5,279 research outputs found
A Model of Two Dimensional Turbulence Using Random Matrix Theory
We derive a formula for the entropy of two dimensional incompressible
inviscid flow, by determining the volume of the space of vorticity
distributions with fixed values for the moments Q_k= \int_w(x)^k d^2 x. This
space is approximated by a sequence of spaces of finite volume, by using a
regularization of the system that is geometrically natural and connected with
the theory of random matrices. In taking the limit we get a simple formula for
the entropy of a vortex field. We predict vorticity distributions of maximum
entropy with given mean vorticity and enstrophy; also we predict the
cylindrically symmetric vortex field with maximum entropy. This could be an
approximate description of a hurricane.Comment: latex, 12 pages, 2 figures, acknowledgement adde
First law of black hole mechanics in Einstein-Maxwell and Einstein-Yang-Mills theories
The first law of black hole mechanics is derived from the Einstein-Maxwell
(EM) Lagrangian by comparing two infinitesimally nearby stationary black holes.
With similar arguments, the first law of black hole mechanics in
Einstein-Yang-Mills (EYM) theory is also derived.Comment: Modified version, major changes made in the introduction. 14 pages,
no figur
An Efficient Bandit Algorithm for Realtime Multivariate Optimization
Optimization is commonly employed to determine the content of web pages, such
as to maximize conversions on landing pages or click-through rates on search
engine result pages. Often the layout of these pages can be decoupled into
several separate decisions. For example, the composition of a landing page may
involve deciding which image to show, which wording to use, what color
background to display, etc. Such optimization is a combinatorial problem over
an exponentially large decision space. Randomized experiments do not scale well
to this setting, and therefore, in practice, one is typically limited to
optimizing a single aspect of a web page at a time. This represents a missed
opportunity in both the speed of experimentation and the exploitation of
possible interactions between layout decisions.
Here we focus on multivariate optimization of interactive web pages. We
formulate an approach where the possible interactions between different
components of the page are modeled explicitly. We apply bandit methodology to
explore the layout space efficiently and use hill-climbing to select optimal
content in realtime. Our algorithm also extends to contextualization and
personalization of layout selection. Simulation results show the suitability of
our approach to large decision spaces with strong interactions between content.
We further apply our algorithm to optimize a message that promotes adoption of
an Amazon service. After only a single week of online optimization, we saw a
21% conversion increase compared to the median layout. Our technique is
currently being deployed to optimize content across several locations at
Amazon.com.Comment: KDD'17 Audience Appreciation Awar
On the Noether charge form of the first law of black hole mechanics
The first law of black hole mechanics was derived by Wald in a general
covariant theory of gravity for stationary variations around a stationary black
hole. It is formulated in terms of Noether charges, and has many advantages. In
this paper several issues are discussed to strengthen the validity of the
Noether charge form of the first law. In particular, a gauge condition used in
the derivation is justified. After that, we justify the generalization to
non-stationary variations done by Iyer-Wald.Comment: Latex, 16 pages, arguments on gauge conditions and near-stationary
entropy are added, accepted for publication in Physical Review
A nucleosome-free dG-dC-rich sequence element promotes constitutive transcription of the essential yeast RIO1 gene
RIO1 is an essential gene that encodes a protein serine kinase and is transcribed constitutively at a very low level. Transcriptional activation of RIO1 dispenses with a canonical TATA box as well as with classical transactivators or specific DNAbinding factors. Instead, a dGdCrich sequence element, that is located 40 to 48 bp upstream the single site of mRNA initiation, is essential and presumably constitutes the basal promoter. In addition, we demonstrate here that this promoter element comprises a nucleosomefree gap which is centered at the dGdC tract and flanked by two positioned nucleosomes. This element is both, necessary and sufficient, for basal transcription initiation at the RIO1 promoter and, thus, constitutes a novel type of core promoter element
PCV42 IMPACT OF VENTRICULAR ARRHYTHMIAS ON HOSPITALIZATION COSTS IN PATIENTS WITH ACUTE MYOCARDIAL INFARCTION (AMI)
Magnetic anomalies in Gd6Co1.67Si3 and Tb6Co1.67Si3
The compounds, Gd6Co1.67Si3 and Tb6Co1.67Si3, recently reported to form in a
Ce6Ni2Si3-derived hexagonal structure (space group: P6_3 / m) and to order
magnetically below 295 and 190 K respectively, have been investigated by
detailed magnetization (M) studies in the temperature interval 1.8-330 K as a
function of magnetic field (H). The points of emphasis are: We observe multiple
steps in the M(H) curve for the Tb compound at 1.8 K while increasing H, but
these steps do not appear in the reverse cycle of H. At higher temperatures,
such steps are absent. However, this 'staircase' behavior of M(H) is not
observed for the Gd compound at any temperature and the isothermal
magnetization is not hysteretic unlike in Tb compound. From the M(H) data
measured at close intervals of temperature, we have derived isothermal entropy
change (Delta S) and it is found that Delta S follows a theoretically predicted
H^2/3-dependence
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