1,152 research outputs found
User Configuration of Activity Awareness
This paper describes an approach to user configuration of activity awareness. This approach offers users increased flexibility by allowing the use of multiple methods of configuration to be used within a unified framework; these configuration methods can include context, policy rules and automatic techniques of configuring behaviour. In this paper we describe the benefits of this flexibility and discuss a model of configuration that can be used to support these features
Finite temperature regularization
We present a non-perturbative regularization scheme for Quantum Field
Theories which amounts to an embedding of the originally unregularized theory
into a spacetime with an extra compactified dimensions of length L ~
Lambda^{-1} (with Lambda an ultraviolet cutoff), plus a doubling in the number
of fields, which satisfy different periodicity conditions and have opposite
Grassmann parity. The resulting regularized action may be interpreted, for the
fermionic case, as corresponding to a finite-temperature theory with a
supersymmetry, which is broken because of the boundary conditions. We test our
proposal in a perturbative calculation (the vacuum polarization graph for a
D-dimensional fermionic theory) and in a non-perturbative one (the chiral
anomaly).Comment: 17 pages, LaTeX fil
Recommended from our members
Precipitation and latent heating distributions from satellite passive microwave radiometry. Part I: improved method and uncertainties
A revised Bayesian algorithm for estimating surface rain rate, convective rain proportion, and latent heating profiles from satellite-borne passive microwave radiometer observations over ocean backgrounds is described. The algorithm searches a large database of cloud-radiative model simulations to find cloud profiles that are radiatively consistent with a given set of microwave radiance measurements. The properties of these radiatively consistent profiles are then composited to obtain best estimates of the observed properties. The revised algorithm is supported by an expanded and more physically consistent database of cloud-radiative model simulations. The algorithm also features a better quantification of the convective and nonconvective contributions to total rainfall, a new geographic database, and an improved representation of background radiances in rain-free regions. Bias and random error estimates are derived from applications of the algorithm to synthetic radiance data, based upon a subset of cloud-resolving model simulations, and from the Bayesian formulation itself. Synthetic rain-rate and latent heating estimates exhibit a trend of high (low) bias for low (high) retrieved values. The Bayesian estimates of random error are propagated to represent errors at coarser time and space resolutions, based upon applications of the algorithm to TRMM Microwave Imager (TMI) data. Errors in TMI instantaneous rain-rate estimates at 0.5°-resolution range from approximately 50% at 1 mm hâ1 to 20% at 14 mm hâ1. Errors in collocated spaceborne radar rain-rate estimates are roughly 50%â80% of the TMI errors at this resolution. The estimated algorithm random error in TMI rain rates at monthly, 2.5° resolution is relatively small (less than 6% at 5 mm dayâ1) in comparison with the random error resulting from infrequent satellite temporal sampling (8%â35% at the same rain rate). Percentage errors resulting from sampling decrease with increasing rain rate, and sampling errors in latent heating rates follow the same trend. Averaging over 3 months reduces sampling errors in rain rates to 6%â15% at 5 mm dayâ1, with proportionate reductions in latent heating sampling errors
\Lambda-buildings and base change functors
We prove an analog of the base change functor of \Lambda-trees in the setting
of generalized affine buildings. The proof is mainly based on local and global
combinatorics of the associated spherical buildings. As an application we
obtain that the class of generalized affine building is closed under ultracones
and asymptotic cones. Other applications involve a complex of groups
decompositions and fixed point theorems for certain classes of generalized
affine buildings.Comment: revised version, 29 pages, to appear in Geom. Dedicat
A Note on the Integral Formulation of Einstein's Equations Induced on a Braneworld
We revisit the integral formulation (or Green's function approach) of
Einstein's equations in the context of braneworlds. The integral formulation
has been proposed independently by several authors in the past, based on the
assumption that it is possible to give a reinterpretation of the local metric
field in curved spacetimes as an integral expression involving sources and
boundary conditions. This allows one to separate source-generated and
source-free contributions to the metric field. As a consequence, an exact
meaning to Mach's Principle can be achieved in the sense that only
source-generated (matter fields) contributions to the metric are allowed for;
universes which do not obey this condition would be non-Machian. In this paper,
we revisit this idea concentrating on a Randall-Sundrum-type model with a
non-trivial cosmology on the brane. We argue that the role of the surface term
(the source-free contribution) in the braneworld scenario may be quite subtler
than in the 4D formulation. This may pose, for instance, an interesting issue
to the cosmological constant problem.Comment: 10 pages, no figures, accepted for publication in the General
Relativity and Gravitation Journa
Responsible agriculture must adapt to the wetland character of midâlatitude peatlands
Drained, lowland agricultural peatlands are greenhouse gas (GHG) emission hotspots and a large but vulnerable store of irrecoverable carbon. They exhibit soil loss rates of ~2.0 cm yrâ1 and are estimated to account for 32% of global cropland emissions while producing only 1.1% of crop kilocalories. Carbon dioxide emissions account for >80% of their terrestrial GHG emissions and are largely controlled by water table depth. Reducing drainage depths is, therefore, essential for responsible peatland management. Peatland restoration can substantially reduce emissions. However, this may conflict with societal needs to maintain productive use, to protect food security and livelihoods. Wetland agriculture strategies will, therefore, be required to adapt agriculture to the wetland character of peatlands, and balance GHG mitigation against productivity, where halting emissions is not immediately possible. Paludiculture may substantially reduce GHG emissions but will not always be viable in the current economic landscape. Reduced drainage intensity systems may deliver partial reductions in the rate of emissions, with smaller modifications to existing systems. These compromise systems may face fewer hurdles to adoption and minimize environmental harm until societal conditions favour strategies that can halt emissions. Wetland agriculture will face agronomic, socio-economic and water management challenges, and careful implementation will be required. Diversity of values and priorities among stakeholders creates the potential for conflict. Successful implementation will require participatory research approaches and co-creation of workable solutions. Policymakers, private sector funders and researchers have key roles to play but adoption risks would fall predominantly on land managers. Development of a robust wetland agriculture paradigm is essential to deliver resilient production systems and wider environmental benefits. The challenge of responsible use presents an opportunity to rethink peatland management and create thriving, innovative and green wetland landscapes for everyone's future benefit, while making a vital contribution to global climate change mitigation
Quantum Mechanics and Leggett's Inequalities
We show that when the proper description of the behaviour of individual
photons or spin 1/2 particles in a spherically symmetric entangled pair is done
through the use of the density matrix, the Leggett's inequality is not violated
by quantum mechanics.Comment: 7 pages, no figures. A missing global sign in the r.h.s. of eq.
(4.10) in section 4 of version 1 (v1) invalidates the conclusion of that
particular section, which is then suppressed in the present version (v2
Continuous loading of a magnetic trap
We have realized a scheme for continuous loading of a magnetic trap (MT).
^{52}Cr atoms are continuously captured and cooled in a magneto-optical trap
(MOT). Optical pumping to a metastable state decouples atoms from the cooling
light. Due to their high magnetic moment (6 Bohr magnetons), low-field seeking
metastable atoms are trapped in the magnetic quadrupole field provided by the
MOT. Limited by inelastic collisions between atoms in the MOT and in the MT, we
load 10^8 metastable atoms at a rate of 10^8 atoms/s below 100 microkelvin into
the MT. After loading we can perform optical repumping to realize a MT of
ground state chromium atoms.Comment: 4 pages, 4 figures, version 2, modified references, included
additional detailed information, minor changes in figure 3 and in tex
Generalizations of entanglement based on coherent states and convex sets
Unentangled pure states on a bipartite system are exactly the coherent states
with respect to the group of local transformations. What aspects of the study
of entanglement are applicable to generalized coherent states? Conversely, what
can be learned about entanglement from the well-studied theory of coherent
states? With these questions in mind, we characterize unentangled pure states
as extremal states when considered as linear functionals on the local Lie
algebra. As a result, a relativized notion of purity emerges, showing that
there is a close relationship between purity, coherence and (non-)entanglement.
To a large extent, these concepts can be defined and studied in the even more
general setting of convex cones of states. Based on the idea that entanglement
is relative, we suggest considering these notions in the context of partially
ordered families of Lie algebras or convex cones, such as those that arise
naturally for multipartite systems. The study of entanglement includes notions
of local operations and, for information-theoretic purposes, entanglement
measures and ways of scaling systems to enable asymptotic developments. We
propose ways in which these may be generalized to the Lie-algebraic setting,
and to a lesser extent to the convex-cones setting. One of our original
motivations for this program is to understand the role of entanglement-like
concepts in condensed matter. We discuss how our work provides tools for
analyzing the correlations involved in quantum phase transitions and other
aspects of condensed-matter systems.Comment: 37 page
Investigating Genres and Perspectives in HCI Research on the Home
The home and domestic experiences have been studied from multiple points of view and disciplines, with an array of methodologies in the past twenty-five years in HCI. Given the attention to the home and the volume of research, what further areas of research might there be? Based on a critical analysis of 121 works on the topic, we present seven genres of domestic technology research in HCI: social routines in the home, ongoing domestic practices, the home as a testing ground, smart homes, contested values of a home, the home as a site for interpretation, and speculative visions of the home. We articulate dominant research perspectives in HCI, and we offer two complementary perspectives about how to investigate the domestic experience in future research: the material perspective and the first person perspective
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