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A<sc>bstract</sc> Using first-principles field-theoretic methods, we investigate neutrino emission from strongly magnetized dense quark matter under conditions relevant to compact stars. We develop a customized approximation that fully accounts for the Landau-level quantization of electron states while neglecting such quantization for quarks. This approach is well-justified in dense quark matter, where the chemical potentials of up and down quarks significantly exceed those of electrons. Our analysis provides a detailed exploration of the influence of strong magnetic fields on neutrino emission, including both the modification of the total emission rate and the emergence of emission asymmetry relative to the magnetic field direction. We further examine the role of temperature in smoothing the oscillatory behavior of neutrino emission as a function of magnetic field strength. Additionally, we study the interplay between the Landau-level quantization of electrons and the Fermi-liquid effects of quarks in modifying the phase space of relevant weak processes. Finally, we briefly discuss the broader implications of magnetic fields on stellar cooling processes and the potential contribution of asymmetric neutrino emission to pulsar kicks. 

We investigate the emission of circularly polarized photons from a magnetized quark-gluon plasma with nonzero quark-number and chiral charge chemical potentials. These chemical potentials qualitatively influence the differential emission rates of circularly polarized photons. A nonzero net electric charge density, induced by quark-number chemical potentials, enhances the overall emission of one circular polarization over the other, while a nonzero chiral charge density introduces a spatial asymmetry in the emission with respect to reflection in the transverse plane. The signs of the electrical and chiral charge densities determine which circular polarization dominates overall and whether the emission preferentially aligns with or opposes the magnetic field. Based on these findings, we propose that polarized photon emission is a promising observable for characterizing the quark-gluon plasma produced in heavy-ion collisions. Published by the American Physical Society2024 

We employ first-principles quantum field theoretical methods to investigate the longitudinal and transverse electrical conductivities of a strongly magnetized hot quantum electrodynamics (QED) plasma at the leading order in coupling. The analysis employs the fermion damping rate in the Landau-level representation, calculated with full kinematics and exact amplitudes of one-to-two and two-to-one QED processes. In the relativistic regime, both conductivities exhibit an approximate scaling behavior described by ${\sigma }_{\parallel ,\perp }=T{\tilde{\sigma }}_{\parallel ,\perp }$, where ${\tilde{\sigma }}_{\parallel ,\perp }$are functions of the dimensionless ratio $\left|eB\right|/T^2$(with $T$denoting temperature and $B$magnetic field strength). We argue that the mechanisms for the transverse and longitudinal conductivities differ significantly, leading to a strong suppression of the former in comparison to the latter. Published by the American Physical Society2024 

We derive a general expression for the fermion self-energy in a hot magnetized plasma by using the Landau-level representation. In the one-loop approximation, the Dirac structure of the self-energy is characterized by five different functions that depend on the Landau-level index $n$and the longitudinal momentum $p_z$. We derive general expressions for all five functions and obtain closed-form expressions for their imaginary parts. The latter receive contributions from three types of on shell processes, which are interpreted in terms of Landau-level transitions, accompanied by a single photon (gluon) emission or absorption. By making use of the imaginary parts of the self-energy functions, we also derive the Landau-level dependent fermion damping rates ${\mathrm{\Gamma }}_n\left(p_z\right)$and study them numerically in a wide range of model parameters. We also demonstrate that the two-spin degeneracy of the Landau levels is lifted by the one-loop self-energy corrections. While the spin splitting of the damping rates is small, it may be important for some spin and chiral effects. We argue that the general method and the numerical results for the rates can have interesting applications in heavy-ion physics, astrophysics, and cosmology, where strongly magnetized QED or QCD plasmas are ubiquitous. Published by the American Physical Society2024 

We study the higher-order anisotropy coefficients $$v_4$$ and $$v_6$$ in the photon and dilepton emission from a hot magnetized quark-gluon plasma. Together with the earlier predictions for $$v_2$$, these results show a distinctive pattern of the anisotropy coefficients in several kinematic regimes. In the case of photon emission, nonzero coefficients $$v_n$$ (with even $$n$$) have opposite signs at small and large values of the transverse momentum (i.e., $$k_T\lesssim \sqrt{|eB|}$$ and $$k_T\gtrsim \sqrt{|eB|}$$, respectively). Additionally, the $$v_n$$ signs alternate with increasing $$n$$, and their approximate values decrease as $1/n^2$ in magnitude. The anisotropy of dilepton emission is well pronounced only at large transverse momenta and small invariant masses (i.e., when $$k_T\gtrsim \sqrt{|eB|}$$ and $$M\lesssim \sqrt{|eB|}$$). The corresponding $$v_4$$ and $$v_6$$ coefficients are of the same magnitude and show a similar alternating sign pattern with increasing $$n$$ as in the photon emission. 

We investigate the differential emission rate of neutral scalar bosons from a highly magnetized relativistic plasma. We show that three processes contribute at the leading order: particle splitting ($$\psi\rightarrow \psi+\phi $$), antiparticle splitting ($$\bar{\psi} \rightarrow \bar{\psi}+\phi $$), and particle-antiparticle annihilation ($$\psi + \bar{\psi}\rightarrow \phi $$). This is in contrast to the scenario with zero magnetic field, where only the annihilation processes contribute to boson production. We examine the impact of Landau-level quantization on the energy dependence of the rate and investigate the angular distribution of emitted scalar bosons. The differential rate resulting from both (anti)particle splitting and annihilation processes are typically suppressed in the direction of the magnetic field and enhanced in perpendicular directions. Overall, the background magnetic field significantly amplifies the total emission rate. We speculate that our model calculations provide valuable theoretical insights with potentially important applications. 

The validity of conventional Ohm’s law is tested in the context of a rapidly evolving quark–gluon plasma produced in heavy-ion collisions. Here, we discuss the electromagnetic response using an analytical solution in kinetic theory. As conjectured previously, after switching on an electric field in a nonexpanding plasma, the time-dependent current is given by J(t)=(1−e−t/τ0)σ0E, where τ0 is the transport relaxation time and σ0 is the steady-state electrical conductivity. Such an incomplete electromagnetic response reduces the efficiency of the magnetic flux trapping in the quark–gluon plasma, and may prevent the observation of the chiral magnetic effect. Here, we extend the study to the case of a rapidly expanding plasma. We find that the decreasing temperature and the increasing transport relaxation time have opposite effects on the electromagnetic response. While the former suppresses the time-dependent conductivity, the latter enhances it. 

Abstract We propose that chirally asymmetric plasma can be produced in the gap regions of the magnetospheres of pulsars and black holes. We show that, in the case of supermassive black holes situated in active galactic nuclei, the chiral charge density and the chiral chemical potential are very small and unlikely to have any observable effects. In contrast, the chiral asymmetry produced in the magnetospheres of magnetars can be substantial. It can trigger the chiral plasma instability that, in turn, can lead to observable phenomena in magnetars. In particular, the instability should trigger circularly polarized electromagnetic radiation in a wide window of frequencies, spanning from radio to near-infrared. As such, the produced chiral charge has the potential to affect some features of fast radio bursts.