6,603 research outputs found
Evidences of evanescent Bloch waves in Phononic Crystals
We show both experimentally and theoretically the evanescent behaviour of
modes in the Band Gap (BG) of finite Phononic Crystal (PC). Based on
experimental and numerical data we obtain the imaginary part of the wave vector
in good agreement with the complex band structures obtained by the Extended
Plane Wave Expansion (EPWE). The calculated and measured acoustic field of a
localized mode out of the point defect inside the PC presents also evanescent
behaviour. The correct understanding of evanescent modes is fundamental for
designing narrow filters and wave guides based on Phononic Crystals with
defects.Comment: 8 pages, 3 figure
Real-time evolution of a large-scale relativistic jet
Context. Astrophysical jets are ubiquitous in the Universe on all scales, but
their large-scale dynamics and evolution in time are hard to observe since they
usually develop at a very slow pace.
Aims. We aim to obtain the first observational proof of the expected
large-scale evolution and interaction with the environment in an astrophysical
jet. Only jets from microquasars offer a chance to witness the real-time,
full-jet evolution within a human lifetime, since they combine a 'short', few
parsec length with relativistic velocities.
Methods. The methodology of this work is based on a systematic recalibraton
of interferometric radio observations of microquasars available in public
archives. In particular, radio observations of the microquasar GRS 1758-258
over less than two decades have provided the most striking results.
Results. Significant morphological variations in the extended jet structure
of GRS 1758-258 are reported here that were previously missed. Its northern
radio lobe underwent a major morphological variation that rendered the hotspot
undetectable in 2001 and reappeared again in the following years. The reported
changes confirm the Galactic nature of the source. We tentatively interpret
them in terms of the growth of instabilities in the jet flow. There is also
evidence of surrounding cocoon. These results can provide a testbed for models
accounting for the evolution of jets and their interaction with the
environment.Comment: 5 pages, 3 figures, 2 tables. Accepted for publication in Astronomy
and Astrophysics Letter
On the structure of the sets of mutually unbiased bases for N qubits
For a system of N qubits, spanning a Hilbert space of dimension d=2^N, it is
known that there exists d+1 mutually unbiased bases. Different construction
algorithms exist, and it is remarkable that different methods lead to sets of
bases with different properties as far as separability is concerned. Here we
derive the four sets of nine bases for three qubits, and show how they are
unitarily related. We also briefly discuss the four-qubit case, give the
entanglement structure of sixteen sets of bases,and show some of them, and
their interrelations, as examples. The extension of the method to the general
case of N qubits is outlined.Comment: 16 pages, 10 tables, 1 figur
Spatial analysis and site formation processes associated with the Middle Pleistocene hominid teeth from Q1/B waterhole, Boxgrove (West Sussex, UK)
Boxgrove is a key locale for our understanding of Middle Pleistocene human behaviour in Northwestern Europe. It provides high-resolution evidence for behaviour at scale in fine-grained sediments, dating from the end of the MIS13 interglacial at around 480,000 years ago. Excavations at this site in the last quarter of the twentieth century have provided a large body of interdisciplinary data, comprising stone artefact assemblages, well-preserved faunal remains and paleoenvironmental archives, from over 100 test pits and larger excavation areas. The excavation area designated Q1/B was excavated between 1995 and 1996 and provided a particularly deep and complex record of early human activity centred upon a pond or waterhole within the wider landscape. In this work, we present a new analysis of spatial data from a single sedimentary unit (Unit 4u) at the Boxgrove Q1/B site. We consider the spatial disposition of lithic and faunal materials, fabric analysis and the role of the palaeotopography in their distribution. The results indicate that, although the dynamic fluvial depositional environment had an undeniable role in the distribution of materials, the scale and nature of post-depositional movement are consistent with the artefacts being preserved within an autochthonous depositional context, not reworked from an earlier sedimentary unit or subject to long-distance transportation. These results are consistent with previous analysis which suggests that the overall lithic assemblage can be directly compared with others from the wider landscape in compositional terms to interpret the behavioural controls over site formation behind the Q1/B archaeology
Evanescent modes in Sonic Crystals: Complex relation dispersion and supercell approximation
Evanescent modes in complete sonic crystals (SC) and SC with point defects
are reported both theoretically and experimentally in this paper. Plane wave
expansion (PWE) and, in general, methods have been used to
calculate band structures showing gaps that have been interpreted as ranges of
frequencies where no real exists. In this work, we extend PWE to solve the
complex problem applied to SC, introducing the supercell
approximation for studying one vacancy. Explicit matrix formulation of the
equations is given. This method enables the calculation of complex
band structures, as well as enabling an analysis of the propagating modes
related with real values of the function , and the evanescent modes
related with imaginary values of . This paper shows theoretical
results and experimental evidences of the evanescent behavior of modes inside
the SC band gap. Experimental data and numerical results using the finite
elements method are in very good agreement with the predictions obtained using
the method.Comment: 15 pages, 3 figure
Sexist Attitudes in Online Video Gaming: Development and Validation of the Sexism Against Women Gamers Scale (SAWGS) in Spanish and English
Sexism is an increasingly prevalent problem in the gaming community. However, until now, assessment instruments focused on the construct “sexism against women gamers” are lacking. We present an 8-item self-report scale: Sexism Against Women Gamers Scale (SAWGS). We studied the reliability and validity of the scores of Spanish and English versions across five independent samples (N = 2,437), with participants from Spain and the United States. Scores on both versions demonstrated high reliability, while exploratory and confirmatory factor analyses supported their unidimensional structure. The analysis established configural, metric, and scalar invariance across gender. SAWGS was invariant at the configural level across countries. SAWGS scores were independent of social desirability, positively correlated with myths about intimate-partner violence against women, sexism, and social dominance orientation, and correlated negatively with feminism. Using two fictitious scenarios of sexism in online gaming, we found that gamers with higher scores on SAWGS showed a greater tendency to downplay a sexist incident and proposed a less severe punishment for toxic gamers. The SAWGS explained additional variance on responses to scenarios beyond that explained by other measures. The detection of sexism should make it possible to develop programs for its eradication and avoid negative consequences for women gamers
Certainty relations between local and nonlocal observables
We demonstrate that for an arbitrary number of identical particles, each
defined on a Hilbert-space of arbitrary dimension, there exists a whole ladder
of relations of complementarity between local, and every conceivable kind of
joint (or nonlocal) measurements. E.g., the more accurate we can know (by a
measurement) some joint property of three qubits (projecting the state onto a
tripartite entangled state), the less accurate some other property, local to
the three qubits, become. We also show that the corresponding complementarity
relations are particularly tight for particles defined on prime dimensional
Hilbert spaces.Comment: 4 pages, no figure
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