2,304 research outputs found
Laser frequency combs and ultracold neutrons to probe braneworlds through induced matter swapping between branes
This paper investigates a new experimental framework to test the braneworld
hypothesis. Recent theoretical results have shown the possibility of matter
exchange between branes under the influence of suitable magnetic vector
potentials. It is shown that the required conditions might be achieved with
present-day technology. The experiment uses a source of pulsed and coherent
electromagnetic radiation and relies on the Hansch frequency comb technique
well-known in ultrahigh-precision spectroscopy. A good matter candidate for
testing the hypothesis is a polarized ultracold neutron gas for which the
number of swapped neutrons is measured.Comment: 14 pages, 4 figures. Published version. Published in Phys. Rev.
Artificially induced positronium oscillations in a two-sheeted spacetime: consequences on the observed decay processes
Following recent theoretical results, it is suggested that positronium (Ps)
might undergo spontaneous oscillations between two 4D spacetime sheets whenever
subjected to constant irrotational magnetic vector potentials. We show that
these oscillations that would come together with o-Ps/p-Ps oscillations should
have important consequences on Ps decay rates. Experimental setup and
conditions are also suggested for demonstrating in non accelerator experiments
this new invisible decay mode.Comment: 9 pages, 2 figures. Minor form correction. Accepted for publication
in Int. J. of Modern Physics
Matter localization and resonant deconfinement in a two-sheeted spacetime
In recent papers, a model of a two-sheeted spacetime M4XZ2 was introduced and
the quantum dynamics of massive fermions was studied in this framework. In the
present study, we show that the physical predictions of the model are perfectly
consistent with observations and most important, it can solve the puzzling
problem of the four-dimensional localization of the fermion species in
multidimensional spacetimes. It is demonstrated that fermion localization on
the sheets arises from the combination of the discrete bulk structure and
environmental interactions. The mechanism described in this paper can be seen
as an alternative to the domain wall localization arising in continuous five
dimensional spacetimes. Although tightly constrained, motions between the
sheets are, however, not completely prohibited. As an illustration, a resonant
mechanism through which fermion oscillations between the sheets might occur is
described.Comment: 9 pages, 1 figure. Published version. Accepted for publication in
Int. J. of Modern Physics
Balanced mechanical resonator for powder handling device
A system incorporating a balanced mechanical resonator and a method for vibration of a sample composed of granular material to generate motion of a powder sample inside the sample holder for obtaining improved analysis statistics, without imparting vibration to the sample holder support
Optical properties of tungsten thin films perforated with a bidimensional array of subwavelength holes
We present a theorical investigation of the optical transmission of a
dielectric grating carved in a tungsten layer. For appropriate wavelengths
tungsten shows indeed a dielectric behaviour. Our numerical simulations leads
to theoretical results similar to those found with metallic systems studied in
earlier works. The interpretation of our results rests on the idea that the
transmission is correlated with the resonant response of eigenmodes coupled to
evanescent diffraction orders.Comment: 4 pages, 3 figure
Brane matter, hidden or mirror matter, their various avatars and mixings: many faces of the same physics
Numerous papers deal with the phenomenology related to photon-hidden photon
kinetic mixing and with the effects of a mass mixing on particle-hidden
particle oscillations. In addition, recent papers underline the existence of a
geometrical mixing between branes which would allow a matter swapping between
branes. These approaches and their phenomenologies are reminiscent of each
other but rely on different physical concepts. In the present paper, we suggest
there is no rivalry between these models, which are probably many faces of the
same physics. We discuss some phenomenological consequences of a global
framework.Comment: 9 pages. Typo corrected. Published in European Physical Journal
Geometry of phase separation
We study the domain geometry during spinodal decomposition of a 50:50 binary
mixture in two dimensions. Extending arguments developed to treat non-conserved
coarsening, we obtain approximate analytic results for the distribution of
domain areas and perimeters during the dynamics. The main approximation is to
regard the interfaces separating domains as moving independently. While this is
true in the non-conserved case, it is not in the conserved one. Our results can
therefore be considered as a first-order approximation for the distributions.
In contrast to the celebrated Lifshitz-Slyozov-Wagner distribution of
structures of the minority phase in the limit of very small concentration, the
distribution of domain areas in the 50:50 case does not have a cut-off. Large
structures (areas or perimeters) retain the morphology of a percolative or
critical initial condition, for quenches from high temperatures or the critical
point respectively. The corresponding distributions are described by a tail, where and are exactly known. With increasing time,
small structures tend to have a spherical shape with a smooth surface before
evaporating by diffusion. In this regime the number density of domains with
area scales as , as in the Lifshitz-Slyozov-Wagner theory. The
threshold between the small and large regimes is determined by the
characteristic area, . Finally, we study the
relation between perimeters and areas and the distribution of boundary lengths,
finding results that are consistent with the ones summarized above. We test our
predictions with Monte Carlo simulations of the 2d Ising Model.Comment: 10 pages, 8 figure
Deep sea spy: a collaborative annotation tool
Since 2010, remote hydrothermal ecosystems are continuously being monitored using video cameras deployed on instrumented platforms. The acquisition of high-frequency video data from deep-sea observatories like EMSOAzores or Ocean Networks Canada provide information on species behaviour, feeding habits, growth, reproduction and organisms’ response to changes in environmental conditions. Video cameras acquire hourly data representing thousands of hours and Tera Bytes of footage but their manual processing is time-consuming and highly labour-intensive, and cannot be comprehensively undertaken by individual researchers. In order to help preliminary manual assessment of this huge imagery archive, a free online annotation tool was developed to gather contributions from a wider community. The Deep Sea Spy system offers a fun and engaging web interface to members of the public to help perform initial footage annotations. The platform now hosts 623 active annotators who contributed 179,663 annotations to 19,541 images. Preliminary analyses highlight a high variability among participants but show promising results to detect trends in species abundance variation over time. Ultimately, the information gathered via this approach can help improving the algorithms necessary to produce accurate automated detection in imagery using a machine learning approach
Exciton swapping in a twisted graphene bilayer as a solid-state realization of a two-brane model
It is shown that exciton swapping between two graphene sheets may occur under
specific conditions. A magnetically tunable optical filter is described to
demonstrate this new effect. Mathematically, it is shown that two turbostratic
graphene layers can be described as a "noncommutative" two-sheeted
(2+1)-spacetime thanks to a formalism previously introduced for the study of
braneworlds in high energy physics. The Hamiltonian of the model contains a
coupling term connecting the two layers which is similar to the coupling
existing between two braneworlds at a quantum level. In the present case, this
term is related to a K-K' intervalley coupling. In addition, the experimental
observation of this effect could be a way to assess the relevance of some
theoretical concepts of the braneworld hypothesis.Comment: 15 pages, 3 figures, final version published in European Physical
Journal
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