Article
Astronomy & Astrophysics
Minghua Wei, Chowdhury Aminul Islam, Mei Huang
Summary: Using current-current correlation function, the photon polarization tensor is computed for a rotating hot and dense QCD medium. The spectral function and dilepton rate are then estimated, showing enhancement in a rotating medium, especially at low invariant masses. The effects of angular velocity, temperature, and chemical potential on the spectral function and dilepton rate are explored. Electromagnetic screening is also investigated, with the calculation of Debye mass indicating suppression in a rotating QCD medium. The most interesting observation is the azimuthal anisotropy of dilepton production, where the elliptic flow v(2) induced by rotation as an external field exhibits a convex down behavior in the transverse momentum, due to competition between centrifugal effect and spin polarization effect.
Article
Astronomy & Astrophysics
Tuhin Malik, Marcio Ferreira, B. K. Agrawal, Constanca Providencia
Summary: The general behavior of the nuclear equation of state (EOS) relevant for neutron stars is studied using a Bayesian approach. A set of models based on a density-dependent relativistic mean-field description of nuclear matter is used. The EOS is subjected to minimal constraints based on nuclear saturation properties and a precise calculation in chiral effective field theory. The posterior distributions of the model parameters are used to construct the distributions of various nuclear matter and neutron star properties. The results are found to be compatible with observed data without invoking exotic degrees of freedom.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Peng-Cheng Qiu, De-Liang Yao
Summary: The chiral effective meson-baryon Lagrangian for interactions between doubly charmed baryons and Goldstone bosons is constructed up to q(4) order. A total of 8, 32, and 218 linearly independent invariant monomials of O(q(2)), O(q(3)), and O(q(4)) are considered. This Lagrangian allows for studying the chiral dynamics and relevant phenomenology of doubly charmed baryons at complete one-loop level, and also includes a discussion on the nonrelativistic reduction of the Lagrangian for completeness.
Article
Physics, Particles & Fields
N. Er, K. Azizi
Summary: The spectroscopic parameters and electromagnetic form factor of the strange particle kaon are investigated in both vacuum and a medium with finite density. The study provides consistent results with existing experimental data for the vacuum mass and decay constant of the kaon. The behavior of the kaon's electromagnetic form factor is found to be in agreement with predictions from lattice QCD and the Nambu-Jona-Lasinio model, as well as with experimental results for the vacuum radius. The study also explores the effects of higher densities on various parameters and provides comparisons with predictions from other models and approaches. These findings are important for future experimental and theoretical studies in both vacuum and dense media.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Parada T. P. Hutauruk, Seung-il Nam
Summary: This study uses the NJL model and PTR scheme to investigate the properties of pions and kaons in a nuclear medium at nonvanishing temperature, as well as the relationship between QCD chiral condensates and baryon density. The findings show that QCD chiral condensates decrease with increasing temperature and baryon density, but increase in the presence of a magnetic field. Additionally, the wave function renormalization factors for pions and kaons increase with temperature, but decrease with increasing baryon density.
MODERN PHYSICS LETTERS A
(2022)
Article
Astronomy & Astrophysics
J. P. Carlomagno, D. Gomez Dumm, N. N. Scoccola
Summary: The study uses a nonlocal PNJL model to analyze the features of strongly interacting matter in the presence of nonzero isospin chemical potential, describing the behavior of thermodynamic quantities and studying the phase diagram in the mu(I) - T plane. It is found that the system may be in an isospin symmetry broken phase under certain conditions, with results for the phase diagram being in better agreement with lattice QCD calculations than other theoretical approaches such as the local PNJL model.
Article
Astronomy & Astrophysics
Gilberto Colangelo, Martin Hoferichter, Bastian Kubis, Malwin Niehus, Jacobo Ruiz de Elvira
Summary: This study investigates the pion-mass dependence of the two-pion channel in the hadronic-vacuum-polarization (HVP) contribution to the anomalous magnetic moment of the muon a(mu)(HVP). The researchers utilize an Omnes representation for the pion vector form factor with the phase shift derived from the inverse-amplitude method (IAM). The findings provide constraints on the dominant isospin-1 part of the isospin-symmetric light-quark contribution and offer improved control over the chiral extrapolation of a(mu)(HVP), which is essential for lattice-QCD calculations performed at larger-than-physical pion masses.
Article
Astronomy & Astrophysics
Carlos Hoyos, Niko Jokela, Matti Jarvinen, Javier G. Subils, Javier Tarrio, Aleksi Vuorinen
Summary: The transport properties of dense QCD matter, important in the physics of neutron stars and their mergers, are difficult to study using traditional quantum field theory tools. This study focuses on unpaired quark matter in beta equilibrium and uses holography, specifically the V-QCD and D3-D7 models, to derive results for electrical and thermal conductivities, as well as shear and bulk viscosities. Comparisons show deviations from perturbative QCD predictions, which are analyzed in detail.
Article
Astronomy & Astrophysics
Rose F. P. Waugh, Moira M. Jardine
Summary: This study focuses on the magnetic confinement of dense plasma in rapidly rotating solar-like stars. By creating a model, the researchers are able to generate cooled magnetic loops that are in equilibrium with the coronal magnetic field. They calculate the masses of these loops and find that magnetic confinement of material is common in rapidly rotating stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Michal Marczenko, Krzysztof Redlich, Chihiro Sasaki
Summary: This study analyzes the effects of chiral symmetry restoration in hadronic matter and its impact on the equation of state. The study finds that partial restoration of chiral symmetry can soften the equation below the saturation density and accommodate astrophysical constraints. However, above the saturation density, there is subsequent stiffening. Additionally, variations in the repulsive interactions of participle baryons in hadronic matter can result in different matter compositions in neutron star cores.
Article
Physics, Particles & Fields
Shubhalaxmi Rath, Binoy Krishna Patra
Summary: This study investigates the influence of strong magnetic fields on the viscous properties of hot QCD matter by calculating shear and bulk viscosities. It is found that both viscosities increase in the presence of a strong magnetic field, further enhanced by the addition of chemical potential. Additionally, the study observes changes in viscosity with temperature, where shear viscosity increases but bulk viscosity decreases, contrasting their behaviors in the absence of a magnetic field.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Chihiro Sasaki
Summary: We construct the spectral functions for light vector mesons at finite density and temperature in the presence of a novel mixing induced by baryon density, and find significant signatures of chiral symmetry restoration.
Article
Physics, Multidisciplinary
S. M. A. Tabatabaee Mehr, F. Taghinavaz
Summary: In this study, we investigate the chiral symmetry restoration/breaking of dense, magnetized, and rotating quark matter within the Nambu Jona-Lasinio model. We consider Nf = 2 flavors and Nc = 3 colors. We find a correlation between the magnetic and rotation fields, leading to the inability of strongly magnetized plasma to rotate. We solve the gap equation at both zero and finite temperature, and sketch the phase diagrams Tc(μB) and Tc(RΩ) for different cases.
Review
Physics, Multidisciplinary
Kai Hebeler
Summary: Recent advances in nuclear structure theory through ab initio many-body calculations have expanded the accessible part of the nuclear landscape, allowing for new microscopic studies. While different many-body methods show remarkable agreement, comparison with experiment and understanding theoretical uncertainties remain important. Efforts are being made to improve nuclear interactions and operators, including the systematic derivation of contributions using chiral effective field theory. Ongoing work focuses on improving the treatment of 3N interactions in ab initio frameworks to further advance our understanding of atomic nuclei.
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS
(2021)
Article
Physics, Nuclear
Jesper Leong, Theo F. Motta, Anthony W. Thomas, P. A. M. Guichon
Summary: The equation of state generated by the quark-meson coupling model incorporates the possibility of new short distance physics within neutron star cores. The contribution of this new physics to the energy density is proportional to the overlap between the quark cores of the baryons involved. By maintaining the properties of symmetric nuclear matter at saturation density and including an incompressibility compatible with data on giant monopole resonances, neutron stars with a maximum mass M-max > 2.1M(?) can be sustained even with the inclusion of hyperons.
Article
Astronomy & Astrophysics
Jose C. Jimenez, Eduardo S. Fraga
Summary: This study investigates compact stars composed of cold quark matter and fermionic dark matter, treated as two mixed fluids. The stellar structures and fundamental radial oscillation frequencies are calculated for different masses of the dark fermion under weak and strong self-interacting dark matter scenarios. It is found that the fundamental frequency can be significantly modified, leading to the formation of stable dark strange planets and dark strangelets with very low masses and radii.
Article
Astronomy & Astrophysics
Han Rui Fu, Jia Jie Li, Armen Sedrakian, Fridolin Weber
Summary: A set of hyperonic equations of state (EoS) are constructed by assuming SU(3) symmetry and using a covariant density functional theory approach. The EoS is constrained by terrestrial experiments at low density and modeled by varying the nuclear matter skewness coefficient and symmetry energy slope at high density. The results show that the model can support a range of static and rotating stellar masses under certain conditions.
Article
Astronomy & Astrophysics
Jia Jie Li, Armen Sedrakian, Mark Alford
Summary: In this work, we investigate the properties of compact stars with a first-order phase transition, where quark matter has low- and high-density phases. Unlike the usual case of a single phase transition, our hybrid star models involve sequential phase transitions from hadronic matter to low-density quark matter, and then to high-density quark matter phases. We explore the parameter space of these hybrid stars, considering constraints from neutron star mass, radius measurements, neutron skin thickness observations, and tidal deformability constraints from a gravitational-wave event.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Osvaldo Ferreira, Eduardo S. Fraga
Summary: This study discusses strange stars mixed with fermionic dark matter in the presence of a strong magnetic field. The two-fluid Tolman-Oppenheimer-Volkov equations are used. The effects of dark matter and a strong magnetic field on the masses, radii, and tidal deformability of the stars are examined, with significant variations observed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Review
Multidisciplinary Sciences
Arus Harutyunyan, Armen Sedrakian
Summary: In this work, the first- and second-order relativistic hydrodynamics of dissipative fluids are derived phenomenologically. A review of ideal relativistic hydrodynamics is provided, followed by a discussion of matching conditions, symmetries, decomposition of dissipative processes, and the definition of fluid velocity. The first-order hydrodynamics is formulated by considering the entropy flow equation, while the second-order hydrodynamics includes diffusion terms between different flavors. The relaxation-type equations are found to ensure causality and stability of the fluid dynamics.
Article
Veterinary Sciences
Javier Espinosa, Maria Ortega, Marti Pumarola, Eduardo Fraga, Laura Martin
Summary: This case report describes the clinical presentation and atypical MRI findings of a nine-year-old cross-breed dog with histologically confirmed multiple MPNSTs. The dog initially presented with ambulatory tetraparesis and was diagnosed with MUO based on MRI findings and CSF analysis. The dog responded well to treatment but deteriorated after seven months, with a follow-up MRI revealing new lesions affecting different spinal nerve roots. Histopathological examination confirmed multiple MPNSTs in the cervicothoracic spinal cord, a rare finding in dogs according to the literature.
VETERINARY SCIENCES
(2023)
Article
Astronomy & Astrophysics
Ana Luisa Foguel, Eduardo S. Fraga
Summary: We investigate the impact of a presumed axion-like-particle (ALP) emission on neutrino luminosities and mean energies in a core-collapse supernova explosion using a simple analytic description. We calculate the nuclear Bremsstrahlung and Primakoff axion luminosities and discuss how the ALP luminosities compete with neutrino emission, affecting the total thermal energy dissipation of the protoneutron star (PNS). Our results are publicly available in the python package ARTISANS for computing neutrino and axion observables under different parameter choices.
ASTROPARTICLE PHYSICS
(2023)
Review
Physics, Nuclear
Armen Sedrakian, Jia Jie Li, Fridolin Weber
Summary: This article reviews the physics of hyperons and -resonances in dense matter in compact stars. The approach to the equation of state and composition of dense nuclear matter in different regimes is presented. The static properties of compact stars with hyperons and -resonances are discussed in light of recent constraints from astrophysics observations. The effects of kaon condensation, strong magnetic fields, and rotation on the composition and properties of hypernuclear stars are also examined.
PROGRESS IN PARTICLE AND NUCLEAR PHYSICS
(2023)
Review
Astronomy & Astrophysics
Armen Sedrakian
Summary: This review article discusses recent developments in the field of dense QCD physics with a focus on the impact of multiple phase transitions on astrophysical manifestations of compact stars. The authors explore the structure of the phase diagram of dense QCD and the possible arrangement of various phases. They propose that pair-correlated quark matter in beta-equilibrium shares similarities with spin-imbalanced cold atoms and isospin asymmetrical nucleonic matter. The article also discusses the non-trivial implications of the beyond-mean-field structure of the quark propagator in two- and three-flavor quark matter. The authors construct an equation of state (EoS) that includes a conformal fluid and examine its effect on the mass-radius diagram of compact hybrid stars. Furthermore, they review the impact of a transition from gapped to gapless two-flavor phase on the thermal evolution of hybrid stars.
Article
Physics, Nuclear
Jia Jie Li, Armen Sedrakian, Fridolin Weber
Summary: In this study, a set of hadronic equations of state derived from covariant density functional theory were used to explore the universal relations among global properties of compact stars at high densities. The validity of the I-Love-Q and I-C-Q relations for nonrotating and rotating stars were confirmed, and these relations were extended to maximally rotating sequences. The relations between integral parameters of maximally rotating and static compact stars were also investigated. The results showed that these universalities persist even when hyperons and A-resonances are included, although the radial profiles of certain properties exhibit bumps in the presence of heavy baryons.
Article
Astronomy & Astrophysics
Peter B. Rau, Armen Sedrakian
Summary: We study the stability of compact stars using hybrid equations of state, with nuclear outer regions and two nested quark phases separated by strong first-order phase transitions. We find that faster transition timescales satisfy the traditional stability criterion, while slower conversion rates lead to stable stellar multiplets beyond triplets. Alternative junction conditions are examined, revealing similarities in stability properties to slow conversion rates. The properties of the reaction mode are also investigated for stars with rapid phase transitions or alternating rapid and slow phase transitions.
Article
Astronomy & Astrophysics
Jia Jie Li, Armen Sedrakian, Mark Alford
Summary: In this study, we investigate the impact of phase transitions in dense QCD on compact stars and their implications for gravitational wave and x-ray astrophysics observations. Our modeling assumes a strong first-order phase transition after the hadronic branch of compact stars reaches the two-solar mass limit. Our analysis suggests the existence of ultracompact stars with very small radii (6-9 km), which are consistent with the current multimessenger data.
Article
Astronomy & Astrophysics
Eduardo S. Fraga, Rodrigo da Mata, Savvas Pitsinigkos, Andreas Schmitt
Summary: We present a model for dense matter that incorporates strangeness and exhibits a chiral phase transition. The model parameters can be tuned to obtain a high-density phase resembling deconfined quark matter. Additionally, the model can be used to study dense matter under compact star conditions and investigate spatially inhomogeneous phases.
Article
Astronomy & Astrophysics
Mark Alford, Arus Harutyunyan, Armen Sedrakian
Summary: In this study, we investigate the bulk viscosity of hot and dense npe mu matter, focusing on the neutrino-transparent and neutrino-trapped regimes. Using a relativistic density functional approach, we model the nuclear matter with density-dependent parametrization DDME2. Our results show that the bulk viscosity reaches its maximum value at lower temperatures in the neutrino-transparent regime and then decreases rapidly at higher temperatures with neutrino-trapping. As an astrophysical application, we estimate the damping timescales of density oscillations in neutron star mergers and find that the bulk viscosity can significantly affect the post-merger object's evolution at certain temperatures.
Article
Physics, Nuclear
Armen Sedrakian, Arus Harutyunyan
Summary: This study investigates the equation of state and composition of dense and hot Delta-resonance admixed hypernuclear matter, and discusses its applications in neutron star binary merger remnants and supernovas.
EUROPEAN PHYSICAL JOURNAL A
(2022)
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Octavio C. Junqueira
Summary: This study investigates the influence of rotation on the transition temperature of strongly interacting matter produced in non-central heavy ion collisions. By using a holographic description of an AdS black hole, the authors extend the analysis to the more realistic case where the matter spreads over a region around the rotational axis. The results show the coexistence of confined and deconfined phases and are consistent with the concept of local temperature in rotating frames developed by Tolman and Ehrenfest.
Article
Astronomy & Astrophysics
Bing Sun, Jiachen An, Zhoujian Cao
Summary: This paper investigates the effect of gravitational constant variation on the propagation of gravitational waves. By employing two analytical methods, the study finds that variations in the gravitational constant result in amplitude and phase corrections for gravitational waves, and the time variation of the gravitational constant can be constrained through the propagation of gravitational waves.
Article
Astronomy & Astrophysics
Abdellah Touati, Zaim Slimane
Summary: This letter presents the first study of Hawking radiation as a tunneling process within the framework of non-commutative gauge theory of gravity. The non-commutative Schwarzschild black hole is reconstructed using the Seiberg-Witten map and the star product. The emission spectrum of outgoing massless particles is computed using the quantum tunneling mechanism. The results reveal pure thermal radiation in the low-frequency scenario, but a deviation from pure thermal radiation in the high-frequency scenario due to energy conservation. It is also found that noncommutativity enhances the correlations between successively emitted particles.
Article
Astronomy & Astrophysics
Shahar Hod
Summary: The travel times of light signals between two antipodal points on a compact star's surface are calculated for two different trajectories. It is shown that, for highly dense stars, the longer trajectory along the surface may have a shorter travel time as measured by asymptotic observers. A critical value of the dimensionless density-area parameter is determined for constant density stars to distinguish cases where crossing through the star's center or following a semi-circular trajectory on the surface has a shorter travel time as measured by asymptotic observers.
