Causality and dielectric functions for linear media with spatial dispersion
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arXiv
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| Autori principali: | , |
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| Natura: | Preprint |
| Pubblicazione: |
2019
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| _version_ | 1866929509931941888 |
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| author | Llosa, Josep Salvat, Francesc |
| author_facet | Llosa, Josep Salvat, Francesc |
| contents | We extend Kramers-Kronig relations beyond the optical approximation to dielectric functions that depend not only on frequency but on the wave number as well. This implies extending the notion of causality commonly used in the theory of Kramers-Kronig relations to include the fact that signals cannot propagate faster than light in vacuo. The extension is applied to some microscopic models for the dielectric function and is compared with previous generalizations. The results derived here also apply to general theories of isotropic linear response in which the response function depends on both wave number and frequency. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_1905_06069 |
| institution | arXiv |
| publishDate | 2019 |
| record_format | arxiv |
| spellingShingle | Causality and dielectric functions for linear media with spatial dispersion Llosa, Josep Salvat, Francesc Classical Physics Mathematical Physics 30E15, 30E20, 78A99 We extend Kramers-Kronig relations beyond the optical approximation to dielectric functions that depend not only on frequency but on the wave number as well. This implies extending the notion of causality commonly used in the theory of Kramers-Kronig relations to include the fact that signals cannot propagate faster than light in vacuo. The extension is applied to some microscopic models for the dielectric function and is compared with previous generalizations. The results derived here also apply to general theories of isotropic linear response in which the response function depends on both wave number and frequency. |
| title | Causality and dielectric functions for linear media with spatial dispersion |
| topic | Classical Physics Mathematical Physics 30E15, 30E20, 78A99 |
| url | https://arxiv.org/abs/1905.06069 |