8,862 research outputs found
On a New Approach for Constructing Wormholes in Einstein-Born-Infeld Gravity
We study a new approach for the wormhole construction in Einstein-Born-Infeld
gravity, which does not require exotic matters in the Einstein equation. The
Born-Infeld field equation is not modified from "coordinate independent"
conditions of continuous metric tensor and its derivatives, even though the
Born-Infeld fields have discontinuities in their derivatives at the throat in
general. We study the relation of the newly introduced conditions with the
usual continuity equation for the energy-momentum tensor and the gravitational
Bianchi identity. We find that there is no violation of energy conditions for
the Born-Infeld fields contrary to the usual approaches. The exoticity of
energy-momentum tensor is not essential for sustaining wormholes. Some open
problems are discussed.Comment: Minor revision to improve the clarity, Corrected typos, Added
reference and footnot
Quasi-Normal Modes of a Natural AdS Wormhole in Einstein-Born-Infeld Gravity
We study the matter perturbations of a new AdS wormhole in (3+1)-dimensional
Einstein-Born-Infeld gravity, called "natural wormhole", which does not require
exotic matters. We discuss the stability of the perturbations by numerically
computing the quasi-normal modes (QNMs) of a massive scalar field in the
wormhole background. We investigate the dependence of quasi-normal frequencies
on the mass of scalar field as well as other parameters of the wormhole. It is
found that the perturbations are always stable for the wormhole geometry which
has the general relativity (GR) limit when the scalar field mass m satisfies a
certain, tachyonic mass bound m^2 > m^2_* with m^2_* < 0, analogous to the
Breitenlohner-Freedman (BF) bound in the global-AdS space, m^2_BF = 3 Lambda/4.
It is also found that the BF-like bound m^2_* shifts by the changes of the
cosmological constant Lambda or angular-momentum number l, with a level
crossing between the lowest complex and pure-imaginary modes for zero angular
momentum l = 0. Furthermore, it is found that the unstable modes can also have
oscillatory parts as well as non-oscillatory parts depending on whether the
real and imaginary parts of frequencies are dependent on each other or not,
contrary to arguments in the literature. For wormhole geometries which do not
have the GR limit, the BF-like bound does not occur and the perturbations are
stable for arbitrary tachyonic and non-tachyonic masses, up to a critical mass
m^2_c > 0 where the perturbations are completely frozen.Comment: Added comments and references, Accepted in EPJ
A Measurement-Driven Process Model For Managing Inconsistent Software Requirements
Inconsistency is a pervasive issue in software engineering. Both general rules of inconsistency management and special case-based approaches to handling inconsistency have recently been considered. In this paper, we present a process model for handling requirements inconsistency within the Viewpoints framework. In this process model, when an inconsistency among viewpoints is detected, a set of candidate proposals for handling inconsistency will be generated using techniques fromMulti-agent automated negotiations. The proposals are then prioritized using an integrated measurement of inconsistencies. The viewpoints involved in the inconsistency will then enter the negotiations by being presented with the candidate proposals and thus selecting an acceptable proposal based on the priorities associated with each candidate proposal. To facilitate usability, in our process, we assume that the natural language requirements statements are first translated into corresponding logical formulas using a translator software. Moreover, the candidate proposals for handling inconsistency are also translated back from formal logic into natural language before being presented for selection
A readily accessible multifunctional probe: simultaneous recognition of the cation ZN²⁺ and the anion F⁻ via distinguishable wavelengths
The probe 1 was readily prepared via condensation of 8-formyl-7-hydroxy-coumarin and carbonic dihydrazide in a one-step procedure. Probe 1 exhibited high sensitivity and selectivity towards Zn²⁺ and F⁻ through a “turn-on” fluorescence response and/or ratiometric colorimetric response with low detection limits of the order of 10-8 M. The complex behaviour was fully investigated by spectral titration, isothermal titration calorimetry, 1H NMR spectroscopic titration and mass spectrometry. Interestingly, probe 1 not only recognizes the cation Zn²⁺ and the anion F⁻, but can also distinguish between these two ions via the max wavelength in their UV-vis spectra (360 nm for 1-Zn²⁺ versus 400 nm for 1-F⁻ complex) or their fluorescent spectra (λₑₓ / λₑm = 360 nm/ 454 nm for 1-Zn²⁺ versus λₑₓ / λₑm = 400 nm/ 475 nm for 1-F⁻ complex) due to their differing red-shifts. Additionally, probe 1 has been further explored in the detection of Zn²⁺ in living cells
Central Engine-Powered Bright X-ray Flares in Short Gamma-Ray Bursts: A Hint of Black Hole-Neutron Star Merger?
Short gamma-ray bursts may originate from the merger of double neutron stars
(NS) or that of a black hole (BH) and an NS. We propose that the bright X-ray
flare related to the central engine reactivity may hint a BH-NS merger, since
such a merger can provide more fall-back materials and therefore a more massive
accretion disk than the NS-NS merger. Based on the observed 49 short bursts
with Swift/X-ray Telescope follow-up observations, we find that three bursts
have bright X-ray flares, among which three flares from two bursts are probably
related to the central engine reactivity. We argue that these two bursts may
originate from the BH-NS merger rather than the NS-NS merger. Our suggested
link between the central engine-powered bright X-ray flare and the BH-NS merger
event can be checked by the future gravitational wave detections from advanced
LIGO and Virgo.Comment: 15 pages, 6 figures, accepted for publication in Ap
Dataset for the proteomic and transcriptomic analyses of perivitelline fluid proteins in Pomacea snail eggs
This article describes how the proteomic and transcriptomic data were produced during a study of the reproductive proteins of Pomacea maculata, an aquatic apple snail laying colorful aerial eggs, and provides public access to the data. The data are related to a research article titled ?An integrated proteomic and transcriptomic analysis of perivitelline fluid proteins in a freshwater gastropod laying aerial eggs? (Mu et al., 2017) [1]. RNA was extracted from the albumen gland and other tissues and sequenced on an Illumina Hiseq. 2000. The assembled transcriptome was translated into protein sequences and then used for protein identification. Proteins from the perivitelline fluid of P. maculata were separated in SDS-PAGE and analyzed by LTQ-Orbitrap Elite coupled to an Easy-nLC. The translated transcriptome data are provided in this article. Proteomic data (.raw file format) are available via ProteomeXchange with the identifier PXD006718.Fil: Mu, Huawei. Hong Kong Baptist University; ChinaFil: Sun, Jin. Hong Kong University; ChinaFil: Heras, Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; ArgentinaFil: Chu, Ka Hou. Chinese University of Hong Kong; ChinaFil: Qiu, Jian Wen. Hong Kong Baptist University; Chin
Spectroscopy of -States in Quark Model and Baryon-Antibaryon Enhancements
We study the mass spectrum of the mesons both from
the quark model with triquark correlations and from common quark model with
colormagnetic interactions and with relative S-waves between quarks. Two
cluster configurations and
are considered. In the spectrum
we find rather stable states which have the same quantum number with particle
resonances which are corresponding to the enhancement,
enhancement and enhancement with
spin- or . This imply these enhancements are NOT
experimental artifacts. The color-spin-flavor structures of ,
, and enhancements are revealed. The
existence of spin-
enhancements is predicted.Comment: 45 pages, 5 figure
- …
