137 research outputs found
Protecting the past for the public good: archaeology and Australian heritage law
Archaeological remains have long been recognised as fragile evidence of the past, which require protection. Legal protection for archaeological heritage has existed in Australia for more than thirty years but there has been little analysis of the aims and effectiveness of that legislation by the archaeological profession. Much Australian heritage legislation was developed in a period where the dominant paradigm in archaeological theory and practice held that archaeology was an objective science. Australian legislative frameworks continue to strongly reflect this scientific paradigm and contemporary archaeological heritage management practice is in turn driven by these legislative requirements. This thesis examines whether archaeological heritage legislation is fulfilling its original intent. Analysis of legislative development in this thesis reveals that legislators viewed archaeological heritage as having a wide societal value, not solely or principally for the archaeological community. Archaeological heritage protection is considered within the broader philosophy of environmental conservation. As an environmental issue, it is suggested that a âpublic goodâ conservation paradigm is closer to the original intent of archaeological heritage legislation, rather than the âscientificâ paradigm which underlies much Australian legislation. Through investigation of the developmental history of Australian heritage legislation it is possible to observe how current practice has diverged from the original intent of the legislation, with New South Wales and Victoria serving as case studies. Further analysis is undertaken of the limited number of Australian court cases which have involved substantial archaeological issues to determine the courtâs attitude to archaeological heritage protection. Situating archaeological heritage protective legislation within the field of environmental law allows the examination of alternate modes of protecting archaeological heritage and creates opportunities for âpublic goodâ conservation outcomes. This shift of focus to âpublic goodâ conservation as an alternative to narrowly-conceived scientific outcomes better aligns with current public policy directions including the sustainability principles, as they have developed in Australia, as well as indigenous rights of self-determination. The thesis suggests areas for legal reforms which direct future archaeological heritage management practice to consider the âpublic goodâ values for archaeological heritage protection
Nonquasiparticle states in the half-metallic ferromagnet NiMnSb
Nonquasiparticle states above the Fermi energy are studied by first-principle
dynamical mean field calculations for a prototype half-metallic ferromagnet,
NiMnSb. We present a quantitative evaluation of the spectral weight of this
characteristic feature and discuss the possible experimental investigation
(BIS, NMR, STM and Andreev reflection) to clarify the existence of these
states.Comment: 15 pages, 4 figures, acepted in PR
Theory of Doping: Monovalent Adsorbates
Contains fulltext :
224022.pdf (Publisherâs version ) (Open Access
First- principle calculations of magnetic interactions in correlated systems
We present a novel approach to calculate the effective exchange interaction
parameters based on the realistic electronic structure of correlated magnetic
crystals in local approach with the frequency dependent self energy. The analog
of ``local force theorem'' in the density functional theory is proven for
highly correlated systems. The expressions for effective exchange parameters,
Dzialoshinskii- Moriya interaction, and magnetic anisotropy are derived. The
first-principle calculations of magnetic excitation spectrum for ferromagnetic
iron, with the local correlation effects from the numerically exact QMC-scheme
is presented.Comment: 17 pages, 3 Postscript figure
Demonstration of a quantum nondemolition sum gate
The sum gate is the canonical two-mode gate for universal quantum computation
based on continuous quantum variables. It represents the natural analogue to a
qubit C-NOT gate. In addition, the continuous-variable gate describes a quantum
nondemolition (QND) interaction between the quadrature components of two light
fields. We experimentally demonstrate a QND sum gate, employing the scheme by
R. Filip, P. Marek, and U.L. Andersen [\pra {\bf 71}, 042308 (2005)], solely
based on offline squeezed states, homodyne measurements, and feedforward. The
results are verified by simultaneously satisfying the criteria for QND
measurements in both conjugate quadratures.Comment: 4 pages, 4 figure
A note on cluster methods for strongly correlated electron systems
We develop, clarify and test various aspects of cluster methods dynamical
mean field methods using a soluble toy model as a benchmark. We find that the
Cellular Dynamical Mean Field Theory (C-DMFT) converges very rapidly and
compare its convergence properties with those of the Dynamical Cluster
Approximation (DCA). We propose and test improved estimators for the lattice
self energy within C-DMFT.Comment: 5 pages, 3 figures; major change
Dual boson approach to collective excitations in correlated fermionic systems
We develop a general theory of a boson decomposition for both local and
non-local interactions in lattice fermion models which allows us to describe
fermionic degrees of freedom and collective charge and spin excitations on
equal footing. An efficient perturbation theory in the interaction of the
fermionic and the bosonic degrees of freedom is constructed in so-called dual
variables in the path-integral formalism. This theory takes into account all
local correlations of fermions and collective bosonic modes and interpolates
between itinerant and localized regimes of electrons in solids. The zero-order
approximation of this theory corresponds to extended dynamical mean-field
theory (EDMFT), a regular way to calculate nonlocal corrections to EDMFT is
provided. It is shown that dual ladder summation gives a conserving
approximation beyond EDMFT. The method is especially suitable for consideration
of collective magnetic and charge excitations and allows to calculate their
renormalization with respect to "bare" RPA-like characteristics. General
expression for the plasmonic dispersion in correlated media is obtained. As an
illustration it is shown that effective superexchange interactions in the
half-filled Hubbard model can be derived within the dual-ladder approximation.Comment: Extended version, 17 pages, 5 figure
Correlated Electrons Step-by-Step: Itinerant-to-Localized Transition of Fe Impurities in Free-Electron Metal Hosts
High-resolution photoemission spectroscopy and realistic ab-initio
calculations have been employed to analyze the onset and progression of d-sp
hybridization in Fe impurities deposited on alkali metal films. The interplay
between delocalization, mediated by the free-electron environment, and Coulomb
interaction among d-electrons gives rise to complex electronic configurations.
The multiplet structure of a single Fe atom evolves and gradually dissolves
into a quasiparticle peak near the Fermi level with increasing the host
electron density. The effective multi-orbital impurity problem within the exact
diagonalization scheme describes the whole range of hybridizations.Comment: 10 pages, 4 figure
Effect of local Coulomb interactions on the electronic structure and exchange interactions in Mn12 magnetic molecules
We have studied the effect of local Coulomb interactions on the electronic
structure of the molecular magnet Mn12-acetate within the LDA+U approach. The
account of the on-site repulsion results in a finite energy gap and an integer
value of the molecule's magnetic moment, both quantities being in a good
agreement with the experimental results. The resulting magnetic moments and
charge states of non-equivalent manganese ions agree very well with
experiments. The calculated values of the intramolecular exchange parameters
depend on the molecule's spin configuration, differing by 25-30% between the
ferrimagnetic ground state and the completely ferromagnetic configurations. The
values of the ground-state exchange coupling parameters are in reasonable
agreement with the recent data on the magnetization jumps in megagauss magnetic
fields. Simple estimates show that the obtained exchange parameters can be
applied, at least qualitatively, to the description of the spin excitations in
Mn12-acetate.Comment: RevTeX, LaTeX2e, 4 EPS figure
Strong-coupling d-wave superconductivity in PuCoGa5 probed by point-contact spectroscopy
Superconductivity is due to an attractive interaction between electrons that, below a critical temperature, drives them to form Cooper pairs and to condense into a ground state separated by an energy gap from the unpaired states. In the simplest cases, the pairing is mediated by lattice vibrations and the wavefunction of the pairs is isotropic. Less conventional pairing mechanisms can favour more exotic symmetries of the Cooper pairs. Here, we report on point-contact spectroscopy measurements in PuCoGa5, a moderate heavy-fermion superconductor with a record high critical temperature Tc=18.5âK. The results prove that the wavefunction of the paired electrons has a d-wave symmetry, with four lobes and nodes, and show that the pairing is likely to be mediated by spin fluctuations. Electronic structure calculations, which take into account the full structure of the f-orbital multiplets of Pu, provide a hint of the possible origin of these fluctuations
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