Qualification:
Ph.D, MSc
v_sreekanth@cb.amrita.edu

Dr. Sreekanth V. currently serves as Assistant Professor in Physics, Department of Sciences, School of Engineering, Coimbatore. Dr. Sreekanth is a theoretical physicist and his research is mainly on the properties of hot and/or dense nuclear matter, such as, Quark-Gluon Plasma created in the relativistic heavy-ion collision experiments and cold nuclear matter inside neutron stars. His research has highlighted the effect of dissipation, particularly due to shear and bulk viscosities, on such systems.

Prior to joining Amrita, Dr. Sreekanth was a post-doctoral fellow at Center for High Energy Physics, Indian Institute of Science (IISc), Bangalore (2014-2017). Before that he was pursuing post-doctoral studies at Department of Theoretical Physics, Tata Institute for Fundamental Research (TIFR), Mumbai (2012-2014). Dr. Sreekanth obtained his Ph. D. in Theoretical Physics from Physical Research Laboratory (PRL), Ahmedabad (2012), where his research work in theoretical high energy nuclear physics had resulted in the thesis- "Properties of strongly interacting matter under extreme conditions". He did his postgraduate studies in Physics at IIT Madras.

His research areas include Quark-Gluon Plasma, Relativistic Dissipative Hydrodynamics, Relativistic Heavy Ion Collisions and Nuclear Astrophysics.

Dr. Sreekanth also has an academic interest in many aspects of Indology.

## Affiliation(s)

• October 2017 – Now: Assistant Professor – Department of Sciences, Amrita Vishwa Vidyapeethom, Coimbatore
• August 2014 - July 2017: Post-Doctoral Fellow – Center for High Energy Physics, Indian Institute of Science (IISc), Bangalore
• April 2012- August 2014: Post-Doctoral Fellow – Department of Theoretical Physics, Tata Institute for Fundamental Research (TIFR), Mumbai
• February 2012- March 2012: Post-Doctoral Fellow – Theoretical Physics Division, Physical Research Laboratory (PRL), Ahmedabad

## Qualification

Year Degree/Program Institution
2012 Ph.D. Physical Research Laboratory(PRL), Ahmedabad
2005 M.Sc. Indian Institute of Technology Madrass (IITM), Chennai

## Awards, Certificates, Honors and Societies

1. Post-Doctoral Research Fellowship, CHEP, IISc (MHRD - Govt. of India), 2014–2017
2. Post-Doctoral Research Fellowship, TIFR (Department of Atomic Energy - Govt. of India), 2012–2014
3. Post-Doctoral Research Fellowship, PRL (Department of Space - Govt. of India), 2012
4. Fellowship for Doctoral Research, PRL (Department of Space - Govt. of India), 2006 –2011

## Research Interest

• Area of Interest
Dr. Sreekanth’s research is mainly on the properties of hot and/or dense nuclear matter, such as, Quark-Gluon Plasma created in the relativistic heavy-ion collision experiments and cold nuclear matter inside neutron stars. His research has highlighted the effect of dissipation, particularly due to shear and bulk viscosities, on such systems.
Dr. Sreekanth also has an academic interest in many aspects of Indology.
• Keywords :
• High Energy Nuclear & Particle Physics
• Quark-Gluon Plasma
• Dissipative Relativistic Hydrodynamics
• Relativistic Heavy Ion Collisions
• Nuclear Astrophysics

## Research Group

### Present Team

Dr. Sreekanth V.
Theoretical High Energy Nuclear & Particle Physics

Lakshmi J. Naik
Ph.D. scholar
Quark-Gluon Plasma

## Teaching

• UG Theory: 4
• Intermediate Mechanics
• Mechanics
• Engineering Physics
• PG/Ph.D Theory: 3
• Mathematical Physics I
• Mathematical Physics II
• Fundamentals of Plasma Physics
• UG Labs: 2
• General Physics Lab (BTech)
• General Physics Lab (Int MSc)
• PG Labs: 3
• Simulation Lab
• Computational Physics Lab

## Publications

### Publication Type: Journal Article

Year of Publication Title

2020

V. Chandra, Kurian, M., Naik, L. J., and V. Sreekanth, “Thermal dilepton production in collisional hot QCD medium in the presence of chromo-turbulent fields”, under review in Phys Rev D, 2020.[Abstract]

The effects of collisional processes in the hot QCD medium to thermal dilepton production from q\overline{q}q
q

annihilation in relativistic heavy-ion collisions have been investigated. The non-equilibrium corrections to the momentum distribution function have been estimated within the framework of ensemble-averaged diffusive Vlasov-Boltzmann equation, encoding the effects of collisional processes and turbulent chromo-fields in the medium. The analysis has been done by considering the realistic equation of state by employing a quasiparticle model for the thermal QCD medium. The contributions from the 2\rightarrow22→2 elastic scattering processes have been quantified for the thermal dilepton production rate. We have showed that the collisional corrections induce appreciable enhancement over the equilibrium dilepton spectra. A comparative study between collisional and anomalous contributions to the dilepton production rates has also been explored. The collisional contributions are seen to be marginal over that due to collisionless anomalous transport

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2017

V. Chandra and V. Sreekanth, “Impact of momentum anisotropy and turbulent chromo-fields on thermal particle production in quark-gluon-plasma medium”, The European Physical Journal C, vol. 77, p. 427, 2017.[Abstract]

Momentum anisotropy present during the hydrodynamic evolution of the Quark-Gluon Plasma (QGP) in RHIC may lead to the chromo-Weibel instability and turbulent chromo-fields. The dynamics of the quark and gluon momentum distributions in this case is governed by an effective diffusive Vlasov equation (linearized). The solution of this linearized transport equation for the modified momentum distribution functions lead to the mathematical form of non-equilibrium momentum distribution functions of quarks/antiquarks and gluons. The modifications to these distributions encode the physics of turbulent color fields and momentum anisotropy. In the present manuscript, we employ these distribution functions to estimate the thermal dilepton production rate in the QGP medium. The production rate is seen to have appreciable sensitivity to the strength of the anisotropy.

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2015

V. Chandra and V. Sreekanth, “Quark and gluon distribution functions in a viscous quark-gluon plasma mediumand dilepton production via q ̄q annihilation”, Phys. Rev. D, vol. 92, p. 094027, 2015.[Abstract]

Viscous modifications to the thermal distributions of quark-antiquarks and gluons have been studied in a quasi-particle description of the quark-gluon-plasma medium created in relativistic heavy-ion collision experiments. The model is described in terms of quasi-partons that encode the hot QCD medium effects in their respective effective fugacities. Both shear and bulk viscosities have been taken in to account in the analysis and the modifications to thermal distributions have been obtained by modifying the the energy momentum tensor in view of the non-trivial dispersion relations for the gluons and quarks. The interactions encoded in the equation of state induce significant modifications to the thermal distributions. As an implication, dilepton production rate in the qq¯ annihilation process has been investigated. The equation of state is found to have significant impact on the dilepton production rate along with the viscosities.

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2014

R. S. Bhalerao, Jaiswal, A., Pal, S., and V. Sreekanth, “Relativistic viscous hydrodynamics for heavy-ion collisions: A comparison between Chapman-Enskog and Grad’s methods”, Phys. Rev. C, vol. 89, p. 054903, 2014.[Abstract]

Derivations of relativistic second-order dissipative hydrodynamic equations have relied almost exclusively on the use of Grad's 14-moment approximation to write f(x,p), the nonequilibrium distribution function in the phase space. Here we consider an alternative Chapman-Enskog-like method, which, unlike Grad's, involves a small expansion parameter. We derive an expression for f(x,p) to second order in this parameter. We show analytically that while Grad's method leads to the violation of the experimentally observed 1/mT−−−√ scaling of the longitudinal femtoscopic radii, the alternative method does not exhibit such an unphysical behavior. We compare numerical results for hadron transverse-momentum spectra and femtoscopic radii obtained in these two methods, within the one-dimensional scaling expansion scenario. Moreover, we demonstrate a rapid convergence of the Chapman-Enskog-like expansion up to second order. This leads to an expression for δf(x,p) which provides a better alternative to Grad's approximation for hydrodynamic modeling of relativistic heavy-ion collisions.

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2013

R. S. Bhalerao, Jaiswal, A., Pal, S., and V. Sreekanth, “Particle production in relativistic heavy-ion collisions: A consistent hydrodynamic approach”, PHYSICAL REVIEW C, vol. 88, no. 4, p. 044911, 2013.[Abstract]

We derive relativistic viscous hydrodynamic equations invoking the generalized second law of thermodynamics for two different forms of the nonequilibrium single-particle distribution function. We find that the relaxation times in these two derivations are identical for shear viscosity but different for bulk viscosity. These equations are used to study thermal dilepton and hadron spectra within longitudinal scaling expansion of the matter formed in relativistic heavy-ion collisions. For consistency, the same nonequilibrium distribution function is used in the particle production prescription as in the derivation of the viscous evolution equations. Appreciable differences are found in the particle production rates corresponding to the two nonequilibrium distribution functions. We emphasize that an inconsistent treatment of the nonequilibrium effects influences the particle production significantly, which may affect the extraction of transport properties of quark-gluon plasma.

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2012

J. R. Bhatt, Mishra, H., and V. Sreekanth, “Cavitation and thermal dilepton production in QGP”, Nuclear Physics A, vol. 875, pp. 181 - 196, 2012.[Abstract]

Abstract We study the effects of bulk and shear viscosities on both hydrodynamical evolution and thermal dilepton emission rate from the QGP phase at RHIC energies. We use lattice QCD inspired parametrization for the bulk viscosity and trace anomaly (equation of state) to describe behavior of the system near the critical temperature Tc. Ratio of the shear viscosity to entropy density is taken to be η/s∼1/4π. We calculate the corrections on the dilepton production rates due to modification in the distribution function, arising due to the presence of the bulk and shear viscosities. It is shown that when the system temperature evolves close to Tc the effect of the bulk viscosity on the dilepton emission rates cannot be ignored. It is demonstrated that the bulk viscosity can suppress the thermal dilepton spectra where as the effect of the shear viscosity is to enhance it. Further we show that the bulk viscosity driven fragmentation or cavitation can set in very early during the hydrodynamical evolution and this in turn would make the hydrodynamical treatment invalid beyond the cavitation time. We find that even though the finite bulk viscosity corrections and the onset of the cavitation reduce the production rates, the effect of the minimal η/s=1/4π can enhance the dilepton production rates significantly in the regime pT⩾2 GeV.

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2011

J. R. Bhatt, Mishra, H., and V. Sreekanth, “Shear viscosity, cavitation and hydrodynamics at LHC”, Physics Letters B, vol. 704, pp. 486 - 489, 2011.[Abstract]

Abstract We study evolution of quark–gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.

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2010

T. K. Jha, Mishra, H., and V. Sreekanth, “Bulk viscosity in a hyperonic star and $r$-mode instability”, PHYSICAL REVIEW C, vol. 82, p. 025803, 2010.[Abstract]

We consider a rotating neutron star with the presence of hyperons in its core, using an equation of state in an effective chiral model within the relativistic mean field approximation. We calculate the hyperonic bulk viscosity coefficient due to nonleptonic weak interactions. By estimating the damping timescales of the dissipative processes, we investigate its role in the suppression of gravitationally driven instabilities in the r-mode. We observe that r-mode instability remains very much significant for hyperon core temperature of around 108K, resulting in a comparatively larger instability window. We find that such instability can reduce the angular velocity of the rapidly rotating star considerably upto ∼0.04ΩK, with ΩK as the Keplerian angular velocity.

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2010

J. R.bhatt and V. Sreekanth, “Photon emission from out of equilibrium dissipative parton plasma”, International Journal of Modern Physics E, vol. 19, 2010.[Abstract]

Using the second order Israel–Stewart hydrodynamics we discuss the effect of viscosity on photon production in a parton plasma created in relativistic heavy ion collisions. We find that photon production rates can be enhanced by several factors due to the viscous effect in a chemically nonequilibrated plasma.

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2010

J. R. Bhatt, Mishra, H., and V. Sreekanth, “Thermal photons in QGP and non-ideal effects”, Journal of High Energy Physics, vol. 2010, p. 106, 2010.[Abstract]

We investigate the thermal photon production-rates using one dimensional boost-invariant second order relativistic hydrodynamics to find proper time evolution of the energy density and the temperature. The effect of bulk-viscosity and non-ideal equation of state are taken into account in a manner consistent with recent lattice QCD estimates. It is shown that the non-ideal gas equation of state i.e $ε$ − 3 P ≠ 0 behaviour of the expanding plasma, which is important near the phase-transition point, can significantly slow down the hydrodynamic expansion and thereby increase the photon production-rates. Inclusion of the bulk viscosity may also have similar effect on the hydrodynamic evolution. However the effect of bulk viscosity is shown to be significantly lower than the non-ideal gas equation of state. We also analyze the interesting phenomenon of bulk viscosity induced cavitation making the hydrodynamical description invalid. It is shown that ignoring the cavitation phenomenon can lead to erroneous estimation of the photon flux.

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2008

T. Jha, Moshra, H., and V. Sreekanth, “On attributes of a Rotating Neutron star with a Hyperon core”, Physical Review C, vol. 77, 2008.[Abstract]

We study the effect of rotation on global properties of neutron star with a hyperon core in an effective chiral model with varying nucleon effective mass within a mean field approach. The resulting gross properties of the rotating compact star sequences are then compared and analyzed with other theoretical predictions and observations from neutron stars. The maximum mass of the compact star predicted by the model lies in the range (1.4−2.4) M⊙ at Kepler frequency ΩK, which is consistant with recent observation of high mass stars thereby reflecting the sensitivity of the underlying nucleon effective mass in the dense matter EoS. We also discuss the implications of the experimental constraints from the flow data from heavy-ion collisions on the global properties of the rotating neutron stars.

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## Selected Invited Talks/ Seminars

• Dynamics of QCD matter 2018, NISER Bhubaneswar – August, 2019
• School of Physical Sciences, NISER Bhubaneswar – August, 2017
• Laboratory Nazionali del Sud INFN, Catania, Italy – October, 2016
• Istituto Nazionale di Fisica Nucleare (INFN) , Torino, Italy – October, 2016
• European Center for Theoretical Studies in Nuclear Physics and Related Areas (ECT*), Trento, Italy – September, 2016
• Ettore Majorana Foundation & Centre for Scientific Culture, Erice, Italy – September, 2016
• Centre for High Energy Physics, IISc Bangalore, India – September, 2015
• Tata Institute of Fundamental Research (TIFR), Mumbai, India – January, 2014
• Laboratori Nazionali di Frascati, INFN Rome, Italy – June, 2011
• Institut für Theoretische Physik, Technische Universität Wien, Vienna, Austria – June, 2011
• Institut für Kernphysik, Technische Universität Darmstadt, Germany – June, 2011
• Institute for Particle and Nuclear Physics (KFKI), Budapest, Hungary – May, 2011
• Tata Institute of Fundamental Research (TIFR), Mumbai, India – December, 2010
• Joint Institute for Nuclear Research (JINR), Dubna, Russia – August, 2010
• Physical Research Laboratory (PRL), Ahmedabad, India, March 2008

## Student Guidance

### Doctoral Students

• Studies on Non-equilibrium Quark-Gluon Plasma”, Lakshmi J. Naik, 2020 - Ongoing

### Master’s Students

• Expanding Quark-Gluon Plasma within Björken flow”, Lakshmi J. Naik(M.Sc), 2018
• “Relativistic Navier-Stokes Equation”, K. Sreelakshmi (Int. M.Sc.), 2018
• Bulk Viscous Cosmology”, Jyothilakshmi O. P. (Int. M.Sc.) , 2019
• Temperature & Relativistic Thermodynamics”, Sravan Krishnan P. E. (Int. M.Sc.) , 2019
• Bubble Dynamics: Rayleigh-Plesset Equation”, Malavika A. (M.Sc.), 2019
• Thermal Dilepton Production from q q̄-annihilation under Non-equilibrium Scenarios, Lakshmi J. Naik(M.Sc), 2020
• “Chemically Equilibrating QGP in Heavy Ion Collision”, K. Sreelakshmi (Int. M.Sc.), 2020
• “Hyperonic Bulk Viscosity”, Jyothilakshmi O. P. (Int. M.Sc.) , 2020 - Ongoing
• “Nuclear Equation of state & r-mode instability”, Sravan Krishnan P. E. (Int. M.Sc.), 2020 - Ongoing

### Bachelor’s Students (Int. M.Sc.)

• “Aspects of Five Dimensional Kaluza-Klein Theory”, Saradha S. (Int. M.Sc.), 2020
• “On Feynmans proof of Maxwell equations”, Udai Saidev (Int. M.Sc.), 2020
Faculty Research Interest: