Mon, 08 Oct 2018

15:45 - 16:45
L3

Fine properties of fractional Brownian motions on Wiener space

JIAWEI LI
(University of Oxford)
Abstract

We study several important fine properties for the family of fractional Brownian motions with Hurst parameter H under the (p,r)-capacity on classical Wiener space introduced by Malliavin. We regard fractional Brownian motions as Wiener functionals via the integral representation discovered by Decreusefond and \"{U}st\"{u}nel, and show non differentiability, modulus of continuity, law of iterated Logarithm(LIL) and self-avoiding properties of fractional Brownian motion sample paths using Malliavin calculus as well as the tools developed in the previous work by Fukushima, Takeda and etc. for Brownian motion case.

 

Mon, 08 Oct 2018

14:15 - 15:15
L3

On smile properties of volatility derivatives and exotic products: understanding the VIX skew

ELISA ALOS ALCALDE
(Universitat Pompeu Fabra)
Abstract

We develop a method to study the implied volatility for exotic options and volatility derivatives with European payoffs such as VIX options. Our approach, based on Malliavin calculus techniques, allows us to describe the properties of the at-the-money implied volatility (ATMI) in terms of the Malliavin derivatives of the underlying process. More precisely, we study the short-time behaviour of the ATMI level and skew. As an application, we describe the short-term behavior of the ATMI of VIX and realized variance options in terms of the Hurst parameter of the model, and most importantly we describe the class of volatility processes that generate a positive skew for the VIX implied volatility. In addition, we find that our ATMI asymptotic formulae perform very well even for large maturities. Several numerical examples are provided to support our theoretical results.  

Pathogenic stromal cells as therapeutic targets in joint inflammation
Dakin, S Coles, M Sherlock, J Powrie, F Carr, A Buckley, C Nature Reviews Rheumatology volume 14 issue 11 714-726 (12 Nov 2018)
Thu, 08 Nov 2018

16:00 - 17:30
L3

(Marta) Models for Thin Prestrained Structures & (Shankar) On discrete leaves, flowers, and sea-slugs.

Marta Lewicka & Shankar Venkataramani
(University of Pittsburgh & University of Arizona)
Abstract

(Marta Lewicka)

Variational methods have been extensively used in the past decades to rigorously derive nonlinear models in the description of thin elastic films. In this context, natural growth or differential swelling-shrinking lead to models where an elastic body aims at reaching a space-dependent metric. We will describe the effect of such, generically incompatible, prestrain metrics on the singular limits' bidimensional models. We will discuss metrics that vary across the specimen in both the midplate and the thin (transversal) directions. We will also cover the case of the oscillatory prestrain, exhibit its relation to the non-oscillatory case via identifying the effective metrics, and discuss the role of the Riemann curvature tensor in the limiting models.

 

(Shankar Venkataramani)

Using the bidimensional models for pre-strained Elasticity, that Marta will discuss in her talk, I will discuss some contrasts between the mechanics of thin objects with non-negative curvature (plates, spherical shells, etc) and the mechanics of hyperbolic sheets, i.e. soft/thin objects with negative curvature. I will motivate the need for new "geometric" methods for discretizing the relevant equations, and present some of our preliminary work in this direction.

This is joint work with Toby Shearman and Ken Yamamoto.

Approximate Abstractions of Markov Chains with Interval Decision Processes ⁎ ⁎ This research has been partially supported by the Alan Turing Institute, London, UK, by the ECSEL SafeCOP project n.692529, and by a grant from the Filauro Foundation.
Lun, Y Wheatley, J D’Innocenzo, A Abate, A IFAC-PapersOnLine volume 51 issue 16 91-96 (2018)
Temporal logic control of general Markov decision processes by approximate policy refinement
Haesaert, S Soudjani, S Abate, A IFAC-PapersOnLine volume 51 issue 16 73-78 (2018)
A touch of awe: crafting meaning from the wonder of the cosmos
Paulson, S Davies, P Louis, A Walkowicz, L Annals of the New York Academy of Sciences volume 1432 issue 1 46-62 (18 Aug 2018)
Fri, 02 Nov 2018

16:00 - 17:00
L1

Characteristic Polynomials of Random Unitary Matrices, Partition Sums, and Painlevé V

Jon Keating
(University of Bristol)
Abstract

The moments of characteristic polynomials play a central role in Random Matrix Theory.  They appear in many applications, ranging from quantum mechanics to number theory.  The mixed moments of the characteristic polynomials of random unitary matrices, i.e. the joint moments of the polynomials and their derivatives, can be expressed recursively in terms of combinatorial sums involving partitions. However, these combinatorial sums are not easy to compute, and so this does not give an effective method for calculating the mixed moments in general. I shall describe an alternative evaluation of the mixed moments, in terms of solutions of the Painlevé V differential equation, that facilitates their computation and asymptotic analysis.

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