17,830 research outputs found
Weak local rules for planar octagonal tilings
We provide an effective characterization of the planar octagonal tilings
which admit weak local rules. As a corollary, we show that they are all based
on quadratic irrationalities, as conjectured by Thang Le in the 90s.Comment: 23 pages, 6 figure
The Causality Relationship between Hnx Index and Stock Trading Volume in Hanoi Stock Exchange
This paper examines the casual relations between the market return and trading volume for the Ha Noi Stock Exchange during the period from May 3th , 2013 to March 2rd, 2016. This paper uses Granger test and the results showed that the change of the volume of transactions that affect the change of HNX-Index. On the basis of this conclusion, we shall determine the degree of influence of the change in trading volume with HNX-Index by means of regression analysis
Exploring Deep Space: Learning Personalized Ranking in a Semantic Space
Recommender systems leverage both content and user interactions to generate
recommendations that fit users' preferences. The recent surge of interest in
deep learning presents new opportunities for exploiting these two sources of
information. To recommend items we propose to first learn a user-independent
high-dimensional semantic space in which items are positioned according to
their substitutability, and then learn a user-specific transformation function
to transform this space into a ranking according to the user's past
preferences. An advantage of the proposed architecture is that it can be used
to effectively recommend items using either content that describes the items or
user-item ratings. We show that this approach significantly outperforms
state-of-the-art recommender systems on the MovieLens 1M dataset.Comment: 6 pages, RecSys 2016 RSDL worksho
Gamma-Ray Bursts as a Probe of the Very High Redshift Universe
We show that, if many GRBs are indeed produced by the collapse of massive
stars, GRBs and their afterglows provide a powerful probe of the very high
redshift (z > 5) universe.Comment: To appear in Proc. of the 5th Huntsville Gamma-Ray Burst Symposium, 5
pages, LaTe
Cosmological Constant in LQG Vertex Amplitude
A new q-deformation of the Euclidean EPRL/FK vertex amplitude is proposed by
using the evaluation of the Vassiliev invariant associated with a 4-simplex
graph (related to two copies of quantum SU(2) group at different roots of
unity) embedded in a 3-sphere. We show that the large-j asymptotics of the
q-deformed vertex amplitude gives the Regge action with a cosmological
constant. In the end we also discuss its relation with a Chern-Simons theory on
the boundary of 4-simplex.Comment: 6 pages, 5 figures, result and presentation improve
Words are Malleable: Computing Semantic Shifts in Political and Media Discourse
Recently, researchers started to pay attention to the detection of temporal
shifts in the meaning of words. However, most (if not all) of these approaches
restricted their efforts to uncovering change over time, thus neglecting other
valuable dimensions such as social or political variability. We propose an
approach for detecting semantic shifts between different viewpoints--broadly
defined as a set of texts that share a specific metadata feature, which can be
a time-period, but also a social entity such as a political party. For each
viewpoint, we learn a semantic space in which each word is represented as a low
dimensional neural embedded vector. The challenge is to compare the meaning of
a word in one space to its meaning in another space and measure the size of the
semantic shifts. We compare the effectiveness of a measure based on optimal
transformations between the two spaces with a measure based on the similarity
of the neighbors of the word in the respective spaces. Our experiments
demonstrate that the combination of these two performs best. We show that the
semantic shifts not only occur over time, but also along different viewpoints
in a short period of time. For evaluation, we demonstrate how this approach
captures meaningful semantic shifts and can help improve other tasks such as
the contrastive viewpoint summarization and ideology detection (measured as
classification accuracy) in political texts. We also show that the two laws of
semantic change which were empirically shown to hold for temporal shifts also
hold for shifts across viewpoints. These laws state that frequent words are
less likely to shift meaning while words with many senses are more likely to do
so.Comment: In Proceedings of the 26th ACM International on Conference on
Information and Knowledge Management (CIKM2017
First-principles study on the structural and electronic properties of single-layer MoSi2N4
Motivated by the successful exfoliation of a novel two-dimensional MoSi2N4 materials, in this work, we investigate the structural and electronic properties of a novel single-layer MoSi2N4 and the effect of strain engineering by using the first-principles calculations based on the density functional theory. The single-layer MoSi2N4 has a hexagonal structure with a space group of P6m1, which is dynamically stable. The material exhibits a semiconducting characteristic with an indirect band gap of 1.80/2.36 eV calculated by using the PBE/HSE functional. The conduction band minimum at the K point of the material originates from the Mo atom, while its valence band maximum at the G point is contributed by the hybridization between the Mo and N atoms. The electronic properties of the single-layer MoSi2N4 can be modulated with strain engineering, giving rise to a transition from a semiconductor to a metal and tending to a change in the band gap. Our results demonstrate that the single-layer MoSi2N4 is a promising candidate for electronic and optoelectronic applications
Atom trapping and guiding with a subwavelength-diameter optical fiber
We suggest using an evanescent wave around a thin fiber to trap atoms. We
show that the gradient force of a red-detuned evanescent-wave field in the
fundamental mode of a silica fiber can balance the centrifugal force when the
fiber diameter is about two times smaller than the wavelength of the light and
the component of the angular momentum of the atoms along the fiber axis is in
an appropriate range. As an example, the system should be realizable for Cesium
atoms at a temperature of less than 0.29 mK using a silica fiber with a radius
of 0.2 m and a 1.3-m-wavelength light with a power of about 27 mW.Comment: 5 pages, 5 figure
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