116,159 research outputs found
Multifragmentation of non-spherical nuclei : Analysis of central Xe + Sn collisions at 50 MeV/nucl
The influence of shape of expanding and rotating source on various
characteristics of the multifragmentation process is studied. The analysis is
based on the extension of the statistical microcanonical multifragmentation
model. The comparison with the data is done for central Xe+Sn collisions at 50
A MeV as measured by INDRA Collaboration.Comment: 9 pages, 2 figures; Talk given at the XXVII International Workshop on
Gross Properties of Nuclei and Nuclear Excitation, Hirschegg (Austria),
January 17 - 23, 199
A mathematical formalization of the parallel replica dynamics
The purpose of this article is to lay the mathematical foundations of a well
known numerical approach in computational statistical physics and molecular
dynamics, namely the parallel replica dynamics introduced by A.F. Voter. The
aim of the approach is to efficiently generate a coarse-grained evolution (in
terms of state-to-state dynamics) of a given stochastic process. The approach
formally consists in concurrently considering several realizations of the
stochastic process, and tracking among the realizations that which, the
soonest, undergoes an important transition. Using specific properties of the
dynamics generated, a computational speed-up is obtained. In the best cases,
this speed-up approaches the number of realizations considered. By drawing
connections with the theory of Markov processes and, in particular, exploiting
the notion of quasi-stationary distribution, we provide a mathematical setting
appropriate for assessing theoretically the performance of the approach, and
possibly improving it
Discussion quality diffuses in the digital public square
Studies of online social influence have demonstrated that friends have
important effects on many types of behavior in a wide variety of settings.
However, we know much less about how influence works among relative strangers
in digital public squares, despite important conversations happening in such
spaces. We present the results of a study on large public Facebook pages where
we randomly used two different methods--most recent and social feedback--to
order comments on posts. We find that the social feedback condition results in
higher quality viewed comments and response comments. After measuring the
average quality of comments written by users before the study, we find that
social feedback has a positive effect on response quality for both low and high
quality commenters. We draw on a theoretical framework of social norms to
explain this empirical result. In order to examine the influence mechanism
further, we measure the similarity between comments viewed and written during
the study, finding that similarity increases for the highest quality
contributors under the social feedback condition. This suggests that, in
addition to norms, some individuals may respond with increased relevance to
high-quality comments.Comment: 10 pages, 6 figures, 2 table
Answering Mermin's Challenge with Conservation per No Preferred Reference Frame
In 1981, Mermin published a now famous paper titled, "Bringing home the
atomic world: Quantum mysteries for anybody" that Feynman called, "One of the
most beautiful papers in physics that I know." Therein, he presented the
"Mermin device" that illustrates the conundrum of quantum entanglement per the
Bell spin states for the "general reader." He then challenged the "physicist
reader" to explain the way the device works "in terms meaningful to a general
reader struggling with the dilemma raised by the device." Herein, we show how
"conservation per no preferred reference frame (NPRF)" answers that challenge.
In short, the explicit conservation that obtains for Alice and Bob's
Stern-Gerlach spin measurement outcomes in the same reference frame holds only
on average in different reference frames, not on a trial-by-trial basis. This
conservation is SO(3) invariant in the relevant symmetry plane in real space
per the SU(2) invariance of its corresponding Bell spin state in Hilbert space.
Since NPRF is also responsible for the postulates of special relativity, and
therefore its counterintuitive aspects of time dilation and length contraction,
we see that the symmetry group relating non-relativistic quantum mechanics and
special relativity via their "mysteries" is the restricted Lorentz group.Comment: 18 pages, 9 figures. This version as revised and resubmitted to
Scientific Report
Evolution of the gaps through the cuprate phase-diagram
The actual physical origin of the gap at the antinodes, and a clear
identification of the superconducting gap are fundamental open issues in the
physics of high- superconductors. Here, we present a systematic electronic
Raman scattering study of a mercury-based single layer cuprate, as a function
of both doping level and temperature. On the deeply overdoped side, we show
that the antinodal gap is a true superconducting gap. In contrast, on the
underdoped side, our results reveal the existence of a break point close to
optimal doping below which the antinodal gap is gradually disconnected from
superconductivity. The nature of both the superconducting and normal state is
distinctly different on each side of this breakpoint
Libration driven elliptical instability
The elliptical instability is a generic instability which takes place in any
rotating flow whose streamlines are elliptically deformed. Up to now, it has
been widely studied in the case of a constant, non-zero differential rotation
between the fluid and the elliptical distortion with applications in
turbulence, aeronautics, planetology and astrophysics. In this letter, we
extend previous analytical studies and report the first numerical and
experimental evidence that elliptical instability can also be driven by
libration, i.e. periodic oscillations of the differential rotation between the
fluid and the elliptical distortion, with a zero mean value. Our results
suggest that intermittent, space-filling turbulence due to this instability can
exist in the liquid cores and sub-surface oceans of so-called synchronized
planets and moons
Efficient light coupling from integrated single-mode waveguides to supercollimating photonic crystals on silicon-on-insulator platforms
We propose a practical and efficient solution for the coupling of light from
integrated single-mode waveguides to supercollimating planar photonic crystals
on conventional silicon-on-insulator platforms. The device consists of a rib
waveguide, designed to sustain spatially extended single-modes and matched to a
supercollimating photonic crystal, which has been truncated at its boundary to
improve impedance matching between the two photonic components.
Three-dimensional simulations show transmission efficiencies up to 96 % and
reflections below 0.2 % at wavelengths close to 1.55 microns. This approach
constitutes a significant step toward the integration of supercollimating
structures on photonic chips.Comment: 11 pages, 4 figure
The Wide-field High-resolution Infrared TElescope (WHITE)
The Wide-field High-resolution Infrared TElescope (WHITE) will be dedicated
in the first years of its life to carrying out a few (well focused in terms of
science objectives and time) legacy surveys.
WHITE would have an angular resolution of ~0.3'' homogeneous over ~0.7 sq.
deg. in the wavelength range 1 - 5 um, which means that we will very
efficiently use all the available observational time during night time and day
time. Moreover, the deepest observations will be performed by summing up
shorter individual frames. We will have a temporal information that can be used
to study variable objects.
The three key science objectives of WHITE are : 1) A complete survey of the
Magellanic Clouds to make a complete census of young stellar objects in the
clouds and in the bridge and to study their star formation history and the link
with the Milky Way. The interaction of the two clouds with our Galaxy might the
closest example of a minor merging event that could be the main driver of
galaxy evolution in the last 5 Gyrs. 2) The building of the first sample of
dusty supernovae at z<1.2 in the near infrared range (1-5 um) to constrain the
equation of state from these obscured objects, study the formation of dust in
galaxies and build the first high resolution sample of high redshift galaxies
observed in their optical frame 3) A very wide weak lensing survey over that
would allow to estimate the equation of state in a way that would favourably
compete with space projects.Comment: Invited talk to the 2nd ARENA Conference : "The Astrophysical Science
Cases at Dome C" Potsdam 17-21 September, 200
- …