52,389 research outputs found
Gravity with de Sitter and Unitary Tangent Groups
Einstein Gravity can be formulated as a gauge theory with the tangent space
respecting the Lorentz symmetry. In this paper we show that the dimension of
the tangent space can be larger than the dimension of the manifold and by
requiring the invariance of the theory with respect to 5d Lorentz group (de
Sitter group) Einstein theory is reproduced unambiguously. The other
possibility is to have unitary symmetry on a complex tangent space of the same
dimension as the manifold. In this case the resultant theory is
Einstein-Strauss Hermitian gravity. The tangent group is important for matter
couplings. We show that in the de Sitter case the 4 dimensional space time
vector and scalar are naturally unified by a hidden symmetry being components
of a 5d vector in the tangent space. With a de Sitter tangent group spinors can
exist only when they are made complex or taken in doublets in a way similar to
N=2 supersymmetry.Comment: 23 pages, one reference added.To be published in JHE
Non-Abelian statistics in the interference noise of the Moore-Read quantum Hall state
We propose noise oscillation measurements in a double point contact,
accessible with current technology, to seek for a signature of the non-abelian
nature of the \nu=5/2 quantum Hall state. Calculating the voltage and
temperature dependence of the current and noise oscillations, we predict the
non-abelian nature to materialize through a multiplicity of the possible
outcomes: two qualitatively different frequency dependences of the nonzero
interference noise. Comparison between our predictions for the Moore-Read state
with experiments on \nu=5/2 will serve as a much needed test for the nature of
the \nu=5/2 quantum Hall state.Comment: 4 pages, 4 figures v2: typo's corrected, discussions clarified,
references adde
Massive Hermitian Gravity
Einstein-Strauss Hermitian gravity was recently formulated as a gauge theory
where the tangent group is taken to be the pseudo-unitary group instead of the
orthogonal group. A Higgs mechanism for massive gravity was also formulated. We
generalize this construction to obtain massive Hermitian gravity with the use
of a complex Higgs multiplet. We show that both the graviton and antisymmetric
tensor acquire the same mass. At the linearized level, the theory is ghost free
around Minkowski background and describes a massive graviton with five degrees
of freedom and an antisymmetric field with three degrees of of freedom. We
determine the strong coupling scales for these degrees of freedom and argue
that the potential nonlinear ghosts, if they exist, have to decouple from the
gravitational degrees of freedom in strong coupling regime.Comment: 10 page
Development of sustainable biodegradable lignocellulosic hemp fiber/polycaprolactone biocomposites for light weight applications
Biocomposites with poly(ε-caprolactone) (PCL) as matrix and lignocellulosic hemp fiber with varying average aspect ratios (19, 26, 30 and 38) as reinforcement were prepared using twin extrusion process. The influence of fiber aspect ratio on the water absorption behavior and mechanical properties are investigated. The percentage of moisture uptake increased with the aspect ratio, following Fickian behavior. The hemp fiber/PCL biocomposites showed enhanced properties (tensile, flexural and low-velocity impact). The biocomposite with 26 aspect ratio showed the optimal properties, with flexural strength and modulus of 169% and 285% respectively, higher than those of neat PCL. However, a clear reduction on the mechanical properties was observed for water-immersed samples, with reduction in tensile and flexural moduli for the aspect ratio of 26 by 90% and 62%, respectively than those of dry samples. Summarily, the optimal sample provides an eco-friendly alternative to conventional, petroleum-based and non-renewable composites for various applications.Peer reviewedFinal Accepted Versio
Fluctuations, Saturation, and Diffractive Excitation in High Energy Collisions
Diffractive excitation is usually described by the Good--Walker formalism for
low masses, and by the triple-Regge formalism for high masses. In the
Good--Walker formalism the cross section is determined by the fluctuations in
the interaction. In this paper we show that by taking the fluctuations in the
BFKL ladder into account, it is possible to describe both low and high mass
excitation by the Good--Walker mechanism. In high energy collisions the
fluctuations are strongly suppressed by saturation, which implies that pomeron
exchange does not factorise between DIS and collisions. The Dipole Cascade
Model reproduces the expected triple-Regge form for the bare pomeron, and the
triple-pomeron coupling is estimated.Comment: 20 pages, 12 figure
X-ray induced persistent photoconductivity in Si-doped AlGaAs
We demonstrate that X-ray irradiation can be used to induce an
insulator-metal transition in Si-doped AlGaAs, a
semiconductor with {\it DX} centers. The excitation mechanism of the {\it DX}
centers into their shallow donor state was revealed by studying the
photoconductance along with fluorescence. The photoconductance as a function of
incident X-ray energy exhibits an edge both at the Ga and As K-edge, implying
that core-hole excitation of Ga and As are efficient primary steps for the
excitation of {\it DX} centers. A high quantum yield () suggests that
the excitation is indirect and nonlocal, due to secondary electrons, holes, and
fluorescence photons.Comment: 3 pages of text, 6 figures. An error in Fig.5 was detected, so we
corrected i
Coopetition of software firms in Open source software ecosystems
Software firms participate in an ecosystem as a part of their innovation
strategy to extend value creation beyond the firms boundary. Participation in
an open and independent environment also implies the competition among firms
with similar business models and targeted markets. Hence, firms need to
consider potential opportunities and challenges upfront. This study explores
how software firms interact with others in OSS ecosystems from a coopetition
perspective. We performed a quantitative and qualitative analysis of three OSS
projects. Finding shows that software firms emphasize the co-creation of common
value and partly react to the potential competitiveness on OSS ecosystems. Six
themes about coopetition were identified, including spanning gatekeepers,
securing communication, open-core sourcing and filtering shared code. Our work
contributes to software engineering research with a rich description of
coopetition in OSS ecosystems. Moreover, we also come up with several
implications for software firms in pursing a harmony participation in OSS
ecosystems.Comment: This is the author's version of the work. Copyright owner's version
can be accessed at
https://link.springer.com/chapter/10.1007/978-3-319-69191-6_10, Coopetition
of software firms in Open source software ecosystems, 8th ICSOB 2017, Essen,
Germany (2017
Stonemasons and craft mobility in the Bronze Age eastern Mediterranean
This chapter considers the evidence for craft mobility and cultural learning amongst stonemasons in the Bronze Age eastern Mediterranean. It draws on a range of cross-cultural comparative evidence, as well as placing particular emphasis on case studies from Egypt and the Aegean in the 3rd and 2nd millennium BC
Centrifuge modeling of rocking-isolated inelastic RC bridge piers
Experimental proof is provided of an unconventional seismic design concept, which is based on deliberately underdesigning shallow foundations to promote intense rocking oscillations and thereby to dramatically improve the seismic resilience of structures. Termed rocking isolation, this new seismic design philosophy is investigated through a series of dynamic centrifuge experiments on properly scaled models of a modern reinforced concrete (RC) bridge pier. The experimental method reproduces the nonlinear and inelastic response of both the soil-footing interface and the structure. To this end, a novel scale model RC (1:50 scale) that simulates reasonably well the elastic response and the failure of prototype RC elements is utilized, along with realistic representation of the soil behavior in a geotechnical centrifuge. A variety of seismic ground motions are considered as excitations. They result in consistent demonstrably beneficial performance of the rocking-isolated pier in comparison with the one designed conventionally. Seismic demand is reduced in terms of both inertial load and deck drift. Furthermore, foundation uplifting has a self-centering potential, whereas soil yielding is shown to provide a particularly effective energy dissipation mechanism, exhibiting significant resistance to cumulative damage. Thanks to such mechanisms, the rocking pier survived, with no signs of structural distress, a deleterious sequence of seismic motions that caused collapse of the conventionally designed pier. © 2014 The Authors Earthquake Engineering & Structural Dynamics Published by John Wiley & Sons Ltd
Pengaruh Citra Perusahaan dan Kepuasan terhadap Kepercayaan dan Dampaknya pada Loyalitas (Studi pada Klien Asuransi Prudential Pru Vision Kabupaten Pati)
This study aims to determine the influence company's image and satisfaction with trust andits impact to clients loyalty on Prudentials insurance Pru Vision Pati. Total sample are 100respondents, by using purposive sampling method with criteria that clients have become customersof at least 3 years. Analysis of the data in this study using regression analyzing. Hypothesis testingis used t calculated at the level of significance (α) 5%. Where mediation test using path analysis.Result of regression analysis in this study resulted in the coefficient of determination for 0,941 orin other words the changes in loyalty can be affected by the company's image, satisfaction andtrust of 4,1%. The results of this study show that company's image positive and significant impacton clients trust, satisfaction positive and significant impact on clients trust, company's imagepositive and significant impact on clients loyalty, satisfaction positive and significant impact onclients loyalty, trust positive and significant impact on clients loyalty, and trust does not mediatethe influence of company's image and satisfaction of the clients loyalty
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