65,537 research outputs found
T-Parity Violation by Anomalies
Little Higgs theories often rely on an internal parity ("T-parity'') to
suppress non-standard electroweak effects or to provide a dark matter
candidate. We show that such a symmetry is generally broken by anomalies, as
described by the Wess-Zumino-Witten term. We study a simple SU(3) x SU(3)/SU(3)
Little Higgs scheme where we obtain a minimal form for the topological
interactions of a single Higgs field. The results apply to more general models,
including [SU(3) x SU(3)/SU(3)]^4, SU(5)/SO(5), and SU(6)/Sp(6).Comment: 17 page
Topological Physics of Little Higgs Bosons
Topological interactions will generally occur in composite Higgs or Little
Higgs theories, extra-dimensional gauge theories in which A_5 plays the role of
a Higgs boson, and amongst the pNGB's of technicolor. This phenomena arises
from the chiral and anomaly structure of the underlying UV completion theory,
and/or through chiral delocalization in higher dimensions. These effects are
described by a full Wess-Zumino-Witten term involving gauge fields and pNGB's.
We give a general discussion of these interactions, some of which may have
novel signatures at future colliders, such as the LHC and ILC.Comment: 22 page
Anomalies, Chern-Simons Terms and Chiral Delocalization in Extra Dimensions
Gauge invariant topological interactions, such as the D=5 Chern-Simons terms,
are required in models in extra dimensions that split anomaly free
representations. The Chern-Simons term is necessary to maintain the overall
anomaly cancellations of the theory, but it can have significant, observable,
physical effects. The CS-term locks the KK-mode parity to the parity of
space-time, leaving a single parity symmetry. It leads to new processes amongst
KK-modes, eg, the decay of a KK-mode to a 2-body final state of KK-modes. A
formalism for the effective interaction amongst KK-modes is constructed, and
the decay of a KK-mode to KK-mode plus zero mode is analyzed as an example. We
elaborate the general KK-mode current and anomaly structure of these theories.
This includes a detailed study of the triangle diagrams and the associated
``consistent anomalies'' for Weyl spinors on the boundary branes. We also
develop the non-abelian formalism. We illustrate this by showing in a simple
way how a D=5 Yang-Mills ``quark flavor'' symmetry leads to the D=4 chiral
lagrangian of mesons and the quantized Wess-Zumino-Witten term.Comment: 51 pages, 3 figures; Corrected typos, amplified discussio
Performance Management in Portfolio School Districts
Explores the challenges of performance-based oversight of portfolio districts -- districts trying to provide diverse types of schools with common standards and accountability -- and the capacities needed. Includes profiles and best practices
Efficiency of autonomous soft nano-machines at maximum power
We consider nano-sized artificial or biological machines working in steady
state enforced by imposing non-equilibrium concentrations of solutes or by
applying external forces, torques or electric fields. For unicyclic and
strongly coupled multicyclic machines, efficiency at maximum power is not
bounded by the linear response value 1/2. For strong driving, it can even
approach the thermodynamic limit 1. Quite generally, such machines fall in
three different classes characterized, respectively, as "strong and efficient",
"strong and inefficient", and "balanced". For weakly coupled multicyclic
machines, efficiency at maximum power has lost any universality even in the
linear response regime
Z -> b\bar{b} Versus Dynamical Electroweak Symmetry Breaking involving the Top Quark
In models of dynamical electroweak symmetry breaking which sensitively
involve the third generation, such as top quark condensation, the effects of
the new dynamics can show up experimentally in Z->b\bar{b}. We compare the
sensitivity of Z->b\bar{b} and top quark production at the Tevatron to models
of the new physics. Z->b\bar{b} is a relatively more sensitive probe to new
strongly coupled U(1) gauge bosons, while it is generally less sensitive a
probe to new physics involving color octet gauge bosons as is top quark
production itself. Nonetheless, to accomodate a significant excess in
Z->b\bar{b} requires choosing model parameters that may be ruled out within run
I(b) at the Tevatron.Comment: LaTex file, 19 pages + 2 Figs., Fermilab-Pub-94/231-
Exact Equivalence of the D=4 Gauged Wess-Zumino-Witten Term and the D=5 Yang-Mills Chern-Simons Term
We derive the full Wess-Zumino-Witten term of a gauged chiral lagrangian in
D=4 by starting from a pure Yang-Mills theory of gauged quark flavor in a flat,
compactified D=5. The theory is compactified such that there exists a B_5 zero
mode, and supplemented with quarks that are ``chirally delocalized'' with q_L
(q_R) on the left (right) boundary (brane). The theory then necessarily
contains a Chern-Simons term (anomaly flux) to cancel the fermionic anomalies
on the boundaries. The constituent quark mass represents chiral symmetry
breaking and is a bilocal operator in D=5 of the form: \bar{q}_LWq_R+h.c, where
W is the Wilson line spanning the bulk, 0\leq x^5 \leq R and is interpreted as
a chiral meson field, W=\exp(2i\tilde{\pi}/f_\pi), where f_\pi \sim 1/R. The
quarks are integrated out, yielding a Dirac determinant which takes the form of
a ``boundary term'' (anomaly flux return), and is equivalent to Bardeen's
counterterm that connects consistent and covariant anomalies. The
Wess-Zumino-Witten term then emerges straightforwardly, from the Yang-Mills
Chern-Simons term, plus boundary term. The method is systematic and allows
generalization of the Wess-Zumino-Witten term to theories of extra dimensions,
and to express it in alternative and more compact forms. We give a novel form
appropriate to the case of (unintegrated) massless fermions.Comment: 25 pages, 1 figure; minor errors fixe
Adhesive for aluminum withstands cryogenic temperatures
Polyurethane adhesive mixed to various proportions with milled glass fibers match the thermal characteristics of 2014-T6 aluminum at cryogenic temperatures
An economic model of the manufacturers' aircraft production and airline earnings potential, volume 3
A behavioral explanation of the process of technological change in the U. S. aircraft manufacturing and airline industries is presented. The model indicates the principal factors which influence the aircraft (airframe) manufacturers in researching, developing, constructing and promoting new aircraft technology; and the financial requirements which determine the delivery of new aircraft to the domestic trunk airlines. Following specification and calibration of the model, the types and numbers of new aircraft were estimated historically for each airline's fleet. Examples of possible applications of the model to forecasting an individual airline's future fleet also are provided. The functional form of the model is a composite which was derived from several preceding econometric models developed on the foundations of the economics of innovation, acquisition, and technological change and represents an important contribution to the improved understanding of the economic and financial requirements for aircraft selection and production. The model's primary application will be to forecast the future types and numbers of new aircraft required for each domestic airline's fleet
Nickel layers on indium arsenide
We report here on the preparation and characterization of InAs substrates for in situ deposition of ferromagnetic contacts, a necessary precursor for semiconductor devices based on spin injection. InAs has been grown on InAs(111)A and (100) substrates by molecular-beam epitaxy and then metalized in situ in order to better understand the mechanisms that inhibit spin injection into a semiconductor. Initial x-ray characterization of the samples indicate the presence of nickel arsenides and indium–nickel compounds forming during deposition at temperatures above room temperature. Several temperature ranges have been investigated in order to determine the effect on nickel-arsenide formation. The presence of such compounds at the interface could greatly reduce the spin-injection efficiency and help elucidate previous unsuccessful attempts at measuring spin injection into InAs
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