2,231 research outputs found
Techniques for QCD calculations by numerical integration
Calculations of observables in quantum chromodynamics are typically performed
using a method that combines numerical integrations over the momenta of final
state particles with analytical integrations over the momenta of virtual
particles. I describe the most important steps of a method for performing all
of the integrations numerically.Comment: 36 pages with 16 postscript figure
Numerical integration of one-loop Feynman diagrams for N-photon amplitudes
In the calculation of cross sections for infrared-safe observables in high
energy collisions at next-to-leading order, one approach is to perform all of
the integrations, including the virtual loop integration numerically. One would
use a subtraction scheme that removes infrared and collinear divergences from
the integrand in a style similar to that used for real emission graphs. Then
one would perform the loop integration by Monte Carlo integration along with
the integrations over final state momenta. In this paper, we have explored how
one can perform the numerical integration. We have studied the N-photon
scattering amplitude with a massless electron loop in order to have a case with
a singular integrand that is not, however, so singular as to require the
subtractions. We report results for N = 4, N = 5 with left-handed couplings,
and N=6.Comment: 30 pages including 5 figures. This is a revised version that is close
to the published versio
An Experimental Investigation of the Structural Properties of High Modulus Aluminium Alloy
The purpose of this report is to give the results of
an experimental investigation of the structural properties of
high modulus aluminium alloy.
The tests carried out consisted of tension,
compression, hardness, bending and compression panel
investigations.
It was found that high modulus material is difficult
to form and very prone to cracking on failure.
Thus although the material has a definite structural
application, in view of the forming and cracking problems it is
doubtful whether further development is worthwhile
Modeling the Dynamics of Compromised Networks
Accurate predictive models of compromised networks would contribute greatly to improving the effectiveness and efficiency of the detection and control of network attacks. Compartmental epidemiological models have been applied to modeling attack vectors such as viruses and worms. We extend the application of these models to capture a wider class of dynamics applicable to cyber security. By making basic assumptions regarding network topology we use multi-group epidemiological models and reaction rate kinetics to model the stochastic evolution of a compromised network. The Gillespie Algorithm is used to run simulations under a worst case scenario in which the intruder follows the basic connection rates of network traffic as a method of obfuscation
On the relationship between instability and Lyapunov times for the 3-body problem
In this study we consider the relationship between the survival time and the
Lyapunov time for 3-body systems. It is shown that the Sitnikov problem
exhibits a two-part power law relationship as demonstrated previously for the
general 3-body problem. Using an approximate Poincare map on an appropriate
surface of section, we delineate escape regions in a domain of initial
conditions and use these regions to analytically obtain a new functional
relationship between the Lyapunov time and the survival time for the 3-body
problem. The marginal probability distributions of the Lyapunov and survival
times are discussed and we show that the probability density function of
Lyapunov times for the Sitnikov problem is similar to that for the general
3-body problem.Comment: 9 pages, 19 figures, accepted for publication in MNRA
Partons and Jets at the LHC
I review some issues related to short distance QCD and its relation to the
experimental program of the Large Hadron Collider (LHC) now under construction
in Geneva.Comment: Talk at the conference QCD2002 at IIT Kanpur, India, November 2002.
Ten pages with 12 figure
Identifying Relevant Socio-Theoretic Foundations for Supporting Multi-Issue IT Cloudsourcing Negotiations
Service level agreement (SLA) negotiations involving cloud-based information technology (IT) service providers and customers are now commonplace. Although historical research on negotiation has often relied on economic foundations, the important nature of IT service levels to organizations’ operational effectiveness suggests that negotiation complexities in the context of cloud-based outsourcing (or cloudsourcing) cannot be well understood by relying on economic perspectives alone. To that end, this paper reports on experiments designed to determine the relevance of competing sociotheoretic frameworks as they pertain to IT cloudsourcing negotiations. Contributions include a rigorous examination of hypotheses derived from social exchange theory, equity theory, learning theory, and the win–win theories of negotiation. Additional contributions include the development of methodological constructs (using the Euclidean geometry) that reflect the complex nature of IT cloudsourcing SLAs, i.e., that they are composed of numerous service category contract clauses where negotiation tradeoffs within a service category as well as across service categories are possible. We find strong support for the relevance of the social exchange theory to IT cloudsourcing negotiations, as well as moderate support for the win-win theories of negotiation. Our conclusions provide clear directions for extending our work into the realm of negotiation support systems, and we rely on our findings to conjecture that IT cloudsourcing negotiation is a unique context for sociotheoretic negotiation research due to the inherent importance of information technologies to organizations’ operational effectiveness
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