arXiv subjects

Vivek Kumar Tiwari

Publications and source records attributed to Vivek Kumar Tiwari.

18 recordsLinked to original sources

arXiv2026

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 $μ$-$T$ 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 $m_σ= 400$ 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 ($m_π= 0$), 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 $g_ω= 2.79$, rendering them highly relevant for compact star equations of state and astrophysical phenomenology.

hep-ph↗

arXiv2026

Improved results of chiral limit study with the large $N_c$ standard U(3) ChPT inputs in the on-shell renormalized quark-meson model

When the $f_π, f_{K} \text{ and } M_η^2$ given by the $ (m_π,m_{K}) $ dependent scaling relations of the large $N_{c}$ standard U(3) Chiral perturbation theory (ChPT) and the infrared regularized U(3) ChPT,~are used in the on-shell renormalized 2+1 flavor quark-meson (RQM) model to find its parameters in the path to the chiral limit $(m_π,m_{K}) \rightarrow 0$ away from the physical point $ (m_π^{\text{\tiny{Phys}}},m_{K}^{\text{\tiny{Phys}}})=(138,496) $ MeV,~one gets the respective framework of RQM-S model and RQM-I model.~Computing and comprehensively comparing the RQM-S and I model Columbia plots for the $m_σ=400,500\text{ and }600$ MeV,~it has been shown that the use of large $N_c$ standard U(3) ChPT inputs give the better and improved framework for the Chiral limit studies as the RQM-S model tricritical lines show the expected saturation pattern after becoming flat in the vertical meson (quark) mass $μ-m_{K}$ ($μ-m_{s}$) plane for all the cases of $m_σ$ whereas the divergent RQM-I model tricritical line for the $m_σ=500$ MeV becomes strongly divergent when the $m_σ=600$ MeV.

hep-ph↗

arXiv2025

Comparison of chiral limit studies in curvature mass versus on-shell renormalized quark-meson model using ChPT

Consistent chiral limit has been investigated in the curvature mass parametrized quark-meson (QM) model with the quark one-loop vacuum term (QMVT) employing the infrared regularized Chiral perturbation theory (ChPT) predicted scaling of the pion,~kaon decay constants $f_π, f_{K} $ and $M_η^2 = m_η^2 + m_{η^{\prime}}^2 $ when the $π\ \text{and} \ K $ meson masses are reduced as one moves away from the physical point in the Columbia plot.~Comparing the QMVT model Columbia plots with the corresponding Columbia plots computed,~in the very recent work of Ref.~\cite{vkt25} using the on-shell renormalized QM (RQM) model and the earlier work of Ref.~\cite{Resch} using functional renormalization group techniques in the extended mean field approximation of QM (e-MFA:QM-FRG) model,~it has been estimated how the first, second and crossover chiral transition regions in the $m_π-m_{K}$($m_{ud}-m_{s}$) and the $μ-m_{K}$($μ-m_{s}$) planes,~get modified by different methods of implementing the quark one-loop vacuum fluctuations in the QM model.~Since both the e-MFA:QM-FRG and the QMVT model,~use curvature meson masses to fix the parameters and the dimensional regularization of vacuum divergences are incorporated equivalently,~the differences in their results can be attributed to different methods of approaching the chiral limit.

hep-ph↗

arXiv2024

Consistent chiral limit in on-shell renormalized quark-meson model with ChPT scaling

Chiral perturbation theory (ChPT) predicted scaling of the pion,~kaon decay constants $f_π, f_{K} $ and $M_η^2 = m_η^2 + m_{η^{\prime}}^2 $ has been used in the renormalized $2+1$ flavor quark-meson (RQM) model,~to find a consistent path to chiral limit as the $π\ \text{and} \ K $ meson masses approach zero.~The left side of the Columbia plot is generated free from any ambiguity or heuiristic adjustment in the model parameter fixing away from the physical point. The on-shell renormalization of parameters and consistent treatment of the divergent quark one-loop vacuum fluctuations in the RQM model,~make the axial $U_{A}(1)$ anomaly significantly stronger and the light (strange) explicit chiral symmetry breaking strength becomes weaker by a small (relatively large) amount.~The first order chiral transition region in the $m_π-m_{K}$ and $μ-m_{K}$ planes of Columbia plot,~increases due to the above novel features of the RQM model.~Comparing the softening effect of quark one-loop vacuum fluctuation on the chiral transition,~it looks overestimated in a recent functional renormalization group study.

hep-ph↗

arXiv2024

Machine Learning Classification of Alzheimer's Disease Stages Using Cerebrospinal Fluid Biomarkers Alone

Early diagnosis of Alzheimer's disease is a challenge because the existing methodologies do not identify the patients in their preclinical stage, which can last up to a decade prior to the onset of clinical symptoms. Several research studies demonstrate the potential of cerebrospinal fluid biomarkers, amyloid beta 1-42, T-tau, and P-tau, in early diagnosis of Alzheimer's disease stages. In this work, we used machine learning models to classify different stages of Alzheimer's disease based on the cerebrospinal fluid biomarker levels alone. An electronic health record of patients from the National Alzheimer's Coordinating Centre database was analyzed and the patients were subdivided based on mini-mental state scores and clinical dementia ratings. Statistical and correlation analyses were performed to identify significant differences between the Alzheimer's stages. Afterward, machine learning classifiers including K-Nearest Neighbors, Ensemble Boosted Tree, Ensemble Bagged Tree, Support Vector Machine, Logistic Regression, and Naive Bayes classifiers were employed to classify the Alzheimer's disease stages. The results demonstrate that Ensemble Boosted Tree (84.4%) and Logistic Regression (73.4%) provide the highest accuracy for binary classification, while Ensemble Bagged Tree (75.4%) demonstrates better accuracy for multiclassification. The findings from this research are expected to help clinicians in making an informed decision regarding the early diagnosis of Alzheimer's from the cerebrospinal fluid biomarkers alone, monitoring of the disease progression, and implementation of appropriate intervention measures.

cs.LG↗

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)\}.

hep-ph↗

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.

hep-ph↗

arXiv2023

On-shell versus curvature mass parameter fixing schemes in the three flavor quark-meson model with vacuum fluctuations

The vacuum effective potential and phase diagram for the three (2+1) flavor quark-meson model have been computed and compared in an extended mean-field approximation (e-MFA) where the model parameters are fixed by using different renormalization prescriptions after including quark one-loop vacuum fluctuations. When the vacuum one-loop divergence is regularized in the minimal subtraction scheme and the curvature masses of the scalar and pseudo-scalar mesons are used for fixing the parameters, the setting of the quark-meson model with the vacuum term (QMVT) turns out to be inconsistent as one notes that the curvature masses are defined by the evaluation of self-energy at zero momentum. This work constitutes the first application of the consistent on-shell parameter fixing scheme to the three flavor quark-meson (QM) model. In this setting of the renormalized quark-meson (RQM) model, the physical (pole) masses of the $π, K, η$ and $η^{\prime}$ pseudo-scalar mesons and the scalar $σ$ meson,the pion decay constant and kaon 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 nonstrange direction normalized vacuum effective potential plots for both the RQM model and QMVT model, are exactly identical for the $m_σ=$ 658.8 MeV while the nonstrange direction order parameter temperature variations and phase diagrams for both the models RQM and PQMVT are identical when the $m_σ$ value is smaller by 10 MeV i.e. $m_σ=$ 648 MeV. This happens because the normalized vacuum effective potential variation in the nonstrange direction is somewhat influenced by its variation in the strange direction.

hep-ph↗

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.

hep-ph↗

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.

hep-ph↗

arXiv2013

Comparing symmetry restoration trends for meson masses and mixing angles in the QCD-like three quark flavor models

We are computing the modifications for the scalar and pseudoscalar meson masses and mixing angles due to the proper accounting of fermionic vacuum fluctuation in the framework of the generalized 2+1 flavor quark meson model and the Polyakov loop augmented quark meson model(PQM). The renormalized contribution of the divergent fermionic vacuum fluctuation at one loop level makes these models effective QCD-like models. It has been explicitly shown that analytical expressions for the model parameters, meson masses, and mixing angles do not depend on any arbitrary renormalization scale. We have investigated how the incorporation of fermionic vacuum fluctuation in quark meson and PQM models qualitatively and quantitatively affects the convergence in the masses of the chiral partners in pseudoscalar ($π$, $η$, $η'$, $K$) and scalar ($σ$, $a_0$, $f_0$, $κ$) meson nonets as the temperature is varied on the reduced temperature scale. Comparison of present results in the quark meson model with vacuum term and PQM model with vacuum term with the already existing calculations in the bare 2+1 quark meson and PQM models, shows that the restoration of chiral symmetry becomes smoother due to the influence of the fermionic vacuum term. We find that the melting of the strange condensate registers a significant increase in the presence of the fermionic vacuum term and its highest melting is found in the PQM model with vacuum term. The role of the $U_A(1)$ anomaly in determining the isoscalar masses and mixing angles for the pseudoscalar ($η$ and $η'$) and scalar ($σ$ and $f_0$) meson complex has also been significantly modified due to the fermionic vacuum correction. In its influence, the interplay of chiral symmetry restoration and the setting up of the $U_A(1)$ restoration trends have also been shown to be significantly modified.

hep-ph↗

arXiv2012

Exploring criticality in the QCD-like two quark flavour models

The critical end-point (CEP) and critical behaviour in its vicinity, has been explored in the two flavour effective chiral models with and without the presence of effective Polyakov loop potential.The tricritical point (TCP) in the massless chiral limit has been located on the phase diagram in the μandT plane for the Polyakov loop extended Quark Meson Model (PQM) and pure Quark Meson (QM) model which become effective Quantum-chromodynamics (QCD) like models due to the proper accounting of fermionic vacuum loop contribution in the effective potential.The proximity of the TCP to the QCD critical end-point (CEP) has been quantified in the phase diagram. The critical region around CEP has been obtained in the presence as well as the absence of fermionic vacuum loop contribution in the effective potentials of PQM and QM models. The contours of appropriately normalized constant quark number susceptibility and scalar susceptibility have been plotted around CEP in different model scenarios. These contours determine the shape of critical region and facilitate comparisons in different models such that the influence of fermionic vacuum term and Polyakov loop potential on the critical behavior around CEP can be ascertained in qualitative as well as quantitative terms. Critical exponents resulting from the divergence of quark number susceptibility at the CEP,have been calulated and compared with in different model scenarios. The possible influence of TCP on the critical behavior around CEP, has also been discussed. The temperature variation of σand πmeson masses at μ= 0, μ= μ_ CEP and μ> μ_CEP has been shown and compared with in different model scenarios and the emerging mass degeneration trend in the σand πmeson mass variations has been inferred as the chiral symmetry restoration takes place at higher temperatures.

hep-ph↗

arXiv2011

Revisiting the Phase Structure of the Polyakov-quark-meson Model in the presence of Vacuum Fermion Fluctuation

We have considered the contribution of fermionic vacuum loop in the effective potential of Polyakov loop extended Quark Meson Model (PQM) for the two quark flavour case and explored the phase structure and thermodynamics of the resulting PQMVT model (Polyakov Quark Meson Model with Vacuum Term) in detail at non zero as well as zero chemical potential. The temperature variations of order parameters and their derivatives have been calculated and the phase diagram together with the location of critical end point (CEP) has been obtained in $μ$, and $T$ plane in both the models PQMVT and PQM. The PQMVT model analysis has been compared with the calculations in PQM model in order to bring out the effect of fermionic vacuum term on the physical observables. We notice that the critical end point (CEP) which is located near the temperature axis at ($μ=81.0$, $T = 167$ MeV) in the PQM model gets shifted close to the chemical potential axis at ($μ_{CEP}=294.7$, $T_{CEP}=84.0$ MeV) in the PQMVT model calculations of the phase diagram. Since it emerges from a background of second order transition in the chiral limit of massless quarks, the crossover occurring at $μ$ = 0 in PQMVT model for the realistic case of explicitly broken chiral symmetry, has been identified as quite a soft and smooth transition. We have presented and compared the results for temperature variations of thermodynamic observables at zero and different non-zero quark chemical potentials. It is noticed that the presence of fermionic vacuum term in the effective potential leads to a smoother and slower temperature variation of thermodynamic quantities.

hep-ph↗

arXiv2010

$W^+W^-$ production in Large extra dimension model at next-to-leading order in QCD at the LHC

We present next-to-leading order QCD corrections to production of two $W$ bosons in hadronic collisions in the extra dimension ADD model. Various kinematical distributions are obtained to order $α_s$ in QCD by taking into account all the parton level subprocesses. We estimate the impact of the QCD corrections on various observables and find that they are significant. We also show the reduction in factorization scale uncertainty when ${\cal O}(α_s)$ effects are included.

hep-ph↗

arXiv2010

Next-to-leading order QCD corrections to $W^+W^-$ production at the LHC in Randall Sundrum model

We present next-to-leading order QCD corrections to production of two $W$ bosons at the LHC in the Randall-Sundrum model. Various kinematical distributions are obtained to order $α_s$ in QCD by taking into account all the parton level subprocesses. We estimate the impact of the QCD corrections on various observables and find that they are significant. We also show the reduction in factorization scale uncertainty when ${\cal O}(α_s)$ effects are included.

hep-ph↗

arXiv2010

Meson Masses and Mixing Angles in 2+1 Flavor Polyakov Quark Meson Sigma Model and Symmetry Restoration Effects

The meson masses and mixing angles have been calculated for the scalar and pseudoscalar sector in the framework of the generalized 2+1 flavor Polyakov loop augmented quark meson linear sigma model. We have given the results for two different forms of the effective Polyakov loop potential. The comparison of results with the existing calculations in the bare 2+1 quark meson linear sigma model, shows that the restoration of chiral symmetry becomes sharper due to the influence of the Polyakov loop potential. We find that inclusion of the Polyakov loop in quark meson linear sigma model together with the presence of axial anomaly, triggers an early and significant melting of the strange condensate. We have examined how the inclusion of the Polyakov loop qualitatively and quantitatively affects the convergence in the masses of the chiral partners in pseudoscalar ($π$, $η$, $η'$, $K$) and scalar ($σ$, $a_0$, $f_0$,$κ$) meson nonets as the temperature is varied on the reduced temperature scale. The role of $U_A(1)$ anomaly in determining the isoscalar masses and mixing angles for the pseudoscalar ($η$ and $η'$) and scalar ($σ$ and $f_0$)meson complex, has also been investigated in the Polyakov quark meson linear sigma model. The interplay of chiral symmetry restoration effects and the setting up of $U_A(1)$ restoration trend has been discussed and analyzed in the framework of the presented model calculations.

hep-ph↗

arXiv2009

Next-to-leading order QCD corrections to the $Z$ boson pair production at the LHC in Randall Sundrum model

The first results on next-to-leading order QCD corrections to production of two $Z$ bosons in hadronic collisions in the extra dimension model of Randall and Sundrum are presented. Various kinematical distributions are obtained to order $α_s$ in QCD by taking into account all the parton level subprocesses. We estimate the impact of the QCD corrections on various observables and find that they are significant. We also show the reduction in factorization scale uncertainty when ${\cal O}(α_s)$ effects are included.

hep-ph↗

arXiv1998

Matter effects on $η$ and $η'$ mesons

We show how the nuclear medium affects the masses of the $η$ and $η'$ mesons. The change should be easily detectable for dense matter and/or strong $η(η')N\bar N$ coupling. We also find that the $η-η'$ mixing angle is less in magnitude in the nuclear matter than in vacuum.

nucl-th↗