Title: Multi-kink collisions in the $ϕ^6$ model,
Abstract: We study simultaneous collisions of two, three, and four kinks and antikinks
of the $\phi^6$ model at the same spatial point. Unlike the $\phi^4$ kinks, the
$\phi^6$ kinks are asymmetric and this enriches the variety of the collision
scenarios. In our numerical simulations we observe both reflection and bound
state formation depending on the number of kinks and on their spatial ordering
in the initial configuration. We also analyze the extreme values of the energy
densities and the field gradient observed during the collisions. Our results
suggest that very high energy densities can be produced in multi-kink
collisions in a controllable manner. Appearance of high energy density spots in
multi-kink collisions can be important in various physical applications of the
Klein-Gordon model.