Is adoption of new products affected by the social network? Mathematical Marketing and Agent-Based approaches

Speaker: 

Gadi Fibich

Time: 

Monday, February 6, 2012 - 4:00pm

Location: 

RH 306

The adoption of new products which mainly spread through word-of-mouth (such as fax machines, skype, facebook, Ipad, etc.) is one of the key problems in Marketing research. Ideally, given the sales data of the first few months, one would like to be able to predict both the future sales and the overall market potential.

In this talk I will first present the classic Bass model and the agent-based approach for the adoption of new products. Then, I will present some recent analytic results on the effect of the social network on the adoption of new products.

This is joint work with Ro'i Gibori and Eitan Muller

Uniqueness of Self-shrinkers of Mean Curvature Flow

Speaker: 

Dr. Lu Wang

Institution: 

MSRI and Johns-Hopkins

Time: 

Tuesday, December 6, 2011 - 4:00pm

Location: 

RH 306

Recently, using the desingularization technique, a new family of complete properly embedded self-shrinkers asymptotic to cones in three dimensional Euclidean space has been constructed by Kapouleas-Kleene-Moeller and independently by Nguyen.

In this talk, we present the uniqueness of self-shrinking ends asymptotic to any given cone in general Euclidean space. The feature of our uniqueness result is that we do not require the control on the boundaries of self-shrinking ends or the rate of convergence to cones at infinity. As applications, we show that, there do not exist complete properly embedded self-shrinkers other than hyperplanes having ends asymptotic to rotationally symmetric cones.

Minimal Lagrangian immersions in CH^2

Speaker: 

Professor Zheng Huang

Institution: 

CUNY, Staten Island

Time: 

Wednesday, January 18, 2012 - 3:00pm

Location: 

RH 306

We consider the problem of minimal Lagrangian immersions of disks into CH^2 which are equivariant to some surface group representation. We prove several results on existence and (non)uniqueness. The local parameterization of the immersion is given by the conformal structure on a closed surface and a holomorphic cubic differential on that conformal structure, hence of complex dimension 8g-8, where g>1 is the genus. This is a joint work with John Loftin and Marcello Lucia.

A Glimpse of Stochastic Dynamics

Speaker: 

Jinqiao Duan

Institution: 

IPAM, UCLA

Time: 

Wednesday, January 11, 2012 - 3:00pm

Location: 

RH 306

Nonlinear dynamical systems arising in biological, physical and chemical sciences are often subject to random influences, which are also known as noise. Stochastic differential equations are appropriate models for some of these systems. The noise in these stochastic differential equations may be Gaussian or non-Gaussian in nature. Non-Gaussianity of the noise manifests as nonlocality at some macroscopic level. In addition, randomness may have delicate, or even profound, impact on the overall evolution of dynamical systems. The speaker will present an overview of some available theoretical and numerical techniques for analyzing stochastic dynamical systems, especially escape probability, mean exit time, invariant manifolds, bifurcation and quantifying the impact of uncertainty. The differences in dynamics under Gaussian and non-Gaussian noises are highlighted, theoretically or numerically.

Skew products with interval fibers

Speaker: 

Denis Volk

Institution: 

SISSA, Italy

Time: 

Friday, November 18, 2011 - 2:00pm

Location: 

RH 440R

Skew products over subshifts of finite type naturally appear when one attempts to apply the methods of classical dynamical systems to random dynamical systems. There is also a close connection between these skew products and partially hyperbolic dynamical systems on smooth manifolds.

Even for the fiber dimension equal to one, we are far from understanding what typical skew products look like. During the last 30 years there appeared several papers studying the skew products with a circle fiber. I will talk about the case when the fiber is an interval, and fiber maps are orientation-preserving diffeomorphisms.

In the work joint with V. Kleptsyn, we developed a theorem which gives us a complete* description of the dynamics of typical step skew products (fiber map depends only on a single symbol in the base sequence). We also obtained a similar result for generic skew products using an additional assumption of partial-hyperbolic nature.

*except some subset which projects onto zero measure set in the base

Effective Dynamics of Stochastic Partial Differential Equations

Speaker: 

Professor Jinqiao Duan

Institution: 

IPAM

Time: 

Tuesday, February 14, 2012 - 11:00am

Location: 

RH 306

The need to take stochastic effects into account for modeling complex systems has now become
widely recognized. Stochastic partial differential equations arise naturally as mathematical
models for multiscale systems under random influences. We consider macroscopic dynamics of
microscopic systems described by stochastic partial differential equations. The microscopic
systems are characterized by small scale heterogeneities (spatial domain with small holes or
oscillating coefficients), or fast scale boundary impact (random dynamic boundary condition),
among others.

Effective macroscopic model for such stochastic microscopic systems are derived. The effective
model s are still stochastic partial differential equations, but defined on a unified spatial domain
and the random impact is represented by extra components in the effective models. The
solutions of the microscopic models are shown to converge to those of the effective macroscopic
models in probability distribution, as the size of holes or the scale separation parameter
diminishes to zero. Moreover, the long time effectivity of the macroscopic system in the sense of
convergence in probability distribution, and in the sense of convergence in energy are also
proved.

Perturbations in homological algebra

Speaker: 

Vladimir Baranovsky

Institution: 

UC Irvine

Time: 

Thursday, December 1, 2011 - 1:00pm

Location: 

RH 440R

A very useful technique in homological algebra, is the Basic Peturbation Lemma which tells how cohomology of a complex changes when a differential is perturbed. It has numerous applications in algebra, topology, and computational methods in algebra; some of which will be reviewed in the talk.

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