Vanshaj Kerni | Research

Late time Stellar Evolution

(Supervisor: C.Muthumariappan and Prof. Moumita Maiti as co-supervisor.

Stellar evolution unfolds as stars undergo mesmerizing transformations, from birth in nebulous nurseries to dazzling supernova finales. Gravity, Nuclear fusion, and cosmic ballets orchestrate these awe-inspiring celestial narratives, revealing nature's sublime intricacies. The work is to understand one of such dramatic dance which begins at the Asymptotic Giant Branch evoltuionary stage, ( read ). As by earlier works, the movemet was thought to go in linear order from Wolf-Rayets( read ) --> Wels( read ) --> PG-1159 ( read ). This all changed, work by C Muthumariappan and M Parthasarathy , "Infrared properties of planetary nebulae with [WR] and wels central stars" ( read ) showed that [WR] and Wels have same family tree but are two different children. This brought the question for PG-1159. My work is about trying to answer what contribute to evolution of PG-1159. How much WR, Wels contribute to PG-1159. During the work, I figured that some of both contribute to PG-1159. Based on the work done at the time, it is likely that PG 1159 stars are descendants of hydrogen deficient [WR]s. However, the case of Wels needs to be clarified.

Relevant Publication: Vanshaj Kerni, "Analysing the evolutionary connection of Central Stars Planetary Nebulae of [WR], wels and PG-1159". Thesis defended successfully on June 2023. Read at: http://dx.doi.org/10.13140/RG.2.2.10403.22563 </div>

Dark Matter and Cosmology

(Mentor: Dr.Geetanjali Sethi)

The large-scale structure of the universe on a scale less than 100 Mpc consists of a network of overdense and underdense regions. Their evolution depends on the initial conditions and content of dark energy, studying them is valuable in constraining the cosmological parameters. Underdensities, or cosmic voids, especially provide reliable testing grounds for large-scale structure formation, cosmological parameters, and dark energy. In our work, the evolution of an isolated spherical underdense region in a homogeneous, expanding background is studied for different dark energy models. We start with reviewing the evolution for an Einstein-de Sitter cosmology and then adding additional models in the accerlation equaiton. Throughout the work, we assumed the initial density profile to be an inverse-top-hat and the density contrast is set to delta=-0.8, as taken by previous studies.
Relevant publication: Vanshaj Kerni Julie Jacob Thomas, Geetanjali Sethi, "The spherical evolution of cosmic voids in Chaplygin gas dark energy models". at 40th Meeting of the Astronomical Society of India held at Indian Institute of Technology Roorkee.

Fluid flow in microsize channels

(ongoing, Mentor: Prof. Ameeya K. Nayak)

Microfluidic technology has seen a tremendous growth in past couple of years. The reason being its coverage in manipulating fluid and species flow in small volumes. Research on new materials have given a new boost to such domains and now such devices are becoming common in diagnostics due to their long-range benefits. These devices are inexpensive, portable, and disposable, thus highly useful in health care systems. These are now becoming popular in research and clinical applications, including biosensing, drug development, and chemical synthesis. Clinical application useage such as plasma seperation are essentially dependent on proper understanding of blood flow in the micro domains.

Theoretical models on blood flow have highlighted the impact of arterial diameter to blood flow. However, only a few actual testing of these ideas have been recorded. A systematic study on factors characterising essential attributes of the blood is still lacking in the field despite their tremendous applications in the health care systems. Our work considers an incompressible Navier Stokes equations with a power-law model to study blood flow velocity in tw-o dimensions. We modelled the stenosed section as a simple compression and expansion region in a rectangular capillary. Our work, an expansion of previous works, has obtained important dependence among such factors.

Relevant publication: Vanshaj Kerni , M.Majhi, A.K.Nayak - Flow characteristics and platelet adhesion of blood flow in a corrugated microchannel with the reduction and extension of shear effects.
Procedings of the 26th National & 4th International ISHMT-ASTFE Heat and Mass Transfer. Conference Paper

Ultra Compact X-Ray Binary

One of the most exciting and poorly understood binary systems are the Ultra-Compact X-Ray binary (UCXB) system. Low Mass X-Ray Binary Systems (LMXB) subsets consist of an accretor and a donor star. Their possible configurations can be White Dwarfs(WD), or He stars as donors and NS/BH as their accretors with an orbital period of fewer than 80 minutes. UCXBs are essential objects that have attracted the attention of researchers across the world. UCXBs serve as laboratories for studying the physical mechanisms of accretion and the nature of compact objects in close proximity. In this work, we analysed the observational and stellar parameters of the Ultra-Compact X-Ray binary OGLE-UCXB-01, primarily following http://dx.doi.org/10.3847/1538-4357/ac06a7, to better understand how these systems work.

Relevant publication: A.Rawat, A.Mandal, A.Dattamunsi, S.Bhargavi, N.Ziyad, P.Kumar, B.Priyanka, R.Venugopal, S.MadhuSudhan, V.Kerni: Analysis of Stellar Parameters of Ultra Compact X-Ray Binary-OGLE-UCXB-01 [researchgate]

Particle simulation on Geant4

(Mentor: Prof. Jyothsna Komaragiri)

Particle Physics Phenomenology is the field where one tries to understand the fundamental interactions of particles of nature. Particle phenomenology bridges the high energy experiment with the theoretical understanding of the interaction. It, therefore, provides a basis for validating the theoretical predictions about the interaction processes. We need tools to simulate the theoretical predictions to work on validation efficiently. For this very reason, a Monte-Carlo based simulation toolkit, the Geant4 project, was initiated in the context of the CERN RD44 R&D project as a worldwide collaboration. Geant4 is a multi-purpose toolkit to explore the nature of collisions and energy loss of particles. It is used in fields where particle interaction is required, ranging from high energy physics to medical physics and space physics research. The physics component offers various simulations packages and tools to study the processes involved. The work used the electromagnetic package to verify the Bethe-Bloch energy loss formula for charged particles developed mainly by Hans Bethe and analyse the extent of its validity.

Relevant publication: V.Kerni, J.Komaragiri: Verification of Bethe-Bloch formula using Geant4 toolkit [arXiv:hep-ph]

Asteroseismology of stars

(Methor: Prof. Anwesh Mazumdar)

Asteroseismology is the study of the oscillations occurring inside a star by analysing the periodicity of the luminosity variations, which leads to inferences about the star's internal structure, which is otherwise beyond the scope of observational astronomy. For a non-technical reader, as analogous to seismic oscillations or earthquakes on Earth, a star also experiences "quakes" or "oscillations" where different modes of changes occur depending on the position inside the star,namely P, G, F, Mixed modes occurs inside the star. My work in the undergraduate project involved learning the asteroseismology theory and data analysis and reduction techniques used in the field by validating the theoretical framework, Stellar Structure and Evolution for theory and Asteroseismic data analysis for data analysis.

Relevant publications: V.Kerni and A.Mazumdar. Asteroseismology of Solar Type Stars [researchgate].

Nuclear aspect of Astrophysics

(Mentor: Prof. Anil Gourishetty)

Astrophysics is a multi-discipline area of research that requires grasping every significant concept in physics, from particle physics to fluid dynamics to quantum physics and gravitation. Nucleosynthesis is the formation of elements in the hot stellar stoves where temperatures are of the order of Million Kelvins. Every star begins its lifecycle from the ZAMS (zero-age-main-sequence) position in the HR (Hertzsprung–Russell) diagram, evolving in many possible paths determined by its initial birth mass. A massive star begins up high in the HR diagram, evolve fast and dye spectacularly in the form of supernovas. In contrast, a low mass star starts in the lower position, evolve in an almost everlasting time frame and ends in the smallest possible "spheres". The element formation in the stars is dependent on the core temperature and therefore are many in number, namely pp-cycle, CNO-cycle, r-process, p-process, s-process. My first undergrad project involved reviewing previous works on stellar evolution, element formation processes, and general academic research.