1,145 research outputs found
Kondo physics in tunable semiconductor nanowire quantum dots
We have observed the Kondo effect in strongly coupled semiconducting nanowire
quantum dots. The devices are made from indium arsenide nanowires, grown by
molecular beam epitaxy, and contacted by titanium leads. The device
transparency can be tuned by changing the potential on a gate electrode, and
for increasing transparencies the effects dominating the transport changes from
Coulomb Blockade to Universal Conductance Fluctuations with Kondo physics
appearing in the intermediate region.Comment: 4 pages, 4 figure
Manifesting Color-Kinematics Duality in the Scattering Equation Formalism
We prove that the scattering equation formalism for Yang-Mills amplitudes can
be used to make manifest the theory's color-kinematics duality. This is
achieved through a concrete reduction algorithm which renders this duality
manifest term-by-term. The reduction follows from the recently derived set of
identities for amplitudes expressed in the scattering equation formalism that
are analogous to monodromy relations in string theory. A byproduct of our
algorithm is a generalization of the identities among gravity and Yang-Mills
amplitudes.Comment: 20 pages, 20 figure
Analytic Representations of Yang-Mills Amplitudes
Scattering amplitudes in Yang-Mills theory can be represented in the
formalism of Cachazo, He and Yuan (CHY) as integrals over an auxiliary
projective space---fully localized on the support of the scattering equations.
Because solving the scattering equations is difficult and summing over the
solutions algebraically complex, a method of directly integrating the terms
that appear in this representation has long been sought. We solve this
important open problem by first rewriting the terms in a manifestly
Mobius-invariant form and then using monodromy relations (inspired by analogy
to string theory) to decompose terms into those for which combinatorial rules
of integration are known. The result is a systematic procedure to obtain
analytic, covariant forms of Yang-Mills tree-amplitudes for any number of
external legs and in any number of dimensions. As examples, we provide compact
analytic expressions for amplitudes involving up to six gluons of arbitrary
helicities.Comment: 29 pages, 43 figures; also included is a Mathematica notebook with
explicit formulae. v2: citations added, and several (important) typos fixe
Scattering Equations and Feynman Diagrams
We show a direct matching between individual Feynman diagrams and integration
measures in the scattering equation formalism of Cachazo, He and Yuan. The
connection is most easily explained in terms of triangular graphs associated
with planar Feynman diagrams in -theory. We also discuss the
generalization to general scalar field theories with interactions,
corresponding to polygonal graphs involving vertices of order . Finally, we
describe how the same graph-theoretic language can be used to provide the
precise link between individual Feynman diagrams and string theory integrands.Comment: 18 pages, 57 figure
Integration Rules for Loop Scattering Equations
We formulate new integration rules for one-loop scattering equations
analogous to those at tree-level, and test them in a number of non-trivial
cases for amplitudes in scalar -theory. This formalism greatly
facilitates the evaluation of amplitudes in the CHY representation at one-loop
order, without the need to explicitly sum over the solutions to the loop-level
scattering equations.Comment: 22 pages, 17 figure
Integration Rules for Scattering Equations
As described by Cachazo, He and Yuan, scattering amplitudes in many quantum
field theories can be represented as integrals that are fully localized on
solutions to the so-called scattering equations. Because the number of
solutions to the scattering equations grows quite rapidly, the contour of
integration involves contributions from many isolated components. In this
paper, we provide a simple, combinatorial rule that immediately provides the
result of integration against the scattering equation constraints for any
M\"obius-invariant integrand involving only simple poles. These rules have a
simple diagrammatic interpretation that makes the evaluation of any such
integrand immediate. Finally, we explain how these rules are related to the
computation of amplitudes in the field theory limit of string theory.Comment: 30 pages, 29 figure
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