17,325 research outputs found
Higher Spin BRS Cohomology of Supersymmetric Chiral Matter in D=4
We examine the BRS cohomology of chiral matter in , supersymmetry
to determine a general form of composite superfield operators which can suffer
from supersymmetry anomalies. Composite superfield operators \Y_{(a,b)} are
products of the elementary chiral superfields and \ov S and the
derivative operators D_\a, \ov D_{\dot \b} and \pa_{\a \dot \b}. Such
superfields \Y_{(a,b)} can be chosen to have `' symmetrized undotted
indices \a_i and `' symmetrized dotted indices \dot \b_j. The result
derived here is that each composite superfield \Y_{(a,b)} is subject to
potential supersymmetry anomalies if is an odd number, which means that
\Y_{(a,b)} is a fermionic superfield.Comment: 15 pages, CPT-TAMU-20/9
The Last of the Finite Loop Amplitudes in QCD
We use on-shell recursion relations to determine the one-loop QCD scattering
amplitudes with a massless external quark pair and an arbitrary number (n-2) of
positive-helicity gluons. These amplitudes are the last of the unknown
infrared- and ultraviolet-finite loop amplitudes of QCD. The recursion
relations are similar to ones applied at tree level, but contain new
non-trivial features corresponding to poles present for complex momentum
arguments but absent for real momenta. We present the relations and the compact
solutions to them, valid for all n. We also present compact forms for the
previously-computed one-loop n-gluon amplitudes with a single negative helicity
and the rest positive helicity.Comment: 45 pages, revtex, 7 figures, v2 minor correction
Device and method for frictionally testing materials for ignitability
Test apparatus for determining ignition characteristics of various metal in oxidizer environments simulating operating conditions for materials is invented. The test apparatus has a chamber through which the oxidizing agent flows, and means for mounting a stationary test sample therein, a powered, rotating shaft in the chamber rigidly mounts a second test sample. The shaft is axially movable to bring the samples into frictional engagement and heated to the ignition point. Instrumentation connected to the apparatus provides for observation of temperatures, pressures, loads on and speeds of the rotating shaft, and torques whereby components of stressed oxygen systems can be selected which will avoid accidental fires under working conditions
Recursive Construction of Higgs-Plus-Multiparton Loop Amplitudes: The Last of the Phi-nite Loop Amplitudes
We consider a scalar field, such as the Higgs boson H, coupled to gluons via
the effective operator H tr G_{mu nu} G^{mu nu} induced by a heavy-quark loop.
We treat H as the real part of a complex field phi which couples to the
self-dual part of the gluon field-strength, via the operator phi tr G_{SD mu
nu} G_{SD}^{mu nu}, whereas the conjugate field phi^dagger couples to the
anti-self-dual part. There are three infinite sequences of amplitudes coupling
phi to quarks and gluons that vanish at tree level, and hence are finite at one
loop, in the QCD coupling. Using on-shell recursion relations, we find compact
expressions for these three sequences of amplitudes and discuss their analytic
properties.Comment: 63 pages, 7 figures; v2 references added; v3 minor typos corrected
and note added; v4 fixed error in eq. (7.11) (lower limit of sum should be
l=2, not l=3), also affecting eqs. (7.14), (8.20), (8.21), (8.27) and (8.28
Unitarity Cuts with Massive Propagators and Algebraic Expressions for Coefficients
In the first part of this paper, we extend the d-dimensional unitarity cut
method of hep-ph/0609191 to cases with massive propagators. We present formulas
for integral reduction with which one can obtain coefficients of all pentagon,
box, triangle and massive bubble integrals. In the second part of this paper,
we present a detailed study of the phase space integration for unitarity cuts.
We carry out spinor integration in generality and give algebraic expressions
for coefficients, intended for automated evaluation.Comment: 33 pages. v2: notation modified. v3: typos fixe
Multipole structure of current vectors in curved spacetime
A method is presented which allows the exact construction of conserved (i.e.
divergence-free) current vectors from appropriate sets of multipole moments.
Physically, such objects may be taken to represent the flux of particles or
electric charge inside some classical extended body. Several applications are
discussed. In particular, it is shown how to easily write down the class of all
smooth and spatially-bounded currents with a given total charge. This
implicitly provides restrictions on the moments arising from the smoothness of
physically reasonable vector fields. We also show that requiring all of the
moments to be constant in an appropriate sense is often impossible; likely
limiting the applicability of the Ehlers-Rudolph-Dixon notion of quasirigid
motion. A simple condition is also derived that allows currents to exist in two
different spacetimes with identical sets of multipole moments (in a natural
sense).Comment: 13 pages, minor changes, accepted to J. Math. Phy
Bootstrapping One-Loop QCD Amplitudes with General Helicities
The recently developed on-shell bootstrap for computing one-loop amplitudes
in non-supersymmetric theories such as QCD combines the unitarity method with
loop-level on-shell recursion. For generic helicity configurations, the
recursion relations may involve undetermined contributions from non-standard
complex singularities or from large values of the shift parameter. Here we
develop a strategy for sidestepping difficulties through use of pairs of
recursion relations. To illustrate the strategy, we present sets of recursion
relations needed for obtaining n-gluon amplitudes in QCD. We give a recursive
solution for the one-loop n-gluon QCD amplitudes with three or four
color-adjacent gluons of negative helicity and the remaining ones of positive
helicity. We provide an explicit analytic formula for the QCD amplitude
A_{6;1}(1^-,2^-,3^-,4^+,5^+,6^+), as well as numerical results for
A_{7;1}(1^-,2^-,3^-,4^+,5^+,6^+,7^+), A_{8;1}(1^-,2^-,3^-,4^+,5^+,6^+,7^+,8^+),
and A_{8;1}(1^-,2^-,3^-,4^-,5^+,6^+,7^+,8^+). We expect the on-shell bootstrap
approach to have widespread applications to phenomenological studies at
colliders.Comment: 77 pages, 17 figures; v2, corrected minor typos in text and small
equation
Immunofluorescent Examination of Biopsies from Long-Term Renal Allografts
Immunofluorescent examination of open renal biopsies revealed clear-cut glomerular localization of immunoglobulins not related clearly to the quality of donor-recipient histocompatibility in 19 of 34 renal allografts. The biopsies were obtained 18 to 31 months after transplantations primarily from related donors with a variable quality of histocompatibility match. IgG was the predominant immunoglobulin class fixed in 13 biopsies, and IgM in six. The pattern of immunoglobulin deposition was linear, connoting anti-GBM antibody in four of the 19; it was granular and discontinuous, connoting antigen–antibodycomplex deposits, in 13. An immune process may affect glomeruli of renal allografts by mechanisms comparable to those that cause glomerulonephritis in native kidneys. The transplant glomerulonephritis may represent a persistence of the same disease that originally destroyed the host kidneys or the consequence of a new humoral antibody response to allograft antigens. © 1970, Massachusetts Medical Society. All rights reserved
Testing Gravity in the Outer Solar System: Results from Trans-Neptunian Objects
The inverse square law of gravity is poorly probed by experimental tests at
distances of ~ 10 AUs. Recent analysis of the trajectory of the Pioneer 10 and
11 spacecraft have shown an unmodeled acceleration directed toward the Sun
which was not explained by any obvious spacecraft systematics, and occurred
when at distances greater than 20 AUs from the Sun. If this acceleration
represents a departure from Newtonian gravity or is indicative of an additional
mass distribution in the outer solar system, it should be detectable in the
orbits of Trans-Neptunian Objects (TNOs). To place limits on deviations from
Newtonian gravity, we have selected a well observed sample of TNOs found
orbiting between 20 and 100 AU from the Sun. By examining their orbits with
modified orbital fitting software, we place tight limits on the perturbations
of gravity that could exist in this region of the solar system.Comment: 20 pages, 4 figures, 2 tables, uses AASTex v5.x macro
New Relations for Gauge-Theory Amplitudes
We present an identity satisfied by the kinematic factors of diagrams
describing the tree amplitudes of massless gauge theories. This identity is a
kinematic analog of the Jacobi identity for color factors. Using this we find
new relations between color-ordered partial amplitudes. We discuss applications
to multi-loop calculations via the unitarity method. In particular, we
illustrate the relations between different contributions to a two-loop
four-point QCD amplitude. We also use this identity to reorganize gravity tree
amplitudes diagram by diagram, offering new insight into the structure of the
KLT relations between gauge and gravity tree amplitudes. This can be used to
obtain novel relations similar to the KLT ones. We expect this to be helpful in
higher-loop studies of the ultraviolet properties of gravity theories.Comment: 40 pages, 7 figures, RevTex, v2 minor correction
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