Dr. Tabasum Rahnuma

I am a scientific researcher in the field of High Energy Physics (HEP). More precisely, my expertise lies in the fields of Gravitational and Black Hole physics alongside Celestial Holography.

I graduated in 2024 from the Indian Institute of Science Education and Research Bhopal (IISERB), India, with a PhD degree, where I had the privilege of working under the supervision of Dr. Nabamita Banerjee.

Now I have joined Asian Pacific Center for Theoretical Physics (APCTP), Pohang, as a postdoctoral researcher. I joined the group of Prof. Kanghoon Lee.

I like music and playing the Keyboard in my free time. Additionally, reading books is a part of my solitary hours.

Research

If an individual possesses a strong intellectual curiosity, particularly within the domain of science, it is imperative to initiate a path of scientific exploration. Research in science in not about solving the unsolved, it's all about observation.

I am currently studying gravity through the lens of holography. Specifically, I am engaged in Celestial Holography. Here I will explain briefly my field of research and list my research publications for reference.

Generically, the holographic principle proposes that the dynamics of a gravitational system in a certain number of spacetime dimensions can be described by a lower-dimensional theory without gravity living on its boundary. This concept is primarily introduced by Juan Maldacena in terms of AdS/CFT Correspondence in which a particular kind of quantum field theory called Conformal Field theory (CFT) emerged out of the gravity in curved anti-de Sitter (AdS) space whose boundary is a cylinder. However, unlike this our universe is asymptotically flat.

In particular, Celestial Holography descibes the physics of a four-dimensional asymptotically flat Minkowski spacetime in terms of the boundary quantum field theory. The bulk spacetime can be described in terms of the compactified Penrose diagram where the boundaries are null hypersurfaces with a sphere sitting at each point. In otherwords we can simply look at the sky to understand what is happening inside this four-dimensional world that we live in. This compactified spacetime preserves the conformal symmetry of the spacetime and in this regard we call the field theory on the sky of the spacetime to be Celestial Conformal Field Theory (CCFT), introduced by Strominger in 2017.

Yes, we have become Celestial Holographers.

In my recent works, we used the Celestial Conformal Field Theory (CCFT) formalism to find the asymptotic symmetries algebras of gauge theory coupled to graivty like Einstein-Yang-Mills and Einstein-Maxwells in (3+1) dimension. Along with we have explored more in the supersymmetric sector liket that in maximally supersymmetric N=8 Supergravity theory. The disjoint study of gravitational memory and asymptotic symmetries will give us more insights on the general theory of relativity and help us explore far in the past and future.

For a general knowledge regarding the holography, I recommend one QuantaMagazine article, how symmetries will help us explore the holographic universe. People can follow the references there itself in the article.

Recent Publications ( my iNSPIRE profile)

N. Banerjee, T. Rahnuma and R. K. Singh, Asymptotic Symmetry algebra of $\mathcal{N}=8$ Supergravity, Phys. Rev. D 109, 046010.
N. Banerjee, T. Rahnuma and R. K. Singh, Soft and collinear limits in $ \mathcal{N} = 8$ supergravity using double copy formalism, JHEP 04 (2023) 126.
N. Banerjee, T. Rahnuma and R. K. Singh, Asymptotic Symmetry of Four-Dimensional Einstein-Yang-Mills and Einstein-Maxwell Theory, JHEP01(2022)033.

Now, I would like the reader to delve more into my research and get motivated towards exploring this field of research. I will do this in an intriguing way. Hope visitors will enjoy the reading.

Celestial Secrecy

Direct detection of the gravitational waves set up a platform for the scientific community in Gravitational Wave Astronomy to investigate different aspects of gravity theories. One of the significant physical effects is called as Gravitational Memory effect. This will help us understand the properties of black hole spacetimes and gravitational waves. The peak sensitivity of LIGO and LISA detectors might capture the effect of memory's rise time during the merger and ringdown phases of a Binary Blackhole (BBH). In this direction, GW memory detection has had several implications in GW150914 through the LIGO detector.

Solving the Spacetime Riddle...

Asymptotically flat spacetimes refers to a type of spacetime geometry in which the curvature of spacetime becomes infinitely small at infinite distances from any massive objects. As we know symmetries are the transformations of fields that leave the physical observables invariant. In this sense asymptotic symmetries exist in the physical systems far away from the gravitational systems.

The passage of gravitational waves produces a permanent shift in the relative positions of a pair of inertial detectors. This effect is called Memory effect. Theoretically, this classical observable effect can be related to the quantum effects like soft theorems and the asymptotic symmetries. I will briefly explain these two quantum phenomena. This can be easily visible in the diagramatical interpretation of Strominger's IR triangle.

NOW, WHAT'S THE HYPE ABOUT INFRARED PHYSICS?

One primary way to probe nature's fundamental forces is to study Scattering processes. Here we want to understand the quantum gravitational scattering problems in the low energy regime. Soft theorems are the symmetry constraints of the scattering amplitudes in this regime. This is basically the low-energy sector of a scattering process. When we have a scattering process, there exist external particles of different energy scales. When we set the energy of one of the external particles to zero, we call that particle a soft particle. But the question is, what's the need to do that? In our observable universe, the asymptotic observer always sits at the infinities of the spacetime, which means at the asymptotic boundaries of the spacetime. Hence the information flow will only be possible via the messengers (which are photons in case of electromagnetic interaction of Electromagnetic Waves and gravitons in case of Gravitational interaction of Gravitational Waves). So the soft particles, in our case, are photons and gravitons. When we study one scattering process, we need to find the scattering amplitude. After taking one of the particles to be soft, we can write this higher point amplitude as a lower point amplitude multiplied by the universal soft factor. This is one incredible result from the Amplitude community because this theorem is independent of the theory we consider; the structure will be independent of the scattering pieces of information. Isn't this cool!! :)

The infinite symmetries of the four-dimensional asymptotically flat spacetime in both gauge and gravity theories lead us to the triangular relation between the memory effect, asymptotic symmetries, and soft theorems. Due to the passage of gravitational radiation, the difference in the initial and final spacetime geometries is related by a BMS supertranslation. The Ward identities of this invariance in Quantum Gravity (QG) are expressed as data representing gravitational radiation at null infinity. The recent uncovering of the relation between the on-shell physics of asymptotically flat theories and 2D CFT has proved to be a powerful tool. The boundary physics is captured by a 2D CFT (CCFT) of the conformal operators on the Celestial Sphere. Celestial amplitudes are of immense importance as an independent entity in itself. The infinite number of symmetries impose constraints on the celestial amplitude via Ward identities giving us the soft theorems. These constraints directly imply constraints on the bulk scattering amplitude. Hence a thorough understanding of celestial amplitudes can uncover new symmetries.

Notes

Here are some notes which could offer valuable assistance to researchers engaged in these specific areas of study:

1. Spinor Helicity Formalism

2. Gravitaional Waves and Memory Effects

Any possible suggestions for modifications and corrections to the notes are highly appreciated.

An interested reader will find the introduction to the study of Holographic Priniciples in My PhD Thesis. Introductory chapters of the thesis incorporates all of the detailed physics of symmetry studies of our holographic universe. All the required references are therein.

Academic History

Undergraduate

I completed my undergraduate degree in Physics at Utkal University, graduating with honors in Physics.

Masters

I earned my Master’s Physics from Utkal University, where I conducted research on theoretical high energy physics, and in the experimental data analysis sectors as one of my research project.

PhD

I completed my PhD in High Energy Physics at Dept of Physics, IISER Bhopal, India, focusing on the application of Celestial Holographic techniques to asymptotic symmetry analysis of different spacetimes. My dissertation, titled "Scattering in Asymptotically Flat Spacetimes and Symmetries from Holography," was supervised by Dr. Nabamita Banerjee and led to several publications in leading journals.

Postdoctoral (present)

I am going to join Asia Pacific Center For Theoretical Physics (APCTP), Pohang, South Korea, as a postdoctoral fellow. I will work with Prof Kangoon Lee there.

Contact Me

Email Id: trahnuma03@gmail.com

Office Tel: 0755-269-1250

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