86,678 research outputs found
A fast high-order method to calculate wakefield forces in an electron beam
In this paper we report on a high-order fast method to numerically calculate
wakefield forces in an electron beam given a wake function model. This method
is based on a Newton-Cotes quadrature rule for integral approximation and an
FFT method for discrete summation that results in an computational
cost, where is the number of grid points. Using the Simpson quadrature rule
with an accuracy of , where is the grid size, we present numerical
calculation of the wakefields from a resonator wake function model and from a
one-dimensional coherent synchrotron radiation (CSR) wake model. Besides the
fast speed and high numerical accuracy, the calculation using the direct line
density instead of the first derivative of the line density avoids numerical
filtering of the electron density function for computing the CSR wakefield
force
Fermion Families from Two Layer Warped Extra Dimensions
In extra dimensions, the quark and lepton mass hierarchy can be reproduced
from the same order bulk mass parameters, and standard model fermion families
can be generated from one generation in the high dimensional space. We try to
explain the origin of the same order bulk mass parameters and address the
family replication puzzle simultaneously. We show that they correlate with each
other. We construct models that families are generated from extra dimensional
space, and in the meantime the bulk mass parameters of same order emerge
naturally. The interesting point is that the bulk mass parameters, which are in
same order, correspond to the eigenvalues of a Schr\"{o}dinger-like equation.
We also discuss the problem existing in this approach.Comment: 21 latex pages, final version to appear in JHE
Entanglement in a second order topological insulator on a square lattice
In a -dimensional topological insulator of order , there are zero
energy states on its corners which have close relationship with its
entanglement behaviors. We studied the bipartite entanglement spectra for
different subsystem shapes and found that only when the entanglement boundary
has corners matching the lattice, exact zero modes exist in the entanglement
spectrum corresponding to the zero energy states caused by the same physical
corners. We then considered finite size systems in which case these corner
states are coupled together by long range hybridizations to form a multipartite
entangled state. We proposed a scheme to calculate the quadripartite
entanglement entropy on the square lattice, which is well described by a
four-sites toy model and thus provides another way to identify the higher order
topological insulators from the multipartite entanglement point of view.Comment: 5 pages, 3 figure
Kolmogorov's law of the iterated logarithm for noncommutative martingales
We prove Kolmogorov's law of the iterated logarithm for noncommutative
martingales. The commutative case was due to Stout. The key ingredient is an
exponential inequality proved recently by Junge and the author.Comment: Revise
Revisit the Concept of PEKS: Problems and a Possible Solution
Since Boneh et al. propose the concept, non-interactive\ud
Public-key Encryption with Keyword Search (PEKS) has attracted lots of attention from cryptographers. Non-interactive PEKS enables a third party to test whether or not a tag, generated by the message sender, and a trapdoor, generated by the receiver, contain the same keyword without revealing further information. In this paper we investigate a non-interactive PEKS application proposed by Boneh et al. and show our observations, especially that privacy is\ud
not protected against a curious server. We propose the notion of interactive PEKS, which, in contrast to non-interactive PEKS, requires the tag to be generated interactively by the message sender and the receiver. For this new primitive, we identify two types of adversaries, namely a curious user and a curious server, and provide\ud
security formulations for the desirable properties. We propose a construction for interactive PEKS and prove its security in the proposed security model
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