Quantum size effects in the inner crust of neutron stars

Barranco, F.; Broglia, R. A.; Vigezzi, E.

doi:10.1088/0954-3899/37/6/064023

Cited by 5 publications

(8 citation statements)

References 49 publications

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“…In spherical nucleon removal models the residue momentum distributions depend strongly on the projections m of the valence nucleon total angular momentum j of the orbital [51]. Because the symmetry axis averaging process of the present model corresponds to an averaging over angular momentum projections in the spherical case, we would expect the calculated residue momentum distributions to depend strongly on θ .…”

Section: [202]5/2mentioning

confidence: 81%

Projectile deformation effects on single-nucleon removal reactions

Simpson

Tostevin

2012

Phys. Rev. C

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We discuss intermediate-energy single-nucleon removal reactions from deformed projectile nuclei. The removed nucleon is assumed to originate from a given Nilsson model single-particle state and the inclusive cross sections, to all rotational states of the residual nucleus, are calculated. We investigate the sensitivity of both the stripping cross sections and their momentum distributions to the assumed size of the model space in the Nilsson model calculations and to the shape of the projectile and residue. We show that the cross sections for small deformations follow the decomposition of the Nilsson state in a spherical basis. In the case of large and prolate projectile deformations the removal cross sections from prolate-like Nilsson states, having large values for the asymptotic quantum number n z , are reduced. For oblate-like Nilsson states, with small n z , the removal cross sections are increased. Whatever the deformation, the residue momentum distributions are found to remain robustly characteristic of the orbital angular momentum decomposition of the initial state of the nucleon in the projectile.

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Section: [202]5/2mentioning

confidence: 81%

Projectile deformation effects on single-nucleon removal reactions

Simpson

Tostevin

2012

Phys. Rev. C

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“…perturbation comes along and unpins many strongly pinned vortices simultaneously. The parameters of vortex pinning within a pulsar have been studied theoretically in great detail (Blasio & Lazzari 1998;Jones 1998b;Hirasawa & Shibazaki 2001;Jones 2003;Avogadro et al 2008;Barranco et al 2010). Of particular interest is the pinning strength, the density of pinning sites, and the region within the star where pinning is strongest (the superfluid pairing state changes with depth).…”

Section: Container and Pinning Potentialmentioning

confidence: 99%

“…The GPE is a standard tool in condensed matter physics for investigating vortex dynamics in quantum condensates (Pethick & Smith 2002). Our simulations are unique in four ways: (1) the system is much larger than those routinely ⋆ lilaw@ph.unimelb.edu.au (LW) simulated in condensed matter applications (Tsubota et al 2002;Penckwitt 2003, for example), and therefore contains many more vortices; (2) in addition to the confining potential, we include a grid of pinning sites to model nuclear lattice defects in the pulsar's crust (Jones 1998b;Donati & Pizzochero 2004Avogadro et al 2007Avogadro et al , 2008; Barranco et al 2010); (3) the container and superfluid are coupled via a feedback torque; and (4) we allow the angular velocity of the container to change non-adiabatically. Thus, the simulations describe scales ranging from individual vortex cores to the collective behaviour of several hundred vortices in the presence of a large grid of pinning sites.…”

Section: Introductionmentioning

confidence: 99%

Gross-Pitaevskii model of pulsar glitches

Warszawski

Melatos

2011

Monthly Notices of the Royal Astronomical Society

138

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The first large-scale quantum mechanical simulations of pulsar glitches are presented, using a Gross-Pitaevskii model of the crust-superfluid system in the presence of pinning. Power-law distributions of simulated glitch sizes are obtained, in accord with astronomical observations, with exponents ranging from -0.55 to -1.26. Examples of large-scale simulations, containing $\sim 200$ vortices, reveal that these statistics persist in the many-vortex limit. Waiting-time distributions are also constructed. These and other statistics support the hypothesis that catastrophic unpinning mediated by collective vortex motion produces glitches; indeed, such collective events are seen in time-lapse movies of superfluid density. Three principal trends are observed. (1) The glitch rate scales proportional to the electromagnetic spin-down torque. (2) A strong positive correlation is found between the strength of vortex pinning and mean glitch size. (3) The spin-down dynamics depend less on the pinning site abundance once the latter exceeds one site per vortex, suggesting that unpinned vortices travel a distance comparable to the inter-vortex spacing before repinning.Comment: 24 pages, 19 figures, accepted for publication in MNRA

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“…This is not to say that there has not been progress. The relevant microphysics, especially concerning the interaction between neutron vortices and crust nuclei [19][20][21][22][23][24][25][26], is better understood, leading to a clearer idea of the location of the superfluid reservoir associated with the events. Observations support the notion that the vortices are (mainly) pinned in the crust and hence the angular momentum available is that associated with the crust superfluid.…”

Section: B Pulsar Glitchesmentioning

confidence: 99%

“…As the present focus is on dynamical aspects, we will only consider the last of these aspects here.Even though the problem of neutron star superfluidity has been under scrutiny since the late 1960s (following the original suggestion of Migdal [13]), many relevant aspects remain unresolved (see [14][15][16] for recent reviews). These range from nuclear physics issues, like the pairing [17,18] and the critical temperature (with the neutron triplet pairing gap-roughly the binding energy of a Cooper pair-still uncertain) and the interaction between quantised neutron vortices and crust nuclei leading to vortex pinning [19][20][21][22][23][24][25][26], to large-scale dynamics and the impact on astrophysical observations, with the mechanism that triggers pulsar glitches remaining not well understood. This brief survey is intended to serve an introduction to dynamical aspects that come into play when we consider a superfluid neutron star.…”

mentioning

confidence: 99%

A superfluid perspective on neutron star dynamics

Andersson

2021

Preprint

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As mature neutron stars are cold (on the relevant temperature scale), one has to carefully consider the state of matter in their interior. The outer kilometer or so is expected to freeze to form an elastic crust of increasingly neutron-rich nuclei, coexisting with a superfluid neutron component, while the star's fluid core contains a mixed superfluid/superconductor. The dynamics of the star depend heavily on the parameters associated with the different phases. The presence of superfluidity brings new degrees of freedom-in essence we are dealing with a complex multi-fluid systemand additional features: Bulk rotation is supported by a dense array of quantised vortices, which introduce dissipation via mutual friction, and the motion of the superfluid is affected by the socalled entrainment effect. This brief survey provides an introduction to-along with a commentary on our current understanding of-these dynamical aspects, paying particular attention to the role of entrainment, and outlines the impact of superfluidity on neutron-star seismology. I. NEUTRON STAR SUPERFLUIDITYDuring its first moments of existence, just after the supernova core collapse, a newly born neutron star can be thought of as a hot, rotating, "ball" of superdense nuclear material. Thermal aspects play a key role during the early stages of evolution, and it is essentially the loss of the associated pressure support (through the emission of neutrinos) that leads to the newly born object shrinking from a radius of about 20 km to the typical size of a "mature" neutron star; likely just over 10 km. Once the temperature drops below about 10 10 K (or 1 MeV for anyone of a nuclear physics persuasion)-after the first 20-100 s [1]-the thermal contribution to the pressure may be ignored and we can meaningfully consider the object as a-now gradually evolving-neutron star. From the nuclear physics point of view, the object is cold. In fact, it so cold that we have to consider the precise state of matter.Laboratory experiments tell us that two things may happen when we cool a fluid. It may freeze-as in the familiar winter-time example of water forming ice-or it may become superfluid-as in the case of low-temperature laboratory experiments on Helium. The latter outcome is less common, as it requires quantum fluctuations to prevent the formation of a regular particle lattice. However, neutron stars-obviously, not hands-on laboratories!-are expected to manifest both phases. The outer kilometer or so forms the star's crust, a lattice composed of increasingly neutronrich nuclei [2]. The outer core of the star is expected to contain a mixture of superfluid neutrons-forming a condensate due to an analogue of Cooper pairing below a density-dependent critical temperature, see figure 1-alongside a charge neutral conglomerate of protons and electrons (with muons also coming into play as the density increases). This may already seem a fairly complicated system, but we need (at least) two further features. First, beyond a density of about 4 × 10 11 g/cm 3 , neutrons start...

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Quantum size effects in the inner crust of neutron stars

Cited by 5 publications

References 49 publications

Projectile deformation effects on single-nucleon removal reactions

Projectile deformation effects on single-nucleon removal reactions

Gross-Pitaevskii model of pulsar glitches

A superfluid perspective on neutron star dynamics

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