1,941 research outputs found
On Factor Universality in Symbolic Spaces
The study of factoring relations between subshifts or cellular automata is
central in symbolic dynamics. Besides, a notion of intrinsic universality for
cellular automata based on an operation of rescaling is receiving more and more
attention in the literature. In this paper, we propose to study the factoring
relation up to rescalings, and ask for the existence of universal objects for
that simulation relation. In classical simulations of a system S by a system T,
the simulation takes place on a specific subset of configurations of T
depending on S (this is the case for intrinsic universality). Our setting,
however, asks for every configurations of T to have a meaningful interpretation
in S. Despite this strong requirement, we show that there exists a cellular
automaton able to simulate any other in a large class containing arbitrarily
complex ones. We also consider the case of subshifts and, using arguments from
recursion theory, we give negative results about the existence of universal
objects in some classes
On the zero-temperature limit of Gibbs states
We exhibit Lipschitz (and hence H\"older) potentials on the full shift
such that the associated Gibbs measures fail to converge
as the temperature goes to zero. Thus there are "exponentially decaying"
interactions on the configuration space for which the
zero-temperature limit of the associated Gibbs measures does not exist. In
higher dimension, namely on the configuration space ,
, we show that this non-convergence behavior can occur for finite-range
interactions, that is, for locally constant potentials.Comment: The statement of Theorem 1.2 is more accurate and some new comment
follow i
Small union with large set of centers
Let be a fixed set. By a scaled copy of around
we mean a set of the form for some .
In this survey paper we study results about the following type of problems:
How small can a set be if it contains a scaled copy of around every point
of a set of given size? We will consider the cases when is circle or sphere
centered at the origin, Cantor set in , the boundary of a square
centered at the origin, or more generally the -skeleton () of an
-dimensional cube centered at the origin or the -skeleton of a more
general polytope of .
We also study the case when we allow not only scaled copies but also scaled
and rotated copies and also the case when we allow only rotated copies
A novel twoâbeam accelerator (twobetron)
A new configuration is analyzed wherein a low current beam is accelerated to high energies (10âs of amps, 10âs of MeV) by a driver beam of high current and low energy (a few kiloamps, <1 MeV). The annular driver beam excites the TM020 cavity mode of an accelerating structure which transfers its rf power to the onâaxis secondary beam. Systematic variation of the driver beam radius provides the secondary beam with phase focusing and adjustable acceleration gradient. A proofâofâprinciple experiment is suggested. Various issues, such as the scaling laws, transverse and longitudinal instabilities, rf coupling among cavities, etc., are examined. © 1995 American Institute of PHysics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87548/2/451_1.pd
Reformas, instituiçÔes e polĂticas de saĂșde no Brasil (1930-1945)
O objetivo geral desse artigo Ă© descrever e analisar de modo sucinto as principais mudanças institucionais e tendĂȘncias polĂticas no setor de saĂșde durante o Primeiro Governo Vargas, em particular na gestĂŁo de Gustavo Capanema, no MinistĂ©rio da Educação e SaĂșde (1934-1945). Um aspecto enfatizado no artigo Ă© a relação entre as reformas da saĂșde e as mudanças e ideologia do regime polĂtico instaurado em 1930, indicando permanĂȘncias e rupturas em relação ao perĂodo republicano anterior, assim como os impactos dessas reformas sobre a saĂșde pĂșblica no Brasil contemporĂąneo
The Role of Supported Joint Engagement and Parent Utterances in Language and Social Communication Development in Children with Autism Spectrum Disorder
This study examined associations between three parentâchild engagement states and social communication, expressive language, and receptive language at 8 month follow-up, in 63 preschool-age children with autism spectrum disorder. We extend the literature on supported joint engagement by dividing this state into higher order (HSJE) and lower order types, with HSJE involving greater reciprocity in toy play. We also examined parentsâ follow-in utterances that co-occurred with each state. We found that only HSJE predicts later social communication and expressive language, while object engagement predicts receptive language. HSJE combined with follow-in utterances (HSJE+FI) predicts all three outcomes when controlling for HSJE+FI in other engagement states. When controlling for total HSJE, HSJE+FI is predictive of receptive language
Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA
Inclusive photoproduction of D*+- mesons has been measured for photon-proton
centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality
Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of
37 pb^-1. Total and differential cross sections as functions of the D*
transverse momentum and pseudorapidity are presented in restricted kinematical
regions and the data are compared with next-to-leading order (NLO) perturbative
QCD calculations using the "massive charm" and "massless charm" schemes. The
measured cross sections are generally above the NLO calculations, in particular
in the forward (proton) direction. The large data sample also allows the study
of dijet production associated with charm. A significant resolved as well as a
direct photon component contribute to the cross section. Leading order QCD
Monte Carlo calculations indicate that the resolved contribution arises from a
significant charm component in the photon. A massive charm NLO parton level
calculation yields lower cross sections compared to the measured results in a
kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure
Measurement of Jet Shapes in Photoproduction at HERA
The shape of jets produced in quasi-real photon-proton collisions at
centre-of-mass energies in the range GeV has been measured using the
hadronic energy flow. The measurement was done with the ZEUS detector at HERA.
Jets are identified using a cone algorithm in the plane with a
cone radius of one unit. Measured jet shapes both in inclusive jet and dijet
production with transverse energies GeV are presented. The jet
shape broadens as the jet pseudorapidity () increases and narrows
as increases. In dijet photoproduction, the jet shapes have been
measured separately for samples dominated by resolved and by direct processes.
Leading-logarithm parton-shower Monte Carlo calculations of resolved and direct
processes describe well the measured jet shapes except for the inclusive
production of jets with high and low . The observed
broadening of the jet shape as increases is consistent with the
predicted increase in the fraction of final state gluon jets.Comment: 29 pages including 9 figure
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