840 research outputs found
Correlation function of null polygonal Wilson loops with local operators
We consider the correlator of a light-like polygonal Wilson loop
with n cusps with a local operator (like the dilaton or the chiral primary
scalar) in planar N =4 super Yang-Mills theory. As a consequence of conformal
symmetry, the main part of such correlator is a function F of 3n-11 conformal
ratios. The first non-trivial case is n=4 when F depends on just one conformal
ratio \zeta. This makes the corresponding correlator one of the simplest
non-trivial observables that one would like to compute for generic values of
the `t Hooft coupling \lambda. We compute F(\zeta,\lambda) at leading order in
both the strong coupling regime (using semiclassical AdS5 x S5 string theory)
and the weak coupling regime (using perturbative gauge theory). Some results
are also obtained for polygonal Wilson loops with more than four edges.
Furthermore, we also discuss a connection to the relation between a correlator
of local operators at null-separated positions and cusped Wilson loop suggested
in arXiv:1007.3243.Comment: 36 pages, 2 figure
OPE for Super Loops
We extend the Operator Product Expansion for Null Polygon Wilson loops to the
Mason-Skinner-Caron-Huot super loop, dual to non MHV gluon amplitudes. We
explain how the known tree level amplitudes can be promoted into an infinite
amount of data at any loop order in the OPE picture. As an application, we
re-derive all one loop NMHV six gluon amplitudes by promoting their tree level
expressions. We also present some new all loops predictions for these
amplitudes.Comment: 16 pages + appendices; 5 figure
On soft singularities at three loops and beyond
We report on further progress in understanding soft singularities of massless
gauge theory scattering amplitudes. Recently, a set of equations was derived
based on Sudakov factorization, constraining the soft anomalous dimension
matrix of multi-leg scattering amplitudes to any loop order, and relating it to
the cusp anomalous dimension. The minimal solution to these equations was shown
to be a sum over color dipoles. Here we explore potential contributions to the
soft anomalous dimension that go beyond the sum-over-dipoles formula. Such
contributions are constrained by factorization and invariance under rescaling
of parton momenta to be functions of conformally invariant cross ratios.
Therefore, they must correlate the color and kinematic degrees of freedom of at
least four hard partons, corresponding to gluon webs that connect four eikonal
lines, which first appear at three loops. We analyze potential contributions,
combining all available constraints, including Bose symmetry, the expected
degree of transcendentality, and the singularity structure in the limit where
two hard partons become collinear. We find that if the kinematic dependence is
solely through products of logarithms of cross ratios, then at three loops
there is a unique function that is consistent with all available constraints.
If polylogarithms are allowed to appear as well, then at least two additional
structures are consistent with the available constraints.Comment: v2: revised version published in JHEP (minor corrections in Sec. 4;
added discussion in Sec. 5.3; refs. added); v3: minor corrections (eqs. 5.11,
5.12 and 5.29); 38 pages, 3 figure
Hexagon remainder function in the limit of self-crossing up to three loops
We consider Wilson loops in planar N=4 SYM for null polygons in the limit of
two crossing edges. The analysis is based on a renormalisation group technique.
We show that the previously obtained result for the leading and next-leading
divergent term of the two loop hexagon remainder is in full agreement with the
appropriate continuation of the exact analytic formula for this quantity.
Furthermore, we determine the coefficients of the leading and next-leading
singularity for the three loop remainder function for null n-gons with n >= 6.Comment: 19 pages, 4 figures, typos corrected, comment on relation to recent
results for the symbol of three-loop remainder added, version to appear in
JHE
MoM total hip replacements in Europe: a NORE report
The purpose of this paper is to determine the prevalence of metal-on-metal (MoM) total hip replacement (THR) in European registries, to assess the incidence of revision surgery and to describe the national follow-up guidelines for patients with MoM THR including resurfacings.Eleven registries of the Network of Orthopaedic Registries of Europe (NORE) participated totalling 54 434 resurfacings and 58 498 large stemmed MoM THRs.The resurfacings and stemmed large head MoM had higher pooled revision rates at five years than the standard total hip arthroplasties (THA): 6.0%, 95% confidence interval (CI) 5.3 to 6.8 for resurfacings; 6.9%, 95% CI 4.4 to 9.4 for stemmed large head MoM; and 3.0%, 95% CI 2.5 to 3.6 for conventional THA.The resurfacings and stemmed large head MoM had higher pooled revision rates at ten years than the standard THAs: 12.1%, 95% CI 11.0 to 13.3 for resurfacings; 15.5%, 95% CI 9.0 to 22 for stemmed large head MoM; and 5.1%, 95% CI 3.8 to 6.4 for conventional THA.Although every national registry reports slightly different protocols for follow-up, these mostly consist of annual assessments of cobalt and chromium levels in blood and MRI (MARS) imaging
Systematics of the cusp anomalous dimension
We study the velocity-dependent cusp anomalous dimension in supersymmetric
Yang-Mills theory. In a paper by Correa, Maldacena, Sever, and one of the
present authors, a scaling limit was identified in which the ladder diagrams
are dominant and are mapped onto a Schrodinger problem. We show how to solve
the latter in perturbation theory and provide an algorithm to compute the
solution at any loop order. The answer is written in terms of harmonic
polylogarithms. Moreover, we give evidence for two curious properties of the
result. Firstly, we observe that the result can be written using a subset of
harmonic polylogarithms only, at least up to six loops. Secondly, we show that
in a light-like limit, only single zeta values appear in the asymptotic
expansion, again up to six loops. We then extend the analysis of the scaling
limit to systematically include subleading terms. This leads to a
Schrodinger-type equation, but with an inhomogeneous term. We show how its
solution can be computed in perturbation theory, in a way similar to the
leading order case. Finally, we analyze the strong coupling limit of these
subleading contributions and compare them to the string theory answer. We find
agreement between the two calculations.Comment: 33 pages, 4 figures. Complete LO six-loop result added. Typos
corrected. Version accepted for publicatio
K-Decompositions and 3d Gauge Theories
This paper combines several new constructions in mathematics and physics.
Mathematically, we study framed flat PGL(K,C)-connections on a large class of
3-manifolds M with boundary. We define a space L_K(M) of framed flat
connections on the boundary of M that extend to M. Our goal is to understand an
open part of L_K(M) as a Lagrangian in the symplectic space of framed flat
connections on the boundary, and as a K_2-Lagrangian, meaning that the
K_2-avatar of the symplectic form restricts to zero. We construct an open part
of L_K(M) from data assigned to a hypersimplicial K-decomposition of an ideal
triangulation of M, generalizing Thurston's gluing equations in 3d hyperbolic
geometry, and combining them with the cluster coordinates for framed flat
PGL(K)-connections on surfaces. Using a canonical map from the complex of
configurations of decorated flags to the Bloch complex, we prove that any
generic component of L_K(M) is K_2-isotropic if the boundary satisfies some
topological constraints (Theorem 4.2). In some cases this implies that L_K(M)
is K_2-Lagrangian. For general M, we extend a classic result of Neumann-Zagier
on symplectic properties of PGL(2) gluing equations to reduce the
K_2-Lagrangian property to a combinatorial claim.
Physically, we use the symplectic properties of K-decompositions to construct
3d N=2 superconformal field theories T_K[M] corresponding (conjecturally) to
the compactification of K M5-branes on M. This extends known constructions for
K=2. Just as for K=2, the theories T_K[M] are described as IR fixed points of
abelian Chern-Simons-matter theories. Changes of triangulation (2-3 moves) lead
to abelian mirror symmetries that are all generated by the elementary duality
between N_f=1 SQED and the XYZ model. In the large K limit, we find evidence
that the degrees of freedom of T_K[M] grow cubically in K.Comment: 121 pages + 2 appendices, 80 figures; Version 2: reorganized
mathematical perspective, swapped Sections 3 and
Ratio of the Isolated Photon Cross Sections at \sqrt{s} = 630 and 1800 GeV
The inclusive cross section for production of isolated photons has been
measured in \pbarp collisions at GeV with the \D0 detector at
the Fermilab Tevatron Collider. The photons span a transverse energy ()
range from 7-49 GeV and have pseudorapidity . This measurement is
combined with to previous \D0 result at GeV to form a ratio
of the cross sections. Comparison of next-to-leading order QCD with the
measured cross section at 630 GeV and ratio of cross sections show satisfactory
agreement in most of the range.Comment: 7 pages. Published in Phys. Rev. Lett. 87, 251805, (2001
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
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