8,191 research outputs found
Case of Almost Redundant Components in 3 alpha Faddeev Equations
The 3 alpha orthogonality condition model using the Pauli-forbidden bound
states of the Buck, Friedlich and Wheatly alpha alpha potential can yield a
compact 3 alpha ground state with a large binding energy, in which a small
admixture of the redundant components can never be eliminated.Comment: Revtex V4.0, 4 pages, no figure
Comparison between the Cramer-Rao and the mini-max approaches in quantum channel estimation
In a unified viewpoint in quantum channel estimation, we compare the
Cramer-Rao and the mini-max approaches, which gives the Bayesian bound in the
group covariant model. For this purpose, we introduce the local asymptotic
mini-max bound, whose maximum is shown to be equal to the asymptotic limit of
the mini-max bound. It is shown that the local asymptotic mini-max bound is
strictly larger than the Cramer-Rao bound in the phase estimation case while
the both bounds coincide when the minimum mean square error decreases with the
order O(1/n). We also derive a sufficient condition for that the minimum mean
square error decreases with the order O(1/n).Comment: In this revision, some unlcear parts are clarifie
Gauge Equivalence in Two--Dimensional Gravity
Two-dimensional quantum gravity is identified as a second-class system which
we convert into a first-class system via the Batalin-Fradkin (BF) procedure.
Using the extended phase space method, we then formulate the theory in most
general class of gauges. The conformal gauge action suggested by David, Distler
and Kawai is derived from a first principle. We find a local, light-cone gauge
action whose Becchi-Rouet-Stora-Tyutin invariance implies Polyakov's curvature
equation , revealing the origin of the
Kac-Moody symmetry. The BF degree of freedom turns out be dynamically
active as the Liouville mode in the conformal gauge, while in the light-cone
gauge the conformal degree of freedom plays that r{\^o}le. The inclusion of the
cosmological constant term in both gauges and the harmonic gauge-fixing are
also considered.Comment: 30 pages, KANAZAWA 93-
A Realistic Description of Nucleon-Nucleon and Hyperon-Nucleon Interactions in the SU_6 Quark Model
We upgrade a SU_6 quark-model description for the nucleon-nucleon and
hyperon-nucleon interactions by improving the effective meson-exchange
potentials acting between quarks. For the scalar- and vector-meson exchanges,
the momentum-dependent higher-order term is incorporated to reduce the
attractive effect of the central interaction at higher energies. The
single-particle potentials of the nucleon and Lambda, predicted by the G-matrix
calculation, now have proper repulsive behavior in the momentum region q_1=5 -
20 fm^-1. A moderate contribution of the spin-orbit interaction from the
scalar-meson exchange is also included. As to the vector mesons, a dominant
contribution is the quadratic spin-orbit force generated from the rho-meson
exchange. The nucleon-nucleon phase shifts at the non-relativistic energies up
to T_lab=350 MeV are greatly improved especially for the 3E states. The
low-energy observables of the nucleon-nucleon and the hyperon-nucleon
interactions are also reexamined. The isospin symmetry breaking and the Coulomb
effect are properly incorporated in the particle basis. The essential feature
of the Lambda N - Sigma N coupling is qualitatively similar to that obtained
from the previous models. The nuclear saturation properties and the
single-particle potentials of the nucleon, Lambda and Sigma are reexamined
through the G-matrix calculation. The single-particle potential of the Sigma
hyperon is weakly repulsive in symmetric nuclear matter. The single-particle
spin-orbit strength for the Lambda particle is very small, in comparison with
that of the nucleons, due to the strong antisymmetric spin-orbit force
generated from the Fermi-Breit interaction.Comment: Revtex v2.09, 69 pages with 25 figure
Spiky density of states in large complex Al-Mn phases
First-principle electronic structure calculations have been performed in
crystalline complex phases mu-Al4Mn and lambda-Al4Mn using the TB-LMTO method.
These atomic structures, related to quasicrystalline structures, contain about
560 atoms in a large hexagonal unit cell. One of the main characteristic of
their density of states is the presence of fine peaks the so-called "spiky
structure". From multiple-scattering calculations in real space, we show that
these fine peaks are not artifacts in ab-initio calculations, since they result
from a specific localization of electrons by atomic clusters of different
length scales
Magnetic properties of Fe/Dy multilayers: a Monte Carlo investigation
We investigate the magnetic properties of a Heisenberg ferrimagnetic
multilayer by using Monte Carlo simulations. The aim of this work is to study
the local structural anisotropy model which is a possible origin of the
perpendicular magnetic anisotropy in transition metal/rare earth amorphous
multilayers. We have considered a face centered cubic lattice where each site
is occupied by a classical Heisenberg spin. We have introduced in our model of
amorphous multilayers a small fraction of crystallized Fe-Dy nanoclusters with
a mean anisotropy axis along the deposition direction. We show that a
competition in the energy terms takes place between the mean uniaxial
anisotropy of the Dy atoms in the nanoclusters and the random anisotropy of the
Dy atoms in the matrix.Comment: accepte pour publication - Proceeding of the Joint European Magnetic
Symposia (JEMS 06) - Journal of Magnetism and Magnetic Material
Analysis of a convenient information bound for general quantum channels
Open questions from Sarovar and Milburn (2006 J.Phys. A: Math. Gen. 39 8487)
are answered. Sarovar and Milburn derived a convenient upper bound for the
Fisher information of a one-parameter quantum channel. They showed that for
quasi-classical models their bound is achievable and they gave a necessary and
sufficient condition for positive operator-valued measures (POVMs) attaining
this bound. They asked (i) whether their bound is attainable more generally,
(ii) whether explicit expressions for optimal POVMs can be derived from the
attainability condition. We show that the symmetric logarithmic derivative
(SLD) quantum information is less than or equal to the SM bound, i.e.\
and we find conditions for equality. As
the Fisher information is less than or equal to the SLD quantum information,
i.e. , we can deduce when equality holds in
. Equality does not hold for all
channels. As a consequence, the attainability condition cannot be used to test
for optimal POVMs for all channels. These results are extended to
multi-parameter channels.Comment: 16 pages. Published version. Some of the lemmas have been corrected.
New resuts have been added. Proofs are more rigorou
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