5,458 research outputs found
Five dimensional formulation of a DSR
In this paper, we analyze a possible formalization of the deformed special
relativity as a five-dimensional theory. This is not the first attempt to do
so, but we feel that either these previous treatments are too arbitrary in the
choice of the new enlarged space, or they lack a satisfactory physical
interpretation. In this work, we propose an algorithm which fixes the shape of
the enlarged space. Afterwards, we focus our attention on the consequences of
our formalism, proposing a physical interpretation.Comment: 19 pages, no figures, minor change
Pre-saccadic perception: separate time courses for enhancement and spatial pooling at the saccade target
We interact with complex scenes using eye movements to select targets of interest. Studies have shown that the future target of a saccadic eye movement is processed differently by the visual system. A number of effects have been reported, including a benefit for perceptual performance at the target (âenhancementâ), reduced influences of backward masking (âunmaskingâ), reduced crowding (âun-crowdingâ) and spatial compression towards the saccade target. We investigated the time course of these effects by measuring orientation discrimination for targets that were spatially crowded or temporally masked. In four experiments, we varied the target-flanker distance, the presence of forward/backward masks, the orientation of the flankers and whether participants made a saccade. Masking and randomizing flanker orientation reduced performance in both fixation and saccade trials. We found a small improvement in performance on saccade trials, compared to fixation trials, with a time course that was consistent with a general enhancement at the saccade target. In addition, a decrement in performance (reporting the average flanker orientation, rather than the target) was found in the time bins nearest saccade onset when random oriented flankers were used, consistent with spatial pooling around the saccade target. We did not find strong evidence for un-crowding. Overall, our pattern of results was consistent with both an early, general enhancement at the saccade target and a later, peri-saccadic compression/pooling towards the saccade target
Heavy quark radiation in NLO+PS POWHEG generators
In this paper we deal with radiation from heavy quarks in the context of
next-to-leading order calculations matched to parton shower generators. A new
algorithm for radiation from massive quarks is presented that has considerable
advantages over the one previously employed. We implement the algorithm in the
framework of the , and compare it with the previous one in
the case of the generator for bottom production in hadronic
collisions, and in the case of the generator for top production
and decay.Comment: 14 pages, 13 figures, LaTe
Towards Dead Time Inclusion in Neuronal Modeling
A mathematical description of the refractoriness period in neuronal diffusion
modeling is given and its moments are explicitly obtained in a form that is
suitable for quantitative evaluations. Then, for the Wiener, Ornstein-Uhlenbeck
and Feller neuronal models, an analysis of the features exhibited by the mean
and variance of the first passage time and of refractoriness period is
performed.Comment: 12 pages, 1 figur
A cluster driven log-volatility factor model: a deepening on the source of the volatility clustering
We introduce a new factor model for log volatilities that performs
dimensionality reduction and considers contributions globally through the
market, and locally through cluster structure and their interactions. We do not
assume a-priori the number of clusters in the data, instead using the Directed
Bubble Hierarchical Tree (DBHT) algorithm to fix the number of factors. We use
the factor model and a new integrated non parametric proxy to study how
volatilities contribute to volatility clustering. Globally, only the market
contributes to the volatility clustering. Locally for some clusters, the
cluster itself contributes statistically to volatility clustering. This is
significantly advantageous over other factor models, since the factors can be
chosen statistically, whilst also keeping economically relevant factors.
Finally, we show that the log volatility factor model explains a similar amount
of memory to a Principal Components Analysis (PCA) factor model and an
exploratory factor model
- âŠ