9,294 research outputs found
The Structure of Multiloop Amplitudes in Gauge and Gravity Theories
We review the recently discovered duality between color and kinematics in
gauge theories. This duality leads to a remarkably simple double-copy relation
between diagrammatic numerators of gravity scattering amplitudes and
gauge-theory ones. We summarize nontrivial evidence that the duality and
double-copy property holds to all loop orders. We also comment on other
developments, including a proof that the gauge-theory duality leads to the
gravity double-copy property, and the identification of gauge-theory
Lagrangians whose double copies yield gravity Lagrangians.Comment: To appear in Proceedings of Loops and Legs in Quantum Field Theory,
Woerlitz, Germany, April 25-30, 2010; 4 figure
The rational parts of one-loop QCD amplitudes II: The five-gluon case
The rational parts of 5-gluon one-loop amplitudes are computed by using the
newly developed method for computing the rational parts directly from Feynman
integrals. We found complete agreement with the previously well-known results
of Bern, Dixon and Kosower obtained by using the string theory method.
Intermediate results for some combinations of Feynman diagrams are presented in
order to show the efficiency of the method and the local cancellation between
different contributions.Comment: 25 pages, 16 figures and LaTeX file; minor corrections, references
added, to be published in Nucl. Phys.
Recursive Approach to One-loop QCD Matrix Elements
We describe the recursive Approach to One-loop QCD Matrix Elements.Comment: 6 pages, to appear in the proceedings of the 7th International
Symposium on Radiative Corrections: Application of Quantum Field Theory to
Phenomenology (RADCOR 2005), Japan, 2-7 Oct 200
Ultra-Violet Infinities and Counterterms in Higher Dimensional Yang-Mills
In this letter we investigate the ultra-violet behaviour of four-point
one-loop gluon amplitudes in dimensions greater than four coupled to various
particles types. We discuss the structure of the counterterms and their
inherent symmetries.Comment: 14 pages, LateX, axodra
Is N = 8 Supergravity Ultraviolet Finite?
Conventional wisdom holds that no four-dimensional gravity field theory can
be ultraviolet finite. This understanding is based mainly on power counting.
Recent studies confirm that one-loop N = 8 supergravity amplitudes satisfy the
so-called `no-triangle hypothesis', which states that triangle and bubble
integrals cancel from these amplitudes. A consequence of this hypothesis is
that for any number of external legs, at one loop N = 8 supergravity and N = 4
super-Yang-Mills have identical superficial degrees of ultraviolet behavior in
D dimensions. We describe how the unitarity method allows us to promote these
one-loop cancellations to higher loops, suggesting that previous power counts
were too conservative. We discuss higher-loop evidence suggesting that N = 8
supergravity has the same degree of divergence as N = 4 super-Yang-Mills theory
and is ultraviolet finite in four dimensions. We comment on calculations needed
to reinforce this proposal, which are feasible using the unitarity method.Comment: 7 pages, 5 figures, revte
The Infrared Behavior of One-Loop Gluon Amplitudes at Next-to-Next-to-Leading Order
For the case of -jet production at next-to-next-to-leading order in the
QCD coupling, in the infrared divergent corners of phase space where particles
are collinear or soft, one must evaluate -parton final-state one-loop
amplitudes through \Ord(\eps^2), where \eps is the dimensional
regularization parameter. For the case of gluons, we present to all orders in
\eps the required universal functions which describe the behavior of one-loop
amplitudes in the soft and collinear regions of phase space. An explicit
example is discussed for three-parton production in multi-Regge kinematics that
has applications to the next-to-leading logarithmic corrections to the BFKL
equation.Comment: Latex, 14 pages, no figure
Calculation of 1-loop Hexagon Amplitudes in the Yukawa Model
We calculate a class of one-loop six-point amplitudes in the Yukawa model.
The construction of multi-particle amplitudes is done in the string inspired
formalism and compared to the Feynman diagrammatic approach. We show that there
exists a surprisingly efficient way of calculating such amplitudes by using
cyclic identities of kinematic coefficients and discuss in detail cancellation
mechanisms of spurious terms. A collection of formulas which are useful for the
calculation of massless hexagon amplitudes is given.Comment: 15 pages Late
On Perturbative Gravity and Gauge Theory
We review some applications of tree-level (classical) relations between
gravity and gauge theory that follow from string theory. Together with
-dimensional unitarity, these relations can be used to perturbatively
quantize gravity theories, i.e. they contain the necessary information for
obtaining loop contributions. We also review recent applications of these ideas
showing that N=1 D=11 supergravity diverges, and review arguments that N=8 D=4
supergravity is less divergent than previously thought, though it does appear
to diverge at five loops. Finally, we describe field variables for the
Einstein-Hilbert Lagrangian that help clarify the perturbative relationship
between gravity and gauge theory.Comment: Talk presented at Third Meeting on Constrained Dynamics and Quantum
Gravity, Villasimius (Sardinia, Italy) September 13-17, 1999 and at the
Workshop on Light-Cone QCD and Nonperturbative Hadron Physics, University of
Adelaide (Australia) December 13-22, 1999. Latex, 9 page
Exploiting Twistor Techniques for One-loop QCD Amplitudes
In this talk we describe the recursive Approach to One-loop QCD Matrix
Elements.Comment: Talk presented by David C. Dunbar at Loop and Legs 2006, 5 page
Unitarity Cuts: NLO Six-Gluon Amplitudes in QCD
We report on a technique for evaluating finite unitarity cut for one-loop
amplitudes in gauge theories, and discuss its application to the
cut-constructible part of six-gluon amplitude in QCD.Comment: talk given at Loops & Legs 2006, April 23-28, Eisenach (Germany
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