4,154 research outputs found
Model-Independent Constraints on Lorentz Invariance Violation via the Cosmographic Approach
Since Lorentz invariance plays an important role in modern physics, it is of
interest to test the possible Lorentz invariance violation (LIV). The time-lag
(the arrival time delay between light curves in different energy bands) of
Gamma-ray bursts (GRBs) has been extensively used to this end. However, to our
best knowledge, one or more particular cosmological models were assumed {\it a
priori} in (almost) all of the relevant works in the literature. So, this makes
the results on LIV in those works model-dependent and hence not so robust in
fact. In the present work, we try to avoid this problem by using a
model-independent approach. We calculate the time delay induced by LIV with the
cosmic expansion history given in terms of cosmography, without assuming any
particular cosmological model. Then, we constrain the possible LIV with the
observational data, and find weak hints for LIV.Comment: 15 pages, 4 figures, 3 tables, revtex4; v2: discussions added, Phys.
Lett. B in pres
Quantifying and Reducing Stereotypes in Word Embeddings
Machine learning algorithms are optimized to model statistical properties of
the training data. If the input data reflects stereotypes and biases of the
broader society, then the output of the learning algorithm also captures these
stereotypes. In this paper, we initiate the study of gender stereotypes in {\em
word embedding}, a popular framework to represent text data. As their use
becomes increasingly common, applications can inadvertently amplify unwanted
stereotypes. We show across multiple datasets that the embeddings contain
significant gender stereotypes, especially with regard to professions. We
created a novel gender analogy task and combined it with crowdsourcing to
systematically quantify the gender bias in a given embedding. We developed an
efficient algorithm that reduces gender stereotype using just a handful of
training examples while preserving the useful geometric properties of the
embedding. We evaluated our algorithm on several metrics. While we focus on
male/female stereotypes, our framework may be applicable to other types of
embedding biases.Comment: presented at 2016 ICML Workshop on #Data4Good: Machine Learning in
Social Good Applications, New York, N
Artificial Gauge Field and Quantum Spin Hall States in a Conventional Two-dimensional Electron Gas
Based on the Born-Oppemheimer approximation, we divide total electron
Hamiltonian in a spinorbit coupled system into slow orbital motion and fast
interband transition process. We find that the fast motion induces a gauge
field on slow orbital motion, perpendicular to electron momentum, inducing a
topological phase. From this general designing principle, we present a theory
for generating artificial gauge field and topological phase in a conventional
two-dimensional electron gas embedded in parabolically graded
GaAs/InGaAs/GaAs quantum wells with antidot lattices. By tuning
the etching depth and period of antidot lattices, the band folding caused by
superimposed potential leads to formation of minibands and band inversions
between the neighboring subbands. The intersubband spin-orbit interaction opens
considerably large nontrivial minigaps and leads to many pairs of helical edge
states in these gaps.Comment: 9 pages and 4 figure
Extraction and Recovery of Cerium from Rare Earth Ore by Solvent Extraction
Rare earth elements are widely found in many minerals, some of which, such as bastnaesite, monazite, and xenotime, are of great commercial value. Cerium (Ce) is the rare earth element with the highest content in light rare earth ore. Solvent extraction is the most effective and efficient method to recover and separate Ce from other light rare earth elements. After acid leaching of rare earth minerals, leaching solution was obtained, and cerium oxide of products of high purity was obtained by extraction and stripping. It is well known that Ce(IV) can be easily separated from the other RE(III) by adopting the traditional solvent extraction. Based on this principle, the clean process of oxidation roasting and Ce(IV) separation for Sichuan bastnaesite was developed. And then, a preliminary flow sheet of two-step oxidation and extraction of Ce(IV) for Bayan Obo mixed rare earth ores was further proposed
Seismic pounding between adjacent buildings of unequal floor height
When the story heights of adjacent buildings are unequal, the inter-floor pounding maybe happen during earthquake. Employing substructures in pounding area, the analytical model of adjacent structures with unequal story height is developed, and the equations of motion considering pounding are derived. Based on analytical model, the inter-floor pounding responses of adjacent buildings with unequal story height are investigated. The corresponding parametrical studies are conducted and influence rules are concluded. The results show that the influences of inter-floor pounding in adjacent buildings on main structures are smaller than those of floor pounding. But the damages on pounding area are quite large. Moreover, the period ratio of structures, the initial gap and the pounding location have remarkable influence on responses of inter-floor pounding
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