14,175 research outputs found
Identification of the age-period-cohort model and the extended chain ladder model
In this paper, we consider the identification problem arising in the age-period-cohort models, as well as in the extended chain ladder model. We propose a canonical parametrization based on the accelerations of the trends in the three factors. This parametrization is exactly identified. It eases interpretation, estimation and forecasting. The canonical parametrization is shown to apply for a class of index sets which have trapezoid shapes, including various Lexis diagrams and the insurance reserving triangles.
Semi-analytic calculation of the monopole order parameter in QCD
The monopole order parameter of QCD is computed in terms of gauge invariant
field strength correlators. Both quantities are partially known from numerical
simulations on the lattice. A new insight results on the structure of the
confining vacuum.Comment: Talk presented at QCD06, Montpellier 3-7 July 2006. To appear in the
proceeding
Robust Unconditionally Secure Quantum Key Distribution with Two Nonorthogonal and Uninformative States
We introduce a novel form of decoy-state technique to make the single-photon
Bennett 1992 protocol robust against losses and noise of a communication
channel. Two uninformative states are prepared by the transmitter in order to
prevent the unambiguous state discrimination attack and improve the phase-error
rate estimation. The presented method does not require strong reference pulses,
additional electronics or extra detectors for its implementation.Comment: 7 pages, 2 figure
Entanglement evolution in a cascaded system with losses
The dynamics of a cascaded system that consists of two atom-cavity subsystems
is studied by using the quantum trajectory method. Unwanted losses are
included, such as photon absorption and scattering by the cavity mirrors and
spontaneous emission of the atoms. Considering an initially excited two-level
atom in the source subsystem, analytical solutions are obtained. The
entanglement evolution is studied for the two atoms and for the two intracavity
fields.Comment: 6 pages, 4 figure
Optimal path for a quantum teleportation protocol in entangled networks
Bellman's optimality principle has been of enormous importance in the
development of whole branches of applied mathematics, computer science, optimal
control theory, economics, decision making, and classical physics. Examples are
numerous: dynamic programming, Markov chains, stochastic dynamics, calculus of
variations, and the brachistochrone problem. Here we show that Bellman's
optimality principle is violated in a teleportation problem on a quantum
network. This implies that finding the optimal fidelity route for teleporting a
quantum state between two distant nodes on a quantum network with bi-partite
entanglement will be a tough problem and will require further investigation.Comment: 4 pages, 1 figure, RevTeX
Monopole condensation in the ground state of gauge theories: a disorder parameter
We construct a disorder parameter for dual superconductivity of the ground
state of gauge theory.Comment: 3 pages, contribution to the Lattice '94 conference, shell archive
containing uuencoded LATEX file + 2 figure
A single photon produces general W state of N qubits and its application
Based on the Wu's scheme[1], We prepare the general N-qubit W state. We find
that the concurrence of two qubits in general N-qubit W state is only related
to their coefficients and we successfully apply the general N-qubit W state to
quantum state transfer and quantum state prepare like that in two-qubit system
Concentration profiles for fine and coarse sediments suspended by waves over ripples: An analytical study with the 1-DV gradient diffusion model
Field and laboratory measurements of suspended sediments over wave ripples
show, for time-averaged concentration profiles in semi-log plots, a contrast
between upward convex profiles for fine sand and upward concave profiles for
coarse sand. Careful examination of experimental data for coarse sand shows a
near-bed upward convex profile beneath the main upward concave profile.
Available models fail to predict these two profiles for coarse sediments. The
1-DV gradient diffusion model predicts the main upward concave profile for
coarse sediments thanks to a suitable (y)-function (where is the
inverse of the turbulent Schmidt number and y is the distance from the bed). In
order to predict the near-bed upward convex profile, an additional parameter
{\alpha} is needed. This parameter could be related to settling velocity
( equal to inverse of dimensionless settling velocity) or to convective
sediment entrainment process. The profiles are interpreted by a relation
between second derivative of the logarithm of concentration and derivative of
the product between sediment diffusivity and
Rosen-Zener Transition in a Nonlinear Two-Level System
We study Rosen-Zener transition (RZT) in a nonlinear two-level system in
which the level energies depend on the occupation of the levels, representing a
mean-field type of interaction between the particles. We find that the
nonlinearity could affect the quantum transition dramatically. At certain
nonlinearity the 100% population transfer between two levels is observed and
found to be robust over a very wide range of external parameters. On the other
hand, the quantum transition could be completely blocked by a strong
nonlinearity. In the sudden and adiabatic limits we have derived analytical
expressions for the transition probability. Numerical explorations are made for
a wide range of parameters of the general case. Possible applications of our
theory to Bose-Einstern Condensates (BECs) are discussed.Comment: 8 pages, 8 figure
A Possible Universal Treatment of the Field Strength Correlator in the Abelian-Projected SU(2)-Theory
An integral relation between two functions parametrizing the bilocal field
strength correlator within the Stochastic Vacuum Model is obtained in the
effective Abelian-projected SU(2)-theory. This relation is independent of the
concrete properties of the ensemble of vortex loops, which are present in the
theory under study. By virtue of the lattice result stating that the infrared
asymptotic behaviours of these functions should have the same functional form,
the obtained relation enables one to find these behaviours, as well as the
infrared asymptotics of the bilocal correlator of densities of the vortex
loops. Those turn out to be exponentials, decreasing at the inverse mass of the
dual vector boson, times certain polynomials in the inverse integer powers of
the distance. This result agrees with the general predictions and the existing
lattice data better than the results of previous calculations, where these
powers were found to be half-integer ones.Comment: 9 pages, LaTeX2e, no figures, new discussions of the obtained results
are added, to appear in Phys. Lett.
- âŠ