Talks

Any consistent regularization scheme induces an apparent violation of gauge invariance in non-anomalous chiral gauge theories. This violation shows up in perturbative calculations, and can be removed by including appropriate finite counterterms. In this talk I will discuss the derivation of such counterterms for a renormalizable chiral gauge theory.  I will use the background field method, which ensures background gauge invariance in the quantized theory. As a concrete application, I will show the finite counterterm at one loop in the Standard Model, within dimensional regularization and the Breitenlohner-Maison-'t Hooft-Veltman prescription for gamma5. 

Zoom Link: https://pitp.zoom.us/j/95507223984?pwd=Y0FDTEJpNDlVaE9Ba1ZNMURXeS9rdz09

Understanding the reason behind the observed accelerating expansion of the Universe is one of the most notable puzzles in modern cosmology, and conceivably in fundamental physics. In the upcoming years, near future surveys will probe structure formation with unprecedented precision and will put firm constraints on the cosmological parameters, including those that describe properties of dark energy. In light of this, in the first part of my talk, I'm going to show a systematic extension of the Effective Field Theory of Dark Energy framework to non-linear clustering. As a first step, we have studied the k-essence model and have developed a relativistic N-body code, k-evolution.

I'm going to talk about the k-evolution results, including the effect of k-essence perturbations on the matter and gravitational potential power spectra and the k-essence structures formed around the dark matter halos. In the second part of my talk, I'm going to show that for some choice of parameters the k-essence non-linearities suffer from a new instability and blow up in finite time.

This talk is based on: arXiv:2204.13098, arXiv:2205.01055, arXiv:2107.14215, arXiv:2007.04968, arXiv:1910.01105, arXiv:1910.01104.

Zoom Link: https://pitp.zoom.us/j/99797451101?pwd=dituM2d2MDFCbDgyVXJ4c2s1NVoyUT09

An exciting development in outer solar system studies is the discovery of a new class of Kuiper belt objects with orbits that lie outside that of Neptune and have semimajor axes in excess of 250 A.U. The alignment of the major axes of these objects and other orbital anomalies are the basis for the Planet Nine hypothesis that an undiscovered giant planet orbits the sun at a distance of around 500 A.U. We show that a modified gravity theory known as MOND (Modified Newtonian Dynamics) provides an alternative explanation for the observed alignment, owing to significant quadrupolar and octupolar terms in the MOND galactic field within the solar system that are absent in Newtonian gravity. Using the well-established secular approximation of solar system dynamics we predict a population of Kuiper belt objects whose major axes are aligned with the direction to the center of the galaxy and that have additional clustering in orbital parameters. These features are exhibited by known Kuiper belt objects of the newly discovered class in support of the MOND hypothesis. Thus MOND, originally developed to explain galaxy rotation without invoking dark matter, may also be observable in the outer solar system.

Quantum mechanics is a cornerstone of modern physics. Just as the 19th century was called the Machine Age and the 20th century the Information Age, the 21st century promises to go down in history as the Quantum Age. Quantum Computing promises unprecedented speed in solving certain classes of problems while Quantum Cryptography promises unconditional security in communications. In this talk, I will discuss the world of single and entangled photons and also discuss ongoing work towards quantum computing, quantum information and quantum cryptography in our Quantum Information and Computing lab at the Raman Research Institute, Bengaluru. I will end with our broad vision for the future, which includes establishment of long distance secure quantum communications in India and beyond involving satellite based, fibre based as well as integrated photonics based approaches towards the global quantum internet.

Zoom Link: https://pitp.zoom.us/j/94788493307?pwd=QTlUaTY4Nm1IS3hyeUFIbVFKV3RMQT09

We present a series of (partly proven) conjectures
describing geometric realizations of
categories of (finite-dimensional) representations of quantum
super-groups U_q(g) corresponding
to Lie super-algebras g with reductive even part and a non-degenerate
invariant form.
We shall also discuss the meaning of these conjectures from the point
of view of local geometric Langlands correspondence as well as a
connection to the work of Ben-Zvi, Sakellaridis and Venkatesh.
Based on joint works with M.Finkelberg, V.Ginzburg and R.Travkin as
well as the work of R.Travkin and R.Yang.

I will discuss a close parallel between Gaiotto and Witten's S-duality for supersymmetric boundary conditions in 4d N=4 SYM and the relative Langlands program, an enhancement of the Langlands program that was developed to provide a framework for the theory of integral representations of L-functions. A special and conjecturally self-dual class of boundary conditions is provided by quantizations of "small" or "multiplicity-free" hamiltonian spaces called hyperspherical varieties. I'll explain how a hyperspherical variety produces objects of interest in all the different settings of the Langlands program (local / global, geometric / arithmetic) and a collection of conjectures providing S-dual descriptions of these objects. The talk is based on forthcoming joint work with Yiannis Sakellaridis and Akshay Venkatesh.

In this lecture I'll discuss various aspects of 4d N=2 and 5d N=1 supersymmetric QFT's in the 1/2 Omega-background (and along the way try to emphasize some relations to the 3d N=2 theories discussed in this workshop). Central to this story is the Nekrasov instanton partition function (or topological string partition function) in this background, which we will obtain through abelianization as an integral of a ratio of Wronskians of certain special solutions to the relevant Schrodinger equation. We will argue that a slight generalization of the above partition function solves an associated Riemann-Hilbert problem and defines a section of a distinguished line bundle over the moduli space of flat connections.