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1. Lack of Debye and Meissner screening in strongly magnetized quark matter at intermediate densities

   https://doi.org/https://doi.org/10.1103/PhysRevD.101.056012  

   B. Feng, E. J. (March 2020, Physical review)

   We study the static responses of cold quark matter in the intermediate baryonic density region(characterized by a chemical potentialμ) in the presence of a strong-magnetic field. We consider inparticular, the so-called magnetic dual Chiral Density Wave (MDCDW) phase, which is materialized by aninhomogeneous condensate formed by a particle-hole pair. It is shown, that the MDCDW phase is morestable in the weak-coupling regime than the one considered in the magnetic catalysis of chiral symmetrybraking phenomenon and even than the chiral symmetric phase that was expected to be realized atsufficiently high baryonic chemical potential. The different components of the photon polarization operatorof the MDCDW phase in the one-loop approximation are calculated. We found that in the MDCDW phasethere is neither Debye screening nor Meissner effect in the lowest-Landau-level approximation. Theobtained Debye length depends on the amplitudemand modulationbof the inhomogeneous condensateand it is only different from zero if the relation |μ−b|>m holds. But, we found that in the region ofinterest this inequality is not satisfied. Thus, no Debye screening takes place under those conditions. On theother hand, since the particle-hole condensate is electrically neutral, the U(1) electromagnetic group is notbroken by the ground state and consequently there is no Meissner effect. These results can be of interest forthe astrophysics of neutron stars 

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2. Effect of Strong Magnetic Field on Competing Order Parameters in Two-Flavor Dense Quark Matter

   https://doi.org/10.1155/2017/6472909  

   Mandal, Tanumoy; Jaikumar, Prashanth (January 2017, Advances in High Energy Physics)

   We study the effect of strong magnetic field on competing chiral and diquark order parameters in a regime of moderately dense quark matter. The interdependence of the chiral and diquark condensates through nonperturbative quark mass and strong coupling effects is analyzed in a two-flavor Nambu-Jona-Lasinio (NJL) model. In the weak magnetic field limit, our results agree qualitatively with earlier zero-field studies in the literature that find a critical coupling ratio G D / G S ~ 1.1 below which chiral or superconducting order parameters appear almost exclusively. Above the critical ratio, there exists a significant mixed broken phase region where both gaps are nonzero. However, a strong magnetic field B ≳ 1 0 18  G disrupts this mixed broken phase region and changes a smooth crossover found in the weak-field case to a first-order transition for both gaps at almost the same critical density. Our results suggest that in the two-flavor approximation to moderately dense quark matter strong magnetic field enhances the possibility of a mixed phase at high density, with implications for the structure, energetics, and vibrational spectrum of neutron stars. 

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3. Near-cancellation of up- and down-gradient momentum transport in forced magnetized shear-flow turbulence

   https://doi.org/arXiv:2208.03342  

   Tripathi, B.; Fraser, A. E.; Terry, P. W.; Zweibel, E. G.; Pueschel, M. J. (October 2022, Physics of plasmas)

   Visco-resistive magnetohydrodynamic turbulence, driven by a two-dimensional unstable shear layer that is maintained by an imposed body force, is examined by decomposing it into dissipationless linear eigenmodes of the initial profiles. The down-gradient momentum flux, as expected, originates from the large-scale instability. However, continual up-gradient momentum transport by large-scale linearly stable but nonlinearly excited eigenmodes is identified, and found to nearly cancel the down-gradient transport by unstable modes. The stable modes effectuate this by depleting the large-scale turbulent fluctuations via energy transfer to the mean flow. This establishes a physical mechanism underlying the long-known observation that coherent vortices formed from nonlinear saturation of the instability reduce turbulent transport and fluctuations, as such vortices are composed of both the stable and unstable modes, which are nearly equal in their amplitudes. The impact of magnetic fields on the nonlinearly excited stable modes is then quantified. Even when imposing a strong magnetic field that almost completely suppresses the instability, the up-gradient transport by the stable modes is at least two-thirds of the down-gradient transport by the unstable modes, whereas for weaker fields, this fraction reaches up to 98% . These effects are persistent with variations in magnetic Prandtl number and forcing strength. Finally, continuum modes are shown to be energetically less important, but essential for capturing the magnetic fluctuations and Maxwell stress. A simple analytical scaling law is derived for their saturated turbulent amplitudes. It predicts the fall-off rate as the inverse of the Fourier wavenumber, a property which is confirmed in numerical simulations. 

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4. NONLINEAR DYNAMICS AND DISSIPATION OF VORTEX LINES DRIVEN BY STRONG RF FIELDS

   https://doi.org/10.18429/JACoW-SRF2019-TUP055  

   W.P.M.R Pathirana; Alex Gurevich (January 2019, SRF)

   Trapped vortices can contribute significantly to a residual surface resistance of superconducting radio frequency (SRF) cavities but the nonlinear dynamics of flexible vortex lines driven by strong rf currents has not been yet investigated. Here we report extensive numerical simulations of large- amplitude oscillations of a trapped vortex line under the strong rf magnetic field. The rf power dissipated by an oscil- lating vortex segment driven by the rf Meissner currents was calculated by taking into account the nonlinear vortex line tension, vortex mass and a nonlinear Larkin-Ovchinnikov viscous drag force. We calculated the field dependence of the residual surface resistance R i and showed that at low frequencies R i (H) increases with H but as the frequency increases, R i (H) becomes a nonmonotonic function of H which decreases with H at higher fields. These results sug- gest that trapped vortices can contribute to the extended Q(H) rise observed on the SRF cavities. 

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5. Giant Hall Waves Launched by Superconducting Phase Transition in Pulsars

   https://doi.org/10.3847/1538-4357/ad90a3  

   Bransgrove, Ashley; Levin, Yuri; Beloborodov, Andrei M (January 2025, The Astrophysical Journal)

   Abstract The cores of pulsars are expected to become superconducting soon after birth. The transition to type-II superconductivity is associated with the bunching of magnetic field lines into discrete superconducting flux tubes which possess enormous tension. The coupling of the crust to the flux tubes implies the existence of huge tangential magnetic fields at the crust–core interface. We show that the transition to superconductivity triggers a highly nonlinear response in the Hall drift of the crustal magnetic field, an effect which was neglected in previous numerical modeling. We argue that at the time of the phase transition giant Hall waves are launched from the crust–core interface toward the surface. Our models show that if the crust contains a multipolar magnetic field ∼10¹³G, the amplitude of the Hall waves is ∼10¹⁵G. The elastic deformation of the lattice is included in our models, which allows us to track the time-dependent shear stresses everywhere in the crust. The simulations indicate that the Hall waves may be strong enough to break the crust, and could cause star quakes which trigger rotation glitches and changes in the radio pulse profile. The Hall waves also couple to slow magnetospheric changes, which cause anomalous braking indices. The emission of the giant Hall waves from the crust–core interface facilitates fast flux expulsion from the superconducting core, provided that the flux tubes in the core are themselves sufficiently mobile. For all of the flux tube mobility prescriptions implemented in this work, the core approaches the Meissner state withB= 0 at late times. 

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