15,770 research outputs found
SU(3) Family Gauge Symmetry and the Axion
We analyze the structure of a recently proposed effective field theory (EFT)
for the generation of quark and lepton mass ratios and mixing angles, based on
the spontaneous breaking of an SU(3) family gauge symmetry at a high scale F.
We classify the Yukawa operators necessary to seed the masses, making use of
the continuous global symmetries that they preserve. One global U(1), in
addition to baryon number and electroweak hypercharge, remains unbroken after
the inclusion of all operators required by standard-model-fermion
phenomenology. An associated vacuum symmetry insures the vanishing of the
first-family quark and charged-lepton masses in the absence of the family gauge
interaction. If this U(1) symmetry is taken to be exact in the EFT, broken
explicitly by only the QCD-induced anomaly, and if the breaking scale F is
taken to lie in the range 10 to 9 - 10 to 12 GeV, then the associated
Nambu-Goldstone boson is a potential QCD axion.Comment: References added and clarifications in Vacuum Structure sectio
Neutrinos and SU(3) Family Gauge Symmetry
We include the standard-model (SM) leptons in a recently proposed framework
for the generation of quark mass ratios and Cabibbo-Kobayashi-Maskawa (CKM)
mixing angles from an SU(3) family gauge interaction. The set of SM-singlet
scalar fields describing the spontaneous breaking is the same as employed for
the quark sector. The imposition at tree-level of the experimentally correct
Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix, in the form of a tri-bi
maximal structure, fixes several of the otherwise free parameters and renders
the model predictive. The normal hierarchy among the neutrino masses emerges
from this scheme.Comment: 9 pages, 3 tables; a comment added to clarify the effects of
additional Yukawa operators; final version in PR
The Loss Rank Principle for Model Selection
We introduce a new principle for model selection in regression and
classification. Many regression models are controlled by some smoothness or
flexibility or complexity parameter c, e.g. the number of neighbors to be
averaged over in k nearest neighbor (kNN) regression or the polynomial degree
in regression with polynomials. Let f_D^c be the (best) regressor of complexity
c on data D. A more flexible regressor can fit more data D' well than a more
rigid one. If something (here small loss) is easy to achieve it's typically
worth less. We define the loss rank of f_D^c as the number of other
(fictitious) data D' that are fitted better by f_D'^c than D is fitted by
f_D^c. We suggest selecting the model complexity c that has minimal loss rank
(LoRP). Unlike most penalized maximum likelihood variants (AIC,BIC,MDL), LoRP
only depends on the regression function and loss function. It works without a
stochastic noise model, and is directly applicable to any non-parametric
regressor, like kNN. In this paper we formalize, discuss, and motivate LoRP,
study it for specific regression problems, in particular linear ones, and
compare it to other model selection schemes.Comment: 16 page
Testing linear hypotheses in high-dimensional regressions
For a multivariate linear model, Wilk's likelihood ratio test (LRT)
constitutes one of the cornerstone tools. However, the computation of its
quantiles under the null or the alternative requires complex analytic
approximations and more importantly, these distributional approximations are
feasible only for moderate dimension of the dependent variable, say .
On the other hand, assuming that the data dimension as well as the number
of regression variables are fixed while the sample size grows, several
asymptotic approximations are proposed in the literature for Wilk's \bLa
including the widely used chi-square approximation. In this paper, we consider
necessary modifications to Wilk's test in a high-dimensional context,
specifically assuming a high data dimension and a large sample size .
Based on recent random matrix theory, the correction we propose to Wilk's test
is asymptotically Gaussian under the null and simulations demonstrate that the
corrected LRT has very satisfactory size and power, surely in the large and
large context, but also for moderately large data dimensions like or
. As a byproduct, we give a reason explaining why the standard chi-square
approximation fails for high-dimensional data. We also introduce a new
procedure for the classical multiple sample significance test in MANOVA which
is valid for high-dimensional data.Comment: Accepted 02/2012 for publication in "Statistics". 20 pages, 2 pages
and 2 table
Breaking Discrete Symmetries in Broken Gauge Theories
We study the spontaneous breaking of discrete symmetries in theories with
broken gauge symmetry. The intended application is to CP breaking in theories
with gauged flavor symmetries, but the analysis described here is preliminary.
We dispense with matter fields and take the gauge theory to be weakly coupled
and broken spontaneously by unspecified, short-distance forces. We develop an
effective-field-theory description of the resultant low energy theory, and ask
whether this theory by itself can describe the subsequent breaking of discrete
symmetries. We conclude that this can happen depending on the parameters of the
effective theory, and that the intrinsic violation is naturally of order unity.Comment: 9 pages, 1 figure, corrected typos, added a referenc
Dual-mode mechanical resonance of individual ZnO nanobelts
©2003 American Institute of Physics. The electronic version of this article is the complete one and can be found online at: http://link.aip.org/link/?APPLAB/82/4806/1DOI:10.1063/1.1587878The mechanical resonance of a single ZnO nanobelt, induced by an alternative electric field, was studied by in situ transmission electron microscopy. Due to the rectangular cross section of the nanobelt, two fundamental resonance modes have been observed corresponding to two orthogonal transverse vibration directions, showing the versatile applications of nanobelts as nanocantilevers and nanoresonators. The bending modulus of the ZnO nanobelts was measured to be ~52 GPa and the damping time constant of the resonance in a vacuum of 5×10–8 Torr was ~1.2 ms and quality factor Q = 500
First-principles and model simulation of all-optical spin reversal
All-optical spin switching is a potential trailblazer for information storage
and communication at an unprecedented fast rate and free of magnetic fields.
However, the current wisdom is largely based on semiempirical models of
effective magnetic fields and heat pulses, so it is difficult to provide
high-speed design protocols for actual devices. Here, we carry out a massively
parallel first-principles and model calculation for thirteen spin systems and
magnetic layers, free of any effective field, to establish a simpler and
alternative paradigm of laser-induced ultrafast spin reversal and to point out
a path to a full-integrated photospintronic device. It is the interplay of the
optical selection rule and sublattice spin orderings that underlines seemingly
irreconcilable helicity-dependent/independent switchings. Using realistic
experimental parameters, we predict that strong ferrimagnets, in particular,
Laves phase C15 rare-earth alloys, meet the telecommunication energy
requirement of 10 fJ, thus allowing a cost-effective subpicosecond laser to
switch spin in the GHz region.Comment: 23 pages, 6 figures and one tabl
Exploring expressive augmented reality: The fing AR puppet system for social pretend play
We present “FingAR Puppet”, an Augmented Reality (AR) system enhancing social pretend play by young children. Un-like goal-oriented AR systems that augment reality with in-formative instructions, FingAR Puppet helps children asso-ciate expressive interpretations with immediate reality. Em-pirical results show that FingAR Puppet promotes reasoning about emotional states, communication and divergent think-ing during social pretend play for children 4-6 years old. We suggest that this study opens an interesting space for future AR systems to support complex cognitive and social devel-opment in early childhood. We also identify broader implica-tions from using theories of cognitive development to guide the design of tangible and augmented interactions
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