40,544 research outputs found
Realizing arbitrary-precision modular multiplication with a fixed-precision multiplier datapath
Within the context of cryptographic hardware, the term scalability refers to the ability to process operands of any size, regardless of the precision of the underlying data path or registers. In this paper we present a simple yet effective technique for increasing the scalability of a fixed-precision Montgomery multiplier. Our idea is to extend the datapath of a Montgomery multiplier in such a way that it can also perform an ordinary multiplication of two n-bit operands (without modular reduction), yielding a 2n-bit result. This
conventional (nxn->2n)-bit multiplication is then used as a “sub-routine” to realize arbitrary-precision Montgomery multiplication according to standard software algorithms such as Coarsely Integrated Operand Scanning (CIOS). We
show that performing a 2n-bit modular multiplication on an n-bit multiplier can be done in 5n clock cycles, whereby we assume that the n-bit modular multiplication takes n cycles. Extending a Montgomery multiplier for this extra
functionality requires just some minor modifications of the datapath and entails a slight increase in silicon area
Estimating spinning binary parameters and testing alternative theories of gravity with LISA
We investigate the effect of spin-orbit and spin-spin couplings on the
estimation of parameters for inspiralling compact binaries of massive black
holes, and for neutron stars inspiralling into intermediate-mass black holes,
using hypothetical data from the proposed Laser Interferometer Space Antenna
(LISA). We work both in Einstein's theory and in alternative theories of
gravity of the scalar-tensor and massive-graviton types. We restrict the
analysis to non-precessing spinning binaries, i.e. to cases where the spins are
aligned normal to the orbital plane. We find that the accuracy with which
intrinsic binary parameters such as chirp mass and reduced mass can be
estimated within general relativity is degraded by between one and two orders
of magnitude. We find that the bound on the coupling parameter omega_BD of
scalar-tensor gravity is significantly reduced by the presence of spin
couplings, while the reduction in the graviton-mass bound is milder. Using fast
Monte-Carlo simulations of 10^4 binaries, we show that inclusion of spin terms
in massive black-hole binaries has little effect on the angular resolution or
on distance determination accuracy. For stellar mass inspirals into
intermediate-mass black holes, the angular resolution and the distance are
determined only poorly, in all cases considered. We also show that, if LISA's
low-frequency noise sensitivity can be extrapolated from 10^-4 Hz to as low as
10^-5 Hz, the accuracy of determining both extrinsic parameters (distance, sky
location) and intrinsic parameters (chirp mass, reduced mass) of massive
binaries may be greatly improved.Comment: 29 pages, 9 figures. Matches version accepted in Physical Review D.
More stringent checks in the inversion of the Fisher matri
The basic parameters of gamma-ray-loud blazars
We determined the basic parameters, such as the central black hole mass
(), the boosting factor (or Doppler factor) (), the propagation
angle () and the distance along the axis to the site of -ray
production () for 23 -ray-loud blazars using their available
variability timescales. In this method, the absorption effect depends on the
-ray energy, emission size and property of the accretion disk. Using
the intrinsic -ray luminosity as a fraction of the Eddington
luminosity, and the optical depth equal to
unity, we can determine the upper limit of the central black hole masses. We
found that the black hole masses range between and
when = 0.1 and 1.0 are adopted. Since this method
is based on gamma-ray emissions and the short time-scale of the sources, it can
also be used for central black hole mass determination of high redshift
gamma-ray sources. In the case of the upper limit of black hole mass there is
no clear difference between BLs and FSRQs, which suggests that the central
black hole masses do not play an important role in the evolutionary sequence of
blazars.Comment: 8 pages, 3 figures, 1 table, Accepted by A&
A three-dimensional lattice gas model for amphiphilic fluid dynamics
We describe a three-dimensional hydrodynamic lattice-gas model of amphiphilic
fluids. This model of the non-equilibrium properties of oil-water-surfactant
systems, which is a non-trivial extension of an earlier two-dimensional
realisation due to Boghosian, Coveney and Emerton [Boghosian, Coveney, and
Emerton 1996, Proc. Roy. Soc. A 452, 1221-1250], can be studied effectively
only when it is implemented using high-performance computing and visualisation
techniques. We describe essential aspects of the model's theoretical basis and
computer implementation, and report on the phenomenological properties of the
model which confirm that it correctly captures binary oil-water and
surfactant-water behaviour, as well as the complex phase behaviour of ternary
amphiphilic fluids.Comment: 34 pages, 13 figures, high resolution figures available on reques
Long Range Correlation in Granular Shear Flow II: Theoretical Implications
Numerical simulations are used to test the kinetic theory constitutive
relations of inertial granular shear flow. These predictions are shown to be
accurate in the dilute regime, where only binary collisions are relevant, but
underestimate the measured value in the dense regime, where force networks of
size are present. The discrepancy in the dense regime is due to
non-collisional forces that we measure directly in our simulations and arise
from elastic deformations of the force networks. We model the non-collisional
stress by summing over all paths that elastic waves travel through force
networks. This results in an analytical theory that successfully predicts the
stress tensor over the entire inertial regime without any adjustable
parameters
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