Boson stars

Boson stars with negative cosmological constant

“…The stability against perturbations around the equilibrium state has been discussed also by a number of authors [21]- [24]. An extensive review of the boson star properties is given in [25], [26].…”

Energy conditions and classical scalar fields

“…Eq. (2.18) then yields 19) where λ is an affine parameter along the worldlines of fluid particles. Eq.…”

“…As an example, consider the well known chaotic inflationary scenario with the potential V = λφ 4 ; the inclusion of NMC with a value of ξ as small as 10 −3 prevents the existence of inflationary solutions unless an unacceptable fine-tuning is allowed, thus ruining an inflationary scenario which is very successful for ξ = 0 [16]. NMC is relevant in cosmology (during inflation and the quintessence era) [17], quantum cosmology [18], and in the physics of boson stars [19] and wormholes [20]. Recently 4 , it was pointed out that the innocent-looking theory described by the action (1.1) leads to negative energy fluxes [22], opening the door to exotica such as traversable wormholes [22], warp drives [23], and time machines [20].…”

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“…Whichever point of view one adopts, with motivations arising in a range of areas as wide as quantum field theory in curved spaces, wormholes [37], black holes [38], boson stars [39,40], specific inflationary scenarios, a pure relativist's approach, or merely a pragmatic one, the message is that in general it is wise not to ignore the NMC term by setting ξ = 0, as done in ordinary inflation. Although the inclusion of NMC makes the analysis considerably more difficult, and it was unknown in the early, pioneering days of inflationary theory, the times are mature for the inclusion of NMC in the theory.…”

“…The power spectrum of a quantity f (t, x) is defined as 39) where x denotes an average over the spatial coordinates x and f k (t) are the coefficients of the Fourier expansion…”