Physics NotePublished
Is the Number of Photons Conserved in an Expanding Universe?
M. Novello; L. R. Oliveira; J. M. Salim
1988
Publication details
- Authors
- M. Novello; L. R. Oliveira; J. M. Salim
- Type
- Physics Note
- Status
- Published
- Publication date
- 1988
- Description
- We describe a Friedman - like scenario in which - due to gravitational interaction - the total number of photons existing in the Universe changes as the Universe expands. The photon number distribution function, in thermal equilibrium, exhibits an explicit dependence on a non-vanishing chemical potential term. This non-null value for the chemical potential of the photon is due to the presence of tidal effects, arising from the direct coupling of the photons - which, in a gravitational field, should not be treated as idealized point-like objects - to the curvature of space-time. As a result, the ratio <math>n_\gamma/n_B\,\!</math> between the numbers of photons and baryons in the Universe is shown to be not a constant, but rather a function of cosmic time, vanishing when the singularity of the standard FRW model is reached. In consequence, some of the supposed "fundamental problems" of standard Cosmology (e.g., the explanation of the constancy of the ratio <math>n_\gamma/n_B\,\!</math>, and thus of the origin of the total ammount of entropy observed today) are but apparent ones in the present scenario, and may be ''ipso facto'' solved.
- Year
- 1988
- Number
- CBPF-NF-058/88
- Linked to a thesis
- No
- Linked to a grant
- No