1,589 research outputs found
Renormalization and blow up for charge one equivariant critical wave maps
We prove the existence of equivariant finite time blow up solutions for the
wave map problem from 2+1 dimensions into the 2-sphere. These solutions are the
sum of a dynamically rescaled ground-state harmonic map plus a radiation term.
The local energy of the latter tends to zero as time approaches blow up time.
This is accomplished by first "renormalizing" the rescaled ground state
harmonic map profile by solving an elliptic equation, followed by a
perturbative analysis
Memetic Multilevel Hypergraph Partitioning
Hypergraph partitioning has a wide range of important applications such as
VLSI design or scientific computing. With focus on solution quality, we develop
the first multilevel memetic algorithm to tackle the problem. Key components of
our contribution are new effective multilevel recombination and mutation
operations that provide a large amount of diversity. We perform a wide range of
experiments on a benchmark set containing instances from application areas such
VLSI, SAT solving, social networks, and scientific computing. Compared to the
state-of-the-art hypergraph partitioning tools hMetis, PaToH, and KaHyPar, our
new algorithm computes the best result on almost all instances
H\"older Continuity of the Integrated Density of States for the Fibonacci Hamiltonian
We prove H\"older continuity of the integrated density of states for the
Fibonacci Hamiltonian for any positive coupling, and obtain the asymptotics of
the H\"older exponents for large and small couplings.Comment: 18 page
Imitation in Large Games
In games with a large number of players where players may have overlapping
objectives, the analysis of stable outcomes typically depends on player types.
A special case is when a large part of the player population consists of
imitation types: that of players who imitate choice of other (optimizing)
types. Game theorists typically study the evolution of such games in dynamical
systems with imitation rules. In the setting of games of infinite duration on
finite graphs with preference orderings on outcomes for player types, we
explore the possibility of imitation as a viable strategy. In our setup, the
optimising players play bounded memory strategies and the imitators play
according to specifications given by automata. We present algorithmic results
on the eventual survival of types
The value of real world evidence: the case of medical cannabis
Randomised controlled trials (RCTs) have long been considered the gold standard of medical evidence. In relation to cannabis based medicinal products (CBMPs), this focus on RCTs has led to very restrictive guidelines in the UK, which are limiting patient access. There is general agreement that RCT evidence in relation to CBPMs is insufficient at present. As well as commercial reasons, a major problem is that RCTs do not lend themselves well to the study of whole plant medicines. One solution to this challenge is the use of real world evidence (RWE) with patient reported outcomes (PROs) to widen the evidence base. Such data increasingly highlights the positive impact medical cannabis can have on patients’ lives. This paper outlines the value of this approach which involves the study of interventions and patients longitudinally under medical care. In relation to CBMPs, RWE has a broad range of advantages. These include the study of larger groups of patients, the use of a broader range and ratio of components of CBMPs, and the inclusion of more and rarer medical conditions. Importantly, and in contrast to RCTs, patients with significant comorbidities–and from a wider demographic profile–can also be studied, so providing higher ecological validity and increasing patient numbers, whilst offering significant cost savings. We conclude by outlining 12 key recommendations of the value of RWE in relation to medical cannabis. We hope that this paper will help policymakers and prescribers understand the importance of RWE in relation to medical cannabis and help them develop approaches to overcome the current situation which is detrimental to patients
On the Dynamics of solitons in the nonlinear Schroedinger equation
We study the behavior of the soliton solutions of the equation
i((\partial{\psi})/(\partialt))=-(1/(2m)){\Delta}{\psi}+(1/2)W_{{\epsilon}}'({\psi})+V(x){\psi}
where W_{{\epsilon}}' is a suitable nonlinear term which is singular for
{\epsilon}=0. We use the "strong" nonlinearity to obtain results on existence,
shape, stability and dynamics of the soliton. The main result of this paper
(Theorem 1) shows that for {\epsilon}\to0 the orbit of our soliton approaches
the orbit of a classical particle in a potential V(x).Comment: 29 page
Spectral Analysis for Matrix Hamiltonian Operators
In this work, we study the spectral properties of matrix Hamiltonians
generated by linearizing the nonlinear Schr\"odinger equation about soliton
solutions. By a numerically assisted proof, we show that there are no embedded
eigenvalues for the three dimensional cubic equation. Though we focus on a
proof of the 3d cubic problem, this work presents a new algorithm for verifying
certain spectral properties needed to study soliton stability. Source code for
verification of our comptuations, and for further experimentation, are
available at http://www.math.toronto.edu/simpson/files/spec_prop_code.tgz.Comment: 57 pages, 22 figures, typos fixe
Evolution of the complex refractive index in the UV spectral region in ageing secondary organic aerosol
The chemical and physical properties of secondary organic aerosol (SOA)
formed by the photochemical degradation of biogenic and anthropogenic
volatile organic compounds (VOC) are as yet still poorly constrained. The evolution
of the complex refractive index (RI) of SOA, formed from purely biogenic VOC
and mixtures of biogenic and anthropogenic VOC, was studied over a diurnal
cycle in the SAPHIR photochemical outdoor chamber in Jülich, Germany.
The correlation of RI with SOA chemical and physical properties such as
oxidation level and volatility was examined. The RI was retrieved by a newly
developed broadband cavity-enhanced spectrometer for aerosol optical
extinction measurements in the UV spectral region (360 to 420 nm). Chemical
composition and volatility of the particles were monitored by a high-resolution time-of-flight aerosol mass spectrometer, and a volatility tandem
differential mobility analyzer. SOA was formed by ozonolysis of either (i) a
mixture of biogenic VOC (α-pinene and limonene), (ii) biogenic VOC
mixture with subsequent addition of an anthropogenic VOC
(<i>p</i>-xylene-d<sub>10</sub>), or (iii) a mixture of biogenic and anthropogenic VOC.
The SOA aged by ozone/OH reactions up to 29.5 h was found to be
non-absorbing in all cases. The SOA with <i>p</i>-xylene-d<sub>10</sub> showed an
increase of the scattering component of the RI correlated with an increase
of the O / C ratio and with an increase in the SOA density. There was a
greater increase in the scattering component of the RI when the SOA was
produced from the mixture of biogenic VOCs and anthropogenic VOC than from
the sequential addition of the VOCs after approximately the same ageing time.
The increase of the scattering component was inversely correlated with the
SOA volatility. Two RI retrievals determined for the pure biogenic SOA
showed a constant RI for up to 5 h of ageing. Mass spectral characterization
shows the three types of the SOA formed in this study have a significant
amount of semivolatile components. The influence of anthropogenic VOCs on
the oxygenated organic aerosol as well as the atmospheric implications are
discussed
Structural models of genome-wide covariance identify multiple common dimensions in autism
Common genetic variation has been associated with multiple symptoms in Autism Spectrum Disorder (ASD). However, our knowledge of shared genetic factor structures contributing to this highly heterogeneous neurodevelopmental condition is limited. Here, we developed a structural equation modelling framework to directly model genome-wide covariance across core and non-core ASD phenotypes, studying autistic individuals of European descent using a case-only design. We identified three independent genetic factors most strongly linked to language/cognition, behaviour and motor development, respectively, when studying a population-representative sample (N=5,331). These analyses revealed novel associations. For example, developmental delay in acquiring personal-social skills was inversely related to language, while developmental motor delay was linked to self-injurious behaviour. We largely confirmed the three-factorial structure in independent ASD-simplex families (N=1,946), but uncovered simplex-specific genetic overlap between behaviour and language phenotypes. Thus, the common genetic architecture in ASD is multi-dimensional and contributes, in combination with ascertainment-specific patterns, to phenotypic heterogeneity
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Biases in the perceived timing of perisaccadic perceptual and motor events
Subjects typically experience the temporal interval immediately following a saccade as longer than a comparable control interval. One explanation of this effect is that the brain antedates the perceptual onset of a saccade target to around the time of saccade initiation. This could explain the apparent continuity of visual perception across eye movements. Thisantedating account was tested in three experiments in which subjects made saccades of differing extents and then judged either the duration or the temporal order of key events. Postsaccadic stimuli underwent subjective temporal lengthening and had early perceived onsets. A temporally advanced awareness of saccade completion was also found, independently of antedating effects. These results provide convergent evidence supporting antedating and differentiating it from other temporal biases
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