4,714 research outputs found
Discreteness without symmetry breaking: a theorem
This paper concerns sprinklings into Minkowski space (Poisson processes). It
proves that there exists no equivariant measurable map from sprinklings to
spacetime directions (even locally). Therefore, if a discrete structure is
associated to a sprinkling in an intrinsic manner, then the structure will not
pick out a preferred frame, locally or globally. This implies that the
discreteness of a sprinkled causal set will not give rise to ``Lorentz
breaking'' effects like modified dispersion relations. Another consequence is
that there is no way to associate a finite-valency graph to a sprinkling
consistently with Lorentz invariance.Comment: 7 pages, laTe
Discreteness and the transmission of light from distant sources
We model the classical transmission of a massless scalar field from a source
to a detector on a background causal set. The predictions do not differ
significantly from those of the continuum. Thus, introducing an intrinsic
inexactitude to lengths and durations - or more specifically, replacing the
Lorentzian manifold with an underlying discrete structure - need not disrupt
the usual dynamics of propagation.Comment: 16 pages, 1 figure. Version 2: reference adde
Long-term polarization observations of Mira variable stars suggest asymmetric structures
Mira and semi-regular variable stars have been studied for centuries but
continue to be enigmatic. One unsolved mystery is the presence of polarization
from these stars. In particular, we present 40 years of polarization
measurements for the prototype o Ceti and V CVn and find very different
phenomena for each star. The polarization fraction and position angle for Mira
is found to be small and highly variable. On the other hand, the polarization
fraction for V CVn is large and variable, from 2 - 7 %, and its position angle
is approximately constant, suggesting a long-term asymmetric structure. We
suggest a number of potential scenarios to explain these observations.Comment: 2 pages, 1 figure, poster presented at IAU Symposium 301, Precision
Asteroseismology, August 2013, Wroclaw, Polan
Gravity and Matter in Causal Set Theory
The goal of this paper is to propose an approach to the formulation of
dynamics for causal sets and coupled matter fields. We start from the continuum
version of the action for a Klein-Gordon field coupled to gravity, and rewrite
it first using quantities that have a direct correspondent in the case of a
causal set, namely volumes, causal relations, and timelike lengths, as
variables to describe the geometry. In this step, the local Lagrangian density
for a set of fields is recast into a quasilocal expression
that depends on pairs of causally related points and
is a function of the values of in the Alexandrov set defined by those
points, and whose limit as and approach a common point is .
We then describe how to discretize , and use it to define a
discrete action.Comment: 13 pages, no figures; In version 2, friendlier results than in
version 1 are obtained following much shorter derivation
Effect of Adult Attachment on the Resiliency of Youth in Behavior Disordered Classrooms
The purpose of this study was to investigate the effect that adult attachment has on the resiliency of at-risk youth . The Inventory of Parent and Peer Attachment was revised to measure the degree of attachment to a significant adult and was administered along with the Children\u27 s Resiliency Attitudes Scale to students in behavior disordered classrooms (n = 41). The assessments were given during one class period in six behavior disordered classrooms at one school. The results found that those students who feel strong attachments to at least one adult were also more resilient and able to deal with adversity. These findings emphasized the importance of involving adults from various facets of life and the community in the development of community and school based youth programs
Age of second language acquisition affects nonverbal conflict processing in children : an fMRI study
Background: In their daily communication, bilinguals switch between two languages, a process that involves the selection of a target language and minimization of interference from a nontarget language. Previous studies have uncovered the neural structure in bilinguals and the activation patterns associated with performing verbal conflict tasks. One question that remains, however is whether this extra verbal switching affects brain function during nonverbal conflict tasks.
Methods: In this study, we have used fMRI to investigate the impact of bilingualism in children performing two nonverbal tasks involving stimulus-stimulus and stimulus-response conflicts. Three groups of 8-11-year-old children - bilinguals from birth (2L1), second language learners (L2L), and a control group of monolinguals (1L1) - were scanned while performing a color Simon and a numerical Stroop task. Reaction times and accuracy were logged.
Results: Compared to monolingual controls, bilingual children showed higher behavioral congruency effect of these tasks, which is matched by the recruitment of brain regions that are generally used in general cognitive control, language processing or to solve language conflict situations in bilinguals (caudate nucleus, posterior cingulate gyrus, STG, precuneus). Further, the activation of these areas was found to be higher in 2L1 compared to L2L.
Conclusion: The coupling of longer reaction times to the recruitment of extra language-related brain areas supports the hypothesis that when dealing with language conflicts the specialization of bilinguals hampers the way they can process with nonverbal conflicts, at least at early stages in life
- …