51 research outputs found
The Karlskrona manifesto for sustainability design
Sustainability is a central concern for our society, and software systems increasingly play a central role in it. As designers of software technology, we cause change and are responsible for the effects of our design choices. We recognize that there is a rapidly increasing awareness of the fundamental need and desire for a more sustainable world, and there is a lot of genuine goodwill. However, this alone will be ineffective unless we come to understand and address our persistent misperceptions. The Karlskrona Manifesto for Sustainability Design aims to initiate a much needed conversation in and beyond the software community by highlighting such perceptions and proposing a set of fundamental principles for sustainability design
On the Mass and Width of the Z-boson and Other Relativistic Quasistable Particles
The ambiguity in the definition for the mass and width of relativistic
resonances is discussed, in particular for the case of the Z-boson. This
ambiguity can be removed by requiring that a resonance's width
(defined by a Breit-Wigner lineshape) and lifetime (defined by the
exponential law) always and exactly fulfill the relation .
To justify this one needs relativistic Gamow vectors which in turn define the
resonance's mass M_R as the real part of the square root of
the S-matrix pole position s_R. For the Z-boson this means that and where M_Z and
are the values reported in the particle data tables.Comment: 23 page
Escape and Spreading Properties of Charge-Exchange Resonances in Bi 208
The properties of charge-exchange excitations of Pb with , i.e., the isobaric analog and Gamow-Teller resonances, are studied within
a self-consistent model making use of an effective force of the Skyrme type.
The well-known isobaric analog case is used to assess the reliability of the
model. The calculated properties of the Gamow-Teller resonance are compared
with recent experimental measurements with the aim of better understanding the
microscopic structure of this mode.Comment: 26 pages including references, figure captions and tables. Figures
are available upon request at [email protected] (decnet 32858::COLO).
Preprint code: IPNO/TH 94-2
Quasielastic Versus Inelastic and Deep Inelastic Lepton Scattering in Nuclei at x > 1
We have made a thorough investigation of the nuclear structure function W_2A
in the region of 0.8 < x < 1.5 and Q^2 < 20 GeV^2, separating the quasielastic
and inelastic plus deep inelastic contributions. The agreement with present
experimental data is good giving support to the results for both channels.
Predictions are made in yet unexplored regions of x and Q^2 to assert the
weight of the quasielastic or inelastic channels. We find that at Q^2 < 4 GeV^2
the structure function is dominated by the quasielastic contributions for x <
1.5, while for values of Q^2 > 15 GeV^2 and the range of x studied the
inelastic channels are over one order of magnitude bigger than the quasielastic
one. The potential of the structure function at x > 1 as a source of
information on nuclear correlations is stressed once more.Comment: 17 pages, LaTeX, 13 PostScript figures, final version to be published
in Nuclear Physics
Quasielastic K-nucleus scattering
Quasielastic K^+ - nucleus scattering data at q=290, 390 and 480 MeV/c are
analyzed in a finite nucleus continuum random phase approximation framework,
using a density-dependent particle-hole interaction. The reaction mechanism is
consistently treated according to Glauber theory, keeping up to two-step
inelastic processes. A good description of the data is achieved, also providing
a useful constraint on the strength of the effective particle-hole interaction
in the scalar-isoscalar channel at intermediate momentum transfers. We find no
evidence for the increase in the effective number of nucleons participating in
the reaction which has been reported in the literature.Comment: 21 pages, uses REVTeX and epsfig, 9 postscript figures; replaced
version corrects a few minor errors in the tex
Projective Hilbert space structures at exceptional points
A non-Hermitian complex symmetric 2x2 matrix toy model is used to study
projective Hilbert space structures in the vicinity of exceptional points
(EPs). The bi-orthogonal eigenvectors of a diagonalizable matrix are
Puiseux-expanded in terms of the root vectors at the EP. It is shown that the
apparent contradiction between the two incompatible normalization conditions
with finite and singular behavior in the EP-limit can be resolved by
projectively extending the original Hilbert space. The complementary
normalization conditions correspond then to two different affine charts of this
enlarged projective Hilbert space. Geometric phase and phase jump behavior are
analyzed and the usefulness of the phase rigidity as measure for the distance
to EP configurations is demonstrated. Finally, EP-related aspects of
PT-symmetrically extended Quantum Mechanics are discussed and a conjecture
concerning the quantum brachistochrone problem is formulated.Comment: 20 pages; discussion extended, refs added; bug correcte
Self-consistent Green's function method for nuclei and nuclear matter
Recent results obtained by applying the method of self-consistent Green's
functions to nuclei and nuclear matter are reviewed. Particular attention is
given to the description of experimental data obtained from the (e,e'p) and
(e,e'2N) reactions that determine one and two-nucleon removal probabilities in
nuclei since the corresponding amplitudes are directly related to the imaginary
parts of the single-particle and two-particle propagators. For this reason and
the fact that these amplitudes can now be calculated with the inclusion of all
the relevant physical processes, it is useful to explore the efficacy of the
method of self-consistent Green's functions in describing these experimental
data. Results for both finite nuclei and nuclear matter are discussed with
particular emphasis on clarifying the role of short-range correlations in
determining various experimental quantities. The important role of long-range
correlations in determining the structure of low-energy correlations is also
documented. For a complete understanding of nuclear phenomena it is therefore
essential to include both types of physical correlations. We demonstrate that
recent experimental results for these reactions combined with the reported
theoretical calculations yield a very clear understanding of the properties of
{\em all} protons in the nucleus. We propose that this knowledge of the
properties of constituent fermions in a correlated many-body system is a unique
feature of nuclear physics.Comment: 110 pages, accepted for publication on Prog. Part. Nucl. Phy
Massively distributed authorship of academic papers
Wiki-like or crowdsourcing models of collaboration can provide a number of benefits to academic work. These techniques may engage expertise from different disciplines, and potentially increase productivity. This paper presents a model of massively distributed collaborative authorship of academic papers. This model, developed by a collective of thirty authors, identifies key tools and techniques that would be necessary or useful to the writing process. The process of collaboratively writing this paper was used to discover, negotiate, and document issues in massively authored scholarship. Our work provides the first extensive discussion of the experiential aspects of large-scale collaborative research.Peer ReviewedPostprint (author's final draft
ICT4S 2029: What Will Be The Systems Supporting Sustainability in 15 Years
Research is often inspired by visions of the future. These visions can take on various narrative forms, and can fall anywhere along the spectrum from utopian to dystopian. Even though we recognize the importance of such visions to help us shape research questions and inspire rich design spaces to be explored, the opportunity to discuss them is rarely given in a research context. Imagine how civilization will have changed in 15 years. What is your vision for systems that will be supporting sustainability in that time Which transformational changes will have occurred in the mean time that allow for these systems Is ICT even the right tool or does it contradict sustainability by making our world ever more complex How can we make systems and our societies more sustainable and resilient by ICT4S This paper presents a compilation of fictional abstracts for inspiration and discussion, and provides means to stimulate discussion on future research and contributes to ICT4S community building
Neutron-induced nucleosynthesis
Neutron--induced nucleosynthesis plays an important role in astrophysical
scenarios like in primordial nucleosynthesis in the early universe, in the
s--process occurring in Red Giants, and in the --rich freeze--out and
r--process taking place in supernovae of type II. A review of the three
important aspects of neutron--induced nucleosynthesis is given: astrophysical
background, experimental methods and theoretical models for determining
reaction cross sections and reaction rates at thermonuclear energies. Three
specific examples of neutron capture at thermal and thermonuclear energies are
discussed in some detail.Comment: 40 pages (uses kluwer.sty), 2 postscript figures (uses psfig),
accepted for publication in Surveys in Geophysics, uuencoded tex-files and
postscript-files available at ftp://is1.kph.tuwien.ac.at/pub/ohu/Geo.u
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