Quintessence Research Papers

Quintessence Another genre of model for dark energy are the scalar-field models. Unlike the cosmological constant, the scalar-field models are dynamic. They hold that the force causing the accelerating expansion of the universe varies based on time and locations. Moreover, as the name suggests, scalar fields are used to demonstrate the magnitude at the specified point in space and time. In essence, they demonstrate that the fabric of space-time is not homogeneous. Consequently, a non-homogeneous universe leads to the idea that w, or the ratio of pressure to energy density, has actually evolved overtime. This means that it has not always been equal to negative one, as the cosmological constant holds. So, these models take time into account
Moreover, when T and V are positive, w becomes constrained to the inequality -1≤w≤1. However, if T is positive and V is negative, w can then be greater than 1 or less than -1. Thus, from the equation and the inequalities, if the kinetic energy of the quintessence field is greater than the potential energy then a positive w is produced. As a result, the pressure of the quintessence field would positive, like matter and radiation. A positive pressure for the quintessence filed would mean that it would be attractive and slow the expansion rate of the universe. However, at some point between the beginning of the universe and present day, the wave length of the quintessence field expanded to an extremely long wavelength. An extremely long wavelength, some sources state universe long wavelength, would cause the magnitude kinetic energy to drop below the potential energy of quintessence field. At this point, the positive pressure would become negative. A negative pressure means the quintessence field would be repulsive and fight against the attractive forces of matter and
wQ is unable to exceed the value of wB it can only be less than or equal to it. So, when wB=0 at the point of the matter-radiation equality, wQ must be zero or less. If wQ is less than zero then its pressure would become negative. Nevertheless, during the matter epoch, positive pressure continued to dominate and, with the dominance of positive pressure, the overall expansion of the universe is slowed. However, when the energy density of the quintessence field exceeded that of matter, beginning the current epoch, its negative pressure overcame the positive pressure exerted by matter and radiation to increase the expansion rate of the universe. In addition, Figure 2 demonstrates another characteristic of quintessence, tracker field. The tracker field solves a crucial problem of an unknown initial value for the energy density of the quintessence field. Essentially a tracker field means that the energy density of quintessence could be any of a wide range of initial values, which, despite its value, will track to a common evolutionary line. In Figure 2, the line “Q-field energy if initialρ_Q<<ρ_rad” is an example of an initial value that is within the tracker field. Regardless of the initial value’s value, it moves to the common evolutionary