Programme

The final program is reported below (CET time). Invited speakers are marked in bold.

	SESSION 1 - February 24th (Morning; Chair: L. Tolos)
09.20-09.30	Welcome
09.30-10.00	CompOSE (S. Typel) A brief introduction into CompOSE will be given with the focus on the main features of the website, data format and program. Problems will be discussed and possible future modifications and extensions will be proposed.
10.00-10.30	Non-ideal effects in magnetised BNS merger simulations (I. Hawke) The observable signatures of neutron star mergers are expected to depend strongly on the post-merger magnetic field: its strength, configuration, and evolution. Numerical simulations have made significant advances in modelling these fields, but huge uncertainties remain. Here we discuss modelling techniques and problems when moving away from ideal magnetised fluids, showing some modelling techniques that make numerical simulations practical, and results highlighting the sensitivity of the outcome to the small non-ideal contributions.
10.30-10:50	Ab initio superfluid properties for neutron star modelling (A. Rios) Superfluidity is a key nuclear physics property that impacts the statics and dynamics of neutron stars. I will first discuss why pairing properties are relevant for neutron star modelling, and should thus be listed in public repositories like COMPOSE. I will then argue that key ingredients, like the pairing gaps themselves, suffer from relatively large uncertainties associated to many-body scheme and nuclear Hamiltonian dependences. Finally, I will discuss our recent efforts to create a first-principles description of superfluidity in dense matter that incorporates meaningful systematic uncertainties.
10.50-11.30	Break
11.30-13.00	Discussion: what we need (D. Blaschke, L. Rezzolla, F. Burgio, S. Bernuzzi)
13.00-14.30	Lunch break

	SESSION 2 - February 24th (Afternoon; Chair: D. Antonopoulou)
14.30-15.00	Binary neutron star merger simulations (A. Bauswein) We will describe simulations of neutron star mergers. We focus on the impact of the equation of state of high-density matter on the dynamics and observables of neutron star mergers. The talk will also address the some more technical aspects of the equation of state.
15.00-15.30	Understanding GWs from core-collapse supernovae (P. Cerda) Core collapse supernovae is among the most exciting events that we expect to observe in the future by gravitational wave interferometers. They provide a unique multi messenger opportunity with the combined emission of gravitational waves, neutrinos and electromagnetic waves. In this talk I will focus in the current understanding of core-collapse GW signals and how they can be modelled in terms of normal oscillations modes of proto-neutron stars excited during the post-bounce phase before the onset of the SN explosion. The observation of such modes in the future by gravitational wave observatories (Virgo, LIGO) may allow to infer the properties of proto-neutron stars and constrain the the equation of state of hot nuclear matter.
15.30-16.00	Spritz: General Relativistic Magnetohydrodynamics with Neutrinos and a New Con2Prim Scheme (F. Cipolletta, J. V. Kalinani) General relativistic magnetohydrodynamic (GRMHD) simulations are an indispensable tool to obtain a detailed physical understanding of binary neutron star (BNS) and neutron star (NS)- black hole (BH) mergers. In the first part of the talk, we will present our newly developed GRMHD code Spritz, aimed at the study of compact binary mergers with finite-temperature equations of state (EOSs) and neutrino physics that is already available for public download. In particular, we will summarize the main features of our code, namely, staggered vector potential evolution, support for either analytical or fully tabulated EOSs, and implementation of a neutrino leakage scheme. We will also briefly discuss the results of various three-dimensional (3D) TOV tests that involve the evolution of electron fraction, temperature, and magnetic field, as well as neutrino transport, and we will give an insight on some preliminary results of BNS simulations with tabulated EOS, done with the support from the NASA TCAN 80NSSC18K1488 grant, with the future aim of including neutrino physics. The second part of the talk will rather focus on the discussion of a completely new conservative-to-primitive (Con2Prim) variable recovery scheme designed for ideal MHD. Having undergone both stand-alone tests and demanding 3D GRMHD tests, this scheme has demonstrated robustness, accuracy, and efficiency over the whole relevant parameter space, including the critical case of very strong magnetizations. We will also talk about technical aspects of implementing the scheme in Spritz, such as the requirements for the EOS framework.
16.00-16.30	Break
16.30-18.00	Discussion: what we need (N. Stergioulas, D. Radice, E. Most)

	SESSION 3 - February 25th (Morning; Chair: C. Ishizuka)
09.30-10.00	The EOS of dense matter from effective field theory interactions (K. Hebeler) In my presentation I will discuss the most recent results for the EOS from ab initio calculations based on chiral effective field theory interactions.
10.00-10.30	The equation of state for (hot) neutron stars (A. Raduta) Cold catalyzed neutron stars are well described by a one-parameter EoS that relates pressure to energy density. At variance with this astrophysical phenomena like core-collapse supernovae, formation of proto-neutron stars and black holes, binary neutron star mergers require as an input three dimensional EoS. The number of presently available general purpose EoS is limited. In my talk I shall review the general purpose EoS on Compose; comment on limitations met when collecting data along arbitrary paths; identify regions of the parameter space where new EoS are needed; suggest extra quantities to be stored.
10.30-11:00	Neutron-star crusts at finite temperature in a multi-component approach (A. Fantina) The interior of a neutron star is usually assumed to be made of cold catalysed matter. However, the crust is unlikely to remain in full thermodynamic equilibrium during the neutron-star formation and cooling, especially after crystallization occurs. In this contribution, we present a study of the evolution of the nuclear distributions of the hot dense multicomponent Coulomb plasma and the equilibrium composition of non-accreting neutron-star crusts down to crystallization. The variation of the impurity parameter, generally taken as free parameter in cooling simulations and calculated in this work self-consistently using microscopic nuclear models, will be discussed. Specifically, its non-monotonic behaviour, with values changing by several orders of magnitude reaching about 50, suggests that the crust may be composed of an alternation of pure (highly conductive) and impure (highly resistive) layers, which in turn may have sizeable impact on transport properties and the neutron-star evolution.
11.00-11.30	Break
11.30-13.00	Discussion: what we have (J. Margueron, I. Vidana, N. Chamel)
13:00-14.30	Lunch break

	SESSION 4 - February 25th (Afternoon; Chair: C. Providencia)
14.30-15.00	Meta-modelling the nucleonic EoSNone (F. Gulminelli) IThe recent progress of multi-messenger astronomy on different astrophysical sources of dense matter, leading to quantitative measurements of various properties of neutron stars such as the correlation between mass and radius and the tidal polarizability, are expected to unveil in the next future exciting open questions such as the structure and degrees of freedom of baryonic matter in extreme density conditions, and in particular the presence of phase transitions and the existence of deconfined matter in the core of neutron stars. This direct connection between astrophysical measurements and the microphysics of dense matter is due to the well-known fact that, under the hypothesis of validity of general relativity, there is a one-to-one correspondence between any static observable and the matter equation of state. However, the task is complicated by the fact that there is no ab-initio calculation of ultra-dense matter neither in the nucleonic nor in the hadronic or partonic sectors, and effective models are used. Therefore, the information on the matter composition is blurred by the uncertainty on the energy functional, and similar equations of state can be obtained under different hypotheses on the underlying microphysics. To advance on this issue, meta-modelling techniques allow exploring the complete parameter space of hadronic equations of state, and predicting the astrophysical observables with uncertainties controlled by our present theoretical and experimental knowledge of nuclear physics. This approach can therefore also be used as a null hypothesis to search for exotic degrees of freedom and suggest new observables. In this talk, the meta-modelling technique will be presented as well as several applications to the calculation of astrophysical observables.
15.00-15.30	Density Functional Theory of Compact Stars (A. Sedrakian) Results of the recent studies of hypernuclear stars will be present with the emphasis on the equation of state and its implications on the structure of compact stars.
15.30-15.50	The nEoS sets from hadron physics alone (F. J. Llanes Estrada) Testing Einstein's GR theory in full and not only in vacuum, as well as constraining its extensions, requires the density matter that only neutron stars can provide. To describe that matter one needs equations of state that are uncontaminated by astrophysical observables, since they are computed within General Relativity leading to circular or contradictory reasoning.We have matched Chiral Perturbation Theory computations at low-density to pQCD at high density employing only first principles, causality and monotony of P(E), at intermediate densities, to yield bands of EoS that are reasonably free of model bias. We have provided thousands of such interpolating EoS at zero temperature to sample the phase space of possible EoS allowed by microscopic physics alone, at the Complutense websitehttp://teorica.fis.ucm.es/nEoS/ Current work focuses on finite-temperature extensions and constraints on the latent heat of possible phase transitions. We also wish to learn about the Compose framework at the workshop to see whether it is simple and flexible enough for our project, currently in plain text column data, to be adapted therein. (In collaboration with Eva Lope Oter)
15.50-16.30	Break
16.30-18.00	Discussion: what we have (A. Harutyunyan, P. Shternin, V. Dexheimer)

	SESSION 5 - February 26th (Morning; Chair: P. Weltvrede)
09.30-10.00	Weak interactions in compact binary mergers (A. Perego) Weak processes are very relevant during the merger of two compact objects comprising at least one neutron star. In particular, they set the relative amount of neutrons to protons everywhere in the remnant and in the ejecta, and provide a very efficient source of cooling, from the merger up to the late postmerger phase. In this talk, I will review the status of neutrino modelling in numerical simulations of compact binary merger, with a special emphasis on the relation with the nuclear equation of state. The most relevant open issues in neutrino modelling will be also discussed.
10.00-10.20	Recent progress of neutrino transfer and equation of state (K. Sumiyoshi) I would like to talk on recent progress and issues of neutrino transport and equation of state for supernovae and neutron stars. The direct solver of the Boltzmann equation in 6D is now applied to numerical simulations of core-collapse supernovae and neutron star merger. As the methods numerical simulations are getting elaborated, the microphysics such as the equation of state and neutrino reaction rates becomes more crucial. I would like to present some of our recent results of the full neutrino transport simulations and the developments of the equation of state based on the many body approaches with associated revisions. I would like to discuss the necessity of matter properties and reaction rates in a coordinated manner, which is the theme of the workshop.
10.20-10.50	Microphysical input for neutron star dynamics (B. Haskell) In this talk I will discuss the different kinds of microphysical inputs that are needed for a number of neutron star related problems. In particular I will focus on modelling pulsar glitches and continuous gravitational waves from isolated neutron stars. I will show how dissipation coefficients, in particular, play a key role in these problems.
10.50-11.30	Break
11.30-13.00	Discussion: what we need to do (T. Fisher, J. L. Zdunik, J. Novak)
13.00-14.30	Lunch break

	SESSION 6 - February 26th (Afternoon; M. Oertel)
14.30-14:50	Bulk Viscous Damping of Density Oscillations in Neutron Star Mergers (A. Harutyunyan) We discuss the damping of density oscillations in dense nuclear matter in the temperature range relevant to neutron star mergers. This damping is due to bulk viscosity arising from the weak interaction “Urca” processes of neutron decay and electron capture. The nuclear matter is modelled in the relativistic density functional approach. The bulk viscosity reaches a resonant maximum close to the neutrino trapping temperature, then drops rapidly as temperature rises into the range where neutrinos are trapped in neutron stars. We investigate the bulk viscous dissipation timescales in a post-merger object and identify regimes where these timescales are as short as the characteristic timescale ∼ 10 ms, and, therefore, might affect the evolution of the post-merger object. Our analysis indicates that bulk viscous damping would be important at not too high temperatures of the order of a few MeV and densities up to a few times saturation density.
14.50-15:10	EOS from the user perspective (W. Kastaun) In this talk I will review problems encountered during the use of publicly available EOS tables in numerical relativity simulations as well as gravitational wave data analysis of BNS merger events. I will also discuss ongoing efforts of building an interface for using EOS that is consistent across use cases. I will present a new library called RePrimAnd, which contains an EOS framework for numerical relativity applications that is modular and extensible and not tied to a particular evolution code.
15.10-15:30	Implementing a tabulated EOS and neutrino leakage scheme in HARM3D (A. M. Berthier) On August 17, 2017, the LIGO/VIRGO collaboration detected the first gravitational wave signal coming from the merger of two neutron stars. This groundbreaking discovery, referred to as GW170817, revealed exciting new insights about how heavy elements, such as gold and platinum, are synthesized through a mechanism known as rapid neutron capture (r-process). In order to fully understand these signals, we need to couple observational surveys with numerical simulations of accretion disks surrounding black holes. Simulating the accretion disk and predicting the composition of the outflows is a task that requires efficient computing codes that include general relativity magnetohydrodynamics (GRMHD), neutrino physics and a model for matter at high densities. In this talk I will present the implementation of a tabulated equation of state that takes care of matter at high densities and a neutrino leakage scheme that considers the impact of neutrinos into HARM3D, a GRMHD parallelized code. I'll present tests for both the tabulated equation of state and the leakage scheme, as well as apply the tools to a magnetized torus.
15.30-15.50	Heat capacity of neutron star's crust in the presence of a vortex (D. Pecak) Bardeen-Cooper-Schrieffer theory explains how the heat capacity of the superfluid vanishes when the temperature approaches zero. Various mechanisms may suppress the pairing gap in the superfluid, leading to an increased heat capacity. In turn, this may translate to changing the cooling rate and the thermal evolution of neutron stars. The presence of a vortex in a superfluid neutron matter will add extra degrees of freedom in which the energy is stored, hence contributing to the heat capacity. From fully microscopic simulations, employing Superfluid Local Density Approximation (SLDA), it is possible to calculate the finite-temperature energy of the system. We use BSk type energy density functional, a very accurate nuclear functional designed to agree with existing astrophysical constraints. Using this state-of-the-art functional, we estimate the change in the heat capacity that results from the mere existence of a vortex in the system.
15.50-16.30	Break
16.30-18.00	Discussion: what we need to do (N. Andersson, S. Rosswog, M.-A. Aloy)
18.00-18.20	Farewell