7,730 research outputs found
Fast Magnetosonic Waves Driven by Gravitational Waves
The propagation of a gravitational wave (GW) through a magnetized plasma is
considered. In particular, we study the excitation of fast magnetosonic waves
(MSW) by a gravitational wave, using the linearized general-relativistic
hydromagnetic equations. We derive the dispersion relation for the plasma,
treating the gravitational wave as a perturbation in a Minkowski background
space-time. We show that the presence of gravitational waves will drive
magnetosonic waves in the plasma and discuss the potential astrophysical
implications.Comment: 12 pages, 2 figures, Astronomy and Astrophysics in pres
A â3Pâ soft power model: an agile approach to diplomatic strategy
Soft power is the ability to shape the preferences of others through appeal and attraction rather than coerce using hard power. Today, most countries are embracing the notion of soft power. Managing soft power resources at the disposal of governments and deploying them effectively is critical for an agile government to build an attractive country image, and thereby enhancing their competitiveness in todayâs dynamic and competitive global landscape. This includes but not limited to promoting their countryâs products and services globally, attract foreign investors, and promoting international tourism. In this study, we develop and validate a novel â3Pâ soft power model, using the perceptions about a countryâs âproductsâ, âplacesâ, and âpeopleâ. Using 167 usable responses obtained from a structured country-wide survey in the UAE, the 3P model developed from the literature was tested for reliability, validity, and model-fitness. While Cronbachâs alpha values confirmed the reliability of first-order constructs (products, place and people), the second-order confirmatory factor analysis (CFA) established the convergent and discriminant validity of the constructs, and operationalization of â3P Soft Powerâ as a higher (second)-order model. The results have implications for governments and researchers in promoting soft power by leveraging its products, places and people. A robust higher-order factor model for soft power using 3Pâs has not been developed previously and constitutes the novelty of this study
How inflation, market capitalization, industrial production and the economic sentiment indicator affect the EU-12 stock markets
In the present study we map the relationship between the EU-12 stock market price indices and four crucial macroeconomic factors, using panel data analysis. The examined variables are market capitalization, industrial production, the economic sentiment indicator, and inflation, while the twelve countries are those which have adopted the euro. The empirical results reveal a strong effect of the first three factors, while inflation has a negative but not statistically significant coefficient. Further, the variables that affect the stock markets positively are market capitalization and the economic sentiment indicator. Finally, an applied statistical model confirms the significant convergence of the EU-12 stock markets in the long run, indicating a low geographic diversification across European markets.peer-reviewe
Towards Improved Forecasts of Atmospheric and Oceanic Circulations over the Complex Terrain of the Eastern Mediterranean
Forecasting atmospheric and oceanic circulations accurately over the Eastern Mediterranean has proved to be an exceptional challenge. The existence of fine-scale topographic variability (land/sea coverage) and seasonal dynamics variations can create strong spatial gradients in temperature, wind and other state variables, which numerical models may have difficulty capturing. The Hellenic Center for Marine Research (HCMR) is one of the main operational centers for wave forecasting in the eastern Mediterranean. Currently, HCMR's operational numerical weather/ocean prediction model is based on the coupled Eta/Princeton Ocean Model (POM). Since 1999, HCMR has also operated the POSEIDON floating buoys as a means of state-of-the-art, real-time observations of several oceanic and surface atmospheric variables. This study attempts a first assessment at improving both atmospheric and oceanic prediction by initializing a regional Numerical Weather Prediction (NWP) model with high-resolution sea surface temperatures (SST) from remotely sensed platforms in order to capture the small-scale characteristics
Matter flows around black holes and gravitational radiation
We develop and calibrate a new method for estimating the gravitational
radiation emitted by complex motions of matter sources in the vicinity of black
holes. We compute numerically the linearized curvature perturbations induced by
matter fields evolving in fixed black hole backgrounds, whose evolution we
obtain using the equations of relativistic hydrodynamics. The current
implementation of the proposal concerns non-rotating holes and axisymmetric
hydrodynamical motions. As first applications we study i) dust shells falling
onto the black hole isotropically from finite distance, ii) initially spherical
layers of material falling onto a moving black hole, and iii) anisotropic
collapse of shells. We focus on the dependence of the total gravitational wave
energy emission on the flow parameters, in particular shell thickness, velocity
and degree of anisotropy. The gradual excitation of the black hole quasi-normal
mode frequency by sufficiently compact shells is demonstrated and discussed. A
new prescription for generating physically reasonable initial data is
discussed, along with a range of technical issues relevant to numerical
relativity.Comment: 27 pages, 12 encapsulated figures, revtex, amsfonts, submitted to
Phys. Rev.
Reconstructing complex lineage trees from scRNA-seq data using MERLoT
Advances in single-cell transcriptomics techniques are revolutionizing studies of cellular differentiation and heterogeneity. It has become possible to track the trajectory of thousands of genes across the cellular lineage trees that represent the temporal emergence of cell types during dynamic processes. However, reconstruction of cellular lineage trees with more than a few cell fates has proved challenging. We present MERLoT (https://github.com/soedinglab/merlot), a flexible and user-friendly tool to reconstruct complex lineage trees from single-cell transcriptomics data. It can impute temporal gene expression profiles along the reconstructed tree. We show MERLoTâs capabilities on various real cases and hundreds of simulated datasets
Remarks on the Configuration Space Approach to Spin-Statistics
The angular momentum operators for a system of two spin-zero
indistinguishable particles are constructed, using Isham's Canonical Group
Quantization method. This mathematically rigorous method provides a hint at the
correct definition of (total) angular momentum operators, for arbitrary spin,
in a system of indistinguishable particles. The connection with other
configuration space approaches to spin-statistics is discussed, as well as the
relevance of the obtained results in view of a possible alternative proof of
the spin-statistics theorem.Comment: 18 page
Hidden geometric correlations in real multiplex networks
Real networks often form interacting parts of larger and more complex
systems. Examples can be found in different domains, ranging from the Internet
to structural and functional brain networks. Here, we show that these multiplex
systems are not random combinations of single network layers. Instead, they are
organized in specific ways dictated by hidden geometric correlations between
the individual layers. We find that these correlations are strong in different
real multiplexes, and form a key framework for answering many important
questions. Specifically, we show that these geometric correlations facilitate:
(i) the definition and detection of multidimensional communities, which are
sets of nodes that are simultaneously similar in multiple layers; (ii) accurate
trans-layer link prediction, where connections in one layer can be predicted by
observing the hidden geometric space of another layer; and (iii) efficient
targeted navigation in the multilayer system using only local knowledge, which
outperforms navigation in the single layers only if the geometric correlations
are sufficiently strong. Our findings uncover fundamental organizing principles
behind real multiplexes and can have important applications in diverse domains.Comment: Supplementary Materials available at
http://www.nature.com/nphys/journal/v12/n11/extref/nphys3812-s1.pd
The spinorial geometry of supersymmetric backgrounds
We propose a new method to solve the Killing spinor equations of
eleven-dimensional supergravity based on a description of spinors in terms of
forms and on the Spin(1,10) gauge symmetry of the supercovariant derivative. We
give the canonical form of Killing spinors for N=2 backgrounds provided that
one of the spinors represents the orbit of Spin(1,10) with stability subgroup
SU(5). We directly solve the Killing spinor equations of N=1 and some N=2, N=3
and N=4 backgrounds. In the N=2 case, we investigate backgrounds with SU(5) and
SU(4) invariant Killing spinors and compute the associated spacetime forms. We
find that N=2 backgrounds with SU(5) invariant Killing spinors admit a timelike
Killing vector and that the space transverse to the orbits of this vector field
is a Hermitian manifold with an SU(5)-structure. Furthermore, N=2 backgrounds
with SU(4) invariant Killing spinors admit two Killing vectors, one timelike
and one spacelike. The space transverse to the orbits of the former is an
almost Hermitian manifold with an SU(4)-structure and the latter leaves the
almost complex structure invariant. We explore the canonical form of Killing
spinors for backgrounds with extended, N>2, supersymmetry. We investigate a
class of N=3 and N=4 backgrounds with SU(4) invariant spinors. We find that in
both cases the space transverse to a timelike vector field is a Hermitian
manifold equipped with an SU(4)-structure and admits two holomorphic Killing
vector fields. We also present an application to M-theory Calabi-Yau
compactifications with fluxes to one-dimension.Comment: Latex, 54 pages, v2: clarifications made and references added. v3:
minor changes. v4: minor change
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