90,563 research outputs found
Gravitational Lensing and Anisotropies of CBR on the Small Angular Scales
We investigate the effect of gravitational lensing, produced by linear
density perturbations, for anisotropies of the Cosmic Background Radiation
(CBR) on scales of arcminutes. In calculations, a flat universe ()
and the Harrison-Zel'dovich spectrum () are assumed. The numerical results
show that on scales of a few arcminutes, gravitational lensing produces only
negligible anisotropies in the temperature of the CBR. Our conclusion disagrees
with that of Cay\'{o}n {\it et al.} who argue that the amplification of on scales may even be larger than 100\%.Comment: Accepted by MNRAS. 16 pages, 2 figures, tarred, compressed and
uuencoded Postscript file
Limit Cycle Bifurcations from Centers of Symmetric Hamiltonian Systems Perturbing by Cubic Polynomials
In this paper, we consider some cubic near-Hamiltonian systems obtained from
perturbing the symmetric cubic Hamiltonian system with two symmetric singular
points by cubic polynomials. First, following Han [2012] we develop a method to
study the analytical property of the Melnikov function near the origin for
near-Hamiltonian system having the origin as its elementary center or nilpotent
center. Based on the method, a computationally efficient algorithm is
established to systematically compute the coefficients of Melnikov function.
Then, we consider the symmetric singular points and present the conditions for
one of them to be elementary center or nilpotent center. Under the condition
for the singular point to be a center, we obtain the normal form of the
Hamiltonian systems near the center. Moreover, perturbing the symmetric cubic
Hamiltonian systems by cubic polynomials, we consider limit cycles bifurcating
from the center using the algorithm to compute the coefficients of Melnikov
function. Finally, perturbing the symmetric hamiltonian system by symmetric
cubic polynomials, we consider the number of limit cycles near one of the
symmetric centers of the symmetric near-Hamiltonian system, which is same to
that of another center
A Simultaneous Quantum Secure Direct Communication Scheme between the Central Party and Other M Parties
We propose a simultaneous quantum secure direct communication scheme between
one party and other three parties via four-particle GHZ states and swapping
quantum entanglement. In the scheme, three spatially separated senders, Alice,
Bob and Charlie, transmit their secret messages to a remote receiver Diana by
performing a series local operations on their respective particles according to
the quadripartite stipulation. From Alice, Bob, Charlie and Diana's Bell
measurement results, Diana can infer the secret messages. If a perfect quantum
channel is used, the secret messages are faithfully transmitted from Alice, Bob
and Charlie to Diana via initially shared pairs of four-particle GHZ states
without revealing any information to a potential eavesdropper. As there is no
transmission of the qubits carrying the secret message in the public channel,
it is completely secure for the direct secret communication. This scheme can be
considered as a network of communication parties where each party wants to
communicate secretly with a central party or server.Comment: 4 pages, no figur
Probabilistic teleportation of unknown two-particle state via POVM
We propose a scheme for probabilistic teleportation of unknown two-particle
state with partly entangled four-particle state via POVM. In this scheme the
teleportation of unknown two-particle state can be realized with certain
probability by performing two Bell state measurements, a proper POVM and a
unitary transformation.Comment: 5 pages, no figur
Angular Momentum Projected Configuration Interaction with Realistic Hamiltonians
The Projected Configuration Interaction (PCI) method starts from a collection
of mean-field wave functions, and builds up correlated wave functions of good
symmetry. It relies on the Generator Coordinator Method (GCM) techniques, but
it improves the past approaches by a very efficient method of selecting the
basis states. We use the same realistic Hamiltonians and model spaces as the
Configuration Interaction (CI) method, and compare the results with the full CI
calculations in the sd and pf shell. Examples of 24Mg, 28Si, 48Cr, 52Fe and
56Ni are discussed.Comment: 10 pages, 10 figures. Revised version. To be published in Physical
Review
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