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The Modern Physics of Compact Stars and Relativistic Gravity 2025
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Etc/GMT+4
Yerevan, Armenia
Yerevan, Armenia
Department of Physics, Alex Manukyan str. 1, Yerevan, Armenia
Aram Saharian
(Yerevan State University ),
Armen Sedrakian
(Goethe University, Frankfurt am Main)
Description
This conference is the 8th in a series that aim to bring together people working in the astrophysics of compact stars, physics of dense matter, gravitation and cosmology, observations of pulsars and binary neutron stars, and related fields.
The previous conferences were held in 2008, 2013, 2015, 2017, 2019, 2021, and 2023
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Welcome
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1
The Golden Age of Neutron Stars
Neutron stars were first posited in the early thirties, and discovered as pulsars in the late sixties; however we are only recently beginning to understand the matter they contain. I will describe the ongoing development of a consistent picture of the liquid interiors of neutron stars, now driven by ever increasing observations as well as theoretical advances. These include in particular observations of at least three heavy neutron stars of about 2.0 solar masses and higher; ongoing simultaneous inferences of masses and radii of neutron stars by the NICER telescope; and past and future observations of binary neutron star mergers, through gravitational waves as well as across the electromagnetic spectrum. Theoretically an understanding is emerging in QCD of how nuclear matter can turn into deconfined quark matter in the interior, and be capable of supporting heavy neutron stars, which I will illustrate with a discussion of modern quark-hadron crossover equations of state.
Speaker: Prof. Gordon Baym (University of Illinois Urbana-Champaign) -
2
Estimating Equation of State Uncertainties from Mass and Radius Observations
Traditionally, neutron star observations from which mass and radius estimates are obtained are used to inform the dense matter equation of state through Bayesian inference. This procedure introduces a difficult-to-infer uncertainty stemming from prior choices for equation of state models and their parameters. We are developing a method to directly estimate central values of energy density and pressure from mass and radius estimates that is universal, that is, it is largely equation of state independent. In this way the usual prior uncertainties in the equation of state models and parameters are not only avoided, but can be deduced. These prior uncertainties appear to be at least as large as the uncertainties due to observations.
Speaker: Prof. James Lattimer (University of New York at Stony Brook) -
11:45
Coffee Break
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3
Uniform models of neutron and quark stars in General Relativity
Models of neutron and quark stars are considered in the case of a uniform density distribution. A universal
algebraic equation, valid for any equation of state, is obtained in General Relativity. This equation allows one to find
the approximate mass of a star for a given density without resorting to the integration of differential equations. The solutions neutron star models for various equations of state, are calculated. The maximum values of stable NS masses differ from the values in exact solutions obtained by the numerical integration of differential equations by at most 20%.Speaker: Gennady Bisnovatyi-Kogan (Space research institute RAN) -
13:00
Lunch break
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4
Relativistic corrections and three-nucleon forces in neutron star matter
We discuss the inclusion of relativistic boost corrections in the correlated basis function (CBF) effective nuclear Hamiltonian. In this framework, a well-behaved nuclear effective interaction is derived from a realistic Hamiltonian through the CBF formalism and cluster expansion techniques. This approach has proven to be remarkably powerful in computing both equilibrium and transport properties of nuclear matter, allowing for several applications in the context of neutron star physics.
Our study analyzes the dependence of boost corrections on the non-relativistic nucleon-nucleon potential, as well as their strong interplay with three-nucleon forces. Because of the crucial role of three-nucleon forces in driving the stiffness of the equation of state at high density, a correct understanding of such interplay is essential for an accurate description of neutron star physics.
Speaker: Andrea Sabatucci -
5
Hybrid Nuclear Matter EOS with Color Superconducting Quark Phase: Bayesian Constraints from Observations
We perform a Bayesian analysis of the equation of state (EOS) constraints using recent observational data, including pulsar masses, radii, and tidal deformabilities. Our focus is on a class of hybrid neutron star EOS that incorporates color superconducting quark matter, based on a recently developed nonlocal chiral quark model. The nuclear matter phase is described using a relativistic density functional approach within the DD2 class, while the phase transition between nuclear and quark matter is described using a Maxwell construction.
Our analysis identifies a region within the two-dimensional parameter space, defined by the vector meson coupling and scalar diquark coupling, where the observational constraints are met with the highest probability (90% of the maximum). We present the overlap of this region with those where other properties are fulfilled:
1. A strong phase transition that produces a third family of compact stars.
2. A maximum mass of the hybrid neutron star that exceeds that of the purely nucleonic star.
3. An onset mass for quark deconfinement below one solar mass.Speaker: Dr Alexander Ayriyan (University of Wroclaw & AANL) -
6
Finite-temperature equations of state of compact stars with hyperons
The equation of state (EoS) for dense, strongly interacting matter serves as the central input in an array of astrophysical simulations involving isolated compact objects and binary systems across various scenarios. While numerous models exist to describe the composition of cold neutron stars, the range narrows considerably when considering the so-called general-purpose EoS, which encompass varying temperature, density, and electron fraction. Moreover, several EoS models that include non-nucleonic degrees of freedom in dense matter, like hyperons, have been rendered incompatible with the recently imposed astrophysical constraints extracted from observations. In this talk, I will discuss the generation of finite temperature EoS of hypernuclear matter in the range of densities, temperatures, and electron fractions that are needed for numerical simulations of supernovas, protoneutron stars, and binary neutron star mergers, along with the variation of their generic features and composition depending on the parametrization of the baryon-meson couplings. Finally, I will present the results for the properties of neutron stars constructed with the zero-temperature version of those EoS and their comparison with the existing astrophysical observations.
Speaker: STEFANOS TSIOPELAS (University of Wrocław) -
16:30
Coffee break
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7
Properties of the Object HESS J1731-347 as a Twin Compact Star
By consideration of the Compact object HESS J1731-347 as a hybrid twin
compact star, i.e., a more compact star than its hadronic twin of the
same mass, its stellar properties are derived. Besides showing that the
properties of compact stars in this work are in good agreement with
state-of-the-art constraints both from measurements carried out in
laboratory experiments as well as by multi-messenger astronomy
observations, the realization of an early strong hadron-quark first
order phase transition as implied by the twins is discussed.Speaker: Dr David Alvarez-Castillo -
8
Quark Deconfinement Phase Transition in Hot Neutron-Star Matter: Effects of Neutrino Trapping.
The possibility of quark deconfinement in hadronic matter at high densities and/or sufficiently high temperatures, as well as its impact on the properties of compact stars and the dynamics of heavy-ion collisions, is one of the most debated topics in modern physics.
In this paper, we investigate the temperature dependence of the parameters associated with the first-order quark deconfinement phase transition in hot, beta-equilibrium, electrically neutral hadronic matter. Considering the opacity of hot hadronic matter to neutrinos, the impact of neutrino trapping on the characteristics of the phase transition is examined.
For the thermodynamic description of hot matter with hadronic structure, we used a relativistic mean-field (RMF) theory with exchange meson fields including sigma, omega, delta, and rho mesons. Quark matter was described within the framework of the local SU(3) Nambu-Jona-Lasinio (NJL) model.
Phase diagrams of temperature are obtained depending on both the baryon chemical potential and the baryon number density. The influence of neutrino trapping on the phase diagram picture and, in particular, on the critical endpoint parameters is analyzed.Speaker: Grigor Alaverdyan
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9
The correspondence of generalised entropic cosmology with F(T) and F(Q) modified gravity and gravitational waves
We investigate the correspondence between modified gravity theories and general entropic cosmology theory. Such a theory is proposed by an analogy with Jacobson’s work, where the Einstein equation was derived from the Bekenstein-Hawking entropy. We compare FLRW equations obtained in entropic gravity with those in modified gravity theories. It is found the correspondence of F(T) and F(Q) gravities and general entropic gravity. We regard the F(T) and F(Q) gravity theories as effective local theories corresponding to the entropic gravity theories and we investigate the gravitational waves. The obtained equation of the gravitational wave is identical to that in Einstein’s gravity except that the gravitational coupling is modified by the functional form of the functions F(T) and F(Q).
Speaker: Prof. Sergei Odintsov (ICREA and ICE-CSIC, Barcelona) -
10
The Role of Supermassive Black Holes in Galaxy Evolution
I will present an overview of the history of observing supermassive black holes (SMBHs) in contemporary astronomy, including discussing various methods to detect these objects, and constrain their masses and accretion rates. I will go on to review important evidence for SMBHs impacting their host galaxies via a mix of : (i) “quasar-mode”, ejective feedback; and via (ii) “radio-mode”, relativistic jet-triggered feedback. I will show how contemporary cosmological simulations require feedback from SMBHs to “quench” galaxies (i.e., causing them to stop forming stars). Indeed, without strong feedback from SMBHs, contemporary galaxy formation models fail to get even the most basic properties of the galaxy population correct - such as the multi-epoch stellar mass function, and the star formation rate density evolution with cosmic time. I will go on to present observational evidence for these processes operating in nature over 13 Gyr of cosmic history, much as predicted from these cosmological models. I will end this review talk by discussing the new evidence (largely from JWST) for over-massive SMBHs in the very early Universe, which may require either primordial black holes to form during the Big Bang, or else for direct collapse prior to galaxy formation. This turns the conventional narrative of galaxy formation on its head – instead of SMBHs forming as the end point of stellar evolution (via mergers of the remnants of the first populations of stars), they may well be the fundamental trigger for galaxy formation to initiate in the first place. I will conclude by remarking on the astonishing impact of SMBHs on scales of up to ten orders of magnitude greater than their gravitational sphere of influence.
Speaker: Prof. Asa F. L. Bluck (Florida International University) -
10:30
Coffee break
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11
Revisiting the Rhoades-Ruffini Bound
We revisit the derivation of the Rhoades-Ruffini bound [1] of 3.2 M⊙ for the upper limit of the maximum mass of neutron stars. We find that the assumption made there for the onset density of an ultimately stiff phase of high-density matter is not stringent. Relaxing this assumption and allowing for an onset of stiff non-nucleonic constant-speed-of-sound matter under neutron star constraints at the saturation density or below boosts the upper limit of the theoretically possible maximum mass to 4 M⊙ or higher. We provide a fit formula for the dependence of the maximum mass on the speed of sound and the onset density of the phase transition [2]. Our findings are relevant for discussing the nature of the so-called mass gap objects in the mass range between 2.5 and 5 M⊙.
[1] C.E. Rhoades and R. Ruffini, Maximum Mass of a Neutron Star, Phys. Rev. Lett. 32, 324 (1974) [2] D. Blaschke and A. Wójcik, Revisiting the Rhoades-Ruffini Bound, in preparation (2025)
Speaker: Prof. David Blaschke (David Blaschke1, 2, 3, ∗ and Adrian Wójcik1, † 1 Institute of Theoretical Physics, University of Wroclaw, Max Born Pl. 9, 50-204, Wroclaw, Poland 2Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany 3Center for Advanced Systems Understanding (CASUS), Untermarkt 20, 02826 Görlitz, Germany) -
12
Scalar vacuum densities on Beltrami pseudosphere
The combined effects of spatial curvature and topology are investigated on the properties of the vacuum state for a charged scalar field localized on the (2+1)-dimensional Beltrami pseudosphere. It is assumed that the field obeys the quasiperiodicity condition along azimuthal angle with a constant phase. As important local characteristics of the vacuum state the vacuum expectation values (VEVs) of the field squared and energy-momentum tensor are evaluated. The VEVs are decomposed into compactified and uncompactified parts. The contributions in the VEVs coming from geometry with an uncompactified azimuthal coordinate are divergent, whereas the compact counterparts are finite. The renormalization of the VEVs is reduced to that for the uncompactified parts only. As an important special case we have discussed the conformally coupled massless scalar field. The geometry for the Beltrami pseudosphere is conformally related to the (2+1)-dimensional Rindler spacetime and the corresponding VEVs of the energy-momentum tensor in these two spacetimes are conformally related as well. The topological contributions are analysed asymptotically for the limiting values of the ratio of radial coordinate and compactification length. This ratio corresponds to the inverse of the proper radius of the compactified dimension measured in units of the curvature radius. For small values of the ratio, the decay of the compact counterpart in the energy density follows a power-law. The effect of nontrivial topology is strong for the radial and azimuthal stresses at small values of the radial coordinate in the conformally coupled massless case. The nontrivial topology is essential also in the opposite asymptotic limit, where the magnitudes of VEVs are increasing by a power-law.
Speaker: Dr Tigran Petrosyan (Yerevan State University) -
13
Spherical orbits and shadows of Kerr black holes surrounded by quintessence
Spherical orbits around rotating black holes have a major astrophysical importance. In the presence of quintessential matter [1, 2], the geodesic equations can be investigated using a combined numerical-analytical approach [3]. One may notice significant differences compared to the results previously derived for Kerr black holes [4]. Also, as it is known, the rotating black holes produce shadows that differ significantly from those of nonrotating black hokes which are perfectly circular. By comparing the theoretically derived shadow’s observables with data on M87 and Sgr A from the Event Horizon Telescope, one may impose constraints on the black hole's parameters and highlight the impact of quintessence [5].
References
[1] V.V. Kiselev. Quintessence and black holes. Classical and Quantum Gravity. 20(6), 1187 (2003)
[2] B. Toshmatov, Z. Stuchlik and B. Ahmedov. Rotating black hole solutions with quintessential energy. European Physical Journal Plus 132(2), 98 (2017)
[3] M.A. Dariescu, V. Lungu, C. Dariescu and C. Stelea. Charged particles in the background of the Kiselev solution in power-Maxwell electrodynamics. Physical Review D 109(2), 024021 (2024)
[4] E. Teo. Spherical photon orbits around a Kerr Black Hole. General Relativity and Gravitation 35, 1909 (2003)
[5] S. Haroon et. al. Shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant. Physical Review D 99(4), 044015 (2019)Speaker: Prof. Marina-Aura Dariescu (Alexandru Ioan Cuza University of Iasi) -
Excursion and Social Dinner
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9
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14
Urca cooling of the neutron star in the Cassiopeia A supernova remnant
Observed cooling rate of the young neutron star (NS) in the Cassiopeia A supernova remnant (Cas A NS) exceeds theoretical expectations based on conventional scenarios of NS cooling, controlled mainly by modified Urca (mUrca) neutrino emission. Several hypotheses have been suggested to explain these observations. The most popular one assumes the cooling enhancement by neutrino emission due to the Cooper pair breaking and formation (PBF) just after the onset of neutron superfluidity in the NS core. This explanation requires strict constraints on critical temperatures of proton and neutron superfluidities in the NS core and on the efficiency of the PBF cooling mechanism. These constraints are in tension with the modern theory. To relax them, Lev Leinson (2022) suggested a hybrid cooling scenario, where the direct Urca (dUrca) process of neutrino emission from a small NS central kernel contributes to the cooling enhancement in addition to the PBF process. We show that Cas A NS cooling needs not to be hybrid, as the joint effect of Urca (dUrca+mUrca) processes can explain the observations equally well with or without superfluidity and the PBF mechanism. We explore the Urca scenario with different assumptions about NS equation of state, baryon superfluidity, and composition of the outer heat-blanketing envelope. We show that the observed cooling rate can be reproduced with many combinations of these assumptions by tuning the NS mass, which should slightly exceed the threshold mass for opening the dUrca process in the kernel. Then the core stays non-isothermal for centuries, delaying the onset of enhanced dUrca cooling to satisfy the Cas A NS observations. In addition, we present an analytic toy model which elucidates many features of the Urca scenario. The work was supported by the Russian Science Foundation Grant No.24-12-00320.
Speaker: Alexander Potekhin (Ioffe Institute) -
15
Some Aspects of the Neutron Star Cooling Mechanism
One of the key challenges in the theory of neutron star cooling is to explain the observed existence of compact relativistic objects of the same age but with different surface temperatures. To address this issue, we investigate the dependence of the neutrino cooling rate on the average density, mass, and internal structure of a neutron star. This study focuses on the medium modification of beta-decay processes in strongly interacting nuclear matter and their sensitivity to changes in density. Special attention is given to the softening of pions in nucleon-nucleon interactions, which affects the intensity of beta processes. The obtained results show good agreement with existing observational data.
Speaker: Dr Hovik Grigorian (JINR & AANL) -
16
The Cas A CCO: An observer's view
The compact object (presumably, a neutron star) at the center of the very young Cassiopeia A supernova remnant attracted a lot of attention because it possibly showed a fast cooling, much faster than in standard neutron star cooling theories. However, the conclusion about the fast cooling is based on observations with detectors that lose their sensitivity with time, and it involves some assumptions that are not always clearly spelled out in the papers. Having worked on the Cas A CCO observations since its discovery in 1999 and knowing firsthand the detector properties, we will present our current view on observed properties of this fascinating object.
Speaker: George Pavlov -
10:30
Coffee break
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17
On peculiar Gaia neutron star binaries
Gaia detected a new population of neutron stars. They are the oldest neutron stars known, which are members of wide binaries with small orbital velocities. I argue that their current orbits are fossils of their turbulent youth and present considerable clues to the physics of their younger selves.
Speaker: Yuri Levin (Columbia University) -
18
Neutrinos in dense matter: beyond modified Urca
Neutrino absorption and emission (the "Urca process") is an essential aspect of the formation and cooling of neutron stars and of neutron star mergers. In this talk I will describe the traditional way of calculating Urca rates, explain its shortfalls, and propose an alternative approach, the nucleon width approximation.
Speaker: Prof. Mark Alford (Washington University, St Louis) -
19
Bulk Viscosity of Two-Flavor Color Superconducting Quark Matter in Neutron Star Mergers
This work investigates the bulk viscosity of warm, dense,
neutrino-transparent, color-superconducting quark matter, where
damping of density oscillations in the kHz frequency range arises
from weak-interaction-driven direct Urca processes involving
quarks. We study the two-flavor red-green paired
color-superconducting (2SC) phase, while allowing for the presence
of unpaired strange quarks and blue color light quarks of all
flavors. Our calculations are based on the SU(3) Nambu-Jona-Lasinio
(NJL) model, extended to include both vector interactions and the
't Hooft determinant term. The primary focus is on how variations in
the NJL Lagrangian parameters - specifically, the diquark and vector
coupling strengths - affect both the static properties of quark
matter, such as its equation of state and composition, and its
dynamical behavior, including bulk viscosity and associated damping
timescales. We find that the bulk viscosity and corresponding
damping timescale can change by more than an order of magnitude upon
varying the vector coupling by a factor of two at high densities and
by a lesser degree at lower densities. This sensitivity primarily
arises from the susceptibility of 2SC matter, with a smaller
contribution from modifications to the weak interaction rates. In
comparison, changes in the diquark coupling have a more limited
impact. The damping of density oscillations in 2SC matter is similar
quantitatively to nucleonic matter and can be a leading mechanism of
dissipation in merging hybrid stars containing color superconducting
cores.Speaker: Dr Arus Harutyunyan (Byurakan Astrophysical Observatory, Yerevan State University) -
Lunch break
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20
Gapless superfluidity and neutron stars
Born from gravitational-core collapse supernovae, with initial temperatures as high as $\sim 10^{12}$K, neutron stars cool down to temperatures $10^9$ K within a few days, providing a unique opportunity to explore matter under extreme conditions. In particular, neutron stars contain nuclear superfluids whose presence is supported by observations of pulsar frequency glitches, rapid decline in luminosity of the Cassiopeia A remnant, and crust cooling of neutron stars in low-mass X-ray binaries.
Despite the importance of the superfluid dynamics in interpreting these astrophysical phenomena, most microscopic calculations of the nuclear pairing properties have been carried out so far for static situations. We have recently studied the dynamics of hot neutron-proton superfluid mixtures within the time-dependent nuclear energy-density functional theory [1,2].
The disappearance of superfluidity has also been investigated and reveals the presence of a dynamical "gapless" state in which nuclear superfluidity is not destroyed even though the energy spectrum of quasiparticle excitations exhibits no gap. The absence of an energy gap affects considerably the neutron specific heat which becomes very different from that in the classical BCS state (in the absence of superflows) [3]. Implications for the crust cooling of neutron stars in low-mass X-ray binaries will be discussed, as well as the consequences of gapless superfluidity for neutron vortex dynamics [4].
[1] N. Chamel & V. Allard, Phys. Rev. C 100, 065801 (2019).
[2] V. Allard & N. Chamel, Phys. Rev. C 103, 025804 (2021).
[3] V. Allard & N. Chamel, Phys. Rev. C 108, 045801 (2023).
[4] V. Allard & N. Chamel, Phys. Rev. Lett. 132, 181001 (2024)Speaker: Valentin Allard (Warsaw University of Technology) -
21
Monistic modification of Einstein's geometrical physics
The pseudo-Riemann metric organization of spacetime can describe the quasi-elastic field hierarchy with the constant rest energy integral in the case of negligible inelastic losses or non-metric intrusions. Visible matter consists of very dense regions of massive fields associated with the material analogue of the Einstein tensor. The non-Schwarzschild metric solution of the non-dual analogue of the Einstein equation preserves the Euclidean 3 geometry for the inhomogeneous matterspace continuum and describes post-Newtonian gravity in line with known measurements. Locally dilated time in a nonlocal field hierarchy generates a primary reason for holistic mass densities and their auto-accelerations, rather than distant gravitational pulls in the dualistic alternative of pairwise interactions. Precise measurements can distinguish between the monistic and dualistic nature of observable astrophysical phenomena.
Speaker: Dr Igor Bulyzhenkov (Space Research Institute RAS) -
22
Massless Bose Particles -Hions and the Possibilities of Real Space-Time Engineering 113
113
Yerevan, Armenia
Department of Physics, Alex Manukyan str. 1, Yerevan, ArmeniaRecently, within the framework of the stochastic Yang-Mills equations for the gauge symmetry group SU(2)xU(1), the possibility of the evidence of massless Bose particles with spin-1- The formation of a scalar field from an ensemble of chions as a result of Bose condensation of entangled pairs of chions with a common spin of 0 is theoretically substantiated. has been proven [1]. The formation of a scalar field from an ensemble of hions as a result of Bose condensation of entangled pairs of hions with a common spin of 0 is theoretically substantiated. In such a field, pairs of hions are not entangled, but the system is assumed to have a net zero spin on fairly small spatial scales. The main goal of our experiment was to demonstrate the possibility of manipulating the refractive indices of empty space (vacuum) by external influence on the vector field and thereby prove the reality of implementing space-time engineering. Recall that when speaking about space-time engineering, scientists usually mean manipulating the structure of space-time itself. Such possibilities are usually associated with so-called wormholes, which can appear in the fabric of space-time according to Einstein's general theory of relativity and connect remote regions of space in the shortest possible way. It is obvious that only supernatural beings are capable of creating and controlling such technologies, and it is doubtful that even in the distant future humanity will be able to master such technologies. However, changing and controlling space-time remains one of the greatest problems of modern quantum physics, and even its partial solution can lead to incredible technological development of human civilization. As is well known, light passing through one slit form a diffraction pattern. We modified this experiment by placing a cylinder behind the diffraction slit, on which a light guide is wound. When two independent low-power laser sources of the visible range of light are switched on, one of which falls on the slit and the other propagates along the light guide, a redistribution of light intensity is observed in individual diffraction zones. Moreover, as precision measurements of light intensity in various diffraction zones have shown, in individual pixels the change in light intensity relative to the normal value amounts to tens of percent. Moreover, as precision measurements of light intensity in various diffraction zones have shown, in individual pixels the change in light intensity relative to the normal value amounts to tens of percent. This effect is so significant that it cannot be explained within the framework of classical or quantum electrodynamics. Latter indicates the formation of a phase object of a complex structure on the path of propagation of a diffracting light beam and, accordingly, a new, still unknown type of polarization of the quantum vacuum. As multilateral analysis and numerical estimates show, such polarization can arise as a result of reorientation of hions spins under the action of an external electromagnetic field.
In other words, this experiment indirectly proves the existence of hions that form physical space itself, the possibility of manipulating them with the help of external influences and, accordingly, the implementation of space-time engineering.
[1] A.S. Gevorkyan, Quantum Vacuum: The Structure of Empty Space–Time and Quintessence with Gauge Symmetry Group SU(2)xU(1), Particles, 2019, Vol. 2(2), pp. 281-308; doi:10.3390/particles2020019Speaker: Mr Grigor Movsesyan (Institute for Informatics and Automation Problems of the National Academy of Sciences of the Republic of Armenia, 1 P. Sevak Str., Yerevan, Republic of Armenia, 0014) -
23
Matrix kinetic equation approach to calculation of neutrino emission accompanying formation of Cooper pairs in superfluid neutron star matter
One of the important processes leading to neutrino emission from the interior of superfluid neutron stars is the process of neutrino emission during Cooper pairing of neutrons. When calculating the neutrino emissivity in this process, it is necessary to correctly consider the self-consistent response of the superfluid condensate. Such an analysis for spin-singlet pairing was carried out by many authors and for the spin-triplet case in a series of works by L.B. Leinson in the long-wavelength limit. All these calculations are based on relatively cumbersome equations within the framework of the Larkin-Migdal-Leggett theory or related approaches. We show that neutrino emission due to Cooper pair formation can be correctly calculated within a somewhat simpler formalism based on the use of the matrix kinetic equation for a superfluid Fermi system, which automatically respects the vector current conservation. The results for different types of pairing can be obtained within the same formalism and here it is applied to the cases of ${}^1S_0$, ${}^3P_2$, and ${}^3P_0$ types of pairing. In the limiting cases the previous results are reproduced.
The work is supported by Russian Science Foundation # 24-12-00320.Speaker: Petr Shternin -
24
Quantum Description of the Motion of a Single Photon and Its Stability 113
113
Yerevan, Armenia
Department of Physics, Alex Manukyan str. 1, Yerevan, ArmeniaABSTRACT
Until now, the theory of quantum mechanics of the photon has not been sufficiently developed; moreover, the idea of the wave function of the photon is often considered a controversial concept, see, for example [1]. Note that for the photon, there is only the quantum theory of the electromagnetic radiation, which, except for the frequency or wavelength, does not provide any other information about the space-time structure and other properties of the photon [2]. The main reason for the difficulties is that photons are never non-relativistic and can be freely emitted and absorbed, therefore there is no law of conservation of the number of photons, which makes its description within the usual paradigm of quantum mechanics, if not impossible, then very difficult. Meanwhile, theoretical attempts to determine the wave functions of the photon have a rich history and date back to the time of the formation of quantum mechanics itself [3]. It is important to note that quantum mechanics, which aims to give a complete description of various natural phenomena, must be able to describe such a fundamental physical particle as a photon, which cannot be done without formulation the concept of a particle's wave function. Recall that for the photon, there is only the quantum theory of electromagnetic radiation, which, apart from the frequency or wavelength, does not provide any other information about the space-time structure and other properties of the photon, while the cross-sections of all processes involving photons are determined by its space-time structure [2]. The problem is becoming increasingly important due to the rapid growth in the number of experiments on the generation and detection of single photons, related to such important areas as quantum computing and quantum cryptography, quantum measurements, quantum communications and other ultra-sensitive quantum technologies, see for example. The study of the structure of the photon and its evolution during large spatial transitions can be important and informative also from the point of view of astrophysics problems.
To study and solve these problems, we considered the wave function of a single photon within the framework of the SU(2)xU(1) gauge symmetry group using the Yang–Mills equations for Abelian fields [4]. The wave equation of a photon as a complex probabilistic process is investigated and, in the limit of statistical equilibrium, the mathematical expectation of its wave state is obtained taking into account relaxation on space-time fluctuations. The role of hions in the formation of the space-time structure of a photon during its “long stay in vacuum” is studied in detail.
[1] Bialynicki-Birula,I., 1995, On the photon wavefunction Coherence and Quantum Optics VII eds 495 Eberly J.H., Mandel L. and Wolf E. (New York: Plenum) p313.
[2] Akhiezer, A.I., and Berestetskii, V.B. 1965, Quantum Electrodynamics, (Interscience, New York), Ch. 497 1.
[3] Dirac, P. A. M., 1958, The Principles of Quantum Theory 4th ed. (Clarendon Press, Oxford) p. 9.
[4] Gevorkyan, A.S., Quantum Vacuum: The Structure of Empty Space–Time and Quintessence with Gauge Symmetry Group SU(2)xU(1), Particles, 2019, Vol. 2(2), pp. 281-308; doi:10.3390/particles2020019Speaker: Prof. Ashot Gevorkyan (Institute for Informatics and Automation Problems NAS of RA) -
25
Superfluid fraction in the inner crust of neutron stars
The question of whether there are enough superfluid neutrons in the inner crust of neutron stars to explain pulsar glitches remains a topic of debate.
Previous band structure calculations suggest that the entrainment effect significantly reduces the superfluid density.
In this talk, HFB calculations are presented and a new derivation of the BCS expression for the superfluid density is given.
These results suggest that about 90% of the neutrons are effectively superfluid, making possible to explain glitches with models that involve the crust only.Speaker: Giorgio ALMIRANTE -
Coffee break
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26
Inferring Nuclear Symmetry Energy from Nuclear Experiment and Neutron Star Observations
The energy density functional for dense nuclear matter can be presented as the sum of two parts. The isospin-symmetric part determines the equation of state of symmetric nuclear matter. The isospin-asymmetric part is commonly considered to be proportional to the squared isospin asymmetry, with the proportionality coefficient referred to as the nuclear symmetry energy. There are two ways to probe nuclear matter properties at densities well above the saturation point. Observations of neutron star properties such as mass and radius constrain the beta equilibrium equation of state of superdense matter, while laboratory experiments on heavy-ion collisions provide the equation of state of symmetric nuclear matter. Neither of these approaches alone allows one to determine the nuclear symmetry energy at high densities. However, by combining them as input for the inverse beta-equilibrium problem, one can infer the symmetry energy as a function of baryon number density in a model-independent way. This idea was proposed several years ago [1] for minimum-composition (npe) nuclear matter. In this work, we extend it to the realistic npe\mu composition of the neutron star core. Using renowned heavy-ion collision data [2] and state-of-the-art astrophysical observations [3], we reconstruct the symmetry energy—baryon density relation with remarkable accuracy. The resulting inferences on particle fractions strongly support the operation of the direct Urca neutrino emission process in neutron stars.
[1] Li B.-A., Xie W.-J., 2020, PhLB, 806, 135517
[2] Danielewicz P., Lacey R., Lynch W. G., 2002, Sci, 298, 1592
[3] Rutherford N. et al., 2024, ApJL, 971, L19Speaker: Dr D. D. Ofengeim (Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel) -
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Thermoelectric coefficients of two-flavor quark matter from the Kubo formalism
This work investigates thermoelectric coefficients (electrical and thermal conductivities and thermoelectric power) of two-flavor quark matter from the Kubo formalism within the framework of the Nambu–Jona-Lasinio model. The subject of the study is quark matter under physical conditions relevant to heavy-ion collisions, where electric fields and temperature gradients are present simultaneously.
We evaluate the relevant two-point equilibrium correlators by using the Matsubara technique of the thermal field theory and applying the $1/N_c$ expansion to the multi-loop Feynman diagrams. The quark spectral functions derived previously from the one meson-exchange diagram for on-mass-shell quarks are employed.
Numerical results show that conductivities decrease with the temperature, whereas the thermopower showes the opposite behavior, thus enhancing system's capability of generating electrical voltage when subjected to a thermal gradient.Speaker: Harutyun Gabuzyan (Yerevan State University) -
28
Electrical conductivity for hot and dense astrophysical plasma
We investigate the electrical conductivity of hot and dense plasma relevant to the outer crusts of neutron stars and the interiors of white dwarfs. The main novelty of the work is the inclusion of positrons in the composition of matter and in the transport. We solve a system of coupled Boltzmann kinetic equations for electrons' and positrons' distribution functions in the relaxation time approximation, taking into account the electron-ion, positron-ion and electron-positron collisions. The relevant scattering matrix elements are calculated from one-plasmon exchange diagrams with the inclusion of in-medium polarization tensors derived within the hard-thermal-loop effective theory. Preliminary numerical results are obtained for matter consisting of carbon nuclei. We found that the conductivity rises with the temperature following a power-law $\sigma\propto T^4$ in the nondegenerate regime because of intense creation of thermal electron-positron pairs.
These results highlight the importance of inclusion of positrons in the transport of heated dense astrophysical plasmas.Speaker: Tigran Petrosyan (Yerevan State University) -
29
Thermoelectric effects in neutron star inner crusts in magnetic fields
We study the thermal conductivity and thermoelectric power of the inner crust of a neutron star at finite temperatures where ions are in a liquid state. Such crust can be formed in various astrophysical scenarios including binary neutron star mergers, proto-neutron stars and accreting neutron stars. We employed the linearized Boltzmann equation assuming simultaneous presence of electromagnetic fields and gradients of temperature and chemical potential. In the electron–ion collision integral the finite nuclear size, the ion–ion correlations and the Debye screening were taken into account. Numerical results were obtained for five compositions of the inner crust, showing the dependence of the thermal conductivity and thermoelectric power on the mass density, temperature and magnetic field. In addition, the timescales of magnetic field evolution were estimated in order to assess the importance of thermoelectric phenomena in the evolution of crustal magnetic fields.
Speaker: Henrik Danielyan (Yerevan State University) -
30
Motion of test particles around a magnetized black hole surrounded by quintessence
We investigate the dynamics of test particles near a magnetized black hole surrounded by quintessence which is modeled as an anisotropic fluid with a specific equation of state [1,2]. The motion of both massive and massless test particles is analyzed using the Lagrangian formalism, with particular focus on the effective potential governing their trajectories. Quintessence modifies the spacetime curvature at large distances, while the magnetic field introduces Lorentz-like forces acting on charged particles[3,4]. We determine the conditions for the existence and stability of circular orbits and examine how the quintessence and magnetic field parameters influence the location of the innermost stable circular orbit (ISCO) and the presence of bounded trajectories. Our findings highlight the intricate interplay between dark energy effects and magnetic interactions, offering potential insights for astrophysical observations near active galactic nuclei and magnetized black holes.
Speaker: Vitalie Lungu (Alexandru Ioan Cuza University of Iasi)
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How well can we infer the magnetic field strengths of neutron stars?
The magnetic field strengths of neutron stars are typically inferred from pulse timing, relying on a model for the electromagnetic braking torque. I will provide a theoretical overview for the various pieces of physics that adjust this torque, relating to general-relativistic effects, the equation of state, magnetospheric conditions, and dynamical phenomena, arguing that actually there is a huge uncertainty on the inferred magnetic field strength when all is taken into account. Given that many models for neutron-star phenomena depend sensitively on the field strength, we will investigate how these uncertainties affect what we can learn from observations.
Speaker: Arthur Suvorov (University of Alicante) -
32
QCD Dynamics of the Nuclear Core and Stability of Nuclear Matter
One of the important properties of nuclear forces is
the nuclear repulsive core which provides a stability for atomic nuclei, making
possible the emergence of a structure for the visible matter.
However the origin of the nuclear core is poorly understood. We discuss how
the strong repulsive nuclear core at short distances can emerge from QCD,
even though one should expect a diminishing interaction due to asymptotic freedom.
It is demonstrated that such a repulsion is associated with the non-nucleonic component in
the NN system and we demonstrate how to incorporate non-nucleonic components in the calculation of
nuclear structure at extremely short distances. We also elaborate the approach that the presented
calculations can be extended to infinite nuclear matter at high densities.Speaker: Misak Sargsian (Florida International University) -
10:30
Coffee break
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Can rotation solve the Hubble puzzle?
The discrepancy between low and high redshift Hubble constant $H_0$ measurements is the highest significance tension within the concordance Lambda cold dark matter paradigm. If not due to unknown systematics, the Hubble Puzzle suggests a lack of understanding of the universe’s expansion history despite the otherwise spectacular success of the theory. We show that a Gödel inspired slowly rotating dark-fluid variant of the concordance model resolves this tension with an angular velocity today $\omega_0\approx 2\times 10^{−3 }\mathrm{Gyr}^{−1}$. Curiously, this is close to the maximal rotation, avoiding closed time-like loops with a tangential velocity less than the speed of light at the horizon.
Speaker: Gergely Barnafoldi (Hungarian Academy of Sciences (HU)) -
34
Instability windows of relativistic r-modes in neutron stars with hyperonic cores
R-modes are quasitoroidal oscillations of rotating stars, primarily restored by the Coriolis force. The fact that, among the variety of stellar oscillations, r-modes are the most susceptible to the Chandrasekhar-Friedman-Schutz (CFS) instability (i.e., instability with respect to gravitational wave emission) makes them promising targets for current and future gravitational wave searches. An r-mode becomes unstable if the energy supply to the mode by the CFS mechanism surpasses the energy losses caused by various dissipative mechanisms operating in the stellar matter. The corresponding stellar parameters - typically, rotation rate $\Omega$ and (redshifted) temperature $T^\infty$ - determine the so-called r-mode instability window on the $(\Omega, T^\infty)$ plane. At high temperatures, bulk viscosity $\zeta$, arising from out-of-equilibrium chemical reactions, is the dominant dissipative mechanism that opposes the CFS instability. Dissipation through $\zeta$ can be substantially enhanced by two independent mechanisms: (1) the presence of hyperons, which significantly increases the bulk viscosity coefficient, and (2) peculiar properties of relativistic r-modes in nonbarotropic matter, which strongly amplify their dissipation through bulk viscosity compared to that in Newtonian theory. In this study, we present the first investigation of the combined impact of these two mechanisms on the r-mode instability windows. Our calculations also estimate the effect of nucleon pairing on the instability windows and investigate the importance of accounting for chemical reactions in the adiabatic index of the matter. We find that hyperonic bulk viscosity is a much more efficient dissipative mechanism than previously thought and that it may provide the dissipation required to stabilize r-modes in the fastest-spinning and moderately hot neutron stars in low-mass X-ray binaries, even when nucleon pairing effects are taken into account. These results have important implications for the interpretation of observations and for the broader understanding of relativistic r-mode physics.
This research was supported by Russian Science Foundation [Grant 22-12-00048-P, https://rscf.ru/project/22-12-00048/].
Speaker: Mr Kirill Kraav (Ioffe Institute) -
35
Accretion channels of subcritical X-ray pulsars: a study of hydrodynamics and radiation
We present the results of self-consistent radiation-hydrodynamic modeling of accretion channels of subcritical X-ray pulsars. The process of resonant Compton scattering and vacuum polarization is taken into account. It is shown that the radiation in the cyclotron line is determined by the hydrodynamic characteristics of the flow in the accretion channel and the position of the cyclotron line centroid has a positive correlation with the plasma deceleration degree, which corresponds to the observational data. In addition, we investigate the polarization of the X-ray radiation outgoing from the accretion channel.
The work of IDM was supported by the Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS”Speaker: Ivan Markozov (Ioffe Institute, IKI RAS) -
Lunch break
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Best Talk/Presentation Award from "Symmetry" and "Particles" Journals
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37
Electromagnetic Properties of Stellar Matter. The Transverse Dielectric Permeability of the Protoquark Star Matter.
Some electromagnetic properties of the protoquark star matter are investigated. It is assumed that during the formation of the protoquark star, the matter of the initial star was already opaque for neutrinos. Thus, this process was accompanied by the conservation of the total lepton charge. The lepton charges of the protoquark star and the initial star are almost equal. In our numerical calculations, the value of the lepton charge per baryon is taken to be 0.4. The thermodynamic characteristics of the hot quark matter during neutrino confinement are determined according to the NIL model. For different values of temperature T∈[20÷100] MeV and baryon charge density $n_B∈[0÷1.8]$ fm$^{-3}$ in the hydrodynamic approximation, plasma frequencies of the quark matter are calculated. The spectrum and energy density of the equilibrium thermal radiation in the matter are also calculated. Although the plasma frequencies of the matter in the proto-quark star are very high, the spectrum of the thermal equilibrium radiation in the temperature range T∈[20÷100] MeV is distorted insignificantly. This cannot be said about a cooled quark star. This is very important for calculating the thermal energy reserves of the proto-quark star.
Speaker: Prof. Gevorg Hajyan (Yerevan State University) -
38
Fastest spinning millisecond pulsars: indicators for quark matter in neutron stars?
We study rotating hybrid stars, with a particular emphasis on the effect of a deconfinement phase
transition on their properties at high spin. Our analysis is based on a hybrid equation of state with
a phase transition from hypernuclear matter to color-superconducting quark matter, where both
phases are described within a relativistic density functional approach. By varying the vector meson
and diquark couplings in the quark matter phase, we obtain different hybrid star sequences with
varying extensions of the quark matter core, ensuring consistency with astrophysical constraints
from mass, radius, and tidal deformability measurements. We test whether the early deconfinement
phase transition is consistent with the present observational data. We show how the fastest spinning
pulsars and the appearance of the quasi-radial oscillations and non-axisymmetric instabilities constrain the strongly interacting matter equation of state at zero temperature. Our findings reveal that
incorporating the hybrid equation of state into the analysis of pulsars has significant implications
for the constraints on the properties of strongly interacting matter and neutron stars which is of the
high interest for the future SKA observations.Speaker: Christoph Gärtlein (University of Lisbon, University of Wroclaw, University of Coimbra) -
39
On the quasi-periodic variations of period derivatives of pulsars
Observed data about quasi-periodic variations of period derivative of pulsars is considered. Characteristic radii of superfluid regions of pulsars are derived under the assumption that these variations are collective elastic oscillations of the superfliud vortex lattice (Tkachenko oscillations). The found values of radii are compared with values derived from X-ray data NICER and XMM-Newton X-ray satellites. These values are also compared with the values, obtained from equation of state. Simple model of Tkachenko oscillations requires further clarification. This method can be used for the approximate evaluation of radii of some pulsars.
Speaker: Prof. Karen Shahabasyan (Yerevan State University) -
40
Exotic Matter and the Neutron Star EOS: Observational Signatures of Hyperons, Bosonic Dark Matter, and Quark Matter
The presence of dark matter in neutron stars is of growing interest due to its possible impact on their structure and observables. Among proposed candidates, the hypothetical sexaquark has emerged as a promising bosonic dark matter particle, potentially forming under extreme conditions in neutron star cores.
We investigate this scenario using a relativistic density functional approach, including hyperons (DD2Y-T model) for the hadronic phase, coupled to a deconfined quark phase described by a non-local Nambu-Jona-Lasinio model.
The phase transition is modeled through a smooth crossover, and sexaquark-baryon interactions
are introduced via an effective mass shift representing repulsion.
We assess whether this hybrid scenario, incorporating hyperons, bosonic dark matter, and deconfined quark matter,
is consistent with multi-messenger constraints from neutron stars. By scanning the parameter space,
we identify sexaquark masses that are consistent with mass-radius measurements and tidal deformability.
Our results show that the presence of the sexaquark softens the equation of state, enabling the model to satisfy both the radius and tidal deformability constraints around the canonical $1.4M_\odot$ neutron stars.
We incorporate all available NICER data, including PSR J0437-4715 and newly published PSR J0614-3329.
We find out that hybrid stars with sexaquark mass near 1900 MeV agree with all current observational limits,
including HESS J1731-347 and PSR J0952-0607, representing the lightest and most massive known neutron stars.
Furthermore, we perform a Bayesian analysis, which yields a favored sexaquark mass range of 1885-1935 MeV, supporting the potential role of this exotic particle in the interiors of neutron stars.Speaker: mahboubeh shahrbaf motlagh -
41
The impact of non-zero quark masses on the Equation of State and the Maximum Mass of Strange Quark Stars
This study explores the equations of state for strange quark matter as a superdense ground state within the MIT bag model, considering both fixed and baryon density–dependent parameters. We examine the structure of cold, self-bound strange stars capable of reaching masses above two solar masses, forming a continuous family with neutron stars along the mass–central density (M(ρ_c)) relation. The primary aim is to compare these theoretical mass predictions with recent precise pulsar mass measurements. By solving the Tolman–Oppenheimer–Volkoff equations numerically, we evaluate two scenarios: (1) fixed bag model parameters m_s,α_c,B; (2) fixed m_s,α_c with B=B(n_B). In this discussion, we address the solutions to the equations of state and subsequently examine the relativistic equations governing compact stars, incorporating the non-zero masses of first-generation quarks. Using numerical calculations based on their experimentally determined values with specified accuracy, we analyze the resulting relationships between these parameters and the various physical quantities.
Speaker: Dr Hasmik Shahinyan (Yerevan State University) -
42
X-ray pulse profile as a new probe for dark matter halo around neutron stars
X-ray telescopes—NICER, eXTP, ATHENA, and STROBE-X—offer a promising probe of the structure of compact objects such as neutron stars. A dark-matter halo surrounding these objects alters the local space-time and, in turn, affects light propagation. In this work, we examine the impact of forming a self-interacting bosonic dark-matter halo around neutron stars, aiming to identify signatures that may shed light on the nature of dark matter.
Speaker: Mr Davood Rafiei Karkevandi (University of Wroclaw, Institute of Theoretical Physics) -
Coffee break
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Beyond Current Limitations: A New Approach to the Neutron Star Equation of State
The neutron star equation of state (EOS) remains one of the fundamental challenges in nuclear astrophysics, with current modeling approaches facing distinct limitations. Phenomenological models, while successful in reproducing nuclear and astrophysical constraints, suffer from inherent model dependencies in their parametrizations. These dependencies can introduce biases in posterior distributions when constraining neutron star properties from observational data, potentially affecting our interpretation of multi-messenger observations.
Model-independent and agnostic frameworks attempt to overcome these limitations through increased flexibility, but this comes at the cost of reduced physical interpretability and increased systematic uncertainties. The tension between flexibility and physical consistency presents a fundamental challenge: how can we develop EOS models that are both sufficiently flexible to capture diverse astrophysical constraints and physically motivated enough to provide meaningful insights into dense matter?
We present a new framework that addresses these challenges by combining the strengths of both approaches. Our method maintains theoretical consistency while achieving the flexibility necessary for modern astrophysical applications. By carefully constructing a framework that respects fundamental nuclear physics principles without being overly restrictive, we demonstrate improved performance in capturing current observational constraints across the full neutron star mass range.
This work suggests that next-generation EOS modeling can move beyond the traditional dichotomy between phenomenological and agnostic approaches, offering new pathways for leveraging multi-messenger observations to constrain the properties of matter at extreme densities.Speaker: Tuhin Malik (CFisUC, Department of Physics, University of Coimbra, Portugal) -
44
Is the Central Compact Object in HESS J1731-347 a Hybrid Star ?
The recent identification of the compact object in HESS J1731-347, with a remarkably low mass of M~0.77 solar mass and radius R~10.4 km, challenges the conventional understanding of dense matter. Such a light and compact star points to the necessity of a softer equation of state (EoS), in tension with the requirement of a stiff EoS to support massive pulsars above 2 solar mass. In this work, we investigate the possibility that HESS J1731-347 may be realized as a hybrid star (HS) containing deconfined quark matter in its inner core. Within the Constant Speed of Sound (CSS) parametrization, we systematically study the influence of individual parameters and hadronic properties-such as the effective nucleon mass, nuclear symmetry energy, and its slope at saturation - on the stability and structure of such low-mass compact stars. Our analysis shows that, at the 1 sigma credible level, HESS J1731-347 is consistent with a stable HS featuring early deconfinement and a sizable energy gap.
We further extend this framework by including dark matter (DM) interactions in both the hadronic and quark sectors, examining their role in modifying stellar properties. The presence of DM inside hybrid stars leads to significant modifications in the mass–radius relation and opens new possibilities for explaining the observed properties of HESS J1731-347.
Overall, our results suggest that the combined effects of dense matter physics, phase transitions, and DM interactions provide a viable path toward reconciling low-mass compact star observations with the existence of massive pulsars.
Speaker: Suman Pal (Variable Energy Cyclotron Centre (VECC)) -
45
How does isospin asymmetry influence the onset of quark matter
In contrast to symmetric nuclear matter, which has been extensively studied in laboratory experiments, the matter inside neutron stars is highly isospin-asymmetric. We investigate the properties of strongly interacting matter under both symmetric and neutron-star-like conditions to determine how electric charge neutrality and beta equilibrium influence the emergence of quark matter. In particular, we establish a relation between the quark onset density in electrically neutral, beta-equilibrated matter and that in symmetric matter. This relation is demonstrated across a broad class of hybrid equations of state and reveals a significant reduction in the quark onset density in highly asymmetric regimes. These findings are further tested through Bayesian analyses of astrophysical measurements, underscoring their relevance for dense matter. A direct consequence of our finding is
that a lower-limit constraint on the deconfinement transition in symmetric nuclear matter may imply that this transition could occur in neutron stars at densities even below nuclear saturation density. This study is of significant importance to both the heavy-ion collision and neutron star communities.Speaker: Mr Pavlo Panasiuk (University of Coimbra) -
46
Equation of state of superdense matter from future high-precision neutron star radius measurements
To more precisely constrain the Equation of State (EOS) of supradense neutron-rich nuclear matter, future high-precision X-ray and gravitational wave observatories are proposed to measure the radii of neutron stars (NSs) with an accuracy better than about 0.1 km. However, it remains unclear what particular aspects (other than the stiffness generally spoken of in the literature) of the EOS and to what precision they will be better constrained. In this talk, within a Bayesian framework using a meta-model EOS for NSs, we discuss what aspects of nuclear EOS can (and what can not) be better constrained by future high-precision NS radius measurements. In particular, we infer the posterior probability distribution functions (PDFs) of incompressibility $K_{0}$ and skewness $J_{0}$ of symmetric nuclear matter (SNM) as well as the slope $L$, curvature $K_{\rm{sym}}$, and skewness $J_{\rm{sym}}$ characterizing the density dependence of nuclear symmetry energy $E_{\rm{sym}}(\rho)$, respectively, from mean values of NS radii consistent with existing observations and an expected accuracy $\Delta R$ ranging from about 1.0 km to 0.1 km. Effects of high-precision NS radius measurements on determining properties of first-order hadron-quark phase transition will also be discussed.
Speaker: Prof. Bao-An Li (East Texas A&M University)
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