Sagnik Chatterjee, IISER Bhopal
The matter at Neutron star (NS) cores are at highly compressed state and
due to gravity, the density can be built up to a few times the nuclear
saturation density. They are very compact and have been observationally
identified with pulsars with their mass being in the range from 0.7 - 3 solar
masses and a radius between 10-15 km. They are therefore one of...
We present the first non-perturbative calculation on the lattice of the baryonic screening masses in a wide range of temperature from $1$ GeV up to $T\sim 160$ GeV. The calculation has been carried out by Monte Carlo simulations and exploits a new strategy to simulate extremely high temperatures which was recently used to compute the non-singlet mesonic screening spectrum for the first time in...
It is important to unravel the internal structure of neutron stars in astrophysics. One effective way to study the interior of neutron stars is analyzing their seismic oscillations. Recently, the chiral magnetic wave (CMW), which is a density wave propagating along magnetic fields due to the chirality of fermions, has been studied in the context of the heavy ion collision experiments.
In...
Knowing the QCD phase diagram is one of the biggest physics challenges we have nowadays.
Neutron stars are true laboratories that test extreme conditions, essential to determine the QCD phase diagram.
In their core, the density can reach $n_B \approx 3 − 8 n_s$ (where $n_s = 0.16 fm^{-3}$ is the saturation density), a range of densities where QCD is unknown.
Ab-initio calculations determine...
Evidence suggest that in the chiral limit, the QCD phase transition becomes a second order phase-transition in the $O(4)$ universality class. Since real world QCD is not too far from the chiral limit, it is thus interesting to explore the consequences for static and dynamic correlation functions. Since, in the vicinity of the critical point, the physics is governed by universal scaling...
In the chiral limit the complicated many-body dynamics around the second-order chiral phase transition of two-flavour QCD can be understood by appealing to universality. We present a novel formulation of real-time functional renormalization group that describes the stochastic hydrodynamic equations of motion for systems in the same dynamic universality class, which correspond to Model G in the...
In this talk, I will report our recent achievements based on refs. [1,2]. Below are highlights from our results.
Confinement under Imaginary Rotation
STAR Collaboration found nuclear matter rotating at $\omega \sim 10^{22}\ s^{-1}$ in heavy ion collisions. Neutron stars can also spin at $\omega \sim 10^3\ s^{-1}$. It is interesting but difficult to unravel mysteries in understanding...
Quantum Electrodynamical effects are prevalent in the complex, nonlinear dynamics of plasmas in extreme astrophysical environments (neutron stars, pulsars, black-hole accretion disks) and intense laser interaction with matter. Understanding of these systems has advanced in parallel with the development of the particle-in-cell numerical framework, where the electromagnetic fields created by...
Light nuclei can be found in core-collapse supernova matter and in binary star mergers. Their presence may impact the evolution of these systems. The presence of degrees of freedom such as hyperons, hyperclusters and Delta isobars may as well impact the composition of these systems at temperatures as high as T~50-100 MeV achieved in both supernova and binary systems.
Implicit Regularization (IReg) is a regularization scheme that works in the physical dimension of the theory and allows for the separation of the ultraviolet (UV) and infrared (IR) divergences of an amplitude. We compute the Higgs decay into gluons using an effective Higgs–Yang-Mills interaction in the limit of infinite top quark mass by using a dimension five operator. The decay rate for...
We employ implicit regularization (IReg) in quark-antiquark decays of the Z, or of a scalar (CP-even or odd) boson at NLO, and compare with dimensional schemes to reveal subtleties involving infrared divergence cancellation and $\gamma_5$-matrix issues. Besides the absence of evanescent fields in IReg, such as $\epsilon$-scalars required in certain schemes that operate partially in the...
In this talk, I discuss results about inhomogeneous chiral phases, where in addition to chiral symmetry also translational symmetry is broken, and the related moat regimes, where non-monotonic dispersion relations appear driven by a negative wave function renormalization. These phenomena may occur in strongly-interacting matter under extreme conditions such as finite baryon density and...
Quantum Chromodynamics at high densities is likely to exhibit inhomogeneous phases. The chiral density wave is a simple ansatz for a class of such phases, and it has been extensively studied in models based on quark degrees of freedom. We are exploring the possibility of a chiral density wave in a nucleon-meson model, taking into account the contribution of the Dirac sea. We find that for...
For the exploration of the phase diagram of QCD, effective Polyakov loop theories derived from lattice QCD provide a valuable tool in the heavy quark mass regime. In practice, the evaluation of these theories is complicated by the appearance of long-range and multipoint interaction terms. On the other hand, it is well known that for theories with such kind of interactions mean field...
Initial state effects in Heavy Ion Collisions play an important role in the quark-gluon plasma formation. Moreover, recent experimental studies have shown that these initial state effects become more relevant in small collision systems where the characterization of medium formed is still an open question. We present predictions of the initial state effects on the small collision systems for...
Recently, efforts have been increased to incorporate various symmetries into the architectures of neural networks. Lattice gauge equivariant Convolutional Neural Networks (L-CNNs) [1] are designed to respect local gauge symmetry, an essential component in lattice gauge theories. This makes them a promising approximator of gauge covariant functions on a lattice. In addition to local symmetries,...
A strategy that has been increasingly and successfully employed over the last few years in the design of neural network architectures is the implementation of layers that inherently respect a specific symmetry. In the context of lattice gauge theories, local symmetries are a crucial element. Lattice gauge equivariant neural networks (L-CNNs) [1] are designed to preserve such symmetries and...
The energy-momentum and spin tensors for a given theory can be replaced by alternative expressions that obey the same conservation laws for the energy, linear momentum, as well as angular momentum but, however, differ by the local redistribution of such quantities (with global energy, linear momentum, and angular momentum remaining unchanged). This arbitrariness is described in recent...
In this work we probe the QCD Anderson transition by studying spectral distributions of the massless overlap operator on gauge configurations created by the twisted mass at finite temperature collaboration (tmfT) with 2+1+1 flavors of dynamical quarks and the Iwasaki gauge action. We assess finite-size and discretization effects by considering two different lattice spacings and several...
We compute the critical exponents of the O(N) model within the Functional Renormalization Group (FRG) approach. We use recent advances which are based on the observation that the FRG flow equation can be put into the form of an advection-diffusion equation. This allows to employ well-tested hydrodynamical algorithms for its solution. In this study we work in the local potential approximation...
The phase diagram of dense matter relevant for neutron stars is typically studied with effective models. These models are nonrenormalizable and must be regularized in order to obtain finite results, leading to regularization artefacts near the cutoff. We study neutral dense matter in a three-flavour Nambu-Jona-Lasinio type model that includes a diquark interaction leading to the formation of...
We have studied the chiral and confinement-screening phase transitions in the Schwinger model at finite temperature and density using the quantum algorithm.
The theoretical exploration of the phase diagram for strongly interacting systems at finite temperature and density remains incomplete mainly due to the sign problem in the conventional Lattice Monte Carlo method.
However, quantum...
Recently, we have calculated the dilepton rate coming out of a hot and dense QCD medium under an arbitrary strength of magnetic field [1]. A considerable amount of enhancement in the rate has been observed in the presence of the magnetic field. We calculate the p_T spectra and the anisotropic flow of dileptons using a hydrodynamical model framework and the new rate [2]. Both spectra and...
Towards the equation of state of neutron stars, we present results for the zero-temperature thermodynamics of strong-interaction matter at high densities which have been obtained based on first-principles functional Renormalization Group studies. In particular, we discuss gluon vacuum polarization effects on the equation of state and the speed of sound in a (semi-)perturbative manner....
Heavy-ion collisions create an environment characterized by extremely high energy density and temperature, leading to the formation of a deconfined state of matter known as quark-gluon plasma (QGP), where quarks and gluons move freely. Recently, collective effects have also been observed in proton-proton (pp) collisions, specifically in events with a high particle production rate. To gain...
In femtoscopy, the correlations between low relative momentum particles can be linked to their emission source function and final state interaction. In a recent precision measurement of the p$\Lambda$ correlation function at the LHC, a deviation was found from the state-of-the-art chiral effective field theory model. If this discrepancy is related to the p$\Lambda$ interaction, it would have...
Determining the phase structure of nuclear and quark matter in external magnetic fields is not only of theoretical interest but also experimentally motivated by the large magnetic fields found in heavy-ion collisions and compact star physics. By including the effects of the chiral anomaly within Chiral Perturbation theory at zero-temperature and non-zero baryon chemical potential, it can be...
We investigate the formation of a color superconductor in dense strong-
interaction matter as associated with the dynamical generation of a gap in
the quark excitation spectrum. To this end, we employ the Wetterich equa-
tion and solve it with numerical methods borrowed from fluid dynamics,
without making any further assumptions about the form of the effective
potential. We critically...
Experimental data on a wide range of jet observables measured in heavy ion collisions provide a rich picture of the modification of jets as perturbative probes and of the properties of the quark-gluon plasma that is formed in these collisions. However, their interpretation is often limited by the assumptions of specific quenching models, and it remains a challenge to establish...
While in field theoretical calculations, being performed in the thermodynamic limit, the volume is infinite, the heavy-ion collisions always carry the effects of finite system size. It is expected that a sufficiently small volume can affect the thermodynamics and the phase diagram of the strongly interacting matter. These effects can be studied in effective models by taking into account the...
In high-energy heavy ion collisions, two relativistically moving nuclei collide with each other to form a hot dense matter known as quark-gluon plasma (QGP). Along with the QGP that is produced in the initial stage of heavy ion collisions, an intense and strong electromagnetic field is also thought to be produced, the main source of which are the spectators. Spectators are those which do not...
Abstract: At the ultrahigh densities existing in the core of neutron stars (NSs), it is expected that a phase transition from baryonic to deconfined quark matter may occur. Such a phase transition would affect the underlying equation of state (EoS) as well as the observable astrophysical properties of NSs. Comparison of EoS model predictions with astronomical data from multimessenger signals...
Femtoscopy is an important technique for studying space--time properties of emission source created in heavy-ion collisions such as spatial size, evolution time, collective flow effects, etc. In this contribution, we present the results of a femtoscopic analysis of identical charged-kaon pair correlations in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02~TeV. The results of the one- and...
Over the last decades, the theoretical picture of how hadronic jets interact with nuclear matter has been extended to account for the medium’s finite longitudinal length and expansion. However, only recently a first-principle approach has been developed that allows to couple the jet evolution to the medium flow and anisotropic structure in the dilute limit. In this talk, we will show how to...
The existence and location of the QCD critical point are objects of both experimental and theoretical studies. The comprehensive data collected by NA61/SHINE at the CERN SPS during a two-dimensional scan in beam momentum (13$\textit{A}$-150$\textit{A}$ GeV/$\textit{c}$) and system size ($\textit{p}$+$\textit{p}$, $\textit{p}$+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb) allows for a systematic search for...
We employ the Schwinger-Keldysh (SK) formalism to study the spin polarization in a medium induced by the metric perturbation diagrammatically. The results in the near-equilibrium limit can be used to describe the effects of hydrodynamic gradient on the polarization (e.g. shear-induced polarization). Moreover, the results obtained from SK formalism may apply to far-from-equilibrium situations...
The nature of the QCD phase transition in the chiral limit constitutes a challenging problem for lattice QCD as it is not directly simulable. Its study, however, provides constraints on the phase diagram at the physical point. Recently, the lattice chiral limit was approached by mapping out the chiral critical surface separating the first-order region from the crossover region in an enlarged...
We present a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermal equilibration and quark production in a system of quarks and gluons. With BEDA, we analyse the evolution of spatially homogeneous system initially populated bu gluons. We observe that soft partons, dominantly produced via medium-induced radiation, rapidly fill a thermal distribution with an...