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In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch is believed to have lasted from 10 −36 seconds to between 10 −33 and 10 −32 seconds after the Big Bang.
8 de ene. de 2021 · The Beginning to the End of the the Universe: Inflating the cosmos. In a trillionth of a trillionth of a trillionth of a second, our universe underwent a growth spurt that shaped the structure...
- Overview
- Inflation
One of the more enduring contributions of particle physics to cosmology is the prediction of inflation by the American physicist Alan Guth and others. The basic idea is that at high energies matter is better described by fields than by classical means. The contribution of a field to the energy density (and therefore the mass density) and the pressure of the vacuum state need not have been zero in the past, even if it is today. During the time of superunification (Planck era, 10−43 second) or grand unification (GUT era, 10−35 second), the lowest-energy state for this field may have corresponded to a “false vacuum,” with a combination of mass density and negative pressure that results gravitationally in a large repulsive force. In the context of Einstein’s theory of general relativity, the false vacuum may be thought of alternatively as contributing a cosmological constant about 10100 times larger than it can possibly be today. The corresponding repulsive force causes the universe to inflate exponentially, doubling its size roughly once every 10−43 or 10−35 second. After at least 85 doublings, the temperature, which started out at 1032 or 1028 K, would have dropped to very low values near absolute zero. At low temperatures the true vacuum state may have lower energy than the false vacuum state, in an analogous fashion to how solid ice has lower energy than liquid water. The supercooling of the universe may therefore have induced a rapid phase transition from the false vacuum state to the true vacuum state, in which the cosmological constant is essentially zero. The transition would have released the energy differential (akin to the “latent heat” released by water when it freezes), which reheats the universe to high temperatures. From this temperature bath and the gravitational energy of expansion would then have emerged the particles and antiparticles of noninflationary big bang cosmologies.
Cosmic inflation serves a number of useful purposes. First, the drastic stretching during inflation flattens any initial space curvature, and so the universe after inflation will look exceedingly like an Einstein–de Sitter universe. Second, inflation so dilutes the concentration of any magnetic monopoles appearing as “topological knots” during the GUT era that their cosmological density will drop to negligibly small and acceptable values. Finally, inflation provides a mechanism for understanding the overall isotropy of the cosmic microwave background because the matter and radiation of the entire observable universe were in good thermal contact (within the cosmic event horizon) before inflation and therefore acquired the same thermodynamic characteristics. Rapid inflation carried different portions outside their individual event horizons. When inflation ended and the universe reheated and resumed normal expansion, these different portions, through the natural passage of time, reappeared on our horizon. And through the observed isotropy of the cosmic microwave background, they are inferred still to have the same temperatures. Finally, slight anisotropies in the cosmic microwave background occurred because of quantum fluctuations in the mass density. The amplitudes of these small (adiabatic) fluctuations remained independent of comoving scale during the period of inflation. Afterward they grew gravitationally by a constant factor until the recombination era. Cosmic microwave photons seen from the last scattering surface should therefore exhibit a scale-invariant spectrum of fluctuations, which is exactly what the Cosmic Background Explorer satellite observed.
One of the more enduring contributions of particle physics to cosmology is the prediction of inflation by the American physicist Alan Guth and others. The basic idea is that at high energies matter is better described by fields than by classical means. The contribution of a field to the energy density (and therefore the mass density) and the pressure of the vacuum state need not have been zero in the past, even if it is today. During the time of superunification (Planck era, 10−43 second) or grand unification (GUT era, 10−35 second), the lowest-energy state for this field may have corresponded to a “false vacuum,” with a combination of mass density and negative pressure that results gravitationally in a large repulsive force. In the context of Einstein’s theory of general relativity, the false vacuum may be thought of alternatively as contributing a cosmological constant about 10100 times larger than it can possibly be today. The corresponding repulsive force causes the universe to inflate exponentially, doubling its size roughly once every 10−43 or 10−35 second. After at least 85 doublings, the temperature, which started out at 1032 or 1028 K, would have dropped to very low values near absolute zero. At low temperatures the true vacuum state may have lower energy than the false vacuum state, in an analogous fashion to how solid ice has lower energy than liquid water. The supercooling of the universe may therefore have induced a rapid phase transition from the false vacuum state to the true vacuum state, in which the cosmological constant is essentially zero. The transition would have released the energy differential (akin to the “latent heat” released by water when it freezes), which reheats the universe to high temperatures. From this temperature bath and the gravitational energy of expansion would then have emerged the particles and antiparticles of noninflationary big bang cosmologies.
Cosmic inflation serves a number of useful purposes. First, the drastic stretching during inflation flattens any initial space curvature, and so the universe after inflation will look exceedingly like an Einstein–de Sitter universe. Second, inflation so dilutes the concentration of any magnetic monopoles appearing as “topological knots” during the GUT era that their cosmological density will drop to negligibly small and acceptable values. Finally, inflation provides a mechanism for understanding the overall isotropy of the cosmic microwave background because the matter and radiation of the entire observable universe were in good thermal contact (within the cosmic event horizon) before inflation and therefore acquired the same thermodynamic characteristics. Rapid inflation carried different portions outside their individual event horizons. When inflation ended and the universe reheated and resumed normal expansion, these different portions, through the natural passage of time, reappeared on our horizon. And through the observed isotropy of the cosmic microwave background, they are inferred still to have the same temperatures. Finally, slight anisotropies in the cosmic microwave background occurred because of quantum fluctuations in the mass density. The amplitudes of these small (adiabatic) fluctuations remained independent of comoving scale during the period of inflation. Afterward they grew gravitationally by a constant factor until the recombination era. Cosmic microwave photons seen from the last scattering surface should therefore exhibit a scale-invariant spectrum of fluctuations, which is exactly what the Cosmic Background Explorer satellite observed.
9 de dic. de 2023 · The current cosmological paradigm for the expansion of the Universe contains many unexplained mysteries and consists of two adjoining theories: cosmic inflation (CI, Fig. 1 red curve) 1, 2,...
- Bruce M. Law
- bmlaw@phys.ksu.edu
According to the theory of inflation, the early Universe expanded exponentially fast for a fraction of a second after the Big Bang. Cosmologists introduced this idea in 1981 to solve several important problems in cosmology. One of these problems is the horizon problem.
22 de mar. de 2024 · Many cosmologists see inflation as the most plausible mechanism for the process that gave the Universe its structure. Inflation is proposed to have been caused by an energy field called the...
11 de feb. de 2005 · Abstract. Understanding the behavior of the universe at large depends critically on insights about the smallest units of matter and their fundamental interactions. Inflationary cosmology is a highly successful framework for exploring these interconnections between particle physics and gravitation.
