34,287 research outputs found
The Guilty Mind
The doctrine of mens rea can be expressed in this way: MRP: If A is culpable for performing phi, then A performs phi intentionally in circumstances in which it is impermissible to perform phi. The Sermon on the Mount suggests the following principle: SMP: If A intends to perform phi in circumstances in which it would be impermissible for A to perform phi, then A’s intending to perform phi makes A as culpable as A would be were A to perform phi. MRP and SMP are principles representative of intentionalism, a family of views that emphasizes the importance of intention to judgments about culpability. This essay examines an intentionalist’s defense of MRP with respect to lying, strict criminal liability, and the distinction between intention and foreseeability, along with a defense of SMP with respect to failed attempts, and self-defens
Super Black Hole from Cosmological Supergravity with a Massive Superparticle
We describe in superspace a classical theory of two dimensional
cosmological dilaton supergravity coupled to a massive superparticle. We give
an exact non-trivial superspace solution for the compensator superfield that
describes the supergravity, and then use this solution to construct a model of
a two-dimensional supersymmetric black hole.Comment: 7 pages, Late
Suprathermal electron distributions in the solar transition region
Suprathermal tails are a common feature of solar wind electron velocity
distributions, and are expected in the solar corona. From the corona,
suprathermal electrons can propagate through the steep temperature gradient of
the transition region towards the chromosphere, and lead to non-Maxwellian
electron velocity distribution functions (VDFs) with pronounced suprathermal
tails. We calculate the evolution of a coronal electron distribution through
the transition region in order to quantify the suprathermal electron population
there. A kinetic model for electrons is used which is based on solving the
Boltzmann-Vlasov equation for electrons including Coulomb collisions with both
ions and electrons. Initial and chromospheric boundary conditions are
Maxwellian VDFs with densities and temperatures based on a background fluid
model. The coronal boundary condition has been adopted from earlier studies of
suprathermal electron formation in coronal loops. The model results show the
presence of strong suprathermal tails in transition region electron VDFs,
starting at energies of a few 10 eV. Above electron energies of 600 eV,
electrons can traverse the transition region essentially collision-free. The
presence of strong suprathermal tails in transition region electron VDFs shows
that the assumption of local thermodynamic equilibrium is not justified there.
This has a significant impact on ionization dynamics, as is shown in a
companion paper
Supergravity from a Massive Superparticle and the Simplest Super Black Hole
We describe in superspace a theory of a massive superparticle coupled to a
version of two dimensional N=1 dilaton supergravity. The (1+1) dimensional
supergravity is generated by the stress-energy of the superparticle, and the
evolution of the superparticle is reciprocally influenced by the supergravity.
We obtain exact superspace solutions for both the superparticle worldline and
the supergravity fields. We use the resultant non-trivial compensator
superfield solution to construct a model of a two-dimensional supersymmetric
black hole.Comment: Latex, 27 pages, minor typos corrected and reference adde
Conservation Laws and 2D Black Holes in Dilaton Gravity
A very general class of Lagrangians which couple scalar fields to gravitation
and matter in two spacetime dimensions is investigated. It is shown that a
vector field exists along whose flow lines the stress-energy tensor is
conserved, regardless of whether or not the equations of motion are satisfied
or if any Killing vectors exist. Conditions necessary for the existence of
Killing vectors are derived. A new set of 2D black hole solutions is obtained
for one particular member within this class of Lagrangians. One such solution
bears an interesting resemblance to the 2D string-theoretic black hole, yet
contains markedly different thermodynamic properties.Comment: 11 pgs. WATPHYS-TH92/0
Symmetry Breaking Using Value Precedence
We present a comprehensive study of the use of value precedence constraints
to break value symmetry. We first give a simple encoding of value precedence
into ternary constraints that is both efficient and effective at breaking
symmetry. We then extend value precedence to deal with a number of
generalizations like wreath value and partial interchangeability. We also show
that value precedence is closely related to lexicographical ordering. Finally,
we consider the interaction between value precedence and symmetry breaking
constraints for variable symmetries.Comment: 17th European Conference on Artificial Intelligenc
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Supporting Computer-supported collaborative work (CSCW) in conceptual design
In order to gain a better understanding of online conceptual collaborative design processes this paper investigates how student designers make use of a shared virtual synchronous environment when engaged in conceptual design. The software enables users to talk to each other and share sketches when they are remotely located. The paper describes a novel methodology for observing and analysing collaborative design processes by adapting the concepts of grounded theory. Rather than concentrating on narrow aspects of the final artefacts, emerging “themes” are generated that provide a broader picture of collaborative design process and context descriptions. Findings on the themes of “grounding – mutual understanding” and “support creativity” complement findings from other research, while important themes associated with “near-synchrony” have not been emphasised in other research. From the study, a series of design recommendations are made for the development of tools to support online computer-supported collaborative work in design using a shared virtual environment
Acceleration of phenological advance and warming with latitude over the past century.
In the Northern Hemisphere, springtime events are frequently reported as advancing more rapidly at higher latitudes, presumably due to an acceleration of warming with latitude. However, this assumption has not been investigated in an analytical framework that simultaneously examines acceleration of warming with latitude while accounting for variation in phenological time series characteristics that might also co-vary with latitude. We analyzed 743 phenological trend estimates spanning 86 years and 42.6 degrees of latitude in the Northern Hemisphere, as well as rates of Northern Hemisphere warming over the same period and latitudinal range. We detected significant patterns of co-variation in phenological time series characteristics that may confound estimates of the magnitude of variation in trends with latitude. Notably, shorter and more recent time series tended to produce the strongest phenological trends, and these also tended to be from higher latitude studies. However, accounting for such variation only slightly modified the relationship between rates of phenological advance and latitude, which was highly significant. Furthermore, warming has increased non-linearly with latitude over the past several decades, most strongly since 1998 and northward of 59°N latitude. The acceleration of warming with latitude has likely contributed to an acceleration of phenological advance along the same gradient
Higher Gauge Theory and Gravity in (2+1) Dimensions
Non-abelian higher gauge theory has recently emerged as a generalization of
standard gauge theory to higher dimensional (2-dimensional in the present
context) connection forms, and as such, it has been successfully applied to the
non-abelian generalizations of the Yang-Mills theory and 2-form
electrodynamics. (2+1)-dimensional gravity, on the other hand, has been a
fertile testing ground for many concepts related to classical and quantum
gravity, and it is therefore only natural to investigate whether we can find an
application of higher gauge theory in this latter context. In the present paper
we investigate the possibility of applying the formalism of higher gauge theory
to gravity in (2+1) dimensions, and we show that a nontrivial model of
(2+1)-dimensional gravity coupled to scalar and tensorial matter fields - the
model - can be formulated both as a standard gauge theory and
as a higher gauge theory. Since the model has a very rich structure - it admits
as solutions black-hole BTZ-like geometries, particle-like geometries as well
as Robertson-Friedman-Walker cosmological-like expanding geometries - this
opens a wide perspective for higher gauge theory to be tested and understood in
a relevant gravitational context. Additionally, it offers the possibility of
studying gravity in (2+1) dimensions coupled to matter in an entirely new
framework.Comment: 22 page
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