Vacuum friction

Abstract

We know that in empty space there is no preferred state of rest. This is true both in special relativity but also in Newtonian mechanics with its associated Galilean relativity. It comes as something of a surprise, therefore, to discover the existence a friction force associated with spontaneous emission. The resolution of this paradox relies on a central idea from special relativity even though our derivation of it is non-relativistic. We examine the possibility that the physics underlying this effect might be explored in an ion trap, via the observation of a superposition of different mass states.

Keywords:

• Optical forces
• spontaneous emission
• Doppler shifts
• trapped ions

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Publisher’s Note

Acknowledgements

We are grateful to Nils Trautmann, Mohamed Babiker, Jim Cresser and Helmut Ritsch with whom we have enjoyed many interesting discussions on this topic.

Notes

No potential conflict of interest was reported by the authors.

1 We could include, explicitly, the dipole radiation pattern but, for simplicity, consider a spatially averaged dipole.

2 Newton’s statement was: ‘Mutationem motus proportionalem esse vi motrici impressae & fieri secundum lineam rectam qua vis illa imprimitur.’ [19], rendered by Ball as ‘The change of momentum [per unit time] is always proportional to the moving force impressed, and takes place in the direction in which the force is impressed.’ [20]

Additional information

Funding

This work was supported by a Royal Society Research Professorship [RP150122]; the Austrian Science Fund FWF [grant number J 3703-N27].