116887100
Color-kinematics duality for pure Yang-Mills and gravity at one and two loops
We provide evidence in favor of the conjectured duality between color and kinematics for the case of nonsupersymmetric pure Yang-Mills amplitudes by constructing a form of the one-loop four-point amplitude of this theory that makes the duality manifest. Our construction is valid in any dimension. We also describe a duality-satisfying representation for the two-loop four-point amplitude with identical four-dimensional external helicities. We use these results to obtain corresponding gravity integrands for a theory containing a graviton, dilaton, and antisymmetric tensor, simply by replacing color factors with specified diagram numerators. Using this, we give explicit forms of ultraviolet divergences at one loop in four, six, and eight dimensions, and at two loops in four dimensions.
34930280
Equivalent D = 3 supergravity amplitudes from double copies of three-algebra and two-algebra gauge theories.
We show that three-dimensional supergravity amplitudes can be obtained as double copies of either three-algebra super-Chern-Simons matter theory or two-algebra super-Yang-Mills theory when either theory is organized to display the color-kinematics duality. We prove that only helicity-conserving four-dimensional gravity amplitudes have nonvanishing descendants when reduced to three dimensions, implying the vanishing of odd-multiplicity S-matrix elements, in agreement with Chern-Simons matter theory. We explicitly verify the double-copy correspondence at four and six points for N = 12,10,8 supergravity theories and discuss its validity for all multiplicity.
119118512
Worldgraph approach to Yang-Mills amplitudes from N = 2 spinning particle
By coupling the N = 2 spinning particle to background vector fields, we construct Yang-Mills amplitudes for trees and one loop. The vertex operators are derived through coupling the BRST charge; therefore background gauge invariance is manifest, and the Yang-Mills ghosts are automatically included in loop calculations by worldline ghosts. Inspired by string calculations, we extend the usual worldline approach to incorporate more ``generalized" 1D manifolds. This new approach should be useful for constructing higher-point and higher-loop amplitudes.
17646476
Running anti-de Sitter radius from QCD-like strings
We consider renormalization effects for a bosonic QCD-like string, whose partons have 1/p2 propagators instead of Gaussian. Classically this model resembles (the bosonic part of) the projective light-cone (zero-radius) limit of a string on an AdS5 background, where Schwinger parameters give rise to the fifth dimension. Quantum effects generate dynamics for this dimension, producing an AdS5 background with a running radius. The projective light-cone is the high-energy limit: Holography is enforced dynamically.
119241869
First-quantized N=4 Yang-Mills
We present simple first-class-constraint actions and BRST operators for the 4D N=4 superparticle in terms of a super anti-de Sitter coset. Each generation of ghosts has 2 super-indices, like the coordinates. The constraints that define projective superspace close in a super Yang-Mills background due to the presence of a (non-central) U(1) generator in the algebra.
119272120
Scattering Amplitudes
The purpose of this review is to bridge the gap between a standard course in quantum field theory and recent fascinating developments in the studies of on-shell scattering amplitudes. We build up the subject from basic quantum field theory, starting with Feynman rules for simple processes in Yukawa theory and QED. The material covered includes spinor helicity formalism, on-shell recursion relations, superamplitudes and their symmetries, twistors and momentum twistors, loops and integrands, Grassmannians, polytopes, and amplitudes in perturbative supergravity as well as 3d Chern-Simons-matter theories. Multiple examples and exercises are included. Part of textbook to be Published by Cambridge University Press ar X iv :1 30 8. 16 97 v2 [ he pth ] 1 1 A pr 2 01 4
119118243
Stability, ghost, and strong coupling in nonrelativistic general covariant theory of gravity with $\lambda \not=1$
In this paper, we investigate three important issues: stability, ghost, and strong coupling, in the Horava-Melby-Thompson setup of the Horava-Lifshitz theory with {lambda}{ne}1, generalized recently by da Silva. We first develop the general linear scalar perturbations of the Friedmann-Robertson-Walker (FRW) universe with arbitrary spatial curvature and find that an immediate by-product of the setup is that, in all the inflationary models described by a scalar field, the FRW universe is necessarily flat. Applying them to the case of the Minkowski background, we find that it is stable, and, similar to the case {lambda}=1, the spin-0 graviton is eliminated. The vector perturbations vanish identically in the Minkowski background. Thus, similar to general relativity, a free gravitational field in this setup is completely described by a spin-2 massless graviton, even with {lambda}{ne}1. We also study the ghost problem in the FRW background and find explicitly the ghost-free conditions. To study the strong coupling problem, we consider two different kinds of spacetimes, all with the presence of matter: one is cosmological, and the other is static. We find that the coupling becomes strong for a process with energy higher than M{sub pl}|c{sub {psi}|}{sup 5/2} in the flat FRW background and M{sub pl}|c{sub {psi}|}{sup more » 3} in a static weak gravitational field, where |c{sub {psi}|{identical_to}}|(1-{lambda})/(3{lambda}-1)|{sup 1/2}. « less
117084548
Determinations of the mass of the top quark.
118336548
Inflation in general covariant theory of gravity
In this paper, we study inflation in the framework of the nonrelativistic general covariant theory of the Hořava-Lifshitz gravity with the projectability condition and an arbitrary coupling constant λ. We find that the Friedmann-Robterson-Walker (FRW) universe is necessarily flat in such a setup. We work out explicitly the linear perturbations of the flat FRW universe without specifying to a particular gauge, and find that the perturbations are different from those obtained in general relativity, because of the presence of the high-order spatial derivative terms. Applying the general formulas to a single scalar field, we show that in the sub-horizon regions, the metric and scalar field are tightly coupled and have the same oscillating frequencies. In the super-horizon regions, the perturbations become adiabatic, and the comoving curvature perturbation is constant. We also calculate the power spectra and indices of both the scalar and tensor perturbations, and express them explicitly in terms of the slow roll parameters and the coupling constants of the high-order spatial derivative terms. In particular, we find that the perturbations, of both scalar and tensor, are almost scale-invariant, and, with some reasonable assumptions on the coupling coefficients, the spectrum index of the tensor perturbation is the same as that given in the minimum scenario in general relativity (GR), whereas the index for scalar perturbation in general depends on λ and is different from the standard GR value. The ratio of the scalar and tensor power spectra depends on the high-order spatial derivative terms, and can be different from that of GR significantly.
118537145
Slow-roll inflation preceded by a topological defect phase à la Chaplygin gas
We present a simple toy model corresponding to a network of frustrated topological defects of domain walls or cosmic strings that exist previous to the standard slow-roll inflationary era of the universe. Such a network (i) can produce a slower inflationary era than that of the standard scenario if it corresponds to a network of frustrated domain walls or (ii) can induce a vanishing universal acceleration; i.e., the universe would expand at a constant speed, if it corresponds to a network of frustrated cosmic strings red. Those features are phenomenologically modeled by a Chaplygin gas that can interpolate between a network of frustrated topological defects and a de Sitter-like or a power-law inflationary era. We show that this scenario can alleviate the quadruple anomaly of the cosmic microwave background spectrum. Using the method of the Bogoliubov coefficients, we obtain the spectrum of the gravitational waves as would be measured today for the whole range of frequencies. We comment on the possible detection of this spectrum by the planned detectors like BBO and DECIGO.
120554497
Inside-out tracking at CDF
The Central Outer Tracker (COT) at the Collider Detector at Fermilab (CDF) is used to reconstruct charged particles in the central rapidity region. The silicon tracker is used to improve the central track measurement and to reconstruct charged particles in the forward rapidity region. We describe the inside-out tracking algorithm, which improves the track measurement in the intermediate rapidity region by attaching COT hits to reconstructed silicon tracks.