Australian Journal of Physics最新文献

{"title":"Atomic radii from electron densities.","authors":"B. Etschmann, E. N. Maslen","doi":"10.1071/PH99028","DOIUrl":"https://doi.org/10.1071/PH99028","url":null,"abstract":"Bond lengths for diatomic molecules are predicted from atomic radii derived from free atom one-electron densities by postulating shielding factors for their valence electrons that depend on orbital angular momentum and on the bond order. The predicted values are closer to spectroscopically measured bond lengths than those based on earlier atomic radii inferred from a wider range of structural evidence. The bond lengths predicted by the sum of the atomic radii are corrected by a reduction that allows for charge transfer and by an extension associated with exchange repulsion of the overlapping electrons in the inter-nuclear region. Both corrections are related to free atom one-electron densities.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131635550","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}

{"title":"Exact causal bulk viscous stiff cosmologies.","authors":"M. Mak, T. Harko","doi":"10.1071/PH99067","DOIUrl":"https://doi.org/10.1071/PH99067","url":null,"abstract":"An exact solution of the gravitational fleld equations is presented for a homogeneous ∞at Friedmann{Robertson{Walker universe fllled with a causal bulk viscous ∞uid obeying the Zeldovich stifi equation of state and having bulk viscosity coe‐cient proportional to the fourth root of the energy density. Dissipative thermodynamic processes of bulk viscous type are supposed to play a crucial role in the dynamics and evolution of the early universe. Over thirty years ago Misner (1966) suggested that the observed large-scale isotropy of the universe is due to the action of the neutrino viscosity which was efiective when the universe was about 1 second old. There are many processes capable of producing bulk viscous stresses in the early universe, such as interaction between matter and radiation, quark and gluon plasma viscosity, strings and superstrings, difierent components of dark matter or particle creation (Chimento and Jakubi 1996). Traditionally the theories of Eckart (1940) and Landau and Lifshitz (1987) were used for the description of these phenomena. However, the results of Israel (1976), Israel and Stewart (1976) and Hiscock and Lindblom (1989) showed that the Eckart-type theories sufier from serious drawbacks concerning causality and stability. Regardless of the choice of equation of state, all equilibrium states in these theories are unstable and in addition signals may be propagated through the ∞uid at velocities exceeding the speed of light (Israel 1976; Israel and Stewart 1976; Hiscock and Lindblom 1989; Hiscock and Salmonson 1991). These problems arise due to the flrst-order nature of the theory, i.e. it considers only flrst-order deviations from equilibrium. The neglected second-order terms are necessary to prevent non-causal and unstable behaviour. A relativistic second-order theory was found by Israel (1976) and developed by Israel and Stewart (1976) into what is called ‘transient’ or ‘extended’ irreversible thermodynamics. Due to the complicated nonlinear character of the evolution equations, very few exact cosmological solutions of the gravitational fleld equations in the framework of the full causal theory are known. For a homogeneous universe fllled with a full causal viscous ∞uid source obeying the relation »»‰ 1 2 , exact general solutions of","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131380459","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}

{"title":"Some properties of the world crystal in fractal spacetime theory.","authors":"M. Agop, I. Oprea, C. Sandu, R. Vlad, C. Buzea, H. Matsuzawa","doi":"10.1071/PH99022","DOIUrl":"https://doi.org/10.1071/PH99022","url":null,"abstract":"We prove that the wave-particle duality, inertia and the Heisenberg uncertainty relation are properties of a fractal spacetime, self-structured by a gravitomagnetic background field, in the world crystal.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128307350","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}

{"title":"Time-dependent Quantum Waveguide Theory: A Study of Nano Ring Structures","authors":"S. Midgley, Jingbo Wang","doi":"10.1071/PH99043","DOIUrl":"https://doi.org/10.1071/PH99043","url":null,"abstract":"As electronic circuits get progressingly smaller to the nanometre scale, the quantum wave nature of the electrons starts to play a dominant role. It is thus possible for the devices to operate by controlling the phase of the quantum electron waves rather than the electron density as in present-day devices. This paper presents a highly accurate numerical method to treat quantum waveguides with arbitrarily complex geometry. Based on this model, a variety of quantum effects can be studied and quantified.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114417827","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}

{"title":"Phase transition properties of a finite ferroelectric superlattice from the transverse Ising model.","authors":"Xiao-guang Wang, Ning-ning Liu, S. Pan, Guo-zhen Yang","doi":"10.1071/PH000453","DOIUrl":"https://doi.org/10.1071/PH000453","url":null,"abstract":"We consider a finite ferroelectric superlattice in which the elementary unit cell is made up of 1 atomic layers of type A and n atomic layers of type B. Based on the transverse Ising model we examine the phase transition properties of the ferroelectric superlattice. Using the transfer matrix method we derive the equation for the Curie temperature of the superlattice. Numerical results are given for the dependence of the Curie temperature on the thickness and exchange constants of the superlattice.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"236 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115841187","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}

{"title":"Time Dynamics in Chaotic Many-body Systems: Can Chaos Destroy a Quantum Computer?","authors":"V. Flambaum","doi":"10.1071/PH99091","DOIUrl":"https://doi.org/10.1071/PH99091","url":null,"abstract":"Highly excited many-particle states in quantum systems (nuclei, atoms, quantum dots, spin systems, quantum computers) can be ‘chaotic’ superpositions of mean-field basis states (Slater determinants, products of spin or qubit states). This is a result of the very high energy level density of many-body states which can be easily mixed by a residual interaction between particles. We consider the time dynamics of wave functions and increase of entropy in such chaotic systems. As an example, we present the time evolution in a closed quantum computer. A time scale for the entropy S(t) increase is t c ~t 0 /(n log 2 n), where t 0 is the qubit ‘lifetime’, n is the number of qubits, S(0) = 0 and S(t c )=1. At t l t c the entropy is small: S ~nt 2 J 2 log 2 (1/t 2 J2 ), where J is the inter-qubit interaction strength. At t > t c the number of ‘wrong’ states increases exponentially as 2 S(t) . Therefore, t c may be interpreted as a maximal time for operation of a quantum computer. At t >>t c the system entropy approaches that for chaotic eigenstates.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121661650","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}

{"title":"Boltzmann equation theory of charged particle transport in neutral gases: perturbation treatment","authors":"S. Vrhovac, Z. Petrović","doi":"10.1071/PH99053","DOIUrl":"https://doi.org/10.1071/PH99053","url":null,"abstract":"This paper examines the formal structure of the Boltzmann equation (BE) theory of charged particle transport in neutral gases. The initial value problem of the BE is studied by using perturbation theory generalised to non-Hermitian operators. The method developed by Resibois was generalised in order to be applied for the derivation of the transport coecients of swarms of charged particles in gases. We reveal which intrinsic properties of the operators occurring in the kinetic equation are sucient for the generalised diffusion equation (GDE) and the density gradient expansion to be valid. Explicit expressions for transport coecients from the (asymmetric) eigenvalue problem are also deduced. We demonstrate the equivalence between these microscopic expressions and the hierarchy of kinetic equations. The establishment of the hydrodynamic regime is further analysed by using the time-dependent perturbation theory. We prove that for times t ? t0 (t0 is the relaxation time), the one-particle distribution function of swarm particles can be transformed into hydrodynamic form. Introducing time-dependent transport coecients ? *(p) (?q,t), which can be related to various Fourier components of the initial distribution function, we also show that for the long-time limit all ? *(p) (?q,t) become time and ?q independent in the same characteristic time and achieve their hydrodynamic values.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114144985","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}

{"title":"The motion of rapidly rotating curling rocks","authors":"M. R. Shegelski, R. Niebergall","doi":"10.1071/PH98064","DOIUrl":"https://doi.org/10.1071/PH98064","url":null,"abstract":"We present a physical model that accounts for the motion of rapidly rotating curling rocks. By rapidly rotating we mean that the rotational speed of the contact annulus of the rock about the centre of mass is large compared with the translational speed of the centre of mass. The principal features of the model are: (i ) that the kinetic friction induces melting of the ice, with the consequence that there exists a thin film of liquid water lying between the contact annulus of the rock and the ice; (ii ) that the curling rock drags some of the thin liquid film around the rock as it rotates, with the consequence that the relative velocity between the rock and the thin liquid film is significantly different to the relative velocity between the rock and the underlying solid ice surface. Since it is the former relative velocity which dictates the nature of the motion of the curling rock, our model predicts some interesting differences between the motions of slowly versus rapidly rotating rocks. Of principal note is that our model predicts, and observations confirm, that rapidly rotating curling rocks stop moving translationally well before rotational motion ceases. This is in sharp contrast to the usual case of slow rotation, where both rotational and translational motion cease at the same instant. We have verified this and other predictions of our model by careful comparison with the motion of actual curling rocks.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121123701","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}

{"title":"Non-leptonic B Meson Decays using Perturbative QCD","authors":"C. Dariescu, M. Dariescu","doi":"10.1071/ph99011","DOIUrl":"https://doi.org/10.1071/ph99011","url":null,"abstract":"Using perturbative QCD within the framework of Szczepaniak et al. (1990), we analyse different non-leptonic B decays, namely B → Π Π , B → Π (K)D, B → DD, as heavy-to-light transitions dominated by tree diagrams and compare our estimates to experimental data and other theoretical model predictions.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128876647","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}

{"title":"A Hartree—Fock program for atomic structure calculations","authors":"J. Mitroy","doi":"10.1071/PH99042","DOIUrl":"https://doi.org/10.1071/PH99042","url":null,"abstract":"The Hartree-Fock equations for a general open shell atom are described. The matrix equations that result when the single particle orbitals are written in terms of a linear combination of analytic basis functions are derived. Attention is paid to the complexities that occur when open shells are present. The specifics of a working FORTRAN program which is available for public use are described. The program has the flexibility to handle either Slater-type orbitals or Gaussian-type orbitals.","PeriodicalId":170873,"journal":{"name":"Australian Journal of Physics","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116995466","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}