2,819 research outputs found
Applications of Subleading-color Amplitudes in N=4 SYM Theory
A number of features and applications of subleading color amplitudes of N=4
SYM theory are reviewed. Particular attention is given to the IR divergences of
the subleading-color amplitudes, the relationships of N=4 SYM theory to N=8
supergravity, and to geometric interpretations of one-loop subleading color and
N^k MHV amplitudes of N=4 SYM theory.Comment: 39 pages; v2: minor correction
One-loop SYM-supergravity relation for five-point amplitudes
We derive a linear relation between the one-loop five-point amplitude of N=8
supergravity and the one-loop five-point subleading-color amplitudes of N=4
supersymmetric Yang-Mills theory.Comment: 17 pages, 2 figures; v2: very minor correction
Demonstration of dispersive rarefaction shocks in hollow elliptical cylinder chains
We report an experimental and numerical demonstration of dispersive
rarefaction shocks (DRS) in a 3D-printed soft chain of hollow elliptical
cylinders. We find that, in contrast to conventional nonlinear waves, these DRS
have their lower amplitude components travel faster, while the higher amplitude
ones propagate slower. This results in the backward-tilted shape of the front
of the wave (the rarefaction segment) and the breakage of wave tails into a
modulated waveform (the dispersive shock segment). Examining the DRS under
various impact conditions, we find the counter-intuitive feature that the
higher striker velocity causes the slower propagation of the DRS. These unique
features can be useful for mitigating impact controllably and efficiently
without relying on material damping or plasticity effects
Large-N Universality of the Two-Dimensional Yang-Mills String
We exhibit the gauge-group independence (``universality'') of all normalized
non-intersecting Wilson loop expectation values in the large N limit of
two-dimensional Yang-Mills theory. This universality is most easily understood
via the string theory reformulation of these gauge theories. By constructing an
isomorphism between the string maps contributing to normalized Wilson loop
expectation values in the different theories, we prove the large N universality
of these observables on any surface. The string calculation of the Wilson loop
expectation value on the sphere also leads to an indication of the large N
phase transition separating strong- and weak-coupling phases.Comment: 18 pages, phyzzx macro, no figure
Improved matrix-model calculation of the N=2 prepotential
We present a matrix-model expression for the sum of instanton contributions
to the prepotential of an N=2 supersymmetric U(N) gauge theory, with matter in
various representations. This expression is derived by combining the
renormalization-group approach to the gauge theory prepotential with
matrix-model methods. This result can be evaluated order-by-order in
matrix-model perturbation theory to obtain the instanton corrections to the
prepotential. We also show, using this expression, that the one-instanton
prepotential assumes a universal form.Comment: 20 pages, LaTeX, 2 figure
Amplitudes for massive vector and scalar bosons in spontaneously-broken gauge theory from the CHY representation
In the formulation of Cachazo, He, and Yuan, tree-level amplitudes for
massless particles in gauge theory and gravity can be expressed as rational
functions of the Lorentz invariants , ,
and , valid in any number of spacetime dimensions.
We use dimensional reduction of higher-dimensional amplitudes of particles with
internal momentum to obtain amplitudes for massive particles in lower
dimensions. In the case of gauge theory, we argue that these massive amplitudes
belong to a theory in which the gauge symmetry is spontaneously broken by an
adjoint Higgs field. Consequently, we show that tree-level -point amplitudes
containing massive vector and scalar bosons in this theory can be obtained by
simply replacing with in
the corresponding massless amplitudes, where the masses of the particles are
given by .Comment: 7 pages, no figures; v2: added paragraph, published versio
KLT-type relations for QCD and bicolor amplitudes from color-factor symmetry
Color-factor symmetry is used to derive a KLT-type relation for tree-level
QCD amplitudes containing gluons and an arbitrary number of massive or massless
quark-antiquark pairs, generalizing the expression for Yang-Mills amplitudes
originally postulated by Bern, De Freitas, and Wong. An explicit expression is
given for all amplitudes with two or fewer quark-antiquark pairs in terms of
the (modified) momentum kernel.
We also introduce the bicolor scalar theory, the "zeroth copy" of QCD,
containing massless biadjoint scalars and massive bifundamental scalars,
generalizing the biadjoint scalar theory of Cachazo, He, and Yuan. We derive
KLT-type relations for tree-level amplitudes of biadjoint and bicolor theories
using the color-factor symmetry possessed by these theories.Comment: 24 pages, 2 figures; v2: added referenc
Analytical Tendex and Vortex Fields for Perturbative Black Hole Initial Data
Tendex and vortex fields, defined by the eigenvectors and eigenvalues of the
electric and magnetic parts of the Weyl curvature tensor, form the basis of a
recently developed approach to visualizing spacetime curvature. In particular,
this method has been proposed as a tool for interpreting results from numerical
binary black hole simulations, providing a deeper insight into the physical
processes governing the merger of black holes and the emission of gravitational
radiation. Here we apply this approach to approximate but analytical initial
data for both single boosted and binary black holes. These perturbative data
become exact in the limit of small boost or large binary separation. We hope
that these calculations will provide additional insight into the properties of
tendex and vortex fields, and will form a useful test for future numerical
calculations.Comment: 18 pages, 8 figures, submitted to PR
Gravity darkening and brightening in binaries
We apply a von Zeipel gravity darkening model to corotating binaries to
obtain a simple, analytical expression for the emergent radiative flux from a
tidally distorted primary orbiting a point-mass secondary. We adopt a simple
Roche model to determine the envelope structure of the primary, assumed massive
and centrally condensed, and use the results to calculate the flux. As for
single rotating stars, gravity darkening reduces the flux along the stellar
equator of the primary, but, unlike for rotating stars, we find that gravity
brightening enhances the flux in a region around the stellar poles. We identify
a critical limiting separation beyond which hydrostatic equilibrium no longer
is possible, whereby the flux vanishes at the point on the stellar equator of
the primary facing the companion. For equal-mass binaries, the total luminosity
is reduced by about 13 % when this limiting separation is reached.Comment: 7 pages, 5 figures, matches version published in Astrophysical
Journa
Thermodynamics of the localized D2-D6 system
An exact fully-localized extremal supergravity solution for N_2 D2 branes and
N_6 D6 branes, which is dual to 3-dimensional supersymmetric SU(N_2) gauge
theory with N_6 fundamentals, was found by Cherkis and Hashimoto. In order to
consider the thermal properties of the gauge theory we present the non-extremal
extension of this solution to first order in an expansion near the core of the
D6 branes. We compute the Hawking temperature and the black brane horizon
area/entropy. The leading order entropy, which is proportional to N_2^{3/2}
N_6^{1/2} T_H^2, is not corrected to first order in the expansion. This result
is consistent with the analogous weak-coupling result at the correspondence
point N_2 ~ N_6.Comment: 14 page
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