cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Coherence and metamagnetism in the two-dimensional Kondo lattice model
Creators: name: Beach, K. S. D.
name: Assaad, F. F.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We report the results of dynamical mean field calculations for the metallic Kondo lattice model subject to an applied magnetic field. High-quality spectral functions reveal that the picture of rigid, hybridized bands, Zeeman-shifted in proportion to the field strength, is qualitatively correct. We find evidence of a zero-temperature magnetization plateau, whose onset coincides with the chemical potential entering the spin up hybridization gap. The plateau appears at the field scale predicted by (static) large-N mean field theory and has a magnetization value consistent with that of x=1-n_c spin-polarized heavy holes, where n_c < 1 is the conduction band filling of the noninteracting system. We argue that the emergence of the plateau at low temperature marks the onset of quasiparticle coherence.
description: 8 pages, 6 figures
Application of Hellman-Feynman and Hypervirial theorems to the eigenvalue problem: Coulomb plus linear term and quartic anharmonic oscillator potentials
Creators: name: Rekab, S.
name: Zenine, N.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: We use the Hellman-Feynman (HF) and Hypervirial (HV) theorems, to calculate the perturbative coefficients of the eigenenergies formal series, in the case of the Coulomb potential with a radial linear term and the radial quartic anharmonic oscillator potential. This calculation method, contrary to the usual Rayleigh-Schrodinger Perturbation Theory (RSPT), does not require the calculation of eigenfunctions coefficients. This method is a fast and efficient tool for the calculation of large order eigenenergies coefficients.
description: 12 pages, no figures, to be published in Algerian Review of Nuclear Sciences
Renyi Dimension and Gaussian Filtering II
Creators: name: Loring, Terry A.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Functional Analysis (math.FA)
subject: FOS: Mathematics
subject: 28A80, 28A78

description: We consider convolving a Gaussian of a varying scale epsilon against a Borel measure mu on Euclidean delta-dimensional space. The Lq norm of the result is differentiable in epsilon. We calculate this derivative and show how the upper order of its growth relates to its lower Renyi dimension. We assume q is strictly between 1 and infty and that mu is finite with compact support. Consider choosing a sequence epsilon_n of scales for the Gaussians. The differences between the usual Lq norms at adjacent scales can be made to grow more slowly than any positive power of n by setting the epsilon_n by a power rule. The correct exponent in the power rule is determined by the lower Renyi dimension. We calculate and find bounds on the derivative of the Gaussian kernel versions of the correlation integral. We show that a Gaussian Kernel version of the Renyi entropy sum in continuous.
description: 20 pages. Added a section on a Gaussian Kernel version of the Renyi entropy sums. Stronger statements of the main theorems
First Nations popular music in Canada : identity, politics and musical meaning
Creators: name: Scales, Christopher Alton
Publisher: name: University of British Columbia
Year: 2009

description: In this thesis, First Nations popular music is examined as a polysemic sign (or symbolic form) whose meaning is mediated both socially and politically. Native popular music is a locus for the action of different social forces which interact in negotiating the nature and the meaning of the music. Music is socially meaningful in that it provides a means by which people construct and recognize social and cultural identities. As such, First Nations popular music functions as an emblem of symbolic differentiation between Canadian natives and non-natives. Native pop music plays host to a number of political meanings embedded in this syncretic musical form. Struggle over meaning is mediated within the music itself: in the lyrics, in the music, in the juxtaposition of musical styles, and between music and text. Mediation on all of these levels is further influenced by the mass media. Meaning on individual, local and national levels is dependent on the socio-political positioning of both the performers and the audience. Because socio-political positions are themselves fluid, political meanings are also in constant flux. As a polysemic sign vehicle, First Nations popular music is a locus for these various meanings and a site for the construction and deconstruction of political discourse.
Lower bound on the blow-up rate of the axisymmetric Navier-Stokes equations
Creators: name: Chen, Chiun-Chuan
name: Strain, Robert M.
name: Tsai, Tai-Peng
name: Yau, Horng-Tzer
Publisher: name: arXiv
Year: 2007
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics

description: Consider axisymmetric strong solutions of the incompressible Navier-Stokes equations in $\R^3$ with non-trivial swirl. Such solutions are not known to be globally defined, but it is shown in \cite{MR673830} that they could only blow up on the axis of symmetry. Let $z$ denote the axis of symmetry and $r$ measure the distance to the z-axis. Suppose the solution satisfies the pointwise scale invariant bound $|v (x,t)| \le C_*{(r^2 -t)^{-1/2}} $ for $-T_0\le t < 0$ and $0
description: 25 pages
Anisotropic separate universe and Weinberg's adiabatic mode
Creators: name: Tanaka, Takahiro
name: Urakawa, Yuko
Publisher: name: arXiv
Year: 2021
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In the separate universe approach, an inhomogeneous universe is rephrased as a set of glued numerous homogeneous local patches. This is the essence of the gradient expansion and the $δN$ formalism, which have been widely used in solving a long wavelength evolution of the universe. In this paper, we show that the separate universe approach can be generically used, as long as a theory under consideration is local and preserves the spatial diffeomorphism invariance. Focusing on these two conditions, we also clarify the condition for the existence of the so-called Weinberg's adiabatic mode. Remarkably, the separate universe approach and the $δN$ formalism turn out to be applicable also to models with shear on large scales and also to modified theories of gravity, accepting violation of four-dimensional diffeomorphism invariance. The generalized $δN$ formalism enables us to calculate all the large scale fluctuations, including gravitational waves. We also argue several implications on anisotropic inflation and ultra slow-roll inflation.
description: 48 pages, 1 figure
Two-dimensional flow of foam around a circular obstacle: local measurements of elasticity, plasticity and flow
Creators: name: Dollet, Benjamin
name: Graner, Francois
Publisher: name: arXiv
Year: 2006
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: We investigate the two-dimensional flow of a liquid foam around circular obstacles by measuring all the local fields necessary to describe this flow: velocity, pressure, bubble deformations and rearrangements. We show how our experimental setup, a quasi-2D "liquid pool" system, is adapted to the determination of these fields: the velocity and bubble deformations are easy to measure from 2D movies, and the pressure can be measured by exploiting a specific feature of this system, a 2D effective compressibility. To describe accurately bubble rearrangements, we propose a new, tensorial descriptor. All these quantities are evaluated via an averaging procedure that we justify showing that the fluctuations of the fields are essentially random. The flow is extensively studied in a reference experimental case; the velocity presents an overshoot in the wake of the obstacle, the pressure is maximum at the leading side and minimal at the trailing side. The study of the elastic deformations and of the velocity gradients shows that the transition between plug flow and yielded regions is smooth. Our tensorial description of T1s highlight their correlation both with the bubble deformations and the velocity gradients. A salient feature of the flow, notably on the velocity and T1 repartition, is a marked asymmetry upstream/downstream, signature of the elastic behaviour of the foam. We show that the results do not change qualitatively when various control parameters vary, identifying a robust quasistatic regime. These results are discussed in the frame of the actual foam rheology literature, and we argue that they constitute a severe test for existing rheological models, since they capture both the elastic, plastic and fluid behaviour of the foam.
description: 41 pages, 25 figures, submitted to Journal of Fluid Mechanics (but not in JFM style), short version of the abstract
Sustainable Production and Characterization of Activated Carbon from Palm Kernel Shell: Assessing Its Potential for Industrial Applications
Creators: name: Abass Mustapha
Publisher: name: Nigerian Journal of Engineering Science Research (NIJESR).
Year: 2023

description: The objective of this study is to produce and comprehensively characterize activated carbon derived from palm kernel shell, aiming to explore its potential as an efficient adsorbent in various industrial applications. The palm kernel shell was initially carbonized in an electric furnace at an elevated temperature of 700°C for a duration of two hours, followed by chemical activation using concentrated H₂SO₄ at 900°C for one hour. The resultant activated carbon was subjected to a rigorous characterization process in accordance with the ASTM standard methods. The results revealed a relatively low moisture content of 10%, an ash content of just 1%, an impressive iodine number of 552.15, indicating substantial adsorption capacity, and a slightly acidic pH value of 4.6. These findings demonstrate that the activated carbon produced exhibits desirable physicochemical properties, suggesting its potential application in water purification, gas adsorption, and as a catalyst support in various chemical processes. This research contributes to the development of value-added products from agro-waste, promoting sustainable practices and offering a viable solution for waste management.
The Villafranca catalog of Galactic OB groups: I. Systems with O2-O3.5 stars
Creators: name: Apellániz, J. Maíz
name: Bellido, P. Crespo
name: Barbá, R. H.
name: Aranda, R. Fernández
name: Sota, A.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: CONTEXT. The GOSSS spectral classifications and Gaia data have significantly improved our ability to measure distances and determine memberships of stellar groups with OB stars. AIMS. We have started a program to identify, measure distances, and determine the membership of Galactic stellar groups with OB stars. We start with the identification and distance determinations of groups with O stars. In this paper we concentrate on groups that contain stars with the earliest spectral subtypes. METHODS. We use GOSSS to select Galactic stellar groups with O2-O3.5 stars and a method that combines Gaia DR2 photometry, positions, proper motions, and parallaxes to assign robust memberships and measure distances. We also include the two clusters in that paper to generate our first list of 16 O-type Galactic stellar groups. RESULTS. We derive distances, determine the membership, and analyze the structure of sixteen Galactic stellar groups with O stars, Villafranca O-001 to O-016, including the 14 groups with the earliest-O-type optically-accessible stars known in the Milky Way. We compare our distance with previous results and establish that the best consistency is with VLBI parallaxes and the worst is with kinematic distances. Our results indicate that massive stars can form in relatively low-mass clusters or even in near-isolation, as is the case for the Bajamar star in the North America nebula. This lends support to the hierarchical scenario of star formation, where some stars are born in well-defined bound clusters but others are born in associations that are unbound from the beginning: groups of newborn stars come in many shapes and sizes. We propose that HD 64 568 and HD 64 315 AB could have been ejected simultaneously from Villafranca O-012 S. Our results are consistent with a difference of approx. 20 microas in the Gaia DR2 parallax zero point between bright and faint stars. (ABRIDGED)
description: Accepted for publication in A&A
Absence of a Dirac gap in ferromagnetic Cr$_x$(Bi$_{0.1}$Sb$_{0.9}$)$_{2-x}$Te$_3$
Creators: name: Kim, Chung Koo
name: Denlinger, Jonathan D.
name: Kundu, Asish K.
name: Gu, Genda
name: Valla, Tonica
Publisher: name: arXiv
Year: 2020
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Magnetism breaks the time reversal symmetry expected to open a Dirac gap in 3D topological insulators that consequently leads to quantum anomalous Hall effect. The most common approach of inducing ferromagnetic state is by doping magnetic 3$d$ elements into bulk of 3D topological insulators. In Cr$_{0.15}$(Bi$_{0.1}$Sb$_{0.9}$)$_{1.85}$Te$_3$, the material where the quantum anomalous Hall effect was initially discovered at temperatures much lower than the ferromagnetic transition, $T_C$, the scanning tunneling microscopy studies have reported a large Dirac gap $\sim20-100$ meV. The discrepancy between the low temperature of quantum anomalous Hall effect ($\ll T_C$) and large spectroscopic Dirac gaps ($\gg T_C$) found in magnetic topological insulators remains puzzling. Here, we used angle-resolved photoemission spectroscopy to study the surface electronic structure of pristine and potassium doped surface of Cr$_{0.15}$(Bi$_{0.1}$Sb$_{0.9}$)$_{1.85}$Te$_3$. Upon potassium deposition, the $p$-type surface state of pristine sample was turned into an $n$-type, allowing spectroscopic observation of Dirac point. We find a gapless surface state, with no evidence of a large Dirac gap reported in tunneling studies.
description: 7 pages, 3 figures
The Phase Transition to Eternal Inflation
Creators: name: Creminelli, Paolo
name: Dubovsky, Sergei
name: Nicolis, Alberto
name: Senatore, Leonardo
name: Zaldarriaga, Matias
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Astrophysics (astro-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: For slow-roll inflation we study the phase transition to the eternal regime. Starting from a finite inflationary volume, we consider the volume of the universe at reheating as order parameter. We show that there exists a critical value for the classical inflaton speed, \dotϕ^2/H^4 = 3/(2 π^2), where the probability distribution for the reheating volume undergoes a sharp transition. In particular, for sub-critical inflaton speeds all distribution moments become infinite. We show that at the same transition point the system develops a non-vanishing probability of having a strictly infinite reheating volume, while retaining a finite probability for finite values. Our analysis represents the exact quantum treatment of the system at lowest order in the slow-roll parameters and H^2/M_Pl^2.
description: 48 pages, 8 figures. v2: JHEP published version, shortened title, added references
Production experiment, subject 41
Creators: name: Lau-Preechathammarach, Raksit Tyler
Publisher: name: California Language Archive, University of California, Berkeley
Year: 2023
Subjects: subject: kdt

description: Target and distractor stimuli embedded in carrier sentences. Subject is a 25-year-old female. Carried out in a quiet room in the temple of Wat Nakharin in Ban Khi Nak.
Two-dimensional polyacrylamide gel electrophoretic analysis of protein synthesis during aromatic acid catabolism by Streptomyces violaceusniger
Creators: name: Chow, Kevin Toshio
Publisher: name: University of British Columbia
Year: 2009

description: Streptomycetes were isolated from soil samples and screened for biodegradative activity against lignin-related aromatic compounds. One isolate, Streptomyces violaceusniger, efficiently utilized 4-hydroxy-3-methoxybenzoic acid (vanillate) and 4-hydroxybenzoic acid (p-hydroxybenzoate) as sole sources of carbon and energy. S. violaceusniger was able to biotransform indole to the dye indigo, indicative of aromatic dioxygenase activity. Colorimetric Rothera assays demonstrated the induction of aromatic dioxygenase activity in S. violaceusniger in the presence of vanillate and p-hydroxybenzoate. Twodimensional gel electrophoresis of total cell proteins revealed the synthesis of specific groups of proteins upon growth in the presence of vanillate, p-hydroxybenzoate or 3,4- dihydroxybenzoic acid (protocatechuate). The amino-terminal sequence of a heavily expressed 52 kDa protein, induced by vanillate andp-hydroxybenzoate, was highly similar to the amino-terminus of a hypothetical 55 kDa protein discovered during the course of the Escherichia coli genome sequencing project. The S. violaceusniger sequence aligns with conserved regions adjacent to nucleotide binding domains of the GTP-binding cc-subunit protein family and valyl-tRNA synthetases. Because biodegradative monooxygenases are known to possess nucleotide binding domains near the amino terminus and the protein is synthesized in such abundance, it is suggested that the 52 kDa protein is an enzyme involved in aromatic biodegradation. The results of this work are of interest to the study of lignin biodegradation, and also to the study of the catabolism of phenolic compounds in Streptomyces.
Large-N expansions applied to gravitational clustering
Creators: name: Valageas, Patrick
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We develop a path-integral formalism to study the formation of large-scale structures in the universe. Starting from the equations of motion of hydrodynamics (single-stream approximation) we derive the action which describes the statistical properties of the density and velocity fields for Gaussian initial conditions. Then, we present large-N expansions (associated with a generalization to N fields or with a semi-classical expansion) of the path-integral defined by this action. This provides a systematic expansion for two-point functions such as the response function and the usual two-point correlation. We present the results of two such expansions (and related variants) at one-loop order for a SCDM and a LCDM cosmology. We find that the response function exhibits fast oscillations in the non-linear regime with an amplitude which either follows the linear prediction (for the direct steepest-descent scheme) or decays (for the 2PI effective action scheme). On the other hand, the correlation function agrees with the standard one-loop result in the quasi-linear regime and remains well-behaved in the highly non-linear regime. This suggests that these large-N expansions could provide a good framework to study the dynamics of gravitational clustering in the non-linear regime. Moreover, the use of various expansion schemes allows one to estimate their range of validity without the need of N-body simulations and could provide a better accuracy in the weakly non-linear regime.
description: 27 pages, published in A&A
Generalized true- and eccentric-anomaly parametrizations for the perturbed Kepler motion
Creators: name: Gergely, László Á.
name: Perjés, Zoltán I.
name: Vasúth, Mátyás
Publisher: name: arXiv
Year: 2007
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The true- and eccentric-anomaly parametrizations of the Kepler motion are generalized to quasiperiodic orbits by considering perturbations of the radial part of kinetic energy as a series in the negative powers of the orbital radius. A toolbox of methods for averaging observables in terms of the energy $E$ and angular momentum $L$ is developed. A broad range of systems governed by the generic Brumberg force, as well as recent applications of the theory of gravitational radiation involve integrals over a period of motion. These integrals are evaluated by using the residue theorem. It is shown that the pole of the integrand is located in the origin and that under certain circumstances an additional pole emerges.
`Mass without mass' from thin shells in Gauss-Bonnet gravity
Creators: name: Gravanis, Elias
name: Willison, Steven
Publisher: name: arXiv
Year: 2007
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Five tensor equations are obtained for a thin shell in Gauss-Bonnet gravity. There is the well known junction condition for the singular part of the stress tensor intrinsic to the shell, which we also prove to be well defined. There are also equations relating the geometry of the shell (jump and average of the extrinsic curvature as well as the intrinsic curvature) to the non-singular components of the bulk stress tensor on the sides of the thin shell. The equations are applied to spherically symmetric thin shells in vacuum. The shells are part of the vacuum, they carry no energy tensor. We classify these solutions of `thin shells of nothingness' in the pure Gauss-Bonnet theory. There are three types of solutions, with one, zero or two asymptotic regions respectively. The third kind of solution are wormholes. Although vacuum solutions, they have the appearance of mass in the asymptotic regions. It is striking that in this theory, exotic matter is not needed in order for wormholes to exist- they can exist even with no matter.
description: 13 pages, RevTex, 8 figures. Version 2: includes discussion on the well-defined thin shell limit. Version 3: typos fixed, a reference added, accepted for publication in Phys. Rev. D
The Sampling Method in Social and Economic Research; A Partial List of References
Creators: name: Larson, Nellie G.
name: Larson, Nellie G.
Publisher: name: Unknown
Year: 1941
Subjects: Research Methods/ Statistical Methods

description: Excerpts from the Foreword: This is a partial list of references to books, pamphlets and periodical articles in the English language, published between January 1928 and June 1940, which deal with the theory, technique and application of the sampling method in social and economic research, with particular reference to human populations. The bibliography is in two main parts. The first contains references on the theory and technique of sampling, and the second, references to studies using the sampling method. A section of the second part contains references to material on straw votes and polls of public opinion. An author and subject index is appended.
Large Scale Structure as a Probe of Gravitational Slip
Creators: name: Daniel, Scott F.
name: Caldwell, Robert R.
name: Cooray, Asantha
name: Melchiorri, Alessandro
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: A new time-dependent, scale-independent parameter, \varpi, is employed in a phenomenological model of the deviation from General Relativity in which the Newtonian and longitudinal gravitational potentials slip apart on cosmological scales as dark energy, assumed to be arising from a new theory of gravitation, appears to dominate the universe. A comparison is presented between \varpi and other parameterized post-Friedmannian models in the literature. The effect of \varpi on the cosmic microwave background anisotropy spectrum, the growth of large scale structure, the galaxy weak-lensing correlation function, and cross-correlations of cosmic microwave background anisotropy with galaxy clustering are illustrated. Cosmological models with conventional maximum likelihood parameters are shown to find agreement with a narrow range of gravitational slip.
description: 12 pages, 16 figures
Long-range exchange interaction between spin qubits mediated by a superconducting link at finite magnetic field
Creators: name: Rosado, Lucia Gonzalez
name: Hassler, Fabian
name: Catelani, Gianluigi
Publisher: name: arXiv
Year: 2020
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Solid state spin qubits are promising candidates for the realization of a quantum computer due to their long coherence times and easy electrical manipulation. However, spin-spin interactions, which are needed for entangling gates, have only limited range as they generally rely on tunneling between neighboring quantum dots. This severely constrains scalability. Proposals to extend the interaction range generally focus on coherent electron transport between dots or on extending the coupling range. Here, we study a setup where such an extension is obtained by using a superconductor as a quantum mediator. Because of its gap, the superconductor effectively acts as a long tunnel barrier. We analyze the impact of spin-orbit (SO) coupling, external magnetic fields, and the geometry of the superconductor. We show that while spin non-conserving tunneling between the dots and the superconductor due to SO coupling does not affect the exchange interaction, strong SO scattering in the superconducting bulk is detrimental. Moreover, we find that the addition of an external magnetic field decreases the strength of the exchange interaction. Fortunately, the geometry of the superconducting link offers a lot of room to optimize the interaction range, with gains of over an order of magnitude from a 2D film to a quasi-1D strip. We estimate that for superconductors with weak SO coupling (\textit{e.g.}, aluminum) exchange rates of up to 100\,MHz over a micron-scale range can be achieved with this setup in the presence of magnetic fields of the order of 100\,mT.
Low-mass star formation in Lynds 1333
Creators: name: Kun, M.
name: Nikolic, S.
name: Johansson, L. E. B.
name: Balog, Z.
name: Gaspar, A.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: Medium-resolution optical spectroscopy of the candidate YSOs associated with the small, nearby molecular cloud Lynds~1333 revealed four previously unknown classical T Tauri stars, two of which are components of a visual double, and a Class I source, IRAS 02086+7600. The spectroscopic data, together with new V,R_ C,I_C photometric and 2MASS J, H, and K_s data allowed us to estimate the masses and ages of the new T Tauri stars. We touch on the possible scenario of star formation in the region. L1333 is one of the smallest and nearest known star forming clouds, therefore it may be a suitable target for studying in detail the small scale structure of a star forming environment.
description: 7 pages, 4 figures, accepted by MNRAS
Geometric Langlands correspondence for D-modules in prime characteristic: the GL(n) case
Creators: name: Bezrukavnikov, Roman
name: Braverman, Alexander
Publisher: name: arXiv
Year: 2006
Subjects: subject: Algebraic Geometry (math.AG)
subject: Representation Theory (math.RT)
subject: FOS: Mathematics

description: Let X be a smooth projective curve over an algebraically closed field k of characteristic p>0. In this paper we explore the relation between algebraic D-modules on the moduli space $Bun_n$ of vector bundles of rank n on X and coherent sheaves on the moduli space $Loc_n$ of vector bundles endowed with a connection (in the way predicted by Beilinson and Drinfeld for k of characteristic 0). The main technical tools used in the paper are the geometry of the Hitchin system and the Azumaya property of the algebra of differential operators in characteristic p.
description: Dedicated to R.MacPherson on the occasion of his 60th birthday
Range-relaxed criteria for choosing the Lagrange multipliers in the Levenberg-Marquardt method
Creators: name: Leitao, A.
name: Margotti, F.
name: Svaiter, B. F.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics
subject: 65J20, 47J06

description: In this article we propose a novel strategy for choosing the Lagrange multipliers in the Levenberg-Marquardt method for solving ill-posed problems modeled by nonlinear operators acting between Hilbert spaces. Convergence analysis results are established for the proposed method, including: monotonicity of iteration error, geometrical decay of the residual, convergence for exact data, stability and semi-convergence for noisy data. Numerical experiments are presented for an elliptic parameter identification two-dimensional EIT problem. The performance of our strategy is compared with standard implementations of the Levenberg-Marquardt method (using a priori choice of the multipliers).
description: 25 pages, 3 figures, IMA Journal of Numerical Analysis (to appear)
Simulation of networks of spiking neurons: A review of tools and strategies
Creators: name: Brette, R.
name: Rudolph, M.
name: Carnevale, T.
name: Hines, M.
name: Beeman, D.
name: Bower, J. M.
name: Diesmann, M.
name: Morrison, A.
name: Goodman, P. H.
name: Harris, F. C.
name: Zirpe, M.
name: Natschlager, T.
name: Pecevski, D.
name: Ermentrout, B.
name: Djurfeldt, M.
name: Lansner, A.
name: Rochel, O.
name: Vieville, T.
name: Muller, E.
name: Davison, A. P.
name: Boustani, S. El
name: Destexhe, A.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Neurons and Cognition (q-bio.NC)
subject: FOS: Biological sciences

description: We review different aspects of the simulation of spiking neural networks. We start by reviewing the different types of simulation strategies and algorithms that are currently implemented. We next review the precision of those simulation strategies, in particular in cases where plasticity depends on the exact timing of the spikes. We overview different simulators and simulation environments presently available (restricted to those freely available, open source and documented). For each simulation tool, its advantages and pitfalls are reviewed, with an aim to allow the reader to identify which simulator is appropriate for a given task. Finally, we provide a series of benchmark simulations of different types of networks of spiking neurons, including Hodgkin-Huxley type, integrate-and-fire models, interacting with current-based or conductance-based synapses, using clock-driven or event-driven integration strategies. The same set of models are implemented on the different simulators, and the codes are made available. The ultimate goal of this review is to provide a resource to facilitate identifying the appropriate integration strategy and simulation tool to use for a given modeling problem related to spiking neural networks.
description: 49 pages, 24 figures, 1 table; review article, Journal of Computational Neuroscience, in press (2007)
A STUDY ON ANALYZING THE RELATIONSHIP BETWEEN EMPLOYEE ENGAGEMENT AND COST CONTROL MEASURES IN SAMUTHRAA TEX
Creators: name: Sanjuthaa
Publisher: name: Zenodo
Year: 2025
Subjects: Employee Engagement, Cost Control, Manufacturing Industry, Workforce Motivation, Operational Efficiency, Job Satisfaction, Resource Optimization, Samuthraa Tex., Karur.

description: Employee engagement plays a crucial role in the financial sustainability of organizations, particularly in manufacturing firms like Samuthraa Tex., Karur. This study examines the relationship between employee engagement and cost control measures, analyzing how workforce motivation, job satisfaction, and commitment impact cost reduction strategies. Through surveys and financial data analysis, the study identifies key engagement drivers that enhance efficiency and minimize operational expenses. The findings highlight that a highly engaged workforce contributes to better resource utilization, waste reduction, and overall cost optimization. Furthermore, effective leadership, employee participation, and incentive programs significantly influence engagement levels. This research provides valuable insights for management to implement engagement-driven cost control measures, ensuring long-term profitability and competitive advantage.
Quasi-geodesics in relativistic gravity
Creators: name: Faraoni, Valerio
name: Vachon, Geneviève
Publisher: name: arXiv
Year: 2020
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: A four-force parallel to the trajectory of a massive particle can always be eliminated by going to an affine parametrization, but the affine parameter is different from the proper time. The main application is to cosmology, in which elements of the cosmic fluid are subject to a pressure gradient parallel to their four-velocities. Natural implementations of parallel four-forces occur when the particle mass changes and in scalar-tensor cosmology.
description: 13 pages, no figures
Photon-assisted electron transport in graphene
Creators: name: Trauzettel, B.
name: Blanter, Ya. M.
name: Morpurgo, A. F.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Photon-assisted electron transport in ballistic graphene is analyzed using scattering theory. We show that the presence of an ac signal (applied to a gate electrode in a region of the system) has interesting consequences on electron transport in graphene, where the low energy dynamics is described by the Dirac equation. In particular, such a setup describes a feasible way to probe energy dependent transmission in graphene. This is of substantial interest because the energy dependence of transmission in mesoscopic graphene is the basis of many peculiar transport phenomena proposed in the recent literature. Furthermore, we discuss the relevance of our analysis of ac transport in graphene to the observability of zitterbewegung of electrons that behave as relativistic particles (but with a lower effective speed of light).
description: 5 pages, 2 figures
Noncommutative Balls and Mirror Quantum Spheres
Creators: name: Hong, Jeong Hee
name: Szymanski, Wojciech
Publisher: name: arXiv
Year: 2007
Subjects: subject: Operator Algebras (math.OA)
subject: Quantum Algebra (math.QA)
subject: FOS: Mathematics
subject: 46L65, 46L87

description: Noncommutative analogues of n-dimensional balls are defined by repeated application of the quantum double suspension to the classical low-dimensional spaces. In the `even-dimensional' case they correspond to the Twisted Canonical Commutation Relations of Pusz and Woronowicz. Then quantum spheres are constructed as double manifolds of noncommutative balls. Both C*-algebras and polynomial algebras of the objects in question are defined and analyzed, and their relations with previously known examples are presented. Our construction generalizes that of Hajac, Matthes and Szymanski for `dimension 2', and leads to a new class of quantum spheres (already on the C*-algebra level) in all `even-dimensions'.
description: 20 pages
Postmating isolation mechanisms between sympatric populations of three-spined sticklebacks
Creators: name: Vamosi, Steven Michael
Publisher: name: University of British Columbia
Year: 2009

description: A pair of sympatric three-spined stickleback species (Gasterosteus aculeatus complex) at Paxton Lake, Texada Island, British Columbia, Canada hybridize regularly, with 1% of the total adult population consisting of hybrids (McPhail 1992). Previous work has established the presence of significant, but imperfect, premating isolation mechanisms (Nagel 1994). I investigated two potential mechanisms of postulating isolation. The first was sexual selection against adult F₁ hybrids and the second was natural selection against juvenile F₁ hybrids. To test for sexual selection against adult F₁ hybrids, I examined the mating success of F₁ hybrid males and the habitat use of benthic and limnetic females. I conducted mate choice tests in which F₁ hybrid and limnetic males competed for wild limnetic females. I found significantly reduced mating success among F₁ hybrid males. Mean mating success of F₁ hybrid males was 33% that of limnetic males. Hatfield (1995) found that F₁ hybrid males nest in the open regions of the littoral zone, which is the same habitat used by nesting limnetic males. I investigated the habitat use of wild gravid females by placing minnow traps in two habitats (open and vegetated). A significantly higher number of limnetic females were trapped at the open site relative to benthic females and significantly more benthic females were trapped at the vegetated site. This observation confirms that F₁ hybrid males, by nesting in open areas, are predominantly sampling limnetic females. These results suggest that reduced mating success of F₁ hybrids may be an effective postmating isolation barrier between benthics and limnetics. I measured the survival and growth over two months of F₁ hybrid juveniles in an enclosure in the littoral zone in the presence of juveniles of both parental species. I did not detect any significant reduction in relative numbers of hybrids in two separate years and growth rates were similar to the average of the two parental species. Prey items consumed by juvenile F₁ hybrids showed substantial overlap with juveniles of the parental species, suggesting that juvenile F₁ hybrids exploit the same resources as the parental species. Natural selection against juvenile hybrids, at the stage in their life history at which I conducted my experiment, may not be a strong postmating isolation barrier reducing gene flow between benthics and limnetics.
The L_X--M relation of Clusters of Galaxies
Creators: name: Rykoff, E. S.
name: Evrard, A. E.
name: McKay, T. A.
name: Becker, M. R.
name: Johnston, D. E.
name: Koester, B. P.
name: Nord, B.
name: Rozo, E.
name: Sheldon, E. S.
name: Stanek, R.
name: Wechsler, R. H.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: We present a new measurement of the scaling relation between X-ray luminosity and total mass for 17,000 galaxy clusters in the maxBCG cluster sample. Stacking sub-samples within fixed ranges of optical richness, N_200, we measure the mean 0.1-2.4 keV X-ray luminosity, , from the ROSAT All-Sky Survey. The mean mass, , is measured from weak gravitational lensing of SDSS background galaxies (Johnston et al. 2007). For 9 <= N_200 < 200, the data are well fit by a power-law, /10^42 h^-2 erg/s = (12.6+1.4-1.3 (stat) +/- 1.6 (sys)) (/10^14 h^-1 M_sun)^1.65+/-0.13. The slope agrees to within 10% with previous estimates based on X-ray selected catalogs, implying that the covariance in L_X and N_200 at fixed halo mass is not large. The luminosity intercent is 30%, or 2σ, lower than determined from the X-ray flux-limited sample of Reiprich & Bohringer (2002), assuming hydrostatic equilibrium. This difference could arise from a combination of Malmquist bias and/or systematic error in hydrostatic mass estimates, both of which are expected. The intercept agrees with that derived by Stanek et al. (2006) using a model for the statistical correspondence between clusters and halos in a WMAP3 cosmology with power spectrum normalization sigma_8 = 0.85. Similar exercises applied to future data sets will allow constraints on the covariance among optical and hot gas properties of clusters at fixed mass.
description: 5 pages, 1 figure, MNRAS accepted
On hydrodynamic instability of chemical oscillations
Creators: name: Myagkov, N. N.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: Chaotic Dynamics (nlin.CD)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: A study was made of the instability that arises when acoustic and gravity waves propagate in an inhomogeneous medium which is characterized by oscillatory approach of the reaction coordinates to the steady state. It is shown that loss of stability can occur in two different ways: by bifurcation of the periodic solution and by Eckhaus bifurcation. It is considered how an introduced nonlinearity stabilizes the unstable modes when the controlling parameter passes through the bifurcation points.
description: 15 pages, 0 figures, 20 references
Density Perturbation in the Universe with Nontrivial Topology of Space-Time
Creators: name: Moskaliuk, S. S.
name: Nesteruk, A. V.
name: Sokolov, I. I.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: A space spectrum of density perturbation In the Universe with nontrivial topology of space-time is shown to become discrete.
description: 9 pages, Latex, no figures
Inner Structure of Spin^{c}(4) Gauge Potential on 4-Dimensional Manifolds
Creators: name: Liu, Xin
name: Duan, Yi-shi
name: Yang, Wen-li
name: Zhang, Yao-zhong
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The decomposition of $Spin^{c}(4)$ gauge potential in terms of the Dirac 4% -spinor is investigated, where an important characterizing equation $ΔA_μ=-λA_μ$ has been discovered. Here $λ$ is the vacuum expectation value of the spinor field, $λ=\Vert Φ\Vert ^{2}$, and $A_μ$ the twisting U(1) potential. It is found that when $λ$ takes constant values, the characterizing equation becomes an eigenvalue problem of the Laplacian operator. It provides a revenue to determine the modulus of the spinor field by using the Laplacian spectral theory. The above study could be useful in determining the spinor field and twisting potential in the Seiberg-Witten equations. Moreover, topological characteristic numbers of instantons in the self-dual sub-space are also discussed.
description: 11 pages
The infrared spectra of very large, compact, highly symmetric, polycyclic aromatic hydrocarbons (PAHs)
Creators: name: Bauschlicher,, Charles W.
name: Peeters, Els
name: Allamandola, Louis J.
Publisher: name: arXiv
Year: 2008
Subjects: subject: Astrophysics (astro-ph)
subject: FOS: Physical sciences

description: The mid-infrared spectra of large PAHs ranging from C54H18 to C130H28 are determined computationally using Density Functional Theory. Trends in the band positions and intensities as a function of PAH size, charge and geometry are discussed. Regarding the 3.3, 6.3 and 11.2 micron bands similar conclusions hold as with small PAHs. This does not hold for the other features. The larger PAH cations and anions produce bands at 7.8 micron and, as PAH sizes increases, a band near 8.5 micron becomes prominent and shifts slightly to the red. In addition, the average anion peak falls slightly to the red of the average cation peak. The similarity in behavior of the 7.8 and 8.6 micron bands with the astronomical observations suggests that they arise from large, cationic and anionic PAHs, with the specific peak position and profile reflecting the PAH cation to anion concentration ratio and relative intensities of PAH size. Hence, the broad astronomical 7.7 micron band is produced by a mixture of small and large PAH cations and anions, with small and large PAHs contributing more to the 7.6 and 7.8 micron component respectively. For the CH out-of-plane vibrations, the duo hydrogens couple with the solo vibrations and produce bands that fall at wavelengths slightly different than their counterparts in smaller PAHs. As a consequence, previously deduced PAH structures are altered in favor of more compact and symmetric forms. In addition, the overlap between the duo and trio bands may reproduce the blue-shaded 12.8 micron profile.
description: ApJ, 36 pages, 9 figs
Free-fall velocities and heat transport enhancement in liquid metal magneto-convection
Creators: name: Vogt, Tobias
name: Yang, Juancheng
name: Schindler, Felix
name: Eckert, Sven
Publisher: name: arXiv
Year: 2020
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: In geo- and astrophysics, low Prandtl number convective flows often interact with magnetic fields. Although a static magnetic field acts as a stabilizing force on such flow fields, we find that self-organized convective flow structures reach an optimal state where the heat transport significantly increases and convective velocities reach the theoretical free-fall limit, i.e. the maximum possible velocity a fluid parcel can achieve when its potential buoyant energy is fully converted into kinetic energy. Our measurements show that the application of a static magnetic field leads to an anisotropic, highly ordered flow structure and a decrease of the turbulent fluctuations. When the magnetic field strength is increased beyond the optimum, Hartmann braking becomes dominant and leads to a reduction of the heat and momentum transport. The results are relevant for the understanding of magneto-hydrodynamic convective flows in planetary cores and stellar interiors in regions with strong toroidal magnetic fields oriented perpendicular to temperature gradients.
The status of the quantum dissipation-fluctuation relation and Langevin equation
Creators: name: Taylor, J. C.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: I examine the arguments which have been given for quantum fluctuation-dissipation theorems. I distinguish between a weak form of the theorem, which is true under rather general conditions, and a strong form which requires a Langevin equation for its statement. I argue that the latter has not been reliably derived.
description: 9 pages
‘A divine right to photograph’: E. Graeme Robertson’s (1903–1975) historical motion pictures of National Hospital staff in 1933
Creators: name: Toodayan, Nadeem
name: Robertson, Denis G.
name: Anderson, Neil E.
name: Lees, Andrew J.
Publisher: name: Taylor & Francis
Year: 2024
Subjects: subject: Neuroscience
subject: Evolutionary Biology
subject: FOS: Biological sciences
subject: Ecology
subject: Sociology
subject: FOS: Sociology
subject: Cancer
subject: Mental Health

description: In the course of researching and writing the first-ever book length biography of Edward Graeme Robertson’s (1903–1975) eventful life and career in Australasian neurology, a rare 1933 cinema film recording of National Hospital staff at Queen Square has recently been rediscovered. Graeme completed his residency in neurology at Queen Square in the early 1930s and maintained close connections with his colleagues in London, thoughtfully recording them at different times using early movie cameras. Two versions of Graeme’s 1933 film have been preserved, and there are also other color clips of his colleagues from later in life in the UCL Neurology archives and Robertson family collection. These remarkable films contain images of several historically significant neurologists, including Gordon Morgan Holmes (1876–1965), Samuel Alexander Kinnier Wilson (1878–1937), Derek Denny-Brown (1901–1981), Macdonald Critchley (1900–1997), and several others. We provide a contextual summary of the many clips recorded alongside an in-depth inventory of all the personalities represented in the 1933 film. Selected photographs are used to indicate the contents of these remarkable films.