11-12 December 2018
Center for Astrophysics and Gravitation, Instituto Superior Técnico, University of Lisbon
Europe/Lisbon timezone

e- e+ plasma-dark electromagnetism similarity establishes a (nearly) weaker-than-gravity bound on long-range dark matter self-interactions

12 Dec 2018, 15:50
10m
Anfiteatro Abreu Faro (Center for Astrophysics and Gravitation, Instituto Superior Técnico, University of Lisbon)

Anfiteatro Abreu Faro

Center for Astrophysics and Gravitation, Instituto Superior Técnico, University of Lisbon

Av. Rovisco Pais 1 1049-001 Lisboa, PORTUGAL

Speaker

Nitin Shukla (GoLP/Instituto de Plasmas e Fus\~ao Nuclear, Instituto Superior T\'ecnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal)

Description

Dark matter (DM) has been theorized to be charged under its own "dark electromagnetism" (DEM). Under this hypothesis, DM can behave like a cold collisionless plasma of self-interacting DM particles, and exhibit plasma-like instabilities with observational consequences [1,2]. Using PIC simulations [3], the nonlinear evolution of such instabilities driven by the interpenetration of two $e^-\,e^+$ plasma clouds that mimic the ``dark plasma" are explored. We show that the clouds slow down due to both oblique and Weibel generated electromagnetic fields, which deflect the particle trajectories, transferring bulk forward momentum into transverse momentum and thermal velocity spread. This process causes the flow velocity to decrease from $v_{fl}$ by a factor of $\sqrt{3}$ in a time interval $\Delta t \omega_p \sim 1/\sqrt{\alpha} (c/v_{fl})$, close to 10 $\times$ the instability growth time, where $\alpha$ is the equipartition parameter determined by the non-linear saturation of the instabilities, and $\omega_p$ is the plasma frequency. We show that if the typical DM slab length $L > v_{fl} \Delta t$, this slowdown is always expected. Comparison with astronomical observations reveal strong new constraints on DEM with the dark electromagnetic self-interaction $\alpha_{D} < 4 \times 10^{-25}$.
[1] Heikinheimo et. al PRB 749 7 (2015) [2] Fonseca et al., PPCF 50, 124034 (2008)

Primary authors

Nitin Shukla (GoLP/Instituto de Plasmas e Fus\~ao Nuclear, Instituto Superior T\'ecnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal) Dr Kevin Schoeffler (GoLP/Instituto de Plasmas e Fus\~ao Nuclear, Instituto Superior T\'ecnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal) Dr Jorge Vieira (GoLP/Instituto de Plasmas e Fus\~ao Nuclear, Instituto Superior T\'ecnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal) Dr Jeremy Mardon (Stanford Institute for Theoretical Physics, Department of Physics, Stanford University, Stanford, CA 94305) Dr Brain Feldstein ((Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP UK)) Prof. Ricardo Fonseca (ISCTE - Inst Universitario Lisboa , Inst Superior Tecnico (IST)) Prof. Luis Silva (GoLP/Instituto de Plasmas e Fus\~ao Nuclear, Instituto Superior T\'ecnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal)

Presentation Materials