how fast was inflation of the universe

The horizon problem is the problem of determining why the Universe appears statistically homogeneous and isotropic in accordance with the cosmological principle. "[7], A recurrent criticism of inflation is that the invoked inflaton field does not correspond to any known physical field, and that its potential energy curve seems to be an ad hoc contrivance to accommodate almost any data obtainable. The simplest inflation models, those without fine-tuning, predict a tensor to scalar ratio near 0.1. Thus fluctuations in the former inflaton would not affect inflation termination, while fluctuations in the latter would not affect the rate of expansion. As dark energy causes the universe to expand ever-faster, it may spur some very distant galaxies to apparently move faster than the speed of light. In eternal inflation, regions with inflation have an exponentially growing volume, while regions that are not inflating don't. The following is the current "theory" of the very early universe. [123] Brane inflation suggests that inflation arises from the motion of D-branes[124] in the compactified geometry, usually towards a stack of anti-D-branes. [14] Yet as a local observer sees such a region for the first time, it looks no different from any other region of space the local observer has already seen: its background radiation is at nearly the same temperature as the background radiation of other regions, and its space-time curvature is evolving lock-step with the others. s It transcends normal political/economic discussions of inflation. The modern explanation for the metric expansion of space was proposed by physicist Alan Guth in 1979, while investigating the problem of why no magnetic monopoles are seen today. Tyson, Neil deGrasse and Donald Goldsmith (2004). Could these two photons exchange any information from the time when they are released? [56] In 1981 Einhorn and Sato[57] published a model similar to Guth's and showed that it would resolve the puzzle of the magnetic monopole abundance in Grand Unified Theories. Inflation is typically not an exactly exponential expansion, but rather quasi- or near-exponential. Cosmologists introduced this idea in 1981 to solve several important problems in cosmology. The team announced the tensor-to-scalar power ratio Inflation also dilutes exotic heavy particles, such as the magnetic monopoles predicted by many extensions to the Standard Model of particle physics. [53] In October 1980, Demosthenes Kazanas suggested that exponential expansion could eliminate the particle horizon and perhaps solve the horizon problem,[54][55] while Sato suggested that an exponential expansion could eliminate domain walls (another kind of exotic relic). It is now understood that the universe is expanding, carrying the galaxies with it, and causing this observation. Inflation predicts that the structures visible in the Universe today formed through the gravitational collapse of perturbations that were formed as quantum mechanical fluctuations in the inflationary epoch. The expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. Other models explain some of the observations explained by inflation. Different measurements of the Hubble constant, the rate of space-time expansion, refuse to … was between 0.15 and 0.27 (rejecting the null hypothesis; Like Guth, they concluded that such a model not only required fine tuning of the cosmological constant, but also would likely lead to a much too granular universe, i.e., to large density variations resulting from bubble wall collisions. In a big bang with only the matter and radiation known in the Standard Model, two widely separated regions of the observable universe cannot have equilibrated because they move apart from each other faster than the speed of light and thus have never come into causal contact. Things are constantly moving beyond the cosmological horizon, which is a fixed distance away, and everything becomes homogeneous. Inflation resolves several problems in Big Bang cosmology that were discovered in the 1970s. Starobinsky used the action, in the Einstein frame. [23], Inflation is a period of supercooled expansion, when the temperature drops by a factor of 100,000 or so. These problems arise from the observation that to look like it does today, the Universe would have to have started from very finely tuned, or "special" initial conditions at the Big Bang. He calls 'bad inflation' a period of accelerated expansion whose outcome conflicts with observations, and 'good inflation' one compatible with them: "Not only is bad inflation more likely than good inflation, but no inflation is more likely than either [...] Roger Penrose considered all the possible configurations of the inflaton and gravitational fields. [95] However, in his model the inflaton field necessarily takes values larger than one Planck unit: for this reason, these are often called large field models and the competing new inflation models are called small field models. [17] Another effect remarked upon since the first cosmic microwave background satellite, the Cosmic Background Explorer is that the amplitude of the quadrupole moment of the CMB is unexpectedly low and the other low multipoles appear to be preferentially aligned with the ecliptic plane. The new regions that come into view during the normal expansion phase are exactly the same regions that were pushed out of the horizon during inflation, and so they are at nearly the same temperature and curvature, because they come from the same originally small patch of space. Some have claimed that this is a signature of non-Gaussianity and thus contradicts the simplest models of inflation. r Penrose's shocking conclusion, though, was that obtaining a flat universe without inflation is much more likely than with inflation – by a factor of 10 to the googol (10 to the 100) power! One of the most severe challenges for inflation arises from the need for fine tuning. [citation needed] In the Soviet Union, this and other considerations led Belinski and Khalatnikov to analyze the chaotic BKL singularity in General Relativity. Now imagine a photon was released very early in the Universe and travelled freely until it hits the North Pole of t… String theory requires that, in addition to the three observable spatial dimensions, additional dimensions exist that are curled up or compactified (see also Kaluza–Klein theory). Technically, neither space nor objects in space move. Some physicists believe this paradox can be resolved by weighting observers by their pre-inflationary volume. The inflationary epoch lasted from 10−36 seconds after the conjectured Big Bang singularity to some time between 10−33 and 10−32 seconds after the singularity. [70] This analysis shows that the Universe is flat to within 0.5 percent, and that it is homogeneous and isotropic to one part in 100,000. In this situation, the predictions of effective field theory are thought to be invalid, as renormalization should cause large corrections that could prevent inflation. These regions in which the inflaton fluctuates upwards expand much faster than regions in which the inflaton has a lower potential energy, and tend to dominate in terms of physical volume. Inflation increased he size of the universe so much that the resulting universe looks flat from any point of view Extra dimensions appear as a frequent component of supergravity models and other approaches to quantum gravity. The most popular explanation for the horizon problem is the theory of inflation, which says the universe expanded at an incredible rate in its first fraction of a second. This requirement is generally thought to be satisfied if the Universe expanded by a factor of at least 1026 during inflation. Inflation is hypothesized to have occurred somewhat later, when the universe was between perhaps 10 –35 and 10 –33 second old and the temperature was 10 27 to 10 28 K. This rapid expansion took place when three forces (electromagnetic, strong, and weak) are thought to have been unified, and this is when GUTs are applicable. These fluctuations form the primordial seeds for all structure created in the later universe. This means that inflation acts as a microscope, which magnifies what was written on the initial balloon. [37], The magnetic monopole problem, sometimes called the exotic-relics problem, says that if the early universe were very hot, a large number of very heavy[why? : New Theory on the Universe's Birth", "Gravity causes homogeneity of the universe", "An interpretation of cosmological model with variable light velocity", "Cosmological model with variable light velocity: the interpretation of red shifts", "Gauge cosmological model with variable light velocity. All models of eternal inflation produce an infinite, hypothetical multiverse, typically a fractal. Current work on this model centers on whether it can succeed in stabilizing the size of the compactified dimensions and produce the correct spectrum of primordial density perturbations. One is the amplitude of the spectrum and the spectral index, which measures the slight deviation from scale invariance predicted by inflation (perfect scale invariance corresponds to the idealized de Sitter universe). Unless the rate of decay to the non-inflating phase is sufficiently fast, new inflating regions are produced more rapidly than non-inflating regions. As such, although predictions of inflation have been consistent with the results of observational tests, many open questions remain. [34][35] It became known in the 1960s that the density of matter in the Universe was comparable to the critical density necessary for a flat universe (that is, a universe whose large scale geometry is the usual Euclidean geometry, rather than a non-Euclidean hyperbolic or spherical geometry). WMAP Bolsters Case for Cosmic Inflation, March 2006,, Articles with dead external links from December 2018, Articles with permanently dead external links, Articles with dead external links from January 2018, Articles with dead external links from June 2020, Wikipedia indefinitely semi-protected pages, Short description is different from Wikidata, Wikipedia articles needing clarification from November 2012, Articles with unsourced statements from May 2014, Wikipedia articles needing clarification from June 2014, Articles needing additional references from November 2016, All articles needing additional references, Creative Commons Attribution-ShareAlike License, This page was last edited on 28 November 2020, at 12:12. Let's suppose that before inflating the balloon, I write a message on the surface of the balloon which is so tiny that you cannot read it. [...] BICEP did a wonderful service by bringing all the Inflation-ists out of their shell, and giving them a black eye. For example, the density of ordinary "cold" matter (dust) goes down as the inverse of the volume: when linear dimensions double, the energy density goes down by a factor of eight; the radiation energy density goes down even more rapidly as the Universe expands since the wavelength of each photon is stretched (redshifted), in addition to the photons being dispersed by the expansion. [121][122] When the second (slow-rolling) inflaton reaches the bottom of its potential, it changes the location of the minimum of the first inflaton's potential, which leads to a fast roll of the inflaton down its potential, leading to termination of inflation. [115] Other authors have argued that, since inflation is eternal, the probability doesn't matter as long as it is not precisely zero: once it starts, inflation perpetuates itself and quickly dominates the Universe. [65] The fluctuations were calculated by four groups working separately over the course of the workshop: Stephen Hawking;[66] Starobinsky;[67] Guth and So-Young Pi;[68] and Bardeen, Steinhardt and Turner.[69]. When inflation ends the temperature returns to the pre-inflationary temperature; this is called reheating or thermalization because the large potential energy of the inflaton field decays into particles and fills the Universe with Standard Model particles, including electromagnetic radiation, starting the radiation dominated phase of the Universe. [72][75] In March 2014, the BICEP2 team announced B-mode CMB polarization confirming inflation had been demonstrated. These photons could not have communicated with each other unless inflation took place during the very early Universe. A person at any point on the balloon might consider themselves to be at the centre of the expansion, as all neighbouring points are getting further away. The whole thing was over in less than a trillionth of a trillionth of a second, but the universe grew exponentially in that brief blip, repeatedly doubling in size. This results in the observables: According to the theory of inflation, the early Universe expanded exponentially fast for a fraction of a second after the Big Bang. In such models, most of the volume of the Universe is continuously inflating at any given time. As things stand, there is no evidence of any 'slowing down' of the expansion, but this is not surprising as each cycle is expected to last on the order of a trillion years.

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