  In this paper we study the electromagnetic scattering, absorption, and
performance bounds for short time modulated pulses that impinge on a
time-varying lossy layer that is sandwiched between vacuum and a perfect
electric conductor. The electric characteristics of the layer, namely, the
conductivity, permittivity, and permeability are assumed to change abruptly or
gradually in time. We demonstrate numerically that a time-varying absorbing
layer that undergoes temporal switching of its permittivity and conductance can
absorb the power of a modulated, ultra-wideband, as well as a
quasi-monochromatic, pulsed wave beyond what is dictated by the time invariant
Rozanov bound when integrating over the whole frequency spectrum. We suggest
and simulate a practical metamaterial realization that is constructed as a
three-dimensional array of resistor loaded dipole. By switching only the
dipole's load resistance, desired effective media properties are obtained.
Furthermore, we show that Rozanov's bound can be bypassed with abrupt and a
more practical gradual, soft, switching thus overcoming some possible causality
issue in abrupt switching.
