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Search Results: 1 - 10 of 4651 matches for " Oliver Butterley "
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Area expanding C^{1+α} Suspension Semiflows
Oliver Butterley
Mathematics , 2012, DOI: 10.1007/s00220-013-1835-6
Abstract: We study a large class of suspension semiflows which contains the Lorenz semiflows. This is a class with low regularity (merely C^{1+\alpha}) and where the return map is discontinuous and the return time is unbounded. We establish the functional analytic framework which is typically employed to study rates of mixing. The Laplace transform of the correlation function is shown to admit a meromorphic extension to a strip about he imaginary axis. As part of this argument we give a new result concerning the quasi-compactness of weighted transfer operators for piecewise C^{1+\alpha} expanding interval maps.
A Note on Operator Semigroups Associated to Chaotic Flows
Oliver Butterley
Mathematics , 2014, DOI: 10.1017/etds.2014.127
Abstract: The transfer operator associated to a flow (continuous time dynamical system) is a one-parameter operator semigroup. We consider the operator-valued Laplace transform of this one-parameter semigroup. Estimates on the Laplace transform have be used in various settings in order to show the rate at which the flow mixes. Here we consider the case of exponential mixing or rapid mixing (super polynomial). We develop the operator theory framework amenable to this setting and show that the same estimates may be used to produce results, in terms of the operators, which go beyond the results for the rate of mixing. Such results are useful for obtaining other statistical properties of the dynamical system.
An Alternative Approach to Generalised BV and the Application to Expanding Interval Maps
Oliver Butterley
Mathematics , 2012,
Abstract: We introduce a family of Banach spaces of measures, each containing the set of measures with density of bounded variation. These spaces are suitable for the study of weighted transfer operators of piecewise-smooth maps of the interval where the weighting used in the transfer operator is not better than piecewise H\"older continuous and the partition on which the map is continuous may possess a countable number of elements. For such weighted transfer operators we give upper bounds for both the spectral radius and for the essential spectral radius.
Expanding Semiflows on Branched Surfaces and One-Parameter Semigroups of Operators
Oliver Butterley
Mathematics , 2012, DOI: 10.1088/0951-7715/25/12/3487
Abstract: We consider expanding semiflows on branched surfaces. The family of transfer operators associated to the semiflow is a one-parameter semigroup of operators. The transfer operators may also be viewed as an operator-valued function of time and so, in the appropriate norm, we may consider the vector-valued Laplace transform of this function. We obtain a spectral result on these operators and relate this to the spectrum of the generator of this semigroup. Issues of strong continuity of the semigroup are avoided. The main result is the improvement to the machinery associated with studying semiflows as one-parameter semigroups of operators and the study of the smoothness properties of semiflows defined on branched manifolds, without encoding as a suspension semiflow.
Robustly invariant sets in fibre contracting bundle flows
Oliver Butterley,Carlangelo Liverani
Mathematics , 2012,
Abstract: We provide abstract conditions which imply the existence of a robustly invariant neighbourhood of a global section of a fibre bundle flow. We then apply such a result to the bundle flow generated by an Anosov flow when the fibre is the space of jets (which are described by local manifolds). As a consequence we obtain sets of manifolds (e.g. approximations of stable manifolds) that are left invariant, {\bf for all} negative times, by the flow and its small perturbations. Finally, we show that the latter result can be used to easily fix a mistake recently uncovered in the paper {\em Smooth Anosov flows: correlation spectra and stability}, \cite{BuL}, by the present authors.
Exponential Mixing for Skew Products with Discontinuities
Oliver Butterley,Peyman Eslami
Mathematics , 2014,
Abstract: We consider the skew product $F: (x,u) \mapsto (f(x), u + \tau(x))$, where the base map $f : \mathbb{T}^{1} \to \mathbb{T}^{1}$ is piecewise $\mathcal{C}^{2}$, covering and uniformly expanding, and the fibre map $\tau : \mathbb{T}^{1} \to \mathbb{R}$ is piecewise $\mathcal{C}^{2}$. We show the dichotomy that either this system mixes exponentially or $\tau$ is cohomologous (via a Lipschitz function) to a piecewise constant.
Disintegration of Invariant Measures for Hyperbolic Skew Products
Oliver Butterley,Ian Melbourne
Mathematics , 2015,
Abstract: We study hyperbolic skew products and the disintegration of the SRB measure into measures supported on local stable manifolds. Such a disintegration gives a method for passing from an observable $v$ on the skew product to an observable $\bar v$ on the system quotiented along stable manifolds. Under mild assumptions on the system we prove that the disintegration preserves the smoothness of $v$, firstly in the case where $v$ is H\"older and secondly in the case where $v$ is $\mathcal{C}^{1}$.
Open sets of Axiom A flows with Exponentially Mixing Attractors
Vítor Araújo,Oliver Butterley,Paulo Varandas
Mathematics , 2014,
Abstract: For any dimension $d\geq 3$ we construct $C^{1}$-open subsets of the space of $C^{3}$ vector fields such that the flow associated to each vector field is Axiom A and exhibits a non-trivial attractor which mixes exponentially with respect to the unique SRB measure.
Numerical evidence for the maximum number of mutually unbiased bases in dimension six
Paul Butterley,William Hall
Physics , 2007, DOI: 10.1016/j.physleta.2007.04.059
Abstract: The question of determining the maximal number of mutually unbiased bases in dimension six has received much attention since their introduction to quantum information theory, but a definitive answer has still not been found. In this paper we move away from the traditional analytic approach and use a numerical approach to attempt to determine this number. We numerically minimise a non-negative function of a set of N+1 orthonormal bases in dimension d which only evaluates to zero if the bases are mutually unbiased. As a result we find strong evidence that (as has been conjectured elsewhere) there are no more than three mutually unbiased bases in dimension six.
Considerations for EAGLE from Monte-Carlo adaptive optics simulation
Alastair Basden,Timothy Butterley,Richard Myers
Physics , 2010,
Abstract: The EAGLE instrument for the E-ELT is a multi-IFU spectrograph, that uses a MOAO system for wavefront correction of interesting lines of sight. We present a Monte-Carlo AO simulation package that has been used to model the performace of EAGLE, and provide results, including comparisons with an analytical code. These results include an investigation of the performance of compressed reconstructor representations that have the potential to significantly reduce the complexity of a real-time control system when implemented.
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