Showing 3651 - 3700 of 5831 Items
Eikonal methods applied to gravitational scattering amplitudes
Date: 2011-01-01
Creator: Stephen G. Naculicha, Howard J. Schnitzerb
Access: Open access
- We apply factorization and eikonal methods from gauge theories to scattering amplitudes in gravity. We hypothesize that these amplitudes factor into an IR-divergent soft function and an IR-finite hard function, with the former given by the expectation value of a product of gravitational Wilson line operators. Using this approach, we show that the IR-divergent part of the n-graviton scattering amplitude is given by the exponential of the one-loop IR divergence, as originally discovered byWeinberg, with no additional subleading IR-divergent contributions in dimensional regularization. © SISSA 2011.
Simple-current symmetries, rank-level duality, and linear skein relations for Chern-Simons graphs
Date: 1993-04-12
Creator: Stephen G. Naculich, Harold A. Riggs, Howard J. Schnitzer
Access: Open access
- A previously proposed two-step algorithm for calculating the expectation values of arbitrary Chern-Simons graphs fails to determine certain crucial signs. The step which involves calculating tetrahedra by solving certain non-linear equations is repaired by introducing additional linear equations. The step which involves reducing arbitrary graphs to sums of products of tetrahedra remains seriously disabled, apart from a few exceptional cases. As a first step towards a new algorithm for general graphs we find useful linear equations for those special graphs which support knots and links. Using the improved set of equations for tetrahedra we examine the symmetries between tetrahedra generated by arbitrary simple currents. Along the way we describe the simple, classical origin of simple-current charges. The improved skein relations also lead to exact identities between planar tetrahedra in level K G(N) and level N G(K) Chern-Simons theories, where G(N) denotes a classical group. These results are recast as WZW braid-matrix identities and as identities between quantum 6-jsymbols at appropriate roots of unity. We also obtain the transformation properties of arbitrary graphs, knots, and links under simple-current symmetries and rank-level duality. For links with knotted components this requires precise control of the braid eigenvalue permutation signs, which we obtain from plethysm and an explicit expression for the (multiplicity-free) signs, valid for all compact gauge groups and all fusion products. © 1993.
Superconformal coset equivalence from level-rank duality
Date: 1997-11-17
Creator: Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- We construct a one-to-one map between the primary fields of the N = 2 superconformal Kazama-Suzuki models G(m, n, k) and G(k, n, m) based on complex Grassmannian cosets, using level-rank duality of Wess-Zumino-Witten models. We then show that conformal weights, superconformal U(1) charges, modular transformation matrices, and fusion rules are preserved under this map, providing strong evidence for the equivalence of these coset models. © 1997 Elsevier Science B.V.
String calculation of QCD Wilson loops on arbitrary surfaces
Date: 1995-01-01
Creator: Stephen G. Naculich, Harold A. Riggs
Access: Open access
- Compact string expressions are found for nonintersecting Wilson loops in SU(N) Yang-Mills theory on any surface (orientable or nonorientable) as a weighted sum over covers of the surface. All terms from the coupled chiral sectors of the 1/N expansion of the Wilson loop expectation values are included. © 1995 The American Physical Society.
Twisted D-branes of the over(su, ̂) (N)K WZW model and level-rank duality
Date: 2006-10-30
Creator: Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- We analyze the level-rank duality of ωc-twisted D-branes of over(su, ̂) (N)K (when N and K > 2). When N or K is even, the duality map involves Z2-cominimal equivalence classes of twisted D-branes. We prove the duality of the spectrum of an open string stretched between ωc-twisted D-branes, and ascertain the relation between the charges of level-rank-dual ωc-twisted D-branes. © 2006 Elsevier B.V. All rights reserved.
The N = 2 U(N) gauge theory prepotential and periods from a perturbative matrix model calculation
Date: 2003-02-24
Creator: Stephen G. Naculich, Howard J. Schnitzer, Niclas Wyllard
Access: Open access
- We perform a completely perturbative matrix model calculation of the physical low-energy quantities of the N = 2 U(N) gauge theory. Within the matrix model framework we propose a perturbative definition of the periods a i in terms of certain tadpole diagrams, and check our conjecture up to first order in the gauge theory instanton expansion. The prescription does not require knowledge of the Seiberg-0Witten differential or curve.We also compute the N = 2 prepotential F(a) perturbatively up to the first-instanton level, finding agreement with the known result. 2002 Elsevier Science B.V. All rights reserved.
Precision measurement of the Ds*+-Ds+ mass difference
Date: 1994-01-01
Creator: D. N. Brown, J. Fast, R. L. McIlwain, T. Miao, D. H., Miller, M. Modesitt, D. Payne, E. I. Shibata, I. P.J. Shipsey, P. N. Wang, M. Battle, J. Ernst, Y. Kwon, S. Roberts, E. H. Thorndike, C. H. Wang, J. Dominick, M. Lambrecht, S. Sanghera, V. Shelkov, T. Skwarnicki, R. Stroynowski, I. Volobouev, G. Wei, P. Zadorozhny, M. Artuso, M. Goldberg, D. He, N. Horwitz, R. Kennett, R. Mountain
Access: Open access
- We have measured the vector-pseudoscalar mass splitting M(Ds*+)-M(Ds+)=144.220.470.37 MeV significantly more precisely than the previous world average. We minimize the systematic errors by also measuring the vector-pseudoscalar mass difference M(D*0)-M(D0) using the radiative decay D*0D0, obtaining [M(Ds*+)-M(Ds+)]-[M(D*0)-M(D0)] =2.090.470.37 MeV. This is then combined with our previous high-precision measurement of M(D*0)-M(D0), which used the decay D*0D00. We also measure the mass difference M(Ds+)-M(D+)=99.50.60.3 MeV, using the + decay modes of the Ds+ and D+ mesons. © 1994 The American Physical Society.
Search for exclusive b→u semileptonic decays of B mesons
Date: 1993-01-01
Creator: A. Bean, J. Gronberg, R. Kutschke, S. Menary, R. J., Morrison, H. N. Nelson, J. D. Richman, H. Tajima, D. Schmidt, D. Sperka, M. S. Witherell, M. Procario, S. Yang, R. Ballest, M. Daoudi, W. T. Ford, D. R. Johnson, K. Lingel, M. Lohner, P. Rankin, J. G. Smith, J. P. Alexander, C. Bebek, K. Berkelman, D. Besson, T. E. Browder, D. G. Cassel, H. A. Cho, D. M. Coffman, P. S. Drell, R. Ehrlich
Access: Open access
- Using a sample of 935 000 BB̄ pairs collected with the CLEO-II detector at the Cornell Electron Storage Ring, we have obtained upper limits on the branching ratios for the b→ul-ν̄ processes B-→ωl- ν̄, B-→ρ0l-ν̄, and B̄0→ρ+l-ν̄. The combined result using the relationships among the widths for these three modes is B(B-→ρ0l-ν̄)<(1.6-2.7)×10-4 at 90% C.L., where the range of values is due to model dependence of the detection efficiencies. These measurements yield the limits Vub/Vcb<0.08-0.13. © 1993 The American Physical Society.