arXiv subjects

Krzysztof Redlich

Publications and source records attributed to Krzysztof Redlich.

At least 37 records · Page 2Linked to original sources

arXiv2023

Interplay of baryonic chiral partners in fluctuations of net-baryon number density

In this contribution, we use the parity doublet model to investigate the fluctuations of the net-baryon number density. We discuss the systematics of the susceptibilities and their ratios for nucleons of positive and negative parity, as well as their correlator. We demonstrate that the fluctuations of positive-parity nucleon do not reflect the fluctuations of the total net-baryon number at the chiral phase transition.

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arXiv2023

Curvature of the energy per particle in neutron stars

Neutron stars (NSs) serve as laboratories for probing strongly interacting matter at the most extreme densities. Their inner cores are expected to be dense enough to host deconfined quark matter. Utilizing state-of-the-art theoretical and multi-messenger constraints, we statistically determine the bulk properties of dense NS matter. We show that the speed of sound can be expressed in terms of the slope and curvature of the energy per particle. We demonstrate that the restoration of conformal symmetry requires changing the sign of the curvature of the bulk energy per particle as a function of energy density. Furthermore, we find that such a sign change is closely related to the peak in the speed of sound. We argue that the curvature of the energy per particle may serve as an approximate order parameter that signifies the onset of strongly coupled conformal matter in the NS core.

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arXiv2023

Influence of dynamical screening of four-quarks interaction on the chiral phase diagram

We investigate the effect of screening of the four-quarks contact interactions by the ring diagram at finite temperature and density in an effective chiral model inspired by QCD in the Coulomb gauge. As a consequence, a medium-dependent coupling naturally emerges which, in a class of chiral models, brings the chiral crossover temperature down to the value calculated in LQCD at low net-baryon density. Furthermore, it implies a stronger divergence of the chiral susceptibility at the critical point compared to the mean-field dynamics. At vanishing temperature, however, the transition sets in at unphysically small chemical potential, indicating a need for additional effects to compensate for the screening strength. We discuss the properties of an effective potential for a class of models described by momentum-independent gap equations. In particular, we introduce the method to construct an approximate effective potential from the gap equations to determine the location of the first-order phase transition.

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arXiv2023

Finite volume effects in the extended linear sigma model via low momentum cutoff

Contrary to field theoretical calculations in the thermodynamic limit where the volume is assumed to be infinitely large, the heavy-ion collisions always carry the effects of finite size. A sufficiently small system size is expected to affect the thermodynamic quantities and the phase diagram of the strongly interacting matter. To study these effects one can take into account the finite spatial extent of the system within the framework of an effective model too, via the restriction of the momentum integrals using discretization or in a simplified case using a low momentum cutoff. We investigated the effects of the finite volume in a vector meson extended Polyakov quark-meson model and found a remarkable change in the thermodynamics and the phase transition, especially in the location of the critical endpoint.

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arXiv2023

Light nuclei production in pp and pA collisions in the Baryon Canonical Ensemble

The increase in yields of light nuclei with charged particle multiplicity, as reported by the ALICE collaboration at CERN in p-p and p-Pb collisions at the LHC energy is investigated in the thermal hadron resonance gas model. The model is extended to account for exact baryon number conservation. The focus is on the production of protons, deuterons, $^3$He, and $^3_Λ$H. A very good description of proton and deuteron yields is obtained as a function of charged particle multiplicity in the mid-rapidity region using the same fixed temperature as in central Pb-Pb collisions. The yields of light nuclei $^3$He and $^3_Λ$H though qualitatively explained as a function of multiplicity, are lower than the model expectation. One of the possible reasons could be that for $^{3}$He and $^{3}_Λ$H, the chemical equilibrium is not yet reached at small multiplicities.

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arXiv2023

Fluctuations near the liquid-gas and chiral phase transitions in hadronic matter

We investigate the fluctuations of the net-baryon number density in dense hadronic matter. Chiral dynamics is modeled via the parity doublet Lagrangian, and the mean-field approximation is employed to account for chiral criticality. We focus on the qualitative properties and systematics of the second-order susceptibility of the net-baryon number density for individual positive- and negative-parity nucleons whose masses become degenerate at the chiral restoration. It is shown that the second-order susceptibility of the positive-parity state can become negative when the chiral symmetry is restored, as a natural consequence of the unique relationship of the mass to the order parameter. Moreover, we find that such negative fluctuations are indicative of approaching the critical point on the chiral phase boundary. Our results may have consequences for the interpretation of the experimental data on net-proton fluctuations in heavy-ion collisions.

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arXiv2023

Reaching percolation and conformal limits in neutron stars

Generating an ensemble of equations of state that fulfill multimessenger constraints, we statistically determine the properties of dense matter found inside neutron stars (NSs). We calculate the speed of sound and trace anomaly and demonstrate that they are driven towards their conformal values at the center of maximally massive NSs. The local peak of the speed of sound is shown to be located at values of the energy and particle densities which are consistent with deconfinement and percolation conditions in QCD matter. We also analyze fluctuations of the net-baryon number density in the context of possible remnants of critical behavior. We find that the global maxima of the variance of these fluctuations emerge at densities beyond those found in the interiors of NSs.

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arXiv2022

Conformality and percolation threshold in neutron stars

Speed of sound is given attention in multi-messenger astronomy as it encodes information of the dense matter equation of state. Recently the trace anomaly was proposed as a more informative quantity. In this work, we statistically determine the speed of sound and trace anomaly and show that they are driven to their conformal values at the centers of maximally massive neutron stars. We show that the local peak in the speed of sound can be associated with deconfinement along with percolation conditions in QCD matter.

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arXiv2022

Driving chiral phase transition with ring diagram

We study the dressing of four-quark interaction by the ring diagram, and its feeding back to the quark gap equation, in an effective chiral quark model. Implementing such an in-medium coupling naturally reduces the chiral transition temperature in a class of chiral models, and is capable of generating the inverse magnetic catalysis at finite temperatures. We also demonstrate the important role of confining forces, via the Polyakov loop, in a positive feedback mechanism which reinforces the inverse magnetic catalysis.

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arXiv2022

Reconciling Multi-messenger Constraints with Chiral Symmetry Restoration

We consider the parity doublet model for nucleonic and delta matter to investigate the structure of neutron stars. We show that it is possible to reconcile the multi-messenger astronomy constraints within a purely hadronic equation of state (EOS), which accounts for the self-consistent treatment of the chiral symmetry restoration in the baryonic sector. We demonstrate that the characteristics of the EOS required by the astrophysical constraints do not necessarily imply the existence of a hadron-quark phase transition in the stellar core.

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arXiv2022

Exact strangeness conservation in heavy ion collisions

We investigate the increase in strangeness production with charged particle multiplicity ($dN_{ch}/dy$) seen by the ALICE collaboration at CERN in p-p, p-Pb and Pb-Pb collisions using the hadron resonance gas model. The strangeness canonical ensemble is used taking into account the interactions among hadrons using S-matrix corrections based on known phase shift analyses. We show the essential role of constraints due to the exact conservation of strangeness which is instrumental to describing observed features of strange particle yields and their scaling with $dN_{ch}/dy$. Furthermore, the results on comparing the hadron resonance gas model with and without S-matrix corrections, are presented. We observe that the interactions introduced by the phase shift analysis via the S-matrix formalism are essential for a better description of the yields data independent of collision system. This work is based on our long-lasting collaboration and most recent publications with Jean Cleymans.

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arXiv2022

Fluctuations in the canonical ensemble of an Abelian charge

We study fluctuations in the canonical ensemble, where the net baryon number is exactly conserved. The focus is on cumulants and factorial cumulants linked to the baryon and antibaryon multiplicities and their sum or difference in full phase-space as well as in subsystems. In particular, we connect the fluctuations of the net baryon number in a subsystem, relevant for fluctuation studies in nucleus-nucleus collisions, with fluctuations of the baryon and antibaryon numbers of the total system. We derive analytic expressions for factorial cumulants of arbitrary order. Compact results are obtained in terms of cumulants of the baryon number of the total system. Moreover, we derive the asymptotic forms of the factorial cumulants of baryon and antibaryon multiplicities in the high- and low-temperature limits and discuss the results in the context of heavy-ion collision experiments.

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arXiv2022

Chiral symmetry restoration and the $Δ$ matter formation in neutron stars

We analyze the effects of chiral symmetry restoration in hadronic matter, including the lowest-lying baryonic resonance $Δ$ based on the parity doublet model. We study the role of $Δ$ and its chiral partner on the equation of state (EoS) of dense matter under neutron star (NS) conditions of $β$-equilibrium and charge neutrality. We find that the softening of the EoS driven by the early onset of $Δ$ matter due to partial restoration of chiral symmetry allows accommodating the modern multi-messenger astrophysical constraints on the mass, radius, and tidal deformability. The softening above the saturation density is accompanied by subsequent stiffening at high densities. We also find that the matter composition in the NS cores may be different upon variations of the repulsive interactions of $Δ$ baryons in hadronic matter.

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arXiv2022

Reconciling multi-messenger constraints with chiral symmetry restoration

We analyze the recent astrophysical constraints in the context of a hadronic equation of state (EoS), in which the baryonic matter is subject to chiral symmetry restoration. We show that with such EoS it is possible to reconcile the modern constraints on the neutron star (NS) mass, radius, and tidal deformability (TD). We find that the softening of the EoS, required by the TD constraint of a canonical $1.4~M_\odot$ NS, followed by a subsequent stiffening, required by the $2~M_\odot$ constraint, is driven by the appearance of $Δ$ matter due to partial restoration of chiral symmetry. Consequently, a purely hadronic EoS that accounts for the fundamental properties of quantum chromodynamics linked to the dynamical emergence of parity doubling with degenerate masses of nucleons and $Δ$ resonances can be fully consistent with multi-messenger data. Therefore, with the present constraints on the EoS, the conclusion about the existence of the quark matter in the stellar core may still be premature.

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arXiv2021

Chiral criticality and the role of repulsive interactions in hot hadronic matter

We explore fluctuations of the net-baryon number density in hadronic matter at vanishing chemical potential. We discuss the interplay between chiral dynamics and repulsive interactions and their influence on the properties of these fluctuations near the chiral crossover in the parity doublet model. We find that the characteristic properties of cumulants are entirely linked to the critical chiral dynamics and cannot be reproduced in phenomenological models, which account only for repulsive interactions. Consequently, a description of the higher-order cumulants of the net-baryon density requires a self-consistent treatment of the chiral in-medium effects and repulsive interactions.

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arXiv2021

Polarization effects at finite temperature and magnetic field

We study the screening of four-quark interaction by the ring diagram in an effective chiral quark model. This entails a medium dependent coupling which naturally reduces the chiral transition temperature in a class of models, and is capable of generating an inverse magnetic catalysis at finite temperature. These results are the first coherent description of inverse magnetic catalysis, anchored to a reliable field-theoretical basis.

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arXiv2021

The multiple-charm hierarchy in the statistical hadronization model

In relativistic nuclear collisions the production of hadrons with light (u,d,s) quarks is quantitatively described in the framework of the Statistical Hadronization Model (SHM). Charm quarks are dominantly produced in initial hard collisions but interact strongly in the hot fireball and thermalize. Therefore charmed hadrons can be incorporated into the SHM by treating charm quarks as 'impurities' with thermal distributions, while the total charm content of the fireball is fixed by the measured open charm cross section. We call this model SHMc and demonstrate that with SHMc the measured multiplicities of single charm hadrons in lead-lead collisions at LHC energies can be well described with the same thermal parameters as for (u,d,s) hadrons. Furthermore, transverse momentum distributions are computed in a blast-wave model, which includes the resonance decay kinematics. SHMc is extended to lighter collision systems down to oxygen-oxygen and includes doubly- and triply-charmed hadrons. We show predictions for production probabilities of such states exhibiting a characteristic and quite spectacular enhancement hierarchy.

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arXiv2021

Fluctuations of order parameter in an $SU(N_c)$ effective model

We investigate features of the deconfinement phase transition in an $SU(N_c)$ gauge theory as revealed by fluctuations of the order parameter. The tool of choice is an effective model built from one-loop expressions of the field determinants of gluon and ghost, in the presence of a Polyakov loop background field. We show that the curvature masses associated with the Cartan angles, which serve as a proxy to study the $A_0$-gluon screening mass, show a characteristic dip in the vicinity of the transition temperature. The strength of the observables, which reflects a competition between the confining and the deconfining forces, is sensitive to assumptions of dynamics, thus provides an interesting link between the $Z(N_c)$ vacuum structure and the properties of gluon and ghost propagators.

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