18,146 research outputs found
Manganese-56 coincidence-counting facility precisely measures neutron-source strength
Precise measurement of neutron-source strength is provided by a manganese 56 coincidence-counting facility using the manganese-bath technique. This facility combines nuclear instrumentation with coincidence-counting techniques to handle a wide variety of radioisotope-counting requirements
Approximate Range Emptiness in Constant Time and Optimal Space
This paper studies the \emph{-approximate range emptiness} problem, where the task is to represent a set of points from and answer emptiness queries of the form " ?" with a probability of \emph{false positives} allowed. This generalizes the functionality of \emph{Bloom filters} from single point queries to any interval length . Setting the false positive rate to and performing queries, Bloom filters yield a solution to this problem with space bits, false positive probability bounded by for intervals of length up to , using query time . Our first contribution is to show that the space/error trade-off cannot be improved asymptotically: Any data structure for answering approximate range emptiness queries on intervals of length up to with false positive probability , must use space bits. On the positive side we show that the query time can be improved greatly, to constant time, while matching our space lower bound up to a lower order additive term. This result is achieved through a succinct data structure for (non-approximate 1d) range emptiness/reporting queries, which may be of independent interest
Monitoring of the prompt radio emission from the unusual supernova 2004dj in NGC2403
Supernova 2004dj in the nearby spiral galaxy NGC2403 was detected optically
in July 2004. Peaking at a magnitude of 11.2, this is the brightest supernova
detected for several years. Here we present Multi-Element Radio Linked
Interferometer Network (MERLIN) observations of this source, made over a four
month period, which give a position of R.A. = 07h37m17.044s, Dec
=+65deg35'57.84" (J2000.0). We also present a well-sampled 5 GHz light curve
covering the period from 5 August to 2 December 2004. With the exception of the
unusual and very close SN 1987A, these observations represent the first
detailed radio light curve for the prompt emission from a Type II-P supernova.Comment: (1) Jodrell Bank Observatory (2) University of Valencia (3)
University of Sheffield 6 pages, 1 figure. To appear in ApJ letter
Stable and Unstable Circular Strings in Inflationary Universes
It was shown by Garriga and Vilenkin that the circular shape of nucleated
cosmic strings, of zero loop-energy in de Sitter space, is stable in the sense
that the ratio of the mean fluctuation amplitude to the loop radius is
constant. This result can be generalized to all expanding strings (of non-zero
loop-energy) in de Sitter space. In other curved spacetimes the situation,
however, may be different.
In this paper we develop a general formalism treating fluctuations around
circular strings embedded in arbitrary spatially flat FRW spacetimes. As
examples we consider Minkowski space, de Sitter space and power law expanding
universes. In the special case of power law inflation we find that in certain
cases the fluctuations grow much slower that the radius of the underlying
unperturbed circular string. The inflation of the universe thus tends to wash
out the fluctuations and to stabilize these strings.Comment: 15 pages Latex, NORDITA 94/14-
DGNB building certification companion: Sustainability Tool for Assessment, Planning, Learning, and Engaging (STAPLE)
In the construction industry, the popularity of sustainability and its benefits have been on the rise in recent years. Alas, with various building sustainability assessment schemes on the market, there is still no single general method for a comprehensive and inclusive design and building process for sustainable buildings. The literature describes several barriers of entry preventing actors in the industry from seeking sustainability certifications and prioritizing design methods, supporting sustainability in greater numbers. In the newly developed tool, “DGNB building certification companion: Sustainable Tool for Assessment, Planning, Learning, and Engaging (STAPLE)”, a new Excel-based, interactive, and iterative education focused platform is introduced, intended to engage dialog among stakeholders, building owners, and decision makers, and the assigned group team leaders, based on the five DGNB topics. In order to establish common levels of knowledge, terminology, and understanding for proper interdisciplinary discussions, which would result in suitable and timely decisions, personal and professional development is enabled by imbedded educational documents in multiple formats throughout the tool as plain-language, easily digestible summaries of various topics regarding sustainability and the DGNB certification scheme. The identified barriers are described in the tool followed by a solution to overcome them. The tool, tested at multiple stages of development and moulded by many individuals both within and outside of the sustainable building industry, has shown to achieve the primary goals of assessment of individual’s current knowledge, educating through multiple stages and formats, and the inspiring of conversation among team members through a graphical display of opinions. Based on user feedback, the conclusion was that this is a desired product on the market. This new approach is expected to dramatically reduce misunderstandings, conflicts, and mistakes during a sustainable design process, helping the design team plan a project to possibly obtain the highest DGNB score if desired and properly documented
Exact Microscopic Entropy of Non-Supersymmetric Extremal Black Rings
In this brief note we show that the horizon entropy of the largest known
class of non-supersymmetric extremal black rings, with up to six parameters, is
exactly reproduced for all values of the ring radius using the same conformal
field theory of the four-charge four-dimensional black hole. A particularly
simple case is a dipole black ring without any conserved charges. The mass gets
renormalized, but the first corrections it receives can be easily understood as
an interaction potential energy. Finally, we stress that even if the entropy is
correctly reproduced, this only implies that one sector of chiral excitations
has been identified, but an understanding of excitations in the other sector is
still required in order to capture the black ring dynamics.Comment: 7 pages. v2: minor improvements, ref adde
A New Measurement of Cosmic Ray Composition at the Knee
The Dual Imaging Cerenkov Experiment (DICE) was designed and operated for
making elemental composition measurements of cosmic rays near the knee of the
spectrum at several PeV. Here we present the first results using this
experiment from the measurement of the average location of the depth of shower
maximum, , in the atmosphere as a function of particle energy. The value
of near the instrument threshold of ~0.1 PeV is consistent with
expectations from previous direct measurements. At higher energies there is
little change in composition up to ~5 PeV. Above this energy is deeper
than expected for a constant elemental composition implying the overall
elemental composition is becoming lighter above the knee region. These results
disagree with the idea that cosmic rays should become on average heavier above
the knee. Instead they suggest a transition to a qualitatively different
population of particles above 5 PeV.Comment: 7 pages, LaTeX, two eps figures, aas2pp4.sty and epsf.sty included,
accepted by Ap.J. Let
The Holographic Universe
We present a holographic description of four-dimensional single-scalar
inflationary universes in terms of a three-dimensional quantum field theory.
The holographic description correctly reproduces standard inflationary
predictions in their regime of applicability. In the opposite case, wherein
gravity is strongly coupled at early times, we propose a holographic
description in terms of perturbative QFT and present models capable of
satisfying the current observational constraints while exhibiting a
phenomenology distinct from standard inflation. This provides a qualitatively
new method for generating a nearly scale-invariant spectrum of primordial
cosmological perturbations.Comment: 20 pages, 5 figs; extended version of arXiv:0907.5542 including
background material and detailed derivations. To appear in Proceedings of 1st
Mediterranean Conference on Classical and Quantum Gravit
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