arXiv subjects

Anirban Lahiri

Publications and source records attributed to Anirban Lahiri.

At least 19 recordsLinked to original sources

arXiv2026

Data Science Approaches to Evaluating Honours Candidates

We present a modular data-science pipeline for estimating public sentiment towards individuals from fragmented, unstructured open-source intelligence (OSINT). The method chains web search, text extraction, relevance filtering, tokenisation, co-reference resolution, and sentiment analysis to convert heterogeneous web material into auditable person-level sentiment distributions. We compare AFINN and VADER with MINOS, a domain-informed sentiment algorithm designed to detect language associated with reputational risk, misconduct, and positive public contribution. Applied to public figures with known reputational outcomes, MINOS gives the clearest separation between positive, ambiguous, and negative cases. The results show that chained NLP and OSINT methods can support transparent, reproducible, human-in-the-loop sentiment assessment for high-stakes decision support. We demonstrate the approach on the UK Honours system, where individuals are required to display high standards of public conduct to maintain an Honour.

cs.CL↗

arXiv2022

A machine learning approach to the classification of phase transitions in many flavor QCD

Normalizing flows are generative machine learning models which can efficiently approximate probability distributions, using only given samples of a distribution. This architecture is used to interpolate the chiral condensate obtained from QCD simulations with five degenerate quark flavors in the HISQ action. From this a model for the probability distribution of the chiral condensate as function of lattice volume, quark mass and gauge coupling is obtained. Using the model, first order and crossover regions can be classified and the boundary between these regions can be marked by a critical mass. An extension of this model to studies of phase transitions in QCD with variable number of flavors is expected to be possible.

hep-lat↗

arXiv2022

Towards the chiral phase transition in the Roberge-Weiss plane

We discuss the interplay between chiral and center sector phase transitions that occur in QCD with an imaginary quark chemical potential $μ=i(2n+1) πT/3$. Based on a finite size scaling analysis in (2+1)-flavor QCD using HISQ fermions with a physical strange quark mass and a range of light quark masses, we show that the endpoint of the line of first-order Roberge-Weiss (RW) transitions between center sectors is second order for light quark masses $m_l\ge m_s/320$, and that it belongs to the $3$-d, $Z(2)$ universality class. The operator for the chiral condensate behaves like an energy-like operator in an effective spin model for the RW phase transition. As a consequence, for any non-zero value of the quark mass, the chiral condensate will have an infinite slope at the RW phase transition temperature, $T_{RW}$. Its fluctuation, the disconnected chiral susceptibility, behaves like the specific heat in $Z(2)$ symmetric models and diverges in the infinite volume limit at the RW phase transition temperature $T_{RW}$ for any non-zero value of the light quark masses. Our analysis suggests the critical temperatures for the RW phase transition and the chiral phase transition coincide in the RW plane. On lattices with temporal extent $N_τ=4$, we find in the chiral limit $T_χ=T_{RW}=195(1)~$MeV.

hep-lat↗

arXiv2022

The Chiral Phase Transition in three-flavor QCD from Lattice QCD

We analyze the pseudo-critical behavior of three-flavor QCD using highly improved staggered quarks (HISQ) on lattices with temporal extent $N_τ=8$ and for quark masses corresponding to a pseudoscalar Goldstone mass in the range $80 ~ {\rm MeV} ~ \lesssim ~ m_π~ \lesssim ~ 140 ~ {\rm MeV}$. Our findings are consistent with the occurrence of a second order chiral phase transition at vanishing values of the quark masses. The chiral phase transition temperature at this finite value of the lattice spacing is determined to be $T_c = 98_{-6}^{+3}~{\rm MeV}$. A comparison with a corresponding analysis performed in (2+1)-flavor QCD suggests that the continuum limit extrapolated chiral phase transition temperature in 3-flavor QCD will turn out to be below $90 ~ {\rm MeV}$.

hep-lat↗

arXiv2021

Critical behavior towards the chiral limit at vanishing and non-vanishing chemical potentials

We study the scaling behavior of the (2+1)-flavor QCD crossover region towards the chiral limit with smaller-than-physical light quark mass gauge ensembles, generated using the HISQ fermion discretization. At zero chemical potential, we study the fluctuations of conserved charges and their correlations with the chiral condensate, towards the chiral limit. We analyse the role of universal and regular contributions to the above quantities. We find a preliminary estimate of the leading curvature coefficient of the chiral phase transition line using scaling arguments.

hep-lat↗

arXiv2021

Aspects of finite temperature QCD towards the chiral limit

QCD under extreme conditions has been studied for a long time, and the chiral limit has been a grey area mostly. In this write-up of my talk, I review some of the recent developments made by the community to unveil various features of QCD towards the chiral limit, which includes calculation of the chiral critical temperature and determination of the order of chiral phase transition for various numbers of flavors. Acknowledging the importance of the studies regarding the effective restoration of $U_A(1)$, I try to give a comprehensive overview about the various studies done in the last few years in a comparative manner to realize the current status of the community in this regard. I also discuss very recent efforts about the relevance of various energy-like observables w.r.t. the chiral phase transition.

hep-lat↗

arXiv2021

Lattice QCD at Imaginary Chemical Potential in the Chiral Limit

We report on an ongoing study on the interplay between Roberge-Weiss (RW) and chiral transitions in simulations of (2+1)-flavor QCD with an imaginary chemical potential. We established that the RW endpoint belongs to the 3-$d$, $Z_2$ universality class when calculations are done with the Highly Improved Staggered Quark (HISQ) action in the RW plane with physical quark masses. We also have explored a range of quark masses corresponding to pion mass values, $m_π\geq40$~MeV and found that the transition is consistent with $Z_2$ universality class. We argue that observables that were usually used to determine the chiral phase transition temperature, e.g. the chiral condensate and chiral susceptibility, are sensitive to the RW transition and are energy-like observables for the $Z_2$ transition, contrary to the magnetic-like (order parameter) behavior at vanishing chemical potential. Moreover the calculations performed at $m_π\sim40$~MeV also put a stringent constraint for a critical pion mass at zero chemical potential for a possible first-order chiral phase transition.

hep-lat↗

arXiv2021

Imprint of chiral symmetry restoration on the Polyakov loop and the heavy quark free energy

The Polyakov loop expectation value $\langle P\rangle$ is an order parameter of the deconfinement transition in the heavy quark mass regime, whereas its sensitivity to the deconfinement of light, dynamical quarks is not apparent. From the perspective of an effective Lagrangian in the vicinity of the chiral transition, the Polyakov loop, $P$, is an energy-like observable, and $\langle P\rangle$ should hence scale like the energy density. Using $N_f=2+1$ HISQ configurations at finite lattice spacing, we show that near the chiral transition temperature, the scaling behavior of $\langle P\rangle$ and the heavy quark free energy $F_q$ is consistent with energy-like observables in the 3-$d$, O($N$) universality class. We extend this analysis to other Polyakov loop observables, including the response of the heavy quark free energy, $F_q$, to the baryon chemical potential, which is expected to scale like a specific heat.

hep-lat↗

arXiv2021

Screening masses towards chiral limit

A possible effective restoration of the anomalous $U_A(1)$ symmetry would have a non-trivial effect on the global phase diagram of QCD. In this work we investigate the effective restoration of the $U_A(1)$ through the calculation of scalar and pseudo-scalar screening masses and corresponding susceptibilities, for physical and lower than physical pion masses. Calculations have been performed in (2+1)-flavor HISQ discretization scheme with a physical value of the strange quark mass. Preliminary calculations of the continuum extrapolated scalar and pseudo-scalar masses are presented, based on lattices with three different temporal extent. Non-trivial structure of the difference between scalar and pseudo-scalar susceptibilites are discussed for $N_τ=8$ lattices.

hep-lat↗

arXiv2021

Sensitivity of the Polyakov loop and related observables to chiral symmetry restoration

While the Polyakov loop is an order parameter of the deconfinement transition in the heavy quark mass regime of QCD, its sensitivity to the deconfinement of light, dynamical quarks in QCD is not apparent. On the other hand, the quark mass dependence of the Polyakov loop is sensitive to the appearance of a chiral phase transition. Using lattice QCD calculations in the staggered fermion discretization scheme at finite values of the lattice spacing, $aT = 1/8$, we show here, for the first time, that the Polyakov loop expectation value, and the heavy quark free energy extracted from it, behave like energy-like observables in the vicinity of the chiral phase transition temperature $T_c$. Consistent with scaling behavior of energy-like observables in the 3-$d$, O(2) universality class, the quark mass derivatives diverge in the chiral limit at $T_c$ while the temperature derivatives stay finite. The latter will develop a characteristic spike at $T_c$. This, however, may be resolved only in calculations with quark masses being two orders of magnitude smaller than those currently accessible in lattice QCD calculations.

hep-lat↗

arXiv2020

Conserved charge fluctuations in the chiral limit

We study the signs of criticality in conserved charge fluctuations and related observables of finite temperature QCD at vanishing chemical potential, as we approach the chiral limit of two light quarks. Our calculations have been performed on gauge ensembles generated using Highly Improved Staggered Quark (HISQ) fermion action, with pion masses ranging from 140 MeV to 55 MeV.

hep-lat↗

arXiv2020

Universal scaling properties of QCD close to the chiral limit

We present a lattice QCD based determination of the chiral phase transition temperature in QCD with two massless (up and down) and one strange quark having its physical mass. We propose and calculate two novel estimators for the chiral transition temperature for several values of the light quark masses, corresponding to Goldstone pion masses in the range of $58~{\rm MeV}\lesssim m_π\lesssim 163~{\rm MeV}$. The chiral phase transition temperature is determined by extrapolating to vanishing pion mass using universal scaling relations. After thermodynamic, continuum and chiral extrapolations we find the chiral phase transition temperature $T_c^0=132^{+3}_{-6}$ MeV. We also show some preliminary calculations that use the conventional estimator for the pseudo-critical temperature and compare with the new estimators for $T_c^0$. Furthermore, we show results for the ratio of the chiral order parameter and its susceptibility and argue that this ratio can be used to differentiate between $O(N)$ and $Z_2$ universality classes in a non-parametric manner.

hep-lat↗

arXiv2020

Sensitivity of the Polyakov loop to chiral symmetry restoration

In the heavy, static quark mass regime of QCD, the Polyakov loop is well known to be an order parameter of the deconfinement phase transition; however, the sensitivity of the Polyakov loop to the deconfinement of light, dynamical quarks is less clear. On the other hand, from the perspective of an effective Lagrangian written in the vicinity of the chiral transition, the Polyakov loop is an energy-like operator and should hence scale as any energy-like operator would. We show here that the Polyakov loop and heavy-quark free energy are sensitive to the chiral transition, i.e. their scaling is consistent with energy-like observables in 3-$d$ $O(N)$ universality classes.

hep-lat↗

arXiv2020

Antarjami: Exploring psychometric evaluation through a computer-based game

A number of questionnaire based psychometric testing frameworks are globally for example OCEAN (Five factor) indicator, MBTI (Myers Brigg Type Indicator) etc. However, questionnaire based psychometric tests have some known shortcomings. This work explores whether these shortcomings can be mitigated through computer-based gaming platforms for evaluating psychometric parameters. A computer based psychometric game framework called Antarjami has been developed for evaluating OCEAN (Five factor) indicators. It investigates the feasibility of extracting psychometric parameters through computer-based games, utilizing underlying improvements in the area of modern artificial intelligence. The candidates for the test are subjected to a number scenarios as part of the computer based game and their reactions/responses are used to evaluate their psychometric parameters. As part of the study, the parameters obtained from the game were compared with those evaluated using paper based tests and scores given by a panel of psychologists. The achieved results were very promising.

cs.HC↗

arXiv2020

QCD phase transition in the chiral limit

We present a lattice QCD based determination of the chiral phase transition temperature in QCD with two massless (up and down) and one strange quark having its physical mass. We propose and calculate two novel estimators for the chiral transition temperature for several values of the light quark masses, corresponding to Goldstone pion masses in the range of $58~{\rm MeV}\lesssim m_π\lesssim 163~{\rm MeV}$. The chiral phase transition temperature is determined by extrapolating to vanishing pion mass using universal scaling analysis. After thermodynamic, continuum and chiral extrapolations we find the chiral phase transition temperature $T_c^0=132^{+3}_{-6}$ MeV. We also present some preliminary calculations on interplay of effective $U_A(1)$ restoration and chiral phase transition towards chiral limit.

hep-lat↗

arXiv2020

Polyakov Loop Susceptibility and Correlators in the Chiral Limit

In quenched QCD the Polyakov loop is an order parameter of the deconfinement transition, but with decreasing quark mass, the peak in the Polyakov loop susceptibility becomes less pronounced, and it loses its interpretation as an indicator for deconfinement. For this $N_f=2+1$ HISQ study, we fix the strange quark mass $m_s$ at its physical value and investigate the dependence of the Polyakov loop on the light quark mass $m_l$ in the range $m_s/m_l=27-160$, following $m_l$ toward the chiral limit. In particular we will look how the inflection point and susceptibility behave as we decrease $m_l$, to see whether one finds any indication of a crossover, and therefore whether the Polyakov loop is sensitive to the chiral phase transition. Preliminary results show no signal of a crossover from the real part of the Polyakov loop in the vicinity of the chiral crossover. Closely related is an investigation of Polyakov loop correlations and the Debye mass in this limit. Preliminary results suggest little or no dependence on $m_l$.

hep-lat↗

arXiv2019

Ground state mass in short lattices by controlling overconfidence and bias in Bayesian fits

We investigate the seemingly ill-defined problem of extracting a ground-state mass from a lattice simulation where the extent of the lattice is not long enough to project out the ground-state properly. We regulate the problem using a Bayesian method. We show that controlling meta-parameters (overconfidence) can allow the data to overcome the input priors (bias). We can write the method as a black-box technique which allows extraction of a ground-state mass, even on a relatively short lattice.

hep-lat↗

arXiv2019

Conserved charge fluctuations with smaller-than-physical quark masses

We present results from calculations of conserved charge fluctuations in $(2+1)$-flavor QCD using light quark masses in the range $m_s/80 \leq m_l \leq m_s/27$, with the strange quark mass ($m_s$) kept fixed at its physical value. This corresponds to a Goldstone pion mass in the range $80$ MeV $\leq m_π\leq 140$ MeV. The measurements have been done using HISQ fermion discretization and Symanzik improved gauge action. We discuss the quark mass dependence of up to 6th order cumulants and present first results on the separation of singular and regular contributions to these cumulants. From these results, we examine the nature of the chiral phase transition and the variation of the curvature of the crossover line as we approach the chiral limit.

hep-lat↗