26,344 research outputs found
A New Key Agreement Scheme Based on the Triple Decomposition Problem
Abstract A new key agreement scheme based on the triple decomposition problem over non-commutative platforms is presented. A realization of the new scheme over braid groups is provided and the strengths of it over earlier systems that rely on similar decomposition problems are discussed. The new scheme improves over the earlier systems over braid groups by countering the linear algebra and length based attacks to the decomposition problem in braid groups
Coupling atomistic and continuum hydrodynamics through a mesoscopic model: application to liquid water
We have conducted a triple-scale simulation of liquid water by concurrently
coupling atomistic, mesoscopic, and continuum models of the liquid. The
presented triple-scale hydrodynamic solver for molecular liquids enables the
insertion of large molecules into the atomistic domain through a mesoscopic
region. We show that the triple-scale scheme is robust against the details of
the mesoscopic model owing to the conservation of linear momentum by the
adaptive resolution forces. Our multiscale approach is designed for molecular
simulations of open domains with relatively large molecules, either in the
grand canonical ensemble or under non-equilibrium conditions.Comment: triple-scale simulation, molecular dynamics, continuum, wate
Scattering AMplitudes from Unitarity-based Reduction Algorithm at the Integrand-level
SAMURAI is a tool for the automated numerical evaluation of one-loop
corrections to any scattering amplitudes within the dimensional-regularization
scheme. It is based on the decomposition of the integrand according to the
OPP-approach, extended to accommodate an implementation of the generalized
d-dimensional unitarity-cuts technique, and uses a polynomial interpolation
exploiting the Discrete Fourier Transform. SAMURAI can process integrands
written either as numerator of Feynman diagrams or as product of tree-level
amplitudes. We discuss some applications, among which the 6- and 8-photon
scattering in QED, and the 6-quark scattering in QCD. SAMURAI has been
implemented as a Fortran90 library, publicly available, and it could be a
useful module for the systematic evaluation of the virtual corrections oriented
towards automating next-to-leading order calculations relevant for the LHC
phenomenology.Comment: 35 pages, 7 figure
A Thermal Plume Model for the Martian Convective Boundary Layer
The Martian Planetary Boundary Layer [PBL] is a crucial component of the
Martian climate system. Global Climate Models [GCMs] and Mesoscale Models [MMs]
lack the resolution to predict PBL mixing which is therefore parameterized.
Here we propose to adapt the "thermal plume" model, recently developed for
Earth climate modeling, to Martian GCMs, MMs, and single-column models. The aim
of this physically-based parameterization is to represent the effect of
organized turbulent structures (updrafts and downdrafts) on the daytime PBL
transport, as it is resolved in Large-Eddy Simulations [LESs]. We find that the
terrestrial thermal plume model needs to be modified to satisfyingly account
for deep turbulent plumes found in the Martian convective PBL. Our Martian
thermal plume model qualitatively and quantitatively reproduces the thermal
structure of the daytime PBL on Mars: superadiabatic near-surface layer, mixing
layer, and overshoot region at PBL top. This model is coupled to surface layer
parameterizations taking into account stability and turbulent gustiness to
calculate surface-atmosphere fluxes. Those new parameterizations for the
surface and mixed layers are validated against near-surface lander
measurements. Using a thermal plume model moreover enables a first order
estimation of key turbulent quantities (e.g. PBL height, convective plume
velocity) in Martian GCMs and MMs without having to run costly LESs.Comment: 53 pages, 21 figures, paper + appendix. Accepted for publication in
Journal of Geophysical Research - Planet
Different Methods for the Two-Nucleon T-Matrix in the Operator Form
We compare three methods to calculate the nucleon-nucleon t-matrix based on
the three-dimensional formulation of J. Golak et al., Phys. Rev. C 81, 034006,
(2010). In the first place we solve a system of complex linear inhomogeneous
equations directly for the t-matrix. Our second method is based on iterations
and a variant of the Lanczos algorithm. In the third case we obtain the
t-matrix in two steps, solving a system of real linear equations for the
k-matrix expansion coefficients and then solving an on-shell equation, which
connects the scalar coefficients of the k- and t-matrices. A very good
agreement among the three methods is demonstrated for selected nucleon-nucleon
scattering observables using a chiral next-to-next-to-leading-order
neutron-proton potential. We also apply our three-dimensional framework to the
demanding problem of proton-proton scattering, using a corresponding version of
the nucleon-nucleon potential and supplementing it with the (screened) Coulomb
force, taken also in the three-dimensional form. We show converged results for
two different screening functions and find a very good agreement with other
methods dealing with proton-proton scattering.Comment: 18 pages, 10 figures (54 eps files
Off-shell two loop QCD vertices
We calculate the triple gluon, ghost-gluon and quark-gluon vertex functions
at two loops in the MSbar scheme in the chiral limit for an arbitrary linear
covariant gauge when the external legs are all off-shell.Comment: 29 latex pages, 32 figures, anc directory contains txt file with
electronic version of vertex functions for each of the three 3-point cases in
the MSbar scheme and includes the projection matrice
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