Chemical potential and the nature of dark energy: The case of a phantom field
- Departamento de Astronomia, Universidade de Sao Paulo, Rua do Matao, 1226 - 05508-900, Sao Paulo, Sao Paulo (Brazil)
The influence of a possible nonzero chemical potential {mu} on the nature of dark energy is investigated by assuming that the dark energy is a relativistic perfect simple fluid obeying the equation of state, p={omega}{rho} ({omega}<0, constant). The entropy condition, S{>=}0, implies that the possible values of {omega} are heavily dependent on the magnitude, as well as on the sign of the chemical potential. For {mu}>0, the {omega} parameter must be greater than -1 (vacuum is forbidden) while for {mu}<0 not only the vacuum but even a phantomlike behavior ({omega}<-1) is allowed. In any case, the ratio between the chemical potential and temperature remains constant, that is, {mu}/T={mu}{sub 0}/T{sub 0}. Assuming that the dark energy constituents have either a bosonic or fermionic nature, the general form of the spectrum is also proposed. For bosons {mu} is always negative and the extended Wien's law allows only a dark component with {omega}<-1/2, which includes vacuum and the phantomlike cases. The same happens in the fermionic branch for {mu}<0. However, fermionic particles with {mu}>0 are permitted only if -1<{omega}<-1/2. The thermodynamics and statistical arguments constrain the equation-of-state parameter to be {omega}<-1/2, a result surprisingly close to the maximal value required to accelerate a Friedmann-Robertson-Walker-type universe dominated by matter and dark energy ({omega} < or approx. -10/21)
- OSTI ID:
- 21254388
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 78, Issue 8; Other Information: DOI: 10.1103/PhysRevD.78.083504; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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