7,980 research outputs found
Hunting for New Physics with Unitarity Boomerangs
Although the unitarity triangles () carry information about the
Kobayashi-Maskawa (KM) quark mixing matrix, it explicitly contains just three
parameters which is one short to completely fix the KM matrix. It has been
shown recently, by us, that the unitarity boomerangs () formed using two
, with a common inner angle, can completely determine the KM matrix and,
therefore, better represents, quark mixing. Here, we study detailed properties
of the , of which there are a total 18 possible. Among them, there is only
one which does not involve very small angles and is the ideal one for practical
uses. Although the have different areas, there is an invariant quantity,
for all , which is equal to a quarter of the Jarlskog parameter
squared. Hunting new physics, with a unitarity boomerang, can reveal more
information, than just using a unitarity triangle.Comment: Latex 9 pages with two figures. References updated
The nonplanar cusp and collinear anomalous dimension at four loops in SYM theory
We present numerical results for the nonplanar lightlike cusp and collinear
anomalous dimension at four loops in SYM theory, which we
infer from a calculation of the Sudakov form factor. The latter is expressed as
a rational linear combination of uniformly transcendental integrals for
arbitrary colour factor. Numerical integration in the nonplanar sector reveals
explicitly the breakdown of quadratic Casimir scaling at the four-loop order. A
thorough analysis of the reported numerical uncertainties is carried out.Comment: 10 pages, 2 figures, 1 table. Proceedings of the 13th International
Symposium on Radiative Corrections (Applications of Quantum Field Theory to
Phenomenology), 25-29 September, 2017, St. Gilgen, Austri
Nonlinear dynamics of a dense two-dimensional dipolar exciton gas
We use a simple model to describe the nonlinear dynamics of a dense two
dimensional dipolar exciton gas. The model predicts an initial fast expansion
due to dipole-dipole pressure, followed by a much slower diffusion. The model
is in very good agreement with recent experimental results. We show that the
dipole pressure induced expansion strongly constrains the time available for
achieving and observing Bose-Einstein quantum statistical effects, indicating a
need for spatial exciton traps. We also suggest that nonlinear ballistic
exciton transport due to the strong internal dipole pressure is readily
achievable.Comment: 5 pages, 4 figure
The Sudakov form factor at four loops in maximal super Yang-Mills theory
The four-loop Sudakov form factor in maximal super Yang-Mills theory is
analysed in detail. It is shown explicitly how to construct a basis of
integrals that have a uniformly transcendental expansion in the dimensional
regularisation parameter, further elucidating the number-theoretic properties
of Feynman integrals. The physical form factor is expressed in this basis for
arbitrary colour factor. In the nonplanar sector the required integrals are
integrated numerically using a mix of sector-decomposition and Mellin-Barnes
representation methods. Both the cusp as well as the collinear anomalous
dimension are computed. The results show explicitly the violation of quadratic
Casimir scaling at the four-loop order. A thorough analysis concerning the
reliability of reported numerical uncertainties is carried out.Comment: 47 pages, 17 figures; v4: fixed typo in eqs. (4.4) and (A.4), final
result unchange
Bosonic Anomalies, Induced Fractional Quantum Numbers and Degenerate Zero Modes: the anomalous edge physics of Symmetry-Protected Topological States
The boundary of symmetry-protected topological states (SPTs) can harbor new
quantum anomaly phenomena. In this work, we characterize the bosonic anomalies
introduced by the 1+1D non-onsite-symmetric gapless edge modes of 2+1D bulk
bosonic SPTs with a generic finite Abelian group symmetry (isomorphic to
). We
demonstrate that some classes of SPTs (termed "Type II") trap fractional
quantum numbers (such as fractional charges) at the 0D kink of the
symmetry-breaking domain walls; while some classes of SPTs (termed "Type III")
have degenerate zero energy modes (carrying the projective representation
protected by the unbroken part of the symmetry), either near the 0D kink of a
symmetry-breaking domain wall, or on a symmetry-preserving 1D system
dimensionally reduced from a thin 2D tube with a monodromy defect 1D line
embedded. More generally, the energy spectrum and conformal dimensions of
gapless edge modes under an external gauge flux insertion (or twisted by a
branch cut, i.e., a monodromy defect line) through the 1D ring can distinguish
many SPT classes. We provide a manifest correspondence from the physical
phenomena, the induced fractional quantum number and the zero energy mode
degeneracy, to the mathematical concept of cocycles that appears in the group
cohomology classification of SPTs, thus achieving a concrete physical
materialization of the cocycles. The aforementioned edge properties are
formulated in terms of a long wavelength continuum field theory involving
scalar chiral bosons, as well as in terms of Matrix Product Operators and
discrete quantum lattice models. Our lattice approach yields a regularization
with anomalous non-onsite symmetry for the field theory description. We also
formulate some bosonic anomalies in terms of the Goldstone-Wilczek formula.Comment: 29 pages, 12 Figures. v3 clarification to be accessible for both HEP
and CMT. Thanks to Roman Jackiw for introducing new Ref
Multi-task CNN Model for Attribute Prediction
This paper proposes a joint multi-task learning algorithm to better predict
attributes in images using deep convolutional neural networks (CNN). We
consider learning binary semantic attributes through a multi-task CNN model,
where each CNN will predict one binary attribute. The multi-task learning
allows CNN models to simultaneously share visual knowledge among different
attribute categories. Each CNN will generate attribute-specific feature
representations, and then we apply multi-task learning on the features to
predict their attributes. In our multi-task framework, we propose a method to
decompose the overall model's parameters into a latent task matrix and
combination matrix. Furthermore, under-sampled classifiers can leverage shared
statistics from other classifiers to improve their performance. Natural
grouping of attributes is applied such that attributes in the same group are
encouraged to share more knowledge. Meanwhile, attributes in different groups
will generally compete with each other, and consequently share less knowledge.
We show the effectiveness of our method on two popular attribute datasets.Comment: 11 pages, 3 figures, ieee transaction pape
Hydrogen Embrittlement of Aluminum: the Crucial Role of Vacancies
We report first-principles calculations which demonstrate that vacancies can
combine with hydrogen impurities in bulk aluminum and play a crucial role in
the embrittlement of this prototypical ductile solid. Our studies of
hydrogen-induced vacancy superabundant formation and vacancy clusterization in
aluminum lead to the conclusion that a large number of H atoms (up to twelve)
can be trapped at a single vacancy, which over-compensates the energy cost to
form the defect. In the presence of trapped H atoms, three nearest-neighbor
single vacancies which normally would repel each other, aggregate to form a
trivacancy on the slip plane of Al, acting as embryos for microvoids and cracks
and resulting in ductile rupture along the these planes.Comment: To appear in Phys. Rev. Let
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