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Register a new userCreation and evolution of particle numberasymmetry in an expanding universe
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We introduce a model which may generate particle number asymmetry in an expanding Universe. The model includes CP violating and particle number violating interactions. The model consists of a real scalar field and a complex scalar field. Starting with an initial condition specified by a density matrix, we show how the asymmetry is created through the interaction and how it evolves at later time. We compute the asymmetry using non-equilibrium quantum field theory and as a first test of the model, we study how the asymmetry evolves in the flat limit.
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Particle number violating interactions wash out the primordial asymmetry of particle number density generated by some interaction satisfying Sakharov conditions for baryogenesis. In this paper, we study how the primordial asymmetry evolves in time under the presence of particle number violating interactions and in the environment of expanding universe. We introduce a complex scalar model with particle number violating mass terms and calculate the time evolution of the particle number density with non-equilibrium quantum field theory. We show how the time evolution of the number density depends on parameters, including the chemical potential related with the particle number, temperature, size of the particle number violating mass terms, and the expansion rate of the universe. Depending upon whether the chemical potential is larger or smaller than the rest mass of the scalar particle, behaviors of the number density are very different to each other. When the chemical potential is smaller than the mass, the interference among the contribution of oscillators with various momenta reduces the number density in addition to the dilution due to the expansion of universe. In opposite case, the oscillation of the particle number density lasts for a long time and the cancellation due to the interference does not occur.
In the present article we study the process of particle creation for Elko spinor fields as a consequence of expansion of the universe. We study the effect driven by a expanding background that is asymptotically minkowskian in the past and future. The differential equation that governs the time mode function is obtained for the conformal coupling case and, although its solution is non-analytic, within an approximation that preserves the characteristics of the terms that break the analyticity, analytic solutions are obtained. Thus, by means of the Bogolyubov transformations technique, the number density of particles created is obtained, which can be compared to exact solutions already present in literature for scalar and Dirac particles. The spectrum of created particles is obtained and it was found that it is a generalization of the scalar field case, which converges to the scalar field one when the specific terms concerning the Elko field are dropped out. We also found that lighter Elko particles are created in larger quantities than Dirac fermionic particles. By considering the Elko particles as candidate to dark matter in the universe, such result shows that there are more light dark matter (Elko) particles created by gravitational effects in the universe than baryonic (fermionic) matter, in agreement to standard model.
In this article we investigate the effects of single derivative mixing in massive bosonic fields. In the regime of large mixing, we show that this leads to striking changes of the field dynamics, delaying the onset of classical oscillations and decreasing, or even eliminating, the friction due to Hubble expansion. We highlight this phenomenon with a few examples. In the first example, we show how an axion like particle can have its number abundance parametrically enhanced. In the second example, we demonstrate that the QCD axion can have its number abundance enhanced allowing for misalignment driven axion dark matter all the way down to $f_a$ of order astrophysical bounds. In the third example, we show that the delayed oscillation of the scalar field can also sustain a period of inflation. In the last example, we present a situation where an oscillating scalar field is completely frictionless and does not dilute away in time.
We show that entanglement can be used to detect spacetime curvature. Quantum fields in the Minkowski vacuum are entangled with respect to local field modes. This entanglement can be swapped to spatially separated quantum systems using standard local couplings. A single, inertial field detector in the exponentially expanding (de Sitter) vacuum responds as if it were bathed in thermal radiation in a Minkowski universe. We show that using two inertial detectors, interactions with the field in the thermal case will entangle certain detector pairs that would not become entangled in the corresponding de Sitter case. The two universes can thus be distinguished by their entangling power.
The gravitational action of the smooth energy-matter components filling in the universe can affect the orbit of a planetary system. Changes are related to the acceleration of the cosmological scale size R. In a universe with significant dark matter, a gravitational system expands or contracts according to the amount and equation of state of the dark energy. At present time, the Solar system, according to the LambdaCDM scenario emerging from observational cosmology, should be expanding if we consider only the effect of the cosmological background. Its fate is determined by the equation of state of the dark energy alone. The mean motion and periastron precession of a planet are directly sensitive to (d^2 R/d t^2)/R, whereas variations with time in the semi-major axis and eccentricity are related to its time variation. Actual bounds on the cosmological deceleration parameters q_0 from accurate astrometric data of perihelion precession and changes in the third Keplers law in the Solar system fall short of ten orders of magnitude with respect to estimates from observational cosmology. Future radio-ranging measurements of outer planets could improve actual bounds by five orders of magnitude.
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