6,034 research outputs found
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
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
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
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
Methods for evaluating the performance of volume phase holographic gratings for the VIRUS spectrograph array
The Visible Integral Field Replicable Unit Spectrograph (VIRUS) is an array
of at least 150 copies of a simple, fiber-fed integral field spectrograph that
will be deployed on the Hobby-Eberly Telescope (HET) to carry out the HET Dark
Energy Experiment (HETDEX). Each spectrograph contains a volume phase
holographic grating as its dispersing element that is used in first order for
350 nm to 550 nm. We discuss the test methods used to evaluate the performance
of the prototype gratings, which have aided in modifying the fabrication
prescription for achieving the specified batch diffraction efficiency required
for HETDEX. In particular, we discuss tests in which we measure the diffraction
efficiency at the nominal grating angle of incidence in VIRUS for all orders
accessible to our test bench that are allowed by the grating equation. For
select gratings, these tests have allowed us to account for > 90% of the
incident light for wavelengths within the spectral coverage of VIRUS. The
remaining light that is unaccounted for is likely being diffracted into
reflective orders or being absorbed or scattered within the grating layer (for
bluer wavelengths especially, the latter term may dominate the others).
Finally, we discuss an apparatus that will be used to quickly verify the first
order diffraction efficiency specification for the batch of at least 150 VIRUS
production gratings.Comment: 18 pages, 11 figures. To be published in Proc. SPIE, 2012,
"Ground-Based and Airborne Instrumentation for Astronomy IV", 8446-20
Ecological and physical characteristics of the Te Awa O Katapaki Stream, Flagstaff, Waikato
1. The fish, macroinvertebrates, aquatic vegetation, and water quality indicate that the Te Awa O Katapaki Stream is an unpolluted, pastureland stream that is typical of the Waikato region.
2. The stream has very high nutrient concentrations that probably result from the dairy farming upstream.
3. The fish fauna is dominated by the native shortfinned eels. The presence of the migratory common smelt indicates that swimming fish species also have free access to the stream from the Waikato River.
4. Fish of high conservation value, such as giant or banded kokopu (Galaxias argenteus or G. fasciatus) were absent, which is predictable given the warm, unshaded nature of the stream.
5. Fish and invertebrates would soon recolonise the restored stream following any work in the streambed
Cosmological structure formation from soft topological defects
Some models have extremely low-mass pseudo-Goldstone bosons that can lead to vacuum phase transitions at late times, after the decoupling of the microwave background.. This can generate structure formation at redshifts z greater than or approx 10 on mass scales as large as M approx 10 to the 18th solar masses. Such low energy transitions can lead to large but phenomenologically acceptable density inhomogeneities in soft topological defects (e.g., domain walls) with minimal variations in the microwave anisotropy, as small as delta Y/T less than or approx 10 to the minus 6 power. This mechanism is independent of the existence of hot, cold, or baryonic dark matter. It is a novel alternative to both cosmic string and to inflationary quantum fluctuations as the origin of structure in the Universe
Anomaly mediated neutrino-photon interactions at finite baryon density
We propose new physical processes based on the axial vector anomaly and
described by the Wess-Zumino-Witten term that couples the photon, Z-boson, and
the omega-meson. The interaction takes the form of a pseudo-Chern-Simons term,
. This term
induces neutrino-photon interactions at finite baryon density via the coupling
of the Z-boson to neutrinos. These interactions may be detectable in various
laboratory and astrophysical arenas. The new interactions may account for the
MiniBooNE excess. They also produce a competitive contribution to neutron star
cooling at temperatures >10^9 K. These processes and related axion--photon
interactions at finite baryon density appear to be relevant in many
astrophysical regimes.Comment: 4 pages, 2 figures; references adde
- …