401 research outputs found
Holographic quenches with a gap
In order to holographically model quenches with a gapped final hamiltonian, we consider a gravity-scalar theory in anti-de Sitter space with an infrared hard wall. We allow a time dependent profile for the scalar field at the wall. This induces an energy exchange between bulk and wall and generates an oscillating scalar pulse. We argue that such backgrounds are the counterpart of quantum revivals in the dual field theory. We perform a qualitative comparison with the quench dynamics of the massive Schwinger model, which has been recently analyzed using tensor network techniques. Agreement is found provided the width of the oscillating scalar pulse is inversely linked to the energy density communicated by the quench. We propose this to be a general feature of holographic quenches.The work of E.daS. is nanced by the spanish
grant BES-2013-063972. E.L. has been supported by the spanish grant FPA2012-32828 and
SEV-2012-0249 of the Centro de Excelencia Severo Ochoa Programme. The work of J.M.
is supported in part by the spanish grant FPA2011-22594, by Xunta de Galicia (GRC2013-
024), by the Consolider-CPAN (CSD2007-00042), and by FEDER. A.S. is supported by
the European Research Council grant HotLHC ERC-2011-StG-279579 and by Xunta de
Galicia (Conselleria de Educaci on). Part of the numerical calculations were performed at
the Centro de Supercomputaci on de Galicia (CESGA).S
Non-autonomous stochastic evolution equations and applications to stochastic partial differential equations
In this paper we study the following non-autonomous stochastic evolution
equation on a UMD Banach space with type 2,
{equation}\label{eq:SEab}\tag{SE} {{aligned} dU(t) & = (A(t)U(t) + F(t,U(t)))
dt + B(t,U(t)) dW_H(t), \quad t\in [0,T],
U(0) & = u_0. {aligned}. {equation}
Here are unbounded operators with domains
which may be time dependent. We assume that
satisfies the conditions of Acquistapace and Terreni. The
functions and are nonlinear functions defined on certain interpolation
spaces and is the initial value. is a cylindrical Brownian
motion on a separable Hilbert space .
Under Lipschitz and linear growth conditions we show that there exists a
unique mild solution of \eqref{eq:SEab}. Under assumptions on the interpolation
spaces we extend the factorization method of Da Prato, Kwapie\'n, and Zabczyk,
to obtain space-time regularity results for the solution of
\eqref{eq:SEab}. For Hilbert spaces we obtain a maximal regularity result.
The results improve several previous results from the literature.
The theory is applied to a second order stochastic partial differential
equation which has been studied by Sanz-Sol\'e and Vuillermot. This leads to
several improvements of their result.Comment: Accepted for publication in Journal of Evolution Equation
Shared Mandates, Moral Hazard, and Political (Mis)alignment in a Decentralized Economy
Prediction of lethal and synthetically lethal knock-outs in regulatory networks
The complex interactions involved in regulation of a cell's function are
captured by its interaction graph. More often than not, detailed knowledge
about enhancing or suppressive regulatory influences and cooperative effects is
lacking and merely the presence or absence of directed interactions is known.
Here we investigate to which extent such reduced information allows to forecast
the effect of a knock-out or a combination of knock-outs. Specifically we ask
in how far the lethality of eliminating nodes may be predicted by their network
centrality, such as degree and betweenness, without knowing the function of the
system. The function is taken as the ability to reproduce a fixed point under a
discrete Boolean dynamics. We investigate two types of stochastically generated
networks: fully random networks and structures grown with a mechanism of node
duplication and subsequent divergence of interactions. On all networks we find
that the out-degree is a good predictor of the lethality of a single node
knock-out. For knock-outs of node pairs, the fraction of successors shared
between the two knocked-out nodes (out-overlap) is a good predictor of
synthetic lethality. Out-degree and out-overlap are locally defined and
computationally simple centrality measures that provide a predictive power
close to the optimal predictor.Comment: published version, 10 pages, 6 figures, 2 tables; supplement at
http://www.bioinf.uni-leipzig.de/publications/supplements/11-01
Numerical Schemes for Rough Parabolic Equations
This paper is devoted to the study of numerical approximation schemes for a
class of parabolic equations on (0, 1) perturbed by a non-linear rough signal.
It is the continuation of [8, 7], where the existence and uniqueness of a
solution has been established. The approach combines rough paths methods with
standard considerations on discretizing stochastic PDEs. The results apply to a
geometric 2-rough path, which covers the case of the multidimensional
fractional Brownian motion with Hurst index H \textgreater{} 1/3.Comment: Applied Mathematics and Optimization, 201
日韓自動車産業の中国展開
Rate limitation due to encounters is fundamental to many ecological
interactions. Since encounter rate governs reaction rates, and thus,
dynamics of systems, it deserves systematic study. In classical
population biology, ecological dynamics rely on the assumption of
perfectly mixed interacting entities (e.g., individuals, populations,
etc.) in a spaceless world. The so-called mean field assumption
assumes that encounter rates are driven exclusively by changes in the
density of the interacting entities and not on how they are
distributed or move in space. Therefore, the mean field assumption
does not give any insight into relevant spatiotemporal statistical
properties produced by the trajectories of moving entities through
space. In the present study, we develop spatially explicit
simulations of random walking particles (i.e., Lévy walkers) to
evaluate encounter rate constraints beyond the mean field
assumption. We show that encounter rate fluctuations are driven not
only by physical aspects such as the size or the velocity of the
interacting particles, but also by different motion patterns. In
particular, superdiffusion phenomena might be relevant at low
densities and/or low spatial dimensionality. Finally, we discuss
potential adaptive responses of living organisms that may allow
individuals to control how they diffuse through space and/or the
spatial dimensions employed in the exploration process
O papel da investigação na prática pedagógica dos mestrados em ensino
Os mestrados em ensino da Universidade do Minho preveem a formação do professor/ educador como prático reflexivo e intelectual crítico, conferindo um lugar de relevo à investigação pedagógica no estágio através da construção e avaliação de um “projeto de intervenção pedagógica supervisionada” que deve enquadrar-se numa visão democrática da educação. O projeto dá origem a um relatório final, defendido em provas públicas.
Com o objetivo de compreender o papel da investigação no estágio, foi analisado um corpus de 28 relatórios de 5 mestrados de diversos níveis de ensino, com base numa grelha incidente na visão de educação subjacente aos projetos, no tipo e função do conhecimento mobilizado, na articulação investigação-ensino e no valor educativo das intervenções.
Os projetos evidenciam a importância da investigação no desenvolvimento de práticas educativas focadas na qualidade dos processos de ensino e de aprendizagem, embora a coexistência de diferentes modalidades de articulação investigação-ensino sinalize conceções diferenciadas de formação e da função da investigação na regulação das práticas e na (re)construção de competências profissionais. A partir das potencialidades e limitações observadas, traçam-se linhas de ação futura para a construção de uma cultura investigativa na formação inicial de professores/ educadores
The U-shaped relationship between parental age and the risk of bipolar disorder in the offspring: A systematic review and meta-analysis
Parenthood age may affect the risk for the development of different psychiatric disorders in the offspring, including bipolar disorder (BD). The present systematic review and meta-analysis aimed to appraise the relationship between paternal age and risk for BD and to explore the eventual relationship between paternal age and age at onset of BD. We searched the MEDLINE, Scopus, Embase, PsycINFO online databases for original studies from inception, up to December 2021. Random-effects meta-analyses were conducted. Sixteen studies participated in the qualitative synthesis, of which k = 14 fetched quantitative data encompassing a total of 13,424,760 participants and 217,089 individuals with BD. Both fathers [adjusted for the age of other parent and socioeconomic status odd ratio - OR = 1.29(95%C.I. = 1.13-1.48)] and mothers aged ≤ 20 years [(OR = 1.23(95%C.I. = 1.14-1.33)] had consistently increased odds of BD diagnosis in their offspring compared to parents aged 25-29 years. Fathers aged ≥ 45 years [adjusted OR = 1.29 (95%C.I. = 1.15-1.46)] and mothers aged 35-39 years [OR = 1.10(95%C.I. = 1.01-1.19)] and 40 years or older [OR = 1.2(95% C.I. = 1.02-1.40)] likewise had inflated odds of BD diagnosis in their offspring compared to parents aged 25-29 years. Early and delayed parenthood are associated with an increased risk of BD in the offspring. Mechanisms underlying this association are largely unknown and may involve a complex interplay between psychosocial, genetic and biological factors, and with different impacts according to sex and age range. Evidence on the association between parental age and illness onset is still tentative but it points towards a possible specific effect of advanced paternal age on early BD-onset
Environmental Metal Pollution Considered as Noise: Effects on the Spatial Distribution of Benthic Foraminifera in two Coastal Marine Areas of Sicily (Southern Italy)
We analyze the spatial distributions of two groups of benthic foraminifera
(Adelosina spp. + Quinqueloculina spp. and Elphidium spp.), along Sicilian
coast, and their correlation with six different heavy metals, responsible for
the pollution. Samples were collected inside the Gulf of Palermo, which has a
high level of pollution due to heavy metals, and along the coast of Lampedusa
island (Sicily Channel, Southern Mediterranean), which is characterized by
unpolluted sea waters. Because of the environmental pollution we find: (i) an
anticorrelated spatial behaviour between the two groups of benthic foraminifera
analyzed; (ii) an anticorrelated (correlated) spatial behaviour between the
first (second) group of benthic foraminifera with metal concentrations; (iii)
an almost uncorrelated spatial behaviour between low concentrations of metals
and the first group of foraminifera in clean sea water sites. We introduce a
two-species model based on the generalized Lotka-Volterra equations in the
presence of a multiplicative noise, which models the interaction between
species and environmental pollution due to the presence in top-soft sediments
of heavy metals. The interaction coefficients between the two species are kept
constant with values in the coexistence regime. Using proper values for the
initial conditions and the model parameters, we find for the two species a
theoretical spatial distribution behaviour in a good agreement with the data
obtained from the 63 sites analyzed in our study.Comment: 28 pages, 8 figures, 5 table
Temporal Networks
A great variety of systems in nature, society and technology -- from the web
of sexual contacts to the Internet, from the nervous system to power grids --
can be modeled as graphs of vertices coupled by edges. The network structure,
describing how the graph is wired, helps us understand, predict and optimize
the behavior of dynamical systems. In many cases, however, the edges are not
continuously active. As an example, in networks of communication via email,
text messages, or phone calls, edges represent sequences of instantaneous or
practically instantaneous contacts. In some cases, edges are active for
non-negligible periods of time: e.g., the proximity patterns of inpatients at
hospitals can be represented by a graph where an edge between two individuals
is on throughout the time they are at the same ward. Like network topology, the
temporal structure of edge activations can affect dynamics of systems
interacting through the network, from disease contagion on the network of
patients to information diffusion over an e-mail network. In this review, we
present the emergent field of temporal networks, and discuss methods for
analyzing topological and temporal structure and models for elucidating their
relation to the behavior of dynamical systems. In the light of traditional
network theory, one can see this framework as moving the information of when
things happen from the dynamical system on the network, to the network itself.
Since fundamental properties, such as the transitivity of edges, do not
necessarily hold in temporal networks, many of these methods need to be quite
different from those for static networks
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