1,371 research outputs found
Online Learning of k-CNF Boolean Functions
This paper revisits the problem of learning a k-CNF Boolean function from
examples in the context of online learning under the logarithmic loss. In doing
so, we give a Bayesian interpretation to one of Valiant's celebrated PAC
learning algorithms, which we then build upon to derive two efficient, online,
probabilistic, supervised learning algorithms for predicting the output of an
unknown k-CNF Boolean function. We analyze the loss of our methods, and show
that the cumulative log-loss can be upper bounded, ignoring logarithmic
factors, by a polynomial function of the size of each example.Comment: 20 LaTeX pages. 2 Algorithms. Some Theorem
Sparse Sequential Dirichlet Coding
This short paper describes a simple coding technique, Sparse Sequential
Dirichlet Coding, for multi-alphabet memoryless sources. It is appropriate in
situations where only a small, unknown subset of the possible alphabet symbols
can be expected to occur in any particular data sequence. We provide a
competitive analysis which shows that the performance of Sparse Sequential
Dirichlet Coding will be close to that of a Sequential Dirichlet Coder that
knows in advance the exact subset of occurring alphabet symbols. Empirically we
show that our technique can perform similarly to the more computationally
demanding Sequential Sub-Alphabet Estimator, while using less computational
resources.Comment: 7 page
Reinforcement Learning via AIXI Approximation
This paper introduces a principled approach for the design of a scalable
general reinforcement learning agent. This approach is based on a direct
approximation of AIXI, a Bayesian optimality notion for general reinforcement
learning agents. Previously, it has been unclear whether the theory of AIXI
could motivate the design of practical algorithms. We answer this hitherto open
question in the affirmative, by providing the first computationally feasible
approximation to the AIXI agent. To develop our approximation, we introduce a
Monte Carlo Tree Search algorithm along with an agent-specific extension of the
Context Tree Weighting algorithm. Empirically, we present a set of encouraging
results on a number of stochastic, unknown, and partially observable domains.Comment: 8 LaTeX pages, 1 figur
ATLAS BEAM VACUUM SYSTEM INTERFACES
This document describes the main interfaces between the LHC beam vacuum system and the ATLAS detector
Atypical energy eigenstates in the Hubbard chain and quantum disentangled liquids
We investigate the implications of integrability for the existence of quantum
disentangled liquid (QDL) states in the half-filled one-dimensional Hubbard
model. We argue that there exist finite energy-density eigenstates that exhibit
QDL behaviour in the sense of J. Stat. Mech. P10010 (2014). These states are
atypical in the sense that their entropy density is smaller than that of
thermal states at the same energy density. Furthermore, we show that thermal
states in a particular temperature window exhibit a weaker form of the QDL
property, in agreement with recent results obtained by strong-coupling
expansion methods in arXiv:1611.02075. This article is part of the themed issue
`Breakdown of ergodicity in quantum systems: from solids to synthetics matter'.Comment: 11 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1611.0207
The ATLAS beam vacuum system
The Large Hadron Collider (LHC) has recently started-up at CERN. It will provide colliding beams to four experiments installed in large underground caverns. A specially designed and constructed sector of the LHC beam vacuum system transports the beams though each of these collision regions, forming a primary interface between machine and experiment. ATLAS [1] is the largest of the four LHC colliding beam experiments, being some 40 m long and 22 m in diameter. Physics performance, geometry and access imposed a large number of constraints on the design of the beam vacuum system. This paper describes the geometry and layout of the ATLAS beam vacuum system. Specific technologies developed for ATLAS, and for the alignment and installation of the vacuum chambers are described as well as the issues related to the physical interfaces with the experiment
What is Causing This Man\u27s Rectal Pain and Urinary Retention?
Case: A 23-year-old man presented to an urgent care office with a 2-week history of rectal pain and scant rectal bleeding. In the few days leading up to his presentation, he also had a fever of 101° F (38.3° C), inguinal lymphadenopathy, and urinary retention
Recommended from our members
A service evaluation of parent adherence with dysphagia management therapy guidelines: Reports from family carers supporting children with complex needs in Greece
Purpose: Many children with complex needs exhibit eating, drinking and/or swallowing disorders (dysphagia). These children often have associated learning needs, and require assistance from carers for daily tasks such as eating and drinking. The aim of this study was to identify which strategies to manage dysphagia were challenging for family carers, and reasons for any non-adherence.
Method: In this service evaluation researchers observed carers during mealtimes, and investigated carer opinions of strategies used to minimise the risks of dysphagia. Eight children with complex needs aged 3.4 - 7.5 years and their primary family caregiver participated.
Results: Adherence with speech and language pathologists’
dysphagia recommendations overall was over 50% in all but one case. For specific strategies, the highest adherence was observed for diet modifications of foods (89%), communication during the mealtime (83%), amount of food to present (81%) and the pacing of fluids and foods (81%). Lower levels of adherence were identified in relation to postural management (58%), environmental changes (58%), utensils (56%) and preparatory strategies (49%).
Conclusion: Adherence with use of strategies to support mealtimes was over 50% in all but one case. Findings suggest that support is essential in order to promote safe mealtimes, reduce family carers’ stress and increase knowledge, confidence and adherence in implementing dysphagia guidelines in the family home
Real-time dynamics in the one-dimensional Hubbard model
We consider single-particle properties in the one-dimensional repulsive
Hubbard model at commensurate fillings in the metallic phase. We determine the
real-time evolution of the retarded Green's function by matrix-product state
methods. We find that at sufficiently late times the numerical results are in
good agreement with predictions of nonlinear Luttinger liquid theory. We argue
that combining the two methods provides a way of determining the
single-particle spectral function with very high frequency resolution.Comment: 10 pages, 6 figures. Minor edits from v1. Version as publishe
- …