Theoretical Statistics and Mathematics Unit

## Past month's Seminars and Colloquia

[Past seminars of this year] [Colloquia archive] [All Seminars archive]

### BANGALORE PROBABILITY SEMINAR

Title : Quantum Markov Semigroups
Speaker : B. V. Rajarama Bhat (ISI Bangalore)
Time : August 20, 2018 (Monday), 02:00 PM
Venue : Auditorium
Abstract : Quantum Markov Semigroups are non-commutative or quantum analogues of transition probability semigroups coming from Markov processes. Here we give a brief introduction to this subject.

### BANGALORE PROBABILITY SEMINAR

Title : Application of urn models in load balancing and opinion dynamics.
Speaker : Gursharn Kaur (ISI Bangalore)
Time : August 20, 2018 (Monday), 03:15 PM
Venue : Auditorium
Abstract : In this talk, we will talk about applications of urn models in load balancing and opinion dynamics. In the first part of the talk, we will introduce the choice of two in negatively reinforced Polya urn models. For this model, we show that the urn configuration converges to uniform distribution and asymptotic normality holds. In particular, we focus on the paradigm of two choices for urn models with finitely many colours. In the second part of the talk, we will talk about an opinion dynamics model on a finite network through interacting urns. We consider a graph of $N$ vertices, such that there is a 2- colour urn at each vertex and the reinforcement in an urn depends on all its neighbouring urns. We observe that if the graph is connected, it always reaches a consensus. In particular we show that, even when the replacement in each urn is not of Polya type, it behaves as a network of N independent Polya urns. Joint work with Antar Bandyopadhyay (ISI Delhi) and some parts with Neeraja Sahasrabudhe (IISER Mohali).

### STUDENT SEMINAR

Title : The Linear Algebra method in Combinatorics and Geometry
Speaker : Koushik Ramachandran (TIFR Bangalore)
Time : August 21, 2018 (Tuesday), 03:30 PM
Venue : G25
Abstract : In this talk I will illustrate how linear algebraic methods can be used to help bound combinatorial quantities. While the method is very large in scope, we restrict ourselves to some examples that will give a flavor of the subject. I will end with a tantalizing conjecture due to Zauner about the number of equiangular lines in Euclidean space. The talk will be understandable to anyone familiar with the basics of linear algebra.

### BANGALORE PROBABILITY SEMINAR

Title : RKHS Embedding of Probabilities & Measures of (In)dependence
Speaker : Bharath K Sriperumbudur (Penn State Univ USA)
Time : August 27, 2018 (Monday), 02:00 PM
Venue : Auditorium
Abstract : Modern scientific fields (e.g., social sciences, bioinformatics, biomedical imaging, and genomics) routinely deal with high-dimensional and highly complex information, including data from non-Euclidean spaces such as trees, graphs and strings. In this talk, I will introduce a functional analytic method for representing and analyzing high-dimensional and complex data by embedding probability measures into a reproducing kernel Hilbert space (RKHS). Such embeddings can be seen as a generalization of characteristic function associated with a probability measure. This generalization allows to represent and compare random variables on domains more general than R^n (including graphs, strings, and groups), which can then be exploited in many statistical applications like homogeneity/independence/goodness-of-fit testing, feature selection, and density estimation. I will discuss various theoretical questions related to distribution embeddings, for example, when is the embedding injective and how it is related to the properties of the RKHS? Based on this embedding, I will introduce measures of (in)dependence between random variables and present results related to the characterization of joint independence.

### BANGALORE PROBABILITY SEMINAR

Title : How to tell a tale of two tails?
Speaker : Parthanil Roy (ISI Bangalore)
Time : August 27, 2018 (Monday), 03:15 PM
Venue : Auditorium
Abstract : A branching random walk is a system of growing particles that starts from one particle at the origin with each particle branching and moving independently of the others after unit time. In this talk, we shall discuss how the tails of progeny and displacement distributions determine the extremal properties of branching random walks. In particular, we have been able to verify two related conjectures of Eric Brunet and Bernard Derrida in a few cases that were open before. This talk is based on a joint work with Souvik Ray (M. Stat dissertation work at Indian Statistical Institute), Rajat Subhra Hazra (Indian Statistical Institute) and Philippe Soulier (University of Paris Nanterre).

### STUDENT SEMINAR

Title : Ensuring Right to Work: Field Experiences from Jharkhand
Speaker : Udvas Das (ISI Bangalore)
Time : August 28, 2018 (Tuesday), 03:15 PM
Venue : Platinum Jubliee Auditorium
Abstract : National Rural Employment Guarantee Act (NREGA) is a social security measure to ensure ‘right to work’ in India. Under the guidance of Prof. Jean Dreze, the architect of NREGA, during the last few years, NREGA “sahayata kendras” (help centres) have been set up in many Blocks of Jharkhand. The basic purpose of the kendras is to help NREGA workers secure their entitlements under the Act. This involves activities such as awareness campaigns, work application drives, social audits, helping workers with payment issues, and the odd demonstration or street action. Many kendras also work on related issues such as food security and old-age pensions. This talk will encompass an experience of working on such a Sahayata kendra in one of the most backward regions of India with the purpose of understanding ‘what it takes’ to ensure fundamental right to ‘work’ in India.

### COLLOQUIUM

Title :Existence of self-dual cuspidal representations
Speaker : Manish Mishra (IISER Pune)
Time : September 3, 2018 (Monday), 03:30 PM
Venue : Auditorium
Abstract : Cuspidal representations are building blocks of all irreducible representations of finite and p-adic groups. I'll review some basic theory about the construction of cuspidal representations. I'll then talk about our result which gives a necessary and sufficient condition for the existence of self-dual cuspidal representations of finite reductive groups and unramified reductive groups over non-archimedean local fields. This is a joint work with Jeffrey Adler.

### STUDENT SEMINAR

Title : Infusing Statistical Ecology into Species Recovery : Tigers in India
Speaker : Ullas Karanth (Wildlife Conservation Society - Bangalore)
Time : September 4, 2018 (Tuesday), 03:15 PM
Venue : Platinum Jubliee Auditorium
Abstract : Large carnivorous mammal species are in a decline globally due to human induced pressures such as hunting and habitat degradation. India represents an extreme case in both the scale of the challenges and sporadic successes in the case of its national animal-the tiger. Efforts at reversing this decline are receiving a lot of attention and investments. However, understanding the dynamics of single tiger populations, meta-populations or habitat occupancy dynamics are crucial to make these efforts effective. In spite of India having a pre-eminent position globally as a leader in statistical sciences, the essential critical link between applied statistics on one hand and studies in areas of science and conservation of tigers practically do not exist. This has lead to practice of tiger conservation in India that is almost divorced from rigorous statistical ecology, whose cutting edge products are adopted globally but are 'unsold stock' in our own country. This is primarily due to issues of government's institutional culture. I will illustrate these issues with respect to large scale studies of tigers conducted by Centre for Wildlife Studies in Western Ghats, which has successfully incorporated a model of collaboration between tiger ecologists and applied statisticians and generated many useful conservation solutions. I submit that ISI as well as other Scientific Ministries of Government of India have an obligation to address this problem effectively and in real time. Without such interventions the fate of many endangered species will remain uncertain even as we attain greater prosperity in other areas of social development. There shall be coffee & snacks after the talk

### STUDENT SEMINAR

Title : Statistical physics and statistics in understanding dynamics of ecological systems
Speaker : Vishwesha Guttal (Center for Ecological Sciences IISC)
Time : September 18, 2018 (Tuesday), 03:00 PM
Venue : Platinum Jubliee Auditorium
Abstract : Ecosystems can be viewed as complex dynamical systems where a large number of living organisms interact to produce many emergent patterns. In this talk, I will demonstrate some examples of ecological phenomena where principles of nonequilibrium statistical mechanics, bifurcation theory together with statistical tools of data analyses offer novel insights and predictive power in our understanding of ecology. Specifically, I present examples of tipping points where ecosystems can abruptly switch to a state with contrasting features. Commonly cited empirical examples of tipping points are desertification in semi-arid ecosystems, algal blooms in aquatic ecosystems, paleo-climatic shifts, and crashes in financial markets. More recently, these ideas have also been applied in genetic circuits and regulatory networks. By drawing an analogy to physics of phase transitions, I will present how one can devise early warning signals of such tipping points. I will discuss empirical evidence for these theoretical predictions from savanna and desert ecosystems, lakes as well as financial markets. If time permits, I will also talk about collective behaviour in animal groups where one finds spectacular forms of synchrony in moving animal groups.

[Seminar] [All upcoming Seminar] [Stat Math Unit] [Indian Statistical Institute]