272 research outputs found
Full one-loop amplitudes from tree amplitudes
We establish an efficient polynomial-complexity algorithm for one-loop
calculations, based on generalized -dimensional unitarity. It allows
automated computations of both cut-constructible {\it and} rational parts of
one-loop scattering amplitudes from on-shell tree amplitudes. We illustrate the
method by (re)-computing all four-, five- and six-gluon scattering amplitudes
in QCD at one-loop.Comment: 27 pages, revte
Profiling Occupant Behaviour in Danish Dwellings using Time Use Survey Data - Part I: Data Description and Activity Profiling
The human interaction with the building is a key cause of uncertainty when predicting energy consump- tion of buildings. Building occupants affect building energy use directly and indirectly by interacting with building energy systems, for example, by adjusting thermostats, switching lights on/off, using electri- cal devices and opening/closing windows. The occupants’ daily activity profiles and occupancy patterns clearly shape the timing and magnitude of energy demand in households. Modelling energy-related hu- man activities throughout the day, therefore, is a crucial task for prediction of energy use and, conse- quently, to reduce the gap between real and predicted building energy use. This study modelled data gathered in the diary-based Danish Time Use Survey (TUS) 2008/09 of 9640 individuals from 4679 households. Individuals’ daily activities were logged in 10-min time increments for 24 h, starting and ending at 04:00, during both weekdays and weekends. The aims of this study were to (i) profile energy-related daily activities of occupants during different seasons and weekdays/weekends (ii) investigate time-related characteristics of activities such as starting and ending times and durations, and (iii) profile occupancy patterns for weekdays/weekends for different household types. The outcomes provide valuable input for building energy simulation for bridging the gap between simulated and real energy consumption in the Danish residential sector; typical occupancy profiles for different household types for different days of the week are freely available online[1]
CutTools: a program implementing the OPP reduction method to compute one-loop amplitudes
We present a program that implements the OPP reduction method to extract the
coefficients of the one-loop scalar integrals from a user defined
(sub)-amplitude or Feynman Diagram, as well as the rational terms coming from
the 4-dimensional part of the numerator. The rational pieces coming from the
epsilon-dimensional part of the numerator are treated as an external input, and
can be computed with the help of dedicated tree-level like Feynman rules.
Possible numerical instabilities are dealt with the help of arbitrary
precision routines, that activate only when needed.Comment: Version published in JHE
Applications of the Collective Field Theory for the Calogero-Sutherland Model
We use the collective field theory known for the Calogero-Sutherland model to
study a variety of low-energy properties. These include the ground state energy
in a confining potential upto the two leading orders in the particle number,
the dispersion relation of sound modes with a comparison to the two leading
terms in the low temperature specific heat, large amplitude waves, and single
soliton solutions. The two-point correlation function derived from the
dispersion relation of the sound mode only gives its nonoscillatory asymptotic
behavior correctly, demonstrating that the theory is applicable only for the
low-energy and long wavelength excitations of the system.Comment: LaTeX, 31 page
Jet angular correlation in vector-boson fusion processes at hadron colliders
Higgs boson and massive-graviton productions in association with two jets via
vector-boson fusion (VBF) processes and their decays into a vector-boson pair
at hadron colliders are studied. They include scalar and tensor boson
production processes via weak-boson fusion in quark-quark collisions, gluon
fusion in quark-quark, quark-gluon and gluon-gluon collisions, as well as their
decays into a pair of weak bosons or virtual gluons which subsequently decay
into , or . We give the helicity amplitudes
explicitly for all the VBF subprocesses, and show that the VBF amplitudes
dominate the exact matrix elements not only for the weak-boson fusion processes
but also for all the gluon fusion processes when appropriate selection cuts are
applied, such as a large rapidity separation between two jets and a slicing cut
for the transverse momenta of the jets. We also show that our off-shell
vector-boson current amplitudes reduce to the standard quark and gluon
splitting amplitudes with appropriate gluon-polarization phases in the
collinear limit. Nontrivial azimuthal angle correlations of the jets in the
production and in the decay of massive spin-0 and -2 bosons are manifestly
expressed as the quantum interference among different helicity states of the
intermediate vector-bosons. Those correlations reflect the spin and the CP
nature of the Higgs bosons and the massive gravitons.Comment: 47 pages, 7 figures, 10 tables; references added, version to appear
in JHE
Anticipatory freight selection in intermodal long-haul round-trips
We consider the planning problem faced by Logistic Service Providers (LSPs) transporting freights periodically, using long-haul round-trips. In each round-trip, freights are delivered and picked up at different locations within one region. Freights have time-windows and become known gradually over time. Using probabilistic knowledge about future freights, the LSP’s objective is to minimize costs over a multi-period horizon. We propose a look-ahead planning method using Approximate Dynamic Programming. Experiments show that our approach reduces costs up to 25.5% compared to a single-period optimization approach. We provide managerial insights for several intermodal long-haul round-trips settings and provide directions for further research
The effects of grain shape and frustration in a granular column near jamming
We investigate the full phase diagram of a column of grains near jamming, as
a function of varying levels of frustration. Frustration is modelled by the
effect of two opposing fields on a grain, due respectively to grains above and
below it. The resulting four dynamical regimes (ballistic, logarithmic,
activated and glassy) are characterised by means of the jamming time of
zero-temperature dynamics, and of the statistics of attractors reached by the
latter. Shape effects are most pronounced in the cases of strong and weak
frustration, and essentially disappear around a mean-field point.Comment: 17 pages, 19 figure
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