Cosmic Acceleration and Dark Energy
C. Sivakumar
Abstract A missing energy called dark energy in the universe is essential to account
for many recent observations. An effective equation of state parameter that represents the cosmic fluid of the universe is postulated to predict the evolution of our
flat universe which is presently expanding with an acceleration under the negative
pressure of such a dark energy. Here a model is proposed to successfully describe the
evolution of the universe after the inflationary epoch to a time when the size of the
universe would be infinite, crossing the time of its shift from the phase of deceleration
to acceleration using a simple equation of state consistent with the cosmic scenario.
Keywords Scale factor · Equation of state · Flat universe · Dark energy
1 Introduction
The development of GTR and cosmology is a major scientific success of the twentieth
century. One of the solutions of Einstein’s field equations is the Friedmann model,
also called standard model in cosmology, which is based on cosmological principle.
Recent observations suggest that ratio of energy density to critical density is one,
that is, universe is flat. But the matter density including both baryonic and dark is
only a small fraction of total density. So there is a missing energy called dark energy.
Since 1998, when observations of supernovae Type-Ia pointed accelerated cosmic
expansion, various observational measurements have established such evolutionary
change in the history of the late universe. To find the source behind the late cosmic
acceleration is certainly a major challenge for cosmologists.
The acceleration in the expansion of the universe is one of the remarkable discoveries in recent cosmological research. This acceleration requires that nearly threequarters of the energy of the universe is in a component of fluid energy density with
a negative pressure. Many dark energy models are proposed to explain this accelC. Sivakumar (B)
Department of Physics, Maharaja’s College, Kochi, Kerala, India
e-mail: thrisivc@yahoo.com
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
K. S. Sreelatha and V. Jacob (eds.), Modern Perspectives in Theoretical Physics,
https://doi.org/10.1007/978-981-15-9313-0_2
17
C. Sivakumar
Abstract A missing energy called dark energy in the universe is essential to account
for many recent observations. An effective equation of state parameter that represents the cosmic fluid of the universe is postulated to predict the evolution of our
flat universe which is presently expanding with an acceleration under the negative
pressure of such a dark energy. Here a model is proposed to successfully describe the
evolution of the universe after the inflationary epoch to a time when the size of the
universe would be infinite, crossing the time of its shift from the phase of deceleration
to acceleration using a simple equation of state consistent with the cosmic scenario.
Keywords Scale factor · Equation of state · Flat universe · Dark energy
1 Introduction
The development of GTR and cosmology is a major scientific success of the twentieth
century. One of the solutions of Einstein’s field equations is the Friedmann model,
also called standard model in cosmology, which is based on cosmological principle.
Recent observations suggest that ratio of energy density to critical density is one,
that is, universe is flat. But the matter density including both baryonic and dark is
only a small fraction of total density. So there is a missing energy called dark energy.
Since 1998, when observations of supernovae Type-Ia pointed accelerated cosmic
expansion, various observational measurements have established such evolutionary
change in the history of the late universe. To find the source behind the late cosmic
acceleration is certainly a major challenge for cosmologists.
The acceleration in the expansion of the universe is one of the remarkable discoveries in recent cosmological research. This acceleration requires that nearly threequarters of the energy of the universe is in a component of fluid energy density with
a negative pressure. Many dark energy models are proposed to explain this accelC. Sivakumar (B)
Department of Physics, Maharaja’s College, Kochi, Kerala, India
e-mail: thrisivc@yahoo.com
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
K. S. Sreelatha and V. Jacob (eds.), Modern Perspectives in Theoretical Physics,
https://doi.org/10.1007/978-981-15-9313-0_2
17