Magnetic phases in three-flavor color superconductivity

Abstract

The best natural candidates for the realization of color superconductivity are quark stars -not yet confirmed by observation-and the extremely dense cores of compact stars, many of which have very large magnetic fields. To reliably predict astrophysical signatures of color superconductivity, a better understanding of the role of the star's magnetic field in the color superconducting phase that realizes in the core is required. This paper is an initial step in that direction. The field scales at which the different magnetic phases of a color superconductor with three quark flavors can be realized are investigated. Coming from weak to strong fields, the system undergoes first a symmetry transmutation from a Color-Flavor-Locked (CFL) phase to a Magnetic-CFL (MCFL) phase, and then a phase transition from the MCFL phase to the Paramagnetic-CFL (PCFL) phase.The low-energy effective theory for the excitations of the diquark condensate in the presence of a magnetic field is derived using a covariant representation that takes into account all the Lorentz structures contributing at low energy. The field-induced masses of the charged mesons and the threshold field at which the CFL → MCFL symmetry transmutation occurs are obtained in the framework of this low-energy effective theory. The relevance of the different magnetic phases for the physics of compact stars is discussed.

Chiral transition in a magnetic field and at finite baryon density

“…The effects of external magnetic fields on the chiral transition have been studied in detail using the NJL model [41][42][43][44][45][46][47][48][49][50], the Polyakov-loop extended NJL model [51][52][53], the QM model [49,50,54], the (P)QM model [55], and the instanton-liquid model [56]. Similarly, the effects of strong magnetic field on the various color superconducting phases have been studied using the NJL model [57][58][59][60][61].…”

Magnetism in Dense Quark Matter

“…During this phase transmutation no symmetry breaking occurs, since in principle once a magnetic field is present the symmetry is strictly speaking that of the MCFL, as discussed above. However, in practice for B ∼ B MCFL ∼ ∆ 2 CFL the main features of MCFL emerge through the low-energy behavior of the system [62]. At the threshold field B MCFL , only five neutral Goldstone bosons remain out of the original nine characterizing the low-energy behavior of the CFL phase, because the charged Goldstone bosons acquire field dependent masses and can decay in lighter modes.…”

“…The less symmetric realization of the CFL pairing that occurs in the presence of a magnetic field, is known as the magnetic-CFL (MCFL) phase [56,57,58,59]. The MCFL phase has similarities, but also important differences with the CFL phase [56,57,58,59,62,111,112].…”

“…In other words, what is the threshold-field strength that effectively separates the CFL low energy behavior from the MCFL one? A fundamental clue in this direction was found in [62] by determining the term in the low-energy CFL Lagrangian that generates a field-induced mass for the charged Goldstone fields, so disconnecting them from the low-energy dynamics at some field strength and thereby effectively reducing the number of Goldstone bosons from the nine of the CFL phase, to the five neutral ones of the MCFL.…”

Directional dependence of a color superconducting gap in two-flavor QCD in a magnetic field

“…Recently, the study of color superconductivity in the presence of magnetic fields attracted a lot of attention [21][22][23][24][25]. This interest is primarily driven by potential astrophysical applications, where magnetic fields play an important role.…”