for covariance fitting in highly correlated data
Yoon, Boram; Lee, Weonjong; Jung, Chulwoo
2011-01-01
We report a possible solution to the trouble that the covariance fitting fails when the data is highly correlated and the covariance matrix has small eigenvalues. As an example, we choose the data analysis of highly correlated $B_K$ data on the basis of the SU(2) staggered chiral perturbation theory. Basically, the essence of the problem is that we do not have an accurate fitting function so that we cannot fit the highly correlated and precise data. When some eigenvalues of the covariance matrix are small, even a tiny error of fitting function can produce large chi-square and spoil the fitting procedure. We have applied a number of prescriptions available in the market such as diagonal approximation and cutoff method. In addition, we present a new method, the eigenmode shift method which fine-tunes the fitting function while keeping the covariance matrix untouched.
Covariance fitting of highly correlated $B_K$ data
Yoon, Boram; Jung, Chulwoo; Lee, Weonjong
2011-01-01
We present the reason why we use the diagonal approximation (uncorrelated fitting) when we perform the data analysis of highly correlated $B_K$ data on the basis of the SU(2) staggered chiral perturbation theory. Basically, the essence of the problem is that we do not have enough statistics to determine the small eigenvalues of the covariance matrix with a high precision. As a result, we have the smallest eigenvalue, which is smaller than the statistical error of the covariance matrix, corresponding to an unphysical eigenmode. We have applied a number of prescriptions available in the market such as the cutoff method and modified covariance matrix method. It turns out that the cutoff method is not a good prescription and the modified covariance matrix method is an even worse one. The diagonal approximation turns out to be a good prescription if the data points are somehow correlated and the statistics are relatively poor.
On spectral distribution of high dimensional covariation matrices
DEFF Research Database (Denmark)
Heinrich, Claudio; Podolskij, Mark
In this paper we present the asymptotic theory for spectral distributions of high dimensional covariation matrices of Brownian diffusions. More specifically, we consider N-dimensional Itô integrals with time varying matrix-valued integrands. We observe n equidistant high frequency data points...... of the underlying Brownian diffusion and we assume that N/n -> c in (0,oo). We show that under a certain mixed spectral moment condition the spectral distribution of the empirical covariation matrix converges in distribution almost surely. Our proof relies on method of moments and applications of graph theory....
Weeland, Martine M; Nijhof, Karin S; Otten, R; Vermaes, Ignace P R; Buitelaar, Jan K
2017-10-01
This study tests the validity of Beck's cognitive theory and Nolen-Hoeksema's response style theory of depression in adolescents with and without MBID. The relationship between negative cognitive errors (Beck), response styles (Nolen-Hoeksema) and depressive symptoms was examined in 135 adolescents using linear regression. The cognitive error 'underestimation of the ability to cope' was more prevalent among adolescents with MBID than among adolescents with average intelligence. This was the only negative cognitive error that predicted depressive symptoms. There were no differences between groups in the prevalence of the three response styles. In line with the theory, ruminating was positively and problem-solving was negatively related to depressive symptoms. Distractive response styles were not related to depressive symptoms. The relationship between response styles, cognitive errors and depressive symptoms were similar for both groups. The main premises of both theories of depression are equally applicable to adolescents with and without MBID. The cognitive error 'Underestimation of the ability to cope' poses a specific risk factor for developing a depression for adolescents with MBID and requires special attention in treatment and prevention of depression. WHAT THIS PAPER ADDS?: Despite the high prevalence of depression among adolescents with MBID, little is known about the etiology and cognitive processes that play a role in the development of depression in this group. The current paper fills this gap in research by examining the core tenets of two important theories on the etiology of depression (Beck's cognitive theory and Nolen-Hoeksema's response style theory) in a clinical sample of adolescents with and without MBID. This paper demonstrated that the theories are equally applicable to adolescents with MBID, as to adolescents with average intellectual ability. However, the cognitive bias 'underestimation of the ability to cope' was the only cognitive error
Zhang, Xing; Herbert, John M.
2015-02-01
We revisit the formalism for analytic derivative couplings between excited states in time-dependent density functional theory (TDDFT). We derive and implement these couplings using quadratic response theory, then numerically compare this response-theory formulation to couplings implemented previously based on a pseudo-wavefunction formalism and direct differentiation of the Kohn-Sham determinant. Numerical results, including comparison to full configuration interaction calculations, suggest that the two approaches perform equally well for many molecular systems, provided that the underlying DFT method affords accurate potential energy surfaces. The response contributions are found to be important for certain systems with high symmetry, but can be calculated with only a moderate increase in computational cost beyond what is required for the pseudo-wavefunction approach. In the case of spin-flip TDDFT, we provide a formal proof that the derivative couplings obtained using response theory are identical to those obtained from the pseudo-wavefunction formulation, which validates our previous implementation based on the latter formalism.
Zhang, Xing; Herbert, John M
2015-02-14
We revisit the formalism for analytic derivative couplings between excited states in time-dependent density functional theory (TDDFT). We derive and implement these couplings using quadratic response theory, then numerically compare this response-theory formulation to couplings implemented previously based on a pseudo-wavefunction formalism and direct differentiation of the Kohn-Sham determinant. Numerical results, including comparison to full configuration interaction calculations, suggest that the two approaches perform equally well for many molecular systems, provided that the underlying DFT method affords accurate potential energy surfaces. The response contributions are found to be important for certain systems with high symmetry, but can be calculated with only a moderate increase in computational cost beyond what is required for the pseudo-wavefunction approach. In the case of spin-flip TDDFT, we provide a formal proof that the derivative couplings obtained using response theory are identical to those obtained from the pseudo-wavefunction formulation, which validates our previous implementation based on the latter formalism.
Expanding Hipolito-Delgado and Lee's Empowerment Theory: A Response
Zalaquett, Carlos; D'Andrea, Michael
2007-01-01
Hipolito-Delgado and Lee's article entitled "Empowerment Theory for the Professional School Counselor: A Manifesto for What Really Matters" represents an important contribution to the school counseling literature for two reasons: (1) It helps to expand a growing knowledge base related to the work school counselors can do to foster the…
Applicability of cable theory to vascular conducted responses
DEFF Research Database (Denmark)
Hald, Bjørn Olav; Jensen, Lars Jørn; Sørensen, Preben Graae
2012-01-01
¿ adequately describes simulated conduction profiles. We find that several important cable theory assumptions are violated when applied to small blood vessels. However, the phenomenological use of a length-constant from a single exponential function is a good measure of conduction length. Hence, ¿ should...
Labour Market Theories and Distance Education: A Response.
Rumble, Greville
1996-01-01
Responds to comments on a previous series of three articles on labor market theories and distance education. Highlights include conceptual frameworks of Fordism, neo-Fordism, and post-Fordism; industrialization and its impact on education; work and academic work; mass production; and specialist markets and small-scale distance education systems.…
General Covariance from the Quantum Renormalization Group
Shyam, Vasudev
2016-01-01
The Quantum renormalization group (QRG) is a realisation of holography through a coarse graining prescription that maps the beta functions of a quantum field theory thought to live on the `boundary' of some space to holographic actions in the `bulk' of this space. A consistency condition will be proposed that translates into general covariance of the gravitational theory in the $D + 1$ dimensional bulk. This emerges from the application of the QRG on a planar matrix field theory living on the $D$ dimensional boundary. This will be a particular form of the Wess--Zumino consistency condition that the generating functional of the boundary theory needs to satisfy. In the bulk, this condition forces the Poisson bracket algebra of the scalar and vector constraints of the dual gravitational theory to close in a very specific manner, namely, the manner in which the corresponding constraints of general relativity do. A number of features of the gravitational theory will be fixed as a consequence of this form of the Po...
Transient response of lattice structures based on exact member theory
Anderson, Melvin S.
1989-01-01
The computer program BUNVIS-RG, which treats vibration and buckling of lattice structures using exact member stiffness matrices, has been extended to calculate the exact modal mass and stiffness quantities that can be used in a conventional transient response analysis based on modes. The exact nature of the development allows inclusion of local member response without introduction of any interior member nodes. Results are given for several problems in which significant interaction between local and global response occurs.
Calcul Stochastique Covariant à Sauts & Calcul Stochastique à Sauts Covariants
Maillard-Teyssier, Laurence
2003-01-01
We propose a stochastic covariant calculus forcàdlàg semimartingales in the tangent bundle $TM$ over a manifold $M$. A connection on $M$ allows us to define an intrinsic derivative ofa $C^1$ curve $(Y_t)$ in $TM$, the covariantderivative. More precisely, it is the derivative of$(Y_t)$ seen in a frame moving parallelly along its projection curve$(x_t)$ on $M$. With the transfer principle, Norris defined thestochastic covariant integration along a continuous semimartingale in$TM$. We describe t...
Development and validation of an item response theory-based Social Responsiveness Scale short form.
Sturm, Alexandra; Kuhfeld, Megan; Kasari, Connie; McCracken, James T
2017-09-01
Research and practice in autism spectrum disorder (ASD) rely on quantitative measures, such as the Social Responsiveness Scale (SRS), for characterization and diagnosis. Like many ASD diagnostic measures, SRS scores are influenced by factors unrelated to ASD core features. This study further interrogates the psychometric properties of the SRS using item response theory (IRT), and demonstrates a strategy to create a psychometrically sound short form by applying IRT results. Social Responsiveness Scale analyses were conducted on a large sample (N = 21,426) of youth from four ASD databases. Items were subjected to item factor analyses and evaluation of item bias by gender, age, expressive language level, behavior problems, and nonverbal IQ. Item selection based on item psychometric properties, DIF analyses, and substantive validity produced a reduced item SRS short form that was unidimensional in structure, highly reliable (α = .96), and free of gender, age, expressive language, behavior problems, and nonverbal IQ influence. The short form also showed strong relationships with established measures of autism symptom severity (ADOS, ADI-R, Vineland). Degree of association between all measures varied as a function of expressive language. Results identified specific SRS items that are more vulnerable to non-ASD-related traits. The resultant 16-item SRS short form may possess superior psychometric properties compared to the original scale and emerge as a more precise measure of ASD core symptom severity, facilitating research and practice. Future research using IRT is needed to further refine existing measures of autism symptomatology. © 2017 Association for Child and Adolescent Mental Health.
Industry and chain responsibilities and integrative social contract theory
Wempe, J.F.D.B. (Johan)
2010-01-01
This article shows that business ethics is not capable of explaining the responsibility of limited organized collectives such as chains, sectors and industries. The responsibility of the pharmaceutical industry to make AIDSblockers available for patients in Africa is an example of such a sector resp
Covariantizing Classical Field Theories
López, Marco Castrillón
2010-01-01
We show how to enlarge the covariance group of any classical field theory in such a way that the resulting "covariantized" theory is 'essentially equivalent' to the original. In particular, our technique will render any classical field theory generally covariant, that is, the covariantized theory will be spacetime diffeomorphism-covariant and free of absolute objects. Our results thus generalize the well-known parametrization technique of Dirac and Kucha\\v{r}. Our constructions apply equally well to internal covariance groups, in which context they produce natural derivations of both the Utiyama minimal coupling and St\\"uckelberg tricks.
Life history theory predicts fish assemblage response to hydrologic regimes.
Mims, Meryl C; Olden, Julian D
2012-01-01
The hydrologic regime is regarded as the primary driver of freshwater ecosystems, structuring the physical habitat template, providing connectivity, framing biotic interactions, and ultimately selecting for specific life histories of aquatic organisms. In the present study, we tested ecological theory predicting directional relationships between major dimensions of the flow regime and life history composition of fish assemblages in perennial free-flowing rivers throughout the continental United States. Using long-term discharge records and fish trait and survey data for 109 stream locations, we found that 11 out of 18 relationships (61%) tested between the three life history strategies (opportunistic, periodic, and equilibrium) and six hydrologic metrics (two each describing flow variability, predictability, and seasonality) were statistically significant (P history strategies, with 82% of all significant relationships observed supporting predictions from life history theory. Specifically, we found that (1) opportunistic strategists were positively related to measures of flow variability and negatively related to predictability and seasonality, (2) periodic strategists were positively related to high flow seasonality and negatively related to variability, and (3) the equilibrium strategists were negatively related to flow variability and positively related to predictability. Our study provides important empirical evidence illustrating the value of using life history theory to understand both the patterns and processes by which fish assemblage structure is shaped by adaptation to natural regimes of variability, predictability, and seasonality of critical flow events over broad biogeographic scales.
Covariant non-commutative space–time
Directory of Open Access Journals (Sweden)
Jonathan J. Heckman
2015-05-01
Full Text Available We introduce a covariant non-commutative deformation of 3+1-dimensional conformal field theory. The deformation introduces a short-distance scale ℓp, and thus breaks scale invariance, but preserves all space–time isometries. The non-commutative algebra is defined on space–times with non-zero constant curvature, i.e. dS4 or AdS4. The construction makes essential use of the representation of CFT tensor operators as polynomials in an auxiliary polarization tensor. The polarization tensor takes active part in the non-commutative algebra, which for dS4 takes the form of so(5,1, while for AdS4 it assembles into so(4,2. The structure of the non-commutative correlation functions hints that the deformed theory contains gravitational interactions and a Regge-like trajectory of higher spin excitations.
Multisymplectic formalism and the covariant phase
Hélein, Frédéric
2011-01-01
The formulation of a relativistic dynamical problem as a system of Hamilton equations by respecting the principles of Relativity is a delicate task, because in their classical form the Hamilton equations require the use of a time coordinate, which of course contradicts the Relativity. Two interesting solutions have been proposed during the last century: the covariant phase space and the multisymplectic formalism. These two approaches were inspired at the beginning by different points of view. However, as shown by works by Kijowski-Szczyrba, Forger-Romero and Vitagliano, a synthetic vision of the two theories leads probably to the most satisfactory answer to the basic question of understanding the Hamiltonian structure of relativistic fields theory.
Frederiksen, Claus S.
2009-01-01
This paper examines the relation between policies concerning Corporate Social Responsibility (CSR) and philosophical moral theories. The objective is to determine which moral theories form the basis for CSR policies. Are they based on ethical egoism, libertarianism, utilitarianism or some kind of common-sense morality? To address this issue, I conducted an empirical investigation examining the relation between moral theories and CSR policies, in companies engaged in CSR. Based ...
Szekeres models: a covariant approach
Apostolopoulos, Pantelis S
2016-01-01
We exploit the 1+1+2 formalism to covariantly describe the inhomogeneous and anisotropic Szekeres models. It is shown that an \\emph{average scale length} can be defined \\emph{covariantly} which satisfies a 2d equation of motion driven from the \\emph{effective gravitational mass} (EGM) contained in the dust cloud. The contributions to the EGM are encoded to the energy density of the dust fluid and the free gravitational field $E_{ab}$. In addition the notions of the Apparent and Absolute Apparent Horizons are briefly discussed and we give an alternative gauge-invariant form to define them in terms of the kinematical variables of the spacelike congruences. We argue that the proposed program can be used in order to express the Sachs optical equations in a covariant form and analyze the confrontation of a spatially inhomogeneous irrotational overdense fluid model with the observational data.
Covariance evaluation work at LANL
Energy Technology Data Exchange (ETDEWEB)
Kawano, Toshihiko [Los Alamos National Laboratory; Talou, Patrick [Los Alamos National Laboratory; Young, Phillip [Los Alamos National Laboratory; Hale, Gerald [Los Alamos National Laboratory; Chadwick, M B [Los Alamos National Laboratory; Little, R C [Los Alamos National Laboratory
2008-01-01
Los Alamos evaluates covariances for nuclear data library, mainly for actinides above the resonance regions and light elements in the enUre energy range. We also develop techniques to evaluate the covariance data, like Bayesian and least-squares fitting methods, which are important to explore the uncertainty information on different types of physical quantities such as elastic scattering angular distribution, or prompt neutron fission spectra. This paper summarizes our current activities of the covariance evaluation work at LANL, including the actinide and light element data mainly for the criticality safety study and transmutation technology. The Bayesian method based on the Kalman filter technique, which combines uncertainties in the theoretical model and experimental data, is discussed.
Curchod, Basile F E; Penfold, Thomas J; Rothlisberger, Ursula; Tavernelli, Ivano
2013-01-01
The implementation of local control theory using nonadiabatic molecular dynamics within the framework of linear-response time-dependent density functional theory is discussed. The method is applied to study the photoexcitation of lithium fluoride, for which we demonstrate that this approach can efficiently generate a pulse, on-the-fly, able to control the population transfer between two selected electronic states. Analysis of the computed control pulse yields insights into the photophysics of the process identifying the relevant frequencies associated to the curvature of the initial and final state potential energy curves and their energy differences. The limitations inherent to the use of the trajectory surface hopping approach are also discussed.
Mokken scale analysis : Between the Guttman scale and parametric item response theory
van Schuur, Wijbrandt H.
2003-01-01
This article introduces a model of ordinal unidimensional measurement known as Mokken scale analysis. Mokken scaling is based on principles of Item Response Theory (IRT) that originated in the Guttman scale. I compare the Mokken model with both Classical Test Theory (reliability or factor analysis)
Culturally Responsive Teaching in the Context of Mathematics: A Grounded Theory Case Study
Bonner, Emily P.; Adams, Thomasenia L.
2012-01-01
In this grounded theory case study, four interconnected, foundational cornerstones of culturally responsive mathematics teaching (CRMT), communication, knowledge, trust/relationships, and constant reflection/revision, were systematically unearthed to develop an initial working theory of CRMT that directly informs classroom practice. These…
Mokken scale analysis : Between the Guttman scale and parametric item response theory
van Schuur, Wijbrandt H.
2003-01-01
This article introduces a model of ordinal unidimensional measurement known as Mokken scale analysis. Mokken scaling is based on principles of Item Response Theory (IRT) that originated in the Guttman scale. I compare the Mokken model with both Classical Test Theory (reliability or factor analysis)
Cosmic Censorship Conjecture revisited: Covariantly
Hamid, Aymen I M; Maharaj, Sunil D
2014-01-01
In this paper we study the dynamics of the trapped region using a frame independent semi-tetrad covariant formalism for general Locally Rotationally Symmetric (LRS) class II spacetimes. We covariantly prove some important geometrical results for the apparent horizon, and state the necessary and sufficient conditions for a singularity to be locally naked. These conditions bring out, for the first time in a quantitative and transparent manner, the importance of the Weyl curvature in deforming and delaying the trapped region during continual gravitational collapse, making the central singularity locally visible.
Turning Reader-Response Theory into Student-Centered Classroom Practice.
McRae, Murdo William
1986-01-01
Describes how reader response theory can be easily adapted to classroom practice, thereby sharpening student interest in reading, increasing their capacity to reason and write, and fostering greater regard for different points of view. (HOD)
Davis, James N.
1989-01-01
Demonstrates Iser's reader-response theory provides a coherent framework for interpreting and teaching narratives in a foreign language. A sample lesson using the Iserian principle to improve students' reading of foreign language texts. (37 references) (CB)
Perturbative approach to covariance matrix of the matter power spectrum
Mohammed, Irshad; Vlah, Zvonimir
2016-01-01
We evaluate the covariance matrix of the matter power spectrum using perturbation theory up to dominant terms at 1-loop order and compare it to numerical simulations. We decompose the covariance matrix into the disconnected (Gaussian) part, trispectrum from the modes outside the survey (beat coupling or super-sample variance), and trispectrum from the modes inside the survey, and show how the different components contribute to the overall covariance matrix. We find the agreement with the simulations is at a 10\\% level up to $k \\sim 1 h {\\rm Mpc^{-1}}$. We show that all the connected components are dominated by the large-scale modes ($k<0.1 h {\\rm Mpc^{-1}}$), regardless of the value of the wavevectors $k,\\, k'$ of the covariance matrix, suggesting that one must be careful in applying the jackknife or bootstrap methods to the covariance matrix. We perform an eigenmode decomposition of the connected part of the covariance matrix, showing that at higher $k$ it is dominated by a single eigenmode. The full cova...
Covariance fitting of highly-correlated data in lattice QCD
Yoon, Boram; Jang, Yong-Chull; Jung, Chulwoo; Lee, Weonjong
2013-07-01
We address a frequently-asked question on the covariance fitting of highly-correlated data such as our B K data based on the SU(2) staggered chiral perturbation theory. Basically, the essence of the problem is that we do not have a fitting function accurate enough to fit extremely precise data. When eigenvalues of the covariance matrix are small, even a tiny error in the fitting function yields a large chi-square value and spoils the fitting procedure. We have applied a number of prescriptions available in the market, such as the cut-off method, modified covariance matrix method, and Bayesian method. We also propose a brand new method, the eigenmode shift (ES) method, which allows a full covariance fitting without modifying the covariance matrix at all. We provide a pedagogical example of data analysis in which the cut-off method manifestly fails in fitting, but the rest work well. In our case of the B K fitting, the diagonal approximation, the cut-off method, the ES method, and the Bayesian method work reasonably well in an engineering sense. However, interpreting the meaning of χ 2 is easier in the case of the ES method and the Bayesian method in a theoretical sense aesthetically. Hence, the ES method can be a useful alternative optional tool to check the systematic error caused by the covariance fitting procedure.
Generation of intensity covariations of the oxygen green and red lines in the nightglow
Misawa, K.; Takeuchi, I.; Kato, Y.; Aoyama, I.
1984-02-01
The cause of intensity covariations of the oxygen green and red lines is studied. Intensity covariations are compared with the auroral-electrojet-activity index AE, the substorm Pi2, and the magnetogram. It is suggested that intensity covariations or double-intensity maxima of the red line occur in association with intense auroral substorms, and that they are the direct experimental evidences of Testud's theory (1973).
Kiriushcheva, N; Kuzmin, S V
2011-01-01
We argue that the field-parametrization dependence of Dirac's procedure, for Hamiltonians with first-class constraints not only preserves covariance in covariant theories, but in non-covariant gauge theories it allows one to find the natural field parametrization in which the Hamiltonian formulation automatically leads to the simplest gauge symmetry.
Covariant description of isothermic surfaces
Tafel, Jacek
2014-01-01
We present a covariant formulation of the Gauss-Weingarten equations and the Gauss-Mainardi-Codazzi equations for surfaces in 3-dimensional curved spaces. We derive a coordinate invariant condition on the first and second fundamental form which is necessary and sufficient for the surface to be isothermic.
Condition Number Regularized Covariance Estimation.
Won, Joong-Ho; Lim, Johan; Kim, Seung-Jean; Rajaratnam, Bala
2013-06-01
Estimation of high-dimensional covariance matrices is known to be a difficult problem, has many applications, and is of current interest to the larger statistics community. In many applications including so-called the "large p small n" setting, the estimate of the covariance matrix is required to be not only invertible, but also well-conditioned. Although many regularization schemes attempt to do this, none of them address the ill-conditioning problem directly. In this paper, we propose a maximum likelihood approach, with the direct goal of obtaining a well-conditioned estimator. No sparsity assumption on either the covariance matrix or its inverse are are imposed, thus making our procedure more widely applicable. We demonstrate that the proposed regularization scheme is computationally efficient, yields a type of Steinian shrinkage estimator, and has a natural Bayesian interpretation. We investigate the theoretical properties of the regularized covariance estimator comprehensively, including its regularization path, and proceed to develop an approach that adaptively determines the level of regularization that is required. Finally, we demonstrate the performance of the regularized estimator in decision-theoretic comparisons and in the financial portfolio optimization setting. The proposed approach has desirable properties, and can serve as a competitive procedure, especially when the sample size is small and when a well-conditioned estimator is required.
Condition Number Regularized Covariance Estimation*
Won, Joong-Ho; Lim, Johan; Kim, Seung-Jean; Rajaratnam, Bala
2012-01-01
Estimation of high-dimensional covariance matrices is known to be a difficult problem, has many applications, and is of current interest to the larger statistics community. In many applications including so-called the “large p small n” setting, the estimate of the covariance matrix is required to be not only invertible, but also well-conditioned. Although many regularization schemes attempt to do this, none of them address the ill-conditioning problem directly. In this paper, we propose a maximum likelihood approach, with the direct goal of obtaining a well-conditioned estimator. No sparsity assumption on either the covariance matrix or its inverse are are imposed, thus making our procedure more widely applicable. We demonstrate that the proposed regularization scheme is computationally efficient, yields a type of Steinian shrinkage estimator, and has a natural Bayesian interpretation. We investigate the theoretical properties of the regularized covariance estimator comprehensively, including its regularization path, and proceed to develop an approach that adaptively determines the level of regularization that is required. Finally, we demonstrate the performance of the regularized estimator in decision-theoretic comparisons and in the financial portfolio optimization setting. The proposed approach has desirable properties, and can serve as a competitive procedure, especially when the sample size is small and when a well-conditioned estimator is required. PMID:23730197
Covariation Neglect among Novice Investors
Hedesstrom, Ted Martin; Svedsater, Henrik; Garling, Tommy
2006-01-01
In 4 experiments, undergraduates made hypothetical investment choices. In Experiment 1, participants paid more attention to the volatility of individual assets than to the volatility of aggregated portfolios. The results of Experiment 2 show that most participants diversified even when this increased risk because of covariation between the returns…
Barren Theory or Petty Craft: A Response to Professor Freedman.
Hope, Keith
1987-01-01
Response to Freedman's critique of path analysis discusses appropriate ways to represent social processes in numerical form and the use of path analysis to achieve that goal. Discusses two main issues: the selection of variables and whether multiple regression can be used to model social processes. (RB)
Metatheories and Organizational Theory: A Pragmatic Response to Metatheoretical Uncertainty
Directory of Open Access Journals (Sweden)
Stratos E. Ramoglou
2010-07-01
Full Text Available Metatheoretical dilemmas about the nature of the social world often animate organizational theorists who purport to dissolve pertinent controversies along truth-laden lines of philosophical argumentation. The present paper acknowledges the inescapable uncertainty at this level of discourse to nonetheless resist taking the usual step according to which metatheoretical discourse should be abandoned as unhelpful, if not misleading, metaphysics. However, it also parts from traditional modes of metatheoretical defense to instead try to identify whether metatheoretical frameworks, beyond considerations of any possible cognitive merit in deciphering the nature of the world, may be of any use in making a desirable difference in the world. In developing a pragmatist defense of realist metatheories, we may explicitly value metatheoretical discourse from a novel standpoint and further delineate subtle conceptual relations between metatheory, theory, phenomenological acceptance, action and epistemic ethics.
Marital, reproductive, and educational behaviors covary with life expectancy.
Krupp, Daniel Brian
2012-12-01
Theories of "life history evolution" suggest that individuals might adjust the timing of marriage and reproduction, as well as their propensity to terminate a marriage or pregnancy and invest in skill development, in response to indicators of the locally prevailing level of life expectancy. In particular, such theories generate the hypothesis that foreshortened time horizons lead to hastened reproduction and marriage whereas lengthier time horizons increase the likelihood of reproductive and marital termination and lead to greater investment in education. Here, I show that the scheduling and occurrence of marital and reproductive behavior (including both initiation and termination), as well as levels of educational attainment and investment, covary with life expectancy, even after controlling for the effects of affluence. In analyses of variation in marital, reproductive, and educational behaviors at two jurisdictional levels in Canada, life expectancy was positively correlated with patterns of age-specific fertility, age at first marriage, divorce, abortion, conferral of high school and higher education degrees (with the exception of the trades) and mean number of years of schooling. The large and highly consistent relationships observed between life expectancy and the behaviors under investigation suggest that these associations may be mediated by individual "perceptions" of life expectancy, though more research is needed before conclusions can be firmly reached.
Item Response Theory Using Hierarchical Generalized Linear Models
Directory of Open Access Journals (Sweden)
Hamdollah Ravand
2015-03-01
Full Text Available Multilevel models (MLMs are flexible in that they can be employed to obtain item and person parameters, test for differential item functioning (DIF and capture both local item and person dependence. Papers on the MLM analysis of item response data have focused mostly on theoretical issues where applications have been add-ons to simulation studies with a methodological focus. Although the methodological direction was necessary as a first step to show how MLMs can be utilized and extended to model item response data, the emphasis needs to be shifted towards providing evidence on how applications of MLMs in educational testing can provide the benefits that have been promised. The present study uses foreign language reading comprehension data to illustrate application of hierarchical generalized models to estimate person and item parameters, differential item functioning (DIF, and local person dependence in a three-level model.
Directory of Open Access Journals (Sweden)
Cheng eLy
2012-03-01
Full Text Available The responses of cortical neurons are highly variable across repeated presentations of a stimulus. Understanding this variability is critical for theories of both sensory and motor processing, since response variance affects the accuracy of neural codes. Despite this influence, the cellular and circuit mechanisms that shape the trial-to-trial variability of population responses remain poorly understood. We used a combination of experimental and computational techniques to uncover the mechanisms underlying response variability of populations of pyramidal (E cells in layer 2/3 of rat whisker barrel cortex. Spike trains recorded from pairs of E-cells during either spontaneous activity or whisker deflected responses show similarly low levels of spiking co-variability, despite large differences in network activation between the two states. We developed network models that show how spike threshold nonlinearities dilutes E-cell spiking co-variability during spontaneous activity and low velocity whisker deflections. In contrast, during high velocity whisker deflections, cancelation mechanisms mediated by feedforward inhibition maintain low E-cell pairwise co-variability. Thus, the combination of these two mechanisms ensure low E-cell population variability over a wide range of whisker deflection velocities. Finally, we show how this active decorrelation of population variability leads to a drastic increase in the population information about whisker velocity. The canonical cellular and circuit components of our study suggest that low network variability over a broad range of neural states may generalize across the nervous system.
Ly, Cheng; Middleton, Jason W; Doiron, Brent
2012-01-01
The responses of cortical neurons are highly variable across repeated presentations of a stimulus. Understanding this variability is critical for theories of both sensory and motor processing, since response variance affects the accuracy of neural codes. Despite this influence, the cellular and circuit mechanisms that shape the trial-to-trial variability of population responses remain poorly understood. We used a combination of experimental and computational techniques to uncover the mechanisms underlying response variability of populations of pyramidal (E) cells in layer 2/3 of rat whisker barrel cortex. Spike trains recorded from pairs of E-cells during either spontaneous activity or whisker deflected responses show similarly low levels of spiking co-variability, despite large differences in network activation between the two states. We developed network models that show how spike threshold non-linearities dilute E-cell spiking co-variability during spontaneous activity and low velocity whisker deflections. In contrast, during high velocity whisker deflections, cancelation mechanisms mediated by feedforward inhibition maintain low E-cell pairwise co-variability. Thus, the combination of these two mechanisms ensure low E-cell population variability over a wide range of whisker deflection velocities. Finally, we show how this active decorrelation of population variability leads to a drastic increase in the population information about whisker velocity. The prevalence of spiking non-linearities and feedforward inhibition in the nervous system suggests that the mechanisms for low network variability presented in our study may generalize throughout the brain.
Some remarks on the notions of general covariance and background independence
Giulini, Domenico
2006-01-01
In the first part of this paper I review some of the difficulties that seem to obstruct generally valid definitions of "general covariance" and/or "background independence" The second and more historical part deals with a rather strange argument that Einstein put forward in his 1913 "Entwurf paper" with M. Grossmann to discredit scalar theories of gravity in order to promote general covariance.
Power analysis in randomized clinical trials based on item response theory
Holman, Rebecca; Glas, Cees A.W.; Haan, de Rob J.
2003-01-01
Patient relevant outcomes, measured using questionnaires, are becoming increasingly popular endpoints in randomized clinical trials (RCTs). Recently, interest in the use of item response theory (IRT) to analyze the responses to such questionnaires has increased. In this paper, we used a simulation s
A Polytomous Item Response Theory Analysis of Social Physique Anxiety Scale
Fletcher, Richard B.; Crocker, Peter
2014-01-01
The present study investigated the social physique anxiety scale's factor structure and item properties using confirmatory factor analysis and item response theory. An additional aim was to identify differences in response patterns between groups (gender). A large sample of high school students aged 11-15 years (N = 1,529) consisting of n =…
Revision of the ICIDH Severity of Disabilities Scale by data linking and item response theory
Buuren, S. van; Hopman-Rock, M.
2001-01-01
The Severity of Disabilities Scale (SDS) of the ICIDH reflects the degree to which an individual's ability to perform a certain activity is restricted. This paper describes the application of two models from item response theory (IRT), the graded response model and the partial credit model, in order
Time-dependent current-density-functional theory for the metallic response of solids
Romaniello, P; de Boeij, PL
2005-01-01
We extend the formulation of time-dependent current-density-functional theory for the linear response properties of dielectric and semi-metallic solids [Kootstra , J. Chem. Phys. 112, 6517 (2000)] to treat metals as well. To achieve this, the Kohn-Sham response functions have to include both interba
Time-dependent current-density-functional theory for the metallic response of solids
Romaniello, P; de Boeij, PL
We extend the formulation of time-dependent current-density-functional theory for the linear response properties of dielectric and semi-metallic solids [Kootstra , J. Chem. Phys. 112, 6517 (2000)] to treat metals as well. To achieve this, the Kohn-Sham response functions have to include both
Min, Shangchao; He, Lianzhen
2014-01-01
This study examined the relative effectiveness of the multidimensional bi-factor model and multidimensional testlet response theory (TRT) model in accommodating local dependence in testlet-based reading assessment with both dichotomously and polytomously scored items. The data used were 14,089 test-takers' item-level responses to the testlet-based…
Estimation of Item Response Theory Parameters in the Presence of Missing Data
Finch, Holmes
2008-01-01
Missing data are a common problem in a variety of measurement settings, including responses to items on both cognitive and affective assessments. Researchers have shown that such missing data may create problems in the estimation of item difficulty parameters in the Item Response Theory (IRT) context, particularly if they are ignored. At the same…
Modelling non-ignorable missing-data mechanisms with item response theory models
Holman, Rebecca; Glas, Cees A.W.
2005-01-01
A model-based procedure for assessing the extent to which missing data can be ignored and handling non-ignorable missing data is presented. The procedure is based on item response theory modelling. As an example, the approach is worked out in detail in conjunction with item response data modelled us
A quantum-mechanical perspective on linear response theory within polarizable embedding
DEFF Research Database (Denmark)
List, Nanna Holmgaard; Norman, Patrick; Kongsted, Jacob
2017-01-01
We present a derivation of linear response theory within polarizable embedding starting from a rigorous quantum-mechanical treatment of a composite system. To this aim, two different subsystem decompositions (symmetric and nonsymmetric) of the linear response function are introduced and the pole...
Fitting Item Response Theory Models to Two Personality Inventories: Issues and Insights.
Chernyshenko, Oleksandr S.; Stark, Stephen; Chan, Kim-Yin; Drasgow, Fritz; Williams, Bruce
2001-01-01
Compared the fit of several Item Response Theory (IRT) models to two personality assessment instruments using data from 13,059 individuals responding to one instrument and 1,770 individuals responding to the other. Two- and three-parameter logistic models fit some scales reasonably well, but not others, and the graded response model generally did…
A Blind Detection Algorithm Utilizing Statistical Covariance in Cognitive Radio
Directory of Open Access Journals (Sweden)
Yingxue Li
2012-11-01
Full Text Available As the expression of performance parameters are obtained using asymptotic method in most blind covariance detection algorithm, the paper presented a new blind detection algorithm using cholesky factorization. Utilizing random matrix theory, we derived the performance parameters using non-asymptotic method. The proposed method overcomes the noise uncertainty problem and performs well without any information about the channel, primary user and noise. Numerical simulation results demonstrate that the performance parameters expressions are correct and the new detector outperforms the other blind covariance detectors.
Covariant Description of Transformation Optics in Linear and Nonlinear Media
Paul, Oliver
2011-01-01
The technique of transformation optics (TO) is an elegant method for the design of electromagnetic media with tailored optical properties. In this paper, we focus on the formal structure of TO theory. By using a complete covariant formalism, we present a general transformation law that holds for arbitrary materials including bianisotropic, magneto-optical, nonlinear and moving media. Due to the principle of general covariance, the formalism is applicable to arbitrary space-time coordinate transformations and automatically accounts for magneto-electric coupling terms. The formalism is demonstrated for the calculation of the second harmonic generation in a twisted TO concentrator.
Students' proficiency scores within multitrait item response theory
Scott, Terry F.; Schumayer, Daniel
2015-12-01
In this paper we present a series of item response models of data collected using the Force Concept Inventory. The Force Concept Inventory (FCI) was designed to poll the Newtonian conception of force viewed as a multidimensional concept, that is, as a complex of distinguishable conceptual dimensions. Several previous studies have developed single-trait item response models of FCI data; however, we feel that multidimensional models are also appropriate given the explicitly multidimensional design of the inventory. The models employed in the research reported here vary in both the number of fitting parameters and the number of underlying latent traits assumed. We calculate several model information statistics to ensure adequate model fit and to determine which of the models provides the optimal balance of information and parsimony. Our analysis indicates that all item response models tested, from the single-trait Rasch model through to a model with ten latent traits, satisfy the standard requirements of fit. However, analysis of model information criteria indicates that the five-trait model is optimal. We note that an earlier factor analysis of the same FCI data also led to a five-factor model. Furthermore the factors in our previous study and the traits identified in the current work match each other well. The optimal five-trait model assigns proficiency scores to all respondents for each of the five traits. We construct a correlation matrix between the proficiencies in each of these traits. This correlation matrix shows strong correlations between some proficiencies, and strong anticorrelations between others. We present an interpretation of this correlation matrix.
Social capital theory related to corporate social responsibility
Directory of Open Access Journals (Sweden)
Eva Abramuszkinová Pavlíková
2013-01-01
Full Text Available The article deals with corporate social responsibility and its relationship to strategic management dealing with acquisition, development and utilisation of essential inputs. They influence the design of processes related to the creation of products or services that satisfy customers’ needs. Authors claim that the successful securing, deployment and development of any input is of human origin or linked to human activity which means that the nature of relationships plays a crucial role. As businesses are not isolated, they operate on a global scale where the question of trust is very important. The concept of social capital stresses that trust in norms and reciprocity facilitate increased productivity in individuals, teams and organisations. Social capital promotes value-added collaboration including on-going and demonstrative transparency which can secure closer bonding among those group members. Business responsibility, CSR and Putnam’s definition of social capital is shown on real case studies as a sign of importance for credibility and effectiveness of any CSR efforts. It is evident that the good will and support garnered from CSR can be fragile and easily damaged.
AFCI-2.0 Neutron Cross Section Covariance Library
Energy Technology Data Exchange (ETDEWEB)
Herman, M.; Herman, M; Oblozinsky, P.; Mattoon, C.M.; Pigni, M.; Hoblit, S.; Mughabghab, S.F.; Sonzogni, A.; Talou, P.; Chadwick, M.B.; Hale, G.M.; Kahler, A.C.; Kawano, T.; Little, R.C.; Yount, P.G.
2011-03-01
The cross section covariance library has been under development by BNL-LANL collaborative effort over the last three years. The project builds on two covariance libraries developed earlier, with considerable input from BNL and LANL. In 2006, international effort under WPEC Subgroup 26 produced BOLNA covariance library by putting together data, often preliminary, from various sources for most important materials for nuclear reactor technology. This was followed in 2007 by collaborative effort of four US national laboratories to produce covariances, often of modest quality - hence the name low-fidelity, for virtually complete set of materials included in ENDF/B-VII.0. The present project is focusing on covariances of 4-5 major reaction channels for 110 materials of importance for power reactors. The work started under Global Nuclear Energy Partnership (GNEP) in 2008, which changed to Advanced Fuel Cycle Initiative (AFCI) in 2009. With the 2011 release the name has changed to the Covariance Multigroup Matrix for Advanced Reactor Applications (COMMARA) version 2.0. The primary purpose of the library is to provide covariances for AFCI data adjustment project, which is focusing on the needs of fast advanced burner reactors. Responsibility of BNL was defined as developing covariances for structural materials and fission products, management of the library and coordination of the work; LANL responsibility was defined as covariances for light nuclei and actinides. The COMMARA-2.0 covariance library has been developed by BNL-LANL collaboration for Advanced Fuel Cycle Initiative applications over the period of three years, 2008-2010. It contains covariances for 110 materials relevant to fast reactor R&D. The library is to be used together with the ENDF/B-VII.0 central values of the latest official release of US files of evaluated neutron cross sections. COMMARA-2.0 library contains neutron cross section covariances for 12 light nuclei (coolants and moderators), 78 structural
AFCI-2.0 Neutron Cross Section Covariance Library
Energy Technology Data Exchange (ETDEWEB)
Herman, M.; Herman, M; Oblozinsky, P.; Mattoon, C.M.; Pigni, M.; Hoblit, S.; Mughabghab, S.F.; Sonzogni, A.; Talou, P.; Chadwick, M.B.; Hale, G.M.; Kahler, A.C.; Kawano, T.; Little, R.C.; Yount, P.G.
2011-03-01
The cross section covariance library has been under development by BNL-LANL collaborative effort over the last three years. The project builds on two covariance libraries developed earlier, with considerable input from BNL and LANL. In 2006, international effort under WPEC Subgroup 26 produced BOLNA covariance library by putting together data, often preliminary, from various sources for most important materials for nuclear reactor technology. This was followed in 2007 by collaborative effort of four US national laboratories to produce covariances, often of modest quality - hence the name low-fidelity, for virtually complete set of materials included in ENDF/B-VII.0. The present project is focusing on covariances of 4-5 major reaction channels for 110 materials of importance for power reactors. The work started under Global Nuclear Energy Partnership (GNEP) in 2008, which changed to Advanced Fuel Cycle Initiative (AFCI) in 2009. With the 2011 release the name has changed to the Covariance Multigroup Matrix for Advanced Reactor Applications (COMMARA) version 2.0. The primary purpose of the library is to provide covariances for AFCI data adjustment project, which is focusing on the needs of fast advanced burner reactors. Responsibility of BNL was defined as developing covariances for structural materials and fission products, management of the library and coordination of the work; LANL responsibility was defined as covariances for light nuclei and actinides. The COMMARA-2.0 covariance library has been developed by BNL-LANL collaboration for Advanced Fuel Cycle Initiative applications over the period of three years, 2008-2010. It contains covariances for 110 materials relevant to fast reactor R&D. The library is to be used together with the ENDF/B-VII.0 central values of the latest official release of US files of evaluated neutron cross sections. COMMARA-2.0 library contains neutron cross section covariances for 12 light nuclei (coolants and moderators), 78 structural
Zhang, Zhongrui; Zhong, Quanlin; Niklas, Karl J.; Cai, Liang; Yang, Yusheng; Cheng, Dongliang
2016-08-01
Metabolic scaling theory (MST) posits that the scaling exponents among plant height H, diameter D, and biomass M will covary across phyletically diverse species. However, the relationships between scaling exponents and normalization constants remain unclear. Therefore, we developed a predictive model for the covariation of H, D, and stem volume V scaling relationships and used data from Chinese fir (Cunninghamia lanceolata) in Jiangxi province, China to test it. As predicted by the model and supported by the data, normalization constants are positively correlated with their associated scaling exponents for D vs. V and H vs. V, whereas normalization constants are negatively correlated with the scaling exponents of H vs. D. The prediction model also yielded reliable estimations of V (mean absolute percentage error = 10.5 ± 0.32 SE across 12 model calibrated sites). These results (1) support a totally new covariation scaling model, (2) indicate that differences in stem volume scaling relationships at the intra-specific level are driven by anatomical or ecophysiological responses to site quality and/or management practices, and (3) provide an accurate non-destructive method for predicting Chinese fir stem volume.
Zhang, Zhongrui; Zhong, Quanlin; Niklas, Karl J; Cai, Liang; Yang, Yusheng; Cheng, Dongliang
2016-08-24
Metabolic scaling theory (MST) posits that the scaling exponents among plant height H, diameter D, and biomass M will covary across phyletically diverse species. However, the relationships between scaling exponents and normalization constants remain unclear. Therefore, we developed a predictive model for the covariation of H, D, and stem volume V scaling relationships and used data from Chinese fir (Cunninghamia lanceolata) in Jiangxi province, China to test it. As predicted by the model and supported by the data, normalization constants are positively correlated with their associated scaling exponents for D vs. V and H vs. V, whereas normalization constants are negatively correlated with the scaling exponents of H vs. D. The prediction model also yielded reliable estimations of V (mean absolute percentage error = 10.5 ± 0.32 SE across 12 model calibrated sites). These results (1) support a totally new covariation scaling model, (2) indicate that differences in stem volume scaling relationships at the intra-specific level are driven by anatomical or ecophysiological responses to site quality and/or management practices, and (3) provide an accurate non-destructive method for predicting Chinese fir stem volume.
Hall Viscosity I: Linear Response Theory for Viscosity
Bradlyn, Barry; Goldstein, Moshe; Read, Nicholas
2012-02-01
In two dimensional systems with broken time-reversal symmetry, there can exist a non-dissipative viscosity coefficient [1,2,3]. This Hall viscosity is similar in nature to the non-dissipative Hall conductivity. In order to investigate this phenomenon further, we develop a linear response formalism for viscosity. We derive a Kubo formula for the frequency dependent viscosity tensor in the long wavelength limit. We compute the viscosity tensor for the free electron gas, integer quantum Hall systems, and two-dimensional paired superfluids. In the zero frequency limit, we show how the known results [3,4] for the Hall viscosity are recovered.[4pt] [1] J. Avron, R. Seiler, and P. Zograf, Phys. Rev. Lett. 75, 697 (1995).[0pt] [2] P. Levay, J. Math. Phys. 36, 2792 (1995).[0pt] [3] N. Read, Phys. Rev. B 79, 045308 (2009).[0pt] [4] N. Read and E. Rezayi, Phys. Rev. B 84, 085316 (2011).
Enabling Automated Dynamic Demand Response: From Theory to Practice
Energy Technology Data Exchange (ETDEWEB)
Frincu, Marc; Chelmis, Charalampos; Aman, Saima; Saeed, Rizwan; Zois, Vasileios; Prasanna, Viktor
2015-07-14
Demand response (DR) is a technique used in smart grids to shape customer load during peak hours. Automated DR offers utilities a fine grained control and a high degree of confidence in the outcome. However the impact on the customer's comfort means this technique is more suited for industrial and commercial settings than for residential homes. In this paper we propose a system for achieving automated controlled DR in a heterogeneous environment. We present some of the main issues arising in building such a system, including privacy, customer satisfiability, reliability, and fast decision turnaround, with emphasis on the solutions we proposed. Based on the lessons we learned from empirical results we describe an integrated automated system for controlled DR on the USC microgrid. Results show that while on a per building per event basis the accuracy of our prediction and customer selection techniques varies, it performs well on average when considering several events and buildings.
Covalent bonding from alchemical linear response density functional theory
Chang, K Y Samuel; Ramakrishnan, Raghunathan; von Lilienfeld, O Anatole
2015-01-01
We assess the predictive accuracy of linear response based estimates of changes in covalent bonding due to linear alchemical interpolations among molecules. We have investigated single bonds to hydrogen, as well as single, double, and triple bonds between main-group elements, occurring in small iso-electronic molecular spaces with atomic elements drawn from rows 2-3 in the $p$-block of the periodic table. Numerical evidence suggests that first order estimates of bonding potentials can achieve chemical accuracy if the alchemical interpolation connects molecules containing late elements in the periodic table (3$^{rd}$ and 4$^{th}$ row) and identical number of atoms and molecular geometries. For these interpolations, changes in bonding potential are near-linear in the coupling parameter, resulting in accurate Hellmann-Feynman predictions. Second order estimates for such interpolations yield worse predictions. The predictions become substantially worse if initial and final molecules differ not only in composition...
Agilan, V.; Umamahesh, N. V.
2017-03-01
Present infrastructure design is primarily based on rainfall Intensity-Duration-Frequency (IDF) curves with so-called stationary assumption. However, in recent years, the extreme precipitation events are increasing due to global climate change and creating non-stationarity in the series. Based on recent theoretical developments in the Extreme Value Theory (EVT), recent studies proposed a methodology for developing non-stationary rainfall IDF curve by incorporating trend in the parameters of the Generalized Extreme Value (GEV) distribution using Time covariate. But, the covariate Time may not be the best covariate and it is important to analyze all possible covariates and find the best covariate to model non-stationarity. In this study, five physical processes, namely, urbanization, local temperature changes, global warming, El Niño-Southern Oscillation (ENSO) cycle and Indian Ocean Dipole (IOD) are used as covariates. Based on these five covariates and their possible combinations, sixty-two non-stationary GEV models are constructed. In addition, two non-stationary GEV models based on Time covariate and one stationary GEV model are also constructed. The best model for each duration rainfall series is chosen based on the corrected Akaike Information Criterion (AICc). From the findings of this study, it is observed that the local processes (i.e., Urbanization, local temperature changes) are the best covariate for short duration rainfall and global processes (i.e., Global warming, ENSO cycle and IOD) are the best covariate for the long duration rainfall of the Hyderabad city, India. Furthermore, the covariate Time is never qualified as the best covariate. In addition, the identified best covariates are further used to develop non-stationary rainfall IDF curves of the Hyderabad city. The proposed methodology can be applied to other situations to develop the non-stationary IDF curves based on the best covariate.
Bayesian adjustment for covariate measurement errors: a flexible parametric approach.
Hossain, Shahadut; Gustafson, Paul
2009-05-15
In most epidemiological investigations, the study units are people, the outcome variable (or the response) is a health-related event, and the explanatory variables are usually environmental and/or socio-demographic factors. The fundamental task in such investigations is to quantify the association between the explanatory variables (covariates/exposures) and the outcome variable through a suitable regression model. The accuracy of such quantification depends on how precisely the relevant covariates are measured. In many instances, we cannot measure some of the covariates accurately. Rather, we can measure noisy (mismeasured) versions of them. In statistical terminology, mismeasurement in continuous covariates is known as measurement errors or errors-in-variables. Regression analyses based on mismeasured covariates lead to biased inference about the true underlying response-covariate associations. In this paper, we suggest a flexible parametric approach for avoiding this bias when estimating the response-covariate relationship through a logistic regression model. More specifically, we consider the flexible generalized skew-normal and the flexible generalized skew-t distributions for modeling the unobserved true exposure. For inference and computational purposes, we use Bayesian Markov chain Monte Carlo techniques. We investigate the performance of the proposed flexible parametric approach in comparison with a common flexible parametric approach through extensive simulation studies. We also compare the proposed method with the competing flexible parametric method on a real-life data set. Though emphasis is put on the logistic regression model, the proposed method is unified and is applicable to the other generalized linear models, and to other types of non-linear regression models as well. (c) 2009 John Wiley & Sons, Ltd.
DEFF Research Database (Denmark)
Kinnebrock, Silja; Podolskij, Mark
This paper introduces a new estimator to measure the ex-post covariation between high-frequency financial time series under market microstructure noise. We provide an asymptotic limit theory (including feasible central limit theorems) for standard methods such as regression, correlation analysis...... and covariance, for which we obtain the optimal rate of convergence. We demonstrate some positive semidefinite estimators of the covariation and construct a positive semidefinite estimator of the conditional covariance matrix in the central limit theorem. Furthermore, we indicate how the assumptions on the noise...
DEFF Research Database (Denmark)
Kinnebrock, Silja; Podolskij, Mark
and covariance, for which we obtain the optimal rate of convergence. We demonstrate some positive semidefinite estimators of the covariation and construct a positive semidefinite estimator of the conditional covariance matrix in the central limit theorem. Furthermore, we indicate how the assumptions on the noise......This paper introduces a new estimator to measure the ex-post covariation between high-frequency financial time series under market microstructure noise. We provide an asymptotic limit theory (including feasible central limit theorems) for standard methods such as regression, correlation analysis...
The Bridge from Text to Mind: Adapting Reader-Response Theory to Consumer Research.
Scott, Linda M.
1994-01-01
Consumer research on advertising response has gradually separated the act of reading an ad from the acquisition of brand information. Because the advertising text is the pathway through which brand information is accessed, current models truncate the process that leads to response in a way that distorts our view of both advertising and the mind that reads it. This author proposes that reader-response theory would help researchers study the process of reading as an essential link between adver...
Norman, Patrick
2011-12-14
The development of electronic response theory in quantum chemistry has been reviewed, starting from the early 1970's and reaching the current state-of-the-art. The general theory has been applied to the calculation of a large number of spectroscopic parameters over the years, and it has been implemented for the majority of standard electronic structure methods. Two formulations of response theory, the Ehrenfest expectation value and the quasi-energy derivative formulation, have turned into leading alternatives for the derivation of computationally tractable expressions of response functions, and they are here reviewed with an attempt to, as far as possible, leave out technical details. A set of four steps are identified as common in derivations of response functions, and the two formulations are compared along this series of steps. Particular emphasis is given to the situation when the oscillation of the weak external electromagnetic field is in resonance with a transition frequency of the system. The formation of physically sound response functions in resonance regions of the spectrum is discussed in light of the causality condition and the Kramers-Kronig relations, and it is achieved in wave function theory by means of the introduction of relaxation parameters in a manner that mimics what one sees in density matrix theory. As a working example, equations are illustrated by their application to a two-state model for para-nitroaniline including the ground and the lowest charge-transfer state in the electric dipole approximation.
The covariance of GPS coordinates and frames
Lachièze-Rey, M
2006-01-01
We explore, in the general relativistic context, the properties of the recently introduced GPS coordinates, as well as those of the associated frames and coframes. We show that they are covariant, and completely independent of any observer. We show that standard spectroscopic and astrometric observations allow any observer to measure (i) the values of the GPS coordinates at his position, (ii) the components of his [four-]velocity and (iii) the components of the metric in the GPS frame. This provides to this system an unique value both for conceptual discussion (no frame dependence) and for practical use (involved quantities are directly measurable): localisation, motion monitoring, astrometry, cosmography, tests of gravitation theories. We show explicitly, in the general relativistic context, how an observer may estimate its position and motion, and reconstruct the components of the metric. This arises from two main results: the extension of the velocity fields of the probes to the whole (curved) spacetime; a...
Noncommutative Spacetime Symmetries from Covariant Quantum Mechanics
Directory of Open Access Journals (Sweden)
Alessandro Moia
2017-01-01
Full Text Available In the last decades, noncommutative spacetimes and their deformed relativistic symmetries have usually been studied in the context of field theory, replacing the ordinary Minkowski background with an algebra of noncommutative coordinates. However, spacetime noncommutativity can also be introduced into single-particle covariant quantum mechanics, replacing the commuting operators representing the particle’s spacetime coordinates with noncommuting ones. In this paper, we provide a full characterization of a wide class of physically sensible single-particle noncommutative spacetime models and the associated deformed relativistic symmetries. In particular, we prove that they can all be obtained from the standard Minkowski model and the usual Poincaré transformations via a suitable change of variables. Contrary to previous studies, we find that spacetime noncommutativity does not affect the dispersion relation of a relativistic quantum particle, but only the transformation properties of its spacetime coordinates under translations and Lorentz transformations.
Universal Gravitation as Lorentz-covariant Dynamics
Kauffmann, Steven Kenneth
2014-01-01
Einstein's equivalence principle implies that the acceleration of a particle in a "specified" gravitational field is independent of its mass. While this is certainly true to great accuracy for bodies we observe in the Earth's gravitational field, a hypothetical body of mass comparable to the Earth's would perceptibly cause the Earth to fall toward it, which would feed back into the strength as a function of time of the Earth's gravitational field affecting that body. In short, Einstein's equivalence principle isn't exact, but is an approximation that ignores recoil of the "specified" gravitational field, which sheds light on why general relativity has no clearly delineated native embodiment of conserved four-momentum. Einstein's 1905 relativity of course doesn't have the inexactitudes he unwittingly built into GR, so it is natural to explore a Lorentz-covariant gravitational theory patterned directly on electromagnetism, wherein a system's zero-divergence overall stress-energy, including all gravitational fee...
Extreme eigenvalues of sample covariance and correlation matrices
DEFF Research Database (Denmark)
Heiny, Johannes
This thesis is concerned with asymptotic properties of the eigenvalues of high-dimensional sample covariance and correlation matrices under an infinite fourth moment of the entries. In the first part, we study the joint distributional convergence of the largest eigenvalues of the sample covariance...... of the problem at hand. We develop a theory for the point process of the normalized eigenvalues of the sample covariance matrix in the case where rows and columns of the data are linearly dependent. Based on the weak convergence of this point process we derive the limit laws of various functionals...... of the eigenvalues. In the second part, we show that the largest and smallest eigenvalues of a highdimensional sample correlation matrix possess almost sure non-random limits if the truncated variance of the entry distribution is “almost slowly varying”, a condition we describe via moment properties of self...
Data Covariances from R-Matrix Analyses of Light Nuclei
Energy Technology Data Exchange (ETDEWEB)
Hale, G.M., E-mail: ghale@lanl.gov; Paris, M.W.
2015-01-15
After first reviewing the parametric description of light-element reactions in multichannel systems using R-matrix theory and features of the general LANL R-matrix analysis code EDA, we describe how its chi-square minimization procedure gives parameter covariances. This information is used, together with analytically calculated sensitivity derivatives, to obtain cross section covariances for all reactions included in the analysis by first-order error propagation. Examples are given of the covariances obtained for systems with few resonances ({sup 5}He) and with many resonances ({sup 13}C ). We discuss the prevalent problem of this method leading to cross section uncertainty estimates that are unreasonably small for large data sets. The answer to this problem appears to be using parameter confidence intervals in place of standard errors.
Covariance in models of loop quantum gravity: Spherical symmetry
Bojowald, Martin; Reyes, Juan D
2015-01-01
Spherically symmetric models of loop quantum gravity have been studied recently by different methods that aim to deal with structure functions in the usual constraint algebra of gravitational systems. As noticed by Gambini and Pullin, a linear redefinition of the constraints (with phase-space dependent coefficients) can be used to eliminate structure functions, even Abelianizing the more-difficult part of the constraint algebra. The Abelianized constraints can then easily be quantized or modified by putative quantum effects. As pointed out here, however, the method does not automatically provide a covariant quantization, defined as an anomaly-free quantum theory with a classical limit in which the usual (off-shell) gauge structure of hypersurface deformations in space-time appears. The holonomy-modified vacuum theory based on Abelianization is covariant in this sense, but matter theories with local degrees of freedom are not. Detailed demonstrations of these statements show complete agreement with results of ...
Non-linear wave loads and ship responses by a time-domain strip theory
DEFF Research Database (Denmark)
Xia, Jinzhu; Wang, Zhaohui; Jensen, Jørgen Juncher
1998-01-01
A non-linear time-domain strip theory for vertical wave loads and ship responses is presented. The theory is generalized from a rigorous linear time-domain strip theory representation. The hydrodynamic memory effect due to the free surface is approximated by a higher order differential equation. ...... and are systematically compared with the experimental results given by Watanabe et al. (1989, J. Soc. Naval Architects Japan, 166) and O’Dea et al. (1992, Proc. 19th Symp. on Naval Hydrodynamics). The agreement between the present predictions and the experiments is very encouraging....
First-order derivative couplings between excited states from adiabatic TDDFT response theory.
Ou, Qi; Bellchambers, Gregory D; Furche, Filipp; Subotnik, Joseph E
2015-02-14
We present a complete derivation of derivative couplings between excited states in the framework of adiabatic time-dependent density functional response theory. Explicit working equations are given and the resulting derivative couplings are compared with derivative couplings from a pseudo-wavefunction ansatz. For degenerate excited states, i.e., close to a conical intersection (CI), the two approaches are identical apart from an antisymmetric overlap term. However, if the difference between two excitation energies equals another excitation energy, the couplings from response theory exhibit an unphysical divergence. This spurious behavior is a result of the adiabatic or static kernel approximation of time-dependent density functional theory leading to an incorrect analytical structure of the quadratic response function. Numerical examples for couplings close to a CI and for well-separated electronic states are given.
Competing risks and time-dependent covariates
DEFF Research Database (Denmark)
Cortese, Giuliana; Andersen, Per K
2010-01-01
Time-dependent covariates are frequently encountered in regression analysis for event history data and competing risks. They are often essential predictors, which cannot be substituted by time-fixed covariates. This study briefly recalls the different types of time-dependent covariates...
Ranger, Jochen; Kuhn, Jorg-Tobias
2012-01-01
Research findings indicate that response times in personality scales are related to the trait level according to the so-called speed-distance hypothesis. Against this background, Ferrando and Lorenzo-Seva proposed a latent trait model for the responses and response times in a test. The model consists of two components, a standard item response…
Parametric methods for estimating covariate-dependent reference limits.
Virtanen, Arja; Kairisto, Veli; Uusipaikka, Esa
2004-01-01
Age-specific reference limits are required for many clinical laboratory measurements. Statistical assessment of calculated intervals must be performed to obtain reliable reference limits. When parametric, covariate-dependent limits are derived, normal distribution theory usually is applied due to its mathematical simplicity and relative ease of fitting. However, it is not always possible to transform data and achieve a normal distribution. Therefore, models other than those based on normal distribution theory are needed. Generalized linear model theory offers one such alternative. Regardless of the statistical model used, the assumptions behind the model should always be examined.
Leading order covariant chiral nucleon-nucleon interaction
Ren, Xiu-Lei; Geng, Li-Sheng; Long, Bing-Wei; Ring, Peter; Meng, Jie
2016-01-01
Motivated by the successes of relativistic theories in studies of atomic/molecular and nuclear systems and the strong need for a covariant chiral force in relativistic nuclear structure studies, we develop a new covariant scheme to construct the nucleon-nucleon interaction in the framework of chiral effective field theory. The chiral interaction is formulated up to leading order with a covariant power counting and a Lorentz invariant chiral Lagrangian. We find that the covariant scheme induces all the six invariant spin operators needed to describe the nuclear force, which are also helpful to achieve cutoff independence for certain partial waves. A detailed investigation of the partial wave potentials shows a better description of the scattering phase shifts with low angular momenta than the leading order Weinberg approach. Particularly, the description of the $^1S_0$, $^3P_0$, and $^1P_1$ partial waves is similar to that of the next-to-leading order Weinberg approach. Our study shows that the relativistic fr...
Calculation of response of Chinese hamster cells to ions based on track structure theory
Institute of Scientific and Technical Information of China (English)
LiuXiao－Wei; ZhangChun－Xiang
1997-01-01
Considering biological cells as single target two-hit detectors,an analytic formula to calculate the response of cells to ions is developed based on track structure theory.In the calculation,the splitting deposition energy between ion kill mode and γ kill mode is not used.The results of calculation are in agreement with the experimental data for response of Chinese hamster cells,whose response to γ rays can be described by the response function of single target two hit detector to ions.
Covariance Evaluation Methodology for Neutron Cross Sections
Energy Technology Data Exchange (ETDEWEB)
Herman,M.; Arcilla, R.; Mattoon, C.M.; Mughabghab, S.F.; Oblozinsky, P.; Pigni, M.; Pritychenko, b.; Songzoni, A.A.
2008-09-01
We present the NNDC-BNL methodology for estimating neutron cross section covariances in thermal, resolved resonance, unresolved resonance and fast neutron regions. The three key elements of the methodology are Atlas of Neutron Resonances, nuclear reaction code EMPIRE, and the Bayesian code implementing Kalman filter concept. The covariance data processing, visualization and distribution capabilities are integral components of the NNDC methodology. We illustrate its application on examples including relatively detailed evaluation of covariances for two individual nuclei and massive production of simple covariance estimates for 307 materials. Certain peculiarities regarding evaluation of covariances for resolved resonances and the consistency between resonance parameter uncertainties and thermal cross section uncertainties are also discussed.
Using item response theory models to evaluate the Practice Environment Scale.
Raju, Dheeraj; Su, Xiaogang; Patrician, Patricia A
2014-01-01
The purpose of this article is to introduce different types of item response theory models and to demonstrate their usefulness by evaluating the Practice Environment Scale. Item response theory models such as constrained and unconstrained graded response model, partial credit model, Rasch model, and one-parameter logistic model are demonstrated. The Akaike information criterion (AIC) and Bayesian information criterion (BIC) indices are used as model selection criterion. The unconstrained graded response and partial credit models indicated the best fit for the data. Almost all items in the instrument performed well. Although most of the items strongly measure the construct, there are a few items that could be eliminated without substantially altering the instrument. The analysis revealed that the instrument may function differently when administered to different unit types.
What Information Theory Says About Best Response and About Binding Contracts
Wolpert, David H.
2004-01-01
Product Distribution (PD) theory is the information-theoretic extension of conventional full- rationality game theory to bounded rational games. Here PD theory is used to investigate games in which the players use bounded rational best-response strategies. This investigation illuminates how to determine the optimal organization chart for a corporation, or more generally how to order the sequence of moves of the players / employees so as to optimize an overall objective function. It is then shown that in the continuum-time limit, bounded rational best response games result in a variant of the replicator dynamics of evolutionary game theory. This variant is then investigated for team games, in which the players share the same utility function, by showing that such continuum- limit bounded rational best response is identical to Newton-Raphson iterative optimization of the shared utility function. Next PD theory is used to investigate changing the coordinate system of the game, i.e., changing the mapping from the joint move of the players to the arguments in the utility functions. Such a change couples those arguments, essentially by making each players move be an offered binding contract.
Theory of negative-refractive-index response of double-fishnet structures.
Mary, A; Rodrigo, Sergio G; Garcia-Vidal, F J; Martin-Moreno, L
2008-09-05
A theory is presented of the negative refractive index observed in the so-called double-fishnet structures. We find that the electrical response of these structures is dominated by the cutoff frequency of the hole waveguide whereas the resonant magnetic response is due to the excitation of gap surface plasmon polaritons propagating along the dielectric slab. Associated with this origin, we show how the negative refractive index in these metamaterials presents strong dispersion with the parallel momentum of the incident light.
DEFF Research Database (Denmark)
Frederiksen, Claus Strue
2010-01-01
This article examines the relation between policies concerning Corporate Social Responsibility (CSR) and philosophical moral theories. The objective is to determine which moral theories form the basis for CSR policies. Are they based on ethical egoism, libertarianism, utilitarianism or some kind...... philosophical moral theories and the ethical content of business activities have mainly concentrated on the ethical decision-making of managers. Some of the most prominent investigations in that regard propose that managers mainly act in accordance with utilitarian moral theory (Fritzsche, D. J. and H. Becker......: 1984, Academy of Management Journal27(1), 166–175; Premeaux, S. and W. Mony: 1993, Journal of Business Ethics12, 349–357; Premeaux, S.: 2004, Journal of Business Ethics52, 269–278). I conclude that CSR policies are not based on utilitarian thinking, but instead, on some kind of common-sense morality...
Multi-Sensory Cognitive Learning as Facilitated in a Multimedia Tutorial for Item Response Theory
Directory of Open Access Journals (Sweden)
Chong Ho Yu
2007-08-01
Full Text Available The objective of this paper is to introduce an application of multi-sensory cognitive learning theory into the development of a multimedia tutorial for Item Response Theory. The cognitive multimedia theory suggests that the visual and auditory material should be presented simultaneously to reinforce the retention of learned materials. A computer-assisted module is carefully designed based upon the preceding theory and also an experiment was conducted to examine the effect of audio types (human audio, computer audio, and no audio on learner performance measured by an objective test. It was found that while there is no significant performance gap between the human audio and the no audio group, the two groups substantively outperform the computer audio group. A plausible explanation is that un-natural audio requires additional cognitive power to process the information and thus this distraction affects the performance.
Trenholm, Susan; Ferlie, Ewan
2013-09-01
We employ complexity theory to analyse the English National Health Service (NHS)'s organisational response to resurgent tuberculosis across London. Tennison (2002) suggests that complexity theory could fruitfully explore a healthcare system's response to this complex and emergent phenomenon: we explore this claim here. We also bring in established New Public Management principles to enhance our empirical analysis, which is based on data collected between late 2009 and mid-2011. We find that the operation of complexity theory based features, especially self-organisation, are significantly impacted by the macro context of a New Public Management-based regime which values control, measurement and risk management more than innovation, flexibility and lateral system building. We finally explore limitations and suggest perspectives for further research.
Directory of Open Access Journals (Sweden)
Intan Meutia
2010-12-01
Full Text Available This research aims to develop the concept and characteristics of social responsibility disclosure and items for the social responsibility disclosure of Islamic banks. This research was conducted based on the critical paradigm by using Habermas’s Theory of Communication Action extended to spirituality in understanding social reality. This study also uses Shari’ah Enterprise Theory to analyze and to produce the concept of social responsibility disclosure for Islamic banks. Analysis was conducted on the annual reports of three Islamic banks in Indonesia, Bank Mega Syariah, Bank Syariah Mandiri and Bank Muamalat Indonesia. Interviews with stakeholders, including direct and indirect stakeholders were also conducted. Spiritual values were found during the research. These values are sharing, rahmatan lil alamin and maslaha. These values are used as guidance in developing items of social responsibility disclosure. Furthermore, a concept of social responsibility disclosure is derived based on the Shari’ah Enterprise Theory. This research proposes a form of social responsibility disclosure for Islamic banks that show efforts to meet vertical accountability to God, and horizontal accountability to people and environment, as well as to consider the material and spiritual needs of stakeholders and to disclose information both qualitatively and quantitatively.
Jong, de Martijn G.; Steenkamp, Jan-Benedict E.M.; Fox, Jean-Paul; Baumgartner, Hans
2008-01-01
Extreme response style (ERS) is an important threat to the validity of survey-based marketing research. In this article, the authors present a new item response theory–based model for measuring ERS. This model contributes to the ERS literature in two ways. First, the method improves on existing proc
Chao, Yu-Long
2012-01-01
Using different measures of self-reported and other-reported environmental behaviour (EB), two important theoretical models explaining EB--Hines, Hungerford and Tomera's model of responsible environmental behaviour (REB) and Ajzen's theory of planned behaviour (TPB)--were compared regarding the fit between model and data, predictive ability,…
Novakovic, A.M.; Krekels, E.H.; Munafo, A.; Ueckert, S.; Karlsson, M.O.
2016-01-01
In this study, we report the development of the first item response theory (IRT) model within a pharmacometrics framework to characterize the disease progression in multiple sclerosis (MS), as measured by Expanded Disability Status Score (EDSS). Data were collected quarterly from a 96-week phase III
Ten Holt, J.C.; van Duijn, M.A.J.; Boomsma, A.
2010-01-01
In scale construction and evaluation, factor analysis (FA) and item response theory (IRT) are two methods frequently used to determine whether a set of items reliably measures a latent variable. In a review of 41 published studies we examined which methodology – FA or IRT – was used, and what resear
Reader-Response Theory and Instructors' Holistic Evaluating in and out of Their Fields.
Anderson, Larry; And Others
1994-01-01
Claims that holistic scoring for schoolwide assessment of writing proficiency is influenced by the disciplines represented by the faculty readers. Describes in detail the findings of a study designed to measure reader bias in evaluation, a phenomenon suggested by reader-response theory. (HB)
Classification Consistency and Accuracy for Complex Assessments Using Item Response Theory
Lee, Won-Chan
2010-01-01
In this article, procedures are described for estimating single-administration classification consistency and accuracy indices for complex assessments using item response theory (IRT). This IRT approach was applied to real test data comprising dichotomous and polytomous items. Several different IRT model combinations were considered. Comparisons…
Directory of Open Access Journals (Sweden)
Farah Qamar
2016-06-01
Full Text Available Since Socrates’ time, reasoning is considered valuable for the justification of speaker’s belief along with Thomas Aquinas’ testing of his thinking to answer his own thinking. Critical thinking has been part of discussion among the educators for its significance and application for last many decades. Many educators have conducted researches on the assessment of critical thinking within a domain or across the domain in order to test students’ critical thinking skills and its effect on their learning. Similarly, critical thinking is highly valuable for the study of literature as it explicitly asked for learners’ beliefs, perceptions, and judgments in order to remove the ambiguity of thought. Perfection of thought can be achieved with the use of critical thinking skills while training of mind needs interaction between literary text and the reader as literature has the capacity to achieve mental traits specified to critical thinking. Accordingly, this report presents a relationship between critical thinking skills and English literature study along with reader response theory techniques considering that without the use of critical thinking skills and reader response theory, study of literature is haphazard hence for the application of reader response theory, literary text is inevitable. In essence, I aim to highlight the effectiveness of critical thinking skills for the study of literature while emphasizing the significance of reader response theory which is also inevitable for the study of literature and for the use of critical thinking skills.
Comparison of Item Response Theory and Thurstone Methods of Vertical Scaling.
Burket, George R.; Yen, Wendy M.
1997-01-01
Using simulated data modeled after real tests, a Thurstone method (L. Thurstone, 1925 and later) and three-parameter item response theory were compared for vertical scaling. Neither procedure produced artificial scale shrinkage, and both produced modest scale expansion for one simulated condition. (SLD)
A Comparison of Developmental Scales Based on Thurstone Methods and Item Response Theory.
Williams, Valerie S. L.; Pommerich, Mary; Thissen, David
1998-01-01
Created a developmental scale for the North Carolina End-of-Grade Mathematics Tests using a subset of identical test forms administered to adjacent grade levels with Thurstone scaling and Item Response Theory methods. Discusses differences in patterns produced. (Author/SLD)
Bolkan, San; Goodboy, Alan K.
2016-01-01
Protection motivation theory (PMT) explains people's adaptive behavior in response to personal threats. In this study, PMT was used to predict rhetorical dissent episodes related to 210 student reports of perceived classroom problems. In line with theoretical predictions, a moderated moderation analysis revealed that students were likely to voice…
Can a Multidimensional Test Be Evaluated with Unidimensional Item Response Theory?
Wiberg, Marie
2012-01-01
The aim of this study was to evaluate possible consequences of using unidimensional item response theory (UIRT) on a multidimensional college admission test. The test consists of 5 subscales and can be divided into two sections, that is, it can be considered both as a unidimensional and a multidimensional test. The test was examined with both UIRT…
Bolkan, San; Goodboy, Alan K.
2016-01-01
Protection motivation theory (PMT) explains people's adaptive behavior in response to personal threats. In this study, PMT was used to predict rhetorical dissent episodes related to 210 student reports of perceived classroom problems. In line with theoretical predictions, a moderated moderation analysis revealed that students were likely to voice…
An NCME Instructional Module on Item-Fit Statistics for Item Response Theory Models
Ames, Allison J.; Penfield, Randall D.
2015-01-01
Drawing valid inferences from item response theory (IRT) models is contingent upon a good fit of the data to the model. Violations of model-data fit have numerous consequences, limiting the usefulness and applicability of the model. This instructional module provides an overview of methods used for evaluating the fit of IRT models. Upon completing…
The Long-Term Sustainability of Different Item Response Theory Scaling Methods
Keller, Lisa A.; Keller, Robert R.
2011-01-01
This article investigates the accuracy of examinee classification into performance categories and the estimation of the theta parameter for several item response theory (IRT) scaling techniques when applied to six administrations of a test. Previous research has investigated only two administrations; however, many testing programs equate tests…
Optimal and Most Exact Confidence Intervals for Person Parameters in Item Response Theory Models
Doebler, Anna; Doebler, Philipp; Holling, Heinz
2013-01-01
The common way to calculate confidence intervals for item response theory models is to assume that the standardized maximum likelihood estimator for the person parameter [theta] is normally distributed. However, this approximation is often inadequate for short and medium test lengths. As a result, the coverage probabilities fall below the given…
Chao, Yu-Long
2012-01-01
Using different measures of self-reported and other-reported environmental behaviour (EB), two important theoretical models explaining EB--Hines, Hungerford and Tomera's model of responsible environmental behaviour (REB) and Ajzen's theory of planned behaviour (TPB)--were compared regarding the fit between model and data, predictive ability,…
Understanding responses to feedback: the potential and limitations of regulatory focus theory.
Watling, C.; Driessen, E.; Vleuten, C.P.M. van der; Vanstone, M.; Lingard, L.
2012-01-01
OBJECTIVES: Regulatory focus theory posits the existence of two systems of self-regulation underlying human motivation: promotion focus, which is concerned with aspirations and accomplishments, and prevention focus, which is concerned with obligations and responsibilities. It has been proposed that
Bayesian modeling of measurement error in predictor variables using item response theory
Fox, Gerardus J.A.; Glas, Cornelis A.W.
2000-01-01
This paper focuses on handling measurement error in predictor variables using item response theory (IRT). Measurement error is of great important in assessment of theoretical constructs, such as intelligence or the school climate. Measurement error is modeled by treating the predictors as unobserved
Optimal and Most Exact Confidence Intervals for Person Parameters in Item Response Theory Models
Doebler, Anna; Doebler, Philipp; Holling, Heinz
2013-01-01
The common way to calculate confidence intervals for item response theory models is to assume that the standardized maximum likelihood estimator for the person parameter [theta] is normally distributed. However, this approximation is often inadequate for short and medium test lengths. As a result, the coverage probabilities fall below the given…
Evaluation of Northwest University, Kano Post-UTME Test Items Using Item Response Theory
Bichi, Ado Abdu; Hafiz, Hadiza; Bello, Samira Abdullahi
2016-01-01
High-stakes testing is used for the purposes of providing results that have important consequences. Validity is the cornerstone upon which all measurement systems are built. This study applied the Item Response Theory principles to analyse Northwest University Kano Post-UTME Economics test items. The developed fifty (50) economics test items was…
Bayesian modeling of measurement error in predictor variables using item response theory
Fox, Jean-Paul; Glas, Cees A.W.
2000-01-01
This paper focuses on handling measurement error in predictor variables using item response theory (IRT). Measurement error is of great important in assessment of theoretical constructs, such as intelligence or the school climate. Measurement error is modeled by treating the predictors as unobserved
Bayesian modeling of measurement error in predictor variables using item response theory
Fox, Jean-Paul; Glas, Cees A.W.
2003-01-01
It is shown that measurement error in predictor variables can be modeled using item response theory (IRT). The predictor variables, that may be defined at any level of an hierarchical regression model, are treated as latent variables. The normal ogive model is used to describe the relation between t
Quantum corrections for the cubic Galileon in the covariant language
Saltas, Ippocratis D.; Vitagliano, Vincenzo
2017-05-01
We present for the first time an explicit exposition of quantum corrections within the cubic Galileon theory including the effect of quantum gravity, in a background- and gauge-invariant manner, employing the field-reparametrisation approach of the covariant effective action at 1-loop. We show that the consideration of gravitational effects in combination with the non-linear derivative structure of the theory reveals new interactions at the perturbative level, which manifest themselves as higher-operators in the associated effective action, which' relevance is controlled by appropriate ratios of the cosmological vacuum and the Galileon mass scale. The significance and concept of the covariant approach in this context is discussed, while all calculations are explicitly presented.
Historical Hamiltonian Dynamics: symplectic and covariant
Lachieze-Rey, M
2016-01-01
This paper presents a "historical" formalism for dynamical systems, in its Hamiltonian version (Lagrangian version was presented in a previous paper). It is universal, in the sense that it applies equally well to time dynamics and to field theories on space-time. It is based on the notion of (Hamiltonian) histories, which are sections of the (extended) phase space bundle. It is developed in the space of sections, in contradistinction with the usual formalism which works in the bundle manifold. In field theories, the formalism remains covariant and does not require a spitting of space-time. It considers space-time exactly in the same manner than time in usual dynamics, both being particular cases of the evolution domain. It applies without modification when the histories (the fields) are forms rather than scalar functions, like in electromagnetism or in tetrad general relativity. We develop a differential calculus in the infinite dimensional space of histories. It admits a (generalized) symplectic form which d...
Schwinger mechanism in linear covariant gauges
Aguilar, A C; Papavassiliou, J
2016-01-01
In this work we explore the applicability of a special gluon mass generating mechanism in the context of the linear covariant gauges. In particular, the implementation of the Schwinger mechanism in pure Yang-Mills theories hinges crucially on the inclusion of massless bound-state excitations in the fundamental nonperturbative vertices of the theory. The dynamical formation of such excitations is controlled by a homogeneous linear Bethe-Salpeter equation, whose nontrivial solutions have been studied only in the Landau gauge. Here, the form of this integral equation is derived for general values of the gauge-fixing parameter, under a number of simplifying assumptions that reduce the degree of technical complexity. The kernel of this equation consists of fully-dressed gluon propagators, for which recent lattice data are used as input, and of three-gluon vertices dressed by a single form factor, which is modelled by means of certain physically motivated Ans\\"atze. The gauge-dependent terms contributing to this ke...
Covariate-adjusted confidence interval for the intraclass correlation coefficient.
Shoukri, Mohamed M; Donner, Allan; El-Dali, Abdelmoneim
2013-09-01
A crucial step in designing a new study is to estimate the required sample size. For a design involving cluster sampling, the appropriate sample size depends on the so-called design effect, which is a function of the average cluster size and the intracluster correlation coefficient (ICC). It is well-known that under the framework of hierarchical and generalized linear models, a reduction in residual error may be achieved by including risk factors as covariates. In this paper we show that the covariate design, indicating whether the covariates are measured at the cluster level or at the within-cluster subject level affects the estimation of the ICC, and hence the design effect. Therefore, the distinction between these two types of covariates should be made at the design stage. In this paper we use the nested-bootstrap method to assess the accuracy of the estimated ICC for continuous and binary response variables under different covariate structures. The codes of two SAS macros are made available by the authors for interested readers to facilitate the construction of confidence intervals for the ICC. Moreover, using Monte Carlo simulations we evaluate the relative efficiency of the estimators and evaluate the accuracy of the coverage probabilities of a 95% confidence interval on the population ICC. The methodology is illustrated using a published data set of blood pressure measurements taken on family members.
Sparse reduced-rank regression with covariance estimation
Chen, Lisha
2014-12-08
Improving the predicting performance of the multiple response regression compared with separate linear regressions is a challenging question. On the one hand, it is desirable to seek model parsimony when facing a large number of parameters. On the other hand, for certain applications it is necessary to take into account the general covariance structure for the errors of the regression model. We assume a reduced-rank regression model and work with the likelihood function with general error covariance to achieve both objectives. In addition we propose to select relevant variables for reduced-rank regression by using a sparsity-inducing penalty, and to estimate the error covariance matrix simultaneously by using a similar penalty on the precision matrix. We develop a numerical algorithm to solve the penalized regression problem. In a simulation study and real data analysis, the new method is compared with two recent methods for multivariate regression and exhibits competitive performance in prediction and variable selection.
The Photon Wavefunction: a covariant formulation and equivalence with QED
Tamburini, Fabrizio; Vicino, Denise
2008-01-01
We discuss the limits of the photon wavefunction (PWF) formalism, which is experiencing a revival in these days from the new practical applications in photonics and quantum optics. We build a Dirac-like equation for the PWF written in a manifestly covariant form and show that, in presence of charged matter fields, it reproduces the standard formulation of (classical) Electrodinamics. This shows the inconsistency of the attempts to construct a quantum theory of interacting photons, based on th...
Covariant GNS Representation for C*-Dynamical Systems
Pandiscia, Carlo
2012-01-01
We extend the covariant GNS representation of Niculescu, Str\\"oh and Zsid\\'o for C*-dynamical systems with time-evolution of the system (dynamics) a homomorphism of C*-algebras, to any dynamical systems, where the dynamics is an unital completely positive map. We give also an overview on its application to the reversible dilation theory as formulated by B. Kummerer.
Covariant Quantization of the Brink-Schwarz Superparticle
Grassi, P A; Porrati, Massimo
2001-01-01
The quantization of the Brink-Schwarz-Casalbuoni superparticle is performed in an explicitly covariant way using the antibracket formalism. Since an infinite number of ghost fields are required, within a suitable off-shell twistor-like formalism, we are able to fix the gauge of each ghost sector without modifying the physical content of the theory. The computation reveals that the antibracket cohomology contains only the physical degrees of freedom.
Density matrix perturbation theory for magneto-optical response of periodic insulators
Lebedeva, Irina; Tokatly, Ilya; Rubio, Angel
2015-03-01
Density matrix perturbation theory offers an ideal theoretical framework for the description of response of solids to arbitrary electromagnetic fields. In particular, it allows to consider perturbations introduced by uniform electric and magnetic fields under periodic boundary conditions, though the corresponding potentials break the translational invariance of the Hamiltonian. We have implemented the density matrix perturbation theory in the open-source Octopus code on the basis of the efficient Sternheimer approach. The procedures for responses of different order to electromagnetic fields, including electric polarizability, orbital magnetic susceptibility and magneto-optical response, have been developed and tested by comparison with the results for finite systems and for wavefunction-based perturbation theory, which is already available in the code. Additional analysis of the orbital magneto-optical response is performed on the basis of analytical models. Symmetry limitations to observation of the magneto-optical response are discussed. The financial support from the Marie Curie Fellowship PIIF-GA-2012-326435 (RespSpatDisp) is gratefully acknowledged.
Ferrighi, Lara; Frediani, Luca; Ruud, Kenneth
2010-01-01
The theory and an implementation of the solvent contribution to the cubic response function for the polarizable continuum model for multiconfigurational self-consistent field wave functions is presented. The excited-state polarizability of benzene, para-nitroaniline, and nitrobenzene has been obtained from the double residue of the cubic response function calculated in the presence of an acetonitrile and dioxane solvent. The calculated excited-state polarizabilities are compared to results obtained from the linear response function of the explicitly optimized excited states.
Predicting Climate Change using Response Theory: Global Averages and Spatial Patterns
Lucarini, Valerio; Ragone, Francesco
2015-01-01
The provision of accurate methods for predicting the climate response to anthropogenic and natural forcings is a key contemporary scientific challenge. Using a simplified and efficient open-source general circulation model of the atmosphere featuring O($10^5$) degrees of freedom, we show how it is possible to approach such a problem using nonequilibrium statistical mechanics. Response theory allows one to practically compute the time-dependent measure supported on the pullback attractor of the climate system, whose dynamics is non-autonomous as a result of time-dependent forcings. We propose a simple yet efficient method for predicting - at any lead time and in an ensemble sense - the change in climate properties resulting from increase in the concentration of CO$_2$ using test perturbation model runs. We assess strengths and limitations of the response theory in predicting the changes in the globally averaged values of surface temperature and of the yearly total precipitation, as well as their spatial patter...
Latent Variable Modelling and Item Response Theory Analyses in Marketing Research
Directory of Open Access Journals (Sweden)
Brzezińska Justyna
2016-12-01
Full Text Available Item Response Theory (IRT is a modern statistical method using latent variables designed to model the interaction between a subject’s ability and the item level stimuli (difficulty, guessing. Item responses are treated as the outcome (dependent variables, and the examinee’s ability and the items’ characteristics are the latent predictor (independent variables. IRT models the relationship between a respondent’s trait (ability, attitude and the pattern of item responses. Thus, the estimation of individual latent traits can differ even for two individuals with the same total scores. IRT scores can yield additional benefits and this will be discussed in detail. In this paper theory and application with R software with the use of packages designed for modelling IRT will be presented.
Orbital-motion-limited theory of dust charging and plasma response
Tang, Xian-Zhu
2015-01-01
The foundational theory for dusty plasmas is the dust charging theory that provides the dust potential and charge arising from the dust interaction with a plasma. The most widely used dust charging theory for negatively charged dust particles is the so-called orbital motion limited (OML) theory, which predicts the dust potential and heat collection accurately for a variety of applications, but was previously found to be incapable of evaluating the dust charge and plasma response in any situation. Here we report a revised OML formulation that is able to predict the plasma response and hence the dust charge. Numerical solutions of the new OML model show that the widely-used Whipple approximation of dust charge-potential relationship agrees with OML theory in the limit of small dust radius compared with plasma Debye length, but incurs large (order-unity) deviation from the OML prediction when the dust size becomes comparable with or larger than plasma Debye length. This latter case is expected for the important ...
Yeager, David S; Lee, Hae Yeon; Jamieson, Jeremy P
2016-08-01
This research integrated implicit theories of personality and the biopsychosocial model of challenge and threat, hypothesizing that adolescents would be more likely to conclude that they can meet the demands of an evaluative social situation when they were taught that people have the potential to change their socially relevant traits. In Study 1 (N = 60), high school students were assigned to an incremental-theory-of-personality or a control condition and then given a social-stress task. Relative to control participants, incremental-theory participants exhibited improved stress appraisals, more adaptive neuroendocrine and cardiovascular responses, and better performance outcomes. In Study 2 (N = 205), we used a daily-diary intervention to test high school students' stress reactivity outside the laboratory. Threat appraisals (Days 5-9 after intervention) and neuroendocrine responses (Days 8 and 9 after intervention only) were unrelated to the intensity of daily stressors when adolescents received the incremental-theory intervention. Students who received the intervention also had better grades over freshman year than those who did not. These findings offer new avenues for improving theories of adolescent stress and coping.
Linear-response time-dependent density-functional theory with pairing fields.
Peng, Degao; van Aggelen, Helen; Yang, Yang; Yang, Weitao
2014-05-14
Recent development in particle-particle random phase approximation (pp-RPA) broadens the perspective on ground state correlation energies [H. van Aggelen, Y. Yang, and W. Yang, Phys. Rev. A 88, 030501 (2013), Y. Yang, H. van Aggelen, S. N. Steinmann, D. Peng, and W. Yang, J. Chem. Phys. 139, 174110 (2013); D. Peng, S. N. Steinmann, H. van Aggelen, and W. Yang, J. Chem. Phys. 139, 104112 (2013)] and N ± 2 excitation energies [Y. Yang, H. van Aggelen, and W. Yang, J. Chem. Phys. 139, 224105 (2013)]. So far Hartree-Fock and approximated density-functional orbitals have been utilized to evaluate the pp-RPA equation. In this paper, to further explore the fundamentals and the potential use of pairing matrix dependent functionals, we present the linear-response time-dependent density-functional theory with pairing fields with both adiabatic and frequency-dependent kernels. This theory is related to the density-functional theory and time-dependent density-functional theory for superconductors, but is applied to normal non-superconducting systems for our purpose. Due to the lack of the proof of the one-to-one mapping between the pairing matrix and the pairing field for time-dependent systems, the linear-response theory is established based on the representability assumption of the pairing matrix. The linear response theory justifies the use of approximated density-functionals in the pp-RPA equation. This work sets the fundamentals for future density-functional development to enhance the description of ground state correlation energies and N ± 2 excitation energies.
Directory of Open Access Journals (Sweden)
Hao Guo
2015-01-01
Full Text Available Recent experimental progress allows for exploring some important physical quantities of ultracold Fermi gases, such as the compressibility, spin susceptibility, viscosity, optical conductivity, and spin diffusivity. Theoretically, these quantities can be evaluated from suitable linear response theories. For BCS superfluid, it has been found that the gauge invariant linear response theories can be fully consistent with some stringent consistency constraints. When the theory is generalized to stronger than BCS regime, one may meet serious difficulties to satisfy the gauge invariance conditions. In this paper, we try to construct density and spin linear response theories which are formally gauge invariant for a Fermi gas undergoing BCS-Bose-Einstein Condensation (BEC crossover, especially below the superfluid transition temperature Tc. We adapt a particular t-matrix approach which is close to the G0G formalism to incorporate noncondensed pairing in the normal state. We explicitly show that the fundamental constraints imposed by the Ward identities and Q-limit Ward identity are indeed satisfied.
Gauge-invariant theories of linear response for strongly correlated superconductors
Boyack, Rufus; Anderson, Brandon M.; Wu, Chien-Te; Levin, K.
2016-09-01
We present a diagrammatic theory for determining consistent electromagnetic response functions in strongly correlated fermionic superfluids. While a gauge-invariant electromagnetic response is well understood at the BCS level, a treatment of correlations beyond BCS theory requires extending this theoretical formalism. The challenge in such systems is to maintain gauge invariance, while simultaneously incorporating additional self-energy terms arising from strong correlation effects. Central to our approach is the application of the Ward-Takahashi identity, which introduces collective mode contributions in the response functions and guarantees that the f -sum rule is satisfied. We outline a powerful method, which determines these collective modes in the presence of correlation effects and in a manner compatible with gauge invariance. Since this method is based on fundamental aspects of quantum field theory, the underlying principles are broadly applicable to strongly correlated superfluids. As an illustration of the technique, we apply it to a simple class of theoretical models that contain a frequency-independent order parameter. These models include BCS-BEC crossover theories of the ultracold Fermi gases, along with models specifically associated with the high-Tc cuprates. Finally, as an alternative approach, we contrast with the path integral formalism. Here, the calculation of gauge-invariant response appears more straightforward. However, the collective modes introduced are those of strict BCS theory, without any modification from additional correlations. As the path integral simultaneously addresses electrodynamics and thermodynamics, we emphasize that it should be subjected to a consistency test beyond gauge invariance, namely that of the compressibility sum rule. We show how this sum rule fails in the conventional path integral approach.
ISSUES IN NEUTRON CROSS SECTION COVARIANCES
Energy Technology Data Exchange (ETDEWEB)
Mattoon, C.M.; Oblozinsky,P.
2010-04-30
We review neutron cross section covariances in both the resonance and fast neutron regions with the goal to identify existing issues in evaluation methods and their impact on covariances. We also outline ideas for suitable covariance quality assurance procedures.We show that the topic of covariance data remains controversial, the evaluation methodologies are not fully established and covariances produced by different approaches have unacceptable spread. The main controversy is in very low uncertainties generated by rigorous evaluation methods and much larger uncertainties based on simple estimates from experimental data. Since the evaluators tend to trust the former, while the users tend to trust the latter, this controversy has considerable practical implications. Dedicated effort is needed to arrive at covariance evaluation methods that would resolve this issue and produce results accepted internationally both by evaluators and users.
Parameter inference with estimated covariance matrices
Sellentin, Elena
2015-01-01
When inferring parameters from a Gaussian-distributed data set by computing a likelihood, a covariance matrix is needed that describes the data errors and their correlations. If the covariance matrix is not known a priori, it may be estimated and thereby becomes a random object with some intrinsic uncertainty itself. We show how to infer parameters in the presence of such an estimated covariance matrix, by marginalising over the true covariance matrix, conditioned on its estimated value. This leads to a likelihood function that is no longer Gaussian, but rather an adapted version of a multivariate $t$-distribution, which has the same numerical complexity as the multivariate Gaussian. As expected, marginalisation over the true covariance matrix improves inference when compared with Hartlap et al.'s method, which uses an unbiased estimate of the inverse covariance matrix but still assumes that the likelihood is Gaussian.
ISSUES IN NEUTRON CROSS SECTION COVARIANCES
Energy Technology Data Exchange (ETDEWEB)
Mattoon, C.M.; Oblozinsky,P.
2010-04-30
We review neutron cross section covariances in both the resonance and fast neutron regions with the goal to identify existing issues in evaluation methods and their impact on covariances. We also outline ideas for suitable covariance quality assurance procedures.We show that the topic of covariance data remains controversial, the evaluation methodologies are not fully established and covariances produced by different approaches have unacceptable spread. The main controversy is in very low uncertainties generated by rigorous evaluation methods and much larger uncertainties based on simple estimates from experimental data. Since the evaluators tend to trust the former, while the users tend to trust the latter, this controversy has considerable practical implications. Dedicated effort is needed to arrive at covariance evaluation methods that would resolve this issue and produce results accepted internationally both by evaluators and users.
Treatment Effects with Many Covariates and Heteroskedasticity
DEFF Research Database (Denmark)
Cattaneo, Matias D.; Jansson, Michael; Newey, Whitney K.
The linear regression model is widely used in empirical work in Economics. Researchers often include many covariates in their linear model specification in an attempt to control for confounders. We give inference methods that allow for many covariates and heteroskedasticity. Our results are obtai......The linear regression model is widely used in empirical work in Economics. Researchers often include many covariates in their linear model specification in an attempt to control for confounders. We give inference methods that allow for many covariates and heteroskedasticity. Our results...... then propose a new heteroskedasticity consistent standard error formula that is fully automatic and robust to both (conditional) heteroskedasticity of unknown form and the inclusion of possibly many covariates. We apply our findings to three settings: (i) parametric linear models with many covariates, (ii...
Eigenvalue variance bounds for covariance matrices
Dallaporta, Sandrine
2013-01-01
This work is concerned with finite range bounds on the variance of individual eigenvalues of random covariance matrices, both in the bulk and at the edge of the spectrum. In a preceding paper, the author established analogous results for Wigner matrices and stated the results for covariance matrices. They are proved in the present paper. Relying on the LUE example, which needs to be investigated first, the main bounds are extended to complex covariance matrices by means of the Tao, Vu and Wan...
Covariant effective action for a Galilean invariant quantum Hall system
Geracie, Michael; Prabhu, Kartik; Roberts, Matthew M.
2016-09-01
We construct effective field theories for gapped quantum Hall systems coupled to background geometries with local Galilean invariance i.e. Bargmann spacetimes. Along with an electromagnetic field, these backgrounds include the effects of curved Galilean spacetimes, including torsion and a gravitational field, allowing us to study charge, energy, stress and mass currents within a unified framework. A shift symmetry specific to single constituent theories constraints the effective action to couple to an effective background gauge field and spin connection that is solved for by a self-consistent equation, providing a manifestly covariant extension of Hoyos and Son's improvement terms to arbitrary order in m.
Variations of cosmic large-scale structure covariance matrices across parameter space
Reischke, Robert; Schäfer, Björn Malte
2016-01-01
The likelihood function for cosmological parameters, given by e.g. weak lensing shear measurements, depends on contributions to the covariance induced by the nonlinear evolution of the cosmic web. As nonlinear clustering to date has only been described by numerical $N$-body simulations in a reliable and sufficiently precise way, the necessary computational costs for estimating those covariances at different points in parameter space are tremendous. In this work we describe the change of the matter covariance and of the weak lensing covariance matrix as a function of cosmological parameters by constructing a suitable basis, where we model the contribution to the covariance from nonlinear structure formation using Eulerian perturbation theory at third order. We show that our formalism is capable of dealing with large matrices and reproduces expected degeneracies and scaling with cosmological parameters in a reliable way. Comparing our analytical results to numerical simulations we find that the method describes...
Mikosch, Jochen; Patchkovskii, Serguei
2013-10-01
We use an analytical theory of noisy Poisson processes, developed in the preceding companion publication, to compare coincidence and covariance measurement approaches in photoelectron and -ion spectroscopy. For non-unit detection efficiencies, coincidence data acquisition (DAQ) suffers from false coincidences. The rate of false coincidences grows quadratically with the rate of elementary ionization events. To minimize false coincidences for rare event outcomes, very low event rates may hence be required. Coincidence measurements exhibit high tolerance to noise introduced by unstable experimental conditions. Covariance DAQ on the other hand is free of systematic errors as long as stable experimental conditions are maintained. In the presence of noise, all channels in a covariance measurement become correlated. Under favourable conditions, covariance DAQ may allow orders of magnitude reduction in measurement times. Finally, we use experimental data for strong-field ionization of 1,3-butadiene to illustrate how fluctuations in experimental conditions can contaminate a covariance measurement, and how such contamination can be detected.
Fukuhara, Hirotaka; Kamata, Akihito
2011-01-01
A differential item functioning (DIF) detection method for testlet-based data was proposed and evaluated in this study. The proposed DIF model is an extension of a bifactor multidimensional item response theory (MIRT) model for testlets. Unlike traditional item response theory (IRT) DIF models, the proposed model takes testlet effects into…
Response Functions for the Two-Dimensional Ultracold Fermi Gas: Dynamical BCS Theory and Beyond
Vitali, Ettore; Shi, Hao; Qin, Mingpu; Zhang, Shiwei
2017-08-01
Response functions are central objects in physics. They provide crucial information about the behavior of physical systems, and they can be directly compared with scattering experiments involving particles such as neutrons or photons. Calculations of such functions starting from the many-body Hamiltonian of a physical system are challenging and extremely valuable. In this paper, we focus on the two-dimensional (2D) ultracold Fermi atomic gas which has been realized experimentally. We present an application of the dynamical BCS theory to obtain response functions for different regimes of interaction strengths in the 2D gas with zero-range attractive interaction. We also discuss auxiliary-field quantum Monte Carlo (AFQMC) methods for the calculation of imaginary time correlations in these dilute Fermi gas systems. Illustrative results are given and comparisons are made between AFQMC and dynamical BCS theory results to assess the accuracy of the latter.
Capturing Abnormal Personality With Normal Personality Inventories: An Item Response Theory Approach
2008-01-01
Correlational and factor-analytic methods indicate that abnormal and normal personality constructs may be tapping the same underlying latent trait. However, they do not systematically demonstrate that measures of abnormal personality capture more extreme ranges of the latent trait than measures of normal range personality. Item Response Theory (IRT) methods, in contrast, do provide this information. In the present study, we use IRT methods to evaluate the range of the latent trait assessed wi...
The theory and practice of regional strategy: a response to Osegowitsch and Sammartino
Alan M Rugman; Alain Verbeke
2008-01-01
We are grateful to Osegowitsch and Sammartino for their critical analysis of our work on the regional and global strategies of multinational enterprises (MNEs). In this response, we demonstrate that changing the quantitative thresholds for classifying MNEs as global vs non-global has no bearing on our earlier conclusions. First, very few global firms exist. Second, scholarly reflection on regional vs global MNE strategy requires substantive extensions of extant international business theory. ...
Mukamel, Shaul
2003-08-01
Computing response functions by following the time evolution of superoperators in Liouville space (whose vectors are ordinary Hilbert space operators) offers an attractive alternative to the diagrammatic perturbative expansion of many-body equilibrium and nonequilibrium Green's functions. The bookkeeping of time ordering is naturally maintained in real (physical) time, allowing the formulation of Wick's theorem for superoperators, giving a factorization of higher order response functions in terms of two fundamental Green's functions. Backward propagations and analytic continuations using artificial times (Keldysh loops and Matsubara contours) are avoided. A generating functional for nonlinear response functions unifies quantum field theory and the classical mode coupling formalism of nonlinear hydrodynamics and may be used for semiclassical expansions. Classical response functions are obtained without the explicit computation of stability matrices.
Pernal, Katarzyna; Giesbertz, Klaas J H
2016-01-01
Recent advances in reduced density matrix functional theory (RDMFT) and linear response time-dependent reduced density matrix functional theory (TD-RDMFT) are reviewed. In particular, we present various approaches to develop approximate density matrix functionals which have been employed in RDMFT. We discuss the properties and performance of most available density matrix functionals. Progress in the development of functionals has been paralleled by formulation of novel RDMFT-based methods for predicting properties of molecular systems and solids. We give an overview of these methods. The time-dependent extension, TD-RDMFT, is a relatively new theory still awaiting practical and generally useful functionals which would work within the adiabatic approximation. In this chapter we concentrate on the formulation of TD-RDMFT response equations and various adiabatic approximations. None of the adiabatic approximations is fully satisfactory, so we also discuss a phase-dependent extension to TD-RDMFT employing the concept of phase-including-natural-spinorbitals (PINOs). We focus on applications of the linear response formulations to two-electron systems, for which the (almost) exact functional is known.
Into the Bulk: A Covariant Approach
Engelhardt, Netta
2016-01-01
I propose a general, covariant way of defining when one region is "deeper in the bulk" than another. This definition is formulated outside of an event horizon (or in the absence thereof) in generic geometries; it may be applied to both points and surfaces, and may be used to compare the depth of bulk points or surfaces relative to a particular boundary subregion or relative to the entire boundary. Using the recently proposed "lightcone cut" formalism, the comparative depth between two bulk points can be determined from the singularity structure of Lorentzian correlators in the dual field theory. I prove that, by this definition, causal wedges of progressively larger regions probe monotonically deeper in the bulk. The definition furthermore matches expectations in pure AdS and in static AdS black holes with isotropic spatial slices, where a well-defined holographic coordinate exists. In terms of holographic RG flow, this new definition of bulk depth makes contact with coarse-graining over both large distances ...
The covariance of GPS coordinates and frames
Energy Technology Data Exchange (ETDEWEB)
Lachieze-Rey, Marc [CNRS APC, UMR 7164 Service d' Astrophysique, CE Saclay, 91191 Gif sur Yvette Cedex (France)
2006-05-21
We explore, in the general relativistic context, the properties of the recently introduced global positioning system (GPS) coordinates, as well as those of the associated frames and coframes that they define. We show that they are covariant and completely independent of any observer. We show that standard spectroscopic and astrometric observations allow any observer to measure (i) the values of the GPS coordinates at his position (ii) the components of his 4-velocity and (iii) the components of the metric in the GPS frame. This provides this system with a unique value both for conceptual discussion (no frame dependence) and for practical use (involved quantities are directly measurable): localization, motion monitoring, astrometry, cosmography and tests of gravitation theories. We show explicitly, in the general relativistic context, how an observer may estimate his position and motion, and reconstruct the components of the metric. This arises from two main results: the extension of the velocity fields of the probes to the whole (curved) spacetime, and the identification of the components of the observer's velocity in the GPS frame with the (inversed) observed redshifts of the probes. Specific cases (non-relativistic velocities, Minkowski and Friedmann-Lemaitre spacetimes, geodesic motions) are studied in detail.
Covariance and objectivity in mechanics and turbulence
Frewer, Michael
2016-01-01
Form-invariance (covariance) and frame-indifference (objectivity) are two notions in classical continuum mechanics which have attracted much attention and controversy over the past decades. Particularly in turbulence modelling it seems that there still is a need for clarification. The aim and purpose of this study is fourfold: (i) To achieve consensus in general on definitions and principles when trying to establish an invariant theory for modelling constitutive structures and dynamic processes in mechanics, where special focus is put on the principle of Material Frame-Indifference (MFI). (ii) To show that in constitutive modelling MFI can only be regarded as an approximation that needs to be reduced to a weaker statement when trying to advance it to an axiom of nature. (iii) To convince that in dynamical modelling, as in turbulence, MFI may not be utilized as a modelling guideline, not even in an approximative sense. Instead, its reduced form has to be supplemented by a second, independent axiom that include...
Covariance structure models of expectancy.
Henderson, M J; Goldman, M S; Coovert, M D; Carnevalla, N
1994-05-01
Antecedent variables under the broad categories of genetic, environmental and cultural influences have been linked to the risk for alcohol abuse. Such risk factors have not been shown to result in high correlations with alcohol consumption and leave unclear an understanding of the mechanism by which these variables lead to increased risk. This study employed covariance structure modeling to examine the mediational influence of stored information in memory about alcohol, alcohol expectancies in relation to two biologically and environmentally driven antecedent variables, family history of alcohol abuse and a sensation-seeking temperament in a college population. We also examined the effect of criterion contamination on the relationship between sensation-seeking and alcohol consumption. Results indicated that alcohol expectancy acts as a significant, partial mediator of the relationship between sensation-seeking and consumption, that family history of alcohol abuse is not related to drinking outcome and that overlap in items on sensation-seeking and alcohol consumption measures may falsely inflate their relationship.
COVARIATION BIAS AND THE RETURN OF FEAR
de Jong, Peter; VANDENHOUT, MA; MERCKELBACH, H
1995-01-01
Several studies have indicated that phobic fear is accompanied by a covariation bias, i.e. that phobic Ss tend to overassociate fear relevant stimuli and aversive outcomes. Such a covariation bias seems to be a fairly direct and powerful way to confirm danger expectations and enhance fear. Therefore
Covariant derivative of fermions and all that
Shapiro, Ilya L
2016-01-01
We present detailed pedagogical derivation of covariant derivative of fermions and some related expressions, including commutator of covariant derivatives and energy-momentum tensor of a free Dirac field. The text represents a part of the initial chapter of a one-semester course on semiclassical gravity.
Schwinger mechanism in linear covariant gauges
Aguilar, A. C.; Binosi, D.; Papavassiliou, J.
2017-02-01
In this work we explore the applicability of a special gluon mass generating mechanism in the context of the linear covariant gauges. In particular, the implementation of the Schwinger mechanism in pure Yang-Mills theories hinges crucially on the inclusion of massless bound-state excitations in the fundamental nonperturbative vertices of the theory. The dynamical formation of such excitations is controlled by a homogeneous linear Bethe-Salpeter equation, whose nontrivial solutions have been studied only in the Landau gauge. Here, the form of this integral equation is derived for general values of the gauge-fixing parameter, under a number of simplifying assumptions that reduce the degree of technical complexity. The kernel of this equation consists of fully dressed gluon propagators, for which recent lattice data are used as input, and of three-gluon vertices dressed by a single form factor, which is modeled by means of certain physically motivated Ansätze. The gauge-dependent terms contributing to this kernel impose considerable restrictions on the infrared behavior of the vertex form factor; specifically, only infrared finite Ansätze are compatible with the existence of nontrivial solutions. When such Ansätze are employed, the numerical study of the integral equation reveals a continuity in the type of solutions as one varies the gauge-fixing parameter, indicating a smooth departure from the Landau gauge. Instead, the logarithmically divergent form factor displaying the characteristic "zero crossing," while perfectly consistent in the Landau gauge, has to undergo a dramatic qualitative transformation away from it, in order to yield acceptable solutions. The possible implications of these results are briefly discussed.
Yang, Chunwei; Yao, Junping; Sun, Dawei; Wang, Shicheng; Liu, Huaping
2016-05-01
Automatic target recognition in infrared imagery is a challenging problem. In this paper, a kernel sparse coding method for infrared target recognition using covariance descriptor is proposed. First, covariance descriptor combining gray intensity and gradient information of the infrared target is extracted as a feature representation. Then, due to the reason that covariance descriptor lies in non-Euclidean manifold, kernel sparse coding theory is used to solve this problem. We verify the efficacy of the proposed algorithm in terms of the confusion matrices on the real images consisting of seven categories of infrared vehicle targets.
Revisiting the equivalence of light-front and covariant QED in the light-cone gauge
Mantovani, Luca; Pasquini, Barbara; Xiong, Xiaonu; Bacchetta, Alessandro
2016-12-01
We discuss the equivalence between light-front time-ordered-perturbation theory and covariant quantum field theory in light-front quantization, in the case of quantum electrodynamics at one-loop level. In particular, we review the one-loop calculation of the vertex correction, fermion self-energy and vacuum polarization. We apply the procedure of integration by residue over the light-front energy in the loop to show how the perturbative expansion in covariant terms can be reduced to a sum of propagating and instantaneous diagrams of light-front time-ordered perturbation theory. The detailed proof of equivalence between the two formulations of the theory resolves the controversial question on which form should be used for the gauge-field propagator in the light-cone gauge in the covariant approach.
Revisiting the equivalence of light-front and covariant QED in the light-cone gauge
Mantovani, Luca; Xiong, Xiaonu; Bacchetta, Alessandro
2016-01-01
We discuss the equivalence between light-front time-ordered-perturbation theory and covariant quantum ?eld theory in light-front quantization, in the case of quantum electrodynamics at one-loop level. In particular, we review the one-loop calculation of the vertex correction, fermion self-energy and vacuum polarization. We apply the procedure of integration by residue over the light-front energy in the loop to show how the perturbative expansion in covariant terms can be reduced to a sum of propagating and instantaneous diagrams of light-front time-ordered perturbation theory. The detailed proof of equivalence between the two formulations of the theory resolves the controversial question on which form should be used for the gauge-?eld propagator in the light-cone gauge in the covariant approach.
Institute of Scientific and Technical Information of China (English)
ZHANG Ying; WANG Qing
2008-01-01
@@ Gauge covariance for Green's functions of a gauge theory through a fermion propagator in the presence of arbitrary external gauge field is proven and a formalism of gauge and Lorentz covariant Schwinger-Dyson equation for the fermion propagator with external gauge field is built up within ladder approximation.
Model Order Selection Rules for Covariance Structure Classification in Radar
Carotenuto, Vincenzo; De Maio, Antonio; Orlando, Danilo; Stoica, Petre
2017-10-01
The adaptive classification of the interference covariance matrix structure for radar signal processing applications is addressed in this paper. This represents a key issue because many detection architectures are synthesized assuming a specific covariance structure which may not necessarily coincide with the actual one due to the joint action of the system and environment uncertainties. The considered classification problem is cast in terms of a multiple hypotheses test with some nested alternatives and the theory of Model Order Selection (MOS) is exploited to devise suitable decision rules. Several MOS techniques, such as the Akaike, Takeuchi, and Bayesian information criteria are adopted and the corresponding merits and drawbacks are discussed. At the analysis stage, illustrating examples for the probability of correct model selection are presented showing the effectiveness of the proposed rules.
The notion of hormesis and the dose-response theory: a unified approach.
Murado, M A; Vázquez, J A
2007-02-07
According to an opinion which is vigorous and insistently defended for approximately one decade, hormesis (the response of a biological entity to an effector, with stimulatory results at low doses and inhibitory results at high doses) radically puts into question the classic theory of dose-response (DR) relationships and demands a profound revision of environmental protection policies. Herein we show that DR theory, with the modifications which we propose, allows the modelling of various kinds of biphasic responses which are phenomenologically similar to hormetic ones and of well-defined origin, as well as responses which have been treated as genuinely hormetic. Our descriptive approach may also represent a useful resource for experimental design, directed towards identifying some of the potentially heterogeneous mechanisms which underlie the hormetic phenomenon. Finally, it also allows to discuss some factors which prevent the use of the notion of hormesis-perhaps useful in a clinical context, under strictly controlled conditions-to make decisions on environmental protection measures.
The embodied cognition theory and the motor component of "yes" and "no" verbal responses.
Brouillet, Thibaut; Heurley, Loïc; Martin, Sophie; Brouillet, Denis
2010-07-01
Most of the experiments which give theories of embodied cognition their empirical anchorage only take into consideration the motor responses induced by the task or the motor component of the visual stimulus. And yet, these motor responses are often associated with a linguistic answer. Our hypothesis is that "YES" and "NO" verbal responses have a motor component. In a first experiment we showed that producing a verbal response (YES vs. NO) involves motor planning (pushing vs. pulling): participants push a lever more quickly when they have to answer "yes" than "no", and conversely, they pull a lever more quickly when they have to answer "no" than "yes". Moreover, in a second experiment, we showed that perceiving the words "YES" and "NO", on its own, leads to the same motor planning than when "yes" and "no" answers actually have to be produced. Participants detect the word "YES" faster when they have to push a lever than when they have to pull it and conversely they detect the word "NO" faster when they have to pull the lever than when they have to push it down. These results are discussed in reference to "online" and "offline embodiment" concepts and to the cognitive linguistic theories. 2010 Elsevier B.V. All rights reserved.
Treatment decisions based on scalar and functional baseline covariates.
Ciarleglio, Adam; Petkova, Eva; Ogden, R Todd; Tarpey, Thaddeus
2015-12-01
The amount and complexity of patient-level data being collected in randomized-controlled trials offer both opportunities and challenges for developing personalized rules for assigning treatment for a given disease or ailment. For example, trials examining treatments for major depressive disorder are not only collecting typical baseline data such as age, gender, or scores on various tests, but also data that measure the structure and function of the brain such as images from magnetic resonance imaging (MRI), functional MRI (fMRI), or electroencephalography (EEG). These latter types of data have an inherent structure and may be considered as functional data. We propose an approach that uses baseline covariates, both scalars and functions, to aid in the selection of an optimal treatment. In addition to providing information on which treatment should be selected for a new patient, the estimated regime has the potential to provide insight into the relationship between treatment response and the set of baseline covariates. Our approach can be viewed as an extension of "advantage learning" to include both scalar and functional covariates. We describe our method and how to implement it using existing software. Empirical performance of our method is evaluated with simulated data in a variety of settings and also applied to data arising from a study of patients with major depressive disorder from whom baseline scalar covariates as well as functional data from EEG are available.
A generalized non-local optical response theory for plasmonic nanostructures.
Mortensen, N A; Raza, S; Wubs, M; Søndergaard, T; Bozhevolnyi, S I
2014-05-02
Metallic nanostructures exhibit a multitude of optical resonances associated with localized surface plasmon excitations. Recent observations of plasmonic phenomena at the sub-nanometre to atomic scale have stimulated the development of various sophisticated theoretical approaches for their description. Here instead we present a comparatively simple semiclassical generalized non-local optical response theory that unifies quantum pressure convection effects and induced charge diffusion kinetics, with a concomitant complex-valued generalized non-local optical response parameter. Our theory explains surprisingly well both the frequency shifts and size-dependent damping in individual metallic nanoparticles as well as the observed broadening of the crossover regime from bonding-dipole plasmons to charge-transfer plasmons in metal nanoparticle dimers, thus unravelling a classical broadening mechanism that even dominates the widely anticipated short circuiting by quantum tunnelling. We anticipate that our theory can be successfully applied in plasmonics to a wide class of conducting media, including doped semiconductors and low-dimensional materials such as graphene.
Measuring the quality of life in hypertension according to Item Response Theory
Directory of Open Access Journals (Sweden)
José Wicto Pereira Borges
Full Text Available ABSTRACT OBJECTIVE To analyze the Miniquestionário de Qualidade de Vida em Hipertensão Arterial (MINICHAL – Mini-questionnaire of Quality of Life in Hypertension using the Item Response Theory. METHODS This is an analytical study conducted with 712 persons with hypertension treated in thirteen primary health care units of Fortaleza, State of Ceará, Brazil, in 2015. The steps of the analysis by the Item Response Theory were: evaluation of dimensionality, estimation of parameters of items, and construction of scale. The study of dimensionality was carried out on the polychoric correlation matrix and confirmatory factor analysis. To estimate the item parameters, we used the Gradual Response Model of Samejima. The analyses were conducted using the free software R with the aid of psych and mirt. RESULTS The analysis has allowed the visualization of item parameters and their individual contributions in the measurement of the latent trait, generating more information and allowing the construction of a scale with an interpretative model that demonstrates the evolution of the worsening of the quality of life in five levels. Regarding the item parameters, the items related to the somatic state have had a good performance, as they have presented better power to discriminate individuals with worse quality of life. The items related to mental state have been those which contributed with less psychometric data in the MINICHAL. CONCLUSIONS We conclude that the instrument is suitable for the identification of the worsening of the quality of life in hypertension. The analysis of the MINICHAL using the Item Response Theory has allowed us to identify new sides of this instrument that have not yet been addressed in previous studies.
Goel, Pranay
2013-01-01
Cells of almost all solid tissues are connected with gap junctions which permit the direct transfer of ions and small molecules, integral to regulating coordinated function in the tissue. The pancreatic islets of Langerhans are responsible for secreting the hormone insulin in response to glucose stimulation. Gap junctions are the only electrical contacts between the beta-cells in the tissue of these excitable islets. It is generally believed that they are responsible for synchrony of the membrane voltage oscillations among beta-cells, and thereby pulsatility of insulin secretion. Most attempts to understand connectivity in islets are often interpreted, bottom-up, in terms of measurements of gap junctional conductance. This does not, however explain systematic changes, such as a diminished junctional conductance in type 2 diabetes. We attempt to address this deficit via the model presented here, which is a learning theory of gap junctional adaptation derived with analogy to neural systems. Here, gap junctions ...
Batel, Susana; Devine-Wright, Patrick
2015-04-01
In the past few years, social research has been examining what contributes to the attitude-behaviour gap in people's responses to large-scale renewable energy technologies. The NIMBY explanation for the gap has long dominated that area of research, but has also been criticised. Alternative proposals to NIMBY were advanced, but it is still evident that some of those maintain presuppositions of NIMBY and that this area of research needs more integration, namely at a theoretical level. In this paper we argue that to overcome those aspects it is relevant, first, to situate the promotion of renewable energy production as a social change process in today's societies, and, second, to therefore consider the socio-psychological aspects involved in people's responses to social change. We discuss specifically how the Theory of Social Representations may help us with that and contribute to a better understanding of people's responses to renewable energy technologies.
Stability of Mixed-Strategy-Based Iterative Logit Quantal Response Dynamics in Game Theory
Zhuang, Qian; Wu, Jinshan
2013-01-01
Using the Logit quantal response form as the response function in each step, the original definition of static quantal response equilibrium (QRE) is extended into an iterative evolution process. QREs remain as the fixed points of the dynamic process. However, depending on whether such fixed points are the long-term solutions of the dynamic process, they can be classified into stable (SQREs) and unstable (USQREs) equilibriums. This extension resembles the extension from static Nash equilibriums (NEs) to evolutionary stable solutions in the framework of evolutionary game theory. The relation between SQREs and other solution concepts of games, including NEs and QREs, is discussed. Using experimental data from other published papers, we perform a preliminary comparison between SQREs, NEs, QREs and the observed behavioral outcomes of those experiments. For certain games, we determine that SQREs have better predictive power than QREs and NEs.
Stability of mixed-strategy-based iterative logit quantal response dynamics in game theory.
Zhuang, Qian; Di, Zengru; Wu, Jinshan
2014-01-01
Using the Logit quantal response form as the response function in each step, the original definition of static quantal response equilibrium (QRE) is extended into an iterative evolution process. QREs remain as the fixed points of the dynamic process. However, depending on whether such fixed points are the long-term solutions of the dynamic process, they can be classified into stable (SQREs) and unstable (USQREs) equilibriums. This extension resembles the extension from static Nash equilibriums (NEs) to evolutionary stable solutions in the framework of evolutionary game theory. The relation between SQREs and other solution concepts of games, including NEs and QREs, is discussed. Using experimental data from other published papers, we perform a preliminary comparison between SQREs, NEs, QREs and the observed behavioral outcomes of those experiments. For certain games, we determine that SQREs have better predictive power than QREs and NEs.
The covariate-adjusted frequency plot.
Holling, Heinz; Böhning, Walailuck; Böhning, Dankmar; Formann, Anton K
2016-04-01
Count data arise in numerous fields of interest. Analysis of these data frequently require distributional assumptions. Although the graphical display of a fitted model is straightforward in the univariate scenario, this becomes more complex if covariate information needs to be included into the model. Stratification is one way to proceed, but has its limitations if the covariate has many levels or the number of covariates is large. The article suggests a marginal method which works even in the case that all possible covariate combinations are different (i.e. no covariate combination occurs more than once). For each covariate combination the fitted model value is computed and then summed over the entire data set. The technique is quite general and works with all count distributional models as well as with all forms of covariate modelling. The article provides illustrations of the method for various situations and also shows that the proposed estimator as well as the empirical count frequency are consistent with respect to the same parameter.
Softening the Blow of Social Exclusion: The Responsive Theory of Social Exclusion.
Freedman, Gili; Williams, Kipling D; Beer, Jennifer S
2016-01-01
Social exclusion is an interactive process between multiple people, yet previous research has focused almost solely on the negative impacts on targets. What advice is there for people on the other side (i.e., sources) who want to minimize its negative impact and preserve their own reputation? To provide an impetus for research on the interactive nature of exclusion, we propose the Responsive Theory of Social Exclusion. Our theory postulates that targets and sources' needs are better maintained if sources use clear, explicit verbal communication. We propose that sources have three options: explicit rejection (clearly stating no), ostracism (ignoring), and ambiguous rejection (being unclear). Drawing on psychology, sociology, communications, and business research, we propose that when sources use explicit rejection, targets' feelings will be less hurt, their needs will be better protected, and sources will experience less backlash and emotional toil than if sources use ambiguous rejection or ostracism. Finally, we propose how the language of rejections may impact both parties.
Dubois, Maarten
2012-09-01
Although economic theory supports the use of extended producer responsibility (EPR) to stimulate prevention and recycling of waste, EPR systems implemented in Europe are often criticized as a result of weak incentives for prevention and green product design. Using a stylized economic model, this article evaluates the efficiency of European EPR systems. The model reveals that the introduction of static collection targets creates a gap between theory and implementation. Static targets lead to inefficient market outcomes and weak incentives for prevention and green product design. The minimum collection targets should be complemented with a tax on producers for the non-collected waste fraction. Because such a tax internalizes the cost of waste disposal, more efficient price signals will lead to better incentives for waste management in a complex and dynamic market.
Lieb-Robinson bounds for multi-commutators and applications to response theory
Bru, J -B
2017-01-01
Lieb-Robinson bounds for multi-commutators are effective mathematical tools to handle analytic aspects of infinite volume dynamics of non-relativistic quantum particles with short-range, possibly time-dependent interactions. In particular, the existence of fundamental solutions is shown for those (non-autonomous) C*-dynamical systems for which the usual conditions found in standard theories of (parabolic or hyperbolic) non-autonomous evolution equations are not given. In mathematical physics, bounds on multi-commutators of an order higher than two can be used to study linear and non-linear responses of interacting particles to external perturbations. These bounds are derived for lattice fermions, in view of applications to microscopic quantum theory of electrical conduction discussed in this book. All results also apply to quantum spin systems, with obvious modifications. In order to make the results accessible to a wide audience, in particular to students in mathematics with little Physics background, basics...
Franco-Pérez, Marco; Ayers, Paul W; Gázquez, José L; Vela, Alberto
2015-12-28
We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.
Energy Technology Data Exchange (ETDEWEB)
Franco-Pérez, Marco, E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México, D.F. 09340 (Mexico); Ayers, Paul W., E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Gázquez, José L., E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México, D.F. 09340 (Mexico); Vela, Alberto, E-mail: francopj@mcmaster.ca, E-mail: ayers@mcmaster.ca, E-mail: jlgm@xanum.uam.mx, E-mail: avela@cinvestav.mx [Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), Av. Instituto Politécnico Nacional 2508, México, D.F. 07360 (Mexico)
2015-12-28
We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model.
Dallavis, Christian
2011-01-01
In this conceptual article the author explores the intersection of culturally responsive pedagogy and religious school contexts. He extends theories of culturally responsive pedagogy to consider how religion, a dimension of student culture that has largely been overlooked in the literature surrounding culturally responsive pedagogy, can inflect…
Dallavis, Christian
2011-01-01
In this conceptual article the author explores the intersection of culturally responsive pedagogy and religious school contexts. He extends theories of culturally responsive pedagogy to consider how religion, a dimension of student culture that has largely been overlooked in the literature surrounding culturally responsive pedagogy, can inflect…
Fowler, Mike S; Ruokolainen, Lasse
2013-05-01
Understanding the mechanisms that underlie the relationship between community diversity and biomass stability is a fundamental topic in ecology. Theory has emphasized differences in species-specific responses to environmental fluctuations as an important stabiliser of total biomass fluctuations. However, previous analyses have often been based on simplifying assumptions, such as uniform species abundance distributions, uniform environmental variance across species, and uniform environmental responses across species pairs. We compare diversity-stability relationships in model communities, based on multi-species Ricker dynamics, that follow different colonization rules during community assembly (fixed or flexible resource use) forced by temporally uncorrelated (white) or correlated (red) environmental fluctuations. The colonization rules generate characteristic niche-dependent (hierarchical, HR) environmental covariance structures, which we compare with uncorrelated (independent, IR) species' environmental responses. Environmental reddening increases biomass stability and qualitatively alters diversity-stability patterns in HR communities, under both colonization rules. Diversity-stability patterns in IR communities are qualitatively altered by colonization rules but not by environmental colour. Our results demonstrate that diversity-stability patterns are contingent upon species' colonization strategies (resource use), emergent or independent responses to environmental fluctuations, and the colour of environmental fluctuations. We describe why our results arise through differences in species traits associated with niche position. These issues are often overlooked when considering the statistical components commonly used to describe diversity-stability patterns (e.g., Overyielding, Portfolio and Covariance effects). Mechanistic understanding of different diversity-stability relationships requires consideration of the biological processes that drive different
Forecasting Covariance Matrices: A Mixed Frequency Approach
DEFF Research Database (Denmark)
Halbleib, Roxana; Voev, Valeri
This paper proposes a new method for forecasting covariance matrices of financial returns. The model mixes volatility forecasts from a dynamic model of daily realized volatilities estimated with high-frequency data with correlation forecasts based on daily data. This new approach allows...... for flexible dependence patterns for volatilities and correlations, and can be applied to covariance matrices of large dimensions. The separate modeling of volatility and correlation forecasts considerably reduces the estimation and measurement error implied by the joint estimation and modeling of covariance...... matrix dynamics. Our empirical results show that the new mixing approach provides superior forecasts compared to multivariate volatility specifications using single sources of information....
Estimation of Low-Rank Covariance Function
Koltchinskii, Vladimir; Lounici, Karim; Tsybakov, Alexander B.
2015-01-01
We consider the problem of estimating a low rank covariance function $K(t,u)$ of a Gaussian process $S(t), t\\in [0,1]$ based on $n$ i.i.d. copies of $S$ observed in a white noise. We suggest a new estimation procedure adapting simultaneously to the low rank structure and the smoothness of the covariance function. The new procedure is based on nuclear norm penalization and exhibits superior performances as compared to the sample covariance function by a polynomial factor in the sample size $n$...
Schwartz, Carolyn E; Andresen, Elena M; Nosek, Margaret A; Krahn, Gloria L
2007-04-01
Measurement of health-related quality of life (HRQOL) in people with disability can be problematic. Ambiguous or paradoxical findings can occur because of differences among people or changes within people regarding internal standards, values, or conceptualization of HRQOL. These "response shifts" can affect standard psychometric indices, such as reliability and validity. Attending to appraisal processes and response shift theory can inform development of HRQOL measures for people with disability that do not confound function and health and that consider important causal indicators such as environment. By design, most HRQOL measures equate function with health, necessarily leading to a lower measured HRQOL in people with functional impairments regardless of their level of self-perceived health. In this article, we present theoretical and conceptual distinctions building on response shift theory and other current developments in HRQOL research. We then submit a set of suggested directions for future measurement development in populations with disabilities that consider these distinctions and extend their use in future measurement developments.
mirt: A Multidimensional Item Response Theory Package for the R Environment
Directory of Open Access Journals (Sweden)
R. Philip Chalmers
2012-05-01
Full Text Available Item response theory (IRT is widely used in assessment and evaluation research to explain how participants respond to item level stimuli. Several R packages can be used to estimate the parameters in various IRT models, the most flexible being the ltm (Rizopoulos 2006, eRm (Mair and Hatzinger 2007, and MCMCpack (Martin, Quinn, and Park 2011 packages. However these packages have limitations in that ltm and eRm can only analyze unidimensional IRT models effectively and the exploratory multidimensional extensions available in MCMCpack requires prior understanding of Bayesian estimation convergence diagnostics and are computationally intensive. Most importantly, multidimensional confirmatory item factor analysis methods have not been implemented in any R package.The mirt package was created for estimating multidimensional item response theory parameters for exploratory and confirmatory models by using maximum-likelihood meth- ods. The Gauss-Hermite quadrature method used in traditional EM estimation (e.g., Bock and Aitkin 1981 is presented for exploratory item response models as well as for confirmatory bifactor models (Gibbons and Hedeker 1992. Exploratory and confirmatory models are estimated by a stochastic algorithm described by Cai (2010a,b. Various program comparisons are presented and future directions for the package are discussed.
Steindal, Arnfinn Hykkerud; Beerepoot, Maarten T P; Ringholm, Magnus; List, Nanna Holmgaard; Ruud, Kenneth; Kongsted, Jacob; Olsen, Jógvan Magnus Haugaard
2016-10-12
We present the theory and implementation of an open-ended framework for electric response properties at the level of Hartree-Fock and Kohn-Sham density functional theory that includes effects from the molecular environment modeled by the polarizable embedding (PE) model. With this new state-of-the-art multiscale functionality, electric response properties to any order can be calculated for molecules embedded in polarizable atomistic molecular environments ranging from solvents to complex heterogeneous macromolecules such as proteins. In addition, environmental effects on multiphoton absorption (MPA) properties can be studied by evaluating single residues of the response functions. The PE approach includes mutual polarization effects between the quantum and classical parts of the system through induced dipoles that are determined self-consistently with respect to the electronic density. The applicability of our approach is demonstrated by calculating MPA strengths up to four-photon absorption for the green fluorescent protein. We show how the size of the quantum region, as well as the treatment of the border between the quantum and classical regions, is crucial in order to obtain reliable MPA predictions.
Role of Local Response in Ion Solvation: Born Theory and Beyond.
Remsing, Richard C; Weeks, John D
2016-07-07
The nature of ion solvation has drawn the interest of scientists for over a century, yet a thorough theoretical understanding is still lacking. In this work, we focus on the microscopic origins underlying ionic charge asymmetric and nonlinear response contributions to ion solvation free energies. We first derive an exact expression for the charging component of the ionic free energy, the free energy change when the Coulomb interactions between a fixed ion and the solvent are gradually "turned on". We then introduce the concept of a Gaussian test charge distribution, a generalization of the classical electrostatic point test charge that can be used to probe dielectric response in atomically detailed models. This enables the study of a thermodynamic cycle that isolates a linear and charge-symmetric contribution to the free energy that is well-described by Born-model-like dielectric continuum theories. We give a simple physical derivation of the classic Born model that locally relates the induced charge density in a linear dielectric model to the applied ionic charge distribution. The nonlinear response and charge asymmetric contributions to the ion solvation free energy are then examined in the remaining steps of the cycle and compared to classic thermodynamic cycles for this process using computer simulations. The insights provided by this work will aid the development of quantitative theories for the solvation of charged solutes.
Using critical race theory to analyze science teachers culturally responsive practices
Wallace, Tamara; Brand, Brenda R.
2012-06-01
Culturally responsive science teaching is using knowledge about the culture and life experiences of students to structure learning that is conducive to their needs. Understanding what teachers need to prepare them to be culturally responsive is a matter of continuous debate. As the focus of multicultural education ventures farther away from its roots, advocating the civil rights of historically oppressed groups, concerns about the gravity of racial inequity on schooling continues. How will this shift in focus influence teachers' capacity to accommodate students' needs resulting from racial inequities in this society, particularly African American students? What knowledge is essential to their effectiveness? This qualitative study examined the instructional practices of two effective middle school science teachers deemed culturally responsive by their administrator on the basis of classroom observations, students' responses and standardized assessment results. Both teachers' classrooms consisted primarily of African American students. Grounded theory was used to analyze the teachers' beliefs and practices in order to identify existing commonalties. Critical race theory was used to identify whether there was any influence of the students' racial identities on the teachers' beliefs and practices. The analysis reveals that the teachers' beliefs and practices were informed by their critical awareness of social constraints imposed upon their African American students' identities. These findings communicate the significance of sociocultural awareness to informing the teachers' instruction, as well as their strategies for managing the varying dynamics occurring in their classrooms. It can be deduced from the findings that an understanding of racial inequities is crucial to the development of sociocultural awareness, and is the foundation for the culturally responsive dispositions and practices of these middle school science teachers.
Adiabatic approximation of time-dependent density matrix functional response theory.
Pernal, Katarzyna; Giesbertz, Klaas; Gritsenko, Oleg; Baerends, Evert Jan
2007-12-07
Time-dependent density matrix functional theory can be formulated in terms of coupled-perturbed response equations, in which a coupling matrix K(omega) features, analogous to the well-known time-dependent density functional theory (TDDFT) case. An adiabatic approximation is needed to solve these equations, but the adiabatic approximation is much more critical since there is not a good "zero order" as in TDDFT, in which the virtual-occupied Kohn-Sham orbital energy differences serve this purpose. We discuss a simple approximation proposed earlier which uses only results from static calculations, called the static approximation (SA), and show that it is deficient, since it leads to zero response of the natural orbital occupation numbers. This leads to wrong behavior in the omega-->0 limit. An improved adiabatic approximation (AA) is formulated. The two-electron system affords a derivation of exact coupled-perturbed equations for the density matrix response, permitting analytical comparison of the adiabatic approximation with the exact equations. For the two-electron system also, the exact density matrix functional (2-matrix in terms of 1-matrix) is known, enabling testing of the static and adiabatic approximations unobscured by approximations in the functional. The two-electron HeH(+) molecule shows that at the equilibrium distance, SA consistently underestimates the frequency-dependent polarizability alpha(omega), the adiabatic TDDFT overestimates alpha(omega), while AA improves upon SA and, indeed, AA produces the correct alpha(0). For stretched HeH(+), adiabatic density matrix functional theory corrects the too low first excitation energy and overpolarization of adiabatic TDDFT methods and exhibits excellent agreement with high-quality CCSD ("exact") results over a large omega range.
Assessing spatial covariance among time series of abundance.
Jorgensen, Jeffrey C; Ward, Eric J; Scheuerell, Mark D; Zabel, Richard W
2016-04-01
For species of conservation concern, an essential part of the recovery planning process is identifying discrete population units and their location with respect to one another. A common feature among geographically proximate populations is that the number of organisms tends to covary through time as a consequence of similar responses to exogenous influences. In turn, high covariation among populations can threaten the persistence of the larger metapopulation. Historically, explorations of the covariance in population size of species with many (>10) time series have been computationally difficult. Here, we illustrate how dynamic factor analysis (DFA) can be used to characterize diversity among time series of population abundances and the degree to which all populations can be represented by a few common signals. Our application focuses on anadromous Chinook salmon (Oncorhynchus tshawytscha), a species listed under the US Endangered Species Act, that is impacted by a variety of natural and anthropogenic factors. Specifically, we fit DFA models to 24 time series of population abundance and used model selection to identify the minimum number of latent variables that explained the most temporal variation after accounting for the effects of environmental covariates. We found support for grouping the time series according to 5 common latent variables. The top model included two covariates: the Pacific Decadal Oscillation in spring and summer. The assignment of populations to the latent variables matched the currently established population structure at a broad spatial scale. At a finer scale, there was more population grouping complexity. Some relatively distant populations were grouped together, and some relatively close populations - considered to be more aligned with each other - were more associated with populations further away. These coarse- and fine-grained examinations of spatial structure are important because they reveal different structural patterns not evident