- Topology Graduate Course:- started on 27-07-07, continued till 11.04.08, place:- School of Mathematics, Tata Institute of Fundamental Research, title:-Topology. (Primary source: `Algebraic Topology' by E. Spanier). (Total 66 `one hour class-room lectures').
- Topology Graduate Course:- started on 10-08-15, continued till 15.04.16 place:- School of Mathematics, Tata Institute of Fundamental Research, title:-Topology. (Primary source: `Algebraic Topology' by E. Spanier, also from Hatcher's book). (Total 82 `one hour class-room lectures').
- `Manifold Topology' Advanced Graduate Course:- started on 20-07-16. (Write up of the first three lectures (5hrs) is in the published section: `Manifold Topology: A Prelude'. It contains some basic materials to make it accessible by students in India. Rest of the course includes Homotopy Theory, Differential Topology, Morse Theory, h-cobordism theorem...).

- Colloquium talk: date:- 12-09-96, place:- Tata Institute of
Fundamental Research, title:- Subcomplex complements in {\Bbb
S}^3: L-theory and curvature.

- Oberseminar Topologie: date:- 17-11-97, place:- Max-Planck Institut f\"{u}r Mathematik, title:- Surgery groups of submanifolds of the 3-sphere.
- MPI-Oberseminar: date:- 04-12-97, place:- Max-Planck Institut f\"{u}r Mathematik, title:- Nonpositive curvature on link complements and Surgery groups.
- Oberseminar Differential Geometry: date:- 09-12-97, place:- University of Bonn, title:- Surgery obstruction groups and nonpositive curvature in 3-manifolds.
- Colloquium talk: date:- 26-11-98, place:- Tata Institute of Fundamental Research, title:- Vanishing structure set of Haken 3-manifolds.
- Mathematics seminar: dates:- 06-04-99 and 08-04-99, place:-Mehta Research Institute, title:- Vanishing structure set of Haken 3-manifolds.
- Oberwolfach meetings (Topologie): dates:- 06-09-98 to 12-09-98, place:- Mathematisches Forschungsinstitut Oberwolfach, title:-Algebraic K-theory of pure braid groups, talk presented by F.T. Farrell.
- Mathematics seminar: dates:- 29-08-2000, place:- Mehta Research Institute, title:- Finiteness of simple homotopy type up to s-cobordism of aspherical 4-manifolds.
- Allahabad Low Dimensional Topology Instructional Conference: date:- 18-12-2000 to 31-12-2000, place:- Allahabad University and Harish Chandra Research Institute, titles:-Knot theory and 3-manifolds (3 lectures); Seifert fibered spaces (1 lecture); 4-manifolds (1 lecture).
- Special Mathematics Seminar: date:- 15-02-2001, place:- Stat-Math Unit, Indian Statistical Institute, Calcutta, title:- K-theory of braid groups.
- Mathematics Seminar: date:- 30-04-2001, place:- Mathematics Section, The Abdus Salam ICTP, Trieste, Italy, title:- L-theory of 3-manifolds.
- Algebra/Topology/K-theory Seminars: date:- 02-05-2001, place:- Mathematics Section, The Abdus Salam ICTP, Trieste, Italy, title:- Algebraic K-theory of braid groups.
- Algebra/Topology/K-theory Seminars: date:- 09-05-2001, place:- Mathematics Section, The Abdus Salam ICTP, Trieste, Italy, title:- Simple homotopy types of aspherical 4-manifolds.
- Geometric Group Theory Seminar: dates:- 20,25,27-09-2001, place:- Harish-Chandra Research Institute, Allahabad, India, title:- Non-positively curved simplicial complexes.
- Colloquium talk: date:- 28-09-2001, place:- Harish-Chandra Research Institute, Allahabad, India, title:- A representation of generalized braid group in classical braid group.
- Colloquium talk: date:- 22-11-2001, place:- Tata Institute of Fundamental Research, title:- The Whitehead group of Artin braid group.
- Delhi Algebraic and Geometric Topology Conference: date:- 01-01-2002 to 04-01-2002, place:- Delhi University, Delhi, India, title:- Topology of 3-manifolds and a class of groups.
- Chennai Topological Methods in Group Theory workshop: date:- 15-07-2002 to 27-07-2002, place:- Institute of Mathematical Sciences, Chennai, India, title:- Cartan Hadamard theorem.
- Satellite Conference of ICM2002 on Geometric Topology: date:- 12-08-2002 to 16-08-2002, place:- Shaanxi Normal University, Xi'an, China, title:- Topology of 3-manifolds and a class of groups.
- International Congress of Mathematicians: date:- 20-08-2002 to 28-08-2002, place:- Beijing, China, title:- The Whitehead group of a class of discrete groups. This lecture was a short communication.
- VSRP lecture: dates:- 02-07-2003 and 04-07-2003, place:-Tata Institute, title:- Introduction to differentiable manifolds.
- Conference on Topology: dates:- 14-07-2003 to 25-07-2003, place:- Mathematical Sciences Institute, The Australian National University, Canberra, title:- Vanishing of Whitehead group of a class of groups.
- Joint India-AMS Mathematics meeting:- dates:- 17-12-2003 to 20-12-2003, place:- Indian Institute of Science, Bangalore, title:- On groups with (un)-stabilized derived series. This lecture was an invited talk in the special session on Algebraic and Geometric Topology.
- Algebraic Geometry Seminar:- date:- 14-05-2004, place:- Tata Institute of Fundamental Research, title:- Finite group action on simplicial complexes.
- An advanced instructional workshop on low-dimensional topology
and geometric group theory:- dates:- 12-07-2004 to 24-07-2004,
place:- Indian Statistical Institute, Bangalore, India, title:-
K-theory of 3-manifold groups. (3 lectures).

- Oberseminar Topologie:- date:- 21-11-2005, place:- Mathematisches Institut, Universitaet Muenster, title:- The Isomorphism Conjecture for 3-manifold Groups.
- Colloquium talk:- date:- 20-07-2006, place:- Tata Institute of Fundamental Research, title:- The Farrell-Jones Isomorphism Conjecture for 3-manifold groups.
- VSRP lecture: dates:- 02-07-2008 and 09-07-2008, place:-Tata Institute of Fundamental Research, title:- Algebraic Topology.
- International Conference in Mathematics: date:- 18-03-2009, place:- Harish Chandra Research Institute, Allahabad, India, title:- The Farrell-Jones Isomorphism conjecture and groups acting on trees.
- Colloquium talk: date:- 18-03-2010, place:- Tata Institute of Fundamental Research, title:- The Isomorphism Conjecture for groups acting on trees.
- VSRP lecture: date:-30-06-2010, place:- Tata Institute of Fundamental Research, title:- The Schoenflies theorem for surfaces.
- The 76-th annual conference of the Indian Mathematical
Society: place:- National Institute of Technology, Surat, India,
title:- The Farrell-Jones Isomorphism Conjecture.

- An advanced instructional school in Algebraic Topology: dates:- 13-06-2011 to 02-07-2011, place:- North-Eastern Hill University, Shillong, India, title:- Fixed point and duality theorems in algebraic topology. (9 lectures).
- Geometry and Topology in Samos:-11-06-2012 to 15-06-2012, place:- The University of the Aegean, Samos, Greece, title:- The Farrell-Jones isomorphism conjecture for a certain class of groups. (On the occassion of the 70th birthday of Professor Tom Farrell).
- Conference on Group actions and applications in Geometry,
Topology and Analysis, dates:- 21-07-2012 to 29-07-2012, place:-
Kunming University of Science and Technology, Kunming, China,
title:- The Isomorphism conjecture for groups acting on trees.

- 27th Annual Conference of the Ramanujan Mathematical Society, dates:-
19-10-2012 to 23-10-2012, place:-Shiv Nadar University, New Delhi, India,
title:- K and L-theory of groups acting on trees.

- International ATM workshop on surgery theory and classification of manifolds, dates:-
17-06-2013 to 26-06-2013, place:-North-Esatern Hill University, Shillong, India,
title:- Morse theory and $s$-cobordism theorem. (5 lectures)

- International conference on surgery theory and classification of manifolds, date:-
25-06-2013, place:-North-Eastern Hill University, Shillong, India,
title:- K and L-theory of groups acting on trees.

- Topology and Groups, date:- 17-10-2015, place:- Goa University, title:- A
generalisation of a certain class of Artin groups.

- Colloquium talk, date:-17-05-2016, place:-TIFR CAM, Bangalore, India, title:-Algebraic
K and L-theory of Artin groups.

- Seminar talk, date:-26-05-2016, place:-IISC, Bangalore, India, title:- Algebraic K
and L-theory of groups acting on trees.

- Seminar talk, date:-27-05-2016, place:-IISC, Bangalore, India, title:- The
isomorphism conjecture for Artin groups.

- Students Seminar, date:- 14-06-16,
place:- Tata Institute of
Fundamental Research, title:-An obstruction group in Topology.