3,055,952 research outputs found
Six-Point One-Loop N=8 Supergravity NMHV Amplitudes and their IR behaviour
We present compact formulas for the box coefficients of the six-point NMHV
one-loop amplitudes in N=8 supergravity. We explicitly demonstrate that the
corresponding box integral functions, with these coefficients, have the
complete IR singularities expected of the one-loop amplitude. This is strong
evidence for the conjecture that N=8 one-loop amplitudes may be expressed in
terms of scalar box integral functions. This structure, although unexpected
from a power counting viewpoint, is analogous to the structure of N=4
super-Yang-Mills amplitudes. The box-coefficients match the tree amplitude
terms arising from recursion relations.Comment: 14 pages; Minor typographic errors correcte
Inherited Twistor-Space Structure of Gravity Loop Amplitudes
At tree-level, gravity amplitudes are obtainable directly from gauge theory
amplitudes via the Kawai, Lewellen and Tye closed-open string relations. We
explain how the unitarity method allows us to use these relations to obtain
coefficients of box integrals appearing in one-loop N=8 supergravity amplitudes
from the recent computation of the coefficients for N=4 super-Yang-Mills
non-maximally-helicity-violating amplitudes. We argue from factorisation that
these box coefficients determine the one-loop N=8 supergravity amplitudes,
although this remains to be proven. We also show that twistor-space properties
of the N=8 supergravity amplitudes are inherited from the corresponding
properties of N=4 super-Yang-Mills theory. We give a number of examples
illustrating these ideas.Comment: 32 pages, minor typos correcte
Dynamics underlying Box-office: Movie Competition on Recommender Systems
We introduce a simple model to study movie competition in the recommender
systems. Movies of heterogeneous quality compete against each other through
viewers' reviews and generate interesting dynamics of box-office. By assuming
mean-field interactions between the competing movies, we show that run-away
effect of popularity spreading is triggered by defeating the average review
score, leading to hits in box-office. The average review score thus
characterizes the critical movie quality necessary for transition from
box-office bombs to blockbusters. The major factors affecting the critical
review score are examined. By iterating the mean-field dynamical equations, we
obtain qualitative agreements with simulations and real systems in the
dynamical forms of box-office, revealing the significant role of competition in
understanding box-office dynamics.Comment: 8 pages, 6 figure
Shapes of Semiflexible Polymers in Confined Spaces
We investigate the conformations of a semiflexible polymer confined to a
square box. Results of Monte Carlo simulations show the existence of a shape
transition when the persistence length of the polymer becomes comparable to the
dimensions of box. An order parameter is introduced to quantify this behavior.
A simple mean-field model is constructed to study the effect of the shape
transition on the effective persistence length of the polymer.Comment: 8 pages, 20 figure
Evaluating double and triple (?) boxes
A brief review of recent results on analytical evaluation of double-box
Feynman integrals is presented. First steps towards evaluation of massless
on-shell triple-box Feynman integrals within dimensional regularization are
described. The leading power asymptotic behaviour of the dimensionally
regularized massless on-shell master planar triple-box diagram in the Regge
limit is evaluated. The evaluation of the unexpanded master planar
triple box is outlined and explicit results for coefficients at 1/\ep^j,
j=2,...,6, are presented.Comment: 6 pages, LaTeX with axodraw.sty; Talk presented at the International
Symposium Radcor 2002 and Loops and Legs 2002 (September 8--13, Kloster Banz,
Germany); to appear in Nuclear Physics B (Proc. Suppl.); a wrong abstract is
replace
The No-Triangle Hypothesis for N=8 Supergravity
We study the perturbative expansion of N=8 supergravity in four dimensions
from the viewpoint of the ``no-triangle'' hypothesis, which states that
one-loop graviton amplitudes in N=8 supergravity only contain scalar box
integral functions. Our computations constitute a direct proof at six-points
and support the no-triangle conjecture for seven-point amplitudes and beyond.Comment: 43page
Parity nonconserving two-pion exchange in elastic proton-proton scattering
Parity nonconserving two-pion exchange in elastic pp scattering is
investigated in the presence of phenomenological strong distortions in various
models. Parity violation is included in the nucleon-pion vertex considering NN
and N Delta(1232) intermediate states in box and crossed box diagrams. Using
the derived parity nonconserving two-pion exchange potential we calculate the
longitudinal analyzing power A_L in elastic scattering. The predicted
effect is of the same order as vector meson exchanges.Comment: 13 pages, 8 eps figure
Brane Boxes: Bending and Beta Functions
We study the type IIB brane box configurations recently introduced by Hanany
and Zaffaroni. We show that even at finite string coupling, one can construct
smooth configurations of branes with fairly arbitrary gauge and flavor
structure. Limiting our attention to the better understood case where NS-branes
do not intersect over a four dimensional surface gives some restrictions on the
theories, but still permits many examples, both anomalous and non-anomalous. We
give several explicit examples of such configurations and discuss what
constraints can be imposed on brane-box theories from bending considerations.
We also discuss the relation between brane bending and beta-functions for
brane-box configurations.Comment: latex, 18 pages, 8 figure
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