We investigate local environmental effects from dark matter (DM) on thermonuclear supernovae (SNe Ia) using publicly available archival data of 224 low-redshift events, in an attempt to shed light on the SN Ia progenitor systems. SNe Ia are explosions of carbon-oxygen (CO) white dwarfs (WDs) that have recently been shown to explode at sub-Chandrasekhar masses; the ignition mechanism remains, however, unknown. Recently, it has been shown that both weakly interacting massive particles (WIMPs) and macroscopic DM candidates such as primordial black holes (PBHs) are capable of triggering the ignition. Here, we present a method to estimate the DM density and velocity dispersion in the vicinity of SN Ia events and nearby WDs; we argue that (i) WIMP ignition is highly unlikely, and that (ii) DM in the form of PBHs distributed according to a (quasi-) log-normal mass distribution with peak $\log_{10}(m_0/1$g$)=24.9\pm 0.9$ and width $\sigma= 3.3\pm 1.0$ is consistent with SN Ia data, the nearby population of WDs and roughly consistent with other constraints from the literature.

A magnon is a collective excitation of the spin structure in a magnetic insulator and can transmit spin angular momentum with negligible dissipation. This quantum of a spin wave has always been manipulated through magnetic dipoles (that is, by breaking time-reversal symmetry). Here we report the experimental observation of chiral spin transport in multiferroic BiFeO₃ and its control by reversing the ferroelectric polarization (that is, by breaking spatial inversion symmetry). The ferroelectrically controlled magnons show up to 18% modulation at room temperature. The spin torque that the magnons in BiFeO₃ carry can be used to efficiently switch the magnetization of adjacent magnets, with a spin-torque efficiency comparable to the spin Hall effect in heavy metals. Utilizing such controllable magnon generation and transmission in BiFeO₃, an all-oxide, energy-scalable logic is demonstrated composed of spin-orbit injection, detection and magnetoelectric control. Our observations open a new chapter of multiferroic magnons and pave another path towards low-dissipation nanoelectronics.