440 research outputs found
Doubling of background solution in 5D stabilized brane world model
We discuss a model providing two different stationary background solutions
with flat and metric on the branes under the same values of the
fundamental parameters. It is shown that only an additional fine-tuning of the
brane scalar field potentials can provide a separation between two background
solutions.Comment: 7 pages, LaTeX, typos correcte
MHV Lagrangian for N=4 Super Yang-Mills
Here we formulate two field redefinitions for N=4 Super Yang-Mills in light
cone superspace that generates only MHV vertices in the new Lagrangian. After
careful consideration of the S-matrix equivalence theorem, we see that only the
canonical transformation gives the MHV Lagrangian that would correspond to the
CSW expansion. Being in superspace, it is easier to analyse the equivalence
theorem at loop level. We calculate the on shell amplitude for 4pt
MHV in the new lagrangian and
show that it reproduces the previously known form. We also briefly discuss the
relationship with the off-shell continuation prescription of CSW.Comment: 17 pages 4 figures, 2 sections and several references added typo
correcte
Amplitudes in Pure Yang-Mills and MHV Diagrams
We show how to calculate the one-loop scattering amplitude with all gluons of
negative helicity in non-supersymmetric Yang-Mills theory using MHV diagrams.
We argue that the amplitude with all positive helicity gluons arises from a
Jacobian which occurs when one performs a Backlund-type holomorphic change of
variables in the lightcone Yang-Mills Lagrangian. This also results in
contributions to scattering amplitudes from violations of the equivalence
theorem. Furthermore, we discuss how the one-loop amplitudes with a single
positive or negative helicity gluon arise in this formalism. Perturbation
theory in the new variables leads to a hybrid of MHV diagrams and lightcone
Yang-Mills theory.Comment: 31 pages, 4 figures. v2: references added, JHEP versio
Form Factors in N=4 Super Yang-Mills and Periodic Wilson Loops
We calculate form factors of half-BPS operators in N=4 super Yang-Mills
theory at tree level and one loop using novel applications of recursion
relations and unitarity. In particular, we determine the expression of the
one-loop form factors with two scalars and an arbitrary number of
positive-helicity gluons. These quantities resemble closely the MHV scattering
amplitudes, including holomorphicity of the tree-level form factor, and the
expansion in terms of two-mass easy box functions of the one-loop result. Next,
we compare our result for these form factors to the calculation of a particular
periodic Wilson loop at one loop, finding agreement. This suggests a novel
duality relating form factors to periodic Wilson loops.Comment: 26 pages, 10 figures. v2: typos fixed, comments adde
General Metrics of G_2 Holonomy and Contraction Limits
We obtain first-order equations for G_2 holonomy of a wide class of metrics
with S^3\times S^3 principal orbits and SU(2)\times SU(2) isometry, using a
method recently introduced by Hitchin. The new construction extends previous
results, and encompasses all previously-obtained first-order systems for such
metrics. We also study various group contractions of the principal orbits,
focusing on cases where one of the S^3 factors is subjected to an Abelian,
Heisenberg or Euclidean-group contraction. In the Abelian contraction, we
recover some recently-constructed G_2 metrics with S^3\times T^3 principal
orbits. We obtain explicit solutions of these contracted equations in cases
where there is an additional U(1) isometry. We also demonstrate that the only
solutions of the full system with S^3\times T^3 principal orbits that are
complete and non-singular are either flat R^4 times T^3, or else the direct
product of Eguchi-Hanson and T^3, which is asymptotic to R^4/Z_2\times T^3.
These examples are in accord with a general discussion of isometric fibrations
by tori which, as we show, in general split off as direct products. We also
give some (incomplete) examples of fibrations of G_2 manifolds by associative
3-tori with either T^4 or K3 as base.Comment: Latex, 27 page
Generalizing the N=2 supersymmetric RG flow solution of IIB supergravity
We explicitly construct the supersymmetry transformations for the N=2
supersymmetric RG flow solution of chiral IIB supergravity. We show that the
metric, dilaton/axion, five-index tensor and half of the three index tensor are
determined algebraically in terms of the Killing spinor of the unbroken
supersymmetry. The algebraic nature of the solution allows us to generalize
this construction to a new class of N=2 supersymmetric solutions of IIB
supergravity. Each solution in this class is algebraically determined by
supersymmetry and is parametrized by a single function of two variables that
satisfies a non-linear equation akin to the Laplace equation on the space
transverse to the brane.Comment: 27 pages; harvmac; tex twic
Generalized Konishi anomaly, Seiberg duality and singular effective superpotentials
Using the generalized Konishi anomaly (GKA) equations, we derive the
effective superpotential of four-dimensional N=1 supersymmetric SU(n) gauge
theory with n+2 fundamental flavors. We find, however, that the GKA equations
are only integrable in the Seiberg dual description of the theory, but not in
the direct description of the theory. The failure of integrability in the
direct, strongly coupled, description suggests the existence of
non-perturbative corrections to the GKA equations.Comment: 20 pages; v3: corrected the comparison to the SU(2) cas
Spinor Helicity and Dual Conformal Symmetry in Ten Dimensions
The spinor helicity formalism in four dimensions has become a very useful
tool both for understanding the structure of amplitudes and also for practical
numerical computation of amplitudes. Recently, there has been some discussion
of an extension of this formalism to higher dimensions. We describe a
particular implementation of the spinor-helicity method in ten dimensions.
Using this tool, we study the tree-level S-matrix of ten dimensional super
Yang-Mills theory, and prove that the theory enjoys a dual conformal symmetry.
Implications for four-dimensional computations are discussed.Comment: 24 pages, 1 figure
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