ACADEMIC

Two heavy objects orbiting each other will create ripples in the fabric of spacetime(this fabric is a mathematical description that helps visualize Einstein's theory, it isn't to be taken literally).  Artwork by Sandbox Studio, Chicago with Corinne Mucha

Present gravitational wave detectors primarily observe short lived and strong signals from compact binary systems. Continuous sources, like those from a spinning neutron star, are weaker and require longer observation time. Accurate modeling of these sources is essential for informed resource allocation. My project aims at modelling the gravitational wave signal from one such neutron star, which is orbiting a red-giant core with a shared envelope. Such binary systems, commonly known as common envelope systems are challenging to observe through electromagnetic means, but gravitational waves offer a possible solution. I developed a common envelope module in MESA, a stellar evolution software, to model the expansion of the red giant envelope during the common envelope phase using hydrodynamics. I compare my results with those of Holgado (2018), which assume a hydrostatic envelope.

A mollweide projection a constant radius surface of a spherical dark matter halo. The color indicates the number density of galaxies in the halo, with red being densest.

In this internship project, I developed a python library to visualise dark matter halos using Vornoi tessellation. Depending on the density profile, we can populate a dark matter halo with galaxies. The denser a region is, the smaller the vornoi volume corresponding to the galaxies in that region is. We can study the morphology of dark matter halos using this principle, and compare it with actual survey data to improve our models. Observational artefacts like redshift space distortion (caused by motion of galaxies within the halo) and gravitational redshift (cause by the gravitational potential of the galaxies) can distort the observed distances to galaxies in surveys, and consequently affect the dark matter halo profile. We can incorporate this effect into simulations, to learn how to get back the true halo profile from actual survey data.

Evolution of total mean magnetic field of galaxy at galactic plane, for different strengths of Omega and Alpha effect.

Galaxies contain ionised plasma which interacts and evolves with the galactic magnetic field. Studying the evolution of the mean galactic magnetic field would therefore help us understand the global evolution of the galaxy itself. Galaxy disk rotation(omega effect) and interstellar medium turbulence(alpha effect) influence the growth or decay of the mean fields. Depending on the extent of these effects, it is possible to observe mean fields that are oscillatory in nature, which could affect the galaxy’s properties periodically. I explore the parameter space of omega and alpha effects to understand which mean field solutions are oscillatory and also draw conclusions about the oscillation frequencies of the fields. 

The Einstein Cross Q2234+030. The Four objects that make up a cross in this image are actually different images of the same quasar, formed by the bending light around a massive body between the line of sight to the quasar. Image: NASA, ESA, and STScI

I designed a website about Gravitational Lensing or the bending of light around massive objects as a semester project for an Astrophysics Course. I have tried to make it accessible to 3rd/4th year undergraduate students. I have also discussed some recent work, and provided with links to open source resources that can be used to learn more about this phenomena. Feel free to contact me if you have any queries or suggestions!

A 3D simulation to visualize the cosmic web of galaxies and their cluster on a very large scale. Image: V.Springel, Max-Planck Institut für Astrophysik, Garching bei München 

I derived the Cosmological equations describing the universe's evolution, and studied the evolution of universes with different cosmological models. I produced plots for many general cases, including, but not limited to the ones discussed in Barbara Ryden's book, my primary reference.

A visualisation of a Jupiter like exoplanet very close to the host star, also called a "Hot Jupiter". Image: NASA/JPL-Caltech 

Serving as an assistant team leader, I led a numerical study on the enhancement of stellar chromospheric activity due to close by hot Jupiters. We studied the model of A. F. Lanza (2008) which estimated the enhancement for circular planetary orbits, and extended it to include elliptical orbits. 

Interface of silicon oil(top layer) and water(bottom layer), which is being heated centrally from the bottom, as observed by our Schlieren setup.

As part of our continuous Schlieren Project, me and R. Vasanth Kashyap utilised our setup to examine convection in liquids, specifically water, silicon oil, and their interface. By analysing the images obtained, we converted the intensity maps to refractive index maps and then to temperature maps. We observed some very interesting structures in the convection cells. You can check out the report by clicking on the image.

The air perturbations around a lighter flame made visible by our Schlieren Imaging setup

When light passes through any medium, it refracts and bends around it. This will introduce a change in an otherwise defined beam of light when it was simply passing through an even medium, compared to when it passes through a medium. It is possible to probe these tiny fluctuations in the beam by mean of a simply optical setup proposed by Schlieren. I and Vasanth Kashyap build this setup for our Open Lab Project.

The core and cladding of a optical fiber made visible by our Phase contrast setup. The center of the fiber would look opaque in simple white light.

A simple microscope, with a white light source, is useful in viewing colored samples, but it cannot differentiate between the different parts of a transparent sample or one that looks the same compared to its surrounding medium. A Phase Contrast Microscope uses the phase shifts of light to convert them to brightness changes in the observed image. In this experiment, I and R. Vasanth Kashyap built the first PCM of our lab, which will be added to the curriculum for coming batches. We have also discussed how this microscope, which is primarily used in Biology, can be used to observe some physics phenomena like the dynamics of bubbles in emulsions.

The Fourier transform image of a 2 dimensional grating(basically a 2D opaque grid with periodic holes in it)

Me and my labmate R. Vasanth Kashyap built a setup that can produce the Fourier transform image of any given image. If we again Fourier transform this Fourier transformed image, we know from the mathematics that we get back the original image. But if we filter out some of the Fourier image of the original image, and then let this filtered part be Fourier transformed, we can remove or enhance certain features of the original image. We can also use the Fourier images to develop more efficient ways of matching fingerprints for Forensic science. We demonstrated all these properties using our setup.