1,853 research outputs found
An elementary optical gate for expanding entanglement web
We introduce an elementary optical gate for expanding polarization entangled
W states, in which every pair of photons are entangled alike. The gate is
composed of a pair of 50:50 beamsplitters and ancillary photons in the
two-photon Fock state. By seeding one of the photons in an -photon W state
into this gate, we obtain an -photon W state after post-selection. This
gate gives a better efficiency and a simpler implementation than previous
proposals for -state preparation.Comment: 5 pages, 2 figures. To appear in Phys. Rev.
Demonstration of local expansion toward large-scale entangled webs
We demonstrate an optical gate that increases the size of polarization-based
W states by accessing only one of the qubits. Using this gate, we have
generated three-photon and four-photon W states with fidelities and , respectively. We also confirmed existence of pairwise
entanglement in every pair of the qubits including the one that was left
untouched by the gate. The gate is applicable to any size of W states and hence
is a universal tool for expanding entanglement.Comment: 5 pages, 4 figure
Double inflation in supergravity and the primordial black hole formation
We study a double inflation model (a hybrid inflation + a new inflation) in
supergravity and discuss the formation of primordial black holes (PBHs) with
mass \sim 10^{-20}-10^{5}M_{\odot}. We find that in a wide range of parameter
space, we obtain PBHs which amount to \Omega \simeq 1, i.e., PBH dark matter.
Also, we find a set of inflation parameters which produces PBHs evaporating
now. Those PBHs may be responsible for antiproton fluxes observed by the BESS
experiment.Comment: 14 pages, 2 figures (RevTeX file
Empirical Abundance Scaling Laws and Implications for the Gamma-Process in Core-Collapse Supernovae
Analyzing the solar system abundances, we have found two empirical abundance
scaling laws concerning the p- and s-nuclei with the same atomic number. The
first scaling is s/p ratios are almost constant over a wide range of the atomic
number, where the p-nculei are lighter than the s-nuclei by two or four
neutrons. The second scaling is p/p ratios are almost constant, where the
second -nuclei are lighter than the first p-nucleus by two neutrons. These
scalings are a piece of evidence that most p-nuclei are dominantly synthesized
by the gamma-process in supernova explosions. The scalings lead to a novel
concept of "universality of gamma-process" that the s/p and p/p ratios of
nuclei produced by individual gamma-processes are almost constant,
respectively. We have calculated the ratios by gamma-process based on
core-collapse supernova explosion models under various astrophysical conditions
and found that the scalings hold for materials produced by individual
gamma-processes independent of the astrophysical conditions assumed. The
universality originates from three mechanisms: the shifts of the gamma-process
layers to keep their peak temperature, the weak s-process in pre-supernovae,
and the independence of the s/p ratios of the nuclear reactions. The results
further suggest an extended universality that the s/p ratios in the
gamma-process layers are not only constant but also centered on a specific
value of 3. With this specific value and the first scaling, we estimate that
the ratios of -process abundance contributions from the AGB stars to the
massive stars are almost 6.7 for the -nuclei of A > 90. We find that large
enhancements of s/p ratios for Ce, Er, and W are a piece of evidence that the
weak s-process actually occurred before SNe.Comment: 35 pages, 15 figure
Transitions among crystal, glass, and liquid in a binary mixture with changing particle size ratio and temperature
Using molecular dynamics simulation we examine changeovers among crystal,
glass, and liquid at high density in a two dimensional binary mixture. We
change the ratio between the diameters of the two components and the
temperature. The transitions from crystal to glass or liquid occur with
proliferation of defects. We visualize the defects in terms of a disorder
variable "D_j(t)" representing a deviation from the hexagonal order for
particle j. The defect structures are heterogeneous and are particularly
extended in polycrystal states. They look similar at the crystal-glass
crossover and at the melting. Taking the average of "D_j(t)" over the
particles, we define a disorder parameter "D(t)", which conveniently measures
the degree of overall disorder. Its relaxation after quenching becomes slow at
low temperature in the presence of size dispersity. Its steady state average is
small in crystal and large in glass and liquid.Comment: 7 pages, 10 figure
âSidewalkâ as a Realm of Usersâ Interactions: simulating pedestriansâ densities at a commercial street in Cairo City
During the last four decades, researchers have developed many tools in order to investigate pedestriansâ behavior at sidewalks. Those tools tried to study sidewalks by investigating two main components: built environment and pedestriansâ movement. This paper presents a simulation for the pedestriansâ movement at a commercial street in Cairo, using an agent-based model. The model was designed in a way by which we could examine: pedestriansâ densities, the influence of types of uses on densities, the influence of flow-generators and destinations. In addition, we categorized the uses along the selected case of study by type of service and time spent by customer.
The method which we utilized for this work could be divided into two main phases: The first phase, included site video-based survey at different times and days, by which we could calculate flow rates at each generator point, and test the influence of uses on the density along the sidewalk. The second phase was to develop the model. In parallel, we focused on the usesâ types and how it affects controls pedestriansâ densities. Our results referred to a strong relation between useâs type and densitiesâ distribution along the street
An inertial range length scale in structure functions
It is shown using experimental and numerical data that within the traditional
inertial subrange defined by where the third order structure function is linear
that the higher order structure function scaling exponents for longitudinal and
transverse structure functions converge only over larger scales, , where
has scaling intermediate between and as a function of
. Below these scales, scaling exponents cannot be determined for any
of the structure functions without resorting to procedures such as extended
self-similarity (ESS). With ESS, different longitudinal and transverse higher
order exponents are obtained that are consistent with earlier results. The
relationship of these statistics to derivative and pressure statistics, to
turbulent structures and to length scales is discussed.Comment: 25 pages, 9 figure
Isocurvature Fluctuations of the M-theory Axion in a Hybrid Inflation Model
The M-theory, the strong-coupling heterotic string theory, presents various
interesting new phenomenologies. The M-theory bulk axion is one of these. The
decay constant in this context is estimated as GeV. Direct
searches for the M-theory axion seem impossible because of the large decay
constant. However, we point out that large isocurvature fluctuations of the
M-theory axion are obtained in a hybrid inflation model, which will most likely
be detectable in future satellite experiments on anisotropies of cosmic
microwave background radiation.Comment: 14 pages (RevTeX file), the final version to appear in Prog. Theor.
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