Search

Your search keyword '"Levy, J. C."' showing total 332 results
Start Over Author "Levy, J. C."
332 results on '"Levy, J. C."'

1. Light Cones in Classical Dipole-Dipole Interacting Systems

Author

Batle, Josep, Cerdà, Joan J., Depondt, Ph., and Lévy, J. -C. S.

Subjects
Quantum Physics
Abstract

The speed at which the magnetic interaction propagates along a chain of classic dipoles is discussed here. While in the quantum information counterpart for long-range interacting spins, where the speed of propagation of the information plays a paramount role, it is not strictly clear whether a light cone exists or not, here we provide numerical evidence that interacting dipoles do posses a linear light cone shortly after a perturbation takes place. Specifically, a power-law expansion occurs which is followed by a linear propagation of the associated interaction. As opposed to the quantum case, and in analogy with the so-called speed of gravity problem, we find that the speed of propagation of information can be arbitrarily large in the classic context. In order to agree with special relativity, we propose the derivation of a frame-independent Landau-Lifshitz equation.

Published
2020

2. Unzipping DNA from the condensed globule state--Effects of unraveling

Author

Lam, Pui-Man and Levy, J. C.

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Statistical Mechanics
Abstract

We study theoretically the unzipping of a double stranded DNA from a condensed globule state by an external force. At constant force, we find that the double stranded DNA unzips an at critical force Fc and the number of unzipped monomers M goes as M~(Fc-F)^{-3}, for both the homogeneous and heterogeneous double stranded DNA sequence. This is different from the case of unzipping from an extended coil state in which the number of unzipped monomers M goes as M~(Fc-F)^{-chi}, where the exponent chi is either 1 or 2 depending on whether the double stranded DNA sequence is homogeneous or heterogeneous respectively. In the case of unzipping at constant extension, we find that for a double stranded DNA with a very large number N of base pairs, the force remains almost constant as a function of the extension, before the unraveling transition, at which the force drops abruptly to zero. Right at the unraveling transition, the number of base pairs remaining in the condensed globule state is still very large and goes as N^{3/4}, in agreement with theoretical predictions of the unraveling transition of polymers stretched by an external force., Comment: 17 pages, 4 figures

Published
2006

3. New magnetostatic modes in small nonellipsoidal magnetic particles

Author

Puszkarski, H., Krawczyk, M., and Levy, J. -C. S.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Magnetostatic normal modes are investigated here in elongated rods. The dipolar field resulting from the dipole-dipole interactions is calculated numerically in points of the axis connecting opposite rod face centers (\emph{central axis}) by collecting individual contributions to this field coming from each of the atomic planes perpendicular to the central axis. The applied magnetic field is assumed to be oriented along the central axis, and the magnetization to be uniform throughout the sample. The \emph{frequency} spectrum of magnetostatic waves propagating in the direction of the applied field is found numerically by solving the Landau-Lifshith equation of motion with the spatially \emph{nonhomogeneous} dipolar field taken into account; the mode amplitude \emph{profiles} are depicted as well. While energetically highest modes have \emph{bulk-extended} character, the modes forming the lower part of the spectrum are localized in the subsurface region (\emph{bulk-dead modes}). Between these two mode types, magnetostatic modes of a new type (\emph{comb modes}) are found to occur, characterized by two clearly discernible regions: a zone of fast amplitude oscillations inside the rod, and narrow slow-oscillation regions at the borders. Absorbing virtually no energy from an applied alternating field, comb modes will have no significant contribution to the magnetic noise., Comment: 16 pages, 6 figures, conferences paper: Physics of Magnetism'05, Poznan, Poland

Published
2005
Full Text
View/download PDF

4. Localization Properties of Quantized Magnetostatic Modes in Nanocubes

Author

Puszkarski, H., Krawczyk, M., and Levy, J. -C. S.

Subjects
Condensed Matter - Other Condensed Matter, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We investigate the dynamical properties of a system of interacting magnetic dipoles disposed in sites of an sc lattice and forming a cubic-shaped sample of size determined by the cube edge length (N-1)a (a being the lattice constant, N representing the number of dipolar planes). The dipolar field resulting from the dipole-dipole interactions is calculated numerically in points of the axis connecting opposite cube face centers (central axis) by collecting individual contributions to this field coming from each of the N atomic planes perpendicular to the central axis. The applied magnetic field is assumed to be oriented along the central axis, magnetizing uniformly the whole sample, all the dipoles being aligned parallelly in the direction of the applied field. The frequency spectrum of magnetostatic waves propagating in the direction of the applied field is found numerically by solving the Landau-Lifshitz equation of motion including the local (nonhomogeneous) dipolar field component; the mode amplitude spatial distributions (mode profiles) are depicted as well. It is found that only the two energetically highest modes have bulk-extended character. All the remaining modes are of localized nature; more precisely, the modes forming the lower part of the spectrum are localized in the subsurface region, while the upper-spectrum modes are localized around the sample center. We show that the mode localization regions narrow down as the cube size, N, increases (we investigated the range of N=21 to N=101), and in sufficiently large cubes one obtains practically only center-localized and surface-localized magnetostatic modes., Comment: 20 pages, 9 figures in postscript, useing Revtex4.cls

Published
2004
Full Text
View/download PDF

5. Excluded Volume Effect in Unzipping DNA with a Force

Author

Lam, Pui-Man, Levy, J. C. S., and Huang, Hanchen

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Statistical Mechanics
Abstract

A double stranded DNA molecule when pulled with a force acting on one end of the molecule can become either partially or completely unzipped depending on the magnitude of the force F. For a random DNA sequence, the number M of unzipped base pairs goes as M~(F-Fc)^(-2) and diverges at the critical force Fc with an exponent \chi=2. We find that when excluded volume effect is taken into account for the unzipped part of the DNA, the exponent \chi=2 is not changed but the critical force Fc is changed. The force versus temperature phase diagram depends on only two parameters in the model, the persistence length and the denaturation temperature. Furthermore a scaling form of the phase diagram can be found. This scaling form is parameter independent and depends only on the spatial dimension. It applies to all DNA molecules and should provide a useful framework for comparison with experiments., Comment: 4 figures

Published
2004

25. Irish endocrine society: Proceedings of 18th annual meeting held at Cork Regional Hospital, Wilton, Cork on November 5th & 6th, 1993

Author

Dimitriadis, E., Owens, D., Collins, P., Johnson, A., Tomkin, G., Cronin, C. C., Barry, D., Crowley, B., Ferriss, J. B., Hetherton, A. M., Smith, D. F., O’Herlihy, C., Smyth, P. P. A., Fiad, T. M., Culliton, M., Dunbar, J., Cunningham, S. K., McKenna, T. J., Heaney, A. P., Loughrey, G. L., McCance, D. R., Mcllrath, E., Hadden, D. R., Kennedy, L., Sheridan, B., Ferris, J. B., Whyte, A., Cleary, P. E., McAuley, D. J., Mathew, B., Bailey, I. C., Curtin, A., Lenehan, K., Deegan, P., Henry, M., Stapleton, M., Baker, H., Duggan, P. F., Mitchell, T. H., O’Hare, J. A., Geoghegan, M., Abuaisha, F., Fearon, U., Clarke, D., Roberts, R. N., Traub, A. I., Thompson, W., Whitehead, H., Holmes, J., Roberts, R., Al-Mandhari, N. A., Greer, A., Carson, D., Traub, T., Hadden, D., Heaney, A. P., Ferguson, T., Atkinson, A. B., O’Keeffe, S., Devlin, J. G., Donnellan, C., Russell, C. R., Kennedy, T. L., Kennedy, A. L., Atkinson, A. B., Long, H. A., Conway, D. J., Mercer, P. M., Murphy, D., Stokes, M., Sheahan, K., O’Higgins, N. J., Dunne, F. P., Ratcliffe, W. A., Mansour, P., Heath, D. A., O’Meara, N. M., Sturis, J., Herold, K. C., Polonsky, K. S., Beatty, O. L., Ritchie, C. M., Bell, P. M., Kennedy, A. L., Clarke, D., Fearon, U., Levy, J. C., Turkington, E., Hadden, D. W., Harper, R., Ennis, C. N., Johnston, G. D., Scanlan, P., Foley, M., Stronge, J., Firth, R., Hanson, R. L., Jacobsson, L. T. H., Bennett, P. H., Bishop, D. T., and Knowler, W. C.

Published
1994
Full Text
View/download PDF

48. Are Research Funds to Engineering Schools of Real Benefit to Industry? A British Viewpoint.

Author

Levy, J. C.

Abstract

Examines government and industry funding of engineering schools in Great Britain, and some collaborative research efforts between both sectors. Discusses the direct industry support of academic research and summarizes the factors that contribute to the importance to industry of research funding in engineering schools. (TW)

Published
1987

50. Irreversible evolution in the topology of magnetic domains (invited).

Author

Molho, P., Porteseil, J. L., Souche, Y., Gouzerh, J., and Levy, J. C. S.

Subjects
FERROMAGNETIC materials, MAGNETIC domain, FERRIMAGNETISM, BULK solids
Abstract

Presents a study which examined domain structures in a layer of a ferrimagnetic garnet. Similarity in the models for describing irreversibility in bulk materials; Definition of parameters needed to describe the domain structures in a ferrimagnetic garnet; Examples of topological evolution which illustrate the mechanisms responsible for reversible evolution in magnetic domains.

Published
1987
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results