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Spin-wave gap critical index for the quantum two-layer Heisenberg antiferromagnet at T e0 量子双层Heisenberg反铁磁体的自旋波间隙临界指数
Australian Journal of Physics Pub Date : 1999-10-01 DOI: 10.1071/PH98099
P. Shevchenko, O. Sushkov
{"title":"Spin-wave gap critical index for the quantum two-layer Heisenberg antiferromagnet at T e0","authors":"P. Shevchenko, O. Sushkov","doi":"10.1071/PH98099","DOIUrl":"https://doi.org/10.1071/PH98099","url":null,"abstract":"The two-layer Heisenberg antiferromagnet exhibits a zero temperature quantum phase transition from a disordered dimer phase to a collinear Neel phase, with long range order in the ground state. The spin-wave gap vanishes as Δ ∝ (J ⊥ – J ⊥ c) n approaching the transition point. To account for strong correlations, the S = 1 elementary excitations triplets are described as a dilute Bose gas with infinite on-site repulsion. We apply the Brueckner diagram approach which gives the critical index n ≈ 0 . 5. We demonstrate also that the linearised in density Brueckner equations give the mean field result n = 1. Finally, an expansion of the Brueckner equations in powers of the density, combined with the scaling hypothesis, gives n ≈ 0 . 67. This value agrees reasonably with that of the nonlinear O(3) σ model. Our approach demonstrates that for other quantum spin models the critical index can be different from that in the nonlinear σ model. We discuss the conditions for this to occur.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128742497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Quadratic solitons: new possibility for all-optical switching 二次孤子:全光开关的新可能性
Australian Journal of Physics Pub Date : 1999-08-01 DOI: 10.1071/PH98117
A. Buryak, V. Steblina
{"title":"Quadratic solitons: new possibility for all-optical switching","authors":"A. Buryak, V. Steblina","doi":"10.1071/PH98117","DOIUrl":"https://doi.org/10.1071/PH98117","url":null,"abstract":"We discuss potential applications of quadratic optical solitons for all-optical switching in bulk quadratic nonlinear media. Among the major phenomena investigated are soliton scattering, spiralling, fusion, and also power exchange between the colliding solitons.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"65 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116380516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Monte Carlo transport simulation techniques for stellarator fusion experiments 仿星器核聚变实验的蒙特卡罗输运模拟技术
Australian Journal of Physics Pub Date : 1999-08-01 DOI: 10.1071/PH98106
S. Dettrick, H. Gardner, S. Painter
{"title":"Monte Carlo transport simulation techniques for stellarator fusion experiments","authors":"S. Dettrick, H. Gardner, S. Painter","doi":"10.1071/PH98106","DOIUrl":"https://doi.org/10.1071/PH98106","url":null,"abstract":"We describe an implementation of a particle orbit-following simulation approach to the Monte Carlo calculation of neoclassical transport coecients which has been developed for application to the H-1NF Heliac. We compare and contrast some Monte Carlo transport coecient estimators that can be used in such computer codes, from both physical and computational perspectives, and we make recommendations for their use. Transport coecient calculations are performed for the H-1NF in conditions that will be available after the full National Facility upgrade.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128825721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
Forward-walking Green's function Monte Carlo method for correlation functions 正向行走格林函数的蒙特卡罗方法的相关函数
Australian Journal of Physics Pub Date : 1999-08-01 DOI: 10.1071/PH98092
M. Samaras, C. Hamer
{"title":"Forward-walking Green's function Monte Carlo method for correlation functions","authors":"M. Samaras, C. Hamer","doi":"10.1071/PH98092","DOIUrl":"https://doi.org/10.1071/PH98092","url":null,"abstract":"The forward-walking Green's Function Monte Carlo method is used to compute expectation values for the transverse Ising model in (1 p 1)D, and the results are compared with exact values. The magnetisation Mz and the correlation function p z (n) are computed. The algorithm reproduces the exact results, and convergence for the correlation functions seems almost as rapid as for local observables such as the magnetisation. The results are found to be sensitive to the trial wavefunction, however, especially at the critical point.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115714628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Cosmological particle production and casual thermodynamics 宇宙粒子的产生和偶然的热力学
Australian Journal of Physics Pub Date : 1999-08-01 DOI: 10.1071/PH99030
M. Mak, T. Harko
{"title":"Cosmological particle production and casual thermodynamics","authors":"M. Mak, T. Harko","doi":"10.1071/PH99030","DOIUrl":"https://doi.org/10.1071/PH99030","url":null,"abstract":"The full linear causal Israel–Stewart–Hiscock theory of bulk viscous processes in relativistic cosmological fluids is reformulated as an effective phenomenological theory for describing particle production processes in the early universe. Explicit expressions for the particle balance law and particle production rates are obtained that relate the particle creation rate to the bulk viscous (creation) pressure. The general formalism is applied to the case of a full causal cosmological fluid with bulk viscosity coecient proportional to the Hubble function. In this case the general solution of the gravitational field equations can be expressed in an exact parametric form. For an appropriate choice of the physical parameters, the dynamics of the universe can be modelled as starting from a vacuum quasi-Minkowskian geometry, followed by an inflationary period but ending in a non-inflationary phase. The influence of the matter creation processes on the evolution of the universe and the behaviour of the energy density, temperature and entropy are investigated.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"15 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129128083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 18
Magnetic stress in solar system plasmas 太阳系等离子体中的磁应力
Australian Journal of Physics Pub Date : 1999-08-01 DOI: 10.1071/PH98102
C. Russell
{"title":"Magnetic stress in solar system plasmas","authors":"C. Russell","doi":"10.1071/PH98102","DOIUrl":"https://doi.org/10.1071/PH98102","url":null,"abstract":"Magnetic stresses play an important role in the dynamics of geophysical systems, from deep inside the Earth to the tenuous plasmas of deep space. In the magnetic dynamos inside the sun and the planets, the magnetic stresses of necessity rival the interior mechanical stresses. In solar system plasmas, magnetic stresses play critical roles in the transfer of mass, momentum and energy from one region to another. Coronal mass ejections are rapidly expelled from the sun and their interplanetary manifestations plough through the pre-existing solar wind. Some of these structures resemble flux ropes, bundles of magnetic field wrapped around a central core, and some of these appear to be almost force-free. These structures and similar ones in planetary magnetospheres appear to be created by the mechanism of magnetic reconnection. Solar system plasmas generally organise themselves in giant cells in which the properties are rather uniform, separated by thin current layers across which the properties change rapidly. When the magnetic field on the two sides of one of these current layers changes direction significantly (by over 90°), the magnetic field on opposite sides of the boundary may become linked across the current sheet. If the resulting magnetic stress can accelerate the plasma out of the reconnection region, the process will continue uninterrupted. If not, the process will shut itself off. Such continuous reconnection can occur at the Earth’s magnetopause and those of the magnetised planets. Reconnection in the terrestrial magnetotail current sheet and the jovian current sheet occurs in a setting in which the flow can be blocked on one side, causing reconnection to be inherently time-varying. At Jupiter, this mechanism also separates heavy ions from magnetospheric flux tubes so that the ions can escape but Jupiter can retain its magnetic field. Despite the very wide range of parameters and scales encountered in heliospheric plasmas, there is surprising coherence in the mechanisms in these varying environments.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116914302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 10
Recent developments of resonant Auger transitions: predictions and propensity rules for the dynamic spin polarisation 共振俄歇跃迁的最新进展:动态自旋极化的预测和倾向规则
Australian Journal of Physics Pub Date : 1999-06-01 DOI: 10.1071/PH99019
B. Lohmann
{"title":"Recent developments of resonant Auger transitions: predictions and propensity rules for the dynamic spin polarisation","authors":"B. Lohmann","doi":"10.1071/PH99019","DOIUrl":"https://doi.org/10.1071/PH99019","url":null,"abstract":"The angular distribution and spin polarisation of the resonantly photoexcited Xe¤(4d–15/2 6p3/2 ) N5O2,3O2,3 Auger spectrum is investigated. The two-step model has been used which allows us to independently determine the dynamic parameters of the primary excitation and the Auger emission process. Assuming either a fully circularly or linearly polarised photon beam the dynamic parameters determining the primary photoexcitation become constant numbers independent of the matrix elements. Applying a relativistic distorted wave approximation the relevant numbers describing the Auger decay dynamics, i.e. relative intensities, angular distribution and spin polarisation parameters have been calculated, and are compared with experimental and other theoretical data. With this, predictions for the spin polarisation vector are possible. A large degree of dynamic spin polarisation has been found for all Auger transitions to a final state with Jf = h . This is in contrast to earlier calculations for diagram Auger transitions. Recently, we have given an explanation for this deriving propensity rules for resonant Auger transitions. The propensity rules allow for predictions for which Auger line a large dynamic spin polarisation can be expected. The predictions are in accord with our multiconfigurational Dirac–Fock calculations for the resonant Xe N5O2,3O2,3 and Ar L3M2,3M2,3 Auger multiplets. It is demonstrated that the effect of a large spin polarisation is caused by a large shift of the scattering phase of the emitted es1/2 partial waves, whereas a small spin polarisation is due to a cancellation between the Coulomb and scattering phases of the partial waves.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121150287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 10
Towards a direct numerical solution of Schrödinger's equation for ( e , 2 e ) reactions (e, 2e)反应的Schrödinger方程的直接数值解
Australian Journal of Physics Pub Date : 1999-06-01 DOI: 10.1071/PH98109
S. Jones, A. Stelbovics
{"title":"Towards a direct numerical solution of Schrödinger's equation for ( e , 2 e ) reactions","authors":"S. Jones, A. Stelbovics","doi":"10.1071/PH98109","DOIUrl":"https://doi.org/10.1071/PH98109","url":null,"abstract":"The finite-difference method for electron-hydrogen scattering is presented in a simple, easily understood form for a model collision problem in which all angular momentum is neglected. The model Schrodinger equation is integrated outwards from the atomic centre on a grid of fixed spacing h. The number of difference equations is reduced each step outwards using an algorithm due to Poet, resulting in a propagating solution of the partial-differential equation. By imposing correct asymptotic boundary conditions on this general, propagating solution, the particular solution that physically corresponds to scattering is obtained along with the scattering amplitudes. Previous works using finite differences (and finite elements) have extracted scattering amplitudes only for low-level transitions (elastic scattering and n = 2 excitation). If we are to eventually extract ionisation amplitudes, however, the numerical method must remain stable for higher-level transitions. Here we report converged cross sections for transitions up to n = 8, as a first step towards obtaining ionisation (e, 2e) results.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123805851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 4
Understanding multicentre electron orbitals by electron momentum spectroscopy 用电子动量谱法理解多中心电子轨道
Australian Journal of Physics Pub Date : 1999-06-01 DOI: 10.1071/PH98078
I. McCarthy, M. Vos
{"title":"Understanding multicentre electron orbitals by electron momentum spectroscopy","authors":"I. McCarthy, M. Vos","doi":"10.1071/PH98078","DOIUrl":"https://doi.org/10.1071/PH98078","url":null,"abstract":"Electron momentum spectroscopy can investigate qualitative predictions based on a physical understanding of the one-electron structure of a system. We describe examples of this understanding for molecules and solids.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"140 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123382730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Electron scattering from the ground and excited states of barium 电子从钡的基态和激发态散射
Australian Journal of Physics Pub Date : 1999-06-01 DOI: 10.1071/PH98085
D. Fursa
{"title":"Electron scattering from the ground and excited states of barium","authors":"D. Fursa","doi":"10.1071/PH98085","DOIUrl":"https://doi.org/10.1071/PH98085","url":null,"abstract":"We have used the nonrelativistic convergent close-coupling (CCC) method to investigate electron scattering from the ground (6s2)1S state and excited (6s6p)1 Po1 and (6s5d)1,3De2 states of barium. For the scattering from the barium ground state, we have found very good agreement with measurements of (6s6p)1 Po1 apparent cross sections at all energies. Similarly, good agreement is found for differential cross sections for elastic scattering and (6s6p)1 Po and (6s5d)1 De2 excitations and with the (6s6p)1 Po1 state electron{photon angular correlations. For the scattering from excited states of barium we have found good agreement with elastic (6s6p)1 Po1 scattering and the (6s5d)1De2 → (6s6p)1 Po1 transition for both differential cross sections and electron–photon angular correlations.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130471096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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