23,243 research outputs found
Comment on "Secure direct communication with a quantum one-time pad"
In the paper [Phys. Rev. A \textbf{69}, 052319 (2004)], a quantum direct
communication protocol is proposed which is claimed to be unconditionally
secure even for the case of a noisy channel. We show that this is not the case
by giving an undetectable attack scheme
The state space of short-range Ising spin glasses: the density of states
The state space of finite square and cubic Ising spin glass models is
analysed in terms of the global and the local density of states. Systems with
uniform and gaussian probability distribution of interactions are compared.
Different measures for the local state density are presented and discussed. In
particular the question whether the local density of states grows exponentially
or not is considered. The direct comparison of global and local densities leads
to consequences for the structure of the state space.Comment: 18 pages (including 6 figures); submitted to Z.f.Physik
Existence of Weak Solutions for the Unsteady Interaction of a Viscous Fluid with an Elastic Plate
International audienceWe consider a three--dimensional viscous incompressible fluid governed by the Navier--Stokes equations, interacting with an elastic plate located on one part of the fluid boundary. We do not neglect the deformation of the fluid domain which consequently depends on the displacement of the structure. The purpose of this work is to study the solutions of this unsteady fluid--structure interaction problem, as the coefficient modeling the viscoelasticity (resp. the rotatory inertia) of the plate tends to zero. As a consequence, we obtain the existence of at least one weak solution for the limit problem (Navier--Stokes equation coupled with a plate in flexion) as long as the structure does not touch the bottom of the fluid cavity
A new doubly discrete analogue of smoke ring flow and the real time simulation of fluid flow
Modelling incompressible ideal fluids as a finite collection of vortex
filaments is important in physics (super-fluidity, models for the onset of
turbulence) as well as for numerical algorithms used in computer graphics for
the real time simulation of smoke. Here we introduce a time-discrete evolution
equation for arbitrary closed polygons in 3-space that is a discretisation of
the localised induction approximation of filament motion. This discretisation
shares with its continuum limit the property that it is a completely integrable
system. We apply this polygon evolution to a significant improvement of the
numerical algorithms used in Computer Graphics.Comment: 15 pages, 3 figure
Einstein-Born-Infeld on Taub-NUT Spacetime in 2k+2 Dimensions
We wish to construct solutions of Taub-NUT spacetime in Einstein-Born-Infeld
gravity in even dimensions. Since Born-Infeld theory is a nonlinear
electrodynamics theory, in leads to nonlinear differential equations. However a
proper analytical solution was not obtain, we try to solve it numerically (by
the Runge-Kotta method) with initial conditions coinciding with those of our
previous work in Einstein-Maxwell gravity. We solve equations for 4, 6 and 8
dimensions and do data fitting by the least-squares method. For N=l=b=1, the
metric turns to the NUT solution only in 8 dimensions, but in 4 and 6
dimensions the spacetime does not have any Nut solution.Comment: 8 pages, 5 figure
Family of Hermitian Low-Momentum Nucleon Interactions with Phase Shift Equivalence
Using a Schmidt orthogonalization transformation, a family of Hermitian
low-momentum NN interactions is derived from the non-Hermitian Lee-Suzuki (LS)
low-momentum NN interaction. As special cases, our transformation reproduces
the Hermitian interactions for Okubo and Andreozzi. Aside from their common
preservation of the deuteron binding energy, these Hermitian interactions are
shown to be phase shift equivalent, all preserving the empirical phase shifts
up to decimation scale Lambda. Employing a solvable matrix model, the Hermitian
interactions given by different orthogonalization transformations are studied;
the interactions can be very different from each other particularly when there
is a strong intruder state influence. However, because the parent LS
low-momentum NN interaction is only slightly non-Hermitian, the Hermitian
low-momentum nucleon interactions given by our transformations, including the
Okubo and Andreozzi ones, are all rather similar to each other. Shell model
matrix elements given by the LS and several Hermitian low-momentum interactions
are compared.Comment: 10 pages, 7 figure
Toward inertial confinement fusion energy based on heavy ion beam
Heavy ion inertial fusion (HIF) energy would be one of promising energy
resources securing our future energy in order to sustain our human life for
centuries and beyond. The heavy ion beam (HIB) has remarkable preferable
features to release the fusion energy in inertial confinement fusion: in
particle accelerators HIBs are generated with a high driver efficiency of ~
30-40%, and the HIB ions deposit their energy inside of materials. Therefore, a
requirement for the fusion target energy gain is relatively low, that would be
~50-70 to operate a HIF fusion reactor with the standard energy output of 1GW
of electricity. The HIF reactor operation frequency would be ~10~15 Hz or so.
Several-MJ HIBs illuminate a fusion fuel target, and the fuel target is
imploded to about a thousand times of the solid density. Then the DT fuel is
ignited and burned. The HIB ion deposition range would be ~0.5-1 mm or so
depending on the material. Therefore, a relatively large density-scale length
appears in the fuel target material. The large density-gradient-scale length
helps to reduce the Rayleigh-Taylor (R-T) growth rate. The key merits in HIF
physics are presented in the article toward our bright future energy resource.Comment: 17 pages. arXiv admin note: substantial text overlap with
arXiv:1511.06508, arXiv:1608.0106
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