title: Unphysical consequences of negative absorbed power in linear passive scattering: Implications for radiation force and torque.
abstract: Contrary to some claims, the absorbed power associated with linear scattering of sound by passive objects in ideal fluids must be non-negative. Such unphysical claims suggest analytical or computational error, or use of an unphysical constitutive relation for material properties. The close connection with the evaluation of acoustic radiation force on targets according to Westervelt's formulation [J. Acoust. Soc. Am. 29, 26-29 (1957)], recently generalized to certain acoustic beams, is briefly reviewed along with the theory of acoustic radiation torque on axisymmetric targets with power absorption. Applications to viscous dissipation and to issues pertaining to active targets are also examined.
authors.affiliation: Physics and Astronomy Department, Washington State University, Pullman, Washington 99164-2814, USA.
authors.forename: Philip L
authors.initials: PL
authors.lastname: Marston
authors.affiliation: Physics Department, University of Texas, Austin, Texas 78712, USA.
authors.forename: Likun
authors.initials: L
authors.lastname: Zhang