312 research outputs found
A note on applying the BCH method under linear equality and inequality constraints
Researchers often wish to relate estimated scores on latent variables to exogenous covariates not previously used in analyses. The BCH method corrects for asymptotic bias in estimates due to these scores’ uncertainty and has been shown to be relatively robust. When applying the BCH approach however, two problems arise. First, negative cell proportions can be obtained. Second, the approach cannot deal with situations where marginals need to be fixed to specific values, such as edit restrictions. The BCH approach can handle these problems when placed in a framework of quadratic loss functions and linear equality and inequality constraints. This research note gives the explicit form for equality constraints and demonstrates how solutions for inequality constraints may be obtained using numerical methods
Supernova Muons: New Constraints on Z' Bosons, Axions, and ALPs
New light particles produced in supernovae can lead to additional energy loss
and a consequent deficit in neutrino production in conflict with the neutrinos
observed from Supernova 1987A (SN1987A). Contrary to the majority of previous
SN1987A studies, we examine the impact of bosons, axions, and axion-like
particles (ALPs) interacting with the muons produced in SN1987A. For the first
time, we find constraints on generic bosons coupled to muons, and apply
our results to particle models including gauged number,
, and gauged number, . We constrain
bosons with masses up to about 250-500 MeV, and down to about in
-muon coupling. We also extend previous work on axion-muon couplings by
examining the importance of loop-level interactions, as well as performing
calculations over a wider range of axion masses. We constrain muon-coupled
axions from arbitrarily low masses up to about 200-500 MeV, with bounds
extending down to axion-muon couplings of approximately GeV.
We conclude that supernovae broadly provide a sensitive probe of new
lightly-coupled particles interacting with muons.Comment: 29 pages, several hot pink figures. v2: figs 7 and 8 updated,
references adde
Model discrimination in gravitational wave spectra from dark phase transitions
In anticipation of upcoming gravitational wave experiments, we provide a comprehensive overview of the spectra predicted by phase transitions triggered by states from a large variety of dark sector models. Such spectra are functions of the quantum numbers and (self-) couplings of the scalar that triggers the dark phase transition. We classify dark sectors that give rise to a first order phase transition and perform a numerical scan over the thermal parameter space. We then characterize scenarios in which a measurement of a new source of gravitational waves could allow us to discriminate between models with differing particle content
Towards Contextual Action Recognition and Target Localization with Active Allocation of Attention
Exploratory gaze movements are fundamental for gathering the most relevant information regarding the partner during social interactions. We have designed and implemented a system for dynamic attention allocation which is able to actively control gaze movements during a visual action recognition task. During the observation of a partners reaching movement, the robot is able to contextually estimate the goal position of the partner hand and the location in space of the candidate targets, while moving its gaze around with the purpose of optimizing the gathering of information relevant for the task. Experimental results on a simulated environment show that active gaze control provides a relevant advantage with respect to typical passive observation, both in term of estimation precision and of time required for action recognition. © 2012 Springer-Verlag
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