Inflation (cosmology)

As cosmological inflation is an episode of extremely rapid expansion of the universe is called, which is believed to have taken place immediately after the Big Bang.

Shortly after the Big Bang according to the current model in the inflation phase gravitational waves, which immortalized the cosmic background radiation a characteristic polarization pattern what you found preliminary evidence in March 2014.

Description

Depending on the underlying assumptions they began between 10-43 s, ie the Planck time, and thus the beginning of the Big Bang itself, and 10-35 s and lasted until a time between 10-33 and 10-30 s s after the Big Bang.

It is assumed that the universe has expanded in this period by at least a factor of 1026. Then, the universe has continued to grow under the standard Big Bang model, as described by the Friedmann equations.

The hypothesis of this inflationary expansion was proposed in 1981 by Alan H. Guth and is not an element of the original Big Bang model. The occasion was the finding that the relativistic cosmology to explain some fundamental observations ( see below) to fine-tune ( " fine tuning" ) of cosmological parameters requires, which in turn needs to be clarified. The inflation hypothesis provides a physical mechanism from which some basic properties of the universe arise casually.

After the cause of this expansion is the change of state of a scalar field with an extremely flat potential. This Inflatonfeld called scalar field has an equation of state with negative pressure. According to the general theory of relativity, this leads to a repulsive force and thus to an expansion of the universe. The change in state of the field during the inflationary phase is similar to a phase transition first order. As part of the grand unified theory, the conditions under which the phase transition occurs, as determined by the Higgs fields.

The adoption of such an inflationary expansion appears randomly on the one hand, on the other hand, it elegantly solves several major cosmological problems:

• The visible universe today contains similar structures everywhere basically. On the other hand, it consists of areas that until very late together could causally interact with a standard expansion, since they have a direct first removed from each other after the Big Bang faster than light. The fact that we still observed a high degree of homogeneity and isotropy of the universe, the cosmic background radiation is therefore called the horizon problem and can not be explained within the framework of a standard expansion. In existence of an inflationary expansion, however, all regions of the visible universe today would have been temporarily stood before this inflation in interaction.

• The range of the visible universe today has no measurable curvature of space. As part of a standard expansion an extremely precise tuning of matter density and kinetic energy would have been required to immediately after the Big Bang, for which there is no explanation. In the case of an inflationary expansion, however, the observed flatness of the space would be merely a consequence of its immense extent, as the visible universe today would represent only a tiny part.

• The inflation hypothesis also explains the density fluctuations from which galaxies and clusters have emerged as a result of quantum fluctuations of Inflatonfeldes. The extreme expansion enlarged these fluctuations according to macroscopic size, which is a standard expansion would not have been sufficiently able to afford.

• According to some theories should be created in the Big Bang also magnetic monopoles, which, however, have eluded experimental proof until now. During an inflationary expansion of the number density of these monopolies would, however, so decreased that the probability of finding single in the visible universe today, would be extremely low - in keeping with the experimental data available.

Field dynamics

To explain the dynamics of inflation is a scalar quantum field is required which is spatially homogeneous and has a finite energy density. If the field changes slowly enough in time ( namely, in the direction of reducing the energy density), so it has negative pressure and behaves effectively as a cosmological constant, thus leading to an accelerated expansion of the universe. The expansion is exponential, when the energy density of the quantum field is the dominant component in the universe. Currently, no specific candidate for this quantum field is known. The name for a quantum field, which causes inflationary expansion, is Inflatonfeld with the Inflaton as Vermittlerteilchen.

The lowest energy state of the Inflatonfeldes can be different from zero, but it does not. This depends on the predetermined density as a parameter of the potential energy of the field. Prior to the expansion cycle the Inflatonfeld was in a higher energy state. Random quantum fluctuations triggered a phase transition, the Inflaton gave its potential energy in the form of matter and radiation, as it moved to the lower energy state. This process produced a repulsive force that accelerated the expansion of the universe.

A simple model for a Inflatonfeld is by the potential

Optionally, wherein the temperature dependence is due to the interaction with the thermal fluctuations of the remaining particles, and fields in the universe state. At high temperature, this potential has in a single minimum. If the temperature decreases due to the expansion of the universe at a first critical temperature, a second local minimum of the potential function appears at. First, has the potential at this secondary minimum a higher value than the global minimum, in which there is a field. But if the temperature falls below a second critical value, the minimum potential in the secondary has a value lower than the primary minimum. Is defined as the global minimum of the potential function, as the true vacuum, and the local minimum as the wrong vacuum.

To go from the wrong in the energetically preferred true vacuum, the field must overcome an energy barrier or tunnel through ( this is due to quantum mechanical tunneling possible). Since the energy density of the false vacuum does not change even with an expansion of space, provided the quantum mechanical tunneling process is sufficiently slowly, the pressure of the false vacuum must be negative and operates according to the Friedmann equations to exponential expansion.

Creation out of nothing?

The theory of the inflationary universe is a theory that takes into account also events before the Big Bang. The gigantic expansion of the entire universe could theoretically from a vanishingly small mass (<10 kg) have been formed with very small extent; However, this requires because of the false vacuum state of extremely high density. This thesis, however, is highly speculative, but gives a possible explanation, taking into account today's laws of physics, even if the theory of the false vacuum state is not understood until today.

Further theories dealing with the origin out of nowhere, under the terms of the vacuum fluctuations ( Tryon ) or the quantum mechanical tunneling ( Vilenkin ) have become known.

View

The hypothesis of an inflationary expansion is an area of ​​research are discussed at the numerous variants. In particular, the nature of the particles or fields that might have caused the necessary vacuum state, still completely unknown.

Whether there was indeed an inflationary phase in the early days of the universe, must be decided by observations; this is the subject of current research. Current observations about the temperature fluctuations in the cosmic background radiation by the U.S. space probe WMAP compatible with the inflation hypothesis, but still allow a final judgment.

The current accelerated expansion of the universe to which is particularly inferred from observations of distant supernovae is attributed to the presence of dark energy with negative pressure and thus to a physical mechanism that is related to the actual inflation in the early universe. However, it is still controversial whether the available data can actually be interpreted as an accelerated expansion.

Despite the complexity of this theory is widely accepted among scientists from all over the world because it offers a first logically comprehensible hypothesis.

First results

Published on March 17, 2014 U.S. scientists at the Harvard - Smithsonian Center for Astrophysics results, after which they observed at the Amundsen -Scott South Pole Station with the BICEP2 telescope to measure the cosmic microwave background radiation for the first time a signal to the intensive generation of gravitational waves suggesting in the inflation phase shortly after the Big Bang some 14 billion years ago.

Quote

" According to inflation theory, the more than one hundred billion galaxies that shine like diamonds in the heavenly universe, nothing but quantum mechanics, which was written in large letters on the sky. For me, this realization is one of the greatest wonders of the modern scientific age. "