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Articles 1 - 14 of 14
Full-Text Articles in Physics
Effects Of Surfaces On Dynamic Percolation, H. K. Janssen, B. Schaub, Beate Schmittmann
Effects Of Surfaces On Dynamic Percolation, H. K. Janssen, B. Schaub, Beate Schmittmann
Beate Schmittmann
The general epidemic process, which is a stochastic multiparticle process belonging to the universality class of dynamic percolation, is studied in a semi-infinite geometry. Critical exponents characterizing the fractal properties are calculated to O(ε) (ε=6-d, where d is the spatial dimension) with use of renormalization-group techniques.
Modified Broyden’S Method For Accelerating Convergence In Self-Consistent Calculations, Duane D. Johnson
Modified Broyden’S Method For Accelerating Convergence In Self-Consistent Calculations, Duane D. Johnson
Duane D. Johnson
A modification to Broyden’s method for obtaining stable and computationally efficient convergence in self-consistent calculations is developed and discussed. The method incorporates the advantages of two schemes proposed by Srivastava and by Vanderbilt and Louie without any increase in complexity. Its improvement over their methods is discussed. The present method is compared with two other widely used convergence methods, simple mixing and Anderson’s method, for the case of the disordered binary alloy Ni0.35Fe0.65 on the verge of a magnetic instability and is shown to be much improved in stability and rate of convergence.
Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo
Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo
Alexander H. King
The role of interaction between slip dislocations and a Σ = 9 tilt boundary in localized microplastic deformation, cleavage, or intergranular fracture in the Li2 ordered structure has been analyzed by using the anisotropic elasticity theory of dislocations and fracture. Screw superpartials cross slip easily at the boundary onto the (1$\overline 1$1) and the (001) planes at low and high temperatures, respectively. Transmission of primary slip dislocations onto the conjugate slip system occurs with a certain degree of difficulty, which is eased by localized disordering. When the transmission is impeded, cleavage fracture on the ($\overline 1$11) plane is predicted to …
Constraints On Left-Right-Symmetric Models From Neutron Decay, As Carnoy, J Deutsch, Br Holstein
Constraints On Left-Right-Symmetric Models From Neutron Decay, As Carnoy, J Deutsch, Br Holstein
Barry R Holstein
The implications for left-right-symmetric models of recent neutron-β-decay asymmetry and lifetime measurements are analyzed. The significance of forthcoming high-precision lifetime measurements is stressed.
Ab Initio Approach To The Deuteron In The Skyrme-Witten Model, Alec Schramm
Ab Initio Approach To The Deuteron In The Skyrme-Witten Model, Alec Schramm
Alec J Schramm
No abstract provided.
A Calculation Of The Deuteron As A Biskyrmion, Alec Schramm, Yossef Dothan, L. Beidenharn
A Calculation Of The Deuteron As A Biskyrmion, Alec Schramm, Yossef Dothan, L. Beidenharn
Alec J Schramm
No abstract provided.
Effects Of Chemical And Magnetic Disorder In Fe0.50mn0.50, Duane D. Johnson, F. J. Pinski, G. M. Stocks
Effects Of Chemical And Magnetic Disorder In Fe0.50mn0.50, Duane D. Johnson, F. J. Pinski, G. M. Stocks
Duane D. Johnson
We present the results of first‐principles calculations of the total energy and spin‐polarized electronic structure of disordered fcc Fe0.50Mn0.50. These self‐consistent calculations were performed using the Korringa–Kohn–Rostoker method and the coherent‐potential approximation (KKR‐CPA), using the local‐spin‐density approximation to treat exchange and correlation. We use a lattice constant of a=6.80 a.u.; information about stability can be inferred from calculated pressure and energy. The moments on the Fe and Mn sites are large but antiparallel to each other, resulting in a small net magnetization. A comparison of the electronic structure is made for fcc Fe, Mn, and FeMn in both the ferromagnetic …
Theoretical Study Of The Hyperfine Fields Of Ni And Fe In Fcc Ni,Fe, Alloys, H. Ebert, H. Winter, B. L. Gyorffy, Duane D. Johnson, F. J. Pinski
Theoretical Study Of The Hyperfine Fields Of Ni And Fe In Fcc Ni,Fe, Alloys, H. Ebert, H. Winter, B. L. Gyorffy, Duane D. Johnson, F. J. Pinski
Duane D. Johnson
Using charge self-consistent cluster Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) band-structure calculations, the authors have studied the hyperfine fields on both Ni and Fe sites in the NixFe1-x alloys. To elucidate the influence of relativistic effects the hyperfine matrix elements have been calculated nonrelativistically as well as completely relativistically The dependence of the hyperfine fields on the environment of a given site has been studied by performing calculations for various atomic configurations around that site. The results of the work are compared with other theoretical data and with experiment.
Bubbles Without Cores, T. C. Shen
Bubbles Without Cores, T. C. Shen
T. -C. Shen
The decay of a false vacuum in a theory without a true vacuum is studied. Using variational arguments, we find that for a class of potentials of the type aφi+bφi (a>0, b<0 and i2φ2—ηφ3+ λφ4 is presented to discuss the transition from a thin-wall bubble to a thick-walled one. The validity conditions of using these solutions to describe the false vacuum decay within the framework of the semiclassical approximation are discussed.
Gauge-Invariance And Quantization, Br Holstein
Gauge-Invariance And Quantization, Br Holstein
Barry R Holstein
Quantizing theories such as quantum electrodynamics that contain a gauge invariance are discussed via a simple pedagogical example. Canonical and path integral quantization methods are compared.
Semiclassical Treatment Of The Double Well, Br Holstein
Semiclassical Treatment Of The Double Well, Br Holstein
Barry R Holstein
The double well potential V(x)= 1/4 λ(x2-α2)2 is addressed using both semiclassical path integral and instanton techniques. The basic physics of the two-state system is shown to arise, and energy levels calculated via the two methods are compared.
Comment On "Percolation In Isotropic Elastic Media.", Anthony Day, M. Thorpe
Comment On "Percolation In Isotropic Elastic Media.", Anthony Day, M. Thorpe
Anthony Roy Day
No abstract provided.
Spectral Dimensionality Of Random Superconducting Networks, Anthony Roy Day, W. Xia, M. F. Thorpe
Spectral Dimensionality Of Random Superconducting Networks, Anthony Roy Day, W. Xia, M. F. Thorpe
Anthony Roy Day
We compute the spectral dimensionality d-tilde of random superconducting-normal networks by directly examining the low-frequency density of states at the percolation threshold. We find that d-tilde=4.1±0.2 and 5.8±0.3 in two and three dimensions, respectively, which confirms the scaling relation d-tilde=2d/(2-s/ nu ), where s is the superconducting exponent and nu the correlation-length exponent for percolation. We also consider the one-dimensional problem where scaling arguments predict, and our numerical simulations confirm, that d-tilde=0. A simple argument provides an expression for the density of states of the localized high-frequency modes in this special case. We comment on the connection between our calculations …
Stability Of Networks Under Tension And Pressure, Anthony Roy Day, H. Yan, M. F. Thorpe
Stability Of Networks Under Tension And Pressure, Anthony Roy Day, H. Yan, M. F. Thorpe
Anthony Roy Day
The number of zero-frequency modes of an elastic network is an important quantity in determining the stability of the network. We present a constraint-counting method for finding this number in general central-force networks that are under an external tension. The technique involves isolating the backbone and then counting constraints in the same way as for free standing networks. A detailed example of this counting is given for a random two-dimensional network subject to an external tension. The results are shown to agree with the number of zero-frequency modes as determined by a direct matrix diagonalization.