About me

I am a cosmologist interested in theories of gravity to understand the dark sector of the universe and testing gravity theories: from cosmology to strong gravity systems, like black holes. At present, I am a postdoc fellow at the Centre for Theoretical Physics and Natural Philosophy at Mahidol University, Thailand. Before joining this position, I held a short-term postdoc at Yukawa Institute for Theoretical Physics, Kyoto University, where I finished my thesis work on "Theoretical and Observational Constraints on the Cosmology of Theories of Gravity".

Discover More

Curriculum
Vitae

2023

Centre for Theoretical Physics and Natural Philosophy, Thailand

I believe this is my first postdoc, where I am working on dark energy theories and their cosmological tests. In particular, I work on interacting dark sector models.

April 2021

Yukawa Institute for Theoretical Physics

It was a short-term position for six months while waiting for a visa from China during COVID-19. During this time I extended the minimal theories of massive gravity, and we call it eMTMG. This theory has many interesting properties.

Sep 2021

Kyoto University

I did my PhD from the cosmology research group, at Yukawa Institute for Theoretical Physics at Kyoto University, Japan. I learned quite a lot about Physics from my advisor and my friends. During this the time I was working on theoretical and observational tests of gravity theories in the context of cosmology. I have also been involved in addressing the Hubble tension with extended theories of gravity.

If you want my full CV, click Download full CV

Research
Interests

My research interest primarily falls on theories of gravity. In particular, I work on theories beyond GR: from IR modification, understanding dark energy physics to UV/strong gravity modification and testing gravity theories: from cosmology to strong gravity systems, like black holes. I am also actively involved in understanding tensions in cosmology from the perspective of beyond LCDM.

Dark Energy Theories

Read more

Testing Gravity

Read more

Cosmological Tension

Read more

Dark Energy Theories

Accelerated expansion of the late-time universe is one of the intriguing problems in cosmology. The simplest solution is to add a constant, known as cosmological constant (C.C.) to Einstein's theory of gravity, General Relativity (GR). Another possibility is to find a dynamical origin of the accelerated expansion by adding additional components (Dark Energy) to the theory of gravity. One can also try to modify the theory of gravity by carefully breaking the assumptions/principles behind the standard theory of gravity (Modified Gravity).

One of my research is to construct different dark energy theories or modified gravity theories to explain the accelerated expansion of the universe. This is a bit non-trivial, so one needs to be very careful to see if the model constructed is healthy. Along this line, I have constructed an Extended Minimally theory of Massive Gravity, and an interacting vector dark energy model, interacting scalar dark energy models, etc.

I am also looking for new models inspired by both observations and fundamental principles.

Testing Gravity

Until now, there has been a plethora of dark energy models and modified gravity models. The crowning glory of a theory is to pass the experimental/observational test. In the recent years, there has been a huge number of cosmological and astrophysical data (both from the electromagnetic wave window and gravitational wave window) available to test a theoretically healthy dark energy theory or modified gravity theory.

My second research interest is to confront different theories of gravity with cosmological data, such as cosmic microwave background radiation, and large-scale structure data. I have worked on putting constraints to various theories of gravity such as generalised proca theory, massive gravity, minimally modified gravity theories and so on. I am experienced in modifying Einstein-Boltzmann code (CLASS) to test these models.

In the coming years, there will be an enormous amount of data coming from EUCLID, and LSST with unprecedented accuracy and precision. I am looking to test theories of gravity at non-linear scales with the upcoming data.

Cosmological Tension

As the cosmological data becomes more and more accurate some discrepancies/mismatches in the estimation of crucial parameters of our universe assuming standard LCDM model. The most crucial such mismatches are in the estimation of the Hubble expansion rate today (H0), and amplitude of fluctuations (S8) from different observations. This is an additional crisis that cannot be ignored by the cosmologists today. If there are no systematics in the observations, then this issue invites us to discover new physics in the cosmos.

One of my research interests is to address the tensions in cosmology, particularly, the Hubble tension and the S8 tension. I have proposed late-time solutions to the Hubble tension using modified theories of gravity. I have also built new interacting dark sector models, in the context of scalar dark energy and vector dark energy, hoping that it can address both Hubble tension and S8 tension.

I am also interested in studying different models, that have potential to address cosmological tensions.

1

2

3

My
Publications

Here are my list of publications.

To see my full publications, please visit my INSPIRE profile INSPIRE
  1. Baryon Physics and Tight Coupling Approximation in Boltzmann Codes
    Masroor C. Pookkillath, Antonio De Felice, Shinji Mukohyama and M.C. Pookkillath
    arXiv:1906.06831 Universe 6 (2019) 1, 6
  2. Modified theory of gravity and clustering of multi-component system of galaxies
    Mir Hameeda, Behnam Pourhassan, Mir Faizal, C.P. Masroor, Rizwan Ul Haq Ansari, P.K. Suresh
    arXiv:1911.01739, Eur.Phys.J.C 79 (2019) 9, 769
  3. Reducing the H0 tension with generalized Proca theory
    Antonio De Felice, Chao-Qiang Geng, Masroor C. Pookkillath, Lu Yin
    arXiv:2002.06782, JCAP 08 (2020) 038.
  4. Anisotropic instability in a higher order gravity theory
    Masroor C. Pookkillath, Antonio De Felice, Alexei A. Starobinsky
    arXiv:2004.03912, JCAP 07 (2020) 041.
  5. Minimally modified gravity fitting Planck data better than ΛCDM
    Katsuki Aoki, Antonio De Felice, Shinji Mukohyama, Karim Noui, Michele Oliosi, Masroor C. Pookkillath
    arXiv:2005.13972, Eur.Phys.J.C 80 (2020) 8, 708.
  6. Addressing H0 tension by means of VCDM
    Antonio De Felice, Shinji Mukohyama, Masroor C. Pookkillath
    arXiv:2009.08718, Phys.Lett.B 816 (2021) 136201.
  7. Disformal map and Petrov classification in modified gravity
    Jibril Ben Achour, Antonio De Felice, Mohammad Ali Gorji, Shinji Mukohyama, Masroor C. Pookkillath
    arXiv:2107.02386, JCAP 10 (2021) 067.
  8. Minimal theory of massive gravity and constraints on the graviton mass
    Antonio De Felice, Shinji Mukohyama, Masroor.C. Pookkillath
    arXiv:2110.01237, JCAP 12 (2021) 12, 011.
  9. Minimally Modified Gravity Fitting Planck Data Better Than ΛCDM
    Masroor C. Pookkillath
    Astron.Rep. 65 (2021) 10, 1021-1025.
  10. Static, spherically symmetric objects in type-II minimally modified gravity
    Antonio De Felice, Shinji Mukohyama, Masroor C. Pookkillath
    arXiv:2110.14496, Phys.Rev.D 105 (2022) 10, 104013.
  11. Comparison of two theories of Type-IIa minimally modified gravity
    Antonio De Felice, Kei-ichi Maeda, Shinji Mukohyama, Masroor C. Pookkillath
    arXiv:2110.14496, Phys. Rev. D 106 (2022) 024028.
  12. Extended minimal theories of massive gravity
    A. De Felice, S. Mukohyama and M.C. Pookkillath
    arXiv:2206.03338, Phys. Rev. D 106 (2022) 084050.
  13. Gravitational collapse and formation of a black hole in a type II minimally modified gravity theory
    Antonio De Felice, Kei-ichi Maeda, Shinji Mukohyama, Masroor C. Pookkillath
    arXiv:2211.14760, JCAP 03 (2023) 030.
  14. The Lunar Gravitational-wave Antenna: Mission Studies and Science Case
    Parameswaran Ajith, Pau Amaro Seoane, Manuel Arca Sedda, Riccardo Arcodia, et al.
    arXiv:2404.09181.
  15. CMB spectrum in unified EFT of dark energy: scalar-tensor and vector-tensor theories
    Katsuki Aoki, Mohammad Ali Gorji, Takashi Hiramatsu, Shinji Mukohyama, Masroor C. Pookkillath, Kazufumi Takahashi
    arXiv:2405.04265, JCAP 07 (2024) 056.
  16. Theory of interacting vector dark energy and fluid
    Masroor C. Pookkillath, Kazuya Koyama
    arXiv:2405.06565.
  17. G3 -- interacting scalar tensor dark energy
    Masroor C. Pookkillath, Nandan Roy
    arXiv:2408.02538.
You can also see my list of publication, click Publication List

My
Activities

Here I show the activities I am involved in that motivate me
to follow my passion.

  • Cosmology Seminar

    Organiser [20 October 2022 - Present]

    This is a fortnight event, Tuesday at 2.00 PM, by the cosmology group at the Centre for Theoretical Physics and Natural Philosophy, where the speaker presents progress on his/her research before the group members. We are having a very good time with it.

    Details

  • Reading Club @ CTPNP

    Organiser [20 October 2022 - Present]

    This is an informal activity, where the cosmology group at CTPNP choose a book on advanced subjects in gravity and field theory. The aim is to brush up our basic knowledge and expose the group to advanced knowledge, in the end, it would help in our research.

    CTPNP

  • Reading Club @ YITP

    Organiser

    The idea of the reading club was already there at Yukawa Institute, where I did my PhD. I spend more than three years in YITP and we almost finished six books in that period. At some point, the duty of organizing the reading club happened to be my responsibility and I was enjoying it. Now, I am not present at YITP to run it.

    YITP

  • Gravity 2023: Dawn of Field-theoretic Approach

    Organiser [18 July 2023 - 20 July 2023]

    This workshop aims to bring together experts working on field-theoretic approaches applied to gravity to share ideas and expertise and to offer introductory talks to teach these state-of-the-art subjects to a broader audience. All talks (invited and contributed) are to be given on-site but the workshop will also be accessible to online audiences who cannot attend on-site.

    Workshop Page

  • Gravity: Current challenges in black hole physics and cosmology

    Organiser [20 June 2022 - 01 July 2022]

    The goal of the workshop is to bring together experts working on several aspects of the gravitational interaction to share ideas and expertise. It will include recent progress on modified gravity theories, black hole physics, and early and late-time cosmology. I have been a part of organising this event. It was an interesting experience and I learned a lots of lessons.

    Workshop Page

  • ICTS, Bangalore, India

    Extended minimal theories of massive gravity.

    April 23, 2023

    I gave this talk on a visit to the Astrophysical Relativity research group at the International Center for Theoretical Science (ICTS), Bangalore. I also attend an interesting one-week discussion on the Lunar Gravitational-wave Antenna (LGWA), which is an ambitious proposal to detect deci-hetz band GWs. I met great people working on gravitational wave astronomy and made a very good interaction.

    Visit the group

  • Department of Physics, Tokyo Institute of Technology

    VCDM and Cuscuton

    October 12, 2022

    This talk was given before the cosmology and gravity group at the Tokyo Institute of Technology, Tokyo, Japan. The presentation of my results on comparing two theories: VCDM and Cuscuton. The talk was pedagogical since there was participation from Master's students.

    Visit the group

  • NAS Workshop 2022

    VCDM: Minimal theory of gravity

    September 15-18, 2022

    This workshop is CTPNP internal event, where researchers from Thailand meet and discuss, the research topics and make a very relaxed environment. This workshop promotes and gives an environment to make new collaborations on our interesting research themes. In this event, I was given a chance to introduce my work on a Minimally Modified Gravity Theory called VCDM.

    More on NAS workshop

  • On the edge of what we know?

    The 2nd CAFÉ FICICA, Good Old days cafe & bistro, Nakhon Sawan

    5 August, 2023

    This is my second formal outreach activity and was a very amazing event. After the talk, there was a panel discussion together with Prof. Shinji Tujikawa and Prof. Burin Gumjudpai. The public asked many interesting questions about cosmology and the limitations of present understanding. The audience also included very eminent people like the local governor of the Nakhon Sawan province. He got impressed by this event and said, he will support such events in future. Here are some news links for it.

    CAFÉ FICICA

  • Understanding our Universe: Current status

    Department of Physics, MES Ponnani College, Ponnani, India

    27 June, 2022

    This is my first outreach activity. I was addressing Undergraduate students in a community college in a a small town called Ponnani in Kerala, India. The basic idea is to give motivation to students who are mostly women and to introduce research to them. This was a very memorable moment for me to make a presentation in this college, where I was a student a few years back.

    Visit College

Useful
Tools

Here are some of the tools I use every day. Some of them are scientific tools, such as Mathematica, while others are more general tools that can help you manage projects and track your work time. This section will be updated as I become more familiar with each tool. My list will be updated if I discover any new tools that are useful.

  • xAct is a symbolic tensor algebra package written in Wolfram Language. This is useful in constructing Lagrangians from tensor objects and deriving covariant equations of motion. There are many other possibilities one can do with this package, for example, one can perform the Dirac algorithm and count degrees of freedom in complicated theories. With xCoba, one can also perform component calculations, given any metric for theory under consideration. There are many good examples one can find online, for example, click here. Here are some of my examples useful for cosmological perturbation.

  • The Cosmic Linear Anisotropy Solving System (CLASS) is an Einstein-Boltzmann code written in the C language. It calculates the evolution of cosmological linear perturbation and compares the observables from Cosmic Microwave Background Radiation (CMB) and Large Scale Structure. Tools like this are highly important for the cosmological tests of theories of gravity. Using this, I have constrained different theories of gravity. The basics of cosmological perturbation theory are explained in the paper by Ma and Bershinger. To learn more about the approximation schemes, one can go through, the CLASS-II paper.

  • Superproductivity is a great tool for tracking how long you spend on your work. I like using this tool because it gives an idea of how much time I spend on my work. This helps me to limit myself to deviate from work. In addition, this application helped me understand how long it may take to complete a task. The best thing is that if you are disconnected from the task, you will be informed.

  • Trello is a working management tool. I use this tool to illustrate my project workflow. This gives a good idea of how each project progresses and what immediate steps should be taken next. You can find many interesting features for effective work management. With this tool, I learned how to organize my own projects.

Contact
Address

Centre for Theoretical Physics & Natural Philosophy
“Nakhonsawan Studiorum for Advanced Studies”
Mahidol University, Nakhonsawan Campus, 402/1 Moo 5 Khaothong, Phayuha Khiri, Nakhonsawan, Thailand 60130
You can reach me at
masroorcp@gmail.com
masroor.cha@mahidol.ac.th

Say Hello



Form submitted successfully!