15,298 research outputs found
On Lorentz invariance and supersymmetry of four particle scattering amplitudes in orbifold sigma model
The supersymmetric orbifold sigma model is expected to describe the
IR limit of the Matrix string theory. In the framework of the model the type
IIA string interaction is governed by a vertex which was recently proposed by
R.Dijkgraaf, E.Verlinde and H.Verlinde. By using this interaction vertex we
derive all four particle scattering amplitudes directly from the orbifold model
in the large limit.Comment: Latex, 23 page
Multipole particle in relativity
We discuss the motion of extended objects in a spacetime by considering a
gravitational field created by these objects. We define multipole moments of
the objects as a classification by Lie group SO(3). Then, we construct an
energy-momentum tensor for the objects and derive equations of motion from it.
As a result, we reproduce the Papapetrou equations for a spinning particle.
Furthermore, we will show that we can obtain more simple equations than the
Papapetrou equations by changing the center-of-mass.Comment: 22 pages, 2 figures. Accepted for publication in Phys. Rev.
Self-forces on extended bodies in electrodynamics
In this paper, we study the bulk motion of a classical extended charge in
flat spacetime. A formalism developed by W. G. Dixon is used to determine how
the details of such a particle's internal structure influence its equations of
motion. We place essentially no restrictions (other than boundedness) on the
shape of the charge, and allow for inhomogeneity, internal currents,
elasticity, and spin. Even if the angular momentum remains small, many such
systems are found to be affected by large self-interaction effects beyond the
standard Lorentz-Dirac force. These are particularly significant if the
particle's charge density fails to be much greater than its 3-current density
(or vice versa) in the center-of-mass frame. Additional terms also arise in the
equations of motion if the dipole moment is too large, and when the
`center-of-electromagnetic mass' is far from the `center-of-bare mass' (roughly
speaking). These conditions are often quite restrictive. General equations of
motion were also derived under the assumption that the particle can only
interact with the radiative component of its self-field. These are much simpler
than the equations derived using the full retarded self-field; as are the
conditions required to recover the Lorentz-Dirac equation.Comment: 30 pages; significantly improved presentation; accepted for
publication in Phys. Rev.
Geodetic, teleseismic, and strong motion constraints on slip from recent southern Peru subduction zone earthquakes
We use seismic and geodetic data both jointly and separately to constrain coseismic slip from the 12 November 1996 M_w 7.7 and 23 June 2001 M_w 8.5 southern Peru subduction zone earthquakes, as well as two large aftershocks following the 2001 earthquake on 26 June and 7 July 2001. We use all available data in our inversions: GPS, interferometric synthetic aperture radar (InSAR) from the ERS-1, ERS-2, JERS, and RADARSAT-1 satellites, and seismic data from teleseismic and strong motion stations. Our two-dimensional slip models derived from only teleseismic body waves from South American subduction zone earthquakes with M_w > 7.5 do not reliably predict available geodetic data. In particular, we find significant differences in the distribution of slip for the 2001 earthquake from models that use only seismic (teleseismic and two strong motion stations) or geodetic (InSAR and GPS) data. The differences might be related to postseismic deformation or, more likely, the different sensitivities of the teleseismic and geodetic data to coseismic rupture properties. The earthquakes studied here follow the pattern of earthquake directivity along the coast of western South America, north of 5°S, earthquakes rupture to the north; south of about 12°S, directivity is southerly; and in between, earthquakes are bilateral. The predicted deformation at the Arequipa GPS station from the seismic-only slip model for the 7 July 2001 aftershock is not consistent with significant preseismic motion
Multi-jet cross sections at NLO with BlackHat and Sherpa
In this talk, we report on a recent next-to-leading order QCD calculation of
the production of a W boson in association with three jets at hadron colliders.
The computation is performed by combining two programs, BlackHat for the
computation of the virtual one-loop matrix elements and Sherpa for the real
emission part.Comment: 4 pages, contribution to the proceedings of the XLIIIth Rencontres de
Moriond (QCD
Next-to-Leading Order Jet Physics with BlackHat
We present several results obtained using the BlackHat next-to-leading order
QCD program library, in conjunction with SHERPA. In particular, we present
distributions for vector boson plus 1,2,3-jet production at the Tevatron and at
the asymptotic running energy of the Large Hadron Collider, including new
Z+3-jet distributions. The Z+2-jet predictions for the second-jet P_T
distribution are compared to CDF data. We present the jet-emission probability
at NLO in W+2-jet events at the LHC, where the tagging jets are taken to be the
ones furthest apart in pseudorapidity. We analyze further the large left-handed
W polarization, identified in our previous study, for W bosons produced at high
P_T at the LHC.Comment: Presented at RADCOR 2009 - 9th International Symposium on Radiative
Corrections (Applications of Quantum Field Theory to Phenomenology), October
25 - 30 2009, Ascona, Switzerland}, 12 pages, 9 figures, LaTeX, v2 updated
small correction to polarization effect plo
The Ultraviolet Behavior of N=8 Supergravity at Four Loops
We describe the construction of the complete four-loop four-particle
amplitude of N=8 supergravity. The amplitude is ultraviolet finite, not only in
four dimensions, but in five dimensions as well. The observed extra
cancellations provide additional non-trivial evidence that N=8 supergravity in
four dimensions may be ultraviolet finite to all orders of perturbation theory.Comment: 5 pages, 4 figures. v2 contains minor corrections, including flipping
sign of eq. (1). Complete results, including mathematica readable form,
presented in the directory aux/ included in the source of this manuscript. As
certain computer operating systems (e.g. Windows) preclude the naming of
directories "aux" we also host this data at:
http://www.physics.ucla.edu/~jjmc/auxiliaryData.tg
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