4,044 research outputs found
A scattering theory of ultrarelativistic solitons
We construct a perturbative framework for understanding the collision of
solitons (more precisely, solitary waves) in relativistic scalar field
theories. Our perturbative framework is based on the suppression of the
space-time interaction area proportional to , where is the
relative velocity of an incoming solitary wave and . We calculate the leading order results for collisions of (1+1) dimensional
kinks in periodic potentials, and provide explicit, closed form expressions for
the phase shift and the velocity change after the collisions. We find excellent
agreement between our results and detailed numerical simulations. Crucially,
our perturbation series is controlled by a kinematic parameter, and hence not
restricted to small deviations around integrable cases such as the Sine-Gordon
model.Comment: v3: 43 pages, 10 figures, references added, matches version accepted
for publication in PR
Position-dependent-mass; Cylindrical coordinates, separability, exact solvability, and PT-symmetry
The kinetic energy operator with position-dependent-mass in cylindrical
coordinates is obtained. The separability of the corresponding Schr\"odinger
equation is discussed within radial cylindrical mass settings. Azimuthal
symmetry is assumed and spectral signatures of various z-dependent interaction
potentials (Hermitian and non-Hermitian PT-symmetric) are reported.Comment: 16 page
A secure data outsourcing scheme based on Asmuth – Bloom secret sharing
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Data outsourcing is an emerging paradigm for data management in which a database is provided as a service by third-party service providers. One of the major benefits of offering database as a service is to provide organisations, which are unable to purchase expensive hardware and software to host their databases, with efficient data storage accessible online at a cheap rate. Despite that, several issues of data confidentiality, integrity, availability and efficient indexing of users’ queries at the server side have to be addressed in the data outsourcing paradigm. Service providers have to guarantee that their clients’ data are secured against internal (insider) and external attacks. This paper briefly analyses the existing indexing schemes in data outsourcing and highlights their advantages and disadvantages. Then, this paper proposes a secure data outsourcing scheme based on Asmuth–Bloom secret sharing which tries to address the issues in data outsourcing such as data confidentiality, availability and order preservation for efficient indexing
Ultra-relativistic oscillon collisions
In this short note we investigate the ultra-relativistic collisions of small
amplitude oscillons in 1+1 dimensions. Using the amplitude of the oscillons and
the inverse relativistic boost factor as the perturbation
variables, we analytically calculate the leading order spatial and temporal
phase shifts, and the change in the amplitude of the oscillons after the
collisions. At leading order, we find that only the temporal phase shift
receives a nonzero contribution, and that the collision is elastic. This work
is also the first application of the general kinematic framework for
understanding ultra-relativistic collisions (arXiv:1308.0606) to intrinsically
time-dependent solitons.Comment: 12 pages, 3 figures, version 2, added one reference and matching the
version to appear on PR
Preparation and characterization of magnetite (Fe3O4) nanoparticles By Sol-Gel method
The magnetite (Fe3O4) nanoparticles were successfully synthesized and annealed under vacuum at different temperature. The Fe3O4 nanoparticles prepared via sol-gel assisted method and annealed at 200-400ºC were characterized by Fourier Transformation Infrared Spectroscopy (FTIR), X-ray Diffraction spectra (XRD), Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscopy (AFM). The XRD result indicate the presence of Fe3O4 nanoparticles, and the Scherer`s Formula calculated the mean particles size in range of 2-25 nm. The FESEM result shows that the morphologies of the particles annealed at 400ºC are more spherical and partially agglomerated, while the EDS result indicates the presence of Fe3O4 by showing Fe-O group of elements. AFM analyzed the 3D and roughness of the sample; the Fe3O4 nanoparticles have a minimum diameter of 79.04 nm, which is in agreement with FESEM result. In many cases, the synthesis of Fe3O4 nanoparticles using FeCl3 and FeCl2 has not been achieved, according to some literatures, but this research was able to obtained Fe3O4 nanoparticles base on the characterization results
Classical and quantum quasi-free position dependent mass; P\"oschl-Teller and ordering-ambiguity
We argue that the classical and quantum mechanical correspondence may play a
basic role in the fixation of the ordering-ambiguity parameters. We use
quasi-free position-dependent masses in the classical and quantum frameworks.
The effective P\"oschl-Teller model is used as a manifested reference potential
to elaborate on the reliability of the ordering-ambiguity parameters available
in the literature.Comment: 10 page
Identification and Ranking of Relevant Image Content
The work in this thesis proposes an image understanding algorithm for automatically identifying and ranking different image regions into several levels of importance. Given a color image, specialized maps for classifying image content namely: weighted similarity, weighted homogeneity, image contrast and memory color maps are generated and combined to provide a perceptual importance map. Further analysis of this map yields a region ranking map which sorts the image content into different levels of significance.
The algorithm was tested on a large database that contains a variety of color images. Those images were acquired from the Berkeley segmentation dataset as well as internal images. Experimental results show that our technique matches human manual ranking with 90% efficiency.
Applications of the proposed algorithm include image rendering, classification, indexing and retrieval. Adaptive compression and camera auto-focus are other potential applications
Flat-top oscillons in an expanding universe
Oscillons are extremely long lived, oscillatory, spatially localized field
configurations that arise from generic initial conditions in a large number of
non-linear field theories. With an eye towards their cosmological implications,
we investigate their properties in an expanding universe. We (1) provide an
analytic solution for one dimensional oscillons (for the models under
consideration) and discuss their generalization to 3 dimensions, (2) discuss
their stability against long wavelength perturbations and (3) estimate the
effects of expansion on their shapes and life-times. In particular, we discuss
a new, extended class of oscillons with surprisingly flat tops. We show that
these flat topped oscillons are more robust against collapse instabilities in
(3+1) dimensions than their usual counterparts. Unlike the solutions found in
the small amplitude analysis, the width of these configurations is a
non-monotonic function of their amplitudes.Comment: v2-matches version published in Phys. Rev D. Updated references and
minor modification to section 4.
Non-Hermitian von Roos Hamiltonian's -weak-pseudo-Hermiticity, isospectrality and exact solvability
A complexified von Roos Hamiltonian is considered and a Hermitian first-order
intertwining differential operator is used to obtain the related position
dependent mass -weak-pseudo-Hermitian Hamiltonians. Using a
Liouvillean-type change of variables, the -weak-pseudo-Hermitian von Roos
Hamiltonians H(x) are mapped into the traditional Schrodinger Hamiltonian form
H(q), where exact isospectral correspondence between H(x) and H(q) is obtained.
Under a user-friendly position dependent mass settings, it is observed that for
each exactly-solvable -weak-pseudo-Hermitian reference-Hamiltonian
H(q)there is a set of exactly-solvable -weak-pseudo-Hermitian isospectral
target-Hamiltonians H(x). A non-Hermitian PT-symmetric Scarf II and a
non-Hermitian periodic-type PT-symmetric Samsonov-Roy potentials are used as
reference models and the corresponding -weak-pseudo-Hermitian isospectral
target-Hamiltonians are obtained.Comment: 11 pages, no figures
The Energy Eigenvalues of the Two Dimensional Hydrogen Atom in a Magnetic Field
In this paper, the energy eigenvalues of the two dimensional hydrogen atom
are presented for the arbitrary Larmor frequencies by using the asymptotic
iteration method. We first show the energy eigenvalues for the no magnetic
field case analytically, and then we obtain the energy eigenvalues for the
strong and weak magnetic field cases within an iterative approach for
and states for several different arbitrary Larmor frequencies. The
effect of the magnetic field on the energy eigenvalues is determined precisely.
The results are in excellent agreement with the findings of the other methods
and our method works for the cases where the others fail.Comment: 13 pages and 5 table
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