Hypernuclear matter in strong magnetic field

TL;DR

This paper investigates how extremely strong magnetic fields affect the properties and stability of hypernuclear matter inside magnetars, revealing a critical field strength beyond which matter becomes unstable.

Contribution

It provides a detailed analysis of the equation of state and stability of hypernuclear matter under ultra-strong magnetic fields using the non-linear Boguta-Bodmer-Walecka model, identifying a critical magnetic field limit.

Findings

Magnetic fields above 10^{17} G significantly influence matter properties.

Hypernuclear matter becomes unstable at magnetic fields around 10^{19} G.

Stable hypernuclear matter in magnetars must have magnetic fields below approximately 10^{19} G.

Abstract

Compact stars with strong magnetic fields (magnetars) have been observationally determined to have surface magnetic fields of order of 10^{14}-10^{15} G, the implied internal field strength being several orders larger. We study the equation of state and composition of dense hypernuclear matter in strong magnetic fields in a range expected in the interiors of magnetars. Within the non-linear Boguta-Bodmer-Walecka model we find that the magnetic field has sizable influence on the properties of matter for central magnetic field B \ge 10^{17} G, in particular the matter properties become anisotropic. Moreover, for the central fields B \ge 10^{18} G, the magnetized hypernuclear matter shows instability, which is signaled by the negative sign of the derivative of the pressure parallel to the field with respect to the density, and leads to vanishing parallel pressure at the critical value B_{\rm cr} \simeq 10^{19} G. This limits the range of admissible homogeneously distributed fields in magnetars to fields below the critical value B_{\rm cr}.