34 research outputs found
The String Calculation of QCD Wilson Loops on Arbitrary Surfaces
Compact string expressions are found for non-intersecting 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.Comment: 10 pages, LaTeX, no figure
CP-Violating Yukawa Couplings in the Skyrme Model and the Neutron Electric Dipole Moment
We argue that the large-\Nc behaviour of the Yukawa couplings in the Skyrme
model involves issues more subtle than the vanishing of linear fluctuations
needed for classical stability of the skyrmion. The chiral fluctuations about
the skyrmion must be quantized in order to reach a conclusion. An improved
quantization procedure allows us to confront this question directly.
The pion-nucleon coupling constants \gcup (CP conserving) and \bgcup (CP
violating) are calculated in the large-\Nc, three-flavour Skyrme model by
direct evaluation of the leading matrix elements appearing in the LSZ reduction
formula. We find that \gcup \sim \Nc^{{3 \over 2}}, but that, at most,
\bgcup \sim m^2_\pi \Nc^{-\shalf}. These results show that the leading
contribution to the neutron electric dipole moment in large-\Nc Skyrme model
is the direct one (\Dn \sim \Nc m^2_\pi), rather than the pion loop
contribution.Comment: 12 pages, Latex with no macros, BRX-TH-33
Assessment of cochlear synaptopathy by electrocochleography to low frequencies in a preclinical model and human subjects
Cochlear synaptopathy is the loss of synapses between the inner hair cells and the auditory nerve despite survival of sensory hair cells. The findings of extensive cochlear synaptopathy in animals after moderate noise exposures challenged the long-held view that hair cells are the cochlear elements most sensitive to insults that lead to hearing loss. However, cochlear synaptopathy has been difficult to identify in humans. We applied novel algorithms to determine hair cell and neural contributions to electrocochleographic (ECochG) recordings from the round window of animal and human subjects. Gerbils with normal hearing provided training and test sets for a deep learning algorithm to detect the presence of neural responses to low frequency sounds, and an analytic model was used to quantify the proportion of neural and hair cell contributions to the ECochG response. The capacity to detect cochlear synaptopathy was validated in normal hearing and noise-exposed animals by using neurotoxins to reduce or eliminate the neural contributions. When the analytical methods were applied to human surgical subjects with access to the round window, the neural contribution resembled the partial cochlear synaptopathy present after neurotoxin application in animals. This result demonstrates the presence of viable hair cells not connected to auditory nerve fibers in human subjects with substantial hearing loss and indicates that efforts to regenerate nerve fibers may find a ready cochlear substrate for innervation and resumption of function
Simple-Current Symmetries, Rank-Level Duality, and Linear Skein Relations for Chern-Simons Graphs
A previously proposed two-step algorithm for calculating the expectation
values of 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. 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 uncover the classical
origin of simple-current charges. The improved skein relations also lead to
exact identities between planar tetrahedra in level and level
CS theories, where denotes a classical group. These results are
recast as identities for quantum -symbols and WZW braid matrices. We obtain
the transformation properties of arbitrary graphs 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.Comment: 58 pages, BRX-TH-30
Integrable N = 2 Landau-Ginzburg Theories from Quotients of Fusion Rings
The discovery of integrable supersymmetric Landau-Ginzburg theories
whose chiral rings are fusion rings suggests a close connection between fusion
rings, the related Landau-Ginzburg superpotentials, and quantum
integrability. We examine this connection by finding the natural
analogue of the construction that produced the superpotentials with
and fusion rings as chiral rings. The chiral rings of the new
superpotentials are not directly the fusion rings of any conformal field
theory, although they are natural quotients of the tensor subring of the
fusion ring.
The new superpotentials yield solvable (twisted ) topological field
theories. We obtain the integer-valued correlation functions as sums of
Verlinde dimensions by expressing the correlators as fusion residues.
The and related topological Landau-Ginzburg
theories are isomorphic, despite being defined via quite different
superpotentials.Comment: 34 pages, BRX-TH-34
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
String calculation of QCD Wilson loops on arbitrary surfaces
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