In most core-collapse supernova (SN) simulations, the equation of state (EoS) has been usually modelled within the single-nucleus approximation. In this approach, the ensemble of nuclei expected to be present in the medium is replaced by one (average) nucleus. Although this approximation is adequate to predict thermodynamic properties of the medium in the temperature-density range of interest,...
The breaking of translational symmetry leads to the depletion of the neutron superfluid reservoir in the inner crust of a neutron star, similarly to superfluid helium in porous media or cold atomic gases in optical lattices. During this talk, calculations of the neutron superfluid fraction will be reviewed, and some astrophysical implications will be briefly discussed.
At densities below the nuclear saturation density and not too high temperatures (T<20 MeV), core-collapse supernova matter is unstable with respect to density fluctuations such that inhomogeneous structures develop and clusters can appear. Light (deuterons, tritons, helions, α-particles), and heavy (pasta phases) nuclei can be expected. Their appearance can modify the neutrino transport, which...
We apply the novel equation of state, which includes the surface tension contribution induced by the interparticle interaction and the asymmetry between neutrons and protons, to the study of neutron star properties. This high-quality equation of state is obtained from the virial expansion for the multicomponent particle mixtures that takes into account the hard-core repulsion between them. The...
The modelling of neutron stars requires the determination of the point of the transition between the core and the crust of the star. In this work, the core-crust transition is studied with finite-range nuclear interactions using the dynamical method for detecting the instability of the matter in the core against density perturbations. We analyze the correlation of the transition properties...
With the detection of GW170817 we have observed the first multi messenger signal
from two merging neutron stars. This signal carried a multitude of information
about the underlying equation of state of nuclear matter.
I will demonstrate how this observation can be used
to constrain macroscopic properties of neutron stars, in particular the radius and the maximum mass and hence to set limits...
The observation of NS allows us to constrain the equation of state(Eos) of the dense matter well beyond the densities available in earth laboratories. For example, observations of the NS mass-radius relation and the mass–moment-of-inertia relation can be used to infer the NS Eos within a certain uncertainty. However, the mass of several NS are known with good precision but their radii still...
We study in detail the deconfinement phase transition that takes place in hot/dense nuclear matter in the context of neutron stars and neutron star mergers. For this purpose, the Chiral Mean Field (CMF) model, an effective relativistic model that includes self-consistent chiral symmetry restoration and deconfinement to quark matter, is employed.
CompOSE (CompStar Online Supernovae Equations of State) is a repository of equation-of-state (EoS) tables for use in astrophysical simulations like core-collapse supernovae or neutron-star mergers. They contain information on thermodynamic properties of compact-star matter, its chemical composition and on microscopic quantities. The data are stored in a simple but flexible format. In addition,...
Because a neutron star's magnetic field is likely to evolve
very slowly, present-day magnetic fields will bear imprints of the
star's early life. In particular, for stronger magnetic fields the star
will achieve hydromagnetic equilibrium whilst still in the proto-neutron
star phase, meaning that finite-temperature effects should be accounted
for. Slightly later, the crust (and pasta...
Based on recent experimental and theoretical hints on possible formation of a resonant four-neutron system we study effects of appearance of such a cluster in neutron rich baryon matter inside NSs. For this purpose we employ a relativistic mean field approach which includes nucleons, $\Delta$-baryons as well as light nuclear clusters. Our analysis demonstrates that tetraneutrons existing as...
The macroscopic properties of neutron stars depend on how sub-atomic particles interact in their interiors. These interactions, encoded in the equation of state, are specially uncertain in the central regions, where densities exceed that of an atomic nucleus. The maximum mass of a neutron star can discriminate between proposed equations of state. New millisecond pulsars in compact binaries...
The role of superfluidity for the transport processes in Neutron Stars
is briefly discussed. The emphasis will be on the different elementary
excitations that can occur in the superfluid matter. A throughout microscopic
study of the excitations in different physical conditions inside Neutron Stars
is presented and discussed. The results include the overall strength functions
of the electron,...
Issues involving nuclear superfluidity are thought to play key roles for neutron star phenomenology. Pulsar glitches (sudden jumps in the period of otherwise steadily spinning down pulsars) offer a glimpse into the superfluid interior of a neutron star: within the currently accepted scenario these timing irregularities are explained in terms of an expulsion of the quantized vortex lines that...
In the interior of a mature neutron star, the differential rotation of the neutron superfluid star with respect to the normal component allows to store angular momentum, which is released during a pulsar glitch. Recent preliminary studies show how it is in principle possible to estimate pulsar masses from observations related to their timing properties. In this talk we will present a...
We have computed stationary and axisymmetric configurations of uniformly rotating superfluid neutron stars in a fully general relativistic framework with realistic equations of state. At low rotation rates, the neutron superfluid and the rest of the star are not only coupled by entrainment, but general relativity leads to an additional coupling through frame-dragging effects, which is likely...
I will give a review of transport properties of matter inside neutron stars and point out their significance for astrophysical observables. This will include various phases of the star, from the outer layers to the densest possible phases, such as deconfined quark matter. I will try to focus on general methods and principles, but also touch on specific open questions for future research.
Bulk viscosity of neutron star cores is responsible for a number of interesting phenomena, e.g., r-mode stabilization [1] and magnetic inclination-angle evolution [2]. It originated because of non-equilibrium particle mutual transformations in dense stellar plasma, and strongly depends on the actual core composition. It is well-known that account for hyperons in the core dramatically increases...
We calculate the spectrum of inertial oscillation modes in a slowly rotating superfluid neutron star, including for the first time both effects of finite temperatures and entrainment between superfluid neutrons and protons. We work in Newtonian limit and assume minimal core composition (neutrons, protons and electrons). We also developed an approximate method that allows to calculate the...
The breaking of a neutron star crust is believed to play a fundamental role in some astrophysical phenomena like glitches, flares and the emission of gravitational waves from isolated compact objects. However, there is still lack of systematic (and quantitative) studies of the crustal deformation under different types of loads, which can be induced by rotation, pinning of superfluid vortices...
The recent discovery of neutron stars (NSs) with current gravitational-wave experiments gives us an unprecedented opportunity to probe the dynamical behaviour of compact stars. The viscous (and thermal) dissipation plays a fundamental role in the dynamical equations of motion of NSs. It has a damping influence on the oscillation modes and directly determines the minimum period of pulsars that...
Neutron stars are the biggest objects in the universe that are thought to contain superfluid matter. However, almost fifty years after the first observation of pulsar, detailed theory of dynamics of the stellar interior still remains open to debate.
The reason for that is a large discrepancy of length scales - quantum theory operates at distances of fm and have to provide input to relativistic...
Neutron Stars offer a unique opportunity to study the fundamental physics in extreme conditions. Physical properties of Neutron Stars are believed to be affected by the presence of superfluid matter inside that is connected with pulsar glitches. To study the latter the dynamics of quantized vorticity is used in the most models. However, the problem of establishing connection between the...
The neutrino mean free path in neutron matter under a strong magnetic field is evaluated for the inelastic scattering reaction and studied as a function of the neutron matter density in the range $0.05 \leq \rho \leq 0.4$ fm$^{-3}$ for several temperatures up to 30 MeV and magnetic field strengths B=0 G, $10^{18}$ G and $2.5\times 10^{18}$ G.
Polarized neutron matter is described within the...
In this talk I will discuss various aspects of pion condensation at finite
temperature and density. At T=0, the phase diagram will be mapped
out in the mu_I-mu_B plane, and we
will discuss the competition between an inhomogeneous chiral condensate and
a pion condensate. At finite T, we map out the phase diagram in the
mu_I-T plane focusing on the deconfinement and chiral transitions as well
as...
