arXiv subjects

Suraj Kumar Rai

Publications and source records attributed to Suraj Kumar Rai.

5 recordsLinked to original sources

arXiv2025

Comparative analysis of critical regions: The renormalized quark-meson model under Polyakov loop, quark back-reaction, and vector interaction effects

The critical regions enveloping the critical end point (CEP) in the $\mu$-$T$ plane are mapped by computing the contours of normalized quark number susceptibility within the on shell renormalized 2+1 flavor quark-meson (RQM) and Polyakov loop enhanced renormalized Polyakov quark meson (RPQM) models for $m_\sigma = 400$ and 500 MeV.The apparent precision for the results of CEP coordinates merely reflects numerical binning of two decimal places rather than the effect of including full thermal and vacuum quantum fluctuations. The renormalized 't Hooft coupling c becomes substantially stronger in the RQM model when the meson self energies due to quark loops are computed using the pole masses of mesons and parameters are fixed on shell in Ref [143] after a consistent treatment of quark one loop vacuum fluctuations while the light and strange chiral symmetry breaking strengths also become weaker. We evaluate the impact of these novel features on critical fluctuations. Furthermore, the improved PolyLog glue form of the Polyakov loop potential from Ref [46] is employed to isolate the effects of the quark back reaction on critical fluctuations, and the results are contrasted against back reaction free outcomes obtained using the logarithmic potential. Utilizing inputs from large $N_c$ standard chiral perturbation theory, phase diagrams are also computed in the light chiral limit ($m_\pi = 0$), quantifying the proximity of the tricritical point (TCP) to the CEP. The critical regions from the RQM/RPQM models are compared with those reported in Ref [120], where curvature masses are used for parameter fixing. Phase diagrams incorporating vector interactions in the RQM/RPQM model reveal that the CEP and first-order transition survive up to a robust coupling of $g_\omega = 2.79$, rendering them highly relevant for compact star equations of state and astrophysical phenomenology.

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arXiv2023

Phase structure of the on-shell parametrized 2+1 flavor Polyakov quark-meson model

Augmenting the improved chiral effective potential of the on-shell renormalized 2+1 flavour quark-meson (RQM) model with the Polyakov-loop potential that accounts for the deconfinement transition,~we get the Quantum Chromodynamics (QCD) like framework of the renormalized Polyakov quark-meson (RPQM) model.~When the divergent quark one-loop vacuum term is included in the effective potential of the quark-meson (QM) model,~its tree level parameters or the parameters fixed by the use of meson curvature masses,~become inconsistent as the curvature masses involve the self energy evaluations at zero momentum.~Using the modified minimal subtraction method,~the consistent chiral effective potential for the RQM model has been calculated after relating the counterterms in the on-shell (OS) scheme to those in the $\overline{\text{MS}}$ scheme and finding the relations between the renormalized parameters of both the schemes where the physical (pole) masses of the $π, K, η$ and $η^{\prime}$ pseudo-scalar mesons and the scalar $σ$ meson,~the pion and kaon decay constants,~have been put into the relation of the running couplings and mass parameter.~Using the RPQM model and the PQM Model with different forms for the Polyakov-loop potentials in the presence or the absence of the quark back-reaction,~we have computed and compared the effect of the consistent quark one-loop correction and the quark back-reaction on the scaled chiral order parameter,~the QCD phase diagrams and the different thermodynamic quantities.~The results have been compared with the 2+1 flavor lattice QCD data from the Wuppertal-Budapest collaboration \{JHEP 09,73(2010); PLB 730,99(2014)\} and the HotQCD collaboration \{PRD 90,094503(2014)\}.

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arXiv2023

Thermodynamics and phase diagrams of the Polyakov quark-meson model with on-shell versus curvature mass parameter fixing

The Quantum Chromodynamics (QCD) phase structure has been studied using the Polyakov-loop augmented quark-meson model (PQM) in the extended mean field approximation (e-MFA) where the quark one-loop vacuum term is included.~When the divergent vacuum term is regularized in the minimal subtraction scheme and the curvature meson masses are used to fix the parameters,~the Polyakov quark-meson model with the vacuum term (PQMVT) becomes inconsistent as the curvature masses are determined by calculating the self energies at zero momentum.~The above inconsistency is remedied by the on-shell parameter fixing when the pion decay constant and the pole masses of the mesons are put into the relation of the couplings and running mass parameter by using the on-shell and the minimal subtraction renormalization scheme.~Combining the modified chiral effective potential of the on-shell renormalized quark-meson model (RQM) with the Polyakov-loop potential that mimics the physics of the confinement-deconfinement transition,~we get the renormalized Polyakov quark-meson (RPQM) model.~The phase diagrams and the thermodynamics details for the PQM, PQMVT and RPQM model, have been computed and compared for different forms of the Polyakov-loop potentials with and without the quark back-reaction.~The results have also been compared with the available lattice QCD data.~The so called quarkyonic phase region in the phase diagram, where the chiral symmetry is restored but the quarks and anti-quarks are still confined,~gets reduced by the quark back-reaction in the unquenched Polyakov-loop potential.~It altogether disappears for the chemical potential dependent parameter $T_{0} \equiv T_{0} (μ)$ in the Log or the PolyLog-glue form of the Polyakov-loop potential in the RPQM model.

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arXiv2022

On-shell versus curvature mass parameter fixing schemes in the quark-meson model and its phase diagrams

We compute and compare the effective potential and phase structure for the quark-meson model in an extended mean-field approximation (e-MFA) when vacuum one loop quark fluctuations are included and the model parameters are fixed using different renormalization prescriptions.When the quark one loop vacuum divergence is regularized under the minimal subtraction scheme,the model setting of the parameter fixing using the curvature masses of the scalar and pseudo-scalar mesons, has been termed as the quark-meson model with the vacuum term(QMVT).However,this prescription becomes inconsistent when we notice that the curvature mass is akin to defining the meson mass by the self-energy evaluation at vanishing momentum.In this work,we apply the recently reported exact prescription of the on-shell parameter fixing,to that version of quark-meson (QM) model where the two quark flavors are coupled to the eight mesons of the $ SU(2)_{L} \times SU(2)_{R} $ linear sigma model with iso-singlet $ σ$ ($η$),iso-triplet $ \vec{a_{0}} $ ($ \vecπ $) scalar(pseudo-scalar) mesons.The model then becomes, the renormalized quark-meson (RQM) model where physical (pole) masses of mesons and pion decay constant, are put into the relation of the running mass parameter and couplings by using the on-shell and the minimal subtraction renormalization schemes.The vacuum effective potential plots,the phase diagrams and the order parameter temperature variations for both the RQM model and QMVT model,are exactly identical for the $m_σ=$616 MeV.The effective potential is deepest in the QMVT model for $m_σ< $ 616 MeV and it becomes deepest in the RQM model when $m_σ> $616 MeV.

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arXiv2020

Exploring axial $U(1)$ restoration in a modified 2+1 flavor Polyakov quark meson model

We report on the $U_{A}(1)$ symmetry restoration resulting due to temperature dependence of the coefficient c(T) for the Kobayashi-Maskawa-'t Hooft determinant (KMT) term in a modified 2+1 flavor Polyakov loop quark meson model having fermionic vacuum correction term (PQMVT).Temperature dependence of KMT coupling c(T) drives the non-strange condensate melting to significantly smaller temperatures in comparison to the constant c case.Further due to c(T), $m_{η^{\prime}}$ decreases from its vacuum value by 220 MeV near T=176 MeV after the chiral transition ($T_{c}^χ=154.9$ MeV).This is similar to the $η^{\prime}$ in-medium mass drop of at least 200 MeV as reported by Csorgo and Vertesi in Ref (Phys Rev Lett 105:182301,2010; Phys Rev C 83:054903,2011), as an experimental signature of the effective restoration of $U_A(1)$ symmetry. The pseudoscalar mixing angle $θ_p$ achieves anti-ideal mixing in the influence of c(T). The $η$ meson becomes light quark system ($ η_{NS} $) at T=176 MeV and changes its identity with $ η' $ meson which becomes strange quark system ($ η_{S} $). The degenerated temperature variations of $σ$, $π$ meson masses merges with the temperature variations of the masses of degenerated $a_{0}$, $η$ mesons near 275 MeV. It means that for c(T) when $m_σ=400$ MeV, the $U_{A}(1)$ restoration takes place at 1.75 $T_{c}^χ$=275 MeV.

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