Hirschegg 2009:

Nuclear Matter at High Density

International Workshop XXXVII on Gross Properties of Nuclei and Nuclear Excitations
Hirschegg, Kleinwalsertal, Austria, January 18-24, 2009


Neutrino interactions with nucleon matter in super
Achim Schwenk (TRIUMF)
Cooling of hybrid stars: towards a consistent pict
Blaschke, David (University of Wroclaw)
We present a set of observational constraints on the cooling behavior of compact stars and discuss possible consequences for structure and composition of their interiors. First, we discuss purely hadronic neutron stars and their cooling [1], focussing on three problems: the {\it direct Urca problem} [2], the {\it Vela mass problem} [3] and the {\it deep crustal heating problem} related to superbursts [4] and X-ray transient cooling [5]. Second, we discuss possible scenarios for hybrid stars with color superconducting quark matter interiors and their cooling behaviour. It is shown that in order to fulfill the cooling constraints, all quark species must be gapped, whereby the smallest diquark pairing gap shall not exceed about 1 MeV [6]. This condition is fulfilled, e.g., for diquark condensation in a single-flavor spin-1 pairing channel, denoted as the isotropic color-spin-locking (CSL) phase [7]. Finally, we discuss a possible realization of this phase in hybrid stars as a down-quark CSL phase in coexistence with asymmetric nuclear matter [8], fulfilling the above cooling constraints and offering a possible source for deep crustal heating as an alternative to previously discussed strange star cores in the color-flavor-locking phase [4]. [1] D. Blaschke, H. Grigorian and D.N. Voskresensky, A\&A 424, 979 (2004) [2] D. Blaschke and H. Grigorian, PPNP 59, 139 (2007) [3] S. Popov, H. Grigorian and D. Blaschke, PRC 74, 025803 (2006) [4] D. Page and A. Cumming, ApJ 635, L157 (2005) [5] P.S. Shternin, D.G. Yakovlev, P. Haensel and A.Y. Potekhin, arXiv:0708.0086 [astro-ph] [6] H. Grigorian, D. Blaschke and D. Voskresensky, PRC 71, 045801 (2005) [7] D.N. Aguilera, D. Blaschke, M. Buballa and V.L. Yudichev, PRD 72, 034008 (2005) [8] D. Blaschke, F. Sandin, T. Kl\"ahn and J. Berdermann, arXiv:0807.0414 [nucl-th]
The CBM experiment
Hoehne, Claudia for the CBM collaboration
The CBM experiment at FAIR prepares for exploring the QCD phase diagram at high net baryon densities. Physics objectives, detector R&D and detailed simulation studies will be presented in this contribution.
Neutrinos and gravitational waves from core-collap
Hans-Thomas Janka
Supernovae and neutron star mergers will be discussed as sources of gravitational waves with a focus on the question what these signals can tell us about the equation of state of hot neutron star matter.
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Pion condensation in quark matter
Abuki, Hiroaki (Frankfurt University)
I will discuss some aspects of pion condensation at finite baryon density within a Nambu-Jona Lasinio model.
Probing Properties of Neutron Stars with Heavy-Ion
Bao-An Li, Lie-Wen Chen, Che Ming Ko, Plamen Krast
Recent heavy-ion reaction experiments on isospin diffusion and the ratio of charged pions have allowed us to put a strong constraint on the density dependence of the nuclear symmetry energy[1]. Implications of the constrained EOS of neutron-rich matter on the mass-radius relation of fast pulsars, core-crust transition density of neutron stars and the gravitational radiation of elliptically deformed pulsars will be discussed [2,3,4]. References: 1)Recent Progress and New Challenges in Isospin Physics with Heavy-Ion Reactions, Bao-An Li, L.W. Chen and C.M. Ko, Physics Reports 464, 113 (2008). [2]Nuclear limits on gravitational waves from elliptically deformed pulsars, Plamen G. Krastev, Bao-An Li and Aaron Worley, Phys. Lett. B668, 1 (2008 (2008). [3]Nuclear constraints on the momenta of inertia of neutron stars, Aaron Worley, Plamen G. Krastev and Bao-An Li, Astrophysical Journal 685, 390 (2008). [4]Constraining properties of rapidly rotating neutron stars using data from heavy-ion collisions, Plamen G. Krastev, Bao-An Li, Aaron Worley, Astrophysical Journal 676, 1170 (2008).
Magneto-seismology and the nuclear physics of comp
Watts, A.L. (University of Amsterdam)
Seismic vibrations triggered by magnetic starquakes offer a new way of studying the composition and coupling of the neutron star crust and core. I will outline the key areas where seismic models draw on dense matter physics, and discuss how observations might constrain stellar composition. I will discuss the progress of deep searches for seismic oscillations using current telescopes (including the Fermi Space Telescope), and review the prospects for detecting gravitational waves from oscillations excited by magnetic events.
Scalar mesons and chiral symmetry restoration
F. Giacosa, A. Heinz, S. Struber, D.H. Rischke
The role of light scalar mesons is important both for vacuum phenomenology and for studies at nonzero temperature and density. After a short recall of the former, the attention is focused on the implication that different interpretation of scalar mesons can have at high density/temperature where chiral symmetry is restored. A model involving (pseudo)scalar and (axial)vector mesons, together with the nucleon and its chiral partner, is used to study the different scenarios.
Cooling neutron stars: Theory and observations
Yakovlev D.G., Kaminker A.D., Potekhin A.D. (Ioffe
We review current state of neutron star cooling theory and analyze those properties of superdense neutron star matter which can be determined (constrained) by comparing the theory with observations of neutron stars. First of all, they are neutrino emission properties, as well as composition and superfluidity of superdense matter. We formulate reliable constraints, which can be imposed at present, and discuss the perspectives.
Observations of isolated cooling neutron stars
Haberl, Frank (MPE)
X-ray observations unveiled new classes of isolated neutron stars for which it is presently unclear whether the different phenomenology we observe reflects different evolutionary stages and/or variations in intrinsic neutron star properties. Over the last years the outstanding capabilities of the X-ray observatories XMM-Newton and Chandra with respect to sensitivity and spectral resolution increased our knowledge in this field of neutron star research considerably. The analysis of thermal radiation from cooling isolated neutron stars has provided crucial insights on their surface temperature and magnetic field distributions. The results are essential to derive important information on the structure and chemical composition of the neutron star surface layers. Thermal emission with temperatures of about 0.3-1 Million K dominates the X-ray spectra of middle-aged pulsars. No non-thermal activity is seen from a group of nearby radio-quiet isolated neutron stars, which offers the unique opportunity to investigate their relatively undisturbed thermal emission in X-rays.
Recent measurements of millisecond pulsar masses
Paulo C. Freire (Arecibo Observatory/Cornell/WVU),
We present several recent (2008) measurements and statistical estimates of the masses of some radio millisecond pulsars. The most recent is PSR J1903+0327, a 2.15-ms pulsar discovered by Arecibo's ALFA pulsar survey. This is the first binary millisecond pulsar in the Galactic disk known to have an eccentric (e = 0.44) orbit. The unusual characteristics of this system allow the measurement of three post-Keplerian (PK) parameters. Assuming they are relativistic, we get for the pulsar a mass of 1.67 +/- 0.01 solar masses, the companion has a mass of 1.028 +/- 0.004 solar masses. This is the most precise mass ever determined for a millisecond pulsar. This value has immediate consequences for the study of dense matter in the cores of neutron stars, because it excludes with certainty several equations of state for dense matter. This value is further confirmed by the fact that the three PK parameters provide 1-sigma consistent estimates for the mass of the pulsar and the companion, confirming their relativistic origin. We also review recent statistical estimates of the masses of millisecond pulsars in globular clusters that suggest that the distribution of the masses of these objects could be much wider than observed for the neutron stars in double neutron star systems, presumably because of accretion of matter from the companion star after formation. In particular, PSR J1748-2021B is very likely to have a mass significantly in excess of 2 solar masses. Continued radio timing over the next few years, complemented by observations at other wavelengths, should be able to provide more precise estimates for the masses of these objects.
Phase Structure and Transport Properties of Dense
Thomas Schaefer
We provide a brief summary of our current knowledge of the phase structure of very dense quark matter, concentrating on the question how the ground state at asymptotically high density - CFL matter - evolves as the density is lowered. We then present some work on the transport properties of these phases.
Soft X-ray emission from isolated neutron stars
Vyacheslav Zavlin (NASA MSFC/USRA)
Investigation of emission from the surfaces of isolated neutron stars (NS) provides, with the aid of advanced theoretical models of thermal emission, a unique opportunity to infer the NS surface temperatures, magnetic fields, chemical composition and, ultimately, NS masses and radii. This information, supplemented with the model equations of state and NS cooling models, can lead to understanding the fundamental properties of the superdense matter in the NS interiors. As the surface temperatures of isolated NSs observable are predicted (and found) to be within a range from about a half to a few million degrees, soft X-rays (0.1-10 keV) are the key energy band for detecting and studying the NS thermal radiation. The first possibility for this investigation was opened about 30 years ago with the launch of the X-ray observatories Einstein and EXOSAT. A significant contribution to this study was provided by ROSAT in 1990's, whose instrumental sensitivity peaked in the soft X-ray band. The outstanding capabilities of the currently operating observatories, Chandra and XMM-Newton, have greatly increased the potential to observe and analyze thermal radiation from isolated NSs. In this presentation I will overview the most important aspects of the theoretical modeling of the NS thermal emission, as well as results from Chandra and XMM-Newton observations of isolated NSs of various types.
"Hydrodynamics of the superfluid CFL phase and r-m
C. Manuel (IEEC-CSIC), M. Mannarelli (IEEC-CSIC),
Dissipative processes acting in rotating neutron stars are essential in preventing the growth of the r-mode instability. We estimate the damping time of r-modes of an hypothetical compact quark star made up by color flavor locked quark matter at a temperature $T \lesssim 0.01$ MeV. We first review the hydrodynamical behavior of this superfluid system, and consider the main dissipative process that take place in its cold regime. The dissipation that we consider is due to the the mutual friction force between the normal and the superfluid component arising from the elastic scattering of phonons with quantized vortices. This process is the dominant one for temperatures $T \lesssim 0.01$ MeV where the mean free path of phonons due to their self-interactions is larger than the radius of the star and they can be described as an ideal bosonic gas. We find that r-modes oscillations are efficiently damped by this mechanism for pulsars rotating at frequencies of the order of $1$ Hz at most. Our analysis rules out the possibility that cold pulsars rotating at higher frequencies are entirely made up by color flavor locked quark matter.
Constraining the Density Dependence of the Symmetr
W. G. Lynch, NSCL and the Department of Physics an
The density dependence of the symmetry energy plays an important role in nuclear masses, fission barriers, collective excitations, and neutron skin thicknesses of neutron-rich nuclei. It also governs many properties of the neutron stars such as their radii, the thicknes of their inner crusts, phase transitions in the stellar interior, seismic activity, and cooling rates. Experiments are beginning to provide constraints on the denstiy dependence of the symmetry energy at sub-saturation densities. This talk will review the measurements and some of the constraints that have been obtained so far.
CFL cores in Hybrid Stars
G. Pagliara (Frankfurt U.), J. Schaffner-Bielich
We study the equation state of strongly interacting quark matter within a NJL-like model in which the chiral condensates and the color superconducting gaps are computed self-consistently as a function of the baryon density. We then use the equation of state to compute the structure of compact stars and we show that two phase transitions could take place in a star, a first transition from hadronic matter to 2SC quark matter and a second transition from 2SC quark matter to CFL quark matter. The astrophysical consequences of this scenario are discussed in connection with explosive phenomena, Supernovae and Gamma-Ray-Bursts, and with the r-modes instability.
A fermionic molecular dynamics technique to model
Vantournhout K. (UGent), Jachowicz N. (UGent), Ryc
At sub-nuclear densities of about $10^{14}$ g/cm$^3$, nuclear matter arranges itself in a variety of complex shapes. This can be the case in the crust of neutron stars and in core-collapse supernovae. These slablike and rodlike structures, designated as nuclear pasta, have been modelled with classical molecular dynamics techniques [1,2]. We present a technique, based on fermionic molecular dynamics [3], to model nuclear matter at sub-nuclear densities in a semi classical framework. The dynamical evolution of an antisymmetric ground state is described making the assumption of periodic boundary conditions. Adding the concepts of antisymmetry, spin and probability distributions to classical molecular dynamics, brings the dynamical description of nuclear matter to a quantum mechanical level. Applications of this model vary from investigation of macroscopic observables and the equation of state to the study of fundamental interactions on the microscopic structure of the matter. [1] G.~Watanabe et al., Phys.~Rev.~C {\bf 69}, 055805 (2004). [2] C.J.~Horowitz et al., Phys.~Rev.~C {\bf 72}, 035801 (2005). [3] F.~Feldmeier and J.~Schnack, Rev.~Mod.~Phys {\bf 72},655-688 (2000).
Neutron Stars as a Probe for Dense Matter
Dexheimer, V. A. (FIAS - Johann Wolfgang Goethe Un
We study different stages of the neutron star cooling by computing neutron star properties at various temperatures/entropies using effective chiral models including hadronic and quark degrees of freedom. We consider the effects of large lepton fractions and trapped neutrinos. Macroscopic properties of the star as mass, radius and moment of inertia are calculated and compared with observations. It can be seen that the effects of chiral restoration and deconfinement to quark matter in the core of the neutron star at different stages of the evolution can be significant for the evolution of the star and allow insight into the behaviour of matter at extreme densities.
Recent progress in Quantum Monte Carlo calculation
Alexey Yu. Illarionov (SISSA), Stefano Gandolfi (
We report on the most recent applications of the Auxiliary Field Diffusion Monte Carlo (AFDMC) method. The equation of state (EoS) for pure neutron matter in both normal and BCS phase and the superfluid gap in the low--density regime are computed, using a realistic Hamiltonian containing the Argonne AV8' plus Urbana IX three--nucleon interaction. Preliminary results for the EoS of isospin--asymmetric nuclear matter are also presented.
r-modes, gravitational waves and neutron star exot
Andersson, N (Southampton)
In this talk I will summarise our current understanding of the gravitational-wave driven r-mode instability. I will explain how the neutron star composition enters the problem, and describe progress towards understanding how the instability works in superfluid stars. I will also discuss recent results for hyperon and colour superconducting cores.
Gravitational waves from core collapse supernovae
Scheidegger, S. (Unibas), Käppeli, R. (Unibas), W
The gravitational wave signal of a core collapse supernova can provide direct observational access to electromagnetically hidden high density regions; it may probe and constrain the nuclear physics properties of the proto-neutron star. We present recent results of 3D simulations of core collapse supernovae performed using different equations of state. The gravitational wave signals from these models will be shown, concentrating on how the signal varies with the equation of state.
Dense Matter Equation of State With A Finite-Range
James M. Lattimer
Preliminary results are presented for an equation of state of hot, dense matter based upon a finite-range Thomas-Fermi method. This model is suitable for the generation of tables for astrophysical applications. It repairs several shortcomings of previous methods, including the liquid droplet approach of Lattimer & Swesty (1991) and the hybrid approach using a relativistic mean-field approach of Shen et al. (1998). It allows for adjustable incompressibility, skewness, nucleon effective masses, and symmetry energy density dependence. Applications to the neutron star crust and to proto-neutron stars are discussed.
Superfluid instabilities and neutron star glitches
Glampedakis, K. (Tuebingen), Andersson, N. (Southa
We discuss a new class of inertial-mode instabilities in superfluid neutron stars and its impact on the dynamics of free precession and glitches.
On the appearance of hyperons in neutron stars
H. Djapo, Institut f\"ur Kernphysik, TU Darmstadt
By employing a recently constructed hyperon-nucleon potential the equation of state of $\beta$-equilibrated and charge neutral nucleonic matter is calculated. The hyperon-nucleon potential is a low-momentum potential which is obtained within a renormalization group framework. Based on a Hartree-Fock approximation at zero temperature the densities at which hyperons appear in neutron stars are estimated. For several different bare hyperon-nucleon potentials and a wide range of nuclear matter parameters it is found that hyperons in neutron stars are always present. These findings have profound consequences for the mass and radius of neutron stars.
Neutron stars, supernovae and the QCD phase transi
Schaffner-Bielich, J, Sagert, I, Pagliara, G, Hemp
We present a nuclear equation of state suitable for core-collapse supernovae, proto neutron stars and neutron star mergers. Emphasis is put on the role of the QCD phase transition at high densities and moderate temperatures. We delinate the QCD phase transition line applicable for conditions in astrophysical scenarios. Comparison to the conditions encountered in heavy-ion collisions is made in particular in view of the upcoming CBM experiment of FAIR. Possible signals for the detection of the QCD phase transition by astrophysical means are outlined.
Cluster formation and the low-Density Nuclear Matt
G. Röpke (Compstar Collaboration), K. Sumiyoshi
We explore the abundance of light clusters in core-collapse supernovae at post-bounce stage in a quantum statistical approach. Adopting the profile of a supernova core from detailed numerical simulations, we study the distribution of light bound clusters up to alpha particles (2 $\leq A \leq$ 4) as well as heavy nuclei ($A > 4$)in dense matter at finite temperature. Within the frame of a cluster-mean field approach, the abundances of light clusters are evaluated accounting for self-energy, Pauli blocking and effects of continuum correlations. We find that deuterons and tritons, in addition to $^3$He and $^4$He, appear abundantly in a wide region from the surface of the proto-neutron star to the position of the shock wave. The appearance of light clusters may modify the neutrino emission in the cooling region and the neutrino absorption in the heating region, and,thereby, influence the supernova mechanism.
Nuclear matter with three-body forces
Soma, V. and Bozek, P. (Institute of Nuclear Physi
We present spectral calculations of nuclear matter properties, with three-body forces included in the in-medium T-matrix equations. The thermodynamic observables are computed for symmetric and pure neutron matter, and estimations for the density dependence of the symmetry energy are obtained. We also investigate the influence of three-body forces on the single-particle properties, discussing spectral functions, self-energies and effective masses.
BEC-BCS Crossover in quark matter
Zablocki, D (U Wroclaw), Anglani, R (U Bari & INFN
A quantum field theoretical approach to the thermodynamics of dense Fermi systems is developed for the description of the formation and dissolution of quantum condensates and bound states in dependence of temperature and density. As a model system, we study the chiral and superconducting phase transitions in twoflavor quark matter within the NJL model and their interrelation with the formation of quark–antiquark and diquark bound states. The phase diagram of quark matter is evaluated as a function of the diquark coupling strength and a coexistence region of chiral symmetry breaking, and color superconductivity is obtained at very strong coupling. The crossover between Bose–Einstein condensation (BEC) of diquark bound states and condensation of diquark resonances (Cooper pairs) in the continuum (BCS) is discussed as a Mott effect. This effect consists in the transition of bound states into the continuum of scattering states under the influence of compression and heating. We explain the physics of the Mott transition with special emphasis on the role of the Pauli principle for the case of the pion in quark matter.
Neutrino emission from superfluid neutron stars
Voskresensky D.N. (MEPhI, GSI), Kolomeitsev E.E. (
Neutrino emission processes from superfluid neutron stars are discussed. As example, the processes of the breaking and formation of neutron and proton pairs are considered within Larkin-Migdal-Leggett approach for superfluid Fermi systems.
Long-range force between non-Abelian strings in CS
Nakano, E (GSI), Nitta, M (Keio Univ), Matsuura, T
We discuss a long-range force between two non-Abelian vortex strings, which could be formed as the most stable vortex solution in color flavor locked phase of color superconductor. Within Ginzburg-Landau type effective theory, we found there is a universal repusive force.
Nuclear equation of state from reactions and struc
P. Danielewicz
Constraints on the nuclear equation of state of symmetric matter, from heavy-ion reactions, and on nuclear symmetry energy, from structure, are discussed. The reactions constraints stem from systematics of nuclear collective flow. The structure constraints stem from systematics of isobaric analog states and of nucleonic radii.
Bound states in nuclear matter
Sedrakian A. (Frankfurt University)
I will discuss the formation of bound states in dilute nuclear matter and its implications for the equation of state and composition of astrophysical plasma in supernova enevlopes. Bulk properties of dense nuclear and hypernuclear matter will be discussed in the framework of the Brueckner theory.
Density of the symmetry energy from heavy ion coll
H.H.Wolter (Univ. Munich), T. Gaitanos (Univ. Gies
The symmetry energy is investigated in heavy ion collisions at densities below saturation at Fermi energies, and at densities above saturation at relativistic energies. We have investigated various observables in both regimes with respect to their sensitivity to the symmetry energy. Among these are transport properties at low energies, and flow and $\pi$- and $K$-meson production at high energies. We will report on these investigations, and show, that a clear conclusion cannot be drawn, yet.
Influence of light nuclei on neutrino-driven super
Arcones, A. (GSI,TUD), Martinez-Pinedo,G (GSI), O'
We study the composition of the outer layers of a protoneutron star and show that light nuclei are present in substantial amounts.The composition is dominated by nucleons, deuterons, tritons and alpha particles; 3He is present in smaller amounts. This composition can be studied in laboratory experiments with new neutron-rich radioactive beams that can reproduce similar densities and temperatures. After including the corresponding neutrino interactions, we demonstrate that light nuclei have a small impact on the average energy of the emitted electron neutrinos, but are significant for the average energy of antineutrinos. During the early post-explosion phase, the average energy of electron antineutrinos is slightly increased, while at later times during the protoneutron star cooling it is reduced by about 1 MeV. The consequences of these changes for nucleosynthesis in neutrino-driven supernova outflows are discussed.
Magnetar seismology.
Samuelsson, L. & Andersson, N
The quasi-periodic oscillations observed in the tails of giant flares in soft gamma-ray repeaters may be interpreted as being a product of torsional motion in the crust of the flaring star. I will review the status of this interpretation and give an overview of the state of art modeling of such oscillations. In particular I will discuss which conclusions about the dense matter equation of state that may be drawn from knowledge of the frequencies and the properties of the crustal matter.
Neutron star structure determined by nuclear physi
Uwe Heinzmann UF, Joacim Maruhn UF, Igor Mishustin
Our research is related to the classical paper of Negele and Vautherin: Neutron star matter at sub-nuclear densities (Nuclear Physics A 207 (1973) 298-320). Negele and Vautherin calculated neutron star matter using density-dependentHartree-Fock (DDHF) equations without pairing. Their aim was the construction of a reliable theory of a nucleon many-body system derived from the two-body nucleonnucleon interaction. They obtained numerical results for nuclear configurations at various subnuclear densities. In the our research project we intend to obtain new insights into nuclear structure physics in connection with the structure of neutron stars by employing these models,predominantly by using Hartree-Fock Bogolyubov code with Skyrme forces. Special astrophysical conditions in a neutron star will be modeled by gases of free electrons and free neutrons. The nuclei subject to these conditions can be expected to possess quite different properties compared to isolated nuclei. The effects of this environment on the shell structure and on the bulk properties of these nuclei will be studied in detail. As for the choice of boundary conditions, we can compare our results with the results obtained by Baldo and Chamel. The modeling of electron and neutron gases will be systematically improved throughout this research work. The results thus obtained will then be processed in a calculation of the neutron star crust and yield new insights in local as well as global properties of these objects. From the astrophysical point of view, we are searching for a model for the inner crust of a neutron star modeling the transition between the neutron lattice in the Wigner-Seitz approach and the neutron Fermi liquidclear densities.
A universal charge-radius relation for spherical o
Madsen, Jes (Aarhus University)
Pair creation in supercritical electric fields limits the net charge of any static, spherical object from subatomic to astrophysical scales. The maximal charge of a sphere is proportional to radius for radii below 10^4 fm and to radius squared for larger radii. The physics behind the universal charge-radius relation will be described and possible consequences of relevance for the Workshop discussed.
Probing neutron-star matter using the cooling prop
Wijnands, R.
Neutron stars in X-ray binaries are heated due the accretion of matter. The X-ray transients among the X-ray binaries allow new probes into the properties of neutron-star matter because when the accretion has halted, the cooling neutron-star surface becomes directly visible. In recent years, detailed observations have become available and new theoretical studies have been performed, both providing new insights into the behavior of accreting neutron stars. I will review the most recent progress in this field, especially focusing on new understanding of the properties of the neutron star crust in accreting systems.
Soft equation of state from heavy ion data and imp
Sagert, I. , Schaffner-Bielich, J. (Institute for
Recent results from measurements of Kaon production at subthreshold energies in heavy ion collisions imply a soft nuclear equation of state for densities below 3 times saturated nuclear matter density with compressibilities K0 < 200 MeV. We apply these results to study the implications on compact star properties. As a probe for the nuclear matter compressibility, maximum masses of neutron stars are calculated using a phenomenological equation of state as well as Skyrme-Hartree-Fock and Relativistic mean field approaches. We test low mass neutron star measurements as a probe for the symmetry energy of nuclear matter and finally explore the consequences of a soft nuclear equation of state for the highest possible mass of compact stars following the approach of Rhoades and Ruffini (PRL, 32, 324-327 (1974)).
To be determined
M. Prakash
To be determined
From Nuclei to Nuclear Matter - A Statistical Mode
Hempel, M. (Goethe-University Frankfurt); Schaffne
The equation of state and the composition of hot hadronic matter is described by an ensemble of nuclei and interacting nucleons in nuclear statistical equilibrium. The nucleons are described with a relativistic mean field model and the masses of the nuclei are taken from nuclear structure calculations which are based on the same nuclear Lagrangian. For known nuclei experimental data is used directly. Excluded volume effects are implemented in a thermodynamic consistent way to be able to describe the transition to uniform nuclear matter. The resulting equation of state is presented and a good agreement with other commonly used models based on the single nucleus approximation is found. Regarding the composition the importance of a statistical treatment is illustrated and the role of the shell effects is investigated. Special emphasis is put on the light clusters which e.g.~under certain conditions are only poorly represented by alpha particles. The important influence of the composition on the nucleosynthesis and on the neutrino dynamics and their spectra suggest the use of a grand canonical description of supernova matter.
Surface effects in color superconducting strange-q
Oertel, M (LUTH Meudon), Urban, M (IPN Orsay)
Surface effects in strange-quark matter play an important role for certain observables which have been proposed in order to identify strange stars, and color superconductivity can strongly modify these effects. We study the surface of color superconducting strange-quark matter by solving the Hartree-Fock-Bogoliubov equations for finite systems (``strangelets'') within the MIT bag model, supplemented with a pairing interaction. Due to the bag-model boundary condition, the strange-quark density is suppressed at the surface. This leads to a positive surface charge, concentrated in a layer of ~ 1 fm below the surface, even in the color-flavor locked (CFL) phase. However, since in the CFL phase all quarks are paired, this positive charge is compensated by a negative charge, which turns out to be situated in a layer of a few tens of fm below the surface, and the total charge of CFL strangelets is zero. We also study the surface and curvature contributions to the total energy. Due to the strong pairing, the energy as a function of the mass number is very well reproduced by a liquid-drop type formula with curvature term.
Subthreshold K+ Production and the Nuclear Equatio
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Simulations of strange star mergers and observatio
Bauswein, A. (MPA Garching), Pagliara, G. (Uni Hei
Hydrodynamical simulations of strange star mergers are presented. These studies allow to estimate the amount of strange matter that becomes gravitationally unbound and thus contributes to the cosmic ray flux of strangelets. Implications for the Madsen-Caldwell-Friedman argument are discussed. Gravitational wave features of this kind of mergers will be addressed as well.
Dynamics of Quantum Vorticity in the Neutron Star
Link, B (Montana State University)
I study the dynamics of a superfluid (SF) vortex in a random potential, as in the inner crust of a neutron star (NS). Below a critical flow velocity of the ambient SF, a vortex is effectively immobilized by lattice forces even in the limit of zero dissipation. Low-velocity, translatory motion is not dynamically possible, a result with important implications for understanding NS precession and the dynamical properties of SF nuclear matter.
Helical ordering in spin-one color superconductors
Brauner, T. (Frankfurt University)
We analyze spin-one color superconductivity of a single-flavor quark matter using the Ginzburg-Landau theory. By explicit minimization of the free energy we demonstrate that in a part of the parameter space the system exhibits a non-inert equilibrium state, different from states considered so far in literature. Finally we show that tiny weak-interaction effects induce a small parity-violating term in the Ginzburg-Landau functional, which causes the system to develop a long-range helical ordering in the ground state.
Protoneutron stars in the Brueckner-Bethe-Goldston
F. Burgio, M. Baldo, H.-J. Schulze
I will give a general overview of the equation of state derived in the Brueckner-Bethe-Goldstone many-body theory at finite temperature. The structure of protoneutron stars will be discussed.
Thermal Behavior of Compact Stars
Page, D. (Instituto de Astronomia, Universidad Nac
I will review the general characteristics of the thermal behavior of neutron and quark stars, in both contexts of isolated cooling stars and accreting stars in binary systems. Only complementary studies of these two types of systems offer real and serious chances to constrain models of dense matter.