Gravitational particle production: a mathematical treatment

Haro, Jaume de

doi:10.1088/1751-8113/44/20/205401

Cited by 23 publications

(38 citation statements)

References 45 publications

(65 reference statements)

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“…The first point is essential for the viability of the model because if one is dealing with light minimally coupled particles, in order to calculate mode solutions of equation (28), and thus, to define the vacuum state after the phase transition one needs a nearly constant effective EoS parameter (w ef f ). In that case, the vacuum modes after the phase transition will be (see [29], where a similar situation was studied in the context of bouncing cosmologies)…”

Section: −4mentioning

confidence: 99%

“…On the other hand, although w ef f was constant after the phase transition, when the field is not nearly conformally coupled, it would be a very difficult task to find vacuum modes before the phase transition, because to obtain them one firstly needs to calculate numerically the scale factor as a function of the conformal time, which could only be done solving numerically the conservation equation obtaining ϕ(t), and consequently the Hubble parameter H(t). With this Hubble parameter, one can numerically calculate the scale factor as a function of the conformal time, and finally, once the scale factor has been calculated, one has to solve the differential equation (28).…”

Section: −4mentioning

confidence: 99%

“…In that case, since the Hubble parameter is continuous up to second derivative, during the adiabatic regimes, we will use the second order WBK solution to define approximately the vacuum modes [28] …”

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confidence: 99%

“…Then the square modulus of the β-Bogoliubov coefficient is obtained by calculating the square modulus of the [28,29]), where χ W KB 2,k (τ ) is evaluated after and before the phase transition. It is not difficult to show that it will be given by…”

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Simple inflationary quintessential model

2016

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In the framework of a flat Friedmann-Lemaître-Robertson-Walker (FLRW) geometry, we present a non-geodesically past complete model of our universe without the big bang singularity at finite cosmic time, describing its evolution starting from its early inflationary era up to the present accelerating phase. We found that a hydrodynamical fluid with nonlinear equation of state could result in such scenario, which after the end of this inflationary stage, suffers a sudden phase transition and enters into the stiff matter dominated era, and the universe becomes reheated due to a huge amount of particle production. Finally, it asymptotically enters into the de Sitter phase concluding the present accelerated expansion. Using the reconstruction technique, we also show that, this background provides an extremely simple inflationary quintessential potential whose inflationary part is given by the well-known 1-dimensional Higgs potential, i.e., a Double Well Inflationary potential, and the quintessential one by an exponential potential that leads to a deflationary regime after this inflation, and it can depict the current cosmic acceleration at late times. Moreover the Higgs potential leads to a power spectrum of the cosmological perturbations which fit well with the latest Planck estimations. Further, we compared our viable potential with some known inflationary quintessential potential, which shows that our quintessential model, that is, the Higgs potential combined with the exponential one, is an improved version of them because it contains an analytic solution that allows us to perform all analytic calculations. Finally, we have shown that the introduction of a non zero cosmological constant simplifies the potential considerably with an analytic behavior of the background which again permits us to evaluate all the quantities analytically. INTRODUCTIONThe complete evolution of our universe is still a mystery, and probably, one of the most interesting topics in the history of cosmology. Until now, we have some theories describing different phases of our universe, in agreement with the latest observations, which tell us that our universe underwent a rapid accelerating phase during its very early evolution, namely, the inflation [1, 2], and presently it is going through a phase of accelerated expansion [3,4]. The gap between these two successive accelerating expansions is described by three sequential decelerated phases, the first one is the stiff matter dominated era, then there was a radiation dominated phase, and finally, before its current accelerating phase, the universe was matter dominated. However, since the beginning of modern cosmology, the big bang still remains as one of the controversial issues for cosmologists. Hence, it has been questioned several times, and alternatively, an existence of some kind of "nonsingular" universe (a model of our universe without finite cosmic time singularity) [5] has been proposed just to replace this big bang singularity, but the evolution of the universe will remain same. As a ...

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Section: −4mentioning

confidence: 99%

Section: −4mentioning

confidence: 99%

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Simple inflationary quintessential model

2016

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“…Thus, the case of gravitons has to be considered in another way, because for them ξ = 0. This was done in [54], where the IR singularity is removed assuming an early radiation phase before inflation (see [55]). Then, let a i be the scale factor when the universe passes from the early radiation phase to inflation.…”

Section: Discussionmentioning

confidence: 99%

Quintessential inflation at low reheating temperatures

Saló

Haro

2017

Eur. Phys. J. C

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We have tested some simple quintessential inflation models, imposing the requirement that they match with the recent observational data provided by the BICEP and Planck team and leading to a reheating temperature, which is obtained via gravitational particle production after inflation, supporting the nucleosynthesis success. Moreover, for the models coming from supergravity one needs to demand low temperatures in order to avoid problems such as the gravitino overproduction or the gravitational production of moduli fields, which are obtained only when the reheating temperature is due to the production of massless particles with a coupling constant very close to its conformal value.

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