1,593 research outputs found
Sighted: an overview
This article is an examination of audience responses to Sighted, two solo dance performances presented individually and simultaneously. The work was presented at venues related to different disciplines. Audience members, who numbered up to 20 and who were free to choose where to stand or move around the space and how to behave, were invited immediately following the performance to write down their responses. This was in order to elicit direct and undigested thoughts before conversation or dialogue has started. These, together with interviews with the dancers, form the basis for this research, which looks at the nature of venues and audiences and to what extent privately felt and communally understood audience commentary can correlate
Tree-ring analysis of winter climate variability and ENSO in Mediterranean California
The feasibility of using tree-ring data as a proxy for regional precipitation and ENSO events in the Mediterranean region of California is explored. A transect of
moisture-sensitive tree-ring sites, extending from southwestern to northcentral California, documents regional patterns of winter precipitation and replicates the regional response to ENSO events in the 20th century. Proxy records of ENSO were used with the tree-ring data to examine precipitation/ENSO patterns in the 18 and 19th centuries. Results suggest some temporal and spatial variability in the regional precipitation response to ENSO over the last three centuries
The Computational Power of Minkowski Spacetime
The Lorentzian length of a timelike curve connecting both endpoints of a
classical computation is a function of the path taken through Minkowski
spacetime. The associated runtime difference is due to time-dilation: the
phenomenon whereby an observer finds that another's physically identical ideal
clock has ticked at a different rate than their own clock. Using ideas
appearing in the framework of computational complexity theory, time-dilation is
quantified as an algorithmic resource by relating relativistic energy to an
th order polynomial time reduction at the completion of an observer's
journey. These results enable a comparison between the optimal quadratic
\emph{Grover speedup} from quantum computing and an speedup using
classical computers and relativistic effects. The goal is not to propose a
practical model of computation, but to probe the ultimate limits physics places
on computation.Comment: 6 pages, LaTeX, feedback welcom
Quantum Nature of the Big Bang: Improved dynamics
An improved Hamiltonian constraint operator is introduced in loop quantum
cosmology. Quantum dynamics of the spatially flat, isotropic model with a
massless scalar field is then studied in detail using analytical and numerical
methods. The scalar field continues to serve as `emergent time', the big bang
is again replaced by a quantum bounce, and quantum evolution remains
deterministic across the deep Planck regime. However, while with the
Hamiltonian constraint used so far in loop quantum cosmology the quantum bounce
can occur even at low matter densities, with the new Hamiltonian constraint it
occurs only at a Planck-scale density. Thus, the new quantum dynamics retains
the attractive features of current evolutions in loop quantum cosmology but, at
the same time, cures their main weakness.Comment: Typos corrected. Revised version to appear in Physical Review
A canonical transformation and the tunneling probability for the birth of an asymptotically DeSitter universe with dust
In the present work, we study the quantum cosmology description of closed
Friedmann-Robertson-Walker models in the presence of a positive cosmological
constant and a generic perfect fluid. We work in the Schutz's variational
formalism. If one uses the scale factor and its canonically conjugated momentum
as the phase space variables that describe the geometrical sector of these
models, one obtains Wheeler-DeWitt equations with operator ordering
ambiguities. In order to avoid those ambiguities and simplify the quantum
treatment of the models, we introduce new phase space variables. We explicitly
demonstrate that the transformation leading from the old set of variables to
the new one is canonical. In order to show that the above canonical
transformations simplify the quantum treatment of those models, we consider a
particular model where the perfect fluid is dust. We solve the Wheeler-DeWitt
equation numerically using the Crank-Nicholson scheme and determine the time
evolution of the initial wave function. Finally, we compare the results for the
present model with the ones for another model where the only difference is the
presence of a radiative perfect fluid, instead of dust.Comment: Revtex4, 18 pages, 2 EPS figure
Complete quantization of a diffeomorphism invariant field theory
In order to test the canonical quantization programme for general relativity
we introduce a reduced model for a real sector of complexified Ashtekar gravity
which captures important properties of the full theory. While it does not
correspond to a subset of Einstein's gravity it has the advantage that the
programme of canonical quantization can be carried out completely and
explicitly, both, via the reduced phase space approach or along the lines of
the algebraic quantization programme. This model stands in close correspondence
to the frequently treated cylindrically symmetric waves. In contrast to other
models that have been looked at up to now in terms of the new variables the
reduced phase space is infinite dimensional while the scalar constraint is
genuinely bilinear in the momenta. The infinite number of Dirac observables can
be expressed in compact and explicit form in terms of the original phase space
variables. They turn out, as expected, to be non-local and form naturally a set
of countable cardinality.Comment: 32p, LATE
Duality through the symplectic embedding formalism
In this work we show that we can obtain dual equivalent actions following the
symplectic formalism with the introduction of extra variables which enlarge the
phase space. We show that the results are equal as the one obtained with the
recently developed gauging iterative Noether dualization method (NDM). We
believe that, with the arbitrariness property of the zero mode, the symplectic
embedding method (SEM) is more profound since it can reveal a whole family of
dual equivalent actions. We illustrate the method demonstrating that the
gauge-invariance of the electromagnetic Maxwell Lagrangian broken by the
introduction of an explicit mass term and a topological term can be restored to
obtain the dual equivalent and gauge-invariant version of the theory.Comment: RevTeX4, 10 pages. To appear in Int. J. Mod. Phys.
Hamiltonian symplectic embedding of the massive noncommutative U(1) Theory
We show that the massive noncommutative U(1) theory is embedded in a gauge
theory using an alternative systematic way, which is based on the symplectic
framework. The embedded Hamiltonian density is obtained after a finite number
of steps in the iterative symplectic process, oppositely to the result proposed
using the BFFT formalism. This alternative formalism of embedding shows how to
get a set of dynamically equivalent embedded Hamiltonian densities.Comment: 16 pages, no figures, revtex4, corrected version, references
additione
Natural and projectively equivariant quantizations by means of Cartan Connections
The existence of a natural and projectively equivariant quantization in the
sense of Lecomte [20] was proved recently by M. Bordemann [4], using the
framework of Thomas-Whitehead connections. We give a new proof of existence
using the notion of Cartan projective connections and we obtain an explicit
formula in terms of these connections. Our method yields the existence of a
projectively equivariant quantization if and only if an \sl(m+1,\R)-equivariant
quantization exists in the flat situation in the sense of [18], thus solving
one of the problems left open by M. Bordemann.Comment: 13 page
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Solar PV Manufacturing Cost Model Group: Installed Solar PV System Prices
EERE's Solar Energy Technologies Program is charged with leading the Secretary's SunShot Initiative to reduce the cost of electricity from solar by 75% to be cost competitive with conventional energy sources without subsidy by the end of the decade. As part of this Initiative, the program has funded the National Renewable Energy Laboratory (NREL) to develop module manufacturing and solar PV system installation cost models to ensure that the program's cost reduction targets are carefully aligned with current and near term industry costs. The NREL cost analysis team has leveraged the laboratories' extensive experience in the areas of project finance and deployment, as well as industry partnerships, to develop cost models that mirror the project cost analysis tools used by project managers at leading U.S. installers. The cost models are constructed through a "bottoms-up" assessment of each major cost element, beginning with the system's bill of materials, labor requirements (type and hours) by component, site-specific charges, and soft costs. In addition to the relevant engineering, procurement, and construction costs, the models also consider all relevant costs to an installer, including labor burdens and overhead rates, supply chain costs, and overhead and materials inventory costs, and assume market-specific profits
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