Subhankar Roy

Assistant Professor

MSc (Gauhati) PhD (Gauhati)

High Energy Physics

Department of Physics
Gauhati University, Guwahati, 781014
Email: subhankar[at]gauhati[dot]ac[dot]in

Dr. Subhankar Roy has been serving as an Assistant Professor in the Department of Physics at Gauhati University, Guwahati, since July 30, 2016.

Email id:  subhankar@gauhati.ac.in

Qualification

  • Ph.D. in Physics, Gauhati University, 2016
  • MSc in Physics, Gauhati University, Guwahati, 2009

Specialization: High Energy Physics

Professional Experience

  • Research Experience: Over twelve years (From April 2010 onwards.)
  • Teaching Experience: Over seven years (From August 2016 onwards)

 Courses taught:

  • First semester: Mathematical Physics, Quantum Mechanics
  • Third Semester: High Energy Physics-I, Advanced Mathematical Physics
  • Fourth Semester: High Energy Physics-II, Advanced Quantum Mechanics.

Research Area:

My current research focuses on Neutrino Physics, a fundamental component of contemporary Particle Physics. Specifically, my research areas include: 

  • The parametrization of neutrino mass and mixing matrices, study of lepton mass matrix Texture.
  • Thought experiments related to Neutrino oscillation and quantum mechanics.
  • Understanding the neutrino masses and mixing through Discrete Flavour symmetry groups using Type I, Type II and Hybrid Seesaw.
  • Investigating the lepton mass matrices from a unification perspective.
  • Renormalization Group equations.
  • Baryogenesis
  • Understanding the neutrino masses in composite models.

Future Prospects:

  • Explore Quark and Lepton mixing matrices within the unification framework, identifying common parameters in both sectors.
  • Develop innovative composite models to address the unsolved issues in particle physics.
  • Gain a deep understanding of Neutrino oscillation from a quantum-field theoretical perspective.
  • Propose alternative models beyond the traditional seesaw mechanism

 

 

 

 

 

 

 

 

  1. M. Dey, S. Roy, Revisiting the Dirac nature of neutrinos in the light of Δ(27) and cyclic symmetries, J.Phys.G 52 (2025) 2, 025005. arXiv: 2403.12461.
  2. P. Chakraborty, M. Dey, B. Karmakar, S. Roy, Neutrino mixing from a fresh perspective, Phys. Lett. B 858 (2024), 139020. arXiv: 2405.10353.
  3. M. Dey, S. Roy, A realistic neutrino mixing scheme arising from A_4  symmetry, Euro Phys. Lett 147 (2024) 1, 14002.  arXiv:2304.07259. 
  4. P. Chakraborty, M. Dey, S. Roy, Constrained neutrino mass matrix and Majorana phases, J. Phys. G 51 (2024) 015003. arXiv:2202.04874.
  5. P. Chakraborty, S. Roy, Confined neutrino oscillation, Phys. Lett. A 484 (2023) 129070. arXiv:2205.05400. doi:10.1016/j.physleta.2023.129070. 
  6. P. Chakraborty, S. Roy, The other variants of mixed μ-τ symmetry, Nucl. Phys. B 992 (2023)116252. arXiv:2304.06737. doi:10.1016/j.nuclphysb.2023.116252.
  7. M. Dey, P. Chakraborty, S. Roy, The μ-τ mixed symmetry and neutrino mass matrix, Phys. Lett. B 839 (2023) 137767. arXiv:2211.01314. doi:10.1016/j.physletb.2023.137767.
  8. S. Roy, S.T. Goswami, Leptons and other forces of nature, J. Phys. G 49 (11) (2022) 115005. arXiv:2106.06045. doi:10.1088/1361-6471/ac94ea. 
  9. S. Roy, K. Sashikanta Singh, J. Borah, Revamped Bi-Large neutrino mixing with Gatto-Sartori-Tonin like relation, Nucl. Phys. B 960 (2020) 115204. arXiv:2001.07401. doi:10.1016/j.nuclphysb.2020.115204. 
  10. S. Singh, S. Roy, N. N. Singh, Stability of neutrino parameters and self-complementarity relation with varying SUSY breaking scale, Phys. Rev. D 97 (5) (2018) 055038. arXiv:1802.09784. doi:10.1103/PhysRevD.97.055038. 
  11. M. Bora, S. Roy, N. N. Singh, Leptogenesis in quasi-degenerate neutrino mass models with non-zero 13, Canadian Journal of Physics 96 (1) (2018) 71–80. doi.org/10.1139/cjp-2016-0964, doi:10.1139/cjp-2016-0964. 
  12. S. Roy, S. Morisi, N. N. Singh, J. W. F. Valle, The Cabibbo angle as a universal seed for quark and lepton mixings, Phys. Lett. B 748 (2015) 1–4. arXiv:1410.3658, doi:10.1016/j.physletb.2015.06.052. 
  13. S. Roy, N. N. Singh, Modulated bimaximal neutrino mixing, Phys. Rev. D 92 (3) (2015) 036001.arXiv:1603.07972, doi:10.1103/PhysRevD.92.036001. 
  14. S. Roy, N. N. Singh, Mixing angle as a function of neutrino mass ratio, Phys. Rev. D 91 (9)(2015) 096003. arXiv:1603.07474. doi:10.1103/PhysRevD.91.096003. 
  15. S.Roy, N. N. Singh, Bi-Large neutrino mixing with charged lepton correction, Indian J. Phys.88 (5) (2014) 513–519. arXiv:1211.7207, doi:10.1007/s12648-014-0446-1.
  16. S. Roy, N. N. Singh, A model-independent investigation on quasi-degenerate neutrino mass models and their significance, Nucl. Phys. B 877 (2013) 321–342. arXiv:1603.07246. doi:10.1016/j.nuclphysb.2013.10.011.
  17. S. Roy, N. N. Singh, Expansion of U_{PMNS}  and Neutrino mass matrix M_{\nu} in terms of  \sin\theta_{13} for Inverted Hierarchical case, J. Mod. Phys. 4 (2013) 495. arXiv:1210.5339. doi:10.4236/jmp.2013.44070.

Unpublished Works:

  1. Generating nonzero \theta_{13} without breaking the 2-3 symmetry of neutrino mass matrix, Authors: S. Roy and N. N. Singh. arXiv:1605.00809.
  2. Leptonic mixing matrix in terms of Cabibbo angle Authors: S. Roy and N. N. Singh. arXiv:1304.1994.

High Energy Physics

(Uploaded between 28 th September 2020- 17 th August, 2021)

   Video Lectures  

  1. Lecture 1 (Klein Gordon Equation)
  2. Lecture 2 (Dirac Equation)
  3. Lecture 3 (Special Features of Dirac Equation: Part 1, Part 2, Part 3, Part 4 )
  4. Lecture 4 (Dirac Spinor, Four vector, Lorentz scalars: Part 1, Part 2, Part 3, Part 4 )
  5. Lecture 5 (Helicity and Chirality Operators: Part 1, Part 2, Part 3, Part 4)
  6. Lecture 6 (Pseudo Scalar Part 1, Part 2, Part 3)
  7. Lecture 7 (Pseudo Vector Part 1, Part 2, Part 3)
  8. Lecture 8 (Infinite Quantum Harmonic Oscillators Part 1, Part 2, Part 3)
  9. Lecture 9 (Maxwell's equation and infinite Harmonic Oscillators: Part 1, Part 2, Part 3, Part 4, Part 5)

 Class Notes

The following class notes cover the discussion on the Natural Unit system, Maxwell's equation, Proca equation, Lorentz gauge and other gauges, Noether's theorem, Conserved charges, Conserved currents, Spontaneous Symmetry breaking, Goldstone theorem, Local gauge theory, Electroweak symmetry, Higgs Mechanism, Electromagnetic interaction, weak interaction, Discrete symmetries and Quark Model, etc.

Lecture 10 Lecture 11 Lecture 12 Lecture 13 Lecture 14 Lecture 15
Lecture 16 Lecture 17 Lecture 18 Lecture 19 Lecture 20 Lecture 21
Lecture 22 Lecture 23 Lecture 24 Lecture 25 Lecture 26 Lecture 27
Lecture 28 Lecture 29 Lecture 30 Lecture 31 Lecture 32 Lecture 34
Lecture 35 Lecture 36 Lecture 37 Lecture 38 Lecture 39 Lecture 40
Assignment -1 Assignment -2 Assignment-3 Assignment-4 Assignment-5  

 

Video Lectures on the Quark Model (For High Energy Physics/ Advanced Mathematical Physics)

(Uploaded between 26th March to 29th July, 2020)

  1. Lecture 1 (Motivation)
  2. Lecture 2 (Pattern and Group Theory) + Lecture Note 2
  3. Lecture 3 (A Simpler Quark Model) + Lecture Note 3
  4. Lecture 4 (Baryon wave function and color quantum number) +Lecture Note 4
  5. Lecture 5 (Color Quantum number) + Lecture Note 5
  6. Lecture 6 (Conjugate Representation) + Lecture Note 6
  7. Lecture 7 (Mesons) + Lecture Note 7
  8. Lecture 8 (Essentials of SU(3) group)  + Lecture Note 8
  9. Lecture 9 (Octet and Decuplet) + Lecture Note 9
  10. Lecture 10 (Shift Operators of SU(3))

 

Advanced Quantum Mechanics

(Uploaded between 6th May, 2021- 17 th August, 2021)

Video Lectures

  1. Lecture 1 (Introduction to Relativistic Quantum Mechanics): Part 1, Part 2, Part 3  + Lecture note
  2. Lecture 2 (Four-vector and Klein Gordon Equation): Part 1, Part 2 + Lecture note

Class Notes

Lecture 3 Lecture 4 Lecture 5 Lecture 6 Lecture 7 Lecture 8 Lecture 9
Feynman interpretation Dirac Equation Dirac Matrices Dirac Equation and spin Energy Eigenstates -Part A Energy Eigenstates- Part B Helicity and Chirality-Part A
Lecture 10 Lecture 11 Lecture 12 Lecture 13 Assignment -1 Assignment -2  
Helicity and Chirality-Part B Transformation of Spinor Path Integral Formulation -Part A Path Integral Formulation -Part B      

 

(Uploaded between 11th April, 2020-  6th June, 2020)

Video Lectures

  1. Lecture 1 (Review of Dirac equation) + Lecture Slides
  2. Lecture 2 (Solution of Dirac equation -A) + Lecture Slides
  3. Lecture 3 (Solution of Dirac equation -B) + Lecture Slides
  4. Lecture 4 (Solution of Dirac equation -C) + Lecture Slides
  5. Lecture 5 (Helicity-A) + Lecture Slides
  6. Lecture 6 (Helicity -B) + Lecture Slides
  7. Lecture 7 (Gamma Matrices) + Lecture Slides + list of properties of Gamma matrices
  8. Lecture 8 (Chirality-A) + Lecture Slides
  9. Lecture 9 (Chirality-B) + Lecture Slides
  10. Lecture 10 (Lorentz transformation) + Lecture Slides
  11. Lecture11 (Miscellaneous issues related to RQM ) + Lecture Slides
  12. Lecture 12 (Classical radius and Compton's wavelength of electron) + Lecture Slides

 

Advanced Mathematical Physics

(Uploaded between 20th September- 2020- 9th December, 2020)

Video Lectures

  1. Lecture 2: Lie Algebra
  2. Lecture 3: Transformation of Particles and Antiparticles
  3. Lecture 4: Generators in Operator form
  4. Lecture 5: Generators of SU(2) in Operator form
  5. Lecture 7: Finite Group Revisited Part 1, Part 2, Part 3
  6. Lecture 8: Important definitions related to representations Part1, Part 2, Part 3
  7. Lecture 9: Reducibility and Schur's Lemna Part 1, Part 2
  8. Lecture 10 Character Orthogonality Part 1, Part 2, Part 3
  9. Lecture 11 Criteria of Reducibility Part 1, Part 2, Part 3, Part 4
  10. Lecture 12 Character Table and Applications Part 1, Part 2
  11. Lecture 13 Kronecker Product Representation Part 1, Part 2

 

Class Notes

Lecture Note 1 Lecture Note 2

Lecture Note 3

 Lecture Note 4
Lie group and generators Lie Algebra Transformation of Particles and Antiparticles Generators in Operator Form
Lecture Note 6 Assignment 1 Assignment 2 Assignment 3
Adjoint Representation      
Assignment 4      

 

Mathematical Physics 

(Uploaded between 31st December- 2020- 1st April, 2021)

Class Notes (Linear Vector space)

Lecture Note 1 Lecture Note 2 Lecture Note 3
Lecture Note 4 Lecture Note 5 Lecture 6-7
Lecture Notes 8-9    

 

Facilities & Resources

Facilities
Resources
Some Important Links (Outside GU)