22,393 research outputs found
Testing formula satisfaction
We study the query complexity of testing for properties defined by read once formulae, as instances of massively parametrized properties, and prove several testability and non-testability results. First we prove the testability of any property accepted by a Boolean read-once formula involving any bounded arity gates, with a number of queries exponential in \epsilon and independent of all other parameters. When the gates are limited to being monotone, we prove that there is an estimation algorithm, that outputs an approximation of the distance of the input from
satisfying the property. For formulae only involving And/Or gates, we provide a more efficient test whose query complexity is only quasi-polynomial in \epsilon. On the other hand we show that such testability results do not hold in general for formulae over non-Boolean alphabets; specifically we construct a property defined by a read-once arity 2 (non-Boolean) formula over alphabets of size 4, such that any 1/4-test for it requires a number of queries depending on the formula size
Probing Unquenching Effects in the Gluon Polarisation in Light Mesons
We introduce an extension to the ladder truncated Bethe-Salpeter equation for
mesons and the rainbow truncated quark Dyson-Schwinger equations which includes
quark-loop corrections to the gluon propagator. This truncation scheme obeys
the axialvector Ward-Takahashi identity relating the quark self-energy and the
Bethe-Salpeter kernel. Two different approximations to the Yang-Mills sector
are used as input: the first is a sophisticated truncation of the full
Yang-Mills Dyson-Schwinger equations, the second is a phenomenologically
motivated form. We find that the spectra and decay constants of pseudoscalar
and vector mesons are overall described well for either approach. Meson mass
results for charge eigenstate vector and pseudoscalar meson masses are compared
to lattice data. The effects of unquenching the system are small but not
negligible.Comment: 26 pages, 13 figure
Gibbons-Hawking Effect in the Sonic de Sitter Space-Time of an Expanding Bose-Einstein-Condensed Gas
We propose an experimental scheme to observe the Gibbons-Hawking effect in
the acoustic analog of a 1+1-dimensional de Sitter universe, produced in an
expanding, cigar-shaped Bose-Einstein condensate. It is shown that a two-level
system created at the center of the trap, an atomic quantum dot interacting
with phonons, observes a thermal Bose distribution at the de Sitter
temperature.Comment: 4 pages, 2 figures, RevTex4; as publishe
Pressure-Induced Rotational Symmetry Breaking in URuSi
Phase transitions and symmetry are intimately linked. Melting of ice, for
example, restores translation invariance. The mysterious hidden order (HO)
phase of URuSi has, despite relentless research efforts, kept its
symmetry breaking element intangible. Here we present a high-resolution x-ray
diffraction study of the URuSi crystal structure as a function of
hydrostatic pressure. Below a critical pressure threshold kbar,
no tetragonal lattice symmetry breaking is observed even below the HO
transition K. For , however, a pressure-induced rotational
symmetry breaking is identified with an onset temperatures K.
The emergence of an orthorhombic phase is found and discussed in terms of an
electronic nematic order that appears unrelated to the HO, but with possible
relevance for the pressure-induced antiferromagnetic (AF) phase. Existing
theories describe the HO and AF phases through an adiabatic continuity of a
complex order parameter. Since none of these theories predicts a
pressure-induced nematic order, our finding adds an additional symmetry
breaking element to this long-standing problem.Comment: 6 pages, 4 figures and supplemental material
Assessment of fissionable material behaviour in fission chambers
A comprehensive study is performed in order to assess the pertinence of fission chambers coated with different fissile materials for high neutron flux detection. Three neutron scenarios are proposed to study the fast component of a high neutron flux: (i) high neutron flux with a significant thermal contribution such as BR2, (ii) DEMO magnetic fusion reactor, and (iii) IFMIF high flux test module.
In this study, the inventory code ACAB is used to analyze the following questions: (i) impact of different deposits in fission chambers; (ii) effect of the irradiation time/burn-up on the concentration; (iii) impact of activation cross-section uncertainties on the composition of the deposit for all the range of burn-up/irradiation neutron fluences of interest. The complete set of nuclear data (decay, fission yield, activation cross-sections, and uncertainties) provided in the EAF2007 data library are used for this evaluation
Near-tip analysis of crack propagation in cementitious composites
The fracture process zone encloses relevant mechanisms which explain the quasi-brittle behavior of cementitious composites. It is an important concept in non-linear fracture mechanics and in the simulation of cracking processes. The use of fibers as reinforcement may alter the crack initiation and propagation processes. A better understanding of the micro-cracking mechanisms taking place at the level of the fracture process zone is therefore relevant for an optimized design of these materials, as well as for the simulation of their mechanical behavior. In this study, the use of an image analysis procedure to capture the crack initiation and propagation process in concrete and other cementitious composites is described. It utilizes high resolution digital images of the surface of the specimens while undergoing the cracking process to determine the displacement fields. The formed cracks are observed at a relatively small scale, allowing the investigation and analysis of propagating cracks near the crack tip in specimens of concrete and other cementitious composites.Fundação para a Ciência e a Tecnologia (FCT
PEN as self-vetoing structural Material
Polyethylene Naphtalate (PEN) is a mechanically very favorable polymer.
Earlier it was found that thin foils made from PEN can have very high
radio-purity compared to other commercially available foils. In fact, PEN is
already in use for low background signal transmission applications (cables).
Recently it has been realized that PEN also has favorable scintillating
properties. In combination, this makes PEN a very promising candidate as a
self-vetoing structural material in low background experiments. Components
instrumented with light detectors could be built from PEN. This includes
detector holders, detector containments, signal transmission links, etc. The
current R\&D towards qualification of PEN as a self-vetoing low background
structural material is be presented.Comment: 4 pages, 7 figures, contribution to Proceedings of the sixth workshop
on Low Radioactivity Techniques 2017, 23-27 May 2017 Seoul, to be published
at AIP, editor: D. Leonar
Influence of Long-term Ingestion of Garcinia Kola Seed Diet on Sperm Count, Sperm Motility, and Fertility in the Wistar Rat
The influence of long-term ingestion of Garcinia kola seed on the sperm count, sperm motility, and fertility was investigated in the rat. Twenty adult Wistar rats initially weighing between 150 and 160 g were randomly divided into 2 groups (A and B) of 10 rats each. Group A animals served as control and were fed normal rat feed. Group B rats were fed Garcinia kola seed diet, obtained by mixing 20g of Garcinia kola seed powder and 80g of rat feed (20% w/w). The animals were allowed their respective diets and tap water ad libitum for 8 weeks. The results obtained revealed that there was a significant difference (p< 0.05) between the sperm count (16.42 × 106 ± 5.25 × 106/ml) and sperm motility(8.72 ± 2.33%) of the treatment group (Group B) and the respective values of the control, sperm count (89.38 × 106 ± 3.68 × 106/ml) and sperm motility (75.56 ± 1.23%). The findings suggest that long- term ingestion of Garcinia kola seed diet may cause a significant reduction in sperm count, sperm motility, and ultimately infertility in the male wistar rat. Keywords: Fertility; Sperm Count; Sperm Motility; Garcinia kola; Wistar rat.
The Momentum Constraints of General Relativity and Spatial Conformal Isometries
Transverse-tracefree (TT-) tensors on , with an
asymptotically flat metric of fast decay at infinity, are studied. When the
source tensor from which these TT tensors are constructed has fast fall-off at
infinity, TT tensors allow a multipole-type expansion. When has no
conformal Killing vectors (CKV's) it is proven that any finite but otherwise
arbitrary set of moments can be realized by a suitable TT tensor. When CKV's
exist there are obstructions -- certain (combinations of) moments have to
vanish -- which we study.Comment: 16 page
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